Power System - Grounding

Anytime sensitive loads are used, great care should be taken to ensure that the wiring and the grounding are appropriate. Every aspect of the power system should meet, or exceed, the National Electrical Code requirements. It is important to realize that the Code is concerned with safety, not power quality.

The impact of improper grounding cannot be understated. Poor grounding can significantly affect the performance and reliability of devices such as process control computers, variable speed drives, and electronic machinery.

Should local area networks (LANs) be in use, grounding is even more important. In computers, the internal digital reference is usually tied directly to the input power ground. Therefore, 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, current will flow through the data cable connecting the two PCs. This can disrupt and even damage their I/O ports.

Proper grounding practices take on a whole new dimension when ensuring good ground connection between multiple service drops. Ground loops between a computer on one system and the control mechanism it communicates with on another must be prevented.