Kcpl Transmission Planning

IATAN 2 SUPPLEMENTAL INTERCONNECTION STUDY

TRANSMISSION PLANNING

JUNE 27, 2005

KCPL Transmission Planning Iatan 2 Supplemental Interconnection Study

KCPL TRANSMISSION PLANNING

Iatan 2 Supplemental Interconnection Study

Introduction:

Transmission Planning was assigned the task of studying additional interconnection options for the proposed Iatan 2 generator, which would rely as much as possible on existing transmission line right-of-ways or on new right-of-way adjoining existing right-of-way. This strategy has been proposed to limit the environmental impact of new transmission line construction. The study involved identifying possible transmission line routes for integrating the Iatan 2 generation into the existing transmission system. A contingency analysis of the surrounding transmission system with the identified transmission facilities added was performed to determine if the proposed additions met reliability standards. This document summarizes the preliminary results of this study.

Transmission Expansion Plans:

Three transmission expansion plans were identified which utilized existing transmission right-of-ways as much as possible. These plans are described below.

1. Plan I2A – Build new 345kV transmission line from Iatan, in southeast direction, to nearest point on Aquila’s Stranger Creek – Platte City 161kV transmission line (approximately 4 miles). Use existing right-of-way for new double circuit 345&161kV transmission lines to Platte City (approximately 12 miles). Continue new double circuit 345&161kV transmission lines easterly along Aquila’s Platte City – Smithville 161kV right-of-way (approximately 8 miles). Build new 345kV switching station (3 breaker ring bus) at Smithville to tie new Iatan – Smithville 345kV line into existing Hawthorn – St. Joseph 345kV line. Total length of new 345kV line is approximately 25 miles. This option is similar to the one studied by the Southwest Power Pool (SPP) for interconnection of the Iatan 2 generation.

1. Plan I2B – Install new 345/161kV transformer (550 Mva) at Iatan. Build new 161kV double circuit transmission lines from Iatan, in southeast direction, to nearest point on Aquila’s Stranger Creek – Platte City 161kV transmission line (approximately 5 miles). Cut Stranger Creek – Platte City line and tie into new Iatan lines so that there would be a Stranger Creek – Iatan 161kV line and an Iatan – Platte City 161kV line. Total length of new 161kV lines is approximately 8 miles (4 miles each). This option requires the least amount of new transmission line construction.

1. Plan I2C – Build new 345kV transmission line from Iatan, in northeast direction, along the existing Iatan – St. Joseph 345kV line to Sparta (where Iatan – St. Joseph crosses Nashua – Lake Road line, approximately 16 miles). Build new double circuit 345&161kV transmission lines to Nashua from Sparta using existing right-of-way (approximately 27 miles). Build new 345kV switching station (3 breaker ring bus) at Nashua to tie new Iatan – Nashua 345kV line into existing Hawthorn – St. Joseph 345kV line. Total length of new 345kV line is approximately 43 miles. This option utilizes only KCPL transmission line right-of-way.

Study Methodology:

The study was performed using the SPP 2010 summer peak loadflow model from the 2005-loadflow model series. This model included all SPP confirmed long-term firm transmission service reservations and transmission service rollover obligations along with a West to East transmission flow bias. Iatan 2 generation was modeled at 900 Mw net, with 500 Mw dispatched to KCPL native load and the remaining 400 Mw to the rest of the eastern interconnection (model swing bus).

PTI’s PSSE loadflow analysis software was used for this study. The ACC function of the PSSE software was used to analyze the transmission system of KCPL and surrounding utilities under normal and contingency conditions to assess the performance of the proposed transmission additions.

Transmission lines (>100kV) were monitored in the following systems; KCPL, Westar, Aquila (MPS only, includes SJLP), BPU-KCK, Independence, and AECI (tie lines only). The analysis contingency list included the same single and multiple contingencies used in KCPL summer/winter operating studies. The following criterion was used to assess transmission system performance in the monitored area;

Normal conditions: all line flows within RATE A (normal) limits

all voltages at load busses within +/- 5% of nominal

Contingency conditions: all line flows within RATE B (emergency) limits

all voltages at load busses within +/- 5% of nominal

Base Case Analysis:

ACC analysis was performed on the base case loadflow model before Iatan 2 generation was added in to identify any pre-existing criteria violations. The base case did not have any criteria violations in the monitored area under normal conditions. The following KCPL lines were overloaded for various contingencies in the base case loadflow model. Adjustments were made to fix these lines to increase their normal/emergency ratings in the loadflow model;

Stilwell-Bucyrus, replaced wavetrap, increased ratings to 293/335 Mva

Southtown-Bendix, replaced wavetrap, increased ratings to 293/335 Mva

Tomahawk-Bendix, replaced small conductor, increased ratings to 293/335 Mva

Southtown-MPS Martin City, replaced wavetrap, increased ratings to 293/335 Mva.

