12
Note that shorting switches shown on the relay diagram are fitted internally across
the relevant case terminals and close when the module is withdrawn. It is essential
that such switches are fitted across all CT circuits.
If a test block type MMLG is provided, the connections should be checked to the
scheme diagram, particularly that the supply connections are to the ‘live’ side of the
test block (coloured orange) and with terminals allocated odd numbers (1, 3, 5, 7,
etc.).
2.4.2
Earthing
Ensure that the case earthing connection above the rear terminal block, is used to
connect the relay to a local earth bar.
2.4.3
Insulation
The relay, and its associated wiring, may be insulation tested between:
– all electrically isolated circuits
– 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.
2.4.4
Terminal allocation
Terminals of the relay are normally allocated as below, but reference should always
be made to the relevant diagram.
a) Single pole relays
Normally open contacts 1, 3 and 2, 4.
AC current input – 27, 28.
b) Triple pole relays
Normally open contacts 1, 3 and 2, 4.
The contacts are normally connected in parallel for the three phases but a version
of the relay having contacts brought out separately is available.
AC current inputs – 23, 24 : 25, 26 : 27, 28.
2.4.5
Instructions to ensure that the relay can be commissioned at the specific settings for
the application.
It is only necessary to check the relay at the setting on which it is to be used.
The relay must not be used at any setting other than that for which the setting has
been calculated.
2.4.6
Test equipment required
1 – Secondary injection test equipment capable of providing an ac voltage supply of
up to at least 120% of the relay setting.
1 – Multifinger test plug type MMLB 01 for use with test block type MMLG
if fitted.
1 – Miniature split plug type MMLB 03 to fit relay plug bridge.
3 – Calibrated multimeters 0 – 10A ac, 0 – 400V ac
1 – Set primary injection testing equipment.
