Study for various contingencies in Telangana –Seemandhra in view
of the agitation
The agitation w.r.t Telangana-Seemandhra split has taken a serious
turn with almost all generation in Seemandhra affected. Mob attacks
on various 400/220/132 kV Stations especially feeding the traction
loads have adversely impacted the security of the Southern Grid. The
attacks are random and impact many Substations at a time. A study
was conducted to assess the impact of various scenarios based on
our recent experience.
1. Introduction:The installed capacity of Seemandhra and Telangana are as
shown below:Area
Telangana
Seemandhra
Hydro
2174
1515
Thermal
2283
3810
Central
2600
1000
Gas/Naptha
IPP
IPP(OA)
272
2759 966
Total
7056
10322
17378
(all Figs in MW)
Typical demand break-up is Telangana 4700 MW and
Seemandhra 4300 MW.
The average day time demand for AP as a whole normally
would be around 8000-10,000 MW considering no gas
generation in Vemagiri complex.
The details of 400 and 220 kV Stations in these areas are as
shown:Area
400 KV SS
220 KV SS
Telangana
Seemandhra
11
9
37
51
The snapshots of the grid showing the Telangana, Rayalaseema
and Coastal AP are attached in Annexure-1.
2. Summary of the Studies conducted:ID
Study Conducted
Description of the study
1
Coastal Threat
Exhibit-1
2
Rayalaseema
Threat
Exhibit-2
3
East Coast threat
Exhibit-3
4
Seemandhra entire
Exhibit-4
5
Worst Case
scenario
Seemandhra
Exhibit-5
Study for impact of outage of Coastal 220 kV and AP 400
/220 kV SS- Ongole, Sulurpeta, Podili, Paruchuru,
Narasaraopeta, Markapur, Gunadala, VTS and
Tadikonda, Nunna SS out. Loads affected 1000 MW
Study for impact of outage of Rayalaseema 220 kV and
AP 400 /220 kV SS- Chittor 400/220 kV, Chinakampalli,
Cuddapah, Gooty, Dhone, Anathpur, Ramgir, Hindupur,
Muddanur, Koduru, Rajampet, Regulupadu, Pulivendula,
Kalyandurg, Yerraguntla, Nannor, APC, SYZ Palli,
Mydukur, Kambalapadu SS out. Loads affected 1600 MW
Study for impact of outage of East Coast Stations at
Vizag, Garividi, Tekkali, Kalpaka 400/220 Kv, Pendurthi,
Dairy Farm, Parawada, Kakinada, Bommuru, VGTS1 and
2.. Loads affected 1030 MW
Outage of all AP owned assets in Seemandhra including
generation. Central Sector assets and Private Assets
spared. This scenario details the aspects of leveraging
the HVDC B2B Station at Gazuwaka to evacuate Simhadri
Generation to SR Grid via NEW Grid and Talcher-Kolar
HVDC Link. Loads affected 4100 MW
Outage of all APTRANSCO, IPP and Central Sector lines
and SS. Impact of entire Seemandhra collapsing. This
study also details the amount of import that can be
absorbed safely from NEW Grid at Bhadrawathi and the
evacuation scenario for all Generating Assets in
Telangana and the limitations. . Loads affected 4100 MW
3. Study details:a. Coastal Threat:AP Demand:Imports:- Gazuwaka 500 MW, Bhadrawathi 1000 MW, Kolar
2000 MW.
Generation in AP:- Hydro- Nagarjunasagar 800 MW, Srisailam
Left Bank 700 MW, Sileru Complex 250 MW,
Thermal- Simhadri Complex 1400 MW, Ramagundam 2000
MW, KTS Complex 1400 MW, Bhoopalapalli 360 MW.
Major Generation affected:- VTS Complex, Rayalaseema,
Srisailam Right Bank. Vemagiri Gas assumed as NIL generation
due to paucity of fuel.
Study conducted for impact of outage of Coastal 220 kV and AP
400 /220 kV SS- Ongole, Sulurpeta, Podili, Paruchuru,
Narasaraopeta, Markapur, Gunadala, VTS, Nellore, Nunna and
Tadikonda SS out. Loads affected 1000 MW.
Observations: Traction on Jolarapettai- Vizag route would be affected.
Sulurupeta 220 kV can be fed from Gummidipoondi SS of
TN.
 Voltages at Nellore, Nunna and Vemagiri would be high,
depending on load profile. All Bus and Line reactors would
need to be in service. The following lines(one Circuit) can
be opened as per order
o 400 kV Gooty-NPS1
o 400 kV Gooty-NPS2
o 400 kV VTS-Malkaram-1
o 400 kV Khammam-Mamidapalli
o 400 kV Kalpaka-Khammam
o 400 kV Vijayawada-Nellore (provided Ʃ of flow is less
than 1000 MW)
o As 220 kV Nunna and VTS bus (vital buses) is
assumed as out the flow on 220 kV lines to be
watched. Sileru Complex generation may have to be
regulated.
o The 400 kV Lines at the following SS would be vital.
Nunna, Gazuwaka, Simhadri, Vemagiri and Kalpaka.
