Directional Overcurrent Protection 67, 67N; General - Siemens siprotec SJ62 User Manual

2 Functions
2.3

Directional Overcurrent Protection 67, 67N

Applications
2.3.1

General

87
With directional time overcurrent protection the phase currents and the ground current
are provided with three elements. All elements may be configured independently from
each other and combined according to the user's requirements.
High-current elements 67-2 and overcurrent element 67-1 always operate with definite
tripping time, the third element 67-TOC, operates with inverse tripping time.
• The directional overcurrent protection allows the application of multifunctional pro-
tection devices 7SJ62/63/64 to systems where coordination protection depends on
knowing both the magnitude of the fault current and the direction of energy flow to
the fault location.
• The time overcurrent protection (non-directional) described in Section 2.2 may
operate as overlapping backup protection or may be disabled. Additionally, individ-
ual 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 time over-
current protection has to be supplemented by the directional criterion.
For parallel lines or transformers supplied from a single source (Figure 2-17), the
second feeder (II) is opened on occurrence of a fault in the first feeder (I) 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 (Figure 2-17) directional overcurrent
protection is applied. Be careful that the "Forward" direction of the protective 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 Figure 2-17.
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015