DESCRIPTION

The Fresno Area consists of all or portions of Fresno, Kings, Madera, Mariposa, and Merced Counties. The bulk transmission supply for this area can import a maximum of 1300MW of power, and consists primarily of six 230kV transmission lines from the Gates, Panoche, and Bellota 230kV substations and one 115kV transmission line from Midway substation.

This area has about 1930MW of internal generation primarily from hydro generators; QFs can provide about another 230MW. The summer peak load is about 2900MW. Projected load growth in the area for the next few years is about 60MW per year on average.

PROBLEMS

The six 230kV lines from Gates, Panoche, and Bellota into the Fresno Area, along with the Midway-McCall 115kV line, are the most constrained segments of the grid serving the area.

The Yosemite Division assessment indicated that there were no normal voltage criteria violations. However, there were three normal thermal overloads which are projected to occur at year 2005 on the following facilities: (1) Panoche 230/115kV Bank #2; (2) Los Banos 230/70kV Bank #3; and (3) Panoche-Panoche Junction 115kV section of the Panoche-Oro Loma 115kV circuit. PG&E studies results also indicated that thermal overloads would also occur at year 2005 for the following contingencies: (a) Loss of a Major Source-Import/Generation Outages (b) Overlapping Major Import Circuit/Internal Generation Outages, and (c) Transformer Bank Outages (T-1).

In the Woodward Distribution Planning Area (DPA), the projected load growth rate is going to exceed the available capacity in the summer 2001 by 4.3%. This is a Normal overload problem.

The Fresno Division assessment indicated that there were no normal problems for the 2001-2005 study period. The main concerns are outages of circuit ties to the Yosemite Division, such as the Wilson-Gregg 230kV and the Kerckhoff I-Kerckhoff II 115kV circuits, which would cause problems on other import circuit ties. Other concerns are serving the Fresno 70 kV network under emergency conditions. Major transmission concerns for the Fresno area are Yosemite Transmission Circuit Tie Outages, Reedley Area, Helm and Kearney 70 kV Area, and Henrietta 70 kV area.

The Kern Division assessment identified one normal overload (in year 2005, not year 2001)-the Ganso-Midway 115kV section of the Smyrna-Semitropic-Midway 115kV circuit, which would be loaded up to 100% of its normal rating by 2005. The worst contingency to cause an overload on this circuit is a single Helms unit outage.

POSSIBLE SOLUTIONS

For the Yosemite Division within the Fresno Area, examples of solutions mitigating year 2005 thermal overload problems described above include: (1) replacing the Panoche Banks or installing a third 230/115kV bank by 2002; (2) replacing the Los Banos 230/70kV bank or installing a second 230/70kV bank by 2003; and (3) reinforcing the Panoche-Panoche Junction. There is no project recommended for year 2001.

Project T351: Woodward 21 kV Area Capacity Increase Project would install a new substation with a 45 MVA transformer and necessary feeder circuit to serve the projected load growth in the Woodward Planning Area. This project will solve the Normal overload problem for the summer 2001.

For the Fresno Division within the Fresno Area, Project T362: Oakhurst Area Reinforcement would separate the Kerckhoff I-Kerckhoff II 115kV circuit into two circuits in 2001 and then reconductoring these two circuits in 2003. PG&E has proposed many projects with various completion dates in order to solve all emergency overload problems in the Fresno area. Project T362 is the only recommended project at this moment; Phase 1 of the project will be completed in year 2001.

For the Kern Division within the Fresno Area, re-rating or reconductoring the Corcoran-Smyrna and Smyrna-Semitropic-Midway 115kV circuits is an example of a solution that would mitigate the problem described above. No project is recommended in the Kern area at this moment because there is no immediate problem needed to be addressed by the summer of 2001.

1.3 Humboldt

TYPE OF CONSTRAINTS

_ Economic (Bulk)

_ Reliability Must Run (RMR)

_ Stability:

_ Normal Overload

_ Contingency (Outage)

DESCRIPTION

The Humboldt Area covers most of Humboldt County. The Humbolt Area includes the City of Eureka. The major transmission lines serving the Humboldt Area are two 115kV lines from Cottonwood and one 60kV line from Trinity in the east, and one 60kV line from Garberville in the south. Electric supply is provided by local generation (Humboldt Bay Power Plant and QFs) and transmission imports.

The transmission system can only import approximately 70 MW of power to serve the regional loads, whereas the peak load (winter) of this area is about 190 MW. RMR contracts make up the difference between loads and import capacity of transmission lines.

This area has about 161 MW of internal generation, from thermal generators, gas turbines, and a biomass generator. QFs can provide about another 36 MW. There are another four generator units, which are off line right now with a total nameplate power of 72 MW. Projected load growth in the area for the next few years is about 2 MW per year on average.

PROBLEMS

The critical contingency in this area is the loss of Humbolt Bay PP unit followed by the loss of the Bridgeville-Cottonwood 115 kV line. Under this overlapping contingency, the transient stability problem requires a total of 171 MW of RMR to correct the transient instability problem. This amount will grow as the load grows in the future years. The total nameplate of RMR candidates is about 233 MW.

Other contingencies such as outage of the Humboldt-Arcata-Janes Creek 60 kV line, will lead to low voltages at Orick bus. Approximately 3 MW of RMR is needed to eliminate the low voltage problem caused by this contingency for year 2001. The capacity for the only existing RMR candidate is 10 MW. If for some reason this RMR candidate did not come through, the required 3 MW can come from the Humbolt area's RMR.

The worst outage in the Humboldt area is an overlapping outage of the Fairhaven generator and the Humboldt-Arcata-Janes Creek 60 kV line. Under this condition, all loads will be automatically switched to Arcata-Janes Creek 60 kV line No. 2. This results in low voltages at stations north of Arcata. This problem is addressed by project T664: Janes Creek Substation Modification Project which modifies the automatic transfer procedure under this G-1 and N-1 emergency contingency condition. The new proposed procedure would use a timer to allow automatic switching to occur only during certain (non-peak) periods of the day. Furthermore, if the Janes Creek load is successfully switched over to the No. 2 circuit, then area loads increase to the point where voltage again becomes a concern, then two distribution feeders at Janes Creek will be dropped. A voltage-sensing device would be used to automatically drop those two distribution feeders. Estimated cost of this project is $100,000. The target operation date is October 1, 2001.

POSSIBLE SOLUTION

Other than order PG&E to finish Project T664 that solves the contingency problem in the Humboldt area, there is no immediate action needed to address this year.

1.4 Chico

TYPE OF CONSTRAINTS

_ Economic (Bulk)

_ Reliability Must Run (RMR)

_ Stability:

_ Normal Overload

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