Acceptance Tests; Introduction; Visual Inspection; Insulation - GE MLJ1000 Manual

7. ACCEPTANCE TESTS

7.1 INTRODUCTION

Given the digital nature of this relay, in most occasions making sure that the relay measures correctly
will guarantee proper performance, since all of the logic of measurement and protection is
implemented by means of programming. In order to do this, the voltages in the line and bus need only
to be measured with a multimeter and make sure they coincide, within the specified accuracy, with the
reading indicated on the screen.
A phasemeter should be used in order to check the correct measurement of the voltage and phase
difference (since the voltage difference is measured vectorially) if angle and voltage is required to be
tested.
Finally, with an accurate and stable frequency meter the line and bus voltage frequency can be
measured the difference between them calculated, which should coincide with the measurement that
appears on the relay screen.

7.2 VISUAL INSPECTION

Check the nameplate stamping to ensure that the model number and rating of the relay agree with the
requisition. The relay should also be checked for scratches, dents, or loose components that may have
been caused from negligent transport.

7.3 INSULATION

Due to the presence of capacitors for immunizing the relay from external interference, during the
insulation test, approximately 7 mA for each capacitor is consumed. In the event that the apparatus
used to carry out the insulation test does not permit such a consumption, the test will be done by
grouping less terminals.
These tests are only carried out on new relays. A new relay means one that has not been in service,
whose expedition date is not more than a year old, and one which has been stored in suitable
conditions so as to prevent any deterioration.
NOTE : It is very important that the strip connected to the ground terminal on the back of the relay is
tightened at all time. If this strip is loose, harmful transients could occur when the insulation
test voltages are performed.
Short-circuit all the terminals except A11, A12, B11 and B12. Slowly apply 2000 V of alternating current
to the chassis and then slowly reduce it back down to 0 V.

7.4 SYNCHRONISM UNIT

For these tests, two independent voltage generators, adjustable in amplitude and phase, should be
available.
In order to carry out these tests the synchronism unit should be activated and the undervoltage unit
deactivated. This is done by putting the 4-1 setting on ON and settings 4-2, 4-3 and 4-4 on OFF.
Due to the complexity of the necessary equipment, it is not recommended to carry out the frequency
difference test. To check that the measurement is correct, the slip on the readout menu (readout F5) is
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