phase polarizing voltage. This measurement is greatly simplified if the polarizing reference voltage is set to 0°
and the current phase angle is measured with respect to this reference.
Alternatively, the instrument can be checked at the 4 points marked a, b, c & d on Figure 9-10 only.
Forward Reverse
Lag (point C) Lead (point A) Lead (point B) Lag (point D)
Pick-up Drop-off Pick-up Drop-off Pick-up Drop-off Pick-up Drop-off
MTA MTA -85 MTA +85 MTA -85 MTA -85
Phase A
Phase B
Phase C
[dw_7SR5_function67FunctionalTests, 1, en_US]
Figure 9-10 Directional Phase Fault Boundary System Angles
5. With the instrument reading Fwd or Rev, reduce the voltage until the element resets. Record the minimum
phase-phase operate voltage.
Minimum Voltage Setting
Measured
2 Out Of 3 Logic
Ensure that at least 1 Phase Overcurrent element is set to Directional. Apply balanced nominal
voltage. Apply current at a level above the 50/51 setting on phase A only at the characteristic angle for
forward operation, normally 45° lagging. Ensure no Directional Phase Overcurrent element opera-
tion occurs. Note that non-directional Phase Overcurrent and non-direction Earth Fault elements may
operate unless disabled.
Repeat the test with phase A current as above but also with equal current in the B phase at 180° to that in the
A phase.
Functional Tests
9.10 Protection Functional Tests
444 Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019
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