TS 970 Transfer Switch
PM163 REV 0 20/02/05 33 Thomson Power Systems
12. GROUND FAULT SITE TEST REQUIREMENTS
Per NEC and UL1008, a ground fault protected system shall be performance tested when first installed
on site. A written record of this shall be made and be available to the authority having jurisdiction. A
form is provided at the back of this manual for this purpose – see SECTION 17.
Confirm and record actual trip set points in the form provided which is to be made available on request
by inspection authority.
12.1. PERFORMANCE TEST
Qualified Field Service technicians require a calibrated current injection test apparatus and
must be knowledgeable in breaker testing to provide primary neutral CT injection up to or
greater than the trip set point as selected by the responsible party. As indicated in the NEC,
the maximum setting of the ground fault protection shall be 1200 amps, and the maximum time
delay shall be 1 second for ground faults equal to or greater than 3000 amps.
The inspection authority should be contacted to confirm actual test requirements as these may
vary by region or local code requirements.
The interconnected system shall be evaluated to ensure compliance with the appropriate
schematic drawings. The proper location of sensors and power cabling shall be determined.
The grounding points of the system shall be verified to determine that ground paths do not
exist that would bypass the sensors. The use of high-voltage testers and resistance bridges
may be required. A simulated fault current is to be generated by a coil around the sensors.
The reaction of the circuit-interrupting device is to be observed for correct response. The
results of the test are to be recorded on the test form provided.
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