Volume I. System Study Report
CONSULTANCY SERVICES FOR PACKAGE 1-FEASIBILITY STUDY
FOR THE 220kV INTERCONNECTION NAMIALO – METORO
ELECTRICIDADE DE MOÇAMBIQUE
Financed by Royal Norwegian Embassy
September 2016
ELECTRICIDADE DE MOÇAMBIQUE
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TABLE OF CONTENTS
1.
Introduction
1.1 Overview of Northern Area---------------------------------------------------------1
1.2 Objective of Namialo-Metro Transmission System Study--------------------2
1.3 Power Demand Forecast and Power Development Plan
2.
Northern Power System Plan in the Future(2016~2036)
2.1 Power Demand------------------------------------------------------------------------3
2.2 Power Generation Plan
2.3 Transmission System Plan
3.
Power System Study
3.1 Transmission Planning Criteria
3.1.1
Minimum Reliability Criteria
3.1.2
Voltage Levels
3.1.3
Maximum Equipment Load Levels
3.1.4
Steady State Transfer Limits
3.1.5
Transient and Dynamic Stability
3.2 Approach Method
3.2.1
Build Scenario Based Namialo-Metoro Transmission Line Planning
3.2.2
Power System Analysis
3.2.2.1 Check Power system status for every 5 years from 2016 to 2036
3.2.2.2 Load Flow Analysis
3.2.2.3 Transfer Capability Analysis based on Voltage Stability
3.2.2.4 Short Circuit Analysis
3.2.3
Determine Optimal Plan Scenario
3.2.4
Simulation cases
3.2.4.1 220kV Namialo-Metoro Transmission line construction
3.2.4.2 400kV Namialo-Metoro Transmission line construction (220kV operation)
3.2.4.3
3.2.5
400kV Namialo-Metoro Transmission line construction (400kV operation)
Contingencies
Inception Report
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3.3 Load Flow Analysis
3.3.1
Present Northern Power System (2016)
3.3.2
Scenario 0 : No Additional Transmission Line
3.3.3
Scenario A : 220kV T/L construction 220kV operation
3.3.4
Scenario B : 400kV T/L construction, 220kV operation
3.3.5
Scenario C : 400kV T/L construction, 400kV operation
3.3.6
summary
3.4 Transfer Capacity Analysis based on Voltage Stability
3.4.1
Present Northern Power System (2016)
3.4.2
Scenario 0 : No Additional Transmission Line
3.4.3
Scenario A : 220kV T/L construction 220kV operation
3.4.4
Scenario B : 400kV T/L construction, 220kV operation
3.4.5
Scenario C : 400kV T/L construction, 400kV operation
3.4.6
summary
3.5 Short Circuit Analysis
3.5.1
present system status in 2016 year
3.5.2
Scenario A : 220kV T/L construction 220kV operation
3.5.3
Scenario B : 400kV T/L construction, 220kV operation
3.5.4
Scenario C : 400kV T/L construction, 400kV operation
3.5.5
summary
3.6 Discussion
3.6.1
Technical Analysis Results
3.6.1.1 Power flow
3.6.1.1.1
System losses
3.6.1.1.2
Must-Run Generation
3.6.1.2
Short Circuit Study Results
3.6.1.3 Transfer Capability
3.6.2
Benefit of the Interconnection with Tanzania Power System
3.6.3
Feasible Solution for Namialo-Metoro transmission upgrade
4.
Conclusion
Inception Report
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1.
Introduction
Mozambique is a large country with abundant natural resources. Therefore, it has a high growth potential, and a
proper development of the power system infrastructure will significantly aid the growth of the country.
However, even though Mozambique is filled with natural resources, it is suffering from a qualitative and
quantitative deficiency in electric power, which is hindering the national growth and the well-being of the
citizens of Mozambique. This is due to the concentration of loads and generators in different areas, and the
capital cost of transmission line construction to connect the source and sink is very expensive.
The power system of Mozambique has been operated and expanded independently with four different areas,
which are Northern (ATNO), Mid-Northern (ATCN), Central (ATCE), and Southern (ATSU), shown in Figure
1.1.1.
The transmission losses are 24%, 23%, 19%, and 23% for Southern, Central, Mid-Northern, and Northern areas,
respectively. In addition, especially higher loss rates are shown in Northern areas due to the long transmission
system. Specifically, from the Statistical Summary document of 2012, the loss rate in the transmission network
is (13%) higher than the loss rate in the distribution network (11%).
Figure 1.1.1 Power system of Mozambique
4
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The average level of reliability in Mozambique is 46.27 outages/year (in 2012) based on the System Average
Interruption Frequency Index (SAIFI), and the Northern system has the highest outage level of 82.6 outages/year.
In addition, the average System Average Interruption Duration Index (SAIDI) of Mozambique is 33hours and 46
minutes (based on 2012), and the Northern area displayed the highest interruption time with 71hours and
17minutes. In reality, these levelscan be translated into one or two outages every week, causing a significant
negative impact to the economy, hindering their development to an advanced level of industry.
In order to address these issues, there have been a steady effort to joint operate the power system networks to
procure the economics and security of the power system. In addition, the utility of Mozambique, EDM, is
working very hard to install additional transmission network, generation, etc., through international cooperation
projects.
Furthermore, the new cities in the Northern system, Nacala, Pemba, etc., is displaying much faster increase in
the load growth rate, compared to other cities in Mozambique, due to natural gas and coal export industry
development in the area.
Therefore, in order to better the power transfer capability of the Northern area, projects, such as 400kV
transmission network construction between Caia and Namialo, static variable compensator (SVC) installation
along the transmission line, and expansion of generators are well under development.
In this project, the goal is to provide a technical analysis for constructing a new transmission line between
Namialo and Metoro in order to account for the significant increase in the loads in the Northern area (Pemba,
Macomia, Ausse, etc). In order to suggest the best transmission construction and operation solution, long term
load forecast (from 2016 to 2036) and analysis of generation and transmission expansion plan is conducted.
5
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A.
Overview of Northern Area
1.1.1 Power System Configuration
The power system of Northern Mozambique is shown in Figure 1.1.2.
Figure 1.1.2 Grid configuration of Northern Mozambique
The Northern transmission system is composed with 1500km network connecting the source in the East to the
loads in the West. Specifically, the main power sources are located 1300~1500km west of the loads, and the
main loads are located near the cities in the coast of Sea of Indonesia. The main transmission lines (T/Ls)
connecting the generators and loads are 220kV (main) and 110kV (sub). As a result, the system’s power transfer
capability has reached its stability limit, and the active transmission capability (ATC) of the transmission
network has been significantly reduced compared to the thermal ratings of transmission lines. In order to address
the stability problem, static variable compensators and other equipments are installed and operated.
Recently, in order to improve the transfer capability of the system, 400kV T/L is constructed between Caia and
Nampula, which will better the stability aspect of the power system.
However, due to the long length of transmission lines, lack of alternative transmission routes in case of line
faults, and the possibility of system wide collapse if major generator is tripped, the Northern system still has
much areas of improvement.
Table 1.1.1 Power supply Indices of Northern area of Mozambique
Area
System Average Interruption
Frequency Index(SAIFI)
6
System Average Interruption
Duration Index(SAIDI)
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Northern System of
64.75 times/year. Per customer
905 min/year..per customer
Mozambique (2014)
Mozambique
57 times/year. Per customer
621 min/year per customer
Nationalwide(2011)
The reliability indices of Northern Mozambique power system is shown in Table 1.1.1
1.1.2 Electric Load Demand
The load demand of the Northern area is 150MW in 2011, however, due to a high annual average growth rate of
14% of the coastal cities, Nacala and Pemba, the load is forecasted to reach 783MW in 2026 (JICA Report
2013).
Table 1.1.2 load Forecasted data of Northern Power System((JICA Report 2013)
Low Load Forecast by
Demand (MW)
Energy Consumption (GWh)
Customer Service Area
Custome
Regio Provinc
201 201 202 202 203 AA 201 201 202 202 203 AA
r Service
n
e
1
6
1
6
1
G
1
6
1
6
1
G
Area
105
Tete
AD Tete
29
177
98
105 153 9% 124
474 509 758 10%
2
Cente
AD
9
23
25
28
38
7%
39
112 121 132 188 9%
r
Mocuba
Zambez
DDC
AD
ia
Quelima
16
43
47
52
74
8%
94
210 234 265 360 7%
ne
ASC
106
48
74
122 138 188 7% 255 409 698 770
8%
Nampula
3
Nampul
ASC
124 213 218 457
22
206 350 359 727 21% 112
22%
Nacala
8
8
4
5
North
Cabo
DDN
ASC
Delgad
17
51
70
77
117 11% 87
238 322 357 534 10%
Pemba
o
AD
Niassa
9
14
18
24
32
7%
40
55
70
91
117 6%
Lichinga
From Table 1.1.2, Nacala and Pemba show a high load growth rate of 22% and 11%, respectively.
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800
700
AD Tete
600
AD Mocuba
500
AD Quelimane
400
ASC Nampula
300
ASC Nacala
200
ASC Pemba
100
AD Lichinga
0
2011
2016
2021
2026
2031
Figure 1.1.3 load growth of northern province[MW] (2011~2031)
1.1.3 Load characteristics
The daily load curve of a peak load day in Mozambique is shown in Figure 1.1.4. The peak load is observed
between 8~9p.m, and the peak usually occurs in November or December. In addition, in 2014, the peak load was
observed in December 15th, at 831MW, and the average load is 606 MW.
Figure 1.1.4. Load Profile of Peak day EDM (ref: Annual Statistical Report 2014, EDM)
Figure 1.1.5 shows the load characteristics of mid, Northern, and Tete area. It is very similar to the load profile
of entire system, where the peak load is 265MW.
8
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Figure 1.1.5. Load profile of Northern Mozambique Peak day EDM(ref : Annual Statistical Report 2014,
EDM)
B.
Objective of Namialo-Metoro Transmission System Study
The objective of Namialo-Metoro T/L feasibility study is to determine the most economic and the most reliable
transmissionnetwork considering the steep increase of load levels in the Northern area.
The objectives can be summarized as follows:
1.
Power system security assessment based on the transmission characteristics and transmission system
expansion plan of the Northern Mozambique Area.
2.
Transfer capability and loss assessment (from 2016 to 2036) of the Namialo-Metoro T/L construction
and operation scenario, and developing the optimal installation plan. Three different construction and
operation cases are considered:
A.
220kV T/L construction, 220kV operation
B.
400kV T/L construction, 220kV operation
C.
400kV T/L construction, 400kV operation
9
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2. Power Demand Forecast and Power Development Plan
The demand, generation, and transmission line data were taken from EDM’s Master Plan Update Project 1, 2,
and 3. The long term forecast data in this document bears high level of uncertainty, since Master Plan Update
data is based on short term planning. Especially, the construction and integration of generators and transmission
lines can be delayed for several years depending on various reasons, possibly affecting the load growth level.
Therefore, the result of this study may have small margin of error.
2.1 Power Demand Forecast
Demand forecast of Northern System was based on the long term load forecast of Master plan[2]. The load of
Metoro substation in 2016 is estimated as 32.7MW, however, shall be 118MW in 2036.
For a systematical analysis of the Northern transmission system, all of the loads connected to other substations
were almost forecasted using the annual load growth rate, and the forecasted values of major substations are
shown in Table 2.1.
Furthermore, in order to account for the forecast error, ±10% of the forecasted value was calculated as low and
high forecast values.
Table 2.3.1. Power demand forecast of Northern system (2016~2036)
AAG
Substation
Area
District
2016
0.06
SE Cuamba
AD
3.3
Lichinga
0.06
SE Lichinga
AD
7.8
0.06
SE Marrupa
AD
4.3
0.22
SE Monapo
AD
94.2
Nacala
0.22
SE Nacala
AD
115.7
Northern
0.08
SE Moma
AD
34.5
Nampula
0.08
SE Nampula
AD
53.1
0.1
SE Auasse
AD
53.1
0.1
SE Macomia
AD
2.1
Pemba
0.1
SE Metoro
AD
11.4
0.1
SE Pemba
AD
35.3
0.09 SE Alto Molocu AD
1.5
0.09
SE Gurue
AD
8.8
Mocuba
0.09
SE Mocuba
AD
4.9
0.09
SE Uape
AD
8.6
H Transmission 0.07
SE Cerami
AD
24.1
Queliman
0.07
SE Chimu
AD
25.8
0.1
SE Manje
AD
4.5
0.1
SE Matambo
AD
Tete
167.6
0.1
SE Tete
AD
27.2
Total
641.2
Where AAG denotes the annual average load growth rate.
10
2021
4.5
10.3
6.4
157.1
199.2
68.3
71.5
71.5
2.8
12.8
54.6
2
10
6.4
8.8
39.2
27
6
81.6
38.3
813.8
2026
6
13.4
9.8
160.8
208.1
69.3
91
91
3.7
14.6
61.3
2.6
19.5
8.4
9.1
45.8
28.5
7.8
71.6
50.1
889
2031
9
18
11
166
220
68
116
116
5
18
67.6
3
14
11
9
47
30.495
8.58
78.76
55.11
966.545
2036
9.6
19.4
12.2
192.7
245.5
74.5
123
123
5.8
21
78.9
3.1
15.3
12.9
10
49.4
32.62965
9.438
86.636
60.621
1075.325
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2.2 Power Generation Plan
The generation expansion plan of the Mozambique system is shown in Table 2.2.
Table 2.2.1. Power Generation Plan
Plan
Type
Plant Name
year
Capacity[MW]
CahoraBassa
Cahora Bassa
North
in
2018
2075
1245
Boroma
2017
200
Contents
Increase
New
Connection and Transmission
Line
Matambo 64.9km
Cataxa 58.7km
400kV(4 tern), 70% Series
compensation
Matambo 220/33kV Tr.
Songo-Matambo T branch
MaphandaNukawa
2018
375MW×4
1500
400kV line(4 Tern), 50% Series
compensation
Hydro
CAIA km
Lupata
2018
600
Matambo 78km(on Map)
10~15km North of Gurue, 110kV
Alto Malema
Lurio
2019
50
T/L(71611-71612)
- Transformer 100MVA
Metro ,
2017
180
120MW,2009
71711-71712, 110/33kV
Macomia S/S connection
Messalo
50
50km-EdM message
Ncondezi
2017
400
200MWx2
-No data in USAID
Benga
2017
2000
150MW×2
Matambo, 28km, 2cct
300MWx2(2012 present)
Thermal
300MW×2
Moatize
2016
2400
180MW×2
600MWx3(Future)
Matambo-Moatize T/L : 220kV
2cct 46.5km
ENI
2017
75
75MW×1
JICA2011 report
Nacala
2020
200
100MW×2
JICA2011 report
2.3 Transmission System Plan
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In this section, the transmission expansion of the Northern Mozambique transmission system is discussed.
2.3.1 Transmission System Length trend (total of Central-Northern and Northern, by 2014.
C-km)
Table 2.4.1. Annual transmission line growth
Voltage
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
220kV
1436 1436 1436 1436 1436 1436 1436 1436 1436 1437 1436 1436 1436 1436
110kV
total
275
275
275
375
985
985 1155 1335 1335 1335 1467 1555 1555 1555
1711 1711 1711 1811 2421 2421 2591 2771 2771 2772 2903 2991 2991 2991
2.3.2 Transmission System Plans
The transmission system expansion plan of the Northern Mozambique system is shown in Table 2.4.
Table 2.3.2.Tansmission system expansion plan of northern system
Commissioning
Project name
Capacity[MVA]
Year
220kV line - Caia-Nampula
2015
Series compensation of the
existing line
1) SVC in Nampula substation
2016
From
To
Length[km]
Caia
Nampula
486
77
Cuamba
Marrupa
215
4) 110kV line Metoro-Pemba
77
Metoro
Pemba
74
5) 220kV line Namialo-Metoro
239
6) 400kV line ChimuaraNamialo
1300
Namialo
Caia
Mocuba
A.Molocue
Metoro
Mocuba
A.Molocue
Namialo
179
218
151
268
7)400/220kV Transformer
500
220kV STATCOM SVC
100/-50
400kV Sh. Reactor
60
400kV Sh. Reactor
60
Alto
Molocue
Line shunt
400/220kV Transfromer
250
400kV Sh. Reactor
60
400kV Sh. Reactor
60x2
Alto
Molocue
Line shunt
400/220 Transformer
500
400/110 Transformer
125
220kV STATCOM SVC
100/-50
400kV Sh. Reactor
60
400kV Sh. Reactor
60
2) 110kV line Cuamba-Marrupa
3) New Marrupa Substation
2016
2016
2016
12
Chimuara S/S
Alto Molocue
400/220/110kV
Namialo S/S
Line shunt
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2016
220kV twin tern line
480
Nampula
Namialo
90.5
2016
220kV twin tern line
480
Nampula
Evete
41.2
2016
220kV twin tern line
480
2020
220/110kV Transformer
125
Evete
NacalaVelha
220kV
NacalaVelha S/S
220kV SVC(under
construction)
2017
61
220kV Nampula
1) 220kV line Nampula-Nacala
Nampula
Namialo
Evate
Nampula
480
2018
110kV line Nampula-Moma
Source : Master Plan Update Project, 2012-2027
77
Namialo
Evate
Nacala
Moma
91
41
61
170
2.3.3 Reactive Power compensation
The system tools utilized in the Northern Mozambique system for reactive power compensation is discussed in
this section.
2.3.3.1 Existing reactive compensation
Existing reactive compensators are listed in Table 2.5.
Table 2.3.3.Present reactive compensation devices
No.
Substation
Unom[kV]
Installed MVAr
No. Items
stats
Sh. Cap.
1
Alto-Molocue
7.7
30
1
on
2
Lionde
33
8
1
on
3
Matambo
33
10
1
on
4
Chicumbane
33
8
1
Out of service
Sh.Reactor
1
Alto-Molocue
7.7
50
1
on
2
Caia
220
20
1
on
3
Caia
33
15
1
on
4
Chibata
33
15
1
on
5
Lichinga
110
15
1
on
6
Matambo
33
5
1
on
7
Mocuba
33
65
1
on
8
Nampula220
33
20
1
on
9
Pemba
110
35
1
on
10
Quelimane
33
5
1
on
11
Songo
33
20
1
on
13
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Single Reactance
1
Macomia
110
50
1
on
Source : “Technical Assistance to Strengthen EDM’s Capacity for Investment and Network Development
Planning”, Master Plan Update Project, 2012 – 2027, Volume 1 Final System Review Report, 2013-04-15
2.3.3.2 Reactive compensation Plans
The planned installation of reactive power compensators are shown in Table 2.3.4.
Table 2.3.4.Plan of reactive compensator installation
No.
Substation
Unom[kV]
Installed MVAr
No. Items
stats
Sh. Cap.
1
Alto-Molocue
7.7
30
1
on
2
Lionde
33
8
1
on
3
Matambo
33
10
1
on
4
Chicumbane
33
8
1
Out of service
Sh.Reactor
1
Alto-Molocue
7.7
50
1
on
2
Caia
220
20
1
on
3
Caia
33
15
1
on
4
Chibata
33
15
1
on
5
Lichinga
110
15
1
on
6
Matambo
33
5
1
on
7
Mocuba
33
65
1
on
8
Nampula220
33
20
1
on
9
Pemba
110
35
1
on
10
Quelimane
33
5
1
on
11
Songo
33
20
1
on
1
on
Single Reactance
1
Macomia
110
50
14
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3.3 Power Flow Analysis
In this section, the results of power flow analysis is provided in order to analyze the operational state of
Northern Mozambique power system, using forecasted demand and generation values from section 2.
In order to supply power at Metoro, Pemba, Macomia, and Mocimbua substations through Namialo-Metoro
transmission line, four different Namialo-Metoro cases were analyzed.
1.
No additional T/L construction
2.
220kV T/L construction
3.
400kV T/L construction, 220kV operation
4.
400kV T/L construction, 400kV operation
Furthermore, the generators were dispatched considering the cost of generation for each generator. In cases
where power flow analysis results diverged, must-run generators were operated in order to make the system
operable.
From the results, the system’s service standard, security, and reliability was analyzed for the steady state
operation using bus voltages, phase angles, and power flows. Also, system power losses on transmission lines
have been calculated for each case for economic evaluation.
Also, the validity of this analysis may be questioned if the integration of Northern power system components
does not follow the schedule. Hence, in order to analyze the sensitivity of the system to the planned integration
of power sources, it was assumed that some generators are not online by its commissioning year (Lurio Hydro
plant was assumed to be out of service), and additional analysis has been performed.
Table 3.3.1 shows different cases which were considered for power flow analysis. The analysis was performed
for the normal load level, and 1.1 times the normal load level. For Lurio outage case, normal load levels were
used.
