New Approaches for Maintenance Grounding in Medium-Voltage Switchgear
■Performing maintenance on medium-voltage electrical distribution switchgear involves inherent risk to the maintenance personnel in and around the switchgear. U.S. Occupational Safety and Health Administration (OSHA) 1910.269 is the standard which governs safety practices that must be undertaken, equipment that must be provided and training that must be given by employers for maintenance work in the electrical power industry. The National Fire Protection Association (NFPA) 70E is a consensus standard that lays out specific steps that shall be followed in order to create “an electrically safe work condition” during electrical switchgear maintenance.
■First, those performing the work must understand all the possible sources of electrical energy supplied to the switchgear being maintained. This includes, but is not limited to, reviewing the most current electrical drawings and sources of energy to the switchgear. Second, all the sources of electrical energy found must be properly disconnected. Third, the isolation of these sources should be visibly verified. This can be done via switch viewing windows or by withdrawing a circuit breaker from its cell. Fourth, lockout/ tagout devices should be applied according to an established policy developed by the owner or organization performing the maintenance. Fifth, the absence of electrical energy needs to be verified. This can be done with an appropriately rated voltage detection device used to test voltage differences between phase-to-phase and phase-to ground. Before and after each test, the voltage detector should be tested to determine correct operation. Lastly, the conductors in the area of switchgear being maintained should be properly grounded with devices rated for the available fault current in order to create an “equi-potential zone,” as described in OSHA 1910.269(n)(3), in which maintenance personnel may work.
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White Paper |
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Please see the document for details |
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English Chinese Chinese and English Japanese |
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2015/8/5 |
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Revision 0 |
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998-2095-08-04-15AR0 |
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530 KB |
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