6 December 2006
Including change 1, 7 December 2006
lines must be provided with discharge devices to discharge the voltage to 50 V or less,
within 5 minutes after the capacitors have been completely disconnected from the
circuit. Wear appropriate levels of PPE identified in Chapter 4.
9-4.4.1 Discharge circuits are intended to discharge capacitors after the circuit is
deenergized. Since there could be no indication that the circuit is burned out or
otherwise not functioning, always assume capacitors are fully charged until tested.
9-4.4.2 Line capacitors removed from service for any purpose must be considered at
full or higher voltage, until the terminals have been shorted together and discharged by
an approved method. Do not short terminals until capacitors have been deenergized for
at least 5 minutes to allow time for the voltage level to reduce.
9-4.4.3 It is not safe to use fuses or disconnect switches to disconnect large capacitor
banks (above 60 kilovolt-reactive single-phase, or 180 kilovolt-reactive three-phase).
Circuit breakers or switches designed specifically for this purpose must be used.
9-4.4.4 After disconnecting all capacitor banks, wait 5 minutes. Short together and
ground all terminals; ensure the neutral is grounded. All operations must be performed
using rubber gloves and a hot stick.
9-4.4.5 Grounds and terminal shorts on capacitors must be left on until the work is
9-4.4.6 Barricade the work area as a safety measure for other workers, when working
on or testing capacitors in the shop.
9-4.4.7 Capacitors made before 1979 usually contained PCBs. Refer to the
precautions listed in Chapter 3 for hazardous materials if the case is ruptured or any
liquid is visible on the outside of the case.
. These capacitors have
a high impedance, which
results in a long discharge period. This characteristic of coupling capacitors is typically
overlooked, which makes them particularly hazardous to personnel if not properly
grounded. To minimize shock hazard follow the precautions below:
A coupling capacitor must always have a shorting wire installed.
9-4.5.2 During maintenance, a grounding wire must be connected to each exposed
metal terminal that a worker could contact. Grounding wires must be left in place for the
entire duration of maintenance.