THE BEST VIRTUAL EXPO FOR INDUSTRIAL AUTOMATION PRODUCTS

Introduction to :

Protection Relays

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

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

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

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

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.

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

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

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

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

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

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

Protect ion re lays

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

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