Table 3.3.1 Power flow analysis cases
Year
2016
SC0-2016
Scenario 0
100%
SCA-2016
Generators
Scenario A
100, 110%
commissioned
as planned
SCB-2016
Scenario B
100, 110%
Scenario C SCC-2016
2018
SC0-2018
100%
SCA-2018
100, 110%
SCB-2018
100, 110%
SCC-2018
15
2021
SC0-2021
100%
SCA-2021
100, 110%
SCB-2021
100, 110%
SCC-2021
2026
SC0-2026
100%
SCA-2026
100, 110%
SCB-2026
100, 110%
SCC-2026
2031
SC0-2031
100%
SCA-2031
100, 110%
SCB-2031
100, 110%
SCC-2031
2036
SC0-2036
100%
SCA-2036
100, 110%
SCB-2036
100, 110%
SCC-2036
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Scenario 0
Lurio power
plant out in
service
Scenario A
Scenario B
Scenario C
100, 110%
SC0-2016
100%
SCA-2016
100%
SCB-2016
100%
SCC-2016
100%
100, 110%
SC0-2018
100%
SCA-2018
100%
SCB-2018
100%
SCC-2018
100%
100, 110%
SC0-2021
100%
SCA-2021
100%
SCB-2021
100%
SCC-2021
100%
100, 110%
SC0-2026
100%
SCA-2026
100%
SCB-2026
100%
SCC-2026
100%
100, 110%
SC0-2031
100%
SCA-2031
100%
SCB-2031
100%
SCC-2031
100%
100, 110%
SC0-2036
100%
SCA-2036
100%
SCB-2036
100%
SCC-2036
100%
3.3.1Present Status of Northern Power System (2016)
The modeling of Norther Mozambique power system is shown in Figure 3.3.1. At present, the main power
supply to the grid comes from Cahora Bassa hydro plant (415MWx5=2075MW) and Moatize thermal plant
(300x2=600MW). Although the total capacity is 2675MW, half (1300MW) is used to supply power to South
Africa due to an agreement with Escom, leaving only 1375MW available.
In 2016, Caia-Namialo 400kV HVAC backbone was commissioned, and is in parallel operation with 220kV
transmission system, transporting half (263MW) of total supplied power (574MW) from the West. Therefore,
the system is partly able to withstand few N-1 contingencies, compared to year 2015.
Figure 3.3.1 Northern Power System of Mozambique
However, since the power supplied to Namialo substation comes from 1300km away through many different
system components, the maximum phase angle becomes -96 degrees (Pemba), which may cause instability in
case of contingencies. The peak power received at Metoro substation in 2016 is 33+j16.3MVA, come from
110kV Namialo-Metoro T/L (215km). The sending end power is 37.0-j14.6MVA, and the loss is 4-j30.9MVA
(10.8%). Also, the loss rate of Northern area was 15.8% due to a long rage power transmission.
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Figure 3.3.6Load, Generation, Length of T/L (2016)
Figure 3.3.7Bus Voltages and Phase Angles (2016)
3.3.2 Scenario 0: Not Constructing new T/L (SC0)
In this section, the operational state of Northern power system is analyzed assuming that no additional
transmission line will be constructed. Also, the transfer capability of 110kV T/L for different load levels is
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analyzed.
Figure 3.3.8Namialo-Metoro system diagram for Scenario 0
3.3.2.1 System Analysis (SC0-100%)
The system state after 2018 was analyzed assuming that no additional transmission line was constructed to meet
the increasing load levels.
Table 3.3.2. Analyzed years in Scenario 0
SC0-2018
SC0-2021
SC0-2026
Scenario 0
100%
100%
100%
3.3.2.1.1 Analysis Results in 2018(SC0-2018, 100%)
18
SC0-2031
100%
SC0-2036
100%
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(a)Load and generation level and T/L length
(b) Bus Voltages and Phase Angles
Figure 3.3.3No T/L Construction (SC0 2018 100%)
3.3.2.1.2 Analysis Results in 2021(SC0-2021, 100%)
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(a) Load and Generation Level and T/L Length
(b) Bus Voltages and Phase Angles
Figure 3.3.6No T/L Construction (SC0 2021 100%)
If no additional T/L is constructed, the 110kV Namialo-Metoro T/L is able to supply 78MW of power to the
loads after Metoro substation, and the phase angles of Namialo 110kV bus and Metoro 110kV bus become -82
and -137 degrees, respectively, with a phase angle difference of 67 degrees between two buses.
3.3.2.1.3 Analysis Results in 2026 (SC0 2026 100%)
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(a) Load and Generation Level and T/L Length
(b) Bus Voltages and Phase Angles
Figure 3.3.7No T/L Construction (SC0 2026 100%)
3.3.2.1.4 Analysis Results in 2031 (SC0 2031 100%)
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(a) Load and Generation Level, and T/L Length
(b) Bus Voltages and Phase Angles
Figure 3.3.8No T/L Construction (SC0 2031 100%)
3.3.2.1.5 Analysis Results in 2036(SC0 2036 100%)
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(a) Load and Generation Levels, and T/L Length
(b) Bus Voltages and Phase Angles
Figure 3.3.9No T/L Construction (SC0 2036, 100%)
3.3.2.2Overview of Analysis Results (SC0, 100%)
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In this section, the bus voltages, phase angles, power flows, and losses were calculated assuming that no
additional T/L will be constructed. As a result, the T/L reaches its thermal limit in 2019, followed by worse
voltage and phase angle values. Therefore, the power transfer limit of the T/L has been reached in 2019.
1,1
METORO 110
1,05
SC0
1
MOCIMBUA
0,95
110 SC0
METRO 2 220
0,9
220 SC0
0,85
METRO 4 SC0
0,8
2018 2021 2026 2031 2036
Figure 3.3.10Bus Voltages of Major Buses if No Additional T/L is Constructed
0
METORO 110
2018 2021 2026 2031 2036
SC0
MOCIMBUA
-50
110 SC0
NAMIALO 110
-100
SC0
NAMIALO 220
SC0
-150
Figure 3.3.11Phase Angles of Major Buses if No Additional T/L is Constructed
Table 3.3.2 Namialo-MetoroT/LLoading (SC0)
2018
2019
2020
2021
2022
2023
2024
110loading[MVA]
59
76.7
89.8
120.6
125.3
114.1
114
110kVrating[MVA]
77
77
77
77
77
77
77
110kV[%]
76.6
99.6
116.7
156.7
162.7
148.2
148
2025
2026
2027
2028
2029
2030
2031
110loading[MVA]
100.9
103.6
100.5
109.5
100.2
104.1
79.6
110kVrating[MVA]
77
77
77
77
77
77
77
110kV[%]
131
134.5
130.5
142.2
130.1
135.3
103.4
2032
2033
2034
2035
2036
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110loading[MVA]
84.1
100.6
56
55
27.8
110kVrating[MVA]
77
77
77
77
77
110kV[%]
109.2
130.7
72.7
71.4
36.1
Table 3.3.3System andNamialo-MetoroT/L Losses (SC0, 100%)
Total Loss[MW]
Loss rate[%]
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
188.1
216.9
275.2
291.1
257.5
298
367.1
290.8
258.6
355.7
349.5
17.88
18.90
21.62
21.47
19.14
21.15
24.45
20.08
17.97
22.87
22.28
Namialo-Metoro
110kVLoss[MW]
9.71
16.53
22.9
41.86
45.09
37.53
37.28
29.15
30.99
28.87
34.39
2029
2030
2031
2032
2033
2034
2035
2036
SUM
Total Loss[MW]
242.4
344.6
244.2
342.3
352.5
251.7
283.6
258.6
5468.4
16.37
21.51
16.06
20.79
20.93
15.63
16.98
15.46
28.77
31.11
17.85
20.13
28.92
8.94
8.51
2.06
Loss rate[%]
Namialo-Metoro
110kVLoss[MW]
480.59
Table 3.3.4Transformers and T/Ls Exceeding 100% Capacity(SC0, 100%)
2021
2026
2031
2036
Scenario0
Rating
[MVA]
SERIES M to MOCUBA
SERIES M to A-MOLOCU
SERIES A to A-MOLOCU
SERIES A to NAMPULA
T-OFF2 to CAIA
QUELIM.C to QUELIM.L
SONGO A to PST
NAMPULA3 to NAMPULA1
NAMPULA1 to NAMPULA
NAMPUL.D to NAMPULA
NAMPUL.D to NAMPULA
NAMPUL.D to NAMPULA
A-MOLOCU to A_MOLOCU
NAMPULA to NAMP.CEN
NAMP.CEN to NAMP.CEN
MONAPO to NAMIALO
MOMA to MOMA22
GURUE to GURUE
METORO to METORO 3
METORO to NAMIALO
PEMBA to PEMBA
LICHINGA to LICHINGA
NAMIALO to NAMIALO
NCONDEZI to NCONDEZI
239
239
239
239
477
12
600
16
100
100
100
16
55
99
35
84
25
16
10
77
16
16
125
185
Loading
[MVA]
281.2
281.2
303.2
303.2
Overrate
[%]
118%
118%
127%
127%
Loading
[MVA]
267.9
267.9
269.9
269.9
Overrate
[%]
112%
112%
113%
113%
Loading
[MVA]
262.8
262.8
263.4
263.4
Overrate
[%]
110%
110%
110%
110%
37.5
1619.4
29.1
313%
270%
182%
45
1620
27.3
103.6
104.3
103.6
375%
270%
171%
104%
104%
104%
55
1624.7
27.8
107.3
107
107.3
458%
271%
174%
107%
107%
107%
151.4
105.8
39.2
128.5
36.8
275%
107%
112%
153%
147%
115.7
49.1
124.3
36.9
117%
140%
148%
148%
134.7
65.6
121.3
36.1
136%
187%
144%
144%
120.6
157%
103.6
135%
79.6
17
19.8
188.2
103%
106%
124%
151%
188.3
151%
186.6
149%
Table 3.3.5 Buses with Abnormal Voltage Levels(SC0,100%)
2021
2026
2031
Scenario0 BaseV
V[kV]
[kV]
MARRUPA
NAMPULA3
NAMP.CEN
CHIMUARA
QUELIMAN
QUELIM.C
QUELIM.R
QUELIM.L
STAR BUS
SERIES M
MARROMEU
110
33
33
33
220
33
33
33
1
220
110
V[PU]
V[kV]
V[PU]
39.835
1.207
38.53
1.168
28.663
0.869
29.691
29.346
0.900
0.889
29.674
29.353
0.899
0.889
0.889
194.44
98.033
0.889
0.884
0.891
0.8895
197.33
0.890
0.897
25
V[kV]
121.39
38.908
29.53
29.086
29.613
0.8814
197.9
Loading
[MVA]
281
281
286.4
286.4
487.1
58.5
1622.7
115.1
124.3
147
124.3
115.1
Overrate
[%]
118%
118%
120%
120%
102%
488%
270%
719%
124%
147%
124%
719%
148.9
71.6
153.9
40
16.2
15
150%
205%
183%
160%
101%
150%
20.1
21.6
166.9
191.8
126%
135%
134%
104%
2036
V[PU]
V[kV]
V[PU]
1.104
1.179
0.895
0.881
0.897
0.881
0.900
28.2
0.855
197.82
28.953
28.487
29.042
0.8632
193.68
0.899
0.877
0.863
0.880
0.863
0.880
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MARROMEU
LICHINGA
LICHINGA
MOCIUMBA
MOCIUMBA
METORO
METORO3
LURIOG1
MACOMIA
33
110
33
110
33
110
33
33
33
29.537
0.895
96.548
28.122
98.577
29.573
29.573
29.578
0.878
0.852
0.896
0.896
0.896
0.896
97.226
26.432
0.884
0.801
28.8
0.873
3.3.3ScenarioA :220kV T/L Construction & 220kV Operation(SCA)
In this scenario, power system operating status of Northern area is analyzed considering the construction of
220kV Namialo-Metoro T/L. Annual increase of loads following Metoro substation has been taken into account.
Figure 3.3.12System Diagram Considering 220kV Namialo-Metoro T/L Construction
3.3.3.1 System Analysis (SCA-100%)
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The operating status of the system considering the construction of 220kV Namialo-Metoro T/L, in
2018, is analyzed.
Scenario A
SCA-2016 SCA-2018 SCA-2021 SCA-2026 SCA-2031
100, 110% 100, 110% 100, 110% 100, 110% 100, 110%
3.3.3.1.1 Analysis Results for 2018 (SCA-2018, 100%)
(a) Load and Generation Levels and T/L Length
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(b) Bus Voltages and Phase Angles
Figure 3.3.13Analysis Results Considering 220kV T/L Construction & 220kV Operation(SCA 2018 100%)
3.3.3.1.2 Analysis Results for 2021 (SCA-2021, 100%)
(a) Load and Generation Levels and T/L Length
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(b) Bus Voltages and Phase Angles
Figure 3.3.14220kV T/L Construction & 220kV Operation(SCA 2021 100%)
If 220kV T/L is constructed, 110kV and 220kV Namialo-Metoro T/L is capable of sending 78MW to
Metoro substation, and the phase angles of Namialo and Metoro 110kV bus are -75 and -72.9 degrees,
respectively. As a result, the phase angle difference between two buses have been significantly
reduced due to operation of must run generation at Lurio.
3.3.3.1.3 Analysis Results for 2026 (SCA-2026, 100%)
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(a) Load and Generation Level and T/L Length
(b) Bus Voltages and Phase Angles
Figure 3.3.15220kV T/L Construction & 220kV Operation(SCA 2026 100%)
3.3.3.1.4 Analysis Results for 2031 (SCA-2031, 100%)
(a) Load and Generation Levels and T/L Length
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(b) Bus Voltages and Phase Angles
Figure 3.3.16220kV T/L Construction & 220kV Operation(SCA 2031 100%)
3.3.3.1.5 Analysis Results for 2036 (SCA-2036, 100%)
(a) Load and Generation Level and T/L Length
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(b) Bus Voltages and Phase Angles
Figure 3.3.17220kV T/L Construction & 220kV Operation(SCA 2036, 100%)
3.3.3.2Overview of Analysis Results (SCA, 100%)
In this section, bus voltages, phase angles, power flows, and losses of major buses has been analyzed
considering the construction and operation of 220kV T/L. The results show that although the line flows do not
reach the limit, after 2026, line flow is maintained at 30% of line capacity, and the bus voltages and phase angles
becomes worse due to long range power transmission. Furthermore, the voltage level at Metoro substation is
higher compared to other buses, which is due to the Ferranti effect.
1,1
METORO 110
1,05
SCA
NAMIALO 110
1
SCA
0,95
NAMIALO 220
SCA
0,9
MOCIUMBA 110
SCA
0,85
2018 2021 2026 2031 2036
Figure 3.3.18Voltages of Major Buses Considering 220kV T/L Construction & 220kV Operation
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2018 2021 2026 2031 2036
METORO 110
-20
SCA
NAMIALO 110
-40
SCA
-60
NAMIALO 220
-80
MOCIUMBA 110
SCA
SCA
-100
Figure 3.3.19Phase Angles of Major Buses Considering 220kV T/L Construction &220kV Operation
Table 3.3.6 Namialo-MetoroT/L Loading Levels (SCA, 100%)
2018
2019
2020
2021
110loading[MVA]
14.4
9.5
8.2
7.7
110kVrating[MVA]
77
77
77
77
110kV%
18.7%
12.3%
10.6%
10.0%
220kVloading[MVA]
28.6
43.1
48
57
220kVrating[MVA]
239
239
239
239
220kV%
12.0%
18.0%
20.1%
23.8%
2025
2026
2027
2028
110loading[MVA]
6.4
9.6
5.4
5.3
110kVrating[MVA]
77
77
77
77
110kV%
8.3%
12.5%
7.0%
6.9%
220kVloading[MVA]
57.6
75.4
59.9
63.2
220kVrating[MVA]
239
239
239
239
220kV%
24.1%
31.5%
25.1%
26.4%
2032
2033
2034
2035
110loading[MVA]
7.3
5.3
6.7
4.4
110kVrating[MVA]
77
77
77
77
110kV%
9.5%
6.9%
8.7%
5.7%
220kVloading[MVA]
74.5
71
75.5
77.1
220kVrating[MVA]
239
239
239
239
220kV%
31.2%
29.7%
31.6%
32.3%
2022
6.9
77
9.0%
51.8
239
21.7%
2029
5.6
77
7.3%
65.8
239
27.5%
2036
7.2
77
9.4%
84.5
239
35.4%
2023
6.8
77
8.8%
55.9
239
23.4%
2030
5.6
77
7.3%
67.5
239
28.2%
2024
8.4
77
10.9%
62
239
25.9%
2031
4.9
77
6.4%
67.8
239
28.4%
Table 3.3.7System &Namialo-MetoroT/L Losses (SCA, 100%)
Total Loss[MW]
Loss rate[%]
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
140.1
155.7
187.3
229.8
236.4
243.6
257
269.7
304.6
276.9
295.6
17.85
17.98
18.47
18.90
20.51
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
13.95
0.42
0.18
14.33
0.13
15.81
0.1
17.75
0.08
0.08
0.1
0.05
0.1
0.03
0.03
0.05
0.3
0.46
0.77
0.63
0.76
0.98
0.84
1.63
0.97
1.12
2029
2030
2031
2032
2033
2034
2035
2036
SUM
Total Loss[MW]
303.3
296.6
246
256.1
219.1
234.2
251.5
270.5
33
4674
18.75
19.52
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Loss rate[%]
19.68
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
14.13
14.70
15.35
16.06
0.02
0.02
19.09
0.01
16.16
0.04
16.42
0.01
0.02
0
0.03
1.12
1.33
1.37
1.69
1.58
1.82
1.92
2.33
1.45
21.79
Table 3.3.8 System &Namialo-MetoroT/L Losses (SCA, 110%)
2018
Total Loss[MW]
Loss rate[%]
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
2019
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
2022
2023
2024
2025
2026
SERIES M to
MOCUBA
SERIES M to
A-MOLOCU
SERIES A to
A-MOLOCU
SERIES A to
NAMPULA
T-OFF2 to
CAIA
QUELIM.C to
QUELIM.L
SONGO A to
PST
NAMPULA3to
NAMPULA1
MATAMBO to
TETE
MATAMBO to
CAIA
A-MOLOCUto
A_MOLOCU
NAMPULA to
NAMP.CEN
NAMP.CEN to
NAMP.CEN
MONAPO to
MONAPO
MONAPO to
NAMIALO
MOMA to
MOMA22
CAIA to CAIA
4
METORO to
METORO 3
PEMBA to
PEMBA
LICHINGA to
2028
217.5
279.1
278.6
233.2
245.9
261.4
268.4
296
295.1
14.96
16.13
16.51
19.21
18.85
16.00
16.43
17.01
17.10
18.31
18.01
0.52
0.16
0.13
0.1
0.09
0.06
0.06
0.08
0.05
0.05
0.01
1.51
1.45
1.45
0.48
0.69
2030
1.17
2031
2032
1.14
1.07
1.21
1.37
2033
2034
2035
2036
SUM
309.8
304
221.7
253.6
257.1
274.8
270.5
287.3
4919
18.50
17.99
13.78
15.00
14.91
15.51
15.04
15.57
0
0.18
0.42
0.28
0.42
0.59
1.01
1.21
5.42
1.62
0.73
0.26
0.7
0.42
0.34
0.13
0.11
15.97
Table 3.3.9 T/Ls & Transformers Exceeding 100% Capacity(SCA,100%)
2016
2021
2026
2031
ScenarioA
Rating
[MVA]
2027
197.4
0.12
Loss rate[%]
2021
167.6
2029
Total Loss[MW]
2020
Loading
[MVA]
Overrate
[%]
2036
Loading
[MVA]
Overrate
[%]
Loading
[MVA]
Overrate
[%]
Loading
[MVA]
Overrate
[%]
Loading
[MVA]
Overrate
[%]
239
264.8
111%
331.2
139%
276.4
116%
294.2
123%
239
264.8
111%
331.2
139%
276.4
116%
294.2
123%
239
291.8
122%
316.7
133%
295.3
124%
302.1
126%
239
291.8
122%
316.7
133%
295.3
124%
302.1
126%
540.3
113%
500.3
105%
477
12
27.8
232%
37
308%
47.3
394%
55.5
463%
57.5
479%
600
1607.9
268%
1620.7
270%
1616.7
269%
1622.9
270%
1618.3
270%
29.1
182%
27.9
174%
28
175%
27.3
171%
63.7
106%
16
60
477
55
99.2
180%
99
36
39.2
109%
479.4
101%
261.3
475%
96.4
175%
139.9
254%
114
115%
136.3
138%
142.6
144%
49
136%
65.5
182%
66.2
184%
30.9
103%
30
84
143.1
170%
148.4
177%
137.3
163%
154
183%
25
36.8
147%
36.9
148%
36.1
144%
40.7
163%
275.8
110%
256.3
103%
27.7
277%
250
10
27.7
277%
28.1
281%
28.1
281%
16
17
106%
19.8
124%
16
20.1
126%
20.3
127%
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LICHINGA
NAMIALO to
NAMIALO
NCONDEZI to
NCONDEZI
MOATIZE to
MOATIZE
100
105.3
105%
109.8
110%
185
263.9
143%
198.4
107%
185
254.2
118.6
119%
132.3
132%
185.3
100%
137%
Table 3.3.10 Buses with Voltage Level Violation (SCA,100%)
ScenarioA
NAMPULA
NAMPULA
NAMPULA3
A-MOLOCU
CHIMUARA
QUELIMAN
QUELIM.C
QUELIM.R
QUELIM.L
CAIA
CAIA
STAR BUS
SERIES M
SERIES C
MARROMEU
MARROMEU
NICUADAL
MONAPO
LICHINGA
BaseV
[kV]
110
33
33
7.7
33
220
33
33
33
220
110
1
220
220
110
33
220
33
33
2016
V[kV]
123.19
2021
V[PU]
V[kV]
2026
V[PU]
V[kV]
2031
V[PU]
V[kV]
2036
V[PU]
V[kV]
V[PU]
1.120
36.852
39.82
1.117
1.207
29.065
0.881
36.325
39.011
8.57
27.204
191.5
28.199
27.865
28.27
197.18
95.959
0.844
184.04
191.73
92.849
27.793
192.34
29.068
28.877
1.101
1.182
1.113
0.824
0.870
0.855
0.844
0.857
0.896
0.872
0.844
0.837
0.872
0.844
0.842
0.874
0.881
0.875
36.325
39.011
8.57
27.204
191.5
28.199
27.865
28.27
197.18
95.959
0.844
184.04
191.73
92.849
27.793
192.34
29.068
28.877
1.101
1.182
1.113
0.824
0.870
0.855
0.844
0.857
0.896
0.872
0.844
0.837
0.872
0.844
0.842
0.874
0.881
0.875
38.529
1.168
27.894
195.49
28.772
28.483
28.857
0.845
0.889
0.872
0.863
0.874
98.245
0.863
190.98
196.59
95.047
28.505
196.44
29.457
29.163
0.893
0.863
0.868
0.894
0.864
0.864
0.893
0.893
0.884
3.3.4 ScenarioB :400kV T/L Construction & 220kV Operation(SCB)
In this section, the steady state operation of 400kV Namialo-Metoro T/L operating on 220kV is
analyzed, considering annual growth of loads connected to Metoro substation.
