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SE-703 Earth-Leakage Monitor Rev. 12-B-092117
1. GENERAL
The SE-703 is a microprocessor-based earth-leakage
monitor for ac power supply systems incorporating earth-
fault current limitation. The SE-703 has two isolated
Form-C relays 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 button, 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 (CT). The
trip level of the earth-leakage circuit is digital-switch
selectable from 25 to 500 mA. Trip time is digital-switch
selectable from INST (instantaneous) to 500 ms.
Ordering option SE-703-0x-00 is AS/NZS 2081:2011
compliant. Its output relays operate in the fail-safe mode for
undervoltage applications.
Ordering option SE-703-0x-02 is AS/NZS 2081:2002
compliant. Its output relays operate in the fail-safe or non-
fail-safe mode for undervoltage or shunt-trip applications.
2. OPERATION
2.1 CONFIGURATION-SWITCH SETTINGS
See Figs. 1A, 1B and 1C.
2.1.1 RELAY OPERATING MODE
The output relays for ordering option SE-703-0x-00
operate only in the fail-safe mode for undervoltage
applications.
The output relays for ordering option SE-703-0x-02
operate in the fail-safe or non-fail-safe mode for
undervoltage or shunt-trip applications.
Switch 1 is used to set the operating mode of the output
relays (for SE-703-0x-02 only).
In the fail-safe mode, the output relays energize when
the earth-leakage circuit is not tripped. 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 relays energize
when a ground-fault trip occurs. 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 button is
pressed or the remote-reset terminals (6 and 7) are
momentarily connected.
The reset circuit responds only to a momentary closure
so that a jammed or shorted button will not prevent a trip.
The front-panel RESET button is inoperative when the
remote-reset terminals are connected.
2.2.4 TEST
The TEST button is used to test the earth-leakage
circuit, the indication, and the output relays. When the
TEST button 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 relays
will operate.
2.3 FRONT-PANEL INDICATION
2.3.1 POWER
The green LED labelled PWR indicates presence of
supply voltage.
2.3.2 TRIP
The red LED labelled 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 labelled CT indicates that an EFCT-series
sensor is connected.
