Startco Engineering Ltd. Page 1
SE-703 Earth-Leakage Monitor Rev. 6
Pub. SE-703-M, March 4, 2008.
1. GENERAL
The SE-703 is a microprocessor-based earth-leakage
monitor for ac power supply systems incorporating earth-
fault current limitation. Its output relay can operate in
the fail-safe or non-fail-safe mode for undervoltage or
shunt-trip applications. The SE-703 has one output relay
with isolated normally open and normally closed
contacts for use in independent control circuits.
Additional features include LED trip and power
indication, latching trips with front-panel and remote
reset, trip memory, test switch, self diagnostics, 0 to 5-V
analog output, CT verification with LED indication,
digital selector switches, and switch-selectable
algorithms for fixed-frequency or variable-frequency
applications.
Earth-leakage current is sensed by an EFCT-series
core-balance, earth-fault current transformer. The trip
level of the earth-leakage circuit is digital-switch
selectable from 25 to 500 mA. Trip time is digital-
switch selectable from 50 to 500 ms.
The SE-703 is AS/NZS 2081:2002 compliant.
2. OPERATION
2.1 CONFIGURATION-SWITCH SETTINGS
See Fig. 1.
2.1.1 RELAY OPERATING MODE
Switch 1 is used to set the operating mode of the
output relay. In the fail-safe mode, the output relay
energizes when the earth-leakage circuit is not tripped.
In the fail-safe mode, non-volatile memory retains the
trip status of the SE-703. If tripped, and the supply
voltage is cycled, the SE-703 will remain tripped, with
the trip relay de-energized and the TRIP LED on, until
reset.
In the non-fail-safe mode, the output relay energizes
when an earth-leakage trip occurs. In the non-fail-safe
mode, trip status is not retained in non-volatile memory.
2.1.2 FILTER SELECTION
Switch 2 is used to select the filtering algorithm for a
fixed-frequency (50/60 Hz) or variable-frequency
application. The FIXED FREQUENCY setting uses a
DFT filter that allows lower trip levels to be used by
rejecting harmonics that can cause nuisance tripping.
The VARIABLE FREQUENCY setting uses a peak-
detection algorithm with a wider bandwidth for fault
detection in variable-frequency drive applications.
2.2 FRONT-PANEL CONTROLS
2.2.1 EARTH-LEAKAGE TRIP LEVEL
The LEVEL (mA) selector switch is used to set the
earth-leakage trip level. For earth-leakage detection, the
earth-leakage trip level must be substantially below the
prospective earth-fault current. To avoid sympathetic
tripping, the trip level must be above the charging
current of the protected feeder.
2.2.2 EARTH-LEAKAGE TRIP TIME
The SE-703 has a definite-time trip characteristic. The
TIME (ms) selector switch is used to set the earth-
leakage trip time for coordination with upstream and
downstream earth-fault devices. Coordination requires
the same trip level for all earth-leakage devices in a
system and the trip time to progressively increase
upstream. The amount of equipment removed from the
system will be a minimum if the first earth-leakage
device to operate is the one immediately upstream from
the fault.
2.2.3 RESET
A trip remains latched until the RESET switch is
pressed or the remote-reset terminals (6 and 7) are
momentarily connected. In the non-fail-safe relay
operating mode, cycling the supply voltage will also
reset the SE-703.
The reset circuit responds only to a momentary closure
so that a jammed or shorted switch will not prevent a
trip. The front-panel RESET switch is inoperative when
the remote-reset terminals are connected.
2.2.4 TEST
The TEST switch is used to test the earth-leakage
circuit, the indication, and the output relay. When the
TEST switch is pressed for one second, a test signal is
applied to the earth-leakage-detection circuit, the circuit
will trip, the TRIP LED will light, and the output relay
will operate.
2.3 FRONT-PANEL INDICATION
2.3.1 POWER
The green LED labeled PWR indicates presence of
supply voltage.
2.3.2 TRIP
The red LED labeled TRIP indicates a trip. A solid red
LED indicates an earth-leakage trip and a flashing LED
indicates a trip initiated by a CT fault. Two fast flashes of
the TRIP LED indicate a diagnostic trip. See Section 2.5.
2.3.3 CT VERIFICATION
The green LED labeled CT indicates that an EFCT-
series sensor is connected.
