Siemens 7SR242 Duobias - Page 28

7SR242 Duobias Commissioning & Maintenance Guide
©2010 Siemens Protection Devices Limited Chapter 6 Page 28 of 57
These elements can be enabled for the I
G1
or I
G2
current inputs by relay settings, ensure that current is injected on
the correct input.
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
Is
(Amps)
DTL
(sec)
P.U. Current
Amps
Operate Time
2 x Is
NOTES
64H-1
64H-2
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 (V
S
)
V
S
Measured Settings Data:
Operate Current (I
OP
)
I
OP
Measured
64H-1
64H-2
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.
2.4.1.1 Element Blocking
The Restricted Earth Fault element can be blocked by Binary Input Inhibit. Where applied this functionality should
be checked.
Element BI Inhibits Checked
64H-1
64H-2
Check correct indication, trip output, alarm contacts, waveform record.
Check that any shorting links are removed after testing.