Ampcontrol Pty Ltd
– ABN 28 000 915 542
HPB USER MANUAL
HPBB012 Version 9
– March/2020
Uncontrolled Copy - Refer to Ampcontrol Website for Latest Version
Page 23 of 61
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7
CURRENT RELATED FUNCTIONS
7.1 Basic Over-Current Protection
NOTE
The HPB 6.6kV Relay uses 1000:1 CTs.
The HPB 22 & 11kV Relay uses 2000:1 CTs.
Two current transformers are used to measure the three line currents. The measured currents are used
to implement the following protection functions:
a. Over-current
b. Short Circuit
c. Phase Current Balance
Full load settings cover a range from 7.5 Amps to 464 Amps for the HPB 6.6kV and 15 Amps to 928
Amps for the HPB 22kV. A current range and current multiplier are utilised to select and store the full
load current value in the non-volatile memory. This forms the basic reference level for the over-current
protection functions.
The current range is selectable in 4 Amp increments between 60 and 116 Amps. The current multiplier is
selectable at 1/8, 1/4, 1/2, 1, 2, and 4 times for the HPB 6.6kV and at 1/4, 1/2, 1, 2, 4, and 8 times for the
HPB 22kV. The selected Range and Multiplier combine to give the basic level.
Example
To obtain a full load current of 152 Amps select a current range of 76 Amps and a multiplier of 2.
Two curve types can be selected. A selected time multiplier modifies the basic trip time characteristic.
This multiplier is selected from 0.05 times to 1.0 times.
The instantaneous current in each of the three phases can be displayed on the display module (level 5,
position 1). The display is expressed as a percentage of the selected full load current and reads between
0 and 999% (i.e. up to 9.99 times full load current).
When the load current exceeds the full load current level, a trip accumulator is incremented at a rate
dependant on the current. When this accumulator reaches 100%, an over-current trip occurs.
The trip accumulator can be viewed on the HDM Remote Display Module (level 5, position 2). This may
be useful to determine how close an outlet gets to trip condition during start up. If the accumulator
reached almost 100% as the load gets away then this may indicate that the over-current settings are too
low. Conversely, if the trip accumulator only builds up slightly on a heavy start, then the over-current
setting may be set too high.
If an over-
current trip occurs, the “OC” LED flashes, and the “OC” open collector output switches on to
provide remote monitoring if required.
Following an over-current trip, the following conditions must be met to affect a reset:
a. The trip accumulator must be less than 80%.
b.
The HPB Relay’s reset input must be closed.
7.2 Over-Current Characteristic
The current-time trip characteristics can be selected as either Very Inverse, or Extremely Inverse,
corresponding to the “OC Type” value or “vlnv” or “xlnv”. The drawing, Very Inverse Over-current Curves,
