Ground-Fault Protection for Equipment

Ground-Fault Protection Switches

Equipment ground-fault protection protects conductors against overheating and faults from ground-fault currents (≤ 1200 A).

Equipment ground-fault protection is standard on 6.0P trip units.
Ground-fault pickup (Ig) (A) sets ground current level where circuit breaker will trip after the preset time delay.
Ground-fault delay (tg) (B) sets the length of time that the circuit breaker will carry a ground-fault current above the ground-fault pickup current level before tripping.
Equipment ground-fault protection can be zone-selective interlocked (ZSI) with upstream or downstream circuit breakers. Setting the ground-fault delay (tg) to the 0 setting turns off zone-selective interlocking.
Neutral protection and equipment ground-fault protection are independent and can operate concurrently.

NOTE: Use I²t off with ZSI for proper coordination. Using I²t on with ZSI is not recommended as the delay in the upstream device receiving a restraint signal could result in the trip unit tripping in a time shorter than the published trip curve.

MicroLogic Trip Unit Ground-Fault Pickup Values

Ig (= In x....)	A	B	C	D	E	F	G	H	J
In ≤ 400 A	0.3	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1
400 A < In ≤ 1200 A	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1
In > 1200 A	500 A	640 A	720 A	800 A	880 A	960 A	1040 A	1120 A	1200 A
In = sensor rating. Ig = ground-fault pickup.

MicroLogic Trip Unit Ground-Fault Delay Values

Setting	Ground-Fault Delay
I²t off (ms at In) (seconds)	0	0.1	0.2	0.3	0.4
I²t on (ms at In) (seconds)	–	0.1	0.2	0.3	0.4
tsd (min. trip) (milliseconds)	20	80	140	230	350
tsd (max. trip) (milliseconds)	80	140	200	320	500