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Figure 3.3.20System Diagram Considering 400kV T/L Construction& 220kV Operation
3.3.4.1 System Analysis (SCB-100%)
In this section, the system status is analyzed for different years after 2018, considering the
construction of 400kV T/L, and operating it on 220kV.
Scenario B
SCB-2016 SCB-2018 SCB-2021 SCB-2026 SCB-2031
100, 110% 100, 110% 100, 110% 100, 110% 100, 110%
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3.3.4.1.1 Analysis Results for 2018(SCB-2018, 100%)
(a) Load and Generation Level and T/L Length
(b) Bus Voltages and Phase Angles
Figure 3.3.21400kV T/L Construction and 220kV Operation(SCB 2018 100%)
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3.3.4.1.2 Analysis Results for 2021(SCB-2021, 100%)
(a) Load and Generation Levels and T/L Lengths
(b) Bus Voltages and Phase Angles
Figure 3.3.22400kV T/L Construction & 220kV Operation (SCB 2021 100%)
If 400kV T/L is constructed and operated on 220kV, 110kV and 220kV Namialo-Metoro T/L is able to
supply 78MW to loads following Metoro substation, and the phase angles of 110kV buses at
Namialo and Metoro substation becomes -74.5 and -71.2, respectively. The phase angles of two
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buses are slightly improved compared to Scenario A, however, not by much.
3.3.4.1.3 Analysis Results for 2026(SCB-2026, 100%)
(a) Load and Generation Levels and T/L Lengths
(b) Bus Voltages and Phase Angles
Figure 3.3.23400kV T/L Construction & 220kV Operation (SCB 2026 100%)
3.3.4.1.4 Analysis Results for 2031(SCB-2031, 100%)
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(a) Load and Generation Levels and T/L Lengths
(b) Bus Voltages and Phase Angles
Figure 3.3.24400kV T/L Construction & 220kV Operation (SCB 2031 100%)
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3.3.4.1.5 Analysis Results for 2036 (SCB-2036, 100%)
(a) Load and Generation Levels and T/L Lengths
(b) Bus Voltages and Phase Angles
Figure 3.3.25400kV T/L Construction & 220kV Operation(SCB 2036 100%)
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3.3.4.2 Overview of Analysis Results (SCB, 100%)
In this section, the voltages, phase angles, power flow, and losses of major buses for different years
have been analyzed considering 400kV T/L construction and 220kV operation. The results show
improved line flows compared to Scenario 0 and A, and that the voltages and phase angles of major
buses become worse as year progresses, due to long range transmission. Again, high voltage level at
Metoro substation is caused by Ferranti effect.
1,1
METORO 110 SCB
1,05
NAMIALO 110 SCB
1
NAMIALO 220 SCB
0,95
MOCIUMBA 110
SCB
0,9
2018
2021
2026
2031
2036
Figure 3.3.26 Voltages of Major Buses Considering 400kV T/L Construction & 220kV Operation
0
2018
2021
2026
2031
2036
-20
METORO 110 SCB
-40
NAMIALO 110 SCB
NAMIALO 220 SCB
-60
MOCIUMBA 110
-80
SCB
-100
Figure 3.3.27 Phase Angles of Major Buses Considering 400kV T/L Construction & 220kV Operation
Table 3.3.11 Namialo-MetoroT/L Loading (SCB, 100%)
2018
2019
2020
2021
42
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2023
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110loading[MVA]
110kVrating[MVA]
110kV%
220kVloading[MVA]
220kVrating[MVA]
220kV%
110loading[MVA]
110kVrating[MVA]
110kV%
220kVloading[MVA]
220kVrating[MVA]
220kV%
110loading[MVA]
110kVrating[MVA]
110kV%
220kVloading[MVA]
220kVrating[MVA]
220kV%
16
77
20.8%
37
715
5.2%
2025
9.5
77
12.3%
65.9
715
9.2%
2032
7.2
77
9.4%
81.5
715
11.4%
11
77
14.3%
52.9
715
7.4%
2026
10.1
77
13.1%
80.9
715
11.3%
2033
6.7
77
8.7%
78.4
715
11.0%
10.3
77
13.4%
57.4
715
8.0%
2027
8.8
77
11.4%
68
715
9.5%
2034
7.1
77
9.2%
83.4
715
11.7%
9.4
77
12.2%
65.6
715
9.2%
2028
8.2
77
10.6%
71.8
715
10.0%
2035
7.1
77
9.2%
84.9
715
11.9%
9.6
77
12.5%
59.7
715
8.3%
2029
7.8
77
10.1%
74.5
715
10.4%
2036
6
77
7.8%
90.6
715
12.7%
9.3
77
12.1%
62.8
715
8.8%
2030
7.4
77
9.6%
76
715
10.6%
9
77
11.7%
69.9
715
9.8%
2031
7.5
77
9.7%
74.6
715
10.4%
Table 3.3.12 System and Namialo-MetoroT/L Losses (SCB, 100%)
Total Loss[MW]
Loss rate[%]
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
Total Loss[MW]
Loss rate[%]
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
135.7
155.2
186.5
228.2
235.3
242.2
254.8
268.1
288.1
275.4
293.7
13.57
17.78
17.90
18.34
18.81
19.61
0.54
0.25
14.29
0.22
15.75
0.2
17.65
0.18
0.17
0.18
0.16
0.2
0.14
0.13
0.05
0.18
0.25
0.38
0.31
0.35
0.46
0.41
0.66
0.46
0.53
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
SUM
301
294.3
242.8
250.7
217.4
232.1
249.1
263
4613.6
19.55
14.04
14.59
14.86
15.68
0.12
0.11
18.97
0.09
15.98
0.1
16.13
0.07
0.08
0.06
0.06
0.59
0.62
0.61
0.75
0.71
0.82
0.87
1
18.67
19.41
3.06
10.01
Table 3.3.13 System and Namialo-MetoroT/L Losses (SCB, 110%)
2018
Total Loss[MW]
Loss rate[%]
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
Loss rate[%]
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
2020
2021
2022
2023
2024
2025
2026
178.1
196.5
216.8
277.2
276.8
232
246.3
262.5
266.3
293.3
293.9
15.75
16.07
16.47
19.11
18.75
15.93
16.46
17.07
16.99
18.16
17.95
0.39
0.26
0.23
0.2
0.2
0.17
0.17
0.18
0.15
0.15
0.13
0.75
0.68
0.74
0.16
2029
Total Loss[MW]
2019
0.27
2030
0.37
2031
0.59
2032
0.58
0.53
0.6
0.68
2033
2034
2035
2036
SUM
4835.1
285.5
304.7
231.8
245.4
254.7
245.4
260.3
267.6
17.30
18.03
14.15
14.59
14.79
14.26
14.56
14.66
0.1
0.34
0.53
0.58
0.57
1.09
1.26
1.47
8.17
0.72
0.36
0.16
0.3
0.2
0.11
0.19
0.12
8.11
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Table 3.3.14 T/Ls and Transformers Exceeding 100% Capacity (SCB, 100%)
2021
2026
2031
ScenarioB Rating 2016
SERIES M to
MOCUBA
SERIES M to
A-MOLOCU
SERIES A to
A-MOLOCU
SERIES A to
NAMPULA
T-OFF2 to
CAIA
QUELIM.C to
QUELIM.L
SONGO A to
PST
NAMPULA3to
NAMPULA1
MATAMBO to
TETE
MATAMBO to
CAIA
A-MOLOCUto
A_MOLOCU
NAMPULA to
NAMP.CEN
NAMP.CEN to
NAMP.CEN
MONAPO to
MONAPO
MONAPO to
NAMIALO
MOMA to
MOMA22
CAIA to CAIA
4
METORO to
METORO 3
PEMBA to
PEMBA
LICHINGA to
LICHINGA
NAMIALO to
NAMIALO
NCONDEZI to
NCONDEZI
MOATIZE to
MOATIZE
2036
[MVA]
Loading
[MVA]
Overrate
[%]
Loading
[MVA]
Overrate
[%]
Loading
[MVA]
Overrate
[%]
Loading
[MVA]
Overrate
[%]
Loading
[MVA]
Overrate
[%]
239
263
110%
317.4
133%
274.9
115%
291
122%
263
110%
239
263
110%
317.4
133%
274.9
115%
291
122%
263
110%
239
292.1
122%
312.3
131%
293.4
123%
298.1
125%
292.1
122%
239
292.1
122%
312.3
131%
293.4
123%
298.1
125%
292.1
122%
525.1
110%
494.7
104%
477
12
36.9
308%
46.6
388%
55.2
460%
56.8
473%
36.9
308%
600
1620.8
270%
1617.5
270%
1623.2
271%
1618.8
270%
1620.8
270%
16
29.4
184%
28.3
177%
28.5
178%
28.1
176%
29.4
184%
63.6
106%
86
156%
39.2
109%
60
477
55
86
156%
99
36
39.2
109%
220
400%
95.9
174%
140.9
256%
112.1
113%
134.8
136%
139.8
141%
49
136%
65.4
182%
66
183%
30.7
102%
30
84
142
169%
148.2
176%
137.2
163%
153.2
182%
142
169%
25
36.8
147%
36.8
147%
36.1
144%
40.6
162%
36.8
147%
270.2
108%
255.6
102%
27.7
277%
27.7
277%
104.1
104%
263.7
143%
250
10
27.7
277%
28
280%
28
280%
16
17
106%
19.8
124%
16
20.1
126%
20.3
127%
116.4
116%
130
130%
100
104.1
104%
107.1
107%
185
263.7
143%
196.4
106%
185
Table 3.3.15Buses with Abnormal Voltage Levels (SCB, 100%)
ScenarioB
NAMPULA
NAMPULA
NAMPULA3
A-MOLOCU
CHIMUARA
QUELIMAN
QUELIM.C
QUELIM.R
QUELIM.L
CAIA
CAIA
STAR BUS
SERIES M
SERIES C
MARROMEU
MARROMEU
BaseV
[kV]
110
33
33
7.7
33
220
33
33
33
220
110
1
220
220
110
33
2016
V[kV]
123.19
2021
V[PU]
V[kV]
2026
V[PU]
V[kV]
2031
V[PU]
V[kV]
2036
V[PU]
V[kV]
V[PU]
1.120
36.812
39.994
1.116
1.212
36.496
39.248
1.106
1.189
36.603
39.374
1.109
1.193
36.45
1.105
29.108
0.882
27.625
194.25
28.621
28.291
28.691
0.837
0.883
0.867
0.857
0.869
29.298
0.888
29.435
28.99
29.519
0.892
0.878
0.895
28.217
197.86
29.136
28.849
29.219
0.855
0.899
0.883
0.874
0.885
97.343
0.857
187.37
193.85
94.307
28.28
0.885
0.857
0.852
0.881
0.857
0.857
0.878
196.56
0.878
0.893
0.874
192.82
197.76
96.167
28.88
0.874
0.876
0.899
0.874
0.875
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NICUADAL
MONAPO
LICHINGA
220
33
33
195.08
29.311
28.877
0.887
0.888
0.875
28.151
0.853
29.34
0.889
3.3.5Scenario C:400kV T/L Construction & 400kV Operation(SCC)
In this section the steady state operation of 400kV Namialo-Metoro T/L construction and operation is
analyzed considering annual load growth levels of the loads connected to Metoro substation.
Figure 3.3.28System Diagram for 400kV T/L Construction & 400kV Operation
3.3.5.1 System Analysis (SCC-100%)
In this section, the system status considering 400kV Namialo-Metoro T/L construction and 400kV
operation is analyzed after 2018.
Scenario C
SCC-2016 SCC-2018 SCC-2021 SCC-2026 SCC-2031
100, 110% 100, 110% 100, 110% 100, 110% 100, 110%
3.3.5.1.1 Analysis Results for 2018 (SCC-2018, 100%)
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(a) Load and Generation Levels and T/L Lengths
(b) Bus Voltages and Phase Angles
Figure 3.3.29400kV T/L Construction and 400kV Operation (SCC 2018 100%)
3.3.5.1.2 Analysis Results for 2021(SCC-2021, 100%)
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(a) Load and Generation Levels and T/L Lengths
(b) Bus Voltages and Phase Angles
Figure 3.3.30400kV T/L Construction and 400kV Operation (SCC 2021 100%)
In 2021, if 400kV T/L is constructed and operated on 400kV, 110kV and 220kV Namialo-Metoro T/L is able to
supply 78MW to loads connected to Metoro substation, and the phase angles of 110kV buses at Namialo and
Metoro substations are -72.3 and -64.7, respectively, showing a significant improvement compared to Scenario
A and B.
3.3.5.1.3 Analysis Results for 2026(SCC-2026, 100%)
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(a) Load and Generation Levels and T/L Lengths
(b) Bus Voltages and Phase Angles
Figure 3.3.31400kV T/L Construction and 400kV Operation(SCC 2026 100%)
3.3.5.1.4 Analysis Results for 2031(SCC-2031, 100%)
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(a) Load and Generation Levels and T/L Lengths
(b) Bus Voltages and Phase Angles
Figure 3.3.32400kV T/L Construction and 400kV Operation(SCC 2031 100%)
3.3.5.1.5 Analysis Results for 2036(SCC-2036, 100%)
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(a) Load and Generation Levels and T/L Lengths
(b) Bus Voltages and Phase Angles
Figure 3.3.33400kV T/L Construction and 400kV Operation(SCC 2036 100%)
3.3.5.2 Overview of Analysis Results (SCC, 100%)
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The voltages, phase angles, line flows, and losses of major buses for different years have been analyzed
considering 400kV T/L construction and 400kV operation. The results show that the line flow is maintained
between 10~20% of transmission limit until 2036, and improved voltage levels and phase angles compared to
other scenarios. The voltage level at Metoro substation is higher than other substations due to Ferranti effect.
1,1
METORO 110 SCC
1,05
NAMIALO 110 SCC
1
NAMIALO 220 SCC
0,95
MOCIUMBA 110
SCC
0,9
2018
2021
2026
2031
2036
Figure 3.3.34 Voltages of Major Buses Considering 400kV T/L Construction & 400kV Operation400kV
0
2018
2021
2026
2031
2036
METORO 110 SCC
-20
NAMIALO 110 SCC
-40
NAMIALO 220 SCC
-60
MOCIUMBA 110
-80
SCC
-100
Figure 3.3.35Phase Angles of Major Buses Considering 400kV T/L Construction & 400kV Operation
Table 3.3.16 Namialo-MetoroT/L Loading (SCC, 100%)
2018
2019
2020
110loading[MVA]
19.6
18.9
19.5
110kVrating[MVA]
77
77
77
110kV%
25.5%
24.5%
25.3%
220kVloading[MVA]
119.4
129.4
135.6
220kVrating[MVA]
1300
1300
1300
220kV%
9.2%
10.0%
10.4%
2025
2026
2027
51
2021
20
77
26.0%
146.5
1300
11.3%
2028
2022
20.2
77
26.2%
136.8
1300
10.5%
2029
2023
20.2
77
26.2%
140.8
1300
10.8%
2030
2024
20.1
77
26.1%
146.1
1300
11.2%
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110loading[MVA]
110kVrating[MVA]
110kV%
220kVloading[MVA]
220kVrating[MVA]
220kV%
20
77
26.0%
151.7
1300
11.7%
2032
18.7
77
24.3%
156.8
1300
12.1%
110loading[MVA]
110kVrating[MVA]
110kV%
220kVloading[MVA]
220kVrating[MVA]
220kV%
19.9
77
25.8%
172.8
1300
13.3%
2033
18
77
23.4%
155.3
1300
11.9%
20.2
77
26.2%
154.5
1300
11.9%
2034
18.2
77
23.6%
159.4
1300
12.3%
20.2
77
26.2%
157.7
1300
12.1%
2035
19.1
77
24.8%
162.9
1300
12.5%
20
77
26.0%
159.6
1300
12.3%
2036
19
77
24.7%
166.8
1300
12.8%
19.7
77
25.6%
159.9
1300
12.3%
18.8
77
24.4%
154.3
1300
11.9%
Table 3.3.17 System &Namialo-MetoroT/L Losses (SCC, 100%)
Total Loss[MW]
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
135.2
153
182.9
221.8
229.3
235.6
246.6
259.9
278.6
268.1
284.7
Loss rate[%]
13.53
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
Total Loss[MW]
Loss rate[%]
17.41
17.50
17.85
18.34
0.92
0.84
14.11
0.9
0.96
0.97
0.97
0.97
0.98
1.01
0.98
0.98
0.09
0.14
0.18
0.25
0.21
0.23
0.26
0.3
0.46
0.33
0.36
17.24
19.09
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
SUM
291
284.9
235.1
238.4
213.4
227.1
243
254.2
4482.8
19.03
NamialoMetoro110kVLoss
[MW]
Namialo-Metoro
220kVLoss[MW]
15.49
13.81
14.32
14.91
15.24
0.97
0.94
18.47
0.84
15.55
0.84
15.77
0.78
0.81
0.86
0.86
17.38
0.38
0.39
0.35
0.37
0.37
0.41
0.44
0.48
6
2026
18.26
18.93
Table 3.3.18 System &Namialo-MetoroT/L Losses (SCC, 110%)
2018
Total Loss[MW]
Loss rate[%]
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
2019
Namialo-Metoro
110kVLoss[MW]
Namialo-Metoro
220kVLoss[MW]
2022
2023
2024
2025
193.2
212.9
269.8
268.9
227.8
239.7
253.7
259.1
283.8
283
15.55
15.84
16.22
18.69
18.32
15.68
16.09
16.59
16.61
17.67
17.40
0.96
0.95
0.98
1.1
1.07
0.98
1
1
1
0.99
0.98
0.49
0.41
0.42
0.15
Loss rate[%]
2021
175.5
2029
Total Loss[MW]
2020
0.27
2030
0.31
2031
0.47
2032
0.4
0.36
0.4
2033
2034
2035
0.43
2036
SUM
295.7
294.9
220
236.6
248.3
262.7
266.6
252
17.81
17.55
13.69
14.31
14.65
14.93
14.86
14.09
4744.2
0.98
1.32
1.37
1.33
1.54
1.73
2.04
2.72
24.04
0.46
0.32
0.17
0.24
0.2
0.2
0.18
0.14
6.02
Table 3.3.19 T/Ls and Transformers Exceeding 100% Capacity (SCC, 100%)
2021
2026
2031
ScenarioC Rating 2016
SERIES M to
MOCUBA
SERIES M to
A-MOLOCU
Loading
[MVA]
Overrate
[%]
2036
Loading
[MVA]
Overrate
[%]
Loading
[MVA]
Overrate
[%]
Loading
[MVA]
Overrate
[%]
Loading
[MVA]
Overrate
[%]
239
251.5
105%
302.3
126%
264.3
111%
278.1
116%
239
251.5
105%
302.3
126%
264.3
111%
278.1
116%
[MVA]
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SERIES A to
A-MOLOCU
SERIES A to
NAMPULA
T-OFF2 to
CAIA
QUELIM.C to
QUELIM.L
SONGO A to
PST
NAMPULA3to
NAMPULA1
MATAMBO to
TETE
MATAMBO to
CAIA
A-MOLOCUto
A_MOLOCU
NAMPULA to
NAMP.CEN
NAMP.CEN to
NAMP.CEN
MONAPO to
MONAPO
MONAPO to
NAMIALO
MOMA to
MOMA22
CAIA to CAIA
4
METORO to
METORO 3
PEMBA to
PEMBA
LICHINGA to
LICHINGA
NAMIALO to
NAMIALO
NCONDEZI to
NCONDEZI
MOATIZE to
MOATIZE
239
279.2
117%
305.8
128%
280.5
117%
286.9
120%
239
279.2
117%
305.8
128%
280.5
117%
286.9
120%
518.2
109%
488.4
102%
477
12
27.8
232%
36.6
305%
46
383%
54.4
453%
56
467%
600
1607.9
268%
1621.4
270%
1618.2
270%
1623.8
271%
1619.5
270%
29.6
185%
29.3
183%
29
181%
29.2
183%
63.5
106%
76.3
139%
16
60
477
55
133.9
243%
99
107.7
109%
130.5
132%
134.1
135%
48.9
136%
65.3
181%
65.8
183%
30.5
102%
36
39.2
109%
30
84
138.5
165%
146.8
175%
136.4
162%
151.8
181%
25
36.8
147%
36.8
147%
36.1
144%
40.6
162%
269.9
108%
255.7
102%
27.7
277%
250
10
27.7
277%
27.8
278%
27.8
278%
16
17
106%
19.8
124%
16
20.1
126%
20.3
127%
110.3
110%
124.9
125%
100
185
185
262.9
254.2
142%
101.9
102%
195.1
105%
137%
Table 3.3.20 Buses with Abnormal Voltage Levels (SCC, 100%)
ScenarioC
NAMPULA
NAMPULA
NAMPULA3
A-MOLOCU
CHIMUARA
QUELIMAN
QUELIM.C
QUELIM.R
QUELIM.L
CAIA
CAIA
STAR BUS
SERIES M
SERIES C
MARROMEU
MARROMEU
NICUADAL
MONAPO
LICHINGA
BaseV
[kV]
110
33
33
7.7
33
220
33
33
33
220
110
1
220
220
110
33
220
33
33
2016
V[kV]
123.19
2021
V[PU]
V[kV]
2026
V[PU]
V[kV]
2031
V[PU]
V[kV]
2036
V[PU]
V[kV]
V[PU]
1.120
40.14
1.216
36.752
39.913
1.114
1.209
36.384
39.736
1.103
1.204
36.328
39.903
1.101
1.209
29.373
0.890
27.977
196.64
28.986
28.659
29.055
0.848
0.894
0.878
0.868
0.880
29.657
0.899
28.604
0.867
29.403
0.891
29.555
29.27
29.637
0.896
0.887
0.898
98.499
0.868
191.35
195.5
95.522
28.686
197.45
0.895
0.868
0.870
0.889
0.868
0.869
0.898
0.891
0.891
0.887
196.62
0.887
0.894
97.506
29.326
0.886
0.889
28.877
0.875
29.426
0.892
28.275
0.857
3.3.6Overview of Power Flow Analysis Results
The analysis results for different scenarios are discussed in the aspect of system security (phase angle, T/L
loading, rating, voltage violation, and T/L and transformer exceeding capacity improvement) and economics
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(loss reduction and must-run generation operation).
