Ampcontrol Pty Ltd – ABN 28 000 915 542
IPD USER MANUAL
IPDB014 Version 14 – SEP/2020
Uncontrolled Copy - Refer to Ampcontrol Website for Latest Version
APPROVED FOR EXTERNAL DISTRIBUTION
– PROPERTY OF AMPCONTROL PTY LTD
– NOT TO BE REPRODUCED IN PART
APPENDIX B: ADDITIONAL INFORMATION ON CURRENT
PROTECTION
This section of the document will outline the equivalence of the Over Current and Motor Overload
protection schemes employed in the IPD with IEC60255 parts 151 and 8, respectively.
See Section 10 of this manual for basic operational information for the time dependent protection
schemes.
Very Inverse Overcurrent – IEC60255-151
See “vInv” Curves (Drawing IPDB018) and Overcurrent Functional Block Diagram (Drawing IPDB032) in
Appendix A – Drawings.
Over Current protection is implemented in conjunction with the time independent short circuit functions of
the IPD. The overcurrent value (“energising quantity”) used in the IPD is calculated from the highest
current of the three phases measured.
When the measured current exceeds the Full Load Current value (GS), an accumulator begins
incrementing, according to the Very Inverse function:
1
5.13
)(
S
G
G
TMSGt
Where:
t(G) is the operate/trip time,
TMS is the time multiplier,
G/G
s
is the input current ratio relative to the full load current setpoint
Also,
TMS=13.3 x m
Where:
m is the time multiplier setting, programmed in the IPD menu.
The value of G
T
(the lowest value at which the relay is guaranteed to operate) for this function is 110%
relative to G
S
. G
D
(the threshold of independent time operation) is made redundant by the independent
time characteristic of the IPD’s short circuit protection, which has a maximum setting of 10 times G
S
.
NOTE: the function which has been published elsewhere in this document for Over Current is:
Where:
t(sec) is the operate/trip time,
m is the selected time multiplier, and
I is the input current ratio relative to the full load current set point,
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