Parameter:
81HB2 Inhibit
•
Default setting:
No
High levels of inrush currents into reactive components such as transformers when they are switched in
can result in operation of overcurrent elements. The inrush current can be detected by the 81HBL2
element. This can be configured to inhibit the overcurrent element automatically.
Parameter Value
Description
No
The element is not inhibited by operation of the 81HBL2 element.
Yes
The overcurrent element is inhibited by operation of the 81HBL2 element and
automatically released when the 81HBL2 element resets.
Parameter:
79 Delayed Inhibit
•
Default setting:
No
The autoreclose scheme can be designed such that only instantaneous elements are used for the first
trip(s) of the sequence before reverting to time graded protection. This setting allows the delayed
element to be inhibited during the delayed autoreclose shots and should be left at the default setting of
Off
unless this is required.
Note that function elements are assigned as
Delayed Trips
in the
79 > 79PF
menu.
Parameter Value
Description
No
The element is not inhibited by the autoreclose sequence design.
Yes
The element will be inhibited during any autoreclose shot which is designated as
Delayed
. Incorrect configuration can result in no protection being enabled.
Parameter:
21LB-3P Inhibit
•
Default setting:
No
Where the reverse load flow current may cause incorrect operation of directional overcurrent protection
this function is used to inhibit the 51 function when the measured power factor is within defined limits.
Parameter:
21LB-1P Inhibit
•
Default setting:
No
Where the reverse load flow current may cause incorrect operation of directional overcurrent protection
this function is used to inhibit the 51 function when the measured power factor is within defined limits.
Parameter:
51V Multiplier
•
Default setting: 0.5
For applied voltages above the 51V setting each 51-n phase element operates at its normal current
setting. When the phase control voltage drops below the 51V setting then a current multiplier setting is
applied to that phase.
The
51V Multiplier
will reduce the 51-n pickup current setting for that phase as the multiplier will
have a setting value < 1.
51-n Phase Current
Control Voltage
IA
Vab
IB
Vbc
IC
Vca
Protection and Automation Functions
5.14 51 Time-Delayed Overcurrent – Phase
236
Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019