Page 37 - 通用电气（中国）有限公司

EntelliGuard* L

Ground Fault Protections GF & GFD

Ground Fault Protection (GFsum)
To protect an installation or a part thereof against
indirect contact, Protection Devices can be used to
automatically disconnect the power supply when
a fault to earth is detected. The HD384 installation
standard requires that the mentioned device
senses the fault and then interrupts the supply SET UP BREAKER GF
within a specified time frame. RATING SUM
A short-circuit device as an EntelliGuard METER 1000A PICKUP
0,3
Power Circuit Breaker can be used to meet x CT
this requirement. However these short-circuit STATUS BAND Ground fault protection
2
protection devices are normally set at values that Slope
are too high to detect normally occurring faults EVENTS OFF
to Earth.
The optionally available Ground Fault protection
feature is specifically designed to detect lower EntelliGuard GT Electronic Trip Unit
currents than a standard short-circuit Device and 10
operate by residually summing the current in the - Time Current Curve
Phases and Neutral. When a fault to Earth creates GF- Protection Device
2
an unbalance in the system the resulting Fault I t slope -OFF-
Current is detected by the device that produces an - GFDB Band Intro
alarm signal or trips the associated circuit breaker
thus disconnecting the circuit.
The EntelliGuard Ground fault device has an A
adjustment range of 0.2 to 1 (±15%) times the
chosen breaker rating (In) and can be set in steps of
0,01 (pick up setting). To allow selectivity with other 1
downstream protection devices there are 0,8 B
14 different time band settings available. 0,6
The graph indicates a number of the available
14 time bands across the full adjustment range. 0,4
The table contains the minimum delay time and C
the maximum total interruption times for all time
band settings. 0,2
The Ground fault device must monitor the current D
in all phases and the Neutral. When a 3 pole device
is used in a 4 wire (3phase + Neutral) system a 4th 0,1
sensor must be placed in the Neutral. On use of a
4 pole EntelliGuard breaker the sensor is already E
present in the Neutral pole.

Ground Fault Protection I t or I t bands (slope)
2
4
The GF device can also be set to a slope value. The Tripping Time In Seconds (s) X
4
2
available multiple I t and I t slopes are normally
used to achieve selectivity with downstream fuses
or to improve selectivity with downstream circuit
breakers. 0,01
1 , 0 0 0 , 1 0 1 0 , 0 0
The user has the possibility to choose a current x Breaker Rating In
adjustment of 0.2 to 1 (times the chosen the ]
chosen breaker rating (In) in steps of 0.01
and one of 14 time bands.
There are three available slopes: Low, Medium and
High.

2
Ground fault tripping times at indicated levels per selected GFDB band -I t slope OFF, in milliseconds
x Ir 1 2 3 4 5 6 7 8 9 10 11 12 13 14
0.2 x Tripping 110 120 140 170 190 240 270 340 400 450 600 700 800 900
±10% Non Tripping 50 60 80 110 130 180 210 280 340 390 540 640 740 840
0.6 x Tripping 110 120 140 170 190 240 270 340 400 450 600 700 800 900
±10% Non Tripping 50 60 80 110 130 180 210 280 340 390 540 640 740 840

B.7