These Stations have to be safeguarded from security
viewpoint
 Flows on 400 kV ensure that the threat is manageable.
 Hydro generation may have to be reduced by about 8001000 MW . However, it is prudent to keep machines on
bar in Synchronous condenser mode.
b. Rayalaseema Threat:-
AP Demand:Imports:- Gazuwaka 500 MW, Bhadrawathi 1000 MW, Kolar
2000 MW.
Generation in AP:- Hydro- Nagarjunasagar 800 MW, Srisailam
Left Bank 700 MW, Sileru Complex 250 MW,
Thermal- Simhadri Complex 1400 MW, Ramagundam 2000
MW, KTS Complex 1400 MW, Bhoopalapalli 360 MW.
Major Generation affected:- VTS Complex, Rayalaseema,
Srisailam Right Bank. Vemagiri Gas assumed as NIL generation
due to paucity of fuel.
Study for impact of outage of Rayalaseema 220 kV and AP 400
/220 kV SS- Chittor 400/220 kV, Chinakampalli, Cuddapah,
Gooty, Dhone, Anathpur, Ramgir, Hindupur, Muddanur,
Koduru, Rajampet, Regulupadu, Pulivendula, Kalyandurg,
Yerraguntla, Nannoor, AP Carbides, SYZ Palli, Mydukur,
Kambalapadu SS out. Loads affected 1600 MW
Observations: Traction on Guntakal route would be affected. Part of
Chitoor loads can be fed from Thiruvalam 230 kV SS of TN
and extended upto the traction station at Renigunta
 Anchoring at Chinakampalli, Gooty 400 kV SS would be
lost. Voltages may fluctuate depending on line flows.
Voltages at Nellore, Nunna and Vemagiri would be high,
depending on load profile. All Bus and Line reactors would
need to be in service. The following lines(one Circuit) can
be opened as per order
o 400 kV Gooty-NPS1
o 400 kV Gooty-NPS2
o 400 kV N’Sagar-Cuddapah
o 400 kV Raichur-Gooty
 Hydro generation at Nagarjunasagar, Srisailam LB and
Sileru complex may have to be scaled down by about 500600 MW. However, it is prudent to keep machines on bar
in Synchronous condenser mode wherever possible. The
imports at Gazuwaka and Bhadrawathi may also be scaled
down or shifted to Talcher-Kolar link if margins are
available.
 400 KV Stations and lines at Chinakampalli and Gooty
needs to be safeguarded as they are vital links for
connecting the AP System to TN and Karnataka Grid.
c. East Coast Threat:AP Demand:- 9000 MW
Imports:- Gazuwaka 500 MW, Bhadrawathi 1000 MW, Kolar
2000 MW.
Generation in AP:- Hydro- Nagarjunasagar 800 MW, Srisailam
Left Bank 700 MW, Sileru Complex 250 MW,
Thermal- Simhadri Complex 1400 MW, Ramagundam 2000
MW, KTS Complex 1400 MW, Bhoopalapalli 360 MW.
Major Generation affected:- VTS Complex, Rayalaseema,
Srisailam Right Bank. Vemagiri Gas assumed as NIL generation
due to paucity of fuel.
Study for impact of outage of Vizag, Garividi, Tekkali, Kalpaka
and Vemagiri 400/220 Kv, Pendurthi, Dairy Farm, Parawada,
Kakinada, Bommuru, VGTS1 and 2. Sileru complex generation
has been assumed as the plant is remote and not easily
accessible.
Observations: Traction on Howrah route would be affected. Supply from
Lower Sileru to Bommur needs to be extended for
normalising part of traction loads.
 Supply to Ports would be affected.
 Vishakapattinam Steel Plant would be islanded with its
loads and Captive generation.
 As both Vemagiri and Kalpaka Stations are assumed to be
out along with the lines, the major issue would be the
evacuation of Simhadri Power as only one 400 kV
link(Gazuwaka-Nunna) is available in this scenario for
evacuating both Simhadri and Gazuwaka power.
Gazuwaka HVDC station has to be reversed to export
about 400-600 MW depending on the ER Grid position
and margins available at Talcher Kolar HVDC link.
Accordingly Simhadri generation must be brought down
to oil support technical minimum.
 400/220 kV Stations at Gazuwaka, Kalpaka, Simhadri and
Vemagiri are critical in this scenario.
 Voltages at Gazuwaka and Nunna would tend to vary.
d. Loss of entire Seemandhra- APTRANSCO Assets:AP Demand:- 9000 MW
Imports:- Gazuwaka 500 MW, Bhadrawathi 1000 MW, Kolar
2000 MW.
Generation in AP:- Hydro- Nagarjunasagar 800 MW, Srisailam
Left Bank 700 MW, Sileru Complex 250 MW,
Thermal- Simhadri Complex 1400 MW, Ramagundam 2000
MW, KTS Complex 1400 MW, Bhoopalapalli 360 MW.
Major Generation affected:- VTS Complex, Rayalaseema,
Srisailam Right Bank. Vemagiri Gas assumed as NIL generation
due to paucity of fuel.
Outage of all AP owned assets in Seemandhra including
generation. Central Sector assets and Private Assets spared.
