Switchgear and protection Lab Manual (20EE33P)

LAB MANUAL

SWITCHGEAR AND PROTECTION LAB (20EE33P)

rd
III SEM ELECTRICAL AND ELECTRONICS ENGINEERING

Prepared by
K.MURUGAN
FORMER HOD
DEPT OF EEE
DSIT, BENGALURU-111

NAME OF STUDENT:

REGISTER NUMBER:

ROLL NUMBER :

DAYANANDA SAGAR INSTITUTE OF TECHNOLOGY (POLYTECHNIC)

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
SHAVIGE MALLESHWARA HILLS, KUMARASWAMY LAYOUT, BENGALURU-560111

Academic year 2022-2023

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 Switchgear and protection Lab Manual (20EE33P)

1. Identify various fuse sets viz., HRC, DO, 33KV fuse set, etc. Date:
DC FUSE

AC FUSE (LOW VOLTAGE)

AC FUSE (HIGH VOLTAGE )

Definition: HRC fuse (high rupturing capacity fuse) is one kind of fuse, where the fuse wire carries a short
circuit current in a set period if the fault occurs in the circuit then it blows off.

signature of staff in charge

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 Switchgear and protection Lab Manual (20EE33P)

1a. Measure and select the appropriate size of fuse wire. Date:

AIM: To Measure and select the appropriate size of fuse wire by using SWG plate

Apparatus required

1. standard wire gauge plate

2. different size of fuse wire

SWG Plate and different size fuse wire

Procedure
1. first keep the SWG Plate and different size of fuse wires ready to be measured
2. take fuse wire and insert it in to the hole of SWG plate and find out the size
3. Wire gauge sizes are represented through numerical values, SWG 0 through SWG 36.
4. The lower the number assigned to a wire the larger its diameter; the higher the number the smaller its
diameter. SWG stands for Standard Wire Gauge.
5. Different sizes of fuse wires are measured and tabulated.

Sl no Size of fuse wire in SWG

1
2
3
4
Result:
Signature of staff in charge

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1b. Test the HRC fuse by performing a Load test. Date:

Aim: To test the HRC fuse by performing a Load test.

Apparatus required

Circuit diagram

Tabular column

Result:

Signature of staff in charge

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2a. Identify the various types of CB- MCB, ELCB, RCCB, MPCB and MCCB. Trace and locate MCBs used in your
institution and note down their specifications. Date:

MCB, MCCB, RCCB, and ELCB are circuit breakers but all of them are designed for serving a specific
purpose.

MCB stands for Miniature Circuit Breaker. It automatically switches OFF electrical circuit during any
abnormal condition in the electrical network such as overload & short circuit conditions. However, fuse may
sense these conditions but it has to be replaced though MCB can be reset. The MCB is an electromechanical
device which guards the electric wires &electrical load from over current so as to avoid any kind of fire or
electrical hazards.
Handling MCB is quite safer and it quickly restores the supply. When it comes to house
applications, MCB is the most preferred choice for overload and short circuit protection. MCB can be reset
very fast & don’t have any maintenance cost. MCB works on bi-metal respective principle which provides
protection against overloadcurrent&shortcircuitcurrent.

MCCB stands for Molded Case Circuit Breaker. It is another type of electrical protection device which
is used when load current exceeds the limit of a miniature circuit breaker. The MCCB provides
protection against overload, short circuit faults and is also used for switching the circuits. It can be used
for higher current rating and fault level even in domestic applications. The wide current ratings and high
breaking capacity in MCCB find their use in industrial applications. MCCB can be used for protection
of capacitor bank, generator protection and main electric feeder distribution. It offers adequate
protection whenever an application requires discrimination, adjustable overload setting or earth fault
protection.

RCCB stands for Residual Current Circuit Breaker. This residual current device is
basically an electrical wiring device that disconnects the circuit whenever there is
leakage of current 昀氀ow through the Human body or the current is not balanced
between the phase conductors. It is the safest device to detect and trip against
electrical leakage currents, thus ensure protection against electric shock caused

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by direct contacts. RCCB is generally used in series with an MCB which protects
them from over current and short circuit current.

