Areva MCAG 19, Service Manual

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Page 5
2.5 Insulation
The relay and its associated wiring, may be insulation tested between:
a) all electrically isolated circuits
b) all circuits and earth
An electronic or brushless insulation tester should be used, having a dc voltage not
exceeding 1000V. Accessible terminals of the same circuit should first be strapped
together. Deliberate circuit earthing links, removed for the tests, subsequently must
be replaced.
Disconnect the external wiring from the appropriate case terminals to low
application of the test supply.
Consult the appropriate application diagram for the case terminals
FIMCAG11 001 for MCAG19/39 relays
FIMCAG31 001 “ “ “ “ “
The relay ratings and settings are indicated on the front of each module.
2.6 Earthing
Ensure that the case earthing screw is used to connect the relay to a local earth.
2.7 Main current transformers
Do not open the secondary circuit of a live ct, since the high voltage produced may
be lethal to personnel and could damage insulation.
2.8 Equipment required
A current source capable of supplying sinusoidal current at the appropriate test
current levels.
An ammeter with the appropriate current range.
2.9 Electrical tests
Set the plug bridge to its lowest value.
Set xI
s
potentiometer to 1.
Slowly raise the current until the relay picks up.
The relay contacts should switch cleanly with no chatter of the contacts, and be
relatively quite.
The mechanical flag should fall as or just before the contacts operate.
Reduce the current slowly and the relay should reset.
Repeat this procedure several times to ensure consistency, resetting the mechanical
flag after each operation.
Pick up tolerance
±
5% of I
s
Reset value >80% of I
s
Repeat this test for each of the calibration marks of the xI
s
potentiometer
Set the plug bridge to its highest value and repeat above for calibrated values xI
s
potentiometer.
Remove plug from plug bridge and check that the setting is at its highest plug bridge
setting.