3.3.6.1 System Security Improvement
1.
Phase Angle Improvement
150
Scenario0 110kV
100
ScenarioA110kV
50
ScenarioA220kV
ScenarioB110kV
0
18
21
26
31
ScenarioB220kV
36
Figure 3.3.36Absolute Value of Phase Angles for Different Scenarios at Metoro Bus
The y-axis of the graph shows the phase angle of Metoro bus for different scenarios. It is shown that the
Scenario C has the lowest value of phase angle compared to other scenarios.
2.
T/L Loading Level Improvement
200,00%
ScenarioA 110kV
150,00%
ScenarioA 220kV
100,00%
ScenarioB 110kV
ScenarioB 220kV
50,00%
ScenarioC 110kV
0,00%
ScenarioC 400kV
19 21 23 25 27 29 31 33 35
Figure 3.3.37 Namialo-Metoro T/L Loading (Scenario A, B, C, 0)
The graph above shows the loading levels of Namialo-Metoro T/L in percentages. All scenarios show that the
T/L is operated within 30% of its thermal capacity, except Scenario 0. Therefore thermal capacity is not a major
problem in this study.
3.
Reduction of Voltage Violation Buses
60
0,135
40
0,13
ScenarioA
20
ScenarioB
ScenarioC
0
ScenarioA
ScenarioB
0,125
Total number of
ScenarioC
0,12
off-limit V buses
Deviation
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Figure 3.3.38Voltage Violating Buses (Scenario A, B, C)
In Figure 3.3.38, the graph on the left shows the total number of buses that have violated the voltage range
(0.9~1.1p.u) for all the years under consideration for Scenario A, B, and C. It has been observed that Scenario C
has the smallest number of buses violating the voltage range, whereas Scenario A has the largest number of
voltage violations. The figure on the right shows the range of voltage deviation from the normal range for
various Scenarios, and it also shows that the deviation is smallest in Scenario C and largest in Scenario A.
Most voltage violations occurred in Nampula, Queliman, Marromeu, Chimura, Lichinga, Caia, Nicuadal, and
Monapo buses, and most violations occurred in 2026 (Table 3.3.10, Table 3.3.15, Table 3.3.20). Therefore,
integration of new equipment should be considered to improve voltage characteristics of the system.
4.
T/L and Transformer Overrate Reduction
95
90
ScenarioA
85
ScenarioB
80
Total number of
ScenarioC
overrate
branches
Figure 3.3.39Total Number of Overrated T/Ls and Transformers for Scenario A, B, and C
In Figure 3.3.39, the total number of T/Ls and transformers that are overrated for three scenarios are graphed for
all the years under consideration. It has been assumed that the T/L or transformer is overrated if the loading or
rating value exceeds one. From this figure, Scenario C has the lowest number of overrated T/Ls and
transformers compared to other two scenarios.
Most overrated equipment were observed in Mocuba, Alto Molocu, Nampula, Queliman, Caia, Songo, Monapo,
Moma, Metoro, Pemba, Lichinga, Namialo, Ncondezi, and Moatize (Table 3.3.9, Table 3.3.14, Table 3.3.19).
Therefore, the capacity of T/Ls and transformers should be expanded in order to meet the increasing load levels.
3.3.6.2 Economic Benefits
Transmission line loss is an important index to compare the economic benefits of different T/L construction
scenarios. When new T/L is constructed and integrated to the power network, the power flows in the network is
modified due to change in network impedance and geometry. Therefore, the economic benefit from network loss
reduction should be analyzed for the entire system.
Another notable point is the operation of must-run generators. In each scenario, as loads increase for each
following year, there comes a point where the power flow results diverge, resulting from voltage instability due
to long range transmission. This phenomenon is observed after year 2021 for Scenario 0 and after year 2026 for
scenario A and B. In order to resolve this issue, must run generations have to be operated near the load area, and
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the generators capable of providing power in the Northern system are NacalaVelha, Palma ENI, and Lurio. From
these three options, Lurio hydro plant was exempted due to long and uncertain construction period. So,
NacalaVelha and Palma ENI thermal plants were used as must-run generators.
Must run generations decrease transmission losses and increase the power supply reliability. The value of these
generations differ depending on the system operation status, however, 60~80% loss reduction and voltage
instability improvement has been observed from the simulation compared to using the power from slack bus.
Hence, when performing economic evaluation, the cost of must run generator operation should be considered
depending on whether it is providing real or reactive power to the system.
1.
Loss Reduction
25,00%
ScenarioA
20,00%
ScenarioB
15,00%
ScenarioC
Scenario0
10,00%
18 21 24 27 30 33 36
Figure 3.3.40Loss percentage for 100% load for Scenario A, B, C and 0
25,00%
20,00%
ScenarioA
ScenarioB
15,00%
ScenarioC
10,00%
18 21 24 27 30 33 36
Figure 3.3.41Loss percentage for 110% load for Scenario A, B, C, and 0
The system losses for different scenarios for 100% load case and 110% load case is shown in Figure 3.3.40 and
3.3.41, respectively. Two different load cases are analyzed for loads growing as forecasted (100%), and loads
growing more than the forecasted levels (110%). Scenario 0 is used to compare the losses of Scenario A, B, and
C.
From the figures above, Scenario C has the lowest loss ratio in both 100% and 110% load cases, followed by
Scenario B and Scenario A. Loss ratio is calculated using the equation below.
𝑃𝑙𝑜𝑠𝑠
𝑃𝐺𝑒𝑛 − 𝐻𝑉𝐷𝐶𝑜𝑢𝑡𝑝𝑢𝑡
Ploss, Pgen, and HVDCoutputdenotes total power loss, total generation, and total power send to South Africa
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using the HVDC line, respectively.
2.
Must-Run Generation
The required generation amount of must-run generators for stable system operation for difference scenarios are
shown in the figure below.
600
500
400
300
SC0_MRGen
200
SC0_loss
100
2036
2034
2032
2030
2028
2026
2024
2022
2020
2018
2016
0
Figure 3.3.42 Required must-run generation, Scenario 0
600
500
400
300
SCA_MRGen
200
SCA_loss
100
2036
2034
2032
2030
2028
2026
2024
2022
2020
2018
2016
0
Figure 3.3.43 Required must-run generation, Scenario A
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600
500
400
300
SCB_MSGen
200
SCB_loss
100
2036
2034
2032
2030
2028
2026
2024
2022
2020
2018
2016
0
Figure 3.3.44 Required must-run generation, Scenario B
600
500
400
300
SCC_MRGen
200
SCC_loss
100
2036
2034
2032
2030
2028
2026
2024
2022
2020
2018
2016
0
Figure 3.3.45 Required must-run generation, Scenario C
As shown in the figures above, Scenario 0 requires must-run generators after year 2021 to meet the loads
connected to Metoro substation. If new T/L is constructed (Scenario A,B, and C), must-run generations are
required after year 2026.
3.
Power Loss Calculation
The power losses and must-run generations are shown in the table below. Loss factor of 0.58 has been applied.
Table 3.3.21 Northern system losses and must-run generations for Scenario A, B, C, 0
Scenario 0
Scenario A
Scenario B
Scenario C
System Loss [GWh]
14604
14851
13502
11803
Must-runGeneration[GWh]
12600
7306
7544
7255
Total[GWh]
27,204
22,156
21,047
19,058
각시나리오별로 2018년도부터 2036년간Namialo-Metoro송전선로자체에발생하는선로손실의합은다음
표와같다.
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Table 3.3.22 Namialo-MetoroT/L Loss rate for Scenario A, B, C, 0
Loss on each T/L [GWh]
Scenario 0
Scenario A
Scenario B
110kV T/L
2,492
257
117
220/400kV T/L
0
88
63
Total
2,492
345
180
Scenario C
42
58
100
In Figure 3.3.46, the loss rate of Namialo-Metoro T/L for different scenarios are displayed.
0,6
0,55
0,52
0,470,49
0,43 0,46
0,41
0,40 0,40 0,390,41
0,33
0,280,30
0,27
0,4
0,2
0,19
0,15
0,11
Scenario-A
0,190,18
0.006(SCC)
0.042(SCA)
0.016(SCB)
Scenario-B
0,08 Scenario_C
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
0
Senario-0
Figure 3.3.46 Namialo-MetoroT/L Loss Rate (Scenario A, B, C, 0)
The T/L in Scenario 0 shows high loss rate after 2018, reaching 27% after 2019. Hence, loss rate is too high to
supply power to loads efficiently. On the other hand, Scenario A, B, and C shows the loss rate of 4%, 1.6%, and
0.6%, respectively.
3.3.7 Sensitivity Analysis (If Lurio hydro plant does not follow its planned operation schedule)
Earlier sections were analyzed assuming that all the generations, T/Ls, and loads are follow the integration plan
or forecast. However, in reality, equipment installation plans may be delayed or modified due to various issues
or problems. Therefore, in this section, it has been assumed that the Lurio hydro plant does not follow its
integration and operation schedule, and its effect has been analyzed.
Year
Scenario 0
Lurio
hydro
plant not
integrated
&
operated
as
planned
1.
Scenario A
Scenario B
Scenario C
2016
SC0-2016
100%
SCA2016
100%
SCB2016
100%
SCC2016
100%
2018
SC0-2018
100%
SCA2018
100%
SCB2018
100%
SCC2018
100%
2021
SC0-2021
100%
SCA2021
100%
SCB2021
100%
SCC2021
100%
Loss rate
59
2026
SC0-2026
100%
SCA2026
100%
SCB2026
100%
SCC2026
100%
2031
SC0-2031
100%
SCA2031
100%
SCB2031
100%
SCC2031
100%
2036
SC0-2036
100%
SCA2036
100%
SCB2036
100%
SCC2036
100%
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30,00%
25,00%
20,00%
Scenario-0
15,00%
Scenario-A
10,00%
Scenario-B
Scenario-C
5,00%
0,00%
18
21
24
27
30
33
36
Figure 3.3.47 Loss rate for Scenario A, B, C, 0 in Lurio off and 100% Load case
As previously shown in Figure 3.3.40, if Lurio hydro plant is integrated and operated as scheduled, all the
scenarios, except Scenario 0, do not exceed the loss rate of 20%. However, in Figure 3.3.47, all scenarios exceed
the loss rate of 20% after 2019. Also, higher loss rate has been observed for 110% load levels, and must –run
generations had to be operated after 2022.
2.
T/L loading
200,0%
SceanrioA 110kV
150,0%
SceanrioA 220kV
SceanrioB 110kV
100,0%
SceanrioB 220kV
SceanrioC 110kV
50,0%
SceanrioC 400kV
Sceanrio0 110kV
0,0%
18 20 22 24 26 28 30 32 34 36
Figure 3.3.48 Namialo-Metoro T/L Loading for Lurio off, 100% Load level (Scenario A, B, C, 0)
All scenarios, except Scenario 0, are operated between 30%~50% of T/L thermal limit.
3.
Bus Voltage Deviations
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80
0,15
60
0,145
ScenarioA
40
ScenarioB
20
ScenarioC
0
Total out-limit
Sceanrio
A
0,14
Sceanrio
0,135
B
Sceanrio
0,13
C
0,125
V bus number
Deviation
Figure 3.3.49 Bus Voltage Violations for Lurio off, 100% Load Levels (Scenario A, B, C)
The buses with voltage violations become much greater compared to the case where Lurio plant is operated as
planned (Figure 3.3.38), reducing the operational stability of the system.
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3.4 Transfer Capacity
In power systems, there are three different categories that impose limits on transfer capability, which are thermal,
voltage stability, and angle stability. The transfer capability is determined by the minimum of the three values.
The Northern transmission system connects the main power source, CHB, to Nacala and Pemba, which is about
1300km in length, and the voltage throughout this long transmission system is maintained by static variable
compensator (SVC) or capacitor bank. Therefore, it is very likely that the overall transfer capability will be
determined by either voltage or angle stability transfer limit.
In this section, transfer capability of the Namialo-Metoro T/L is determined by analyzing the thermal rating,
voltage stability, and angle stability of different operation scenarios.
Table 3.4.5. Thermal Transfer Capability of Namialo-Metoro T/L
T/L type
Operating
Thermal
Distance[km]
[kV]
Voltage [kV]
Capacity[MVA]
110
110
215
77
220
220
215
239
220
215
715
400
400
215
1300
R[pu]
X[pu]
C[pu]
0.2861
0.04002
0.01553
0.003883
0.7090
0.2268
0.1560
0.03899
0.07530
0.3422
0.4057
1.3411
As shown in Table 3.4.1, if the T/L between Namialo and Metoro is upgraded to 400kV and operated in 400kV,
there will be no problem serving the forecasted demand of 884.8MVA in 2036, calculated in previous section, if
only the thermal capacity is considered. However, as previously mentioned, since a voltage instability problem
is expected due to the long distance of T/L, the transfer capability considering voltage stability is calculated in
the following sections.
Furthermore, in order to provide adequate reliability and security for the system, N-1 reliability criterion was
considered, which are listed below.
Table 3.4.6. Considered N-1 Contingencies
C1
C2
C3
C4
N-1 Contingencies
Namialo 220/110kV Transformer Trip
110kV Namialo-Metoro T/L Trip
220kV (could be 400kV depending on the Scenario) Namialo-Metoro T/L Trip
Namialo 400/220kV Transformer Trip
3.4.1Without New T/L Construction (Base Scenario)
3.4.1.1 2016 year case
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Figure 3.4.9. PSS/E Modeling of 110kV Namialo-Metoro T/L
In order to perform the analysis, the transmission system is modeled as shown in Figure 3.4.1. The blue, green,
and red lines indicate 400, 220, and 110kV T/L, respectively. Since the 220kV T/L is not in service in 2016, the
transmission capability of 110kV Namialo-Metoro T/L is analyzed.
Since the 220kV T/L is not in service, the total thermal capacity of the T/L is 77MVA.
Figure 3.4.2. Transfer Capacity Analysis (Scenario A: 2016, N-0)
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Figure 3.4.3. Transfer Capacity Analysis (Scenario A: 2016, N-1 (C4))
Table 3.4.7. Transfer Capacity Analysis Results (Scenario A, 2016)
Power
Voltage Bus Voltage [p.u.]
Flow[MVA]
Cases Contingency
[kV]
Namialo Metoro from
to
N-0
N-1
C1
110
1.0337
1.0425
110
1.0551
1.0425
37.0j14.5
36.6j11.8
33.1+j16.2
33.1+j12.5
Loss
[MVA]
Max
Transfer
Cap[MW]
Max
Transfer
Cap[MVA]
3.9+j1.7
63.66
88
3.5+j0.7
39.04
43
The additional power that the current system can supplied to the load, and the power flow on the T/Ls
considering N-0 and N-1 contingencies are shown in Figure 3.4.2 and 3.4.3.
In the base case, the maximum real power transmission capability of 110kV T/L to the loads in Metoro area is
63.66MW, with the line flow of 88MVA. Therefore, the transmission capability of the base case is determined
by the voltage stability transfer capability of 63.66MW (88MVA).
Furthermore, the N-1 contingency considered in 2016 is the outage of 220/110kV transformer at Namialo. When
the transformer was tripped, the maximum real power transmission capability of the system was 39.04MW with
line flow of 43MVA. Therefore, the transfer capacity of the system considering N-1 contingency is determined
by the voltage stability transfer capacity of 39.04MW (43MVA).
3.4.1.2 2018 year case
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Figure 3.4.4. PSS/E Modeling of 220kV, 110kV Namialo-Metoro T/L
As shown in Figure 3.4.4, it is assumed that the 220kV Namialo-Metoro T/L will be in service by 2018, and is in
parallel operation with 110kV T/L.
The thermal capacity of each line is 77MVA and 239MVA, with a total of 316MVA.
Figure 3.4.5. Transfer Capacity Analysis (Scenario A: 2018, N-0)
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Figure 3.4.6. Transfer Capacity Analysis (Scenario A: 2018, N-1(C1))
Figure 3.4.7. Transfer Capacity Analysis (Scenario A: 2018, N-1(C4))
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The voltage stability transfer capacity of the system for N-0 and N-1 cases are shown in Figure 3.4.5, 3.4.6, and
3.4.7. Figure 3.4.5 is displaying the base case, whereas Figure 3.4.6 and 3.4.7 are showing the voltage stability
transfer capacity of the system considering C1 and C4 contingencies, respectively.
In 2018, the maximum voltage stability transfer capacity of the system in the base case is 116.83MW with line
flow of 134MVA, which is much less than the total thermal capacity of 220kV and 110kV T/Ls (316MVA).
Therefore, the transfer capacity of the system in the base case is determined by the voltage stability transfer
capacity of 116.83MW.
