XXXXXXXXXXXXXXXXXXXX GENERATION INTERCONNECTION FACILITIES STUDY SHORT CIRCUIT ANALYSIS FOR PROPOSED GENERATION AT NEWMAN 115 kv BUS

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1 XXXXXXXXXXXXXXXXXXXX GENERATION INTERCONNECTION FACILITIES STUDY SHORT CIRCUIT ANALYSIS FOR PROPOSED GENERATION AT NEWMAN 115 kv BUS El Paso Electric Company System Operations Department System Planning Section May 2003

2 I. INTRODUCTION XXXXXXXXXXXXXXXXXXXXXXXXXXX (XXX) has proposed the addition of a generating plant near EPE s Newman Substation. This proposed generation unit was analyzed in two phases. Phase I analyzed a 140 MW combustion turbine (CT) in Phase II analyzed a steam turbine integrated with the CT to form a Combined Cycle (CC) unit in In both phases, the unit was modeled as being interconnected at EPE s Newman 115 kv bus. When generating units are added to a transmission system, the available fault current on a system increases. Therefore, as part of the Generation Interconnection Facilities Study (GIFS), a short circuit study was performed to determine if the additional fault current on the EPE system due to the proposed generation does not exceed the interruption ratings of EPE s existing substation circuit breakers. In the powerflow analysis of the GIFS, the 2006 CT was modeled at a 140 MW generation output level. The 2009 CC unit was modeled at a 290 MW maximum generation output level. This Short Circuit Study was performed by El Paso Electric Company s Transmission & Distribution Division (EPE T&D). The Powerflow, Q-V, and Stability analyses for this study are also being performed by El Paso Electric Company s Transmission & Distribution Division (EPE T&D) and will be issued under a separate cover. Short Circuit Analysis for a 1 El Paso Electric Company

3 II. SHORT CIRCUIT STUDY MODELING The new generation proposed by XXX is sited at EPE s Newman 115 kv substation. The combustion and steam-turbine generator portion of the proposed combined-cycle plant will be connected to the 115 kv transmission through a 200 MVA, 18/115 kv step-up transformer per generator. Each of the two step-up transformers has an impedance of 7.5 % on a 120 MVA base. The step-up transformer impedance modeled in the short circuit analysis for both step-up transformers was: Z (step-up) = J per unit (100 MVA base) The new generators have the following reactance values on the generator MVA base: Combustion-Turbine: X d = Direct Axis Synchronous Reactance = per unit X d = Direct Axis Transient Reactance = per unit X d = Direct Axis Subtransient Reactance = per unit Steam-Turbine: X d = Direct Axis Synchronous Reactance = 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. In addition to the new generation connected to the Newman 115 kv bus, one existing and four potential generation projects were also modeled in the analysis. These generation projects included the following: 135 MW of generation at Afton Substation interconnected to the Luna-Afton- Newman 345 kv line (existing). 614 MW of generation interconnected at the Luna 345 kv Substation. 160 MW of generation interconnected near Lordsburg, New Mexico. 150 MW of generation interconnected at Lordsburg, New Mexico. 130 MW of new generation interconnected at Afton 345 kv Substation and 14 MW of additional generation on the existing Afton generator. These additional generators were modeled in the study to provide a worst case scenario in the event that all are interconnected into EPE s system before the proposed Newman generation is interconnected. Short Circuit Analysis for a 2 El Paso Electric Company

