Northern California Impacted by Brief Power Outage; Transmission Equipment Failure Triggered 20 Minute Disruption

Business Wire, Jan 21, 2001

News Editors

FOLSOM, Calif.--(BUSINESS WIRE)--Jan. 21, 2001

Already under a Stage Three Electrical Emergency due to scant resources, the California Independent System Operator (California ISO) encountered a significant and sudden loss of transmission capacity today that forced municipal utilities in Northern California to endure a brief 20 minute transmission-related outage.

About 120 megawatts of load shedding in Northern California was initiated when electricity that normally flows on the 500 kilovolt Pacific DC (Direct Current) Intertie was automatically redirected on to the California Oregon Intertie, a 500 kilovolt AC (Alternating Current) line linking northern and southern California. The transmission disruption occurred when the DC Intertie sensed an equipment malfunction at a substation operated by the Bonneville Power Administration 90 miles east of Portland. The California ISO issued the controlled outage to keep the AC lines from being overloaded at Path 15, a group of high-voltage lines in central California already at their limit because of low resources in the northern part of the state. By issuing the outage, the California ISO averted possible rotating blackouts for Northern California should Path 15 have overloaded to the point that the transmission lines were damaged.

The California ISO does not forecast further outages tonight, but is keeping a close eye on any transmission problems. Conservation is strongly encouraged as the control area remains under an extended Stage Three Electrical Emergency through tomorrow night, Jan. 22, 2001 at midnight, due to low operating reserves.