Furthermore, when contingencies are considered, the maximum transfer capacity of the system is much reduced,
which is summarized in Table 3.4.4.
Table 3.4.8. Transfer Capacity Analysis Results (Scenario A, 2018)
Power Flow
Bus Voltage [p.u.]
Voltage
[MVA]
Cases Contingency
[kV]
Namialo Metoro
From
To
N-0
C1
C2
N-1
C3
C4
110
1.0527
1.0397
-12.7+j3.7
220
1.0116
1.0397
-10.4-j28.1
Total
-
-
-23.1-j24.4
110
1.0726
1.0398
23.0+j12.8
220
1.0043
1.0398
1.3-j33.2
Total
-
-
-21.7-j20.4
110
1.0528
1.0360
-
220
1.0106
1.0360
-23.6-j24.1
Total
-
-
-23.6-j24.1
110
1.0394
1.0336
-22.2+j7.7
220
1.0090
1.0336
-
Total
-
-
-22.2+j7.7
110
1.0489
1.0406
-12.5+j2.9
220
1.0180
1.0407
-10.7-j25.9
Total
-
-
-23.2-j23.0
3.4.1.2 2021 year case
67
Loss
[MVA]
13.3j10.5
10.5j7.4
23.8j17.9
25.1j16.1
-1.2j2.0
23.9j18.1
0.6j6.8
0.1j35.5
0.7j42.3
2.1j3.3
0.1j35.2
2.2j38.5
-
-
23.9j10.4
23.9j10.4
23.9j11.7
23.9j11.7
13.0j9.8
10.8j10.0
23.8j19.8
0.3j34.5
0.3j34.5
1.7j4.0
1.7j4.0
0.5j6.9
0.1j35.9
0.4j42.8
Max
Transfer
Cap
[MW]
Max
Transfer
Cap[MVA]
116.83
134
108.41
128
0
-
0
-
110.01
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Figure 3.4.8. Transfer Capacity Analysis (Scenario A: 2021, N-0)
The additional real power transfer capability and according power flow in the T/Ls are shown in Figure 3.4.8, in
the base case. The 2021 system is able to supply additional load of 12.13MW, and the total line flow at this point
is 58.06MW (97.5MVA). Therefore, transfer capacity of the T/L is determined by voltage stability transfer
capability of 58.06MW, instead of the thermal rating of the T/Ls (316MVA).
The maximumpower transfer capability of the system considering the base and N-1 contingency is shown in
Table 3.4.3.In 2021, the system is unable to provide power to the in the case of C1, C3, and C4 contingencies.
Table 3.4.9. Transfer Capacity Analysis Results (Scenario A, 2021)
Power Flow
Bus Voltage [p.u.]
Voltage
[MVA]
Cases Contingency
[kV]
Namialo Metoro From
To
N-0
Max
Transfer
Cap
[MW]
Max
Transfer
Cap[MVA]
30.7+j15.2
24.5+j12.2
0.1j8.0
0.8j32.0
0.9j40.0
58.06
97.5
110
1.0350
220
1.0001
Total
-
110
1.0197
1.0590
-
-
-
220
0.9924
1.0590
25.2j49.4
24.5+j17.3
0.7j32.1
C1
N-1
-6.1j5.0
31.51.0590
j47.2
25.4j52.2
Diverge
1.0590
Loss
[MVA]
C2
68
6.2-j3.0
0
28.5
-
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Total
C3
C4
-
-
25.2j49.4
Diverge
Diverge
24.5+j17.3
0.7j32.1
0
0
3.4.1.3 2026 year case
The transfer capability of parallel operation of 110 and 220kV Namialo-Metoro T/L is analyzed. Same system
diagram is used, with forecasted load level at 2026.
Figure 3.4.9. Transfer Capacity Analysis (Scenario A: 2026, N-0)
In the base case, maximum voltage stability transfer capability of the system is 46.71MW, with the line flow of
91MVA, as shown in Figure 3.4.9. Therefore, the transfer capacity of the base case in 2026 is determined by the
voltage stability transfer capacity of 46.71MW, instead of the thermal capacity (316MVA).
The voltage stability transfer capacity of the system considering various contingencies are summarized in Table
3.4.6. It is shown that the system collapses in C1 and C3 contingencies. However, the system is able to
withstand C2 and C4 contingencies.
Table 3.4.10. Transfer Capacity Analysis Results (Scenario A, 2026)
Power Flow
Max
Max
Bus Voltage [p.u.]
Voltage
[MVA]
Loss Transfer Transfer
Cases
Name
[kV]
[MVA]
Cap
Cap
Namialo Metoro From
To
[MW]
[MVA]
N-0
110
1.0203 1.0622 -4.95.0+j0.0
0.146.71
91
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220
0.9879
Total
-
C1
110
1.0103
220
0.9854
Total
-
C2
N-1
C3
110
1.0375
220
0.9881
Total
-
C4
j7.9
41.11.0621
j53.8
36.261.7i
Diverge
1.0622
36.01.0621
j54.4
36.0j54.4
Diverge
-4.01.0622
j6.0
40.21.0621
j53.7
36.2j59.7
39.9+j25.0
34.9+j25.0
j7.9
1.2j28.8
1.3j36.7
0
34.9+j24.8
34.9+j24.8
1.1j29.6
1.1j29.6
43.9
-
0
4.0-j2.1
38.9+j24.6
34.9+j22.5
0.0j8.1
1.3j29.1
1.3j37.2
34.9
-
3.4.1.4 2031 year case
In this section the transfer capacity of 110kV and 220kV T/L is analyzed for the load levels of 2031.
Figure 3.4.10. Transfer Capacity Analysis (Scenario A: 2031, N-0)
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The additional real power transfer capacity and the line flow of Namialo-Metoro T/L considering the base case
is shown in Figure 3.4.10.
In the base case, the maximumreal power that could be transferred to the load is 57.66MW, with the line flow of
89MVA. Therefore, the transmission capacity of the system in the base case is determined by voltage stability
transfer capacity of 57.66MW, instead of the thermal rating of both lines (316MVA).
Furthermore, when contingencies are considered, the system failed to supply the load in all N-1 contingences
except the outage of 110kV T/L. The results of the simulation is summarized in Table 3.4.7.
Table 3.4.11. Transfer Capacity Analysis Results (Scenario A, 2031)
Case
s
Contingenc
y
N-0
Voltag
e [kV]
Bus Voltage
[p.u.]
Namial Metor
o
o
110
1.0328
220
0.9952
Total
-
C1
110
1.0238
220
0.9911
C2
N-1
Total
-
110
220
Total
-
C3
C4
Power Flow
[MVA]
Fro
To
m
-1.41.0406
1.4-j3.5
j4.6
51.91.0406
50.5+j14.
j42.5
7
50.549.1+j11.
j47.3
2
Diverge
1.0386
50.41.0386
49.1+j15.
j43.1
3
50.449.1+j15.
j43.1
3
Diverge
-
Loss
[MVA
]
Max
Transfe
r Cap
[MW]
Max
Transfe
r Cap
[MVA]
57.66
89
0.0j8.1
1.4j27.8
1.4j35.9
0
1.3j27.8
53.1
1.3j27.8
0
-
0
3.4.1.5 2036 year case
The power transfer capability of 110, 220kV Namialo-Metoro T/L is analyzed for 2036 load levels in this
section. In 2036, the system is unable to operate if must-run generators are not added near the Metoro area due
to low voltage levels resulting from fast load growth. Hence, it has been assumed that Palma ENI, Lurio, and
Nacala2 generation plantsare in operation with the output values of 0.0+j28.5MVA, 55+j11.2MVA, and 200j2.8MVA, respectively.
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Figure 3.4.11. Transfer Capacity Analysis (Scenario A: 2036, N-0)
The additional real power transfer capability of the system along with the line flows are shown in
Figure 3.4.11. Considering the load levels of 2036, the maximum real power transfer capability of the
system is 68.93MW, with line flow of 92MVA. Therefore, transfer capacity of Namialo-Metoro T/L is
determined by the voltage stability transfer capacity of 68.93MW, instead of the thermal capacity
(316MVA).
Furthermore, if N-1 contingency is considered in the system of 2031, all the considered cases failed to
converge, and the results are summarized in Table 3.4.8.
Table 3.4.12. Transfer Capacity Analysis Results (Scenario A, 2036)
Bus Voltage
Power Flow
[p.u.]
[MVA]
Case Contingenc Voltag
s
y
e [kV] Namial Metor
Fro
To
o
o
m
0.5110
1.0198 1.0399
-0.5-j0.9
j7.0
68.6220
0.9847 1.0399
66.3+j24.
N-1
j46.6
6
69.1Total
66.8+j23.
j53.6
7
N-1
C1
Diverge
72
Loss
[MVA
]
Transfe
r Cap
[MW]
Transfe
r Cap
[MVA]
68.93
92
0.0j7.9
2.3j22.0
2.3j29.9
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C2
C3
C4
Diverge
Diverge
Diverge
0
0
0
3.4.1.6 Transfer Capacity of 2032~2035
After 2032, must-run generations are required near the load area for a stable operation, and its
capacity ranges from j21.9MVA to j25.0MVA in the case of Palma ENI generation plant. Also, since
the base case does not converge, N-1 contingencies are not considered in this section.
Table 3.4.13. Transfer Capacity Analysis Results (2032~2035)
Bus Voltage
Power Flow [MVA]
[p.u.]
Voltag
Year
Name
e [kV] Namial Metor
From
To
o
o
Namialo
-Metoro
203
2
203
4
110
1.0142
1.0378
-1.5-j6.6
1.5-j1.2
0.0j7.8
220
0.9828
1.0377
55.8-j46.0
54.1+j20.
4
1.7j25.6
PalmaENI
Lurio
Nacala2
11
-
-
0.0+j24.7
-
-
33
220
-
-
55+j11.6
135.0-j3.7
-
Total
-
-
-
54.3-j52.6
52.6+j19.
2
110
1.0331
1.0429
-0.6-j5.2
0.6-j2.9
0.0j8.1
220
1.0038
1.0429
58.3-j40.6
56.7+j13.
7
1.6j26.9
-
-
Namialo
-Metoro
203
3
Loss
[MVA
]
PalmaENI
11
-
-
Lurio
33
-
-
Nacala2
220
-
-
Total
-
-
-
110
1.0221
220
0.9980
Namialo
-Metoro
0.0+j21.9
55.0+j10.
6
190.0j50.5
Ref.
0
Base
case
Must
-run
Gen.
Req.
0
Base
case
Must
-run
Gen.
Req.
0
Base
case
Must
-run
Gen.
1.7j33.4
-
-
-
-
57.7-j45.8
56.1+j10.
8
1.6j35.0
1.0417
-0.4-j6.6
0.5-j1.4
0.1j8.0
1.0416
62.0-j42.4
60.2+j17.
0
1.8j25.4
73
Additiona
l Transfer
Capabilit
y [MW]
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PalmaENI
Lurio
Nacala2
11
-
-
0+j24.9
-
-
33
220
-
-
55+j10.9
190-j33.2
-
Total
-
-
-
61.6-j49.0
59.7+j15.
6
110
1.0443
1.0439
0.7-j4.3
-0.7-j3.9
0.0j8.2
220
1.0012
1.0438
64.5-j42.2
62.6+j17.
2
1.9j25.0
-
-
-
-
-
-
63.3+j13.
3
1.9j33.2
Namialo
-Metoro
203
5
PalmaENI
11
-
-
Lurio
33
-
-
Nacala2
220
-
-
Total
-
-
-
0.0+j25.0
55.0+j10.
4
190.0j48.6
65.2-j46.5
Req.
1.9j33.4
0
Base
case
Must
-run
Gen.
Req
3.4.2.7 Results on 220kV T/L construction
In the system of 2016, its transfer capacity is determined by the thermal capacity of the Namialo-Metoro T/L.
However, after the 220kV T/L construction in 2018, the transfer capacity in all the following years is determined
by the voltage stability transfer capacity, ranging from 46.71MW to 116.83MW. The system is able to serve load
until 2031, however after 2031, must run generations have to be operated in order to operate the system reliably
and securely.
3.4.2Scenario B: 400kV T/L Construction, 220kV Operation
In this section, the parallel operation of 110kV T/L and 400kV T/L operating in 220kV is analyzed. The thermal
capacities of 110kV and 400(220)kV T/Ls are 77MVA and 715MVA, respectively. Therefore the total thermal
capacity of the Namialo-Metoro transmission system is 792MVA.
3.4.2.1 2018 year case
The transfer capability of 110kV and 400(220)kV T/L between Namialo and Metoro is analyzed under 2018
load levels, and the modeled system is shown in Figure 3.4.11.
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Figure 3.4.12. PSS/E Modeling of 110, 220kV Namialo-Metoro T/L Operation (2018)
Figure 3.4.13. Transfer Capacity Analysis (Scenario B: 2018, N-0)
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Figure 3.4.14. Transfer Capacity Analysis (Scenario B: 2018, N-1 (C1))
Figure 3.4.15. Transfer Capacity Analysis (Scenario B: 2018, N-1 (C3))
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Figure 3.4.16. Transfer Capacity Analysis (Scenario B: 2018, N-1 (C4))
The additional real power transfer capability and line flows in the base case and N-1 contingency case
of 2018 are shown in Figure 3.4.13, 3.4.14, 3.4.15, and 3.4.16.
In the base case, the maximum real power transfer capability of the system is 89.24MW with the line
flow of 106MVA. Therefore, the transfer capacity of the transmission system is determined by the
voltage stability transfer capacity (89.24MW), instead of the thermal capacity (792MVA).
Furthermore, the system was able to be operated even when N-1 contingencies were considered, and
the results are summarized in Table 3.4.10.
Table 3.4.14. Transfer Capacity Analysis Results (Scenario B, 2018)
Bus Voltage
Power Flow [MVA]
[p.u.]
Case Contingenc Voltag
s
y
e [kV] Namial Metor
From
To
o
o
110
1.0572 1.0489 10.9+j2. 11.9-j9.3
0
400
N-0
-2.3(220
1.0156 1.0489
2.3-j0.2
j42.4
oper.)
-13.2Total
14.2-j9.5
j40.4
24.3N-1
C1
110
1.0443 1.0489 22.6+j6.
j10.9
7
77
Loss
[MVA
]
Max
Transfe
r Cap
[MW]
Max
Transfe
r Cap
[MVA]
89.24
106
86.15
119
1.0j7.3
-j42.6
1.0j49.9
1.7j4.2
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C2
C3
C4
400
(220
oper.)
1.0042
1.0489
Total
-
-
110
400
(220
oper.)
1.0368
1.0489
1.0088
1.0489
Total
-
-
110
1.0345
1.0489
400
(220
oper)
1.0009
1.0489
Total
-
-
110
1.0452
1.0489
400
(220
oper)
1.0147
1.0489
Total
-
-
10.8j50.2
-11.8j43.5
-
10.7+j8.
9
0.1j41.3
-
1.8j45.5
-
-13.5j45.2
13.6+j3.
4
0.1j41.8
-13.5j45.2
-13.1j0.1
13.6+j3.
4
0.1j41.8
0.5j6.9
-
13.6-j2.0
13.6-j6.8
-
-
13.6-j6.8
0.5j6.9
11.2-j7.6
0.4j7.4
-2.4j42.9
2.4+j0.4
0.0j42.5
-13.2j42.7
13.6-j8.0
0.4j49.9
-13.1j0.1
10.8+j0.
2
7.4
-
50.15
-
86.21
101
3.4.2.2 2021 year case
The transfer capability of 110kV and 400(220)kV Namialo-Metoro T/L is analyzed for 2021. The
system model is the same, and only the loads have been changed to the levels of 2021.
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Figure 3.4.17. Transfer Capacity Analysis (Scenario B: 2021, N-0)
Figure 3.4.18. Transfer Capacity Analysis (Scenario B: 2021, N-1 (C4))
The additional real power transfer capability of the system and the line flows for Namialo-Metoro
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transmission system in the base and N-1 contingency case in 2021 is shown in Figure 3.4.17 and 3.4.18.
The maximum real power transfer capacity of the system is 63.63MW with the line flow of 106MVA. Therefore,
the transfer capacity of the Namialo-Metoro T/L in 2021 is determined by the voltage stability transfer capacity
of 63.63MW, instead of the thermal capacity (792MVA).
Accordingly, when N-1 contingency is applied to the system, the system was unable to supply power to loads in
the case of C1 and C3 contingencies. However, the system was able to withstand other contingencies.
The results of the simulation for Scenario B in 2021 are summarized in Table 3.4.11.
Table 3.4.15. Transfer Capacity Analysis Results (Scenario B, 2021)
Case
s
Contingenc
y
N-0
Voltag
e [kV]
Bus Voltage
[p.u.]
Namial Metor
o
o
110
1.0413
400
(220
oper.)
1.0065
Total
-
C1
C2
N-1
110
400
(220
oper.)
1.0349
Total
-
1.0042
C3
C4
110
1.0258
400
(220
oper)
0.9953
Total
-
Power Flow
[MVA]
Fro
To
m
-8.61.0590
8.8-j4.9
j3.0
33.71.0590
33.3+j17.
j56.8
2
25.124.5+j12.
j59.8
3
Diverge
1.0590
24.81.0590
24.5+j17.
j57.6
5
24.824.5+j17.
j57.6
5
Diverge
-8.71.0590
8.9-j2.6
j5.0
33.91.0590
33.4+j24.
j63.0
9
25.224.5+j22.
j68.0
3
Loss
[MVA
]
Max
Transfe
r Cap
[MW]
Max
Transfe
r Cap
[MVA]
63.63
106
0
-
40.5
-
0
-
50.19
109
0.2j7.9
0.4j39.6
0.6j47.5
0.3j40.1
0.3j40.1
0.2j7.6
0.5j38.1
0.7j45.7
3.4.2.3 2026 year case
In this section, the transfer capability of 110kV and 400(220)kV Namialo-Metoro T/L is analyzed for
the load levels of 2026.
80
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Figure 3.4.19. Transfer Capacity Analysis (Scenario B: 2026, N-0)
Figure 3.4.20. Transfer Capacity Analysis (Scenario B: 2026, N-1 (C1))
The additional real power transfer capability and its line flow of the base and N-1 case in 2026 are shown in
81
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Figure 3.4.19 and 3.4.20.
In 2026, the system is able to transfer maximum real power amount of 50.78MW to the load with the line flow
of 107MVA in the base case. Therefore, the transfer capacity of transmission system in 2026 is determined by
the voltage stability transfer capacity (50.78MW), instead of the thermal capacity (792MVA).
Furthermore, when the N-1 reliability standard was applied, the system collapsed when 220kV T/L and Namialo
400/220kV transformer was tripped. Also, tripping 110kV T/L did not have much effect on the system.
The results are summarized in Table 3.4.10.
Table 3.4.16. Transfer Capacity Analysis Results (Scenario B, 2026)
Case
s
Contingenc
y
Voltag
e [kV]
110
N-0
C1
Power Flow [MVA]
From
To
-8.3-j6.0
8.5-j1.7
400
(220
oper.)
0.9922
1.062
1
44.1j67.1
Total
-
-
35.8j73.1
110
1.0092
1.062
2
24.8+j1.
0
400
(220
oper.)
0.9843
1.062
1
62.6j71.5
Total
-
-
37.8j70.5
110
1.0151
1.062
2
-
400
(220
oper.)
0.9901
1.062
0
35.5j67.9
Total
-
-
35.5j67.9
N-1
C2
Bus Voltage
[p.u.]
Namial Metor
o
o
1.062
1.0236
2
C3
C4
Diverge
Diverge
43.4+j30.
8
34.9+j29.
1
26.8-j4.7
61.5+j39.
6
34.7+j34.
9
34.9+j30.
8
34.9+j30.
8
Loss
[MVA
]
Max
Transfe
r Cap
[MW]
Max
Transfe
r Cap
[MVA]
50.78
107
35.14
123
0.2j7.7
0.7j36.3
0.9j44.0
2.0j3.7
1.1j31.9
3.1j35.6
-
45.9
0.00
0.00
3.4.2.4 2031 year case
In this section, the transfer capability of 110kV and 400(220kV) Namialo-Metoro T/Ls are analyzed
for the year of 2031.
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Figure 3.4.21. Transfer Capacity Analysis (Scenario B: 2031, N-0)
The additional real power transfer capability and the line flow of the transmission system in 2031 for the base
case are shown in Figure 3.4.21.
The system is able to supply up to 61.23MW of real power to the load in the base case with the line flow of
97MVA. Therefore, the transfer capacity of Namialo-Metoro T/L is determined by the voltage stability transfer
capacity of 61.23MW instead of the thermal capacity (792MVA).
