The San Francisco Bay Area load is supplied by both internal generation and imports from outlying 500-230 kV substations and their connecting 230 kV transmission lines


The San Francisco Bay Area load is supplied by both internal generation and imports from outlying 500-230 kV substations and their connecting 230 kV transmission lines. Most of the existing generation is concentrated in the northeast Bay Area (the Pittsburg/Contra Costa region). Major generating units in San Francisco are the Hunters Point and Potrero power plants that are also major sources of reactive power support in the area. Tesla, Metcalf and Vaca Dixn 500-230 kV substations are the three major bulk transmission sources that provide additional load-sewing support for the Bay Area. Various 230 kV interconnections from Moss Landing Power Plant and The Geysers geothermal plants to the Bay Area also result in higher power import capability for load serving purposes.
In addition to the voltage support provided by generation in the area, there are several synchronous condensers (dynamic devices) and shunt capacitors (static devices) available for voltage support at 115 kV and 230 kV voltage levels. Newark 230 kV substation near Silicon Valley also is a major location in the Bay Area because of its strong electrical interconnections with neighboring substations via 230 kV and 115 kV networks.
One of the increasingly growing concerns for electric utilities is Voltage stability and reactive power-related system restrictions. Blackouts in the northeast region in August 2003 provide a strong reminder to the electric utility industry regarding the importance of “proven” new technology applications such as Flexible AC Transmission Systems (FACTS), devices to help the grid withstand “system swings” and severe disturbances especially when load is remote from the generation sources. Analysis and mitigation of voltage instability has become an integral part of planning and operating studies for transmission asset-owning companies.
In recent years San Francisco has suffered from severe power supply disturbances and studies have shown that the area’s current transmission infrastructure is insuf¬ficient to accommodate anticipated load growth over the near future.
Pacific Gas ; Electric Company (PG;E) study alternative solutions to facilitate the shutdown of old synchronous condensers at PG;E owned Hunters Point Power Plant, which are reaching the end of their original design life. These aging assets incur high maintenance and operating costs and face the challenge to meet increasingly stricter NOx emission requirements under environmental regulations.
Six synchronous condensers at Newark 230 kV substation primarily provided voltage support for the South Bay and Silicon Valley in the past. There were serious technical, operational and environmental problems with the six condensers at Newark substation. Due to rapid load growth in Silicon Valley, system reactive margin had been reduced considerably thereby increasing the risk of voltage collapse. Consequently, the synchronous condensers or some other VAR source was vital to system security in this region. All synchronous condensers are expensive to maintain compared with traditional substation equipment. Periodic overhauls are required to ensure reliability. These overhauls are expensive because the condensers are large horizontal salient-pole machines. A mobile crane is required to disassemble the condenser for inspection and repair. In addition, the cooling water system required high maintenance. The condensers ar