Effect of shock and vibration on relays

TWENTY-EIGHT electrical operating companies, surveyed by a questionnaire,^∗ reported on 126 cases of faulty relay operations caused by shock or vibration within the past 10 years. Analysis of the replies indicates that approximately 53 per cent of the cases were caused by shock and 47 per cent of the cases caused by vibration. The vibration was caused by rotating machines or by transients such as passing trains or trucks. A majority of difficulties caused by shock occurred where relays were mounted on hinged panels.