4 Maximum fault currents were then determined at the Newman 115 kv bus and other EPE substations of interest or importance. These included the following: Diablo 345 kv Diablo 115 kv Newman 345 kv Rio Grande 115 kv Rio Grande 69 kv The resulting fault current was then compared to the circuit breaker interruption ratings of the breakers at each of the above mentioned substations. Among the proposed projects listed above is the addition of 14 MW of generation to the existing 135 MW generator at Afton. This existing generator will be combined with a proposed 130 MW generator and interconnected to the Luna-Afton-Newman 345 kv line. Together, these projects (135 MW +14 MW MW) represent a combinedcycle configuration with a modeled output of 279 MW. Because there are two transmission line interconnection configurations for this proposed project that are currently being studied as part of a different analysis, the results for this Short-Circuit Study will be presented in two different result groups. The Transmission Configuration 1 used to interconnect the 279 MW generation plant mentioned above involves the use of the existing Luna-Afton-Newman 345 kv transmission configuration. The existing Afton generator interconnects the Luna- Newman 345 kv line to now form two line segments, the Luna-Afton 345 kv line and the Afton to Newman 345 kv. In Transmission Configuration 2, EPE s Luna-Diablo 345 kv line is routed such that this existing line will be tied to Afton 345 kv substation to also form two line segments, the Luna-Afton 345 kv line and the Afton-Diablo 345 kv line Ultimately, a Study of the proposed Afton Project, currently in progress, will be used to determine which Transmission Configuration will be used to interconnect the 279 MW project described above. Because the study referenced above has not yet been completed, results of this Short- Circuit Study will be divided into two groups corresponding to each of the two Transmission Configurations described above. Short Circuit Analysis for a 3 El Paso Electric Company

5 III. RESULTS OF THE SHORT CIRCUIT ANALYSIS The circuit breakers used in the Southern New Mexico System at 345 kv, 115 kv, and 69 kv buses vary between the substations. The following is a list of the existing circuit breakers, along with the interruption rating, at each of the relevant substations: Breaker Breaker Interruption Substation Voltage Number Rating (Amps) Diablo B 40, B 40, B 40,000 Diablo B 40, B 40, B 40, B 40, B 40, B 31,500 Newman B 40, B 40, B 40, B 40,000 Newman , , , N , , , N , , N , , , N , , , N , , N , N ,000 Short Circuit Analysis for a 4 El Paso Electric Company

6 Breaker Breaker Interruption Substation Voltage Number Rating (Amps) Newman ,000 (continued) 115 N , N , , N , N ,000 Rio Grande B 40,000* B 23, B 23, B 40, B 40, B 23, B 23, B 40, B 40,000* B 23, B 23, B 40,000 Rio Grande ,000* , , , , , , , B 31, , , B 31, , ,000 * Currently these breakers have ratings ranging between 19,000-20,000 amperes. They are expected to be replaced with breakers having 40,000 ampere ratings as part of EPE s normal breaker replacement program. Short Circuit Analysis for a 5 El Paso Electric Company

7 The short circuit analysis was first performed with no new generation at Newman 115 kv (all other potential generation projects in). This gave the base case fault duties of the circuit breakers. The new generation at Newman 115 kv was then modeled in two phases. Phase I analyzed a 140 MW combustion turbine (CT) in Phase II analyzed a steam-turbine added to the combustion turbine configuration to form a Combined Cycle (CC) unit in In both phases the short circuit study was then reanalyzed (with all other potential generation projects in). The incremental between the three studies gave the impact of the new generators on the existing circuit breakers in the Southern New Mexico system. A. Short Circuit Results for Proposed New Generation at Newman 115 kv Using Transmission Configuration 1 Transmission Configuration 1 assumes that the transmission configuration of interconnecting the Afton generating station to the Luna-Afton-Newman 345 kv line will remain as it exists now, with the line divided into two segments: 1) Luna to Afton 345 kv substation 2) Afton to Newman 345 kv substation. The other proposed projects previously listed are also included in this configuration. The short circuit (fault) currents of Configuration 1 at all the substations which may be impacted due to the addition of the proposed Newman 5 project are listed below: No New Generation at Newman 115 kv Bus Versus Phase 1 CT Addition at Newman 115 kv Bus in 2006 Three Phase Line to Ground: No New Generation With New Generation Diablo 345 kv Bus 5, ,498.0 Diablo 115 kv Bus 19, ,070.0 Newman 345 kv Bus 8, ,348.0 Newman 115 kv Bus 25, ,755.0 Rio Grande 115 kv Bus 21, ,845.0 Rio Grande 69 kv Bus 19, ,051.0 Short Circuit Analysis for a 6 El Paso Electric Company

