8.4.4.3 TROUBLE SHOOTING THE PHASE SEQUENCE TEST
In the process of commissioning the relay the first test that should be run and should pass is the Phase Se-
quence Test. This is parameter number 3 and the display will show SEQ TEST as the top line message. Essen-
tially, the relay will measure the current flowing on Phase A Phase B Phase C and 3I0. This corresponds to the
parameter numbers 5, 6, 7, and 8 “LOC IA”, “LOC IB”, “LOC IC”, and LOC3I0.
The current present should be at least 1 amp per phase and there should be no current on 3I0. (unbalances
which cause currents on 3I0 of more than 0.5 amps RMS will cause the phase sequence test to fail).
The Phase sequence test determines if the phases are in the proper sequence and balanced. If the phases are
in sequence and 120 degrees out of phase then the display will show LP for local unit passed the test, 1P for
remote 1 unit passed the test ( and 2P for remote 2 unit passed the test in a 3 terminal system). If any of the
tests fail, the phases are improperly sequenced or unbalanced. This means that one or more of the Phases are
connected to the wrong inputs, the wires may be inverted (i.e. backwards) or there is current on 3I0.
If the phase sequence test fails check the 3I0 current to determine if the system is unbalanced.
To check if current is present on ground, press [ENT] repeatedly until the display shows “LOC 3I0” on the first
line. The second line should measure 0.00 amps.
To check if current is present on the other phase inputs, press [ENT] repeatedly until the message “LOC IA”,
“LOC IB”, or “LOC IA” appears. Each should display at least 1.00 amp.
Remote stations can also be inspected using the display, however it is recommended that the Phase Sequence
test be run locally at each station since shunting PHASE A current is not possible from a remote relay. Remote
station(s) can be inspected for Phase A current, however this is intended to help trouble shoot the differential
current test and not the Phase Sequence test.
If all the stations show at least 1.00 amps current flowing on A, B, and C and no current on 3I0, then there is a
problem with the connection of phases to the relay.
Verify that the phases are connected to the correct inputs and are not inverted, and check for current on 3I0.
NOTE
ALL OF THESE PROBLEMS SHOULD BE CORRECTED BEFORE CONTINUING TO THE NEXT
STEP OF THE PHASE SEQUENCE TEST.
By pressing the [ENT] key you can step through the values of the different currents to verify that phase current
is still flowing and that no current is in 3I0. Measuring the phase angle between phases is done internal to the
unit and can not be displayed in a meaningful way, however minor fluctuations in the difference in phase be-
tween adjacent phases will not result in a failed test.
One reason that the phase sequence test would fail at this point in the procedure is that a pair of inputs has
been swapped.
RFL 9300 RFL Electronics Inc.
October 20, 2004 8 - 28 (973) 334-3100
To Next Page
Loading...