Directional Overcurrent Protection 67, 67N; General - Siemens 7SC80 Manual

2.3

Directional Overcurrent Protection 67, 67N

Directional time overcurrent protection comprises three definite elements and several inverse elements for the
phase currents and the ground currents. All elements are independent of each other and can be combined as
desired.
The high-current elements 67-2 and 67-3 and the 67-1 overcurrent element always operate with a definite
tripping time, the fourth element 67-TOC always operates with an inverse tripping time.
Applications
•
The directional overcurrent protection allows the 7SC80 Feeder Protection and Recloser Controller to be
used also in power systems where protection coordination depends on knowing both the magnitude of
the fault current and the direction of power flow to the fault location.
•
The non-directional overcurrent protection described in Section
51N may operate as overlapping backup protection or may be disabled. Additionally, individual elements
(e.g. 67-2 and/or 67N-2) may be interconnected with the directional overcurrent protection.
•
For parallel lines or transformers supplied from a single source, only directional overcurrent protection
allows selective fault detection.
•
For line sections supplied from two sources or in ring-operated lines, the overcurrent protection has to be
supplemented by the element-specific directional criterion.
2.3.1

General

For parallel lines or transformers supplied from a single source
on occurrence of a fault in the first feeder (Ι) if tripping of the breaker in the parallel feeder is not prevented
by a directional measuring element (at B). Therefore, where indicated with an arrow
overcurrent protection is applied. Please ensure that the "forward" direction of the protection element is in the
direction of the line (or object to be protected). This is not necessarily identical with the direction of the
normal load flow, as shown in
[ueberstromzeitschutz-bei-paralleltransformatoren-020626-kn, 1, en_US]
Figure 2-23
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
Figure 2-23.
Overcurrent protection for parallel transformers
2.3 Directional Overcurrent Protection 67, 67N
2.2 Overcurrent Protection 50, 51, 50N,
(Figure 2-23), the second feeder (ΙΙ) is opened
(Figure
Functions
2-23), directional
111