Arcteq AQ-S215, Instruction Manual

Page: 246 / 289

The ARON input connection can measure the load symmetrically despite the fact that one of the CTs is
missing from the installation. Normally, Phase 2 does not have a current transformer installed as an
external fault is much more likely to appear on Lines 1 or 3.
A fault between Line 2 and the earth cannot be detected when the ARON input connection is used. In
order to detect an earth fault in Phase 2, a cable core CT must be used.
7.4 Trip circuit supervision (95)
Trip circuit supervision is used to monitor the wiring from auxiliary power supply, through the IED's
digital output, and all the way to the open coil of the breaker. It is recommended to supervise the health
of the trip circuit when breaker is closed.
Trip circuit supervision with one digital input and one non-latched trip output
The figure below presents an application scheme for trip circuit supervision with one digital input and a
non-latched trip output. With this connection the current keeps flowing to the open coil of the breaker
via the breaker's closing auxiliary contacts (52b) even after the circuit breaker is opened. This requires
a resistor which reduces the current: this way the coil is not energized and the relay output does not
need to cut off the coil's inductive current.
Figure. 7.4 - 147. Trip circuit supervision with one DI and one non-latched trip output.
Note that the digital input that monitors the circuit is normally closed, and the same applies to the alarm
relay if one is used. For monitoring and especially trip circuit supervision purposes it is recommended
to use a normally closed contact to confirm the wiring's condition. An active digital input generates a
less than 2 mA current to the circuit, which is usually small enough not to make the breaker's open coil
operate.
A AQ Q-S215 -S215
Instruction manual
Version: 2.04
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