Power System Effect on Disrupted Equipment

Anytime sensitive loads are used, great care should be taken to ensure that the wiring and grounding are appropriate. Sensitive loads are not confined just to computers. They include other equipment like VSDs, large computer controlled machinery, and computerized test and monitoring equipment. Every aspect of the power system should meet, or exceed, the National Electrical Code requirements. It is important to realize that the Code is not concerned with safety, not power quality.

Grounding is often a key ingredient in equipment disruption problems. The AC power ground is used by the electronic device as its digital reference. Noise and transients can travel along the ground and enter the device, disrupting proper data flow. This disruption usually results in a lock-up.

If local area networks (LANs) are in use, grounding is even more important. The digital reference of PC #1 on the LAN is the outlet it is plugged in to. The same applies to PC #2. If a voltage difference exists between these two ground points, then current will flow through the data cable connecting the two PCs. This can disrupt data flow and operation.

If wiring is found that violates the Code, it should be fixed immediately. Oftentimes, bringing the electrical system up to Code resolves many power quality problems.

If poor grounding is a concern, use isolated ground receptacles, isolated ground busses in the panel, and isolated ground conductors to alleviate many problems.

When an isolated ground conductor is used, it should be run in the same raceway as the power conductors, and terminated at the neutral-to-ground bond of the power source. This source is the transformer or service entrance directly feeding the loads.

Ground rods for grounding sensitive electronic devices inside the building are not recommended.