1.
Substation
Protection
System

2.
Presented By:
Assistant Project Managers, MRT Line-1, DMTCL
Namely,
- Mr. Tafhimul Hossain Siddiqi
- Mr. Md. Rakib Hasan Sarker
- Mr. Ashim Das
- Mr. Md. Intishar Rahman

3.
Table of contents
Protection
What is protection & Why
Requirements
Obejectives, Requirements
& How
CT, PT Relay, Circuit
Breakers, Arrester &
Isolators
Mechanisms of devices
Conclusions
You can describe the
topic of the section here
Devices
Common devices needed
for protection
04 05
01 02 03

4.
Protection
01
In the field of electrical engineering
protection is the measures and
activities to guarding the electrical
system and its parts from faults
through the isolation of faulty parts.

5.
Why?
IF SOMETHING CAN
GO WRONG
IT WILL!
-Murphy’s Law

6.
Objectives
The objective of a protection scheme is to keep the power
system stable by isolating only the components that are
under fault, whilst leaving as much of the network as possible
still in operation
Under abnormal working condition protection is necessary
for safety of valuable electrical equipments and safety of
human beings.

7.
Requirements
Reliability
Selectibility
Speed
Sensibility

8.
How?
A typical substation design would be …

9.
Devices
03
The apparatus and their associated
auxiliaries employed for controlling,
regulating and switching on or off the
electrical circuits in the power system
are known as the protection devices
or switchgear.

10.
Devices
Protection devices protect the
transmission lines, generators and
transformers as well as other
connected electrical equipment from
faults or overcurrent or overvoltage.

11.
Faults, Types of
Short circuit faults
Relay detected faults
Open circuit faults
3
1
2

12.
Switchgear Apparatus
Despite being red,
Mars is a cold place
CT & PT
measurement of
alternating
current & voltages
Circuit Breakers
For closing or opening
contact members
Isolators Lightning Arresters
Saturn is a gas giant
and has several rings
01 02
03 04
Despite being red,
Mars is a cold place
Relays Earthing
Saturn is a gas giant
and has several rings
05 06

13.
04
CT, PT, Relay,
Circuit Breakers
Arrester & Isolators

14.
Current Transformer
o A current transformer is used for measurement of alternating current
o When current in a circuit is too high to apply directly to measuring
instruments a current transformer produces a relatively reduced current
accurately proportional to the current in the circuit which can then be
conveniently connected to measuring and recording instruments.
o Current transformers are commonly used in metering and protective relays

15.
Potential Transformer
o Potential transformer are a parallely connected device
o Used for accurately measuring the proportional voltage ratio and phase
relationship so as to enable metering.

16.
Circuit Breaker
o Circuit breakers are automatically operated devices designed to close or
open contact members, thus closing and opening an electrical circuit under
normal or abnormal condition.
o It operates on relay command.
o It handles large voltage or current or anomolous frequencies.
o Consist of two contacts namely fixed and moving contact which stay in touch
with each other in normal condition. (Closed)
o Whenever a fault occurs (detected by the relay) the trip coil gets energized
the moving contacts get pilled by some mechanism and therefore the circuit
breaker is opened and the circuit is broken.

17.
Lightning Arresters
o The device or equipment used for the protection of the power system against
voltage surge is 'surge diverter' or 'lightning arrester'.

18.
Isolators
o These devices are used for the high voltage from the flow through line into
the bus, It only allows current to pass once in closed position.
o Isolators are off-load device.

19.
Conclusion
Years of knowledge and expertise have led
to improved engineering for the protection
system of the substations and thus more
and more control and reliability.
With the advancement of technology in this
field now-a-days the substation protection
systems are mostly automated.
05

20.
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