Electricity Today T&D Magazine

Detecting and avoiding preventable failures

BY JAY GARNETT, Doble Engineering Company

While metal clad switchgear can be very reliable, sometimes operating for over 50 years, throughout the aging process, this group of electrical disconnect switches, fuses and circuit breakers can experience issues such as moisture ingress, animal intrusion, enclosure rusting, and insulation deterioration. One efficient approach to detect incipient failures is partial discharge (PD), a leading indicator of various failure modes. Using both acoustic and electrical partial discharge techniques, sources of partial discharge can be detected and pinpointed to a source, such as a particular metal clad compartment.

PARTIAL DISCHARGE TECHNIQUES • Acoustic methods use acoustic emission signals to detect sources of sound within the switchgear • Transient earth voltage (TEV) approaches look at signals developed in grounded metalclad surfaces • High-frequency current transformers (HFCTs) can be used to determine local sources of partial discharge for investigation