8.4 STARTUP MODE
8.4.1 STARTUP MODE OVERVIEW
NOTE
THIS PROCEDURE IS FOR TWO-TERMINAL AND THREE-TERMINAL SYSTEMS.
IT IS ASSUMED THAT WE HAVE A QUIESCENT SYSTEM, THERE ARE NO ALARMS AND THERE
ARE NO TAPPED LOADS IN THE SYSTEM. CURRENT FLOWING INTO ANY TAPS ON THE LINE
WILL AFFECT THE ACCURACY OF THE “DIFF CURR” TEST.
Two tests are performed in Startup Mode to insure that the relay is correctly connected. These are the Phase
Sequence test and the Differential Current test. These tests when used together will insure that PHASE A,
PHASE B, and PHASE C CT connections are correct and that the 3I0 controller connections are properly
phased. Either condition would prevent the unit from operating correctly.
Programming the relay using any remote RS232 connection to the display via APRIL is not recommended while
Startup Mode is active at any of the stations in the system.
8.4.2 PHASE SEQUENCE TEST OVERVIEW
The phase sequence test checks for positive sequence phase rotation by determining if Phase A Current Leads
Phase B current by 120 degrees and Phase B Current Leads Phase C current by 120 degrees and finally that
Phase C current leads Phase A current by 120 degrees. The possibility that the phases are connected in se-
quence but are rotated in some way is addressed by the Differential Current test.
8.4.3 DIFFERENTIAL CURRENT TEST OVERVIEW
The differential current test determines if Phase A Current inputs at all stations are phased correctly relative to
each other. It does this by calculating the arithmetic sum of the Phase A currents at each station. Since the re-
lay operates on the assumption that current going into the protected zone equals current going out, the differ-
ence must always be zero in a balanced system with no faults and all wires connected to the proper inputs. The
possibility that the phases are rotated in some way is addressed by the Differential Current test as well as the
possibility that one station is phase inverted with respect to the other(s).
RFL 9300 RFL Electronics Inc.
October 20, 2004 8 - 22 (973) 334-3100
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