Setting Notes - Siemens 7SC80 Manual

Functions
2.5 Single-Phase Overcurrent Protection
[sj6x-ueb-einph-kesselschut-020926-rei, 1, en_US]
Figure 2-45
2.5.4

Setting Notes

General
Single-phase overcurrent protection is only in effect if address 127 50 1Ph is set to Enabled during configu-
ration. If this function is not required, Disabled is set.
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 pickup value for 50 1Ph-2 PICKUP is set at address 2703, the pickup value for 50 1Ph-1 PICKUP at
address 2706. If only 1 element is required, set the element not required to ∞.
To delay tripping, set the time delay for the 50-2 element at address 2704 50 1Ph-2 DELAY, for the 50-1
element at address 2707 50 1Ph-1 DELAY. If no delay is desired, set the time to 0 s.
The set 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 corresponding 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.
Application as High-Impedance Differential Protection
The application as high-impedance differential protection requires that neutral point current detection is
possible in the system in addition to phase current detection (see example in
sensitive input transformer must be available at device input Ι
overcurrent protection is set at the 7SC80 device for the current at input Ι
The entire function of high-impedance differential protection, however, depends on the interaction of current
transformer characteristics, external resistor R, and voltage across R. The following section gives information
on this topic.
Current Transformer Data for High-impedance Protection
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 approxi-
mately calculated from the rated data of a CT as follows:
[ueb-einph-saetigungsspannung-021026-rei, 1, en_US]
170
Principle of tank-leakage protection
Figure 2-44). Furthermore, a
. In this case, only the pickup value for 1-phase
Ns
.
Ns
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017