Violations of Art. 250, Part V and Chapter 3 of the NEC are responsible for most of the equipment damage related to power quality. But what exactly are these violations?

The Art. 250, Part V violations are errors of bonding. From Art. 100, we know that bonding means creating a metallic path that establishes electrical continuity between metallic objects. When this continuity is absent, you get a difference of potential between those objects. This voltage can build up to fairly high levels before equalizing via a flashover. That particular event destroys semiconductors and also presents a personnel hazard.

Article 250, Part V addresses another issue, which is that of circulating currents. By establishing a system bonding path, you provide electricity with a low impedance path for getting back to its source — instead of circulating in circuits and overheating components.

A common mistake, particularly with electronics, is driving a ground rod and "grounding" (connecting to dirt) the vendor equipment. This procedure has no technical reason for being done. It neither establishes electrical continuity between metallic objects, nor does it provide electricity with a low impedance path for getting back to its source. Consequently, you get flashovers and circulating currents, which tend to turn circuit boards into toast.

Chapter 3 wiring method requirements exist primarily to prevent the melting of conductors. However, many of these requirements also have an effect on whether power quality issues will damage equipment (or arise in the first place).