Unit 6
Created @June 11, 2022 12:22 AM
chapter Instrumentation & Equipment in Power Plants
Theory
Dec 2019
May 2019
Dec 2018
May 2018
Dec 2017
May 2017
Dec 2016
May 2016
Numerical
Dec 2019
May 2019
Extra Questions
Switch Gears
Definition of Switchgear: Switchgear is a general term which constitutes all
the equipment of a power plant whose function is to receive and distribute
electrical power.
apparatus used for switching, controlling and protecting the electrical
circuits
switchgear may refer to a number of different systems and components.
Switchgear examples include the following:
Switches
Fuses
Isolators
Relays
Circuit Breakers
Lightning Arresters
Unit 6 1
, Functions of switch gear
The faulty plant is automatically disconnected from the system by the
operation of protective equipment.
To break short circuit without giving rise to dangerous conditions.
To facilitate inspection and maintenance on the system.
Switchgear Classification: three different classes of switchgear systems:
low-voltage
are designed to regulate systems of up to 1KV.
medium-voltage
are used in systems from 1KV up to 75KV.
high-voltage.
those that control 75KV of power or more.
Types of Switchgears
Indoor Switchgear
used for voltage range 20kV to 119kV
small capacity installation
Unit Type Switchgear
are assembled and manufactured as a unit by the manufacturer.
Outdoor Switchgear
for high voltages above 35kV
Classification according to Isolating Media Types
Air
the least expensive insulation option (and thus the most commonly
used), the air has a low dielectric strength, making it a relatively poor
insulator.
Fluid
offers better insulation when compared to air, and is similarly
inexpensive. Fluid also provides the added advantage of cooling for
overheated systems.
Unit 6 2
, Gas
offers increased dielectric strength compared to standard air
insulation
Oil
Oil has a high dielectric strength, and may also provide increased
cooling benefits.
Solid
can provide exceptional dielectric strength, as well as resistance to
chemical and thermal deterioration.
Working of switch gear
Different kinds of switchgears may follow different operational processes
basic switchgears follow a relatively straightforward process:
In the event of an electrical fault, the relay closes the trip circuit,
disconnecting downstream loads. This allows the remainder of a
circuit to continue operating without disruption, while also
protecting vital equipment from damage.
It is connected directly to the supply system by placing in the low &
high voltage planes of the power transformer. This device de-energizes
for clearing the fault, testing & maintaining. These devices play an
essential role in the power system to protect the equipment from the
heavy current. Otherwise, the device may get damaged & the service
gets interrupted. So these devices are essential to protect the
equipment from the damage like a transformer, generators, lines, etc.
The main features of this include the following.
Manual control provision
Fast operation
Completely certain discrimination
Entire Reliability
Circuit Breakers
Circuit Breaker:
Unit 6 3
, A circuit breaker is an equipment which can open or close a circuit under
conditions like no-load, full load and fault conditions. It is so designed
that it can be operated manually (or by remote control) under normal
conditions and automatically under fault conditions.
Function
To make the connection when required and to trip or disconnect the
circuit under faulty or abnormal conditions.
Helps to prevent damage of electrical equipment in an installation.
Working
A circuit breaker essentially consists of fixed and moving contacts,
called electrodes. These contacts are placed in the closed chamber
containing a fluid containing medium (either liquid or gas) which
quenches the arc formed between the contacts.
Under normal operating conditions, these contacts remain closed and
will not open automatically until and unless the system becomes
faulty.
The contacts can be opened manually or by remote control whenever
desired.
When a fault occurs on any part of the system, the trip coils of the
breaker get energized. The moving contacts are pulled apart by
some mechanism, thus opening the circuit.
