DISTANCE PROTECTION
➢ Distance protection is primarily used in high-voltage transmission systems due
to its accuracy, speed, and reliability in detecting and isolating faults.
➢ Distance protection, also known as impedance protection, is a type of protection
scheme used in electrical power systems to detect and isolate faults. It operates
by measuring the impedance (resistance and reactance) of the line from the relay
location to the fault.
DISTANCE PROTECTION
Principle of Operation: Distance protection works on the principle that the impedance of a
transmission line is directly proportional to its length. When a fault occurs, the impedance measured
by the relay decreases because the fault creates a low-impedance path.
Zones of Protection: Distance protection typically uses multiple zones of protection, each covering
different lengths of the transmission line. These zones are set to operate for faults within their
designated areas.
Zone 1: Immediate tripping without delay, covering 80-90% of the line length.
Zone 2: Delayed tripping, extending beyond Zone 1 to cover the remaining line and a
portion of the adjacent line.
Zone 3: Additional backup protection, covering the entire line and extending further into
the adjacent line
DISTANCE PROTECTION
Zones of Protection:
Zone 1: This zone typically covers 80-90% of the line length from the relay
location. It is set to operate instantaneously for faults within this zone.
Zone 2: This zone usually extends to cover the remaining portion of the
line and a part of the next line section. It operates with a time delay to
ensure selective tripping.
Zone 3: This zone provides backup protection and extends further, typically
covering the next line section entirely. It operates with a longer time delay.
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DISTANCE PROTECTION
Lets take an example:
DISTANCE PROTECTION
