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2 Functions
116
7ST6 Manual
E50417-G1176-C251-A3
Definite-time
Backup Time Over-
current Protection
The defrosting protection is provided with a two-stage definite-time overcurrent pro-
tection as backup protection. This backup protection is switched on and off together
with the differential protection. The stages operate with the fundamental wave compo-
nent of the defrosting current I. The stages generate separate indications for pickup
and tripping. The figure below shows the logic diagram of the back-up protection.
Figure 2-35
Pick-up and tripping logic of the backup O/C protection of the defrosting protection
Operational Mea-
sured Values
In some models (3xI, 3xU) the defrosting current Ix is always displayed as an opera-
tional measured value. It can be shown as a primary, secondary or percent value.
If the defrosting protection is configured, the differential current
„Id =“
(FNo. 13968)
calculated by the differential protection, and the restraint current
„Ir =“
(FNo.
13969) can be displayed as percent values.
Fault Recording
In some models (3xI, 3xU) the defrosting current Ix is always recorded by the fault re-
cording function.
If the defrosting protection is configured, the current Ix and the internally calculated
currents
„Id =“
(differential current) and
„Ir =“
(restraint current) are also re-
corded by the fault recording function.
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