Woodward
Manual MRIK3-C EN
66
DOK-TD-MRIK3-C Rev. A
7.4
Example of test circuit for MRIK3-C relays without
directional
feature
For testing MRIK3-C relays without directional feature, only current input signals are required. Fig-
ure 7.1 shows a simple example of a single phase test circuit with adjustable current energizing the
MRIK3-C relay under test.
Figure 7.1: Test circuit
7.4.1
Checking the input circuits and measured values
Inject a current, which is less than the relay pickup current set values, in phase 1 (terminals B3-
B4), and check the measured current on the display by pressing the push button <SELECT>. For a
relay with rated current In = 5A, for example, a secondary current injection of 1A should be indi-
cated on the display with about 0.2 (0.2 x In). When parameter Iprim = „SEK“ is set, the indication
is 0.2 x In and at „5“ the indication is 1.00 [A]. The current can be also injected into the other cur-
rent input circuits (Phase 2: terminals B5-B6, Phase 3: terminals B7-B8. Compare the displayed
current value with the reading of the ammeter. The deviation must not exceed 3% or 1% In. By us-
ing an RMS-metering instrument, a greater deviation may be observed if the test current contains
harmonics. Because the MRIK3-C relay measures only the fundamental component of the input
signals, the harmonics will be rejected by the internal DFFT-digital filter. Whereas the RMS-
metering instrument measures the RMS-value of the input signals.
