Table of Contents
Advertisement
2.7
Teleprotection for Distance Protection (optional)
2.7.1
General
Purpose of
Faults which occur on the protected line, beyond the first distance zone, can only be
Teleprotection
cleared selectively by the distance protection after a delay time. On line sections that
are shorter than the smallest sensible distance setting, faults can also not be selec-
tively cleared instantaneously.
To achieve non-delayed and selective tripping on 100 % of the line length for all faults
by the distance protection, the distance protection can exchange and process infor-
mation with the opposite line end by means of signal transmission systems. For this
purpose, the device has signal send outputs and receive inputs.
As an alternative, digital communication lines can be used for signal transmission.
Teleprotection
A distinction is made between underreach and overreach schemes.
Schemes
In underreach schemes, the protection is set with a normal grading characteristic. If a
trip command occurs in the first zone, the other line end receives this information via
a transmission channel. There the received signal initates a trip, either by activation of
overreach zone Z1B or via a direct trip command.
7SD5 allows:
• PUTT (Pickup),
• Permissive Underreach Transfer Trip with Zone Acceleration Z1B (PUTT),
• Direct (Underreach) Transfer Trip
In overreach schemes, the protection works from the start with a fast overreaching
zone. This zone, however, can only cause a trip if the opposite end also detects a fault
in the overreaching zone. A release (unblock) signal or a block signal can be transmit-
ted. The following teleprotection schemes are differentiated:
Permissive (release) schemes:
• Permissive Overreach Transfer Trip (POTT) (with overreaching zone Z1B).
• Directional comparison,
• Unblocking with overreaching zone Z1B.
Blocking scheme:
• Blocking of overreaching zone Z1B.
Schemes via pilot wire:
• Pilot Wire Comparison
• Reverse Interlocking
As the distance zones Z1 ... Z5 (without Z1B) function independently, an instanta-
neous trip in Z1 without a release or blocking signal is always possible. If fast tripping
in Z1 is not required (e.g. on very short lines), then Z1 must be delayed with T1.
Transmission
For the signal transmission, one channel in each direction is required. For example,
Channels
fibre optic connections or voice frequency modulated high frequency channels via pilot
cables, power line carrier or microwave radio links can be used for this purpose.
As an alternative, digital communication lines connected to one of the protection data
interfaces can be used for signal transmission. For example: fibre optic cables, com-
7SD5 Manual
C53000-G1176-C169-1
2.7 Teleprotection for Distance Protection (optional)
175
Hide quick links:
Advertisement
Table of Contents