8 Single Phase Line to Ground: No New Generation With New Generation Diablo 345 kv Bus 4, ,958.0 Diablo 115 kv Bus 19, ,820.0 Newman 345 kv Bus 8, ,396.0 Newman 115 kv Bus 30, ,063.0 Rio Grande 115 kv Bus 22, ,373.0 Rio Grande 69 kv Bus 23, ,518.0 No New Generation at Newman 115 kv Bus Versus Phase 2 CC Plant at Newman 115 kv Bus in 2009 Three Phase Line to Ground: No New Generation With New Generation Diablo 345 kv Bus 5, ,562.0 Diablo 115 kv Bus 19, ,323.0 Newman 345 kv Bus 8, ,746.0 Newman 115 kv Bus 25, ,695.0 Rio Grande 115 kv Bus 21, ,430.0 Rio Grande 69 kv Bus 19, ,308.0 Single Phase Line to Ground: No New Generation With New Generation Diablo 345 kv Bus 4, ,992.0 Diablo 115 kv Bus 19, ,231.0 Newman 345 kv Bus 8, ,738.0 Newman 115 kv Bus 30, ,787.0 Rio Grande 115 kv Bus 22, ,819.0 Rio Grande 69 kv Bus 23, ,753.0 Short Circuit Analysis for a 7 El Paso Electric Company

9 As can be seen in the table below, the fault currents of six (6) existing circuit breakers at Rio Grande 115 kv exceed their interruption ratings during a single phase line to ground fault in SUBSTATION BREAKER NUMBER INTERRUPTION RATING SC FAULT CURRENT W/O NEWMAN 5 SC FAULT CURRENT WITH NEWMAN 5 Rio Grande B 23,000 22,818 23, B 23,000 22,818 23, B 23,000 22,818 23, B 23,000 22,818 23, B 23,000 22,818 23, B 23,000 22,818 23,373 Therefore, under Transmission Configuration 1, XXX will be responsible for the cost of replacing six new circuit breakers at the Rio Grande 115 kv bus. B. Short Circuit Results for Proposed New Generation at Newman 115 kv Using Transmission Configuration 2 Transmission Configuration 2 assumes that the transmission configuration of interconnecting the Afton generating station to the Luna-Afton-Newman 345 kv line will remain as it exists now, with the line divided into two segments: 1) Luna to Afton 345 kv substation 2) Afton to Newman 345 kv substation. However, this Configuration also interconnects the Afton plant to EPE s Luna-Diablo 345 kv line, also dividing the line into two segments, 1) Luna to Afton 345 kv substation 2) Afton to Diablo 345 kv substation. The other proposed projects previously listed are also included in this configuration. The short circuit (fault) currents under Configuration 2 at all the substations which may be impacted due to the addition of the proposed Newman 5 project are listed on the following page. Short Circuit Analysis for a 8 El Paso Electric Company

10 No New Generation at Newman 115 kv Bus Versus Phase 1 CT Addition at Newman 115 kv Bus in 2006 Three Phase Line to Ground: No New Generation With New Generation Diablo 345 kv Bus 7, ,876.0 Diablo 115 kv Bus 21, ,759.0 Newman 345 kv Bus 9, ,791.0 Newman 115 kv Bus 25, ,783.0 Rio Grande 115 kv Bus 22, ,019.0 Rio Grande 69 kv Bus 20, ,441.0 Single Phase Line to Ground: No New Generation With New Generation Diablo 345 kv Bus 6, ,025.0 Diablo 115 kv Bus 21, ,823.0 Newman 345 kv Bus 9, ,727.0 Newman 115 kv Bus 30, ,097.0 Rio Grande 115 kv Bus 23, ,549.0 Rio Grande 69 kv Bus 23, ,935.0 No New Generation at Newman 115 kv Bus Versus Phase 2 CC Plant at Newman 115 kv Bus in 2009 Three Phase Line to Ground: No New Generation With New Generation Diablo 345 kv Bus 7, ,022.0 Diablo 115 kv Bus 21, ,323.0 Newman 345 kv Bus 9, ,217.0 Newman 115 kv Bus 25, ,723.0 Rio Grande 115 kv Bus 22, ,692.0 Rio Grande 69 kv Bus 20, ,717.0 Single Phase Line to Ground: Short Circuit Analysis for a 9 El Paso Electric Company

