The user perception is that all, or at least a large percentage, of power problems enter the facility from the utility. This is probably true for some locations, but on average the bulk of power problems which plague the user are generated within the user’s own facility.

The problems entering a facility from the utility tend to have a greater impact on the site than most facility-created events. Typical utility generated events include:

· Power factor correction (impulse and surge).

· Breaker clearing (sag, undervoltage and outage).

· Lightning (impulse, surge and sag).

· Grid switching (impulse, dropout).

· Arcing contactors (impulse).

The place to stop or limit utility generated events is at the electrical service entrance. Once the interference enters the facility’s distribution system it is much more difficult to control. High energy suppression equipment (building service entrance protection) can be installed in conjunction with the main switchgear. A more closely alternative is the installation of a filter which would have dv/dt (frequency) filtering capabilities.

Building as the Source of Problems

The building (facility) is a source rich in power problems and potential power problems. The normal utilization of electrical energy creates any number of power line events which may effect other sensitive equipment within the facility.

Typical building or facility problems include:

· Loose connections (impulse).

· Overloaded circuits and transformers (distortion).

· Wiring errors (neutral-to-ground voltage).

· Ground loops (neutral-to-ground voltage, high frequency).

· Arcing connections (high frequency).

Power problems generated within the facility are more difficult to control. There is no substitute for a comprehensive maintenance program to identify and repair loose connections, wiring errors and other physical problems within the distributions system. The use of transformers (with some output filtering) can be effective in creating areas of electrical interest and prevent interference from one source or section being transmitted to other areas.

Equipment as the Source of Problems

Equipment, through its normal operation, may inject undesirable events into the facility electrical distribution system. Typical equipment (load) activities which cause power problems include:

· Equipment turn-on/off (impulse, sag, surge).

· Equipment operation (voltage distortion)

· Phase angle controlled loads (distortion and repetitive disturbances).

Equipment generated power disturbances are generally corrected at the equipment or by introducing mitigation equipment between the load and the facility wiring. Filters and transformer-based conditioning products are used in these situations.

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