EH-89-3 Electrical Equipment in Unsafe Condition After Maintenance
ENVIRONMENT, SAFETY & HEALTH
BULLETIN
Assistant Secretary for U.S. Department of Energy
Environment, Safety, & Health Washington, D.C. 20585
DOE/EH-0095 Issue No. 89-3 August 1989
Electrical Equipment In Unsafe Condition After Maintenance Or Modification
Several investigation reports of electrical accidents have indicated the same
problem; workers have left electrical equipment in an unsafe condition after
they have performed maintenance or modifications. Those unsafe conditions
might have been discovered or avoided, if work acceptance tests and periodic
tests had been done, and if documentation, tags and protective devices had
been used correctly.
The following accidents, briefly described, illustrate the problems being
encountered:
o In one accident, a worker was severely shocked and burned when he
came into contact with a circuit breaker that was electrically
energized, even though it was supposed to be out of service and was
tagged "abandoned." The circuit was carrying 8,000 volts.
The key-type interlock, which should have prevented access to the
circuit breaker, had been left unlocked. (Maintenance work was last
performed on this equipment four years earlier.)
o In another accident, lightning caused several hundred thousand
dollars in damage when two independent protective circuit breakers
each failed to function. One breaker had been out of service for
several years. When workers refurbished the breaker and returned it
to use, they left the wire to the breaker's trip relay disconnected;
hence that circuit breaker was inoperative. The other circuit
breaker failed because of a relay that was mechanically stiff and
non-functioning.
The required acceptance tests and periodic tests, which would have
disclosed these conditions, had not been performed.
o Another accident resulted in over $3 million in electrical damages,
including the destruction of a main substation transformer. The
electrical system depended upon a dc circuit to actuate the ac
circuit breakers protecting the 13.8kV system against faults. A
modification to the dc system had introduced electrical
characteristics such that the breaker for the dc system would
sometimes trip to "OFF" the first time it was closed. Evidently, the
last time the breaker was closed, some weeks before the accident, the
breaker had tripped and was off even though the handle had remained
showing the "ON" position. Consequently, there was no actuating
power for the ac circuit breakers when a fault occurred.
Again, proper acceptance tests after the modification would have
shown the unusual behavior of the dc circuit. Also, periodic testing
of the equipment should have revealed the dangerous situation that
existed.
Safety Precautions
When electrical equipment is modified or undergoes a change in status,
measures need to be taken to assure continuing safety. Appropriate
precautionary measures should include the following good operating practices:
o Assure that required design reviews for the intended modification or
change are being implemented in a technically complete fashion.
o Comply strictly with the approved, written installation or change
procedures.
o Specify and perform the required inspections and tests to verify
that work has been completed acceptably, that equipment has been left
in the correct status and that equipment is being operated as
intended and safely.
o Assure that written operating, maintenance, and recordkeeping
procedures are appropriate for any changed status of equipment.
o Document each change on drawings, records, labels, markings and
tags.
o Independently verify that appropriate precautionary measures have
been carried out.
Recommended Actions
Actions should be taken to assure that similar unsafe conditions do not exist
at your facility. A review should be conducted to:
o Verify that various safety features, associated with electrical
components and systems, are functioning properly and have not been
degraded by past repairs or modifications.
o Verify that electrical equipment taken out of service is
de-energized, and that appropriate positive controls are in place to
prevent inadvertent energizing.
o Inspect all records, drawings, tags, labels and markings on
electrical equipment to verify that they accurately and adequately
reflect the equipment's condition.
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This publication is one of several series of bulletins published so that DOE
program managers and contractors can share information about potential
occupational safety problems relevant to DOE operations. For more information
or additional copies, contact the Performance Evaluation Division, Office of
Safety Compliance, Assistant Secretary for Environment, Safety & Health, U.S.
Department of Energy, Washington, DC 20545; telephone FTS 233-3294, Commercial
(301) 353-3284.
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