System Grounding; Hi-Pot Testing - GE 735 Instruction Manual

2.2 ELECTRICAL
Two separate grounds are brought out to rear terminals. The safety ground (terminal G12) makes a solid electrical connec-
tion to all internal metal chassis parts and causes a fuse to blow should a short develop to the case. It ensures operator
safety in the event of a fault. A separate green ground screw is also provided on the back of the chassis for the safety
ground.
Surge suppression components are grounded to a separate filter ground (terminal G11). These components are designed
2
to conduct during transients at input terminals to prevent nuisance operation or damage to internal components. For reli-
able operation both grounds must be tied directly to the ground bus bar of the switchgear which is itself connected to a solid
ground. Braided cable or heavy solid copper wire (such as 10 gauge) should be used for optimum transient protection. Do
not rely on a ground connection to a part of the metal switchgear enclosure because a low impedance to ground cannot be
guaranteed.
Prior to leaving the factory, all terminals except filter ground and communications are hi-pot (dielectric strength) tested. If hi-
pot testing is to be performed on an installed relay for insulation verification. The hi-pot potential is applied between the
wired together terminals and the enclosure ground according to the figure below. A potential of 2.0 kV is to be applied for 1
minute to test dielectric strength. To effectively clamp transient voltages at a level sufficient to protect the internal circuitry,
the internal transient protection devices conduct below the hi-pot voltages used for insulation testing. Consequently, the fil-
ter ground terminal G11 must be left floating for this test.
Disconnect the communications terminals and filter ground during dielectric strength testing (hipot) or
damage to the internal surge protection devices may occur.
WARNING
2-12
Figure 2–15: HI-POT TESTING CONNECTIONS
735/737 Feeder Protection Relay
2 INSTALLATION

2.2.6 SYSTEM GROUNDING

2.2.7 HI-POT TESTING

GE Power Management