Areva MiCom P120, Technical Manual

Page: 559 / 668

Commissioning and Maintenance P12x/EN CM/A96
MiCOM P120/P121/P122/P123
Page 5/18
3. PRODUCT VERIFICATION TESTS
3.1 Allocation of terminals
It is necessary to consult the appropriate wiring diagram provided in the APPENDIX 1 of the
Technical Guide whilst observing the various polarities and ground/earth connection.
3.2 Electrostatic discharge (ESD)
Before any handling of the module (active part of the relay), please refer to the
recommendations in User guide of this Technical Guide.
3.3 Visual inspection
Carefully examine the relay to see if there has been any possible deterioration following
installation.
Check if the external wiring corresponds to the appropriate relay diagram or the assembly
diagram. The reference number of the relay diagram is indicated on a label situated under
the upper flap of the front panel.
When the relay is withdraw from its case, use a continuity tester to check if the current short-
circuits (phases and earth CT's) between the terminals indicated on the wiring diagram are
closed.
3.4 Earthing
Check if the earth connection of the case situated above the rear terminal block is used to
connect the relay to a local earth bar. With several relays present, make sure that the copper
earth bar is properly installed for solidly connecting the earthing terminals of each case.
3.5 Current transformers (CT's)
DANGER:
NEVER OPEN CIRCUIT THE SECONDARY CIRCUIT OF A CURRENT TRANSFORMER
SINCE THE HIGH VOLTAGE PRODUCED MAY BE LETHAL AND COULD DAMAGE
INSULATION.
3.5.1 Use of a Core CT for earth faults.
If a core CT is used to detect earth faults, prior to any test, the user must check the following
points:
MV or HV cable screens and core CT,
No current flow through the MV or HV cables,
Orientation of the core CT (P1-S1, P2-S2)
3.5.1.1 Cable shields and core CT
When mounting a core CT around electric cables, check the connection to the earth of the
cable shields. It is vital that the earth cable of the shield moves in the opposite direction
through the core CT. This cancel the currents carried by the cable shields through the core
CT.