Multilin PROTECT 4A-120, Instruction Manual

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4. RELAY TESTING
4.1 COMMISSIONING TESTS
Prior to applying power at a new installation, system operation
can be verified by injecting current through the phase CTs. If a
3 phase current injection set is available it would be connected
as shown in figure 2-5 in place of the 3 phase supply and using
a short between the 3 phases in place of the motor. A short
must be placed across the ground fault CT terminals when do-
ing current tests or nuisance ground fault trips will occur.
When a single phase injection set is used, the sensing circuitry
sees an unbalance condition as shown in figure 5-2 and ex-
plained in the theory of operation section 5. To make the single
phase input appear to the Protect 4A like a 3 phase input, it is
necessary to temporarily connect a capacitor (observe capaci-
tor polarity) across the two test points on the terminal board as
shown in figure 4.1. Larger capacitors may be substituted. The
actual value is not critical. This shifts the measured values so
that all current readings should be multiplied by a factor of 1.5
to set the equivalent 3 phase current.
Figure 4-1 shows a suitable setup for single phase testing. Fig-
ure 4-2 shows how to build a 100 amp current source if a
commercial unit is not available. All current values can be in-
creased by winding n turns in place of the single turn shown
and multiplying current readings by n.
To verify that the internal relay circuitr y is operating press the
front panel test button. When the test button is pressed, the
fault indicators operate and the motor contactor should trip, Tests
for each protection mode are outlined in the sections that fol-
low.