D0920 Arc-Detection Unit Rev. 0-D-070616
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• 5/18
1 INTRODUCTION
1.1 General
The D0920 Arc Detection Unit is a high-speed arc-detection device for electrical power-distribution
systems. The D0920 requires a 230 Vac supply and supports up to three point sensors (A0220)
mounted in a switchboard.
On the occurrence of an arc fault, the D0920 detects the fault and pulses the trip output in less
than 1 ms. The fast trip time reduces the risk of personal injury and equipment damage.
The D0920 is typically supplied from the switchboard main power. The AC voltage may fail when
an arc fault develops. The D0920 uses energy stored in an internal capacitor to trip the circuit
breaker. The storage capacitor is an extremely long-life electrolytic capacitor with a specified life
time of more than 30 years at an ambient temperature of 50°C (121°F). The trip energy stored is
sufficient for circuit breakers with a 220/250 Vdc shunt trip coil.
The D0920 has one output indication relay with an isolated normally-open contact, and one output
indication relay with an isolated normally-closed contact. Additional features include power and
trip indication, test mode, and sensitivity adjustment.
NOTE: Dangerous voltage is present at the storage capacitor (terminals 4, 7, and 8) even after the
relay has been disconnected from the supply voltage. The capacitor has a self-discharge circuit
which will discharge it to a safe voltage level within two minutes after disconnection from the
supply voltage.
1.2 A0220 Point Sensor
The A0220 point sensor is a photoelectric sensor with a sensitivity range of 180 degrees. It has a
transparent polycarbonate enclosure that is IP65 rated. Each point sensor includes 10 m (33 ft) of
shielded 2-wire, 24 AWG (0.2 mm
2
) cable. The cable length can be extended to a maximum of
50 m (164 ft), however use shielded 2-wire, 20 AWG (0.5 mm
2
) cable.
FIGURE 1. D0920 Arc Detection Unit.
FIGURE 2. A0220 Point Sensor.
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