Survey of failure of surge protective capacitors and arresters on AC rotating machines report by working group 3.4.9 of surge protective devices committee

A survey of manufactures and users of surge protective capacitors and arresters for rotating machines was conducted to obtain device failure data or comparison with failure statistics on rotating machine insulation. Answers to two questions were sought. These questions are: (1) do protective devices reduce or increase the overall machine feature rate; and (2) is there a cost of service benefit derived from application of surge protective devices to rotating machines? The conclusions drawn from this survey are: (1) the service data for machine surge-protective capacitors and arresters are sparse and not usually recorded, and there is little assurance that the data sample was not biased by the absence of records for either a surviving unfailed population or a failed population; (2) it is not a common practice among electric utilities to apply surge-protective devices to AC motors; (3) in utility, industrial, and commercial service, the reliability level of machine-protective surge capacitors was about equal to the average reliability of large motor windings to voltage stress; and (4) if surge protective capacitor application were able to prevent all nonoverheating insulation failures, the overall machine forced outage rate would be changed by only a little