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DEVELOPING AND IMPLEMENTING AN EFFECTIVE ELECTRICAL MAINTENANCE PROGRAM Part I: Selection Of A Testing Firm Part II: Developing Specifications Part III: Anatomy Of a Shutdown; Implementing The Program |
The Maintenance The shutdown was scheduled to start at 7 AM so we arrived on site at 6 AM. This would give all our personnel a chance to do a quick walk of the site seeing where each of our people would be located. A forms and procedures package was provided to each of our technicians and a "tailgate" safety meeting was completed with Powertronic personnel providing any particular requirements at the facility. We met with the contractors and facility personnel and were advised that the shutdown of the facility was in progress. Our equipment was distributed throughout the facility and placed in each substation. The facility supervisor required all personnel to assemble in the cafeteria while the shutdown safety procedures were followed. We went with the facility personnel and electrical contractors as each substation was removed from service. Power was removed from the indoor lineup of 4 high voltage switches, which distributes power to each of the substations and the outdoor main switch. With all power removed from the facility and temporary power on, the utility completed their disconnect procedures. Depending on the utility and disconnect requirements, this shutdown can take from 30 minutes to several hours. While they were disconnecting the main power, the facility personnel followed proper grounding procedures by verifying power was off, and installed safety grounds on the load side of each high voltage switch on the indoor switch lineup (this work was two disconnects removed from the utility). While this description of the process seems short, the shutdown took several hours. During this time all maintenance personnel were standing by in the cafeteria waiting. The utility disconnect and shutdown safety procedures followed, personnel were assembled into maintenance groups and the work finally began. Each substation was cleaned, mechanical connections checked and equipment electrically tested. To my surprise, the facility introduced me to a Factory Mutual representative who wanted to ask questions regarding the maintenance. This surprise me because the facility insurance representative often provides recommended guidelines for maintenance but I had never had one actually show up during the shutdown. The representative review the procedures we were following and asked questions about our testing Factory Mutual create a pamphlet, Electrical Testing 5-20/14-22, that provides maintenance guidelines and an Electrical Testing Matrix. It would be simple to say the maintenance went well, no problems were encountered and the equipment was in good condition. Sometimes that happens, but then there wouldn't be much of a story to tell. Here is an overview of the maintenance, there were problems in three of the four substations and the fourth substation was only two years old. The following is an excerpt of the actual job report.
SUBSTATION NUMBER 1 Service Performed: Preventative Maintenance was completed on one pad mount transformer outdoors, one 4000 ampere main fused disconnect switch and the inside main equipment included four sections of switchboard. This included the new switchboard installed during the shutdown. The main switch included ground fault and there were 26 molded case feeder circuit breakers The outdoor pad mount transformer was inspected, primary and secondary connections checked. Turns ratio and insulation resistance testing was completed on the transformer. There was some beaded water noted on the tank of the transformer inside the high and low voltage compartments. This was caused by a gap in the compartment housing, see finding #1 below. An oil sample was drawn and test results will be provided in approximately three weeks. The previous oil analysis completed in 1994 will also be provided, which can be used for comparative purposes. The low voltage switchboard was cleaned, inspected and electrically tested. The switchboard interiors were wiped down and vacuum cleaned by the electrical contractor and facility personnel. Technical assistance was provided to the electricians checking and cleaning the equipment. Switch load cables and bolted bus connections in the switchboard were checked for proper torque. Cable connections were checked on all feeder circuit breakers. Contact resistance tests were completed on the main fused disconnect switch and all feeder circuit breakers in the switchboard including the newly installed switchboard section. The ground fault relay on the main switch was tested in accordance with manufacturers' instructions and operated properly.
Recommendation: Silicone was provided by the facility
and was applied inside both the high and low voltage compartments. This
condition should be monitored periodically to ensure the leak is
stopped.
Recommendation: All phase barriers should be replaced
due to the tracking and condensation. Ensure compartment heaters are
always operational by installing some type of metering or pilot device.
Recommendation: Properly install all insulators (12) by
flipping them over.
Recommendation: None, corrective action was taken. The ground
fault relay was adjusted to 1000 amperes as recommended by Factory
Mutual.
Recommendation: None
SUBSTATION NUMBER 2 Service Performed: Preventative Maintenance was completed on one dry type transformer, one 2500 ampere main fused disconnect switch with ground fault and 26 molded case circuit breakers. The transformer was inspected, primary and secondary connections checked. Turns ratio and insulation resistance testing was completed on the transformer. The low voltage switchboard was cleaned, inspected and electrically tested. The switchboard interiors were wiped down and vacuum cleaned by Current Electric and Mennen personnel. Technical assistance was provided to the electricians checking and cleaning the equipment. Switch load cables and bolted bus connections in the switchboard were checked for proper torque. Cable connections were checked on all feeder circuit breakers. Contact resistance tests were completed on the main fused disconnect switch and all feeder circuit breakers in the switchboard. The ground fault relay on the main switch was tested in accordance
with manufacturer instructions and operated properly.
Finding Recommendation: None, corrective action was taken. The switch was cleaned, lubricated and blades adjusted to proper values. The switch is operating properly.
SUBSTATION NUMBER 4 Service Performed: Preventative Maintenance was completed on one dry type transformer, one 4000 ampere main and 12 feeder electronic trip molded case circuit breakers. The transformer was inspected, primary and secondary connections checked. Turns ratio and insulation resistance testing was completed on the transformer. The low voltage switchboard was cleaned, inspected and electrically
tested. The switchboard interiors were wiped down and vacuum cleaned by
the electrical contractor and Facility personnel. Technical assistance
was provided to the electricians checking and cleaning the equipment.
Switch load cables and bolted bus connections in the switchboard were
checked for proper torque. Cable connections were checked on all feeder
circuit breakers. Contact resistance tests were completed on the main
fused disconnect switch and all feeder circuit breakers in the
switchboard.
Finding Recommendation: None, corrective action was taken. All bolted
bus connections were checked and torqued by contractor and Facility
personnel. This may have contributed slightly to the transformer noise
problem.
Finding Recommendation: None, corrective action was taken. Contractor personnel were advised of the problem and they rerouted the cables so they all pass on the same side of the mounting channel.
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Copyright (c) 2002 Powertronic, Inc. All Rights Reserved. |
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