Siemens 7SR51 - 87 GH Restricted Earth Fault Protection - High-Impedance

87GH Restricted Earth Fault Protection – High-Impedance
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 Measured
The high value of setting resistance R will often prevent 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 2 times setting current if possible and record operating time.
Phase I
set
(Amps) DTL (sec) P.U. Current
Amps
Tolerance Operate Time
2 ⋅ I
set
Tolerance
It is also desirable to check the operating voltage achieved with the setting resistor and all parallel CTs
connected but de-energized. A higher capacity test set will be required for this test. Adequate current must be
supplied to provide the magnetizing current of all connected CTs. Precautions should be taken to ensure that
no personnel are at risk of contact with any of the energized secondary wiring during the test.
Settings Data Voltage Setting Measured
To complete testing of the REF requires primary injection through the phase and residual REF CT in series to
simulate an out of zone fault and ensure stability of the relay. The test can then be repeated with the REF CT
secondary connections reversed to prove operation.
Element Blocking
The Restricted Earth Fault element can be blocked by Binary Input Inhibit. This functionality
should be checked.
Element
BI Inhibits
87GH
Check correct indication, trip output, alarm contacts, waveform record.
Check that any shorting links are removed after testing.
9.9.28
Functional Tests
9.9 Protection Functional Tests
496 Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019