Relays are electromagnetic switches that are designed to detect faults on electrical circuits and trip circuit breakers. They use a low amperage control circuit to operate a high amperage tripping circuit. Relays can be classified based on their construction, applications, or time of operation. Common types include impedance, reactance, mho, and digital protective relays. Impedance relays have an overcurrent operative torque and a voltage-restraining torque. Reactance relays have a current operative torque and a directional restraining torque. Mho relays induce operative torque from both voltage and current and have a voltage-restraining torque. Digital protective relays use microprocessors to analyze voltages, currents, and

1. RELAYS
Presented By:-
ANIL KUMAR KUMAWAT
4Yr. EE
Guided By:-
Mr. GAURAV SRIVASTAVA
(Seminar Co-ordinator)

2. CONTENTS :-
Introduction
trip circuit
Functional diagram
Classifications
Distance relAy
I. Impedance relay
II. Reactance relay
III. Mho relay
 references

3. Introduction :-
 designed to trip a circuit breaker when a fault is
detected.
 A relay may also be called an “electromagnetic
switch”.
 Relays use a “low amperage circuit” to control a
“high amperage circuit”.

4. trip circuit :-

5. functional diagram:-
Ct & pt
rectifier Measuring unit amplifier Output unit
Trip
coil
Dc supply
Consists of level
Detector,filters etc.

6. Classifications :-
 According to Construction & Principle –
1. Electromagnetic Attraction relay
2. Electromagnetic Induction relay
3. Electro dynamic relay
4. Moving Coil relay
5. Thermal type relay
6. Static relay etc.

7.  According to Applications :-
1.Under V,Under I,Under P Relay
2.Over V, Over I,Over P Relay
3.Directional or Reverse Current Relay
4.Directional or Reverse Power Relay
5.Differential Relay
6.Distance Relay etc.

8. According to Time of Operation :-
1.Instantaneous type Relay
2.Definite Time Lag Relay
3.Inverse Time Lag Relay
4.IDMT Lag Relay

9. Distance relay :-
1.IMPEDANCE RELAY
o +ve (operative)Torque by
current element
o -ve(restraining)Torque by voltage element
At normal condition
operative torque = restraining torque
At fault
operative torque > restraining torque
Also called voltage restrained over current relay.

12. 2.Reactance relay :-
o Operative Torque by current
o Restraining Torque by Current-Voltage Directional relay
 +ve torque by over current element
 -ve torque by directional unit
Directional element designed for maxi. Torque angle =
90 degree

15. 3.Mho relay :-
Induction cup type structure.
oOperative Torque produced by V & I element.
o Restraining Torque by Voltage element.
Also called Admittance relay.

18. Digital protective relay
 Protective relay that uses a micro
processor to analyze power system
voltages, currents or other process
quantities for the purpose of detection
of faults in an industrial process
system.
Also called NEUMERIC RELAY.

19. 1.Input processing
2. Logic processing
3. Parameter setting
4. Event recording
5. Data display
BLOCKS IN NEUMERIC RELAY :-

20. REFERENCES :-
https://www.wikipedia.org/
https://books.google.co.in/books?isbn=8184316399
Induction Type Relays. CircuitManiac.com. Accessed
March 8th, 2012.
 Fundamental Relay-Operating Principles and Characteristics.
G.E. Digital Energy. Accessed March 8th, 2012.
www.google.co.in