Directional Overcurrent Protection 67, 67N
The directional overcurrent protection comprises four elements each for the phase current 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 operates with an inverse tripping time.
Applications
•
The directional overcurrent protection allows the application of multifunctional protection devices
7SJ62/64 also in 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 2.2 Overcurrent Protection 50, 51, 50N,
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.
General
For parallel lines or transformers supplied from a single source (see Figure 2-22), 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 2-22),
directional 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 Figure 2-22.
[ueberstromzeitschutz-bei-paralleltransformatoren-020626-kn, 1, en_US]
Figure 2-22 Overcurrent protection for parallel transformers
2.3
2.3.1
Functions
2.3 Directional Overcurrent Protection 67, 67N
SIPROTEC 4, 7SJ62/64, Manual 85
C53000-G1140-C207-8, Edition 08.2016
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