Micom P634 - Inverse-Time Overcurrent Protection (Function Groups IDMT1 to IDMT3); Enabling or Disabling IDMT Protection

3.24 Inverse-time Overcurrent Protection (Function Groups
IDMT1 to IDMT3)
The P634 features an inverse-time overcurrent protection function (IDMT
protection) for up to three transformer ends. The measured variables to be
monitored by the respective IDMT function are selected by a setting parameter.
These values can also be quantities formed by summation of current values from
two user-selected transformer ends.
Phase current values as well as negative-sequence and residual current
measured values are monitored.
The function group IDMT1 will serve as an example to illustrate the operation of
the IDMT protection functions. The same will apply to function groups IDMT2 and
IDMT3.
64Z5027A
IDMT1:
Select. meas. input
[ 019 106 ]
0
1
2
4
3
IA,y
IB,y
IC,y
IN,y
0: End a
1: End b
2: End c
4: End d
3: Current summation
40
IA,a
IB,a
IC,a
IN,a
IA,b
IB,b
IC,b
IN,b
IA,c
IB,c
IC,c
IN,c
IA,d
IB,d
IC,d
IN,d
ΣIA
ΣIB
ΣIC
ΣIN
Fig. 3-115: Selection of measured variables for IDMT protection
3.24.1 Enabling or Disabling IDMT Protection
IDMT protection can be enabled or disabled via setting parameters. Moreover,
enabling can be carried out separately for each parameter subset.
3 Operation
P634
P634/EN M/R-42-A // P634‑311‑653 3-161