Safety Corner
Test Leads —
Avoid Falling in Love with Them
by Paul Hartman
Power Testing and Energization
O
n a flight from Seattle to the East Coast, a fellow passenger asked me
what I do for a living. I gave him the standard “electrical testing and
maintenance” answer, and he began telling me factory maintenance
stories from his work experience. I figured I was in for several hours of discussion on the subject. Never missing an opportunity to learn from a situation, I
asked the gentleman if he had any electrical safety-related issues at his facility.
As luck would have it he was full of stories that made me cringe, most of which
belonged in the unqualified worker category.
There was the story about an alligator clip on a test lead that caused a threephase fault which tripped a 1000 ampere circuit breaker. It turned out that the
test probe on the end of a meter test lead had been replaced by one of the “not
so sure if qualified” workers. The replacement clip was originally uninsulated and,
therefore, required a copious amount of electrical tape to supposedly bring it up
to an acceptable safety level. Long story short, the worker clipped it onto a phase
conductor in the subpanel. The test lead slipped off and shorted two of the phase
terminals, thus starting the fault that tripped the upstream breaker.
This reminded me of incidents that I had seen in the past where a test lead
was a contributor to an unsafe, near miss, or failure situation. For instance, many
of us have seen the test lead that works better if you just wiggle the banana jack
a little where it plugs into the meter. I am not sure if that is a meter or test lead
issue, but I am sure that it is not a correct situation.
Then there was the case of the uninsulated ground wire alligator clip that
started what turned out to be a three-phase arcing fault. How can a ground lead
start an arcing fault? Very easily. Just connect it to a panel ground point right
above the panel main circuit lugs. When the ground lead slips off, gravity kicks
in to do the rest by dropping the lead onto the breaker lugs.
Another problem was the high quality, manufacturer-supplied meter test lead
with a wire splice crimped right in the center of the lead. It seems the test lead
was cut when a tool box lid was closed on it, and the only way to fix the lead
was to splice it back together. When a worker pulled on the lead while taking
a reading, the wire pulled out of the crimp. Fortunately, there was no injury or
damage from this near miss.
www.netaworld.org Another test lead improvement
I have seen is taking a standard set
of test probes and cutting off the
insulating skirt that is part of the
probe at the end of the lead. This
kind of modification eliminates the
safety aspect of the test leads that
help prevent one’s fingers from accidentally sliding down the probe
and coming in contact with an
energized bus.
There was the customized set of
test leads used to drain the charge
out of a tested set of mediumvoltage cables (four uninsulated
alligator clips connected to bare
copper wire). When I inquired
about the uninsulated clips, the test
set operator replied, “As long as you
attach the ground bus lead first,
then you don’t feel the little spark
that jumps from the cable to the
ground lead when you clip it on”
(to the just tested cable). He was
attaching the not so insulated drain
wire clips with his bare hands.
In another case, wildly fluctuating and often unacceptable 5 kV
insulation resistance test values
were being recorded. The problem
was traced to a nice, shiny, new set
of test leads, 1000 volt test leads.
It seems that the original leads
had been lost, and the facility had
determined that 1000 volt leads
Summer 2008 NETA WORLD
were a lot cheaper. If you have ever had to purchase a set
of 5 kV test leads, they are expensive. However, regardless
of the price savings, 1000 volt leads are not an acceptable
substitute.
I almost forgot about the guy in Reno, Nevada, (this is
not a joke) that was using steel barbed wire he had taken off
of a nearby fence to extend his length-challenged test leads.
Of course he had wrapped the wire with electrical tape in a
not so successful attempt to make the situation safe. Even
though a safety incident did not occur from this usage, it
doesn’t make using barbed wire an acceptable practice.
It is hard to understand why people fall in love with their
test leads. Test leads are one of the fundamental safety devices we use every day, and they are what we use to couple
our test equipment to a potentially energized circuit. You
might say that equipment-wise test leads are our first line
of defense.
Test leads should be replaced the instant their integrity
has been compromised.
NETA WORLD Summer 2008
The cost of ensuring that every person who works with
test leads has the proper leads to safely perform his job
pales in comparison to the cost of a test set failure, customer
equipment failure, or even the worst case scenario, personal
injury.
The ultimate responsibility for maintaining quality test
leads falls to the workers themselves. Test technicians,
maintenance personnel, factory service representatives, and
electricians should all be trained in the hazards of unsafe
test leads and how to ensure that the test leads are safe for
continued use.
Paul Hartman has over 20 years experience in start-up, commissioning,
maintenance, and training in power generation, including international
projects in Pakistan, Indonesia, Thailand, Brazil, and Korea. He has been
an instructor for state certified continuing education programs. Paul is
currently Project Manager for Power Testing and Energization. He is a
regular contributor to NETA World and a frequent speaker at NETA’s
Annual Technical Conference.
www.netaworld.org