11 No New Generation With New Generation Diablo 345 kv Bus 6, ,103.0 Diablo 115 kv Bus 21, ,231.0 Newman 345 kv Bus 9, ,086.0 Newman 115 kv Bus 30, ,821.0 Rio Grande 115 kv Bus 23, ,059.0 Rio Grande 69 kv Bus 23, ,186.0 As can be seen in the table below, the fault currents of six (6) existing circuit breakers at Rio Grande 115 kv exceed their interruption ratings during a single phase line to ground fault in These circuit breakers will have to be replaced due to the increased shortcircuit current resulting from the addition of another proposed project in Therefore, XXX is not responsible for the replacement of these breakers. BREAKER NUMBER INTERRUPTION RATING SC FAULT CURRENT W/O NEWMAN 5 SC FAULT CURRENT WITH NEWMAN 5 Rio Grande B 23,000 23,916 24, B 23,000 23,916 24, B 23,000 23,916 24, B 23,000 23,916 24, B 23,000 23,916 24, B 23,000 23,916 24,549 However, in the 2009 case, the fault current to at the Rio Grande 115 kv bus exceeds the interruption rating of one (1) existing circuit breaker. The table below shows that the overloading of this breaker is due to the addition of the proposed Newman 5 project. INTERRUPTION RATING SC FAULT CURRENT W/O NEWMAN 5 SC FAULT CURRENT WITH NEWMAN 5 SUBSTATION BREAKER NUMBER Rio Grande ,000 23,616 24,186 Therefore, under Transmission Configuration 2, XXX will be responsible for the cost of replacing one new circuit breaker at the Rio Grande 69 kv bus. Short Circuit Analysis for a 10 El Paso Electric Company

12 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 115 kv Substation and selected substations in the EPE system, both with and without the new generation proposed at Newman 115 kv. In addition, two transmission configurations were analyzed to model potential interconnections involving the interconnection of an additional 144 MW of proposed generation at the existing Afton Substation. Transmission Configuration 1 assumes that the transmission configuration of the Luna- Afton-Newman 345 kv line remains as it exists now, with the line divided into two segments 1) Luna to Afton 345 kv substation 2) Afton to Newman 345 kv substation. Transmission Configuration 2 assumes that the Afton substation is interconnected to the Luna-Afton-Newman 345 kv line as it is in Configuration 1 and it is also tied in to the Luna-Diablo 345 kv line as follows 1) Luna to Afton 345 kv substation 2) Afton to Diablo 345 kv substation Ultimately, a Study for the proposed Afton project that is currently in progress will determine which transmission configuration will be used to interconnect the additional 144 MW of the potential generation to the EPE system. The tables below show the results of the short circuit analyses for Transmission Configuration 1 and Transmission Configuration 2. A. Short Circuit Results for Proposed New Generation at Newman 115 kv Using Transmission Configuration 1 Maximum Fault Current With Proposed Minimum Circuit Breaker Generation Addition Substation Interruption Rating (Amps) (Amps) Diablo 345 kv Bus 40, ,562.0 Diablo 115 kv Bus 31, ,323.0 Newman 345 kv Bus 40, ,746.0 Newman 115 kv Bus 40, ,787.0 Rio Grande 115 kv Bus* 23, ,819.0 Rio Grande 69 kv Bus* 24, ,753.0 Short Circuit Analysis for a 11 El Paso Electric Company

