Siemens 7SR18 Solkor - Primary Injection Tests

7SR18 Commissioning & Maintenance Guide
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2.6 PRIMARY INJECTION TESTS
Primary injection tests are to check the ratio and polarity of the current transformers as well as the secondary
wiring. Alternatively ‘On-Load’ tests may be conducted to speed to up test procedure.
Use the circuit shown in Figure 2.6-1 to check the current transformer ratio and the phase to earth connections.
Inject a current of sufficient magnitude for the relay ammeters to display. These values should be compared with
the ammeters connected in series with the relay.
Primary current
The secondary current is: Is = ––––––––––––––
C.T. ratio
Use the circuit shown in Figure 2.6-2 to check the current transformer ratio and the phase to phase connections.
Record the results: -
Phase
Injected
Primary
Current
Secondary Current
A
B
C
N
A-B Nil Nil
B-C Nil Nil
B-E Nil Nil
Figure 2.6-1 Primary Injection Phase to Earth