Power Quality

Site Survey

A site survey is a visual check of your facility's electrical system to ensure that it is not the source of the power quality problem. The Electric Power Research Institute (EPRI) states that approximately 80 percent of all power quality problems may result from inadequate wiring or grounding within a customer's facility. Due to this high rate, wiring and grounding checks should be the first area of investigation when performing a site survey. A brief tutorial of wiring and grounding can be found in the Appendix.

The objectives of a site survey are:

  • Determine the condition and adequacy of the wiring and grounding system 
  • Determine the quality of the AC voltage at the utilization point 
  • Check for loose connections

If the power quality problem is seen throughout your entire facility, check the electrical service entrance for faulty or loose connections first. Use an earth-ground tester to measure the resistance of the grounding system. Voltage and current readings should also be taken and recorded. From this point, each panel in the power distribution system serving the affected equipment should be tested or verified. Verification tests should include voltage measurements, proper conductor termination, and measurement of ground and neutral impedance levels. Neutral and ground bonds and isolated grounds should be installed as recommended in the National Electrical Code.

Momentary power outages and voltage sags in the electrical distribution system can also cause power quality problem that can affect your entire facility. A call to your Account Manager can verify if there was an outage in the electrical system. Please refer to the Character of Service section for details of the characteristics of electrical power that the utility delivers to your facility's electrical service entrance.

If a power quality problem is affecting only specific equipment in your facility, check the wiring and grounding for the equipment to ensure that it is properly sized and connected. Voltage and current measurements should also be taken at the input to the equipment before the equipment starts up, during start up, and after it has been running for a while. These checks may help resolve the power quality problem especially when a problem is noticed after any equipment upgrades, replacements, or facility expansions.