Setting Notes - Siemens siprotec SJ62 User Manual

2.5.4

Setting Notes

General
Use as High-imped-
ance Protection
Current Transform-
er Data for High-im-
pedance Protection
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
Single-phase time overcurrent protection can be set ON or OFF at address 2701 50
1Ph.
The settings are based on the particular application. The setting ranges depend on
whether the current measuring input is a sensitive or a normal input transformer (see
also „Ordering Information" in Appendix A.1).
In case of a normal input transformer, set the pickup value for 50 1Ph-2 PICKUP in
address 2702, the pickup value for 50 1Ph-1 PICKUP in address 2705. If only one
element is required, set the one not required to ∞.
In case of a sensitive input transformer, set the pickup value for 50 1Ph-2 PICKUP
in address 2703, the pickup value for 50 1Ph-1 PICKUP in address 2706. If only
one element is required, set the one not required to ∞.
If you need a trip time delay for the 50-2 element, set it in address 2704 50 1Ph-2
DELAY, for the 50-1 element in address 2707 50 1Ph-1 DELAY. With setting 0 s no
delay takes place.
The selected times are additional time delays and do not include the operating time
(measuring time, etc.) of the elements. The delay can also be set to ∞; the correspond-
ing element will then not trip after pickup, but the pickup is reported.
Special notes are given in the following for the use as high-impedance unit protection
and tank leakage protection.
The use as high-impedance protection requires that starpoint current detection is pos-
sible in the system in addition to phase current detection (see example in figure 2-39).
Furthermore, a sensitive input transformer must be available at device input I
this case, only the pickup value for single-phase overcurrent protection is set at the
7SJ62/63/64 device for the current at input I
The entire function of high-impedance protection is, however, dependent on the inter-
action of current transformer characteristics, external resistor R and voltage across R.
The following section gives information on this topic.
All current transformers must have an identical transformation ratio and nearly equal
knee-point voltage. This is usually the case if they are of equal design and identical
rated data. The knee-point voltage can be approximately calculated from the rated
data of a CT as follows:
V Knee-point voltage
KPV
R Internal burden of the CT
I
P Rated power of the CT
Nom
I Secondary nominal current of CT
Nom
ALF Rated accuracy limit factor of the CT
2.5 Single-Phase Overcurrent Protection
/I .
N NS
/I . In
N NS
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