This scenario details the aspects of leveraging the HVDC B2B
Station at Gazuwaka to evacuate Simhadri Generation to SR
Grid via NEW Grid and Talcher-Kolar HVDC Link as detailed in
the scenario above
e. Loss of entire Seemandhra- all Assets- Worst case
scenario:AP Demand:- 9000 MW
Imports:- Gazuwaka 500 MW, Bhadrawathi 1000 MW, Kolar
2000 MW.
Generation in AP:- Hydro- Nagarjunasagar 800 MW, Srisailam
Left Bank 700 MW, Sileru Complex 250 MW,
Thermal- Simhadri Complex 1400 MW, Ramagundam 2000
MW, KTS Complex 1400 MW, Bhoopalapalli 360 MW.
Major Generation affected:- VTS Complex, Rayalaseema,
Srisailam Right Bank. Vemagiri Gas assumed as NIL generation
due to paucity of fuel.
This scenario details the entire Seemandhra going dark.
Simhadri station and Gazuwaka would also be out. All
400/220/132 kV SS in Seemandhra is taken out. The objective is
to rescue the Metro and Generators at Ramagundam, KTS and
Bhoopalapalli with Telangana loads.
Observations: Traction on all routes passing through AP would be
affected
 Surplus generation/import of about 1700 MW needs to
be dealt with by minimising import on HVDC Bhadrawathi
and hydro stations. Evacuation is through a single 400 kV
line( N’Sagar-Mehboobnagar-Raichur).
 This scenario can be dealt with by reducing flow on HVDC
B2B at Bhadrawathi and converting the links to AC by
operating the Bypass and tripping the N’Sagar-MBNRaichur link. This way the Telangana area can be reliably
connected to NEW Grid till situation improves. Flow on AC
link could be controlled by flexing hydro/load shedding.
4. Conclusions:As per the studies conducted it can be seen that most threats can
be dealt with reliably. However, the loss of entire Seemandhra
with all stations would pose a severe threat to the Southern Grid
where part of the Grid (about 5500 MW) would be lost. Telangana
Grid would be with WR and rest of SR Grid needs to survive on
internal resources and the import at Kolar of about 2000 MW.
Traction and important loads would be severely affected
especially in Seemandhra area. It is therefore paramount to
enhance physical security at all 400 kV Stations to preserve the
integrity of the Grid. The summary of the impact severity and the
actions to be taken are summarised in the tables below
ID
Study Conducted
Impact Severity
1
Coastal Threat
Moderate to severe. Manageable
2
3
Rayalaseema
Threat
East Coast threat
4
Seemandhra entire
5
Worst Case
scenario
Seemandhra
Severe. Manageable with changes in load-generation
balance
Severe. Manageable with changes in load-generation
balance
Very severe. Large areas would be affected. Severely
reduced reliability. Manageable for short periods
Extremely severe. Large areas and vital installations
would be affected. May also lead to widespread
disturbance in SR Grid.
Actions to be taken
ID
Study
Conducted
Action items
1
Coastal Threat
Voltage and line flows to be watched
Traction restoration from TN source.
Hydro reduction of about 800-1000 MW
Following lines to be opened in the order for controlling High
Voltages:-
o
o
o
o
o
o
2
Rayalaseema
Threat
3
East Coast
threat
4
Seemandhra
entire
5
Worst Case
scenario
Seemandhra
400 kV Gooty-NPS1
400 kV Gooty-NPS2
400 kV VTS-Malkaram-1
400 kV Khammam-Mamidapalli
400 kV Kalpaka-Khammam
400 kV Vijayawada-Nellore (provided Ʃ of flow is less than
1000 MW)
Voltage and line flows to be watched
Traction restoration from TN source.
Hydro reduction of about 500-600 MW
HVDC import from NEW grid at BVT and GZK to be shifted to
Talcher-Kolar if margins permit. Following lines to be opened in
the order for controlling High Voltages:o
400 kV Gooty-NPS1
o
400 kV Gooty-NPS2
o
400 kV N’Sagar-Cuddapah
o
400 kV Raichur-Gooty
Traction restoration from Hydro. HVDC at Gazuwaka to export to
ER of about 400-600 MW. Simhadri Units generation reduction to
Technical minimum(oil Support).No N-1 for Simhadri evacuation
VSP would be islanded with its CPP
Traction restoration from Hydro. HVDC at Gazuwaka to export to
ER of about 400-600 MW. Simhadri Units generation reduction to
Technical minimum(oil Support)
).No N-1 for Simhadri evacuation. VSP would be islanded with its
CPP.Following lines to be opened in the order for controlling High
Voltages:o
400 kV Gooty-NPS1
o
400 kV Gooty-NPS2
o
400 kV VTS-Malkaram-1
o
400 kV Khammam-Mamidapalli
o
400 kV Srisailam-Mamidapalli
o
400 kV Vijayawada-Nellore (provided Ʃ of flow is less than
1000 MW)
Bypass to AC mode at Bhadrawathi. Telangana and Ramagundam
to be with NEW Grid. Telengana Hydro to be reduced. Restoration
to be made at earliest