7PG21 Solkor Rf Commissioning
©2012 Siemens Protection Devices Limited
Chapter 6 Page 9 of 21
The test should be made with the load current in the feeder equal to at least 10 -15% of the rating of the feeder
current-Transformers. Since in these tests all three phases of the primary circuits are energised, take care that
the current-transformer secondary leads are not open circuited.
Remove the trip-links at both ends of the feeder but check that the remainder of the equipment, including the
pilots, is connected for normal operation.
Connect the secondary circuit at both ends to simulate an external Red-Earth fault condition as shown in Fig. 3(a)
(Solkor Rf without isolating transformers) or Fig. 3(b) (Solkor Rf with isolating transformers). Record the various
current levels in the test circuit.
If the pilots and current transformers are correctly connected the d.c. current in the operating coils of the relays
should be negligible.
If damage has been sustained a claim should immediately be made against the carrier and the local Siemens
office should be informed.
Conditions of current transformers connections
Primary
current (A)
Secondary
current (A)
Tripping relay
(mA d.c.)
Normal
R-E
Reverse
Normal
Y-E
Reverse
Normal
Feeder ends
1
B-E
Reverse
Normal
R-E
Reverse
Normal
Y-E
Reverse
Normal
Feeder ends
2
B-E
Reverse
Table 4 - stability tests
Reverse the leads to terminals 10 (23) and 7 (24) at one end of the feeder to simulate an internal Re-Earth fault.
Alternatively reverse the pilot connections at one end of the feeder to unstabilise the protection.
Check that there is a large increase of d.c. current in the operating coils of the relays.
If required repeat these tests for the other phase to earth conditions. Record the results for each end of the feeder
as shown in Table 4.