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25 – 3
Ground Fault Mode Selection (Setting)
Before beginning to test, the Ground Fault Mode setting should be verified.
a. If connected to a 3- or 4-wire residual system, the mode switch must be in the summation position. In this mode, the ETU will per-
form a vector summation of phases A, B, C and if connected, N (Neutral). If this sum is not zero, a ground fault is present and the
ETU behaves according to the pickup and delay settings.
b. If connected in system where an external iron-core sensor detects the ground current (such as an MDGF scheme), the switch must
be in the Direct Sense position (down). If the switch is in this position, the trip unit will not do a residual calculation and will only
respond to a signal from an external iron-core sensor.
c. On an ETU776, these settings are done via the LCD and keypad as there is no physical switch.
Phase Loss Sensing
When single-phase testing, make sure that the short-time delay is not set to the 20ms setting. In this position, a phase-loss sensitivity func-
tion is enabled. This function is designed to protect motors from heavy imbalances and loss of one or more phases. When active, and the
trip unit detects that the least heavily loaded phase is 50% lower than the most heavily loaded phase, the long-time pickup setting(IR) is
reduced to 80% of setting indicated on the display or dial. When this unbalance condition no longer exists, the setting is returned to normal.
Single-phase testing will be recognized as a phase unbalance and the long-time pickup will be reduced to 80% of its set value. The resulting
trip timing will be faster than indicated in the trip curves. For an ETU776, the phase-loss sensing is controlled by the "PhaseSen" menu item
under the protective parameters. When short-time delay is set to 20ms, phase-loss sensing cannot be turned off.
External Ground Fault Sensor Inputs
There are three types of connections for ground fault protection:
a. If applied in a 4-wire system, there will be an external air-core sensor connected to the second ary wiring points X8.9 & 10.
b.
If applied in a direct sensed scheme, there will be an external iron-core 1200:1 CT connected to secondary wiring points
X8.11 & 12.
c.
If applied in a 3-wire system, secondary wiring points X8.9 & 10 must be shorted together.
Activating the WL Trip Unit
The external neutral sensor does not provide power to the trip unit when current is flowing through it. The trip unit must be activated by an
auxiliary power source or phase current in order to detect and react to current flowing though the external neutral sensor.
The WL trip units will become active and begin protecting at approximately 80A in a single phase in Frame Size 1 & 2 breakers and approx-
imately 100A in a single phase in a FS3 breaker.
Summary of Contents for UL 489
Page 36: ...5 21 Frame size II 3000 A Frame size III 1 Holes 14 mm 0720 1 0721_nu ...
Page 63: ...7 2 Horizontal connectors 0733_nu top view ...
Page 64: ...7 3 Rear vertical connectors 0734_nu top view rear view ...
Page 65: ...7 4 Front connectors 0736_nu front view top view ...
Page 66: ...7 5 Front connectors and pressure wire terminals 0737_nu top view front view ...
Page 67: ...7 6 7 2 Frame size II fixed mounted version 0494 3_nu ...
Page 68: ...7 7 Class C always 0494 5_nu top view rear view ...
Page 69: ...7 8 2500 0738_nu LH side view front view ...
Page 71: ...7 10 7 4 Frame size III fixed mounted version 0495 1_nu LH side view ...
Page 72: ...7 11 0495 2_nu top view top view ...
Page 73: ...7 12 0495 3_nu top view rear view ...
Page 75: ...7 14 7 5 Door cut outs fixed mounted circuit breaker Frame size I 0735_nu ...
Page 76: ...7 15 Frame size II III 0496_nu ...
Page 77: ...7 16 7 6 Frame size I draw out version 0745_nu ...
Page 78: ...7 17 0746_nu rear view top view ...
Page 79: ...7 18 0747_nu bottom view ...
Page 80: ...7 19 0748_nu ...
Page 81: ...7 20 0749_nu ...
Page 82: ...7 21 7 7 Frame size II draw out version 0490 1_ul ...
Page 86: ...7 25 7 8 Frame size III draw out version ...
Page 87: ...7 26 ...
Page 88: ...7 27 ...
Page 89: ...7 28 7 9 Door cut outs for draw out circuit breakers Frame size I 0750_nu ...
Page 91: ...7 30 7 11 External sensor for neutral conductor WLNCT2 ...
Page 92: ...7 31 WLNCT3 ...
Page 107: ...9 5 I tripping Ground fault tripping ...
Page 351: ......