Furthermore, when N-1 reliability standard was applied, the system was unable to supply power to the loads,
except in C2 contingency.
The results are summarized in Table 3.4.13.
Table 3.4.17. Transfer Capacity Analysis Results (Scenario B, 2031)
Case
s
Contingenc
y
N-0
Voltag
e [kV]
Bus Voltage
[p.u.]
Namial Metor
o
o
110
1.0263
1.0398
400
(220
oper.)
0.9932
1.0398
Total
-
83
Power Flow
[MVA]
Fro
To
m
-5.96.0-j4.4
j3.4
55.755.1+j17.
j52.6
2
49.8j56.0 49.1+j12.
Loss
[MVA
]
Max
Transfe
r Cap
[MW]
Max
Transfe
r Cap
[MVA]
61.23
97
0.1j7.8
0.6j35.4
0.7j43.2
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8
C1
N-1
C2
C3
C4
110
400
(220
oper.)
1.0175
Diverge
1.0376
-
0.9892
1.0376
49.7j53.3
Total
-
-
49.7j53.3
0
49.1+j17.
4
49.1+j17.
4
Diverge
Diverge
0.6j35.9
53.1
0.6j35.9
0
0
3.4.2.5 2036 year case
The transfer capability of 110kV and 400(220)kV Namialo-Metoro T/Ls are analyzed for year 2036.
In 2036, due to a lengthy transmission system and high load levels, the system is unable to operate
without must-run generation plants due to low voltage levels in the loads. Therefore, in order to make
the system operable for simulation, Palma ENI, Lurio, and Nacala2 generation plants were assumed to
be in operation with generation amounts of 0.0+j25.5MVA, 55.0+j10.4MVA, and 200.0-j23.9MVA,
respectively.
Figure 3.4.22. Transfer Capacity Analysis (Scenario B: 2036, N-0)
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The additional real power transfer capability and the line flow of Namialo-Metoro T/L in 2036 is
shown in Figure 3.4.22. The maximum real power transfer capacity of the system in the base case is
72.83MW with the line flow of 105MVA. Therefore, the transmission capacity of the system is
determined by the voltage stability transfer capacity (72.83MW), instead of its thermal capacity
(792MVA).
The system failed to supply power to the loads in C1, C3, and C4 contingency cases. However,
tripping 110kV T/L did not have much effect on the transfer capacity of the system.
The summary of the simulation results is shown in Table 3.4.14.
Table 3.4.18. Transfer Capacity Analysis Results (Scenario B, 2036)
Bus Voltage
Power Flow
[p.u.]
[MVA]
Case Contingenc Voltag
s
y
e [kV] Namial Metor
Fro
To
o
o
m
-4.6110
1.0326 1.0433
4.7-j4.3
j3.6
400
72.4(220
0.9957 1.0433
71.4+j21.
N-0
j53.4
oper.)
2
67.8Total
66.7+j16.
j57.0
9
C1
Diverge
110
1.0212 1.0407
400
67.7(220
0.9903 1.0407
66.8+j22.
j54.8
C2
oper.)
2
N-1
67.7Total
66.8+j22.
j54.8
2
C3
Diverge
C4
Diverge
Loss
[MVA
]
Max
Transfe
r Cap
[MW]
Max
Transfe
r Cap
[MVA]
72.83
105
0.1j7.9
1.0j32.2
1.1j40.1
0
0.9j32.6
69.8
0.9j32.6
0
0
3.4.2.6 Transfer capacity for the years 2032~2035
In this section, the operation limit year of 110kV and 400(220)kV transmission system is identified.
After 2032, the system is required to operate must-run generation plants in order to be operable, and
additional power ranging from j23.2MVA to j23.8MVA is needed in the case Palma ENI generation
plant.
Table 3.4.19. Transfer Capacity Analysis Results (Scenario B, 2032~2035)
Bus Voltage [kV]
Power Flow [MVA]
Loss
Voltag
Year
Name
[MVA
Namial Metor
e [kV]
From
To
]
o
o
85
Additiona
l Transfer
Capabilit
y [MW]
Ref.
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110
1.0216
1.0394
-5.8-j4.0
5.9-j3.7
0.1j7.7
220
0.9902
1.0394
59.3-j54.0
58.5+j19.
6
0.8j34.4
PalmaENI
11
-
-
0.0+j23.2
-
-
Lurio
33
-
-
-
-
Nacala2
220
-
-
55.0+j11.
4
135-j17.4
-
Total
-
-
-
53.5-j58.0
52.6+j15.
9
110
1.0342
1.0442
-5.2-j3.3
5.3-j4.6
0.1j7.9
220
1.0059
1.0442
62.1-j48.3
61.4+j12.
8
0.7j35.5
Namialo
-Metoro
203
2
Namialo
-Metoro
203
3
203
4
11
-
-
0.0+j20.7
-
-
33
-
-
-
-
Nacala2
220
-
-
55+j10.2
190.0j54.2
-
-
Total
-
-
-
56.9-j51.6
-56.1+j8.2
110
1.0240
1.0429
-5.3-j4.4
5.4-j3.4
220
1.0005
1.0429
66.0-j50.5
65.1+j16.
3
0.9j34.2
-
-
-
-
-
-
203
5
11
-
-
Lurio
33
-
-
Nacala2
220
-
-
Total
-
-
-
60.7-j54.9
59.7+j12.
9
1.0j42.0
110
1.0460
1.0453
-4.5-j2.1
4.5-j5.9
0.0j8.0
0.9j33.9
Namialo
-Metoro
PalmaENI
Lurio
55.0+j10.
6
190.0j37.9
220
1.0038
1.0453
68.7-j50.2
67.8+j16.
3
11
-
-
0.0+j23.6
-
-
33
-
-
55.0+j10.
-
-
86
0
Base
case
Must
-run
Gen.
Req.
0
Base
case
Must
-run
Gen.
Req
0.8j43.4
0.1j7.8
PalmaENI
0+j23.8
0
Base
case
Must
-run
Gen.
Req.
0.9j42.1
PalmaENI
Lurio
Namialo
-Metoro
0
Base
case
Must
-run
Gen.
Req.
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Nacala2
220
-
-
0
190-j53.4
Total
-
-
-
64.2-j52.3
63.3+j10.
4
0.9j41.9
3.4.2.7 Results on 400kV T/L construction and 220kV operation
If the new T/L between Namialo and Metoro is constructed as 400kV rating, and operated on 220kV, the transfer
capacity of the Namialo-Metoro transmission system is always determined by the voltage stability transfer
capacity, and the maximum real power transfer capability ranges from 50.78MW to 89.24MW in the base case.
The system is unable to supply the load after 2031. After this year, the limit of 110kV and 400(220)kV
transmission system has been reached, and the must-run generation, in the load side, is required to operate the
system.
3.4.3Scenario C: 400kV T/L Construction, 400kV Operation
In this section, the parallel operation of 110kV and 400kV T/L between Namialo and Metoro is considered. The
thermal capacities of 110kV and 400kV linesare 77MVA and 1300MVA, respectively. Therefore, the thermal
rating of the transmission system is 1377MVA.
3.4.3.1 2018 year case
In this section, the transfer capacity of 110kV and 400kV Namialo-Metoro T/L is analyzed. The system diagram
used for the simulation is shown in Figure 3.4.23.
87
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Figure 3.4.23. PSS/E Diagram used for simulating 110, 400kV Namialo-Metoro T/L Analysis
From Figure 3.4.23, it is shown that the loads in Metoro area is supplied by 400kV (blue) and 110kV (red) T/Ls.
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Figure 3.4.24. Transfer Capacity Analysis (Scenario C: 2018, N-0)
Figure 3.4.25. Transfer Capacity Analysis (Scenario C: 2018, N-1 (C1))
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Figure 3.4.26. Transfer Capacity Analysis (Scenario C: 2018, N-1 (C4))
The additional real power transfer capacity and the line flow of Namialo-Metoro transmission system
for the base and contingency cases are shown in Figure 3.4.24, 3.4.25, and 3.4.26.
The maximum real power transfer capacity in the base case is 104.44MW with the line flow rating of
191MVA. Therefore, the transfer capacity of this system is determined by the voltage stability transfer
capacity (104.44MW), instead of the thermal rating (1377MVA) of the transmission system.
Moreover, the system was able to be operated stably in all contingency cases when N-1 reliability
criterion was applied.
The summary of the results is provided in Table 3.4.16.
Table 3.4.20. Transfer Capacity Analysis Results (Scenario C, 2018)
Bus Voltage [p.u.]
Cases
Contingenc
y
N-0
N-1
Power Flow [MVA]
Voltage
[kV]
Namialo
Metoro
From
110
1.0532
1.0489
-16.0+j4.1
400
1.0607
1.0795
3.4-j127.1
Total
-
-
-12.6j123.0
110
1.0516
1.0489
-27.3+j10.9
400
1.0578
1.0779
16.5-j131.3
C1
90
To
Loss
[MVA]
16.8j10.4
-3.3j25.6
13.5j36.1
29.9j13.0
16.4-
0.8j6.3
0.1j152.7
0.9j159.0
2.6j2.1
0.1j151.7
Max
Transfer
Cap
[MW]
Max
Transfer
Cap
[MVA]
104.44
191
103.5
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j20.4
C2
C3
Total
-
-
-10.8j120.4
13.5j33.4
2.7j153.8
110
1.0537
1.0489
-
-
-
400
1.0604
1.0796
-13.4j126.1
13.5j26.5
0.1j152.6
Total
-
-
-13.4j126.1
110
1.0345
1.0489
-13.0-j0.2
400
1.0197
1.0706
-
Total
-
-
-13.0-j0.2
1.0489
-19.9+j6.4
13.5j26.5
13.5j6.8
13.5j6.8
21.3j11.5
-7.8j33.2
13.5j44.7
0.1j152.6
0.5j7.0
0.5j7.0
1.4j5.1
0.0j154.1
1.4j159.2
110
C4
1.0535
400
1.0661
1.0822
7.8-j120.9
Total
-
-
-12.1j114.5
8.5
-
6.5
-
103.13
199
3.4.3.2 2021 year case
In this section, the transfer capacity of 110kV and 400kV Namialo-Metoro T/L is analyzed for the year of 2021.
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Figure 3.4.27. Transfer Capacity Analysis (Scenario C: 2021, N-0)
Figure 3.4.28. Transfer Capacity Analysis (Scenario C: 2021, N-1 (C1))
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Figure 3.4.29. Transfer Capacity Analysis (Scenario C: 2021, N-1 (C4))
The additional real power transfer capacity and the line flow of the system considering the load levels
of 2021 is shown in Figure 3.4.27, 3.4.28, and 3.4.29.
In the base case, the system was able to supply maximum real power of 103.98MW, with the line flow
rating of 201MVA. Hence, the transfer capacity of 2021 is determined by the voltage stability transfer
capacity (103.98MW), instead of the thermal capacity (1377MVA) of the transmission system.
Furthermore, it has been verified that the system was able to be operated stably in all contingencies,
except in the case of 400kV T/L outage.
The result of the simulation is summarized in Table 3.4.17.
Table 3.4.21. Transfer Capacity Analysis Results (Scenario C, 2021)
Bus Voltage
Power Flow [MVA]
[p.u.]
Case Contingenc Voltag
s
y
e [kV] Namial Metor
From
To
o
o
1.059
18.4110
1.0612
0
17.4+j4.5
j10.6
1.082
43.3-43.0N-0
400
1.0565
3
j148.6
j2.2
25.9-24.6Total
j144.1
j12.8
1.059
35.8N-1
C1
110
1.0519
32.3+j12.
0
j12.6
8
93
Loss
[MVA]
Max
Transfe
r Cap
[MW]
Max
Transfe
r Cap
[MVA]
1.0j6.1
0.3j150.8
1.3j156.9
103.98
201
3.5+j0.
2
87.95
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C2
400
1.0517
1.079
6
60.8j154.7
Total
-
-
28.5j141.9
60.5+j5.
9
-24.7j6.7
110
1.0614
1.059
0
-
-
-
400
1.0562
1.082
4
24.8j148.1
-24.6j3.2
0.2j151.3
Total
-
-24.6j3.2
0.2j151.3
C3
C4
24.8j148.1
Diverge
1.059
0
22.7+j6.5
-
110
1.0538
400
1.0546
1.081
2
49.2j151.0
Total
-
-
26.5j144.5
0.3j148.8
3.8j148.6
45.6
0
24.3j10.9
48.9+j0.
9
-24.6j10.0
1.6j4.4
0.3j150.1
93.6
211
1.9j154.5
3.4.3.3 2026 year case
In this section, the transfer capacity of 110kV and 400kV Namialo-Metoro T/L is analyzed for the
load levels of 2026.
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Figure 3.4.30. Transfer Capacity Analysis (Scenario C: 2026, N-0)
Figure 3.4.31. Transfer Capacity Analysis (Scenario C: 2026, N-1 (C1))
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Figure 3.4.32. Transfer Capacity Analysis (Scenario C: 2026, N-1 (C4))
The additional real power transfer capability and line flow of the system 2026 load levels are shown
in Figure 3.4.30, 3.4.31, and 3.4.32.
The system is able to supply maximum real power of 75.75MW with the line flow of 221MVA in the
base case. Therefore, the transfer capacity of the transmission system is determined by the voltage
stability transfer capacity of 75.75MW instead of its thermal capacity of 1377MVA.
Continuing, the system operated stably in all considered contingencies, except the outage of 400kV
T/L.
The results are summarized in Table 3.4.18.
Table 3.4.22. Transfer Capacity Analysis Results (Scenario C, 2026)
Bus Voltage
Power Flow [MVA]
[p.u.]
Case Contingenc Voltag
s
y
e [kV] Namial Metor
From
To
o
o
N-0
110
1.0423
1.0622
18.6+j1.
9
400
1.0406
1.0758
55.2j171.4
Total
-
-
36.6j169.5
96
19.7-j7.8
54.7+j25.
8
35.0+j18.
Loss
[MVA]
Max
Trans
. Cap
[MW
]
Max
Trans.
Cap
[MVA
]
75.75
221
1.1-j5.9
0.5j145.6
1.6j151.5
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0
C1
N-1
C2
110
1.0258
1.0622
34.3+j9.
9
400
1.0369
1.0736
73.7j175.8
Total
-
-
39.4j165.9
110
1.0405
1.0622
-
400
1.0403
1.0760
35.4j171.1
Total
-
-
35.4j171.1
C3
C4
Diverge
1.0622 24.3+j3.
9
110
1.0318
400
1.0381
1.0745
61.7j174.3
Total
-
-
37.4j170.4
38.0-j8.9
73.1+j32.
3
35.1+j23.
4
35.0+j24.
8
35.0+j24.
8
3.7+j1.
0
0.6j143.5
65.35
254
4.3j142.5
0.4j146.3
51
0.4j146.3
0
26.1-j7.8
61.1+j29.
7
35.0+j21.
9
1.8-j3.9
0.6j144.6
68.44
232
2.4j148.5
3.4.3.4 2031 year case
In this section, the transfer capability of 110kV and 400kV Namialo-Metoro T/L is analyzed for the
load levels of 2031.
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Figure 3.4.33. Transfer Capacity Analysis (Scenario C: 2031, N-0)
Figure 3.4.34. Transfer Capacity Analysis (Scenario C: 2031, N-1 (C1))
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Figure 3.4.35. Transfer Capacity Analysis (Scenario C: 2031, N-1 (C4))
The additional real power transfer capability and line flow of the transmission system for 2031 load
levels is shown in Figure 3.4.33, 3.4.34, and 3.4.35.
The maximum real power that the system can supply to the load is 92.95MW at line flow of 318MVA
in the base case. Therefore, the transfer capacity in the base case is determined by the voltage stability
transfer capacity of 92.95MW, instead of the thermal capacity (1377MVA).
Furthermore, when the N-1 reliability criterion was applied, the system was still able to withstand all
considered contingencies, except the outage of 400kV T/L.
The summary of simulation results is shown in Table 3.4.19.
Table 3.4.23. Transfer Capacity Analysis Results (Scenario C, 2031)
Bus Voltage
Power Flow [MVA]
[p.u.]
Case Contingenc Voltag
s
y
e [kV] Namial Metor
From
To
o
o
1.051
17.1110
1.0528
5
16.2+j3.8
j10.0
1.074
66.7-66.3N-0
400
1.0487
0
j147.5
j0.1
50.5-49.2Total
j143.7
j10.1
1.050
36.4N-1
C1
110
1.0416
32.8+j13.
2
j12.4
1
99
Loss
[MVA]
Max
Transfe
r Cap
[MW]
Max
Transfe
r Cap
[MVA]
0.9j6.2
0.4j147.6
1.3j153.8
92.95
318
3.6+j0.
7
75.61
319
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C2
400
1.0458
1.071
6
86.2j149.4
Total
-
-
53.4j136.3
85.7+j3.
7
-49.3j8.7
110
1.0526
1.048
7
-
-
-
400
1.0478
1.072
4
49.5j144.1
-49.2j4.0
0.3j148.1
Total
-
-49.2j4.0
0.3j148.1
C3
C4
110
1.0485
400
1.0493
Total
-
49.5j144.1
Diverge
1.051
7
20.9+j5.8
1.074
71.93
j147.3
51.0j141.5
-
0.5j145.7
4.1j145.0
72.2
0
22.3j10.7
-71.5j0.2
-49.2j10.9
1.4j4.9
0.4j147.5
1.8j152.4
84.58
317
3.4.3.5 2036 year case
In this section, the transfer capacity of 110kV and 400kV Namialo-Metoro transmission system is
analyzed for 2036 load levels.
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Figure 3.4.36. Transfer Capacity Analysis (Scenario C: 2036, N-0)
Figure 3.4.37. Transfer Capacity Analysis (Scenario C: 2036, N-1 (C1))
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Figure 3.4.38. Transfer Capacity Analysis (Scenario C: 2036, N-1 (C4))
The additional real power transfer capability and line flow of the transmission system for the year of 2036 is
shown in Figure 3.4.36, 3,4,37, and 3,4,38.
The maximum real power transfer capability of the system is 108.9MW with the line flow rating of 234MVA.
Therefore, the transfer capacity of the system is determined by the voltage stability transfer capability of
108.9MW, instead of the thermal rating of 1377MVA.
In addition, the system was able to be operated in all considered contingency cases except for the case of
tripping the 400kV T/L.
The results of the simulation are summarized in Table 3.4.20.
Table 3.4.24. Transfer Capacity Analysis Results (Scenario C, 2036)
Bus Voltage
Power Flow [MVA]
[p.u.]
Case Contingen Voltag
s
cy
e [kV] Namial Metor
From
To
o
o
1.053
110
1.0539
17.3-j10.0
0
16.4+j3.8
1.073
84.7N-0
400
1.0463
-84.2+j6.8
3
j152.7
68.3Total
-66.9-j3.2
j148.9
1.050
N-1
C1
110
1.0319
35.3+j13. 39.6-j11.3
6
5
102
Loss
[MVA]
Max
Transf
er Cap
[MW]
Max
Transf
er Cap
[MVA]
0.9j6.2
0.5145.9i
1.4j152.1
108.9
234
4.3+j2.
2
85.78
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C2
400
1.0418
1.069
3
107.1j154.5
106.5+j11
.6
0.6j142.9
Total
-
-
71.8j141.0
-66.9+j0.3
4.9j140.7
110
1.0541
1.050
4
-
-
-
400
1.0455
1.071
9
67.2j149.6
-66.9+j3.0
0.3j146.6
Total
-
-66.9+j3.0
0.3j146.6
C3
C4
110
1.0508
400
1.0472
Total
-
67.2j149.6
Diverge
1.053
4
20.8+j5.9
1.073
89.78
j152.3
68.9j146.4
-
88.9
0
22.2-j10.8
-89.2+j6.5
-67.0-j4.3
1.4j4.9
0.5j145.8
1.9j150.7
101.63
236
In 2036, the transferred power to Metoro area flows in opposite direction for 400kV and 110kV T/L. Although
the system fails in the case of largest contingency (tripping 400kV T/L), this problem may be mitigated through
operating a must-run generation near the load side. The required amount of generation in the load side for a
stable operation is 28+j12.6MVA and 20+j20.2MVA for Lurio G1 and Palma ENI, respectively.
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3.4.4.Simulation Results
The summarized results for each scenario for the considered years are displayed in Table 3.4.21.
Due to complexity of the table, several notations are used, which are:
B: Base Case
D: Diverge
U: Unstable
N-1 Cases:
1.
C1: Namialo 220/110kV Transformer Trip
2.
C2: 110kV Namialo-Metoro T/L Trip
3.
C3: 400kV or 220kV Namialo-Metoro T/L Trip (Could be 400kV or 220kV T/L depending on the
Scenario)
4.