The following KCPL base case contingency criteria violations are known conditions, which are mitigated by operating guides (operator manual actions). No adjustments were made in the loadflow model for these criteria violations;

Olathe-Switzer line overload for loss of Brookridge-Overland Park line

Brookridge-Overland Park line overload for loss of Olathe-Switzer line

East District low voltages for contingencies along South Waverly to Salisbury lines

The following base case contingency criteria violations exist in utilities bordering on KCPL’s transmission system. No adjustments were made in the loadflow model for these violations, as any mitigation would require consultation with those utilities;

Westar’s Jarbalo-166th Street-Jaggard 115kV line overload for various contingencies

Aquila’s Martin City-Turner Road 161kV line overload for a KCPL common right-of-way multiple contingency (Stilwell-Redel & Stilwell-Hickman).

Analysis of Iatan 2 Generation Addition:

The base case loadflow model was modified with the addition of the Iatan 2 generator at 900 Mw net at the Iatan 345kV bus. Iatan 1 generation was at 683 Mw. The following generation adjustments were made to the loadflow model to accommodate the Iatan 2 addition.

KCPL Northeast generation (8 units) decreased 400 Mw

KCPL Osawatomie generation (2 units) decreased 100 Mw

TVA Brown’s Ferry 3 generation (1 unit) decreased 345 Mw (model swing bus)

ACC analysis was performed on this case loadflow model to identify criteria violations due to adding the Iatan 2 generation. The following line was overloaded for normal conditions;

Westar’s Jarbalo-166th Street 115kV line was overloaded approximately 8%.

The following additional criteria violations were identified for contingency conditions;

Aquila’s Iatan-St Joe 345kV line overloaded 63% for loss of Iatan-Stranger Creek

Iatan-Stranger Creek 345kV line overloaded 34% for loss of Iatan-St Joe

Nashua-Lake Road 161kV line overloaded 25% for loss of Iatan-Stranger Creek

As this line has overcurrent relaying this criteria violation is not valid.

Small (<5%) overloads on Craig-College & Craig-Lenexa for KCPL multiple contingencies.

Analysis of Transmission Plan I2A:

The base case with Iatan 2 loadflow model was modified with the addition of the Iatan–Smithville 345kV line and a 345kV bus at Smithville tapped into the Hawthorn-St. Joseph 345kV line. ACC analysis was performed on this case loadflow model to determine if criteria violations identified due to adding the Iatan 2 generation were mitigated by these facility additions. This case did not have any criteria violations in the monitored area under normal conditions.

The following criteria violation continues to exist in the I2A plan case for contingency conditions;

Small (<2%) overload of Nashua-Lake Road 161kV line for loss of Hawthorn-Smithville

As this line has overcurrent relaying this criteria violation is not valid.

No other criteria violations not previously identified in the base case loadflow model exist in the I2A plan case.

Analysis of Transmission Plan I2B:

The base case with Iatan 2 loadflow model was modified with the addition of a 345/161kV transformer at Iatan and new line construction to tie the Platte City–Stranger Creek 161kV line into the Iatan 161kV bus. ACC analysis was performed on this case loadflow model to determine if criteria violations identified due to adding the Iatan 2 generation were mitigated by the transmission facility additions. The following line was overloaded for normal conditions;

Westar’s Jarbalo-166th Street 115kV line was overloaded approximately 5%.

The following criteria violation continues to exist in the I2B plan case for contingency conditions;

Aquila’s Iatan-St Joe 345kV line overloaded 5% for loss of Iatan-Stranger Creek

The following additional new criteria violations were identified in the I2B plan for contingency conditions;

Iatan-Platte City 161kV line overloaded 41% for loss of Iatan-St Joe

Aquila’s Platte City-Smithville 161kV line overloaded 15% for loss of Iatan-St Joe

Aquila’s Smithville-Nashua 161kV line overloaded 7% for loss of Iatan-St Joe

KCPL’s Iatan 345/161kV transformer overloaded 4% for loss of Iatan-Stranger Creek

Small (<2%) overload on Greenwood-Merriam for KCPL multiple contingencies.

Small (<3%) overloads on some Westar 115kV facilities in Northeast Kansas.

Analysis of Transmission Plan I2C:

The base case with Iatan 2 loadflow model was modified with the addition of the Iatan–Nashua 345kV line and a 345kV bus at Nashua tapped into the Hawthorn-St. Joseph 345kV line. ACC analysis was performed on this case loadflow model to determine if criteria violations identified due to adding the Iatan 2 generation were mitigated by the transmission line addition. This case did not have any criteria violations in the monitored area under normal conditions.

The following criteria violation continues to exist in the I2C plan case for contingency conditions;

Small (<1%) overload of Nashua-Lake Road 161kV line for loss of Hawthorn-Nashua

As this line has overcurrent relaying this criteria violation is not valid.

No other criteria violations not previously identified in the base case loadflow model exist in the I2C plan case.

