XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TRANSMISSION/GENERATION FEASIBILITY STUDY SHORT CIRCUIT ANALYSIS

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1 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 El Paso Electric Company

2 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 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 El Paso Electric Company

3 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: Z 1 = J per unit (100 MVA base) EPE determined an estimated zero sequence impedance, based on standard construction and spacing, of: Z 0 = J 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) = J per unit (100 MVA base) Z (steam turbine) = J per unit (100 MVA base) The new generators have the following reactance values on the generator MVA base: Gas Turbines: X d = Direct Axis Synchronous Reactance = 1.90 per unit X d = Direct Axis Transient Reactance = per unit X d = Direct Axis Subtransient Reactance = per unit Steam Turbines: X d = Direct Axis Synchronous Reactance = 2.13 per unit X d = Direct Axis Transient Reactance = per unit X d = Direct Axis Subtransient Reactance = 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 El Paso Electric Company

4 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 El Paso Electric Company

5 circuit breakers, along with the interruption rating, at each of the pertinent substations: Breaker Breaker Interruption Substation Voltage Number Rating (Amps) Arroyo B 40, B 40, B 40, B 40, B 40, B 40, B 40,000 Diablo B 40, B 40, B 40,000 Hidalgo , , , ,000 Luna , , , , , , , , ,000 Newman B 40, B 40, B 40, B 40,000 Breaker Breaker Interruption Substation Voltage Number Rating (Amps) Diablo B 40, B 40, B 40, B 40,000 Short Circuit Analysis for a 5 El Paso Electric Company

6 B 40, B 31,500 Luna , , ,000 Mimbres , , , , ,500 Newman , , , N , , , N , , N , , , N , , , N , , N , N , , N , N , ,000 Breaker Breaker Interruption Substation Voltage Number Rating (Amps) Newman 115 N , N ,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 El Paso Electric Company

7 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: 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 5, ,128.8 Diablo 345 kv Bus 4, ,717.5 Hidalgo 345 kv Bus 6, ,257.9 Luna 345 kv Bus 7, ,549.0 Newman 345 kv Bus 6, ,611.6 Diablo 115 kv Bus 17, ,958.5 Luna115 kv Bus 8, ,863.7 Mimbres 115 kv Bus 7, ,583.6 Newman 115 kv Bus 22, , 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, ,268.0 Diablo 345 kv Bus 4, ,091.3 Hidalgo 345kV Bus 5, ,077.5 Luna 345 kv Bus 6, ,790.3 Newman 345 kv Bus 6, ,698.1 Diablo 115 kv Bus 17, ,305.3 Luna 115 kv Bus 9, ,624.9 Mimbres 115 kv Bus 7, ,836.5 Newman 115 kv Bus 26, ,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 El Paso Electric Company

8 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 Luna- Newman 345 kv line is less than the minimum interruption rating of any effected existing circuit breaker: Short Circuit Analysis for a 8 El Paso Electric Company

9 Maximum Fault Current With 6 XXXX Generators and new generation on Minimum Circuit Breaker Luna-Newman 345 kv line Substation Interruption Rating (Amps) (Amps) Arroyo 345 kv 40,000 6,128.8 Diablo 345 kv 40,000 6,717.5 Hidalgo 345 kv 40,000 7,257.9 Luna 345 kv 40,000 14,790.3 Newman 345 kv 40,000 8,698.1 Diablo 115 kv 31,500 20,305.3 Luna 115 kv 40,000 11,624.9 Mimbres 115 kv 17,500 8,836.5 Newman 115 kv 40,000 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 El Paso Electric Company

10 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: Title: Dennis H. Malone Supervisor, System Planning Signature: Dennis H. Malone Company: El Paso Electric Company Date: September 11, 2001 Short Circuit Analysis for a 10 El Paso Electric Company