XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
TRANSMISSION/GENERATION FEASIBILITY STUDY
SHORT CIRCUIT ANALYSIS
El Paso Electric Company
System Operations Department
System Planning Section
September 2001
Short Circuit Analysis for a
1
Transmission/Generation Feasibility Study
Requested by XXXXXXXXXXXXXXX (XXXX)
El Paso Electric Company
September 2001
I.
INTRODUCTION
El Paso Electric Company (EPE) has agreed to perform a
Transmission/Generation Feasibility Study for XXXXXXXXXXXXXXXXXXXXXX
(XXXX) with regard to the construction and interconnection of 1227.8 MW of new
XXXX generation (four gas turbines and two steam turbines in two combined
cycle arrangement) at the Luna 345 kV bus. When generation is added to a
system, the available fault current of that system increases. Therefore, a study,
called a short circuit study, has been performed to determine if the Southern New
Mexico existing substation circuit breakers in the substations electrically near the
new generation have adequate short circuit interruption duties. This report and
this part of the analysis consists of the short circuit study. The powerflow and
stability analysis of this study is being performed by EPE and will be issued under
a separate cover.
II.
SHORT CIRCUIT STUDY MODELING
Short Circuit Analysis for a
2
Transmission/Generation Feasibility Study
Requested by XXXXXXXXXXXXXXX (XXXX)
El Paso Electric Company
September 2001
The new generation proposed by XXXX is sited near the Luna 345 kV substation
and will be interconnected to the Luna 345 kV Substation bus through two 345
kV circuits (one for each combined cycle generating unit) of approximately 3200
feet in length consisting of 954 kCmil 45/7 ACSR “Rail”, 2-conductor bundles per
phase. The positive sequence impedance of each of these lines is:
Z1= 0.00003 + J0.00031 per unit (100 MVA base)
EPE determined an estimated zero sequence impedance, based on standard
construction and spacing, of:
Z0 = 0.00026 + J0.00105 per unit (100 MVA base)
The generators will be connected to the 345 kV transmission through a 193 MVA
and a 308 MVA, 18/345 kV step-up transformer, for each of the gas turbines and
and each of the steam turbines, respectively. The step-up transformers have
impedances of 10 % on a 116 MVA and 185 MVA for each of the gas turbine and
the steam turbine step-up transformer, respectively. These impedances were
modeled in the short circuit analysis as:
Z(gas turbines) = 0.00212 + J0.086181 per unit (100 MVA base)
Z (steam turbine) = 0.001329 + J0.054038 per unit (100 MVA base)
The new generators have the following reactance values on the generator MVA
base:
Gas Turbines:
Xd = Direct Axis Synchronous Reactance = 1.90 per unit
X’d = Direct Axis Transient Reactance = 0.286 per unit
X’’d = Direct Axis Subtransient Reactance = 0.203 per unit
Steam Turbines:
Xd = Direct Axis Synchronous Reactance = 2.13 per unit
X’d = Direct Axis Transient Reactance = 0.321 per unit
X’’d = Direct Axis Subtransient Reactance = 0.227 per unit
These reactance values were converted to a 100 MVA base and used to model
the new generators in the short circuit study.
Short Circuit Analysis for a
3
Transmission/Generation Feasibility Study
Requested by XXXXXXXXXXXXXXX (XXXX)
El Paso Electric Company
September 2001
In addition to the new XXXX generation, one other viable generation project that
was added in the analysis. This generation project was:
•
225 MW of new generation interconnected at on EPE’s Luna-Newman 345 kV
line
These additional generators were modeled in the study to provide a “worst case”
scenario in the event that they are interconnected into EPE’s system before the
XXXX generation is interconnected.
Maximum fault currents were then determined at the Luna 345 kV and the Luna
115 kV buses, and the substations immediately connected to Luna:
Arroyo 345 kV
Diablo 115 kV
Mimbres 115 kV
Newman 115 kV
Diablo 345 kV
Hidalgo 345 kV
Newman 345 kV
The resulting fault current was then compared to the circuit breaker interruption
ratings of the breakers at each of the above mentioned substations.
III.
