Manual MRI3 GB
Woodward
DOK-TD-MRI3 Rev.A
49
6.4.7 Example of a test circuit for MRI3 relay with directional feature
Figure 6.2: Test circuit
For testing relays with directional feature, current and voltage input signals with adjustable phase
shifting are required. Figure 6.2 shows an example of a single phase test circuit with adjustable vol-
tage and current energizing the MRI3 relay under test.
For testing a relay with directional feature, one of the input energizing quantity (voltage) shall be
applied to the relay with a constant value within its effective range. The other input energizing
quantity (current) and phase angle shall be appropriately varied.
MRI3 is a three phase directional time overcurrent relay with relay connection angle of 0°. The re-
lay input currents and their corresponding reference voltages are shown in Table 6.1 (also refer to
4.3):
If the single phase test circuit as illustrated in
Figure 6.2 is applied to test the directional feature of the relay and the current source is connected
to phase 1 current input (B3/B4), then the voltage source should be connected to relay terminals
A5/A7.
In order to test the directional feature, all thresholds should first be set to “EXIT”. Then a test vol-
tage equivalent to the rated voltage is connected to terminals A5/A7 and a current of 1 x In is im-
pressed upon the current inputs B3/B4.
It is now possible to read and check all measured values in accordance with Table 6.1. If the phase
position is changed, the values I
Q
and I
P
change. If the angle is changed by 90°, for example, the
measured value for current input I1 must be 1.0 for IP and ±0.0 for I
Q
.