Distance protection measures the impedance between the relay location and the fault point, comparing it to a set value. A distance relay measures the current and voltage to determine the impedance ratio and operates if this ratio indicates a fault within its protection zone. Distance relays are widely used for high-speed transmission and distribution line protection due to their non-unit characteristics and permanent settings.

2. CONTENTS
01
02
03
04
05
06
Introduction
Distance protection
Distance Relay
Distance relay in double circuit line
Distance relay characteristics
Advantages , Dis advantages and applications

3. Introduction
Distance Protection : -
 Distance Protection is non –unit type protection .
 which measures the Impedance between the Relay Location and the point where the fault is
incident and compares it with the Set Value.
Distance Relay : -
 A distance relay is a type of protection relay most often used for transmission line protection.
 Distance relays measure the impedance from the installation side to the fault location and
operates in response to changes in the ratio of measured current and voltage.

4. Distance Protection
Distance protection is widely used for protection
of transmission and distribution line .
It’s having a high speed protection.

5. Distance Relay
The distance relay is a distance protection element designed to measure the faulty point. Distance
relay principle is based on the determination of the fault impedance from the measured short
circuit voltage and current at the relay location.
These are double actuating quantity relays with one coil energized by voltage and other coil
energized by current. The torque produced is such that when V/I reduces below a set value the
relay will operate.
During the fault on transmission line the fault current increases and voltage at the fault point
reduces.

6. Distance Relay in double circuit line

7. Distance Relay Types
 According to the dependency of distance relay on voltage and current it’s classified into
three types.
i.e. 1. Impedance Relay
2. Reactance Relay
3. Admittance or MHO Relay
Also
1. Definite distance relay :-
It works when the value of reactance or admittance is below a predetermined impedance
value of the relay.
2. Time distance relay :-
It’s working depends on the value of impedance i.e. on the distance between the fault and
the relay point.

8. Impedance Relay Characteristics

9. Reactance Relay Characteristics

10. Mho Relay Characteristics

11. Advantages
Dis advantages
Application
i. It replaces the protection of overcurrent transmission lines.
ii. Available with permanent settings and there is no need to
readjust the settings.
i. As it operates on both sides faults of a line, then it is said to be
non-directional.
ii. The measurement capacity of fault resistance is limited
• These are most widely used to protect transmission lines and
distribution lines over high AC voltages.

12. Conclusion
Overall, Distance protection system and distance relay both are needed
for protection of transmission and distribution line as primary or
backup protection.

13. Thank you!