RESULTS OF THE SHORT CIRCUIT ANALYSIS
The circuit breakers used in the Southern New Mexico System at 345 kV and
115 kV buses vary between the substations. The following is a list of the existing
Short Circuit Analysis for a
4
Transmission/Generation Feasibility Study
Requested by XXXXXXXXXXXXXXX (XXXX)
El Paso Electric Company
September 2001
circuit breakers, along with the interruption rating, at each of the pertinent
substations:
Breaker
Substation
Arroyo
Breaker
Voltage
345
345
345
345
345
345
345
Number
2418B
2458B
4348B
3018B
5428B
7548B
2098B
Diablo
345
345
345
1888B
2138B
2258B
40,000
40,000
40,000
Hidalgo
345
345
345
345
09782
04982
02782
03882
40,000
40,000
40,000
40,000
Luna
345
345
345
345
345
345
345
345
345
01982
03082
04182
07482
09682
08582
10682
11782
15082
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
Newman
345
345
345
345
2448B
6018B
8378B
0538B
40,000
40,000
40,000
40,000
Breaker
Voltage
115
115
115
115
Breaker
Number
1586B
1636B
1706B
1806B
Substation
Diablo
Short Circuit Analysis for a
5
Transmission/Generation Feasibility Study
Requested by XXXXXXXXXXXXXXX (XXXX)
Interruption
Rating (Amps)
40,000
40,000
40,000
40,000
40,000
40,000
40,000
Interruption
Rating (Amps)
40,000
40,000
40,000
40,000
El Paso Electric Company
September 2001
115
115
2876B
4326B
40,000
31,500
Luna
115
115
115
32162
34362
33262
20,000
20,000
20,000
Mimbres
115
115
115
115
115
10662
12862
13962
14062
15162
17,500
22,000
22,000
17,500
17,500
Newman
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
Breaker
Voltage
115
115
Breaker
Substation
Newman
11950
11101
15601
N-115-1
11951
11401
N-115-7
11957
N-115-8
11952
11601
N-115-3
11953
15501
N-115-19
11967
N-115-20
N-115-21
11968
N-115-22
N-115-23
11969
Number
N-115-24
N-115-2
40,000
50,000
40,000
40,000
40,000
40,000
43,000
43,000
43,000
40,000
50,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
Interruption
Rating (Amps)
40,000
40,000
The short circuit analysis was first performed with no new generation. This gave
the “base case” fault duties of the circuit breakers. Then the six new XXXX
generators and the viable 225 MW generation on the Luna-Newman 345 kV line
Short Circuit Analysis for a
6
Transmission/Generation Feasibility Study
Requested by XXXXXXXXXXXXXXX (XXXX)
El Paso Electric Company
September 2001
were modeled and the short circuit study was re-run. The incremental between
these two studies gave the impact of the new generators on the existing circuit
breakers in the Southern New Mexico system. The short circuit (fault) currents
for each case at all of the possibly impacted substations are:
Three Phase Line to Ground:
Substation Faulted
Arroyo 345 kV Bus
Diablo 345 kV Bus
Hidalgo 345 kV Bus
Luna 345 kV Bus
Newman 345 kV Bus
Diablo 115 kV Bus
Luna115 kV Bus
Mimbres 115 kV Bus
Newman 115 kV Bus
No XXXX Generators
Fault Current (Amps)
5,227.2
4,599.6
6,402.1
7,193.6
6,568.9
17,088.8
8,521.3
7,580.1
22,202.8
With 6 XXXX Generators
and new generation on
Luna-Newman 345 kV line
Fault Current (Amps)
6,128.8
6,717.5
7,257.9
13,549.0
8,611.6
19,958.5
9,863.7
8,583.6
24, 916.0
Single Phase Line to Ground:
With 6 XXXX Generators
and new generation on
No XXXX Generators Luna-Newman 345 kV line
Substation Faulted
Fault Current (Amps)
Fault Current (Amps)
Arroyo 345 kV Bus
4,735.2
5,268.0
Diablo 345 kV Bus
4,364.5
6,091.3
Hidalgo 345kV Bus
5,193.6
6,077.5
Luna 345 kV Bus
6,110.2
14,790.3
Newman 345 kV Bus
6,884.0
8,698.1
Diablo 115 kV Bus
17,624.5
20,305.3
Luna 115 kV Bus
9,884.7
11,624.9
Mimbres 115 kV Bus
7,861.1
8,836.5
Newman 115 kV Bus
26,617.6
29,397.6
Comparing these fault currents to the appropriate existing circuit breaker
interruption ratings shows that the interconnection of the new generators at the
Luna 345 kV Substation, in the configuration and parameters as given by XXXX,
will not cause any existing circuit breaker to operate outside its design rating.
Short Circuit Analysis for a
7
Transmission/Generation Feasibility Study
Requested by XXXXXXXXXXXXXXX (XXXX)
El Paso Electric Company
September 2001
IV. Results and Conclusions
A short circuit study was performed on the Southern New Mexico system
comparing the maximum fault current on the system at various substations: Luna
Substation (both 345 kV and 115 kV) and each substation directly connected to
Luna, both with and without the six new generators proposed by XXXX and the
225 MW of new proposed generation on the Luna-Newman 345 kV line. The
results of this study show that the maximum fault current with six new generators
proposed by XXXX and the 225 MW of new proposed generation on the LunaNewman 345 kV line is less than the minimum interruption rating of any effected
existing circuit breaker:
Short Circuit Analysis for a
8
Transmission/Generation Feasibility Study
Requested by XXXXXXXXXXXXXXX (XXXX)
El Paso Electric Company
September 2001
Substation
Arroyo 345 kV
Diablo 345 kV
Hidalgo 345 kV
Luna 345 kV
Newman 345 kV
Diablo 115 kV
Luna 115 kV
Mimbres 115 kV
Newman 115 kV
Minimum Circuit Breaker
Interruption Rating (Amps)
40,000
40,000
40,000
40,000
40,000
31,500
40,000
17,500
40,000
Maximum Fault Current
With 6 XXXX Generators
and new generation on
Luna-Newman 345 kV line
(Amps)
6,128.8
6,717.5
7,257.9
14,790.3
8,698.1
20,305.3
11,624.9
8,836.5
29,397.6
Therefore, the operation of six new generators proposed by XXXX with the
parameters as given by XXXX connected to the Luna 345 kV bus and the 225
MW of new proposed generation on the Luna-Newman 345 kV line will not cause
any existing circuit breaker to operate outside its interruption rating limit.
Short Circuit Analysis for a
9
Transmission/Generation Feasibility Study
Requested by XXXXXXXXXXXXXXX (XXXX)
El Paso Electric Company
September 2001
V. Certification
This Short Circuit Analysis was performed pursuant with a
Transmission/Generation Feasibility Study requested by
XXXXXXXXXXXXXXXXXXXXXXX. The generator, step-up transformer and new
transmission line parameters were supplied by XXXXXXXXXXXXXXXXXXXXX.
The Short Circuit Analysis was performed by El Paso Electric Company.
Name:
Dennis H. Malone
Title:
Supervisor, System Planning
Signature:
Dennis H. Malone
Company: El Paso Electric Company
Date:
September 11, 2001
Short Circuit Analysis for a
10
Transmission/Generation Feasibility Study
Requested by XXXXXXXXXXXXXXX (XXXX)
El Paso Electric Company
September 2001