C4: Namialo 400/220kV Transformer Trip
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Table 3.4.25. Summary of transfer capability analysis results for 2016~2036
Scenario A: 110kV, 220kV
Scenario B: 110kV, 400(220)kV
Max
Max
Max
Max
Thermal
Thermal
Transfer Transfer
Transfer
Transfer
Capacity
Capacity
Capacity Capacity
Capacity
Capacity
[MVA]
[MVA]
[MW]
[MVA]
[MW]
[MVA]
N-0
63.66
88
‘16
N-1
C1
39.04
43
C2
-
-
C3
-
C4
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
116.83
134
89.24
106
104.44
191
C1
108.41
128
86.15
119
103.5
213
C2
0
-
7.4
-
8.5
-
C3
0
-
50.15
-
6.5
-
C4
110.01
125
86.21
101
103.13
199
58.06
97.5
63.63
106
103.98
201
C1
0
-
0
-
87.95
234
C2
28.5
-
40.5
-
45.6
-
C3
0
-
0
-
0
-
C4
0
-
50.19
109
93.6
211
46.71
91
50.78
107
75.75
221
0
-
35.14
123
65.35
254
45.9
-
51
-
N-0
‘18
N-1
N-0
‘21
N-1
N-0
C1
‘26
N-1
N-1
N-1
316
792
43.9
-
C3
0
-
0
-
0
-
C4
34.9
-
0
-
68.44
232
57.66
89
61.23
97
92.95
318
C1
0
-
0
-
75.61
319
C2
53.1
-
53.1
-
72.2
-
C3
0
-
0
-
0
-
C4
0
0
0
-
84.58
317
68.93
92
72.83
106
108.9
234
C1
0
-
0
-
85.78
248
C2
0
-
69.8
-
88.9
-
C3
C4
0
0
-
0
0
-
0
101.63
236
N-0
‘36
77
C2
N-0
‘31
Scenario C: 110kV, 400kV
Max
Max
Therma
Transfer
Transfer
Capacit
Capacity
Capacity
[MVA
[MW]
[MVA]
-
Inception Report
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3.5 Short Circuit Analysis
3.5.1 Current System Status (2016)
For the substations that will be affected by the installation of new transmission line (T/L) between Namialo and
Metoro, a three phase to ground short circuit analysis was conducted, and the results are shown in Table 3.5.1.
Table 3.5.26 Short Circuit MVA and Fault current of substation (2016 year)
Source Impedance[pu]
Bus
Voltage[kV]
SCMVA[pu] Fault current[A]
Metoro
110
1.38
724.7519
Z+:0.462897+j0.593838
Macomia
110
0.91
477.9161
Z+:0.612170+j0.936092
Mocimbua
110
0.71
372.8796
Z+:0.725866+j1.203414
Pemba
110
1.22
640.7227
Z+:0.503492+j0.668175
Namialo
110
4.79
2515.624
Z+:0.178264+j0.121104
Namialo
220
5.90
1549.288
Z+:0.144386+j0.085400
Namialo
400
5.89
850.6644
Z+:0.140811+j0.095019
The results show that the fault current flowing through the 400/110kV Namialosubstation was 2.5kA, and 1.5kA
for the 400/220kV Namialosubstation, both of which are about five times the normal rating. For other
substations, the fault current did not exceed 1kA, showing a moderate fault characteristics. Furthermore, since
the substations at Macomia and Mocimbuahas a source impedance of 0.6~0.7p.u.,difference between the base
and fault current was very small.
3.5.2 Scenario A : 220kV T/L construction, 220kV operation
The three phase to ground fault currents for the years between 2018 and 2036 are shown in Table 3.5.2 in the
case of constructing a 220kV T/L between Namialo and Metoro. After 2016, the fault currents in each scenario
increases every year. The fault current of 110kV Metoro bus displayed a 410% increase in 2036 compared to the
fault current level of 2016, and Pemba substation displayed a 570% increasein 2036 compared to the fault
current level of 2016. On the contrary, the substations in Namialo, Macomia, and Mocimbua, displayed only a
slight increase of around 210~320% compared to the fault current levels of 2016.
Table 3.5.27 short circuit current of secnarioA(220kV T/L)
Base
2016
2018
2021
2026
Bus
voltage
Fault current [kA]
[kV]
110
0.725
2.962
3.219
3.351
Metoro
220
0.909
1.610
1.675
Macomia
0.478
0.583
0.940
0.961
Mocimbua
110
0.373
1.481
0.599
0.609
Pemba
0.641
1.786
1.896
1.959
110
2.516
3.293
3.766
3.934
Namialo
220
1.549
2.279
2.673
2.831
400
0.851
1.245
1.450
1.522
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4.685
2.342
1.513
0.777
3.587
4.165
3.070
1.638
4.769
2.382
1.513
0.777
3.640
4.349
3.232
1.704
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6000
5000
Metoro110kV
Metoro220kV
4000
Macomia110kV
3000
Pemba110kV
Namialo110kV
2000
Namialo400kV
1000
Namialo220kV
0
2016
Figure
2018
2021
2026
2031
2036
3.5.10 short curcuit currenttrends of scenario A (220kV T/L)
3.5.3 Scenario B : 400kV T/L construction, 220kV operation
The three phase to ground fault currents for constructing the Namialo-Metoro T/L as a 400kV line and operating
it with 220kV are shown in Table 3.5.3. Although the fault current of 110kV Metoro substation increases by 110%
in comparison with Scenario A, the fault current calculations of other substations were very similar to the results
of Scenario A. This shows that the changes in transmission line coefficients from 400kV T/L installation do not
have a significant impact on the magnitude of the fault currents.
Table 3.5.28 short circuit current of scenario B(400kV construction, 220kV operation)
Base
2016
2018
2021
2026
2031
Bus
voltage
Fault current [kA]
[kV]
110
0.725
3.309
3.435
3.435
5.136
Metoro
220
1.654
1.657
1.657
2.568
Macomia
0.478
0.935
1.423
1.423
1.534
Mocimbua
110
0.373
0.599
0.751
0.751
0.783
Pemba
0.641
1.906
3.141
3.141
3.713
110
2.516
3.282
3.802
3.802
4.165
Namialo
220
1.549
2.295
2.820
2.820
3.138
400
0.851
1.251
1.508
1.508
1.665
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5.252
2.626
1.539
0.783
3.771
4.349
3.298
1.735
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6000
5000
Metoro110kV
Metoro220kV
4000
Macomia110kV
3000
Pemba110kV
Namialo110kV
2000
Namialo220kV
1000
Namialo400kV
0
2016
2018
2021
2026
2031
2036
Figure 3.5.11 short circuit current of scenario B(400kV construction, 220kV operation)
3.5.4Scenario C : 400kV T/L construction, 400kV operation
The calculated three phase to ground short circuit currents when constructing the Namialo-Metoro T/L as 400kV
and operating it on 400kV are shown in Table 3.5.4. Similarly, although the 110kV Metoro substations bus and
110kV Pemba bus showed a 130% and 110% increase in the level of fault current, respectively, the fault currents
of other substations did not show much difference with the fault currents calculated in Scenario A. This result,
again, verifies that the change in T/L coefficients does not have much impact on the magnitude of the fault
currents.
Table 3.5.29 short circuit current of scenario C(400kV operation)
Base
2016
2018
2021
2026
Bus
voltage
Fault current [kA]
[kV]
110
0.725
3.850
4.333
4.564
Metoro
220
1.102
1.254
1.327
Macomia
0.478
0.977
1.014
1.029
Mocimbua
110
0.373
0.614
0.630
0.635
Pemba
0.641
2.085
2.243
2.300
110
2.516
3.225
3.655
3.860
Namialo
220
1.549
2.195
2.542
2.734
400
0.851
1.242
1.443
1.547
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5.971
1.616
1.570
0.793
3.907
4.128
3.075
1.787
6.155
1.672
1.576
0.798
3.976
4.312
3.225
1.860
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5000
Metoro110kV
Metoro220kV
4000
Macomia110kV
3000
Pemba110kV
Namialo110kV
2000
Namialo220kV
1000
Namialo400kV
0
2016
2018
2021
2026
2031
2036
Figure 3.5.12 short circuit current of scenario C(400kV operation)
3.5.5Summary of short circuit study
The three phase to ground short circuit current is usually affected by the location of the fault in the
Theveninequivalent circuit. When the Northern part of the power system is supplied by the source that is more
than 1300km away from Namialo substations, the impact of change in transmission line coefficients for
Namialo-Metoro T/L, is relatively small.
The summary of the results for different scenarios are as follows:
1.
Since the 400kV Namialo substation is a source terminal, it is merely affected by the higher voltage
operations (220, 400kV, shown in Figure 3.5.4, 3.5.5).
2.
On the contrary, the fault current of 220/110kV Metoro substation increases by 410~660% for 220kV
operation, and 530~850% for 400kV operation compared to the base case. Therefore, relays with
higher capacity should be considered for higher voltage operations (Figure 3.5.6, 3.5.7).
3.
The change in the magnitude of the fault currents of other substations, (Pemba, Macomia, and
Mocimbua), are relatively small (within 110% range). Therefore, the T/L upgrade will not have a
significant impact on the relay capacities of these substations.
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5000
4000
Namialo110kV 220kVup
3000
Namialo110kV
2000
400/220kVup
Namialo110kV 400kV up
1000
0
2016
2018
2021
2026
2031
2036
Figure 3.5.13 fault currents of Namialo S/S 110kV bus
4000
3000
Namialo220kV 220kVup
2000
Namialo220kV
400/220kVup
1000
Namialo220kV400kVup
0
2016
2018
2021
2026
2031
2036
Figure 3.5.14 Fault current of Namialo S/S 220kV bus
8000
6000
Metoro110kVBus_220kVup
4000
Metoro110kVBus_400/220k
Vup
2000
Metoro110kV Bus_400kV
up
0
2016
2018
2021
2026
2031
2036
Figure 3.5.15 Fault current of Metoro S/S 110kV bus
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3000
2500
Metoro220kV_200kVup
2000
1500
Metoro220kV_400/220kVu
1000
p
Metoro220kV_400kVup
500
0
2016
2018
2021
2026
2031
2036
Figure 3.5.16 Fault current of Metoro S/S 220kV bus
5000
4000
Pemba110kV Bus 220kVup
3000
Pemba110kV Bus
2000
400/220kVup
Pemba110kV Bus 400kVup
1000
0
2016
2018
2021
2026
2031
2036
Figure 3.5.17 Fault current of Pemba S/S 110kV bus
2000
1500
Macomia110kV Bus_220kV
up
1000
Macomia 110kV Bus
400/220kVup
500
Macomia 110kV Bus
400kVup
0
2016
2018
2021
2026
2031
2036
Figure 3.5.18 Fault current of Macomia S/S 110kV bus
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3.6 Discussion
3.6.1 Technical Analysis Results
3.6.1.1. Power Flow
3.6.1.1.1 System losses
The benefits from the construction of Namialo-Metoro T/L should not only be accounted for the loss reduction
between Namialo and Metoro but also the system-wide loss reduction effect.
Therefore, in order to compare this effect, the system and T/L losses are analyzed in this section.
A. Loss for 100% Load Level
A-1. System Loss
1200
1000
814
800
600
889
1075
967
641
total demand growth[MW]
400
200
0
2016
2021
2026
2031
2036
Figure 3.6.19 demand growth of northern system(2016~2036)
350
300
Loss-SCA100%
250
200
Loss SCB100%
150
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
100
Loss SCC100%
Figure 3.6.20 annual system losses for each scenario
Annual load forecast and system loss [MW] is shown in Figure 3.6.1 and 3.6.2. System loss has been calculated
using the forecasted load values, and for three different T/L construction scenarios.
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Table 3.6.30System losses in peak load [MW]
Year
2018
2019
2020
2021
2022
SCA 100%
136.31
155.44
187.28
229.75
236.42
SCB 100%
135.73
155.23
186.52
228.25
235.32
SCC 100%
135.25
153.01
182.87
221.96
229.29
2027
2028
2029
2030
2031
2032
276.89
295.64
303.28
296.59
249.21
256.12
275.43
293.72
301.02
294.3
242.78
250.7
268.13
284.66
290.96
284.89
235.07
238.39
Loss reduction effect for three scenarios are shown in Figure 3.6.3.
Table 3.6.31 electric energy losscomparision [GWh/year]
Year
2018
2019
2020
2021
SCA 100%
693
790
952
1167
SCB 100%
690
789
948
1160
SCC 100%
687
777
929
1128
2027
2028
2029
2030
2031
1407
1502
1541
1507
1266
1399
1492
1529
1495
1234
1362
1446
1478
1447
1194
2022
1201
1196
1165
2032
1301
1274
1211
2023
243.61
242.21
235.56
2033
219.12
217.41
213.43
2024
257.04
254.79
246.6
2034
234.24
232.08
227.15
2025
269.66
268.08
250.9
2035
251.46
249.12
243.03
2026
290.2
288.08
278.58
2036
270.48
262.99
254.21
2023
1238
1231
1197
2033
1113
1105
1084
2024
1306
1295
1253
2034
1190
1179
1154
2025
1370
1362
1275
2035
1278
1266
1235
2026
1474
1464
1415
2036
1374
1336
1292
Loss reduction effects[MW.peak]
손실차:400/220-220kV
손실차:400kV-220kV
18,76
2036
2035
2034
2033
2032
2031
2030
2029
2028
2027
2026
2025
2024
2023
2022
2021
2020
2019
2018
17,73
16,27
14,14
12,32
1
1,7
11,62
10,98
10,44
8,76
8,43
7,797,138,05
6,435,425,697,09 7,49
4,41
2,43
2,251,582,121,461,922,262,29
1,712,162,34
0,74
0,260,210,761,5 1,1 1,4
Figure 3.6.21Comparison of loss reduction effect (Scenario A base)
The total system loss and transmission losses for 20 years have been calculated in Table 3.6.2 using the loss
values at peak loads and loss rate value of 0.58. If loss reduction benefit factor of 0.18 $/kWh (2021년예상전기
요금: 정산진 16.0524), loss cost is $4261, $4219, $4092 million for Scenario A, B, and C, respectively.
Furthermore, loss cost can be reduced by $169 million in case of Scenario C.
Table 3.6.32System power loss cost for scenarios [Million USD/year]
Annual Loss
2018
2019
2020
2021
2022
2023
SCA 100%
125
142
171
210
216
223
SCB 100%
124
142
171
209
215
222
SCC 100%
124
140
167
203
210
215
2027
2028
2029
2030
2031
2032
2033
253
270
277
271
228
234
200
Inception Report
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235
233
226
2034
214
2025
247
245
229
2035
230
2026
265
263
255
2036
247
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252
245
269
260
275
266
269
261
222
215
229
218
199
195
212
208
228
222
241
232
A-2.Namialo-Metoro T/L Losses
The T/L losses using peak load for years from 2018 to 2036 is shown in Figure 3.6.4 and Table 3.6.4.
Figure 3.6.22Transmission route power losses, 100% load [MW/peak]
3
2,5
2
SCA 100%ED
1,5
SCB 100%ED
1
SCC 100% ED
0,5
Table 3.6.33 transmission line energy losses, 100% load [GWh/year]
T/L Losses
2018
2019
2020
2021
2022
SCA 100%
0.51
1.52
2.03
4.06
3.05
SCB 100%
0.51
1.02
1.02
2.03
1.52
SCC 100%
0.51
0.51
1.02
1.52
1.02
2027
2028
2029
2030
2031
2032
5.08
6.10
6.61
6.61
7.11
12.70
2.03
3.05
3.05
3.05
3.05
4.06
2.03
1.52
2.03
2.03
2.03
2.03
2036
2035
2034
2033
2032
2031
2030
2029
2028
2027
2026
2025
2024
2023
2022
2021
2020
2019
2018
0
2023
3.56
2.03
1.02
2033
8.13
3.56
1.52
2024
5.08
2.54
1.52
2034
9.15
4.06
2.03
2025
4.06
2.03
1.52
2035
9.65
4.57
2.03
2026
6.61
3.05
2.54
2036
11.69
5.08
2.54
Table 3.6.34 transmission line loss costs, 100% load [Million USDollar/yr]
Loss Cost [M$/yr]
2018
2019
2020
2021
2022
2023
2024
2025
2026
SCA 100%ED
0.09
0.27
0.37
0.73
0.55
0.64
0.91
0.73
1.19
SCB 100%ED
0.09
0.18
0.18
0.37
0.27
0.37
0.46
0.37
0.55
SCC 100% ED
0.09
0.09
0.18
0.27
0.18
0.18
0.27
0.27
0.46
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
0.91
1.10
1.19
1.19
1.28
2.29
1.46
1.65
1.74
2.10
0.37
0.55
0.55
0.55
0.55
0.73
0.64
0.73
0.82
0.91
0.37
0.27
0.37
0.37
0.37
0.37
0.27
0.37
0.37
0.46
Losses for the system and T/L from 2018 to 2036, for different scenarios are shown in Table 3.6.6.
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Table3.6.35Comparison between system losses and Transmission line losses, 100% load
System
Transmission Lines
Incremental
dWloss[GWh]
dWloss[GWh]
Loss[GWh]
Loss
Line loss[Gwh]
SCA
SCA
cost[M$]
SCA
23,670
0
0
113.3
0
SCB
23,442
229
41
51.3
62.0
SCC
22,731
939
169
31.0
82.3
Incremental
Loss
cost[M$]
0
11
15
From the table above, it has been shown that the system loss is much larger compared to the T/L losses, which is
due to the long range power transmission, coming from the sources located in the Northwest area.
Furthermore, as the system load increases continuously, loss is affected by composition of generation sources.
After 2026, the system reaches power transfer limit if hydro or coal power plant is used to meet the loads. Hence,
must run generations located in eastern area have to be operated. Although must-run generations bring the
benefit of loss reduction, increased system wide generation cost should also be considered during economic
evaluation. For instance, if loads after Metoro substation is increased by 10MW, 16MW is required to meet this
load level using CBNB, whereas only 8.5MW is needed using NacalaVelha.
B. 110% Load Level
B-1.System Loss for 110% Load Level
If loads follow 110% of the forecasted load level, its system losses are shown in Figure 3.6.5.
In this case, for each scenario, must-run generation should be operated to meet the increasing loads, and also to
be operated stably.
Total system loss for each scenario, keeping the must-run generation at a constant level, is shown in Table 3.6.7.
400
350
300
SCA110%ED Loss
SCB110%ED Loss
250
SCC110%ED Loss
200
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2035
2034
2033
2032
2031
2030
2029
2028
2027
2026
2025
2024
2023
2022
2021
2020
2019
2018
150
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Figure 3.6.23 system losses for 110% load, peak [MW]
Table 3.6.36 System losses for each scenario, 110% load,
[GWh/yr]
2018
2019
2020
2021
2022
2023
2024
2025
2026
SCA
898.6
1003.3
1105.6
1343.5
1470.7
1515.6
1545.3
1569.6
1585.2
SCB
898.5
1001.4
1102.9
1336.4
1463.7
1507.0
1535.3
1551.1
1567.2
SCC
895.3
988.5
1088.9
1314.7
1431.6
1477.2
1501.9
1554.9
1532.7
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
1487.8
1486.5
1562.2
1538.5
1379.9
1360.7
1362.7
1550.2
1542.1
1769.6
1487.1
1479.2
1553.2
1528.6
1376.3
1305.3
1351.2
1548.7
1542.1
1768.3
1451.8
1452.4
1523.3
1499.6
1329.3
1290.3
1315.7
1505.0
1523.8
1731.7
B-2.Namialo-MetoroT/L Losses
The transmission losses of Namialo-Metoro corridor for 110% load level of each scenario is shown in Figure
3.6.6. Although the total power loss for each scenario through the projected period (2018~2016) is 102.63, 59.45,
and 56.40 [GWh], for SCA, SCB, and SCB, in order to minimize the losses, the new T/L should be constructed
as 400kV T/L, and operated as 220kV until 2022, and stepped up to 400kV at 2023 (Total loss reduced to
49.28GWh).
6
5
4
SCA110% N-Mloss
3
SCB110% N-Mloss
SCC110% N-Mloss
2
1
0
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Figure 3.6.24Namialo-Metoro T/L loss(110% Load, Peak)
The figure below shows annual loss of Namial-Metoro T/L for three scenarios.
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6
5
4
3
A110kV
2
A220kV
1
0
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
6
5
4
3
B110kV
2
B220kV
1
0
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
6
5
4
3
C110kV
2
C400kV
1
0
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Figure 3.6.25 Transmission line loss composition of Namialo-Metoro Corridor
C. System planning not on schedule (100% Load level, Without Lurio hydro plant)
C-1.System Losses
In this section, power flows analysis was performed assuming that the Lurio hydro plant is out of service, and
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system loss was derived from the power flow analysis results. The system loss at peak loads and must run
generations for different scenarios are obtained by dispatching the generators evenly throughout the system, and
the results are shown in the figure below.
