Reverse Interlocking For Double End Fed Lines - Siemens siprotec SJ62 User Manual

2.3.9

Reverse Interlocking for Double End Fed Lines

Application
Example
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
The forward area is a range of ±86° around the rotated reference voltage V
vector of the negative sequence system current -3I
forward direction.
The directionality feature of the directional overcurrent protection enables the user to
perform reverse interlocking also on double end fed lines using relay element 67-1. It
is designed to selectively isolate a faulty line section (e.g. sections of rings) in high
speed, i.e. no long graded times will slow down the process. This scheme is feasible
when the distance between protective relays is not too great and when pilot wires are
available for signal transfer via an auxiliary voltage loop.
For each line, a separate data transfer path is required to facilitate signal transmission
in each direction. When implemented in a closed-circuit connection, disturbances in
the communication line are detected and signalled with time delay. The local system
requires a local interlocking bus wire similar to the one described in Subsection "Re-
verse Interlocking Bus Protection" for the directional overcurrent protection (Section
2.2).
During a line fault, the device that detects faults in forward (line) direction using the
directional relay element 67-1 will block one of the non-directional overcurrent ele-
ments (50-1, 50-TOC) of devices in the reverse direction (at the same busbar) since
they should not trip (Figure 2-28). In addition, a message is generated regarding the
fault direction. "Forward" messages are issued when the current threshold of the di-
rectional relay element 67-1 is exceeded and directional determination is done. Sub-
sequently, "forward" messages are transmitted to the device located in reverse direc-
tion.
During a busbar fault, the device that detects faults in reverse (busbar) direction using
the directional relay element 67-1 will block one of the non-directional overcurrent el-
ements (50-1, 50-TOC) of devices at the opposite end of the same feeder. In addition,
a "Reverse" message is generated and transmitted via the auxiliary voltage loop to the
relay located at the opposite end of the line.
Figure 2-28 Reverse interlocking using directional elements
2.3 Directional Overcurrent Protection 67, 67N
is in this area, the device detects
2
. If the
ref, rot
102