Short Circuit Analysis
with New Generation
Proposed by
XXXXXXXXXXXXXXXXXXXXXX
Pursuant to a
Transmission and Facilities Study
Requested by
XXXXXXXXXXXXXXXXXXXXXX
Study Performed by El Paso Electric Company
System Planning Section
January 2001
Short Circuit Analysis with Generation Proposed by XXXXXXXXXXXXXXXXX pursuant to a
Transmission and Facilities Study Requested by XXXXXXXXXXXXXXXXXXXXXX (XXXXX)
January 2001
Short Circuit Analysis with New Generation
Connected to EPE’s Newman 115 kV Bus
I.
Introduction
El Paso Electric Company (EPE) has agreed to perform a Transmission and
Facilities Study, for XXXXXXXXXXXXXXXXXXXXXXXXXXXXX (XXXXX), with
regard to the construction and interconnection of 500 MW of new generation (two
250 MW generators) at EPE’s Newman 115 kV bus. The powerflow and stability
analysis of this study is also being performed by EPE.
When generation is added to a system, the available fault current of that system
increases. Therefore, a study has been performed to determine if EPE’s existing
substation circuit breakers in the substations electrically near the new generation
have adequate short circuit interruption duties.
II.
Short Circuit Study
The new generation proposed by XXXXX is sited, as per XXXXX, just south of
EPE’s Newman Power Plant. The interconnection to the existing EPE
transmission system is EPE’s Newman 115 kV Substation bus through a XXXXX
115 kV Switchyard and four (4) 115 kV circuits of approximately 2500 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= 0.00002571 + J0.00023722 per unit (100 MVA base)
EPE determined an estimated zero sequence impedance, based on standard
construction and spacing, of:
Z0 = 0.00022195 + J0.00079049 per unit (100 MVA base)
The generators will be connected to the 115 kV transmission system through two
(2) 330 MVA, 21/115 kV step-up transformers, with rated short circuit
impedances of 15% each at a 330 MVA base. These impedances were modeled
in the short circuit analysis as:
Z = 0.00090 + J0.04545 per unit (100 MVA base)
The new generators is defined as 270 MVA each with the following reactance
values on the generator MVA base:
Xd = Direct Axis Synchronous Reactance = 1.95 per unit
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Short Circuit Analysis with Generation Proposed by XXXXXXXXXXXXXXXXXXXX pursuant to a
Transmission and Facilities Study Requested by XXXXXXXXXXXXXXXXXXXXXXXXXX (XXXXX)
January 2001
X’d = Direct Axis Transient Reactance = 0.200 per unit
X’’d = Direct Axis Subtransient Reactance = 0.150 per unit
These reactance values were converted to a 100 MVA base and used to model
the new generators in the short circuit study.
Maximum fault currents were then determined at the Newman 345 kV and the
Newman 115 kV buses, and the substations immediately connected to Newman:
Arroyo 345 kV
Luna 345 kV
Butterfield 115 kV
Cromo 115 kV
Shearman 115 kV
Caliente 345 kV
AAP 115 kV
Chaparral 115 kV
Milagro 115 kV
Vista 115 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 by EPE at the 345 kV and 115 kV vary between the
substations. The following is a list of the existing circuit breakers, along with the
interruption rating, at each of the pertinent substations:
Substation
Newman
Newman
Breaker
Voltage
345
345
345
345
Breaker
Number
2448B
6018B
8378B
0538B
115
115
115
115
115
115
115
115
115
11950
11101
15601
N-115-1
11951
11401
N-115-7
11957
N-115-8
Interruption
Rating (Amps)
40,000
40,000
40,000
40,000
40,000
50,000
40,000
40,000
40,000
40,000
43,000
43,000
43,000
3
Short Circuit Analysis with Generation Proposed by XXXXXXXXXXXXXXXXXXXX pursuant to a
Transmission and Facilities Study Requested by XXXXXXXXXXXXXXXXXXXXXXXXXX (XXXXX)
January 2001
Substation
Newman
Breaker
Voltage
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
Breaker
Number
N-115-2
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
N-115-24
Interruption
Rating (Amps)
40,000
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
40,000
Arroyo
345
345
345
345
345
345
345
2418B
2458B
4348B
3018B
5428B
7548B
2098B
40,000
40,000
40,000
40,000
40,000
40,000
40,000
Caliente
345
345
345
345
345
1828B
3928B
0428B
4178B
4688B
40,000
40,000
50,000
40,000
40,000
Luna
345
345
345
345
345
345
345
345
01982
02182
03082
09682
08582
10682
11782
15082
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
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Short Circuit Analysis with Generation Proposed by XXXXXXXXXXXXXXXXXXXX pursuant to a
Transmission and Facilities Study Requested by XXXXXXXXXXXXXXXXXXXXXXXXXX (XXXXX)
January 2001
Breaker
Voltage
115
Breaker
Number
4806B
Butterfield
115
115
115
115
0796B
2236B
5386B
6936B