Sensitivity Analysis of Transmission Plan I2B (I2B2):

Because the I2B plan performed poorly in the ACC analysis, it was decided to modify this plan to determine if its performance could be improved. This plan, designated I2B2, used a new 345kV line from Iatan to Platte City (approximately 16 miles) with a 345/161kV transformer at Platte City. The base case with Iatan 2 loadflow model was modified with the addition of a 345/161kV transformer at Platte City and a new 345kV line from Iatan to Platte City. ACC analysis was performed on this case loadflow model to determine if criteria violations identified due to adding the Iatan 2 generation were mitigated by the transmission facility additions. The following lines were overloaded for normal conditions;

Aquila’s Platte City-Smithville 161kV line overloaded 13% (56% under contingency)

Aquila’s Smithville-Nashua 161kV line overloaded 4% (48% under contingency)

None of the additional criteria violations from the base case with Iatan 2 continue to exist in the I2B2 plan case for contingency conditions;

The following additional new criteria violations were identified in the I2B2 plan for contingency conditions;

Platte City 345/161kV transformer overloaded 8% for loss of Iatan-Stranger Creek

Platte City 161/69kV transformer overloaded 6% for loss of Iatan-St Joe

MPS Nashua-KCPL Nashua 161kV line overloaded 6% for loss of Iatan-St Joe

Small (<2%) overload on Greenwood-Merriam for KCPL multiple contingencies.

Additional Study Analysis of Transmission Plan I2A (I2D):

After review of the initial study results, a version of Plan I2A was developed for consideration. This plan, designated I2D, used the 161kV right-of-way currently occupied by the Stranger Creek-Platte City-Smithville lines. These lines would be replaced by a new 345kV line from Iatan to Platte City (approximately 16 miles), continuing to Smithville (approximately 8 miles), and tapped into the Hawthorn-St. Jospeh 345kV line at Smithville. 345/161kV transformers would be installed at Platte City and Smithville (used Stranger Creek transformer at Platte City). The base case with Iatan 2 loadflow model was modified with the addition of a new 345kV line from Iatan to Platte City to Smithville, with Smithville tapped into the Hawthorn-St. Joseph 345kV line. The Stranger Creek 345/161kV transformer was moved to Platte City and a duplicate transformer was added at Smithville. ACC analysis was performed on this case loadflow model to determine if criteria violations identified due to adding the Iatan 2 generation were mitigated by the transmission facility additions of this plan. The following lines were overloaded for normal conditions;

Aquila’s Smithville-Nashua 161kV line overloaded 3% (58% under contingency)

None of the additional criteria violations from the base case with Iatan 2 continue to exist in the I2D plan case for contingency conditions;

The following additional new criteria violation was identified in the I2D plan for contingency conditions;

MPS Nashua-KCPL Nashua 161kV line overloaded 5% for a KCPL multiple contingency.

Initial Study Conclusions:

The transmission expansion plans utilizing only new 345kV lines tying into the Hawthorn-St. Joseph 345kV line (I2A & I2C) performed best and equally well based on ACC analysis. Plan I2D performed almost as well, but still had two small criteria violations. Plan I2D involves elimination of a tie between Aquila and Westar (Platte City-Stranger Creek), which may not be possible for contractual reasons (Jeffery generation joint ownership delivery path). Plan I2A is preferred over I2C because it uses significantly less (18 miles) new 345kV line construction.

The plans utilizing a new 345/161kV transformer (I2B & I2B2) did not perform as well. In fact, these plans do not have enough emergency transmission capacity (956+605=1561) to deliver the full generation output of Iatan 1 & 2 (683+900=1583) under contingent loss of the Iatan-Stranger Creek line. The I2B plan is the less expensive as it has by far the least amount of construction. If the Iatan 2 generator design net output is significantly less than 900 Mw, this plan needs to be reconsidered.

Plan I2A, the construction of a new 345kV line from Iatan to Smithville and a new 345kV substation at Smithville tied into Hawthorn-St. Joseph line, is the best transmission expansion plan studied using the assumptions given, for interconnecting the Iatan 2 generator into the transmission system.

Coordinated Planning:

KCPL met with personnel from Aquila to discuss the preliminary results of this study. At that meeting Aquila staff indicated a desire to develop an interconnection at Iatan for the northern part of the Missouri Public Service (MPS) territory, within 18 months. The MPS plan proposed installation of a 400 Mva 345/161kV transformer at Iatan with lines from Iatan intercepting the Platte City-Stranger Creek 161kV line. This plan is very similar to the I2B plan studied by KCPL Transmission Planning. Aquila staff noted that the Platte City-Stranger Creek 161kV line capacity could be easily increased to 584 Mva by the replacement of terminal equipment at Platte City. They also indicated plans were under development to increase the capacity of the Iatan-St. Joseph 345kV line to 1195 Mva. These upgrades overcome the major criteria violations in the I2B plan. It was decided to analyze a 2015 case with the I2B plan to determine if additional criteria violations might exist at higher load levels.