With freezing weather upon many of our areas of operation, it is an opportune time to share an arc flash experience that typically can be overlooked by some electricians.
The effect of condensation can have on electrical testing meters. Read the story below:
An electrician took his tools and voltage meter from being stored outside in a vehicle with temperatures in single digits and brought in to a generator room that was at 80 degrees to test 480V 3 phase circuits. The electrician held his meter in his left hand along with one of the tests leads on L1 and with his right hand the other test lead and touched L3. The electrician stated he saw the brightest light he had ever seen, heard the loudest noise, and that the temperature was hot. He had no clue what had happened, nor why it happened. The room went dark, his ears were ringing. He was in shock, then heard the stand-by generator start. So, at that point he knew he was still alive. A few seconds had gone by when he notices pain in his left hand. He later had found out he had tripped the line fuses on the utility side.
He later learned that condensation had built up on/inside his meter from the temperature difference from his vehicle to the generator room. The condensation allowed for an alternate path for the meter to travel and caused a phase to phase short through his meter.
Things to remember:
□ How to properly use your meter
□ What are the specifications of your meter
□ Proper use and storage of your meter
□ Operating temperature of your meter
□ The effects of condensation
Do you know the category rating of your meter? CAT I, CAT II, CATIII, or CAT IV
□ CAT I
Measurements of voltages from specially protected secondary circuits. Such voltage measurements include signal levels, special equipment, limited-energy parts of equipment, circuits powered by regulated low- voltage sources, and electronics.
□ CAT II
This is sufficient for a receptacle outlet circuit or plug-in loads, also referred to as “local-level electrical distribution”. This would also include measurements performed on household appliances, portable tools, etc.
□ CAT III
Distribution wiring are qualified for this group, including “mains” bus, feeders and branch circuits. Also, permanently installed or “hard-wired” loads and distribution boards. Other examples are higher voltage wiring, including power cables, bus bars, junction boxes, switches, and stationary motors with permanent connections to fixed installations.