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Chapter 6) 7SR17 Commissioning and Maintenance Guide
2.11 Restricted Earth fault (87REF)
Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
The setting resistance should be measured and the value compared to that specified in the settings data. Both
values should be recorded.
Settings Data Resistor Value
The high value of setting resistance R will often interfere with secondary current injection when using a digital test
set. It is normal practice in these cases to short out the series resistor to allow testing, the shorting link should be
removed after testing.
Since the DTL setting is generally small the pick-up setting can be tested by gradually increasing current until
element operates. The relay should be disconnected from the current transformers for this test.
Apply 2x setting current if possible and record operating time
Phase
Is
(Amps)
(sec)
REF
It is also desirable to check the operating voltage achieved with the setting resistor and all parallel CTs connected
but de-energised. A higher capacity test set will be required for this test. Adequate current must be supplied to
provide the magnetising current of all connected CTs. Precautions should be taken to ensure that no personnel
are at risk of contact with any of the energised secondary wiring during the test.
Settings Data Voltage Setting
Page 38 of 62
n/a
I
G
32S, 50G BF, 67/50G, 67/51G
87REF - Self Reset
DTL
P.U. Current
Amps
Measured
Tolerance
Operate Time
2 x Is
Measured
©2014 Siemens Protection Devices Limited
Tolerance
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