Facts technology application to retire aging transmission assets and address voltage stability related reliability challenges in San Francisco Bay Area

Loadability of electric transmission system in North America is currently influenced and restricted by several technical considerations. Since highly loaded transmission systems (with, consequently, high reactive power losses) are at the root of many reactive deficiency problems, it is not surprising that voltage instabilitykollapse are cause for increasing concern among transmission planners and operators. Detailed technical studies routinely performed by planners demonstrate that bulk system utilization is often restricted by voltage or angular instability related limits, which are typically significantly lower than thermal capacity limits. Relaxing such non-thermal transmission limitations in a cost-effective fashion can be very challenging in a deregulated utility environment. Recent experience at PG&E'has shown that retirement of six aging synchronous condensers in the San Francisco Bay Area (which'cumently impose additional technical, operating and environmental problems coupled with high maintenance and operating costs) can be successfully accomplished with a (semiconductor-based) FACTS device installation in a cost-effective manner and thereby maintaining bulk transmission system reliability. PG&E installed a 230 kV (;100/+200 W A R ) SVS system at Newark substation near Silicon Valley during 2002. As a replacement for the condensers, a Static VAr Compensator (SVC) in the Bay area will help maintain an acceptable and necessary reactive reserve margin to prevent voltage instability arising from unscheduled generation and transmission contingencies during high load conditions in the Bay Area. This paper addresses reliability related issues arising from aging infrastructure and summarizes successful application of FACTS technology (equipped with smart digital control systems) to prevent any degradation of system performance upon retirement of synchronous