Ampcontrol Pty Ltd
– ABN 28 000 915 542
ELV-PRO USER MANUAL
MAG-219 Version 5
– NOVEMBER/2020
Uncontrolled Copy - Refer to Ampcontrol Website for Latest Version
Page 20 of 59
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4.4.8 Removal of ELV-PRO Relay
The ELV-PRO can be removed by simply removing the plugs and dislodging the Analyser from the DIN
rail. Each plug is secured to the ELV-PRO through two screws on either end to prevent the plugs
becoming loose during operation or transport.
4.4.9 ELV-PRO Current Transformer Location and Selection
The ELV-PRO relay has been designed for compliance to AS/NZS 2081:2011 for use on earth fault
limited systems. There are generally two locations where the ELV-PRO may be installed:
1- Core balance protection performs the primary protection in an installation by protecting the outlet
supplying power to a machine. In this application the relay
’s operation time is typically set at
instantaneous. The three power phases are passed symmetrically through the centre of the
toroid. If there is no earth fault present, the vector sum of the currents in a three-phase supply is
zero. If current from any phase flows to earth, the toroid flux becomes unbalanced, allowing the
toroid to produce an output, which in turn trips the relay.
A test current is injected through the window of the toroid to test the operation of the relay.
2- Series neutral protection is the backup protection method and may have an operation time up to
a maximum of 500ms. In this method the neutral to earth connection is passed through the
toroid. An earth fault on any of the phase conductors causes an earth current which returns,
through the neutral, to the star point of the transformer and is detected by the toroid.
A test circuit can connect a test resistor between a phase and earth or inject a current through
the toroid as previously described.
NOTE
The test resistor to earth method is recommended with this type of
protection as this test also proves the neutral to earth connection.
Figure 4-11: ELV-PRO Toroid Installation Examples