Primary Injection Phase Current Testing - Siemens UL 489 Operating Instructions Manual
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25.2
Primary Injection Phase Current Testing
Circuit Breakers Without Ground Fault Protection
WL Breakers equipped with trip units without ground fault protection can be easily single phase tested by injecting current into either the line
or load connection of any phase and out the opposite connection.
Figure 2
ETU
Circuit Breakers With 3- or 4-Wire Residual Ground Fault Protection
WL Breakers equipped with trip units with residual ground fault protection must be phase injected such that the ETU sees two active phases
which cancel each other out. This cancellation prevents the ground fault function from tripping. This cancellation is accomplished by inject-
ing current into the line side of one phase, out the load side, back into another load side and back out the line side.
Figure 3
ETU
If it is not possible to inject phase current into the breaker as shown in the figure above, the Ground Fault Mode switch can be used to tell the
ETU to look for a ground fault signal on a different set of terminals. As stated above, putting the Ground Fault Mode switch in the Direct
Sense position will cause the ETU to look for ground fault current on terminals X8.11 and X8.12 and not do the residual calculation. This
method can only be used if it is possible to remove the front cover of the breaker to access the switch on the side of the ETU. The switch
must be returned to its original position after testing is complete. On an ETU776, these settings are done via the LCD and keypad as there
is no physical switch.
25 – 4
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