Both phase and neutral wires are connected through a RCCB device. These are an
extremely e昀昀ective form of shock protection & widely used for protection from a
leakage current of 30,100 & 300mA. It is essential lifesaving equipment used to
protect the human body from electrical and is mandatory in many states for
domestic installation.
ELCB: ELCB stands for Earth Leakage Circuit Breaker. They have the same function as RCCB but are
voltage sensor devise. However, this is an old technology & is not in common use. RCCB being a current
sensitive device have a better advantage over ELCB as under:

MPCB: A motor protection circuit breaker, or MPCB, is an electromechanical

device that performs three important functions upstream of an electric motor:
isolation, motor protection against overload and short circuit, control of the motor
(on/o昀昀).
In the event of overload or short circuits, the MPCB automatically disconnects the
circuit. It has internal contacts that connect the power supply line to the load. An
internal coil detects the short-circuit currents (high or very high current values),
while a heat-sensitive element, welded on the bimetal, detects over currents
(current values slightly higher than the nominal value) which may damage the
motor. In the event of over currents, the coil or the bimetal determine the opening
of the contacts.

Signature of staff in charge

2b. Dismantle MCCB/ELCB and identify various parts. Date:

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Functions of MCCB
1. Protection against overload
2. Electric fault protection
3. Switching the circuits on and o昀昀

Main parts of MCCB

1. Arc chute
2. Contacts
3. Operating mechanism
4. Terminal Connector
5. Thermal Trip Unit
6. Magnetic Trip Unit
7. Handle / Trip-free Mechanism
8. Trip Button

Arc chute is a set of parallel metal plates that are mutually insulated from each other. it helps in
extinguishing the arc by splitting the arc and lengthening it. it is also known as an arc divider or arc splitter.
These plates are made of ferromagnetic material.
Contacts: Contacts are the metallic conductors that are responsible for carrying the current to the load.
There are two types of contacts i.e. fixed and moving contact. The contacts are made of arc resistance

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material having low resistivity and corrosion. The quality of the material decides the lifetime of the circuit
breaker.
Operating Mechanism: It is the mechanism of MCCB responsible for opening and closing the current-
carrying contacts. it is connected with trip unit that triggers the operating mechanism. The trip unit operates
on a thermal and magnetic mechanism.
Terminal Connector: The terminal connectors are used to connect the MCCB to the external circuit. The
upper terminals are connected to the output/load while the bottom terminals are connected to the
input/supply. Although they are bidirectional, the input and output designation is due to their physical
installation
Trip Unit: It is the unit responsible to trigger the operating mechanism. The trip unit includes a thermal
mechanism for overload, magnetic tripping for short circuits and a test button for testing.
Thermal Trip Unit : The thermal trip unit uses a thermal mechanism that is a bimetallic strip that bends
(and opens the contacts) when the temperature rises due to the overloading.
Magnetic Trip Unit : The magnetic trip unit has a relay that generates a magnetic field when higher
currents flow through its solenoid due to the short circuit. it trips the circuit breaker. While the test button is
used to simulate the above-said mechanisms and test the response of the circuit breaker.
Handle / Trip-free Mechanism : It is a handle used to open or close the breaker manually. It is also known
as a trip-free mechanism because it will trip even if the handle is held in ON position.
The handle could be in either three positions i.e. upward, middle or downward. If the handle is in upward
position, it is ON position. If it is in the middle position, the breaker has been tripped while the downward
position shows OFF status.
Trip Button : The trip button is used for testing the breaker. It is a red-colored button that trips the operating
mechanism when pushed.

Signature of staff in charge

2c. Test the MCB and plot its inverse time characteristic curve. Date:
AIM: study the operation of MCB and plot the operating characteristics
MCB has two characteristics.
1. Inverse time characteristics during over load.
2. Instantaneous characteristics during short circuit
APPARATUS REQUIRED:
01. Single Pole MCB (preferably lower rating like 6 A)
02. Ammeter 0-10A MI
03. 15 A SPST switch.
04. Single phase Auto-transformer (dimmer-stat) 0-300 V 10A
05. Resistive load, 10 A single phase.
06. Stop clock