Ampcontrol Pty Ltd
– ABN 28 000 915 542
OCS USER MANUAL
MAG-182 Version 5
– FEB/2020
Uncontrolled Copy - Refer to Ampcontrol Website for Latest Version
Page 32 of 72
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7.2.2 Operation Summary
The residual voltage protection element is a designated unit for use on installations utilising a high
impedance NER. A definite time operating characteristic is provided with adjustable trip sensitivity and
an adjustable time delay.
When a fault occurs such that the trip level and time delays are exceeded, a trip occurs. The trip acts in
the Main Contactor Relay (MCR) logic and is latched. A residual voltage trip is considered a special
fault and requires a specific reset function to be cleared.
The residual voltage (RV) is displayed as the voltage detected. When the leakage reaches the relative
trip level for the selected time delay a trip occurs.
The Label of the Residual Voltage Protection Element has been modified to easily distinguish the two
types apart. The Residual Voltage Protection Element label has been coloured yellow, as opposed to
the Standard
Protection Element’s orange label. The two protection elements are not mechanically
keyed, which means the relays can be interchanged, however the protection element will remain in a
tripped state and prevent the outlet from being energised. The Residual Voltage Protection Element
does not require the EL CT to be connected and disables the EL CT detection trip.
NOTE
The
Residual Voltage
Protection Element and the
Standard
Protection
Element can be interchanged, however the outlet will
not be able to
energise
.
7.3 Earth Continuity
The earth continuity function tests for the continuity of the earth between the outlet and the machine, via
the pilot in the trailing cable. This is in accordance with AS/NZS 2081: 2011. The pilot is also used to
transfer data when a remote termination unit (RTX) is used to achieve machine communication.
The Protection Element can be configured to operate in either diode or RTX mode. This determines what
terminating device the relay is expecting on the pilot.
NOTE
The RTX will only be recognised by an OCS Protection Element and will
not be seen as a diode by other earth continuity devices
.
CAUTION!
Cable parameters
are important to the correct operation of the Pilot
E/C function. Resistance & capacitance values can
determine the
length of cable that the relay can drive
.
The relay measures the resistance of the pilot - earth loop and the leakage between the pilot and earth
conductors. These measurements are known as the series earth continuity resistance and the shunt
earth continuity resistance, respectively. The shunt measurement ensures that a pilot to earth fault is
detected. If the pilot - earth loop is not healthy (series resistance greater or shunt resistance lower than
their respective trip settings) a trip occurs which in turn opens the MCR to interrupt the main contactor
control circuit.
The trip can be configured as latching or non-latching. This allows the user to determine if the trip is
manually or automatically reset once the pilot - earth loop is healthy.
