Cause and Effect: Arcing Transients and Equipment Faults

We recently reviewed some power monitor data for a client. Problem statement:

Breaker Q1 in the WCS electronic box trips on a sporadic basis. The breaker is the M4 and M5 fan motor overcurrent protection. We have replaced the breaker multiple times.

First pass, we noticed three very high current swells in the ground current data:

Ground RMS

We also saw 100s of very serious arcing voltage transients, not related to load current changes or other voltage events. The transients showed up on Phase-Neutral and Neutral-Ground, but the NG transients were much lower amplitude (secondary, not the primary issue).

Transient PhN Transient NG

Finally, we captured three current swell events that clearly show equipment faults to ground (notice the elevated ground current) immediately following voltage transients – cause and effect.

Fault1 Fault2 Fault3

Figuring out the cause of the transients is an exercise for the local service engineers or an onsite power quality engineer. But we’ve got a pretty clear linkage here between transients and equipment faults. Most of the time, power quality problems are a lot less concrete and clear.