This document provides an overview of different types of protection relays used in industrial automation. It discusses electromagnetic and digital protection relays, and describes various specialized relays including motor protection relays, differential protection relays, earth fault protection relays, feeder protection relays, overvoltage protection relays, generator protection relays, transformer protection relays, distance protection relays, and arc protection relays. The document aims to introduce readers to these relay types and their functions in protecting electrical circuits and industrial equipment from faults.

1. THE BEST VIRTUAL EXPO FOR INDUSTRIAL AUTOMATION
PRODUCTS
Introduction to :
Protection Relays

2. In electrical engineering, a protective relay is a device designed to trip
a circuit breaker when a fault is detected. The first protective relays
were electromagnetic devices, relying on coils operating on moving
parts to provide detection of abnormal operating conditions such as
over-current, over-voltage, reverse power flow, over- and under-
frequency. There are many different types of valves that are found in
different industries and applications are as Below:
Motor protection relays Overvoltage protection relays
Digital protection relays Generator protection relays
Differential protection relays Transformer protection relays
Earth fault protection relays Distace protection relays
Feeder protection relays Arc protection relays

3. M o t o r p r o t e c t i o n r e l a y s
Motor protection relays are safety industrial
devices that function by protecting the internally
built structures of a motor. They’re few features
of motor protection relays :
1. Electric motor protection
2. Overload protection
3. Special motor protection
4. System motor protection
5. Control functions

4. D i g i t a l p r o t e c t i o n r e l a y s
Digital protection relays are types of industrial
safety devices that operate using a digitized
microprocessor laced with software-based
algorithms which function by detecting electrical
faults as well as protecting the machine.
Operating Principes are:
a) Input processing
b) Logic processing
c) Parameter setting
d) Event recording
e) Data display

5. D i f f e r e n t i a l p r o t e c t i o n
r e l a y s
Differential relays are types of relays that operate
when a differential vector of two or more
electrical quantities which are similar exceed
the pre determined amount of a current.
Types of differential protection relays
1. Current-differential
2. Percentage-differential

6. E a r t h f a u l t p r o t e c t i o n
r e l a y s
Earth-fault relays are industrial protection relays
which are used to protect any industrial
mechanical feeder against faults which involve
the ground connection.
Most common types of faults are
1. Line faults
2. Line to line faults
3. Double line faults
4. Three phase line faults
Earth fault relays employ a protection procedure
which acts by protecting the machines
or electrical equipments connected to the
primary power source.

7. F e e d e r p r o t e c t i o n r e l a y s
Feeder protection relays are types of protective
relays that function by feeding current to the
main transformer. They are also known as
distribution relays due to their current distribution
character.
Features
1. Complete feeder protection
2. Under frequency protection
3. Device synchronization

8. O v e r v o l t a g e p r o t e c t i o n
r e l a y s
Overvoltage protection relays are types of
industrial safety relays that functions by
protecting an industrial machine from dangerous
high voltage currents that may destroy the
machine.
Types of Overvoltage relays
1. Zener diodes
2. Metal Oxide Varistors (MOV)
3. Gas dicharge tubes
4. Semiconductor Suppressors

9. G e n e r a l p r o t e c t i o n r e l a y s
Generator relays are types of industrial relays that
are primarily designed to protect generators from
surges and high electric voltages.
Generator relays are available in three
different symmetrical designs
a) Positive Sequence
b) Negative Seguence
c) Zero Phase

10. Tr a n s f o r m e r p r o t e c t i o n
r e l a y s
Transformer protection relays are industrial
relays which function by preventing, repairing and
replacing a transformer fault.
Some of the features
a) High response time of less than 1.5 cycles.
b) In-built software’s
c) Different types of synchrophasors are
easily sent between the relay and the
transformer

11. D i s t a n c e p r o t e c t i o n r e l a y s
These are types of relays which detect electrical
faults depending on the fault in the line of electrical
flow. The relay operates depending on the
impendence found between the point of relay
installing and the point of fault.
Types distance relays
a) Definite distance relay
b) Time distance relay

12. A r c p r o t e c t i o n r e l a y s
These are types of relays that function by
protecting an industrial machine from arc faults
which arise when the current passes through a
dielectric. Arc faults or arc flash is a mass of
heat and pressure which is usually caused by a
switchgear fault.
Applications of arc protection relays
1. They are easily connected to automation
systemsFlat Face (FF)
2. Communication protocols which use interfaces
with SCADA

13. Protection relays
Contact details :
VISUM Ltd.
Letna 40
040 01 Kosice
Slovakia - E.U.
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