Types of circuit breaker
On the basis of voltage
low voltage circuit breakers
used in home circuits.
high voltage circuit breakers
are mainly used in substation
Type
Oil Circuit Breaker
Air Circuit Breaker
Air Circuit Breaker
Unit 6 4
Created @June 11, 2022 12:22 AM
chapter Instrumentation & Equipment in Power Plants
Theory
Dec 2019
May 2019
Dec 2018
May 2018
Dec 2017
May 2017
Dec 2016
May 2016
Numerical
Dec 2019
May 2019
Extra Questions
Switch Gears
Definition of Switchgear: Switchgear is a general term which constitutes all
the equipment of a power plant whose function is to receive and distribute
electrical power.
apparatus used for switching, controlling and protecting the electrical
circuits
switchgear may refer to a number of different systems and components.
Switchgear examples include the following:
Switches
Fuses
Isolators
Relays
Circuit Breakers
Lightning Arresters
Unit 6 1
, Functions of switch gear
The faulty plant is automatically disconnected from the system by the
operation of protective equipment.
To break short circuit without giving rise to dangerous conditions.
To facilitate inspection and maintenance on the system.
Switchgear Classification: three different classes of switchgear systems:
low-voltage
are designed to regulate systems of up to 1KV.
medium-voltage
are used in systems from 1KV up to 75KV.
high-voltage.
those that control 75KV of power or more.
Types of Switchgears
Indoor Switchgear
used for voltage range 20kV to 119kV
small capacity installation
Unit Type Switchgear
are assembled and manufactured as a unit by the manufacturer.
Outdoor Switchgear
for high voltages above 35kV
Classification according to Isolating Media Types
Air
the least expensive insulation option (and thus the most commonly
used), the air has a low dielectric strength, making it a relatively poor
insulator.
Fluid
offers better insulation when compared to air, and is similarly
inexpensive. Fluid also provides the added advantage of cooling for
overheated systems.
Unit 6 2
, Gas
offers increased dielectric strength compared to standard air
insulation
Oil
Oil has a high dielectric strength, and may also provide increased
cooling benefits.
Solid
can provide exceptional dielectric strength, as well as resistance to
chemical and thermal deterioration.
Working of switch gear
Different kinds of switchgears may follow different operational processes
basic switchgears follow a relatively straightforward process:
In the event of an electrical fault, the relay closes the trip circuit,
disconnecting downstream loads. This allows the remainder of a
circuit to continue operating without disruption, while also
protecting vital equipment from damage.
It is connected directly to the supply system by placing in the low &
high voltage planes of the power transformer. This device de-energizes
for clearing the fault, testing & maintaining. These devices play an
essential role in the power system to protect the equipment from the
heavy current. Otherwise, the device may get damaged & the service
gets interrupted. So these devices are essential to protect the
equipment from the damage like a transformer, generators, lines, etc.
The main features of this include the following.
Manual control provision
Fast operation
Completely certain discrimination
Entire Reliability
Circuit Breakers
Circuit Breaker:
Unit 6 3
, A circuit breaker is an equipment which can open or close a circuit under
conditions like no-load, full load and fault conditions. It is so designed
that it can be operated manually (or by remote control) under normal
conditions and automatically under fault conditions.
Function
To make the connection when required and to trip or disconnect the
circuit under faulty or abnormal conditions.
Helps to prevent damage of electrical equipment in an installation.
Working
A circuit breaker essentially consists of fixed and moving contacts,
called electrodes. These contacts are placed in the closed chamber
containing a fluid containing medium (either liquid or gas) which
quenches the arc formed between the contacts.
Under normal operating conditions, these contacts remain closed and
will not open automatically until and unless the system becomes
faulty.
The contacts can be opened manually or by remote control whenever
desired.
When a fault occurs on any part of the system, the trip coils of the
breaker get energized. The moving contacts are pulled apart by
some mechanism, thus opening the circuit.
Types of circuit breaker
On the basis of voltage
low voltage circuit breakers
used in home circuits.
high voltage circuit breakers
are mainly used in substation
Type
Oil Circuit Breaker
Air Circuit Breaker
Air Circuit Breaker
Unit 6 4
