Maintaining Electrical Protective Devices
Jun 23, 2003 12:00 PM, By Dennis K. Neitzel, AVO Training Institute
Several studies have shown that electrical protective devices (circuit breakers and relays), which were not maintained within a five-year period, have a 50% failure rate. Maintenance of the circuit breakers will generally consist of keeping them clean and properly lubricated. The frequency of maintenance will depend on the manufacturer’s recommendations and the cleanliness of the surrounding area. If dust, lint, moisture, or other foreign matter is present, then more frequent maintenance is necessary.
If these devices are not properly maintained, an excessive time delay in operations could occur which would affect the outcome of the Flash Hazard Analysis required by NFPA 70E-2000, Part II, paragraph 2-1.3.3. The Flash Hazard Analysis must be performed before anyone approaches exposed electrical conductors or circuit parts that have not been placed in an electrically safe work condition. In addition, Paragraph 2-1.3.3.2 requires a flash protection boundary to be established. All calculations for determining the incident energy of an electrical arc and for establishing a flash protection boundary require the arc clearing time. This clearing time is derived from the engineering coordination study, which is based on what the protective devices are supposed to do.
Maintenance is a very critical part of the flash hazard issue. Evidence has proven that inadequate maintenance can cause unintentional time delays in the clearing of these devices during a short circuit condition. If, for example, a low-voltage power circuit breaker had not been operated or maintained for several years and the lubrication had become sticky or hardened, the circuit breaker could take several additional cycles, seconds, minutes, or longer to clear a fault condition.
Neitzel is the director of the AVO Training Institute, Dallas, Texas
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