13 Results of the analysis for Transmission Configuration 1 indicate that the fault current at the Rio Grande 115 kv bus for a single line-to-ground fault exceeded the breaker interruption rating of six existing breakers. From the list of circuit breakers at the Rio Grande 115 kv bus on page 5, the maximum fault current at this bus for a single line-toground fault exceeded the 23,000 ampere interruption rating of six breakers. This was due to the addition of the proposed CT at Newman 115 kv bus in Therefore, the addition of new generation at the Newman 115 kv bus in 2006 will require that six existing circuit breakers at the Rio Grande 115 kv Substation with 23,000 amp ratings be replaced with six new breakers with higher breaker interruption ratings in B. Short Circuit Results for Proposed New Generation at Newman 115 kv Using Transmission Configuration 2 Maximum Fault Current With proposed Minimum Circuit Breaker Generation Addition Substation Interruption Rating (Amps) (Amps) Diablo 345 kv Bus 40, ,022.0 Diablo 115 kv Bus 31, ,323.0 Newman 345 kv Bus 40, ,217.0 Newman 115 kv Bus 40, ,821.0 Rio Grande 115 kv Bus* 23, ,059.0 Rio Grande 69 kv Bus* 24, ,186.0 Results of the analysis for Transmission Configuration 2 indicate that fault currents for a single line-to-ground fault exceeded breaker interruption rating of six existing breakers at the Rio Grande 115 kv bus and one breaker at the Rio Grande 69 kv bus. From the list of circuit breakers at the Rio Grande 115 kv bus on page 5, the maximum fault current for a single line-to-ground fault exceeded the 23,000 ampere interruption rating of six breakers. In Transmission Configuration 2, the fault current exceeded 23,000 amps for a single line-to-ground fault due to the addition of proposed generation interconnected at the existing Afton Substation as modeled in this short circuit analysis in This potential project occurs in the study queue prior to the addition of new generation at the Newman 115 kv bus. Therefore, under this transmission configuration, the owner of this proposed project is responsible for the cost of replacing the six existing 23,000 amp circuit breakers at Rio Grande 115 kv Substation. However, the list of circuit breaker ratings at the Rio Grande 69 kv bus on page 6 indicates that the maximum fault current at this bus for a single line-to-ground fault exceeded the 24,000 amp circuit breaker interruption rating of one existing circuit breaker due to the addition of the proposed new generation at the Newman 115 kv bus in Therefore, under this configuration, XXX is responsible for the cost of replacing one 69 kv breaker at the Rio Grande 69 kv bus with a circuit breaker with an interruption rating above 24,000 amps in Short Circuit Analysis for a 12 El Paso Electric Company

14 The estimated costs to replace the breakers XXX will be responsible under each of the configurations analyzed are shown below: XXX ESTIMATED COSTS FOR BREAKER REPLACEMENT UNDER TRANSMISSION CONFIGURATION 1 SUBSTATION BREAKER NUMBER YEAR ESTIMATED COST (2003$) Rio Grande B 2006 $60, B 2006 $60, B 2006 $60, B 2006 $60, B 2006 $60, B 2006 $60,000 TOTAL XXX BREAKER REPLACEMENT COSTS $360,000 XXX ESTIMATED COSTS FOR BREAKER REPLACEMENT UNDER TRANSMISSION CONFIGURATION 2 SUBSTATION BREAKER NUMBER YEAR ESTIMATED COST (2003$) Rio Grande $40,000 TOTAL XXX BREAKER REPLACEMENT COSTS $40,000 Short Circuit Analysis for a 13 El Paso Electric Company

15 V. Certification This Short Circuit Analysis was performed pursuant with a Generation Interconnection Facilities Study requested by XXXXXXXXXXXXXXXXXXXXXXXXXXXX (XXX). The generator, step-up transformer and new transmission line parameters were supplied by XXX. The Short Circuit Analysis was performed by El Paso Electric Company s Transmission & Distribution Division (EPE T&D). Name: Title: Dennis H. Malone Manager, System Planning Signature: Dennis H. Malone Company: El Paso Electric Company Date: Short Circuit Analysis for a 14 El Paso Electric Company