Chaparral
115
Cromo
115
115
115
115
0306B
0596B
0766B
0666B
40,000
40,000
40,000
40,000
Milagro
115
11602
25,000
Shearman
115
115
115
0136B
3126B
2486B
22,000
22,000
22,000
Vista
115
115
115
115
115
115
3656B
0106B
4426B
6256B
5186B
7026B
25,000
40,000
40,000
25,000
25,000
25,000
Substation
AAP
Interruption
Rating (Amps)
40,000
20,000
40,000
31,500
31,500
No Circuit Breakers at this Substation
The short circuit analysis was first performed with no new generation. This gave
the “base case” fault duties of the circuit breakers. Then the two new generators
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 EPE system. The short circuit (fault) currents for each case at all
of the possibly impacted substations are:
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Short Circuit Analysis with Generation Proposed by XXXXXXXXXXXXXXXXXXXX pursuant to a
Transmission and Facilities Study Requested by XXXXXXXXXXXXXXXXXXXXXXXXXX (XXXXX)
January 2001
Three Phase Line to Ground:
Substation Faulted
Newman 345 kV Bus
Newman 115 kV Bus
Arroyo 345 kV Bus
Caliente 345 kV Bus
Luna 345 kV Bus
AAP 115 kV Bus
Butterfield 115 kV Bus
Chaparral 115 kV Bus
Cromo 115 kV Bus
Milagro 115 kV Bus
Shearman 115 kV Bus
Vista 115 kV Bus
No XXXXX Generators With 2 XXXXX Generators
Fault Current (Amps)
Fault Current (Amps)
6,568.9
7,634.5
22,202.8
31,519.1
5,227.2
5,762.6
5,259.7
5,933.7
7,193.6
7,587.1
10,099.7
11,096.1
11,203.5
11,988.8
13,072.1
15,736.5
16,247.4
17,617.9
9,629.6
11,475.9
10,553.6
12,225.6
12,361.7
13,572.9
Single Phase Line to Ground:
Substation Faulted
Newman 345 kV Bus
Newman 115 kV Bus
Arroyo 345 kV Bus
Caliente 345 kV Bus
Luna 345 kV Bus
AAP 115 kV Bus
Butterfield 115 kV Bus
Chaparral 115 kV Bus
Cromo 115 kV Bus
Milagro 115 kV Bus
Shearman 115 kV Bus
Vista 115 kV Bus
No XXXXX Generators With 2 XXXXX Generators
Fault Current (Amps)
Fault Current (Amps)
6,884.0
7815.4
26,617.6
37,746.4
4,735.2
5,052.8
5,381.2
5,870.1
6,110.2
6,301.4
7,449.5
7,852.3
8,376.9
8,671.4
10,875.2
12,295.3
15,580.8
16,411.7
7,684.7
8,713.4
7,963.1
8,810.8
11,199.0
11,855.6
Comparing these fault currents to the appropriate existing circuit breaker
interruption ratings shows that the interconnection of the new generators at
EPE’s Newman 115 kV Substation, in the configuration and parameters as given
by XXXXX, will not cause any existing circuit breaker to operate outside its
design rating.
6
Short Circuit Analysis with Generation Proposed by XXXXXXXXXXXXXXXXXXXX pursuant to a
Transmission and Facilities Study Requested by XXXXXXXXXXXXXXXXXXXXXXXXXX (XXXXX)
January 2001
IV. Results and Conclusions
A short circuit study was performed on the EPE system comparing the maximum
fault current on the system at various substations: Newman Substation (both 345
kV and 115 kV) and each substation directly connected to Newman, both with
and without the two new generators proposed by XXXXX. The results of this
study show that the maximum fault current with the two new generators is less
than the minimum interruption rating of any effected existing circuit breaker:
Substation
Newman 345 kV
Newman 115 kV
Arroyo 345 kV
Caliente 345 kV
Luna 345 kV
AAP 115 kV
Butterfield 115 kV
Cromo 115 kV
Milagro 115 kV
Shearman 115 kV
Vista 115 kV
Minimum Circuit Breaker
Interruption Rating (Amps)
40,000
40,000
40,000
40,000
40,000
40,000
20,000
40,000
25,000
22,000
25,000
Maximum
Fault Current with 2
New Generators (Amps)
7,815.4
37,746.4
5,762.6
5,870.1
7,587.1
11,096.1
11,988.8
17,617.9
11,475.9
12,225.6
13,572.9
Therefore, the operation of the two new generators with the parameters as given
by XXXXX connected to EPE’s Newman 115 kV bus will not cause any existing
circuit breaker to operate outside its interruption rating limit.
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Short Circuit Analysis with Generation Proposed by XXXXXXXXXXXXXXXXXXXX pursuant to a
Transmission and Facilities Study Requested by XXXXXXXXXXXXXXXXXXXXXXXXXX (XXXXX)
January 2001
V. Certification
This Short Circuit Analysis was performed pursuant to the Agreement for a
Transmission and Facilities Study, dated December 8, 1999 requested by
XXXXX. The generator, step-up transformer and new transmission line
parameters were supplied by XXXXX. The Short Circuit Analysis was performed
by El Paso Electric Company.
Name:
Dennis H. Malone
Title:
Supervisor, System Planning
Signature:
Dennis H. Malone
Date:
February 8, 2001
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Short Circuit Analysis with Generation Proposed by XXXXXXXXXXXXXXXXXXXX pursuant to a
Transmission and Facilities Study Requested by XXXXXXXXXXXXXXXXXXXXXXXXXX (XXXXX)
January 2001