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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