7SG12 DAD N Commissioning
d)
Laptop PC to drive the test set and the Reydisp Evolution relay software.
e)
500volt Variac to measure CT magnetizing characteristics.
f)
Primary test leads and injection set.
Suitable primary injection connectors and secondary injection test plugs and leads and a suitable a.c supply may
be required and must be suitable for the site concerned.
When making secondary injection tests ensure that the test circuit is earthed at one point only.
5. Insulation Resistance Test
Before commencing to inspect the wiring take the following precautions:
Isolate the auxiliary supplies.
Remove the trip and inter-trip links.
Check that the relay wiring is complete and that all terminal connections are tight and remove the C.T. earth link
for the insulation resistance tests.
Measure the insulation resistance between each section of the wiring and the other sections connected together
and to earth.
The sections comprise:
a)
C.T. secondary wiring connected to module AN1 (Analogue 1 module)
b)
D.C. wiring connected to PSU and I/O modules, excluding power supply wiring to the PSU
Module.
Before testing the D.C. wiring to earth, apply test connections between suitable points to short circuit each status
input and series resistor to avoid possible damage to the opto-coupler should the wiring be earthed.
c)
Test the power supply wiring to module PSU separately. Note that the D.C. +ve and D.C. -ve are each
connected to earth by surge capacitors.
Record the results in Table 1 - Insulation Resistance Values.
Wiring Section
Resistance MegaOhms
AN1 C.T.’s to earth and other circuits
D.C. Wiring to Earth and other circuits
Power Supply wiring to earth
Table 1 - Insulation Resistance Values
Insulation resistance values that are considered satisfactory must depend upon the amount of wiring involved.
Generally, where a considerable amount of multi-core wiring is included, a reading of 2M ohms to 3M ohms is
reasonable, for short lengths of wiring on a panel, higher readings should be expected. A reading of 1M ohm
would not normally be considered satisfactory.
6. Check of C.T and Secondary Wiring Resistance
This test is to be applied to each of the Overall Differential protections.
Isolate the auxiliary supplies.
Remove the trip and inter-trip links.
Refer to the calculated performance data for the Overall Differential. This will give the maximum permissible lead
resistance values.
©2010 Siemens Protection Devices Limited
Chapter 7 Page 4 of 8
Summary of Contents for 7SG12 DAD-N
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