Siemens siprotec SJ62 User Manual page 134

Use as Tank
Leakage Protection
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
If performance makes it necessary to switch several varistors in parallel, preference
should by given to types with a flat characteristic to avoid asymmetrical loading. We
therefore recommend the following types from METRSIL:
600A/S1/S256 (k = 450, β = 0.25)
600A/S1/S1088 (k = 900, β = 0.25)
The pickup value (0.1 A or 0.05 A in the example) is set in address 2706 50 1Ph-1
PICKUP in the device. The 50-2 element is not required (address 2703 50 1Ph-2
PICKUP = ∞ ).
The trip command of the element can be delayed in address 2707 50 1Ph-1 DELAY.
This delay is normally set to 0.
If a higher number of CT's is connected in parallel, e.g. as busbar protection with
several feeders, the magnetizing currents of the transformers connected in parallel
cannot be neglected any more. In this case, the magnetizing currents at the half knee-
point voltage (corresponds to the setting value) have to be summed up. These mag-
netizing currents reduce the current through the resistor R. Therefore the actual
pickup value will be correspondingly higher.
The use as tank leakage protection requires that a sensitive input transformer is avail-
able at the device input I
current protection is set at the 7SJ62/63/64 device for the current at input I
The tank leakage protection is a sensitive overcurrent protection which detects the
leakage current between the isolated transformer tank and ground. Its sensitivity is set
in address 2706 50 1Ph-1 PICKUP. The 50-2 element is not required (address 2703
50 1Ph-2 PICKUP = ∞ ).
The trip command of the element can be delayed in address 2707 50 1Ph-1 DELAY.
It is normally set to 0.
Note
In the following Setting overview addresses 2703 and 2706 are valid for a highly sen-
sitive current measuring input independently of the nominal current.
2.5 Single-Phase Overcurrent Protection
/I . In this case, only the pickup value for single phase over-
N NS
/I .
N NS
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