GE MFAC 14 User Manual page 13

2.2.1 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 0–10 amp ac, 0–400 volt ac.
1 – Set primary injection testing equipment.
2.2.2 General
If the relay is wired through an MMLG test block it is recommended that all
secondary injection tests should be carried out using this block.
Ensure that the main system current transformers are shorted before isolating the
relay from the current transformers in preparation for secondary injection tests.
DANGER:
DO NOT OPEN CIRCUIT THE SECONDARY CIRCUIT OF A CURRENT
TRANSFORMER SINCE THE HIGH VOLTAGE PRODUCED MAY BE LETHAL
AND COULD DAMAGE INSULATION.
When type MMLG test block facilities are installed, it is important that the sockets in
the type MMLB 01 test plug, which correspond to the current transformer secondary
windings, are LINKED BEFORE THE TEST PLUG IS INSERTED INTO THE TEST
BLOCK. Similarly, a MMLB 02 single finger test plug must be terminated with an
ammeter BEFORE IT IS INSERTED to monitor CT secondary currents.
It is assumed that the initial preliminary checks have been carried out.
2.2.3 Relay CT shorting switches
With the relay removed from its case, check electrically that the CT shorting switch
is closed.
2.2.4 Secondary injection testing
Connect the circuit as shown in Figure 1 and ensure that the current transformer
primary is open circuit and that if any earthing connections are fitted, they do not
short out the primaries of any current transformers.
Increase the voltage until the relay just operates.
Note the current in the relay (this can be done using the miniature split plug
inserted into the appropriate position of the plug bridge connected to an ammeter).
It should be approximately 38mA at setting.
Note also the voltage at which the relay operates which should correspond to the
setting V
R
operation will be given on ammeter A1. This test should be repeated for each pole
of the relay.
Drop off/Pick up ratio.
Check that this ratio is greater than 50%.
of the relay with a tolerance of ±10%. The total secondary current for
13