Lifeline Response to the Tejon Ranch Earthquake

Abstract

The vulnerability of important high voltage switchyard equipment to low seismic input motions has again been demonstrated. Ten of sixteen 230 kV circuit breaker phases failed at the Edmonston Pumping Plant on the California Aqueduct. Failures were primarily porcelain members. The failures were due to both dynamic response of the members and to a lack of slack in conductors connecting adjacent equipment. The aqueduct was out of service for four days until power was partially restored. Repairing or replacing all damaged equipment is expected to take from 6 to 8 weeks. The importance and vulnerability of high voltage power equipment, the long time required to make repairs, and the difficulty in obtaining spare parts quickly emphasizes the need for cost effective measures to improve the seismic response of this type of equipment. While this earthquake did not substantiate the effectiveness of a base isolation system installed on one circuit breaker, it did illustrate the need for instrumentation to evaluate the performance of these systems. Leaks developed at two Smith-Blair mechanical couplings in one of two 192″ diameter aqueduct siphons near the pump plant. Whether this was due to ground deformations or inertial loads could not be determined.