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 Lightning strikes or faults like downed utility lines can cause momentary outages. A recloser or similar function in a circuit breaker control can clear some of these faults. Some will not be cleared quickly, and produce a longer outage. Whenever a fault occurs, it will affect nearby circuitry. This also applies to an especially heavy load on a circuit. The latter usually has no serious effect in the rest of a facility, although a fault may impact a nearby circuit. A circuit that includes an under-voltage device, for example, could be bothered by a nearby fault. A fault should be cleared before the under-voltage device reacts to the associated voltage dip, so attention would be warranted. If such a situation is suspected, a one-line diagram would help identify the problem.
Uninterrupted power supplies (UPS), silicon-controlled rectifiers (SCR) and variable frequency drives (VFD) can cause line disturbances. The heating effect of a harmonic-rich current on a protected load may require a different level of protection. Relays designed to operate on certain frequencies may function incorrectly with a high level of harmonics.
Harmonics might affect nearby circuits in surprising ways, even passing through transformers and bothering equipment in adjacent buildings where there might be little reason to suspect their presence. A harmonic analysis of the voltage at your facility might identify the presence and nature of bothersome disturbances in your power supply.
Most frequently encountered is the third harmonic, which is generated by commonly used power supplies for computers and other electronic devices. DYMAX can provide an analysis of your electrical power, including a breakdown of harmonics that might be present. Harmonic filters, particularly useful where third harmonics are present in significant values, can radically reduce the undesirable effects of harmonics generated primarily by the nature of the connected loads.
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