600
SC0100%
500
mustrun
400
600
300
200
200
100
100
0
0
16 18 20 22 24 26 28 30 32 34 36
16 18 20 22 24 26 28 30 32 34 36
600
600
400
SCA100% Loss
400
300
500
SCA100% mustrun
500
SCB100% mustrun
SCB100% Loss
500
400
SCC100%
mustrun
SCC100%
Loss
300
300
200
200
100
100
0
0
16 18 20 22 24 26 28 30 32 34 36
16 18 20 22 24 26 28 30 32 34 36
Figure 3.6.26 T/L Loss and must-run generation of N-M corridor for scenario (100% Load, Lurio off)
For Scenario 0 (No new T/L construction), power flow analysis does not converge after 2020 if must-run
generations are not operated, meaning that the power cannot be transferred to the loads. Furthermore, generation
has been evenly dispatched throughout the system in order to compare the loss reduction effect in three
scenarios, therefore, must-run generation levels have not been changed.
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400
350
300
250
SCA100% Loss
200
SCB100% Loss
150
SCC100% Loss
100
50
0
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Figure 3.6.27.System loss for three scenarios assuming Lurio is not in service[MW]
The annual system loss [GWh/yr] for each scenario is shown in Table 3.6.8.
Table 3.6.8 Power loss inNamialo-MetoroT/L [GWh/yr : 100% Load, Lurio not in service)
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
SC0100%
646
766
956
1102
1398
1479
1308
1514
1865
1478
1314
SCA100%
646
766
865
923
1119
1547
1469
1523
1623
1723
1349
SCB100%
646
766
860
915
1110
1529
1454
1500
1593
1686
1288
SCC100%
646
766
848
899
1086
1468
1416
1450
1528
1635
1293
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
Total
SC0100%
1807
1776
1232
1751
1241
1739
1791
1279
1441
1381
27851
SCA100%
1814
1785
1775
1770
1329
1796
1673
1227
1472
1440
28224
SCB100%
1777
1748
1729
1729
1326
1751
1627
1191
1385
1440
27636
SCC100%
1701
1676
1645
1658
1286
1684
1560
1181
1435
1400
26852
From the table above, using SCA as the base case, loss reduction of 588GWh and 1372GWh can be realized for
SCB and SCC, respectively. The annual loss difference, using Scenario A as base case, for Scenario B and C is
shown in the Figure below.
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140,0
128,9
120,0
113,0
100,0
95,4
88,6
80,0
78,2
60,0
0,0
87,2
A-B
73,2
61,4
56,5
53,5
46,2
40,0
20,0
111,8 112,3
111,5
109,3
37,8
33,3
17,3
5,5
24,1
7,9
9,8
37,1 37,4
41,1 42,6
30,2
17,5 15,2
A-C
45,2 46,5 45,9
39,3
35,7 36,8
23,3
2,3
0,0
18 19 20 21 22 23 24 25 26 27 228 29 30 31 32 33 34 35 36
Figure 3.6.28Annual power loss between scenarios using SCA as the base case[GWh/yr]
C-2.T/L loss in Namialo – Metoro Corridor
각시나리오의해당년도최대전력에대한손실계산결과선로손실의추이는그림과같다. 부하증가에따라손
실증가가균일하지않은것은 must-run 발전기들이병입되기때문이다.
6
5
4
Corri Loss SCA
3
Corri Loss SCB
2
Corri Loss SCC
1
0
18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Figure 3.6.29Namialo-Metoro corridor의선로손실(MW : peak load case)
The losses occurring in high and low voltage lines for each scenario is shown in Figure 3.6.12 and Table
3.6.9.According to these results, most loss occurs in high voltage transmission lines, and transmission loss
reduction of 257GWh can be realized throughout the project period (‘18~’36) if SCC (400kV) is used.
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6
4
SCA-110kV
SCA-220kV
2
0
18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
5
3
SCB-110kV
SCB-220kV
1
-1
18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
5
3
SCC-110kV
SCC-400kV
1
-1
18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Figure 3.6.30 Loss comparison of N-M Corridor for different Scenario (In the order of Scenario A, B,
C)(MW, 100% Load, Lurio off)
Table 3.6.9 Annual Loss of N-M Corridor T/L for each scenario(GWh/yr, 100%, Lurio off)
[GWh]
18
19
20
21
22
23
24
25
26
27
Loss SCA
7
9
11
15
14
16
18
17
16
18
Loss SCB
3
6
5
7
6
7
8
7
8
8
Loss SCC
1
2
1
2
2
2
2
2
2
2
28
29
30
31
32
33
34
35
36
total
Loss SCA
19
22
21
14
20
26
7
10
15
295
Loss SCB
8
9
8
7
8
11
4
6
15
138
Loss SCC
3
3
3
2
2
3
3
2
2
38
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3.6.1.1.2 Must-Run Generation
Typically, dispatching generators in power systems are performed in the order of generator with the lowest cost
to generator with the highest cost, called economic dispatch. However, for systems like Northern Mozambique,
where distant power source is used to supply the load, generations near the load area must be operated in order
to supply power securely and reliably. These generations are called must-generations, and they must be operated
for secure operation of the system regardless of its high operation costs.
A. 100% Load Level
In 100% load level, power flow analysis results show that all three scenarios require must-run generations after
2027. Must run generations include Nacala 2, Palma ENI, Lurio, and Messalo, however, Lurio and Messalo, are
exempted from consideration since it is a hydro plant, and its operation can be affected by the water level of the
system. Therefore, Nacala 2 and Palma ENI was selected as must-run generations, and the annual generation
levels of these sources are shown in Table 3.6.9 and Figure 3.6.13.
Table 3.6.37. Required Must-run Gen capacities for 3 scenarios
Must-runGen
Nacala2
Scenario A
PalmaENI
Nacala2
Scenario B
PalmaENI
Nacala2
Scenario C
PalmaENI
2027
30
0
30
0
30
0
2028
30
0
30
0
30
0
2029
40
0
40
0
40
0
2030
60
0
60
0
60
0
2031
120
0
120
0
120
0
2032
135
0
135
0
135
0
2033
190
0
190
0
190
0
2034
190
0
190
0
190
0
2035
190
0
190
0
190
0
2036
200
0
200
0
200
0
250
200
220kV Nacala2
220kV PalmaEni
150
400/220kV Nacala2
100
400/220kV PalmaEni
400kV Nacala2
50
400kV PalmaEni
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
0
Figure 3.6.31. Required Must-run Gen capacities for three scenarios
B. 110% Load Level
The must-run generation levels are shown in Table 3.6.9 and Figure 3.6.14 for 110% load level. Compared to
100% load levels, it requires earlier operation of must-run generations, which is due to the operation of Lurio
hydro plant. For SCA and SCB, NacalaVelha must-run generation is operated in 2020, and even though the
generation amount for each case is different, it shows that must run generation is required to operate the system.
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Table 3.6.38Must-run generation (110% Load)
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
SCA110%
0
55
55
55
85
85
85
85
95
105
175
SCB110%
0
55
55
55
85
85
95
95
95
105
120
SCC110%
0
55
55
55
55
95
95
95
95
95
110
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
sum
SCA110%
155
172
180
200
245
270
290
280
280
280
3232
SCB110%
225
172
180
185
250
260
290
283
280
275
3245
SCC110%
116
150
150
170
245
250
275
270
270
305
3006
350
300
250
200
SCA110%
150
SCB110%
100
SCC110%
50
2036
2035
2034
2033
2032
2031
2030
2029
2028
2027
2026
2025
2024
2023
2022
2021
2020
2019
2018
2017
2016
0
Figure 3.6.32Must-run generation (110% load)
The system loss for 110% load level is shown in Figure 3.6.15. In 2020, SCA and SCB utilize 30MW output
from NacalaVelha for secure operation of the system, and reduce the loss rate to 16%. However, must –run
generations are not required for SCC, and the loss rate is around 18%. If NacalaVelha is operated in SCC with
output level of 40MW, the loss rate was reduced to 17.5%.
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0,22
0,2
0,18
SCA110%EDsys손실률
0,16
SCB110%EDsys손실률
0,14
SCC110%EDsys손실률
0,12
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
0,1
Figure 3.6.33System loss ratios (110% load)
C. System components not following construction/operation schedule (Lurio off, 100% Load level)
The required amount of must run generation is shown in Table 3.6.10 and Figure 3.6.16, in case of Lurio hydro
plant (180MW) not following the construction/operation schedule. For SC0 (no new T/L construction), great
amount of generation is required from NacalaVelha after 2021, for system operation. Must run generation is
required after 2026 for SCA, SCB, and SCC.
Table 3.6.39 Must-run generation (MRG) (Lurio Generation off, 100% Load)
MRG[MW]
16
17
18
19
20
21
22
23
24
25
26
SC0100%
0
0
0
0
0
65
128
92
40
105
160
SCA100%
0
0
0
0
0
0
0
0
0
0
90
SCB100%
0
0
0
0
0
0
0
0
0
0
90
SCC100%
0
0
0
0
0
0
0
0
0
0
90
MRG[MW]
27
28
29
30
31
32
33
34
35
36
sum
SC0100%
80
110
215
140
225
150
180
250
215
250
2405
SCA100%
30
48
67
81
170
122
140
237
227
235
1447
SCB100%
30
48
67
81
170
122
140
237
227
235
1447
SCC100%
30
48
67
81
170
122
140
237
227
235
1447
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300
250
200
SC0100%
SCA100%
150
SCB100%
100
SCC100%
50
0
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Figure 3.6.34Must-run generation (Lurio generation off, 100% load)
3.6.1.2 Short Circuit Study Results
The short circuit current analyses of three different scenarios are as follows:
1)
400kV Namialo substation is source of Namialo-Metoro T/L, hence, it is merely affected by the change
in NamialoMetoro T/Ls(Figure 3.5.4, ~3.5.5).
2)
For 110kV bus at 220/110kV Metoro substation, the short circuit current becomes 4.1~6.6 times and
5.3~8.5 times the original short circuit current for 220kV and 400kV step up, respectively. Therefore,
the capacity of current relays may need to be increased (Figure 3.5.6 and 3.5.7).
3)
The short circuit currents of other substations (Pemba, Macomia, Mosimbua) remained within 1.1 times
its original short circuit current values, hence, the capacity of current relays do not have to be changed
(Figure 3.5.8 and 3.5.9).
3.6.1.3 Transfer Capability
There is much limitation to applying N-1 reliability standard to the Northern Mozambique power system.
Therefore, the transfer capability has been calculated using N-0 criterion, and only outages of equipment related
to Namialo-Metoro T/L has been considered.
Table 3.6.40. Transfer Capability for three scenarios
Reliability
Standard
No parallel
T/L
Scenario A
ScenarioB
ScenarioC
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N-0
N-1
N-0
N-1
N-0
N-1
N-0
Thermal
Capacity [MVA]
77
316
792
1377
Voltage Stability Transfer Capacity(N-0/N1)
2018
2021
2026
2031
2036
0
88
43
157
106
185
0
105
0
112
44
170
0
119
0
94
0
89
0
93
0
93
0
105
170
93
109
ATC
[MVA]
89
93
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N-1
N-M
Demand
62
59
65
50.7
77.3
87.2
101.6
118.4
3.6.1.3.1 Transfer Capacity Analysis applying N-0 reliability standard
200
150
118,4
100
87,2
77,3
50
시나리오 A
시나리오 B
101,6
시나리오 C
N-M Demand
50,7
0
2018
2021
2026
2031
2036
Figure 3.6.35. Demand and Available transfer capability
The relation between transfer capability and demand for Namialo-Metoro interconnection is shown in Figure
3.6.5, when N-0 standard is applied. As shown, transfer capacity decreases as load level increases, and is the
greatest in Scenario C. The load exceeds transfer capacity around 2031, requiring the operation of must-run
generations.
3.6.1.3.2 Transfer Capacity Analysis using N-1 Reliability Standard
In order to apply N-1 reliability standard, the failure probability of each component within the system is
required. Since this data could not be obtained N-1 standard could not be applied. However, if Namialo-Metoro
T/L is constructed and operated in 400kV, it has been identified that the system could withstand certain outages
of system components, which was not possible in case of Scenario A. This result shows that the system
reliability can be improved if 400kV backbone in extended to Metoro substation. Furthermore, 400kV T/L
construction and operation has greater amount of transfer capacity compared to 220kV operation.
3.6.2 Benefit of the Interconnection with Tanzanian Power system
3.6.2.1 Overview of Tanzanian Power System
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Figure 3.6.36
System(2002)
Network
Figure 3.6.37 Number of Customers Connected
(Source
:
TANESCO
OVERVIEW,
FelchesmiMramba, 14-Aug-2015)
Tanzania is the country which is next to the North border of Mozambique, and its power system is operated by
TANESCO(Tanzania Electric Supply Company). The population of Tanzania is 49.6 million, and 38% of the
population is supplied with electricity. Furthermore, there are 1,501,162 households (2015. 6. 30), and the
annual power usage of each household is 101kWh/year. Recently, the electrification of Tanzania has reached
23%~38% annually, due to Tanzanian government and international cooperation and support.
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Figure 3.6.38 Master Plan of TANESCO
The master plan of Tanzanian system, until 2035, is shown in Figure 3.6.20. In 2015, total generation capacity
was 1250MW (Hydro 45%, gas 35.3%, liquid oil 19.4%, SPP 0.3%), with the peak load of 934.62MW. An
independent grid is located in the South with the generation capacity of 73.77MW, and peak load of 48.58MW.
The power consumption in 2014 was 6000GWh, and although the load growth rate compared to the previous
year was 5%, the annual average load growth rate was estimated to be between 8% and 15% in the master plan.
The transmission system uses voltage levels of 220kV, 132kV, and 66kV, where 220kV is mainly used, and the
distribution network is composed with 33kV, 11kV, and 400V/230V low voltage lines.
The power network of TANESCO is constantly expanding, and according to the master plan, 400kV network
will be the main power transmission line in the future. The 400kV transmission line is planned to be expanded to
Mtwara, which is very close to the North border of Mozambique, and is planned to be interconnected with
Mozambique to exchange power (220kV T/L, 100MW capacity).
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Table 3.6.41 Participation in Power Trading (source : Master Plan of TANESCO, page 45)
3.6.2.2 Benefit of Interconnection between Mozambique and Tanzania
Selecting the best scenario for Namialo-Metoro T/L construction depends on the procurement of transfer
capacity, to supply the loads connected to Metoro substation, and T/L losses. However, even though the 400kV
backbone transmission network has been constructed in the Northern transmission system, the transfer capacity
is still very limited due to 1300km of distance between the source and load.
However, if new generations located near the east coast (Palma ENI, NacalaVelha), system loss can be reduced,
transfer capacity can be increased, and the system can be operated more securely and reliably. If the Tanzania
transmission network follows the master plan, 400kV T/Ls can be used to exchange power between Tanzania
and Mozambique, which can be seen as another power source to supply the loads in Metoro area. Furthermore,
this interconnection will increase the reliability of the system, and Northern Mozambique system may then be
able to satisfy N-1 reliability standard. Therefore, 400kV T/L construction may be more beneficial due to greater
transfer capacity, compared to 220kV T/L, in this respect.
3.6.3 Feasible Solution for Namialo-Metoro Transmission upgrade
In this section, the construction of T/L between Namialo and Metoro for different scenarios has been analyzed
for 100% and 110kV load levels, and for the case of generations not following the construction and operation
schedule.
As a result, SCC (400kV T/L construction) displayed the best characteristics compared to other two scenarios.
However, when 110% load levels were considered, SCC showed a low level of losses after 2022, which may be
due to high level of reactive power exchange on 400kV T/L. Therefore, it is better to operate the T/L on 220kV,
during low load levels.
In addition, SCC displayed better transfer capacity than other scenarios; however, must-run generations have to
be operated after 2031. Therefore, considering all the technicalities, and for minimum loss and maximum
transfer capacity, 400kV T/L should be constructed, and operated on 220kV until 2022, and stepped up to 400kV
after 2022.
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4. Conclusion
This study has been conducted in order to identify the most adequate T/L construction scenario between 400kV Namialo and 110kV
Metorosubstations in order to provide a secure and reliably power to the fast growing areas in Northern Mozambique, Pemba, Macomia, and
Ausse until 2036.
The considered scenarios are:

Scenario 0: No T/L construction (Increasing load levels only served by current 110kV T/L)

Scenario A: Constructing 220kV T/L and operating it in parallel with current 110kV T/L.

Scenario B: In order to account for future expansion of the transmission system and the tie-line interchange with other African
countries, constructing 400kV T/L and operating on 220kV until the load growth is manageable.

Scenario C: Constructing and operating the T/L with 400kV.
Power flow, voltage stability transfer capability, and fault analysis was conducted for each scenario in order to:

Identify whether the system is capable of serving the load in each scenario

Identify potential problems and security concerns in the system, and if there are any factors that jeopardize system security

Calculate the power losses and the capacities of must-run generations for economic evaluation
4.1 Results
The main generation used to supply power to Metoro substation comes from the hydro and thermal power generations, which are located
more than 1000km away from the load area. Due to the length of the transmission, the T/L losses amount to almost 60% of the supplied
power. On the other hand, if new generations, which are constructed near the load, are used to supply the load, it may significantly reduce
the transmission losses.
After analyzing the three different scenarios, Scenenario A, 220kV T/L construction and operation, Scenario B, 400kV T/L construction and
220kV operation, and Scenario C, 400kV construction and operation, the results show that it is optimal to construct the Namialo-Metoro T/L
as 400kV T/L, and operate it on 220kV until 2023, then step up the voltage to 400kV after 2023. However, must-run generators have to be
operated after 2031 for all three scenarios due to insufficient transfer capacity. The economic value of must run generators should be taken
into account in future feasibility studies.
Furthermore, after analyzing the system losses throughout the project period (2018~2036), the results show that Scenario C is able to reduce
system losses by 939GWh and Namialo-Metoro T/L losses by 82.3GWh compared to Scenario A, in 100% load levels. In 110% load levels,
Scenario C reduced system losses by 682GWh and Namialo-Metoro T/L losses by 46.2GWh, compared to Scenario A. Lastly, if Lurio hydro
plant (must-run generation) is assumed to be out of service throughout the project period, Scenario C is able to save 1372GWh of system
losses and 275GWh of Namialo-Metoro T/L losses compared to Scenario A.
The operation of must-run generations has significant effect on system security for Northern power system operation. In 100% load levels,
must-run generation have to be operated since 2027 and since 2020 for 110% load levels even if Lurio is assumed to be operating. If Lurio
plant is out of service, NacalaVelha generation must be operated since 2021 in Scenario A for stable system operation.
Constructing the T/L between Namialo and Metoro as 400kV T/L provides another advantage as the Northern system may be interconnected
with the Tanzanian power system, which can increase the system security, stability, and reliability. Also, 400kV T/L will serve as the core
network of renewable energy source integration in Africa, promoting energy source and industrial development.
Inception Report
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ELECTRICIDADE DE MOÇAMBIQUE
BYUCKSAN POWER CO.,LTD.
CONSULTANCY SERVICES FOR PACKAGE-1 FEASIBILITY STUDY FOR THE 220kV
INTERCONNECTION NAMIALO - METORO
References
[1] “Technical Assistance to Strengthen EDM’s Capacity for Investment and Network Development Planning - Master Plan Update Project,
2012 - 2027 -Volume 1–Final System Review Report”, 2013-04-15
[2] “Technical Assistance to Strengthen EDM’s Capacity for Investment and Network Development Planning, Master Plan Update Project,
2012 – 2027” , Draft Final Master Plan Update Report, Volume II - Load Forecast Report, Norconsult, 2013-04-15
[3] “Chimuara - Nacala Transmission Project Feasibility Study”, Volume II:
Norconsult , May 2013
Load Forecast, Final Report - Assignment no.: 5009957
[4] Gilberto Mahumane, Peter Mulder e David Nadaud, “Energy outlook for Mozambique 2012-2030 LEAP-based scenarios for energy
demand and power Generation”, IESE conference paper n 16, 4~5 September 2012
[5] “Mozambique Regional Transmission Backbone Project (“CESUL”): Technical & Economic Feasibility Study”, Presentation of
Feasibility Study Report, CESUL Launch Workshop, Centro de Conferências Joaquim Chissano, Maputo, 24 November 2011
[6] Judy W.Chang, et.el,
July 2013.
“The benefits of Electric Transmission : Identifying and Analyzing the Value of Investments”, The Brattle Group,
[7] EDM Annual Report 2014, Electricidade De Mocambique
[8] Statistical Summary 2012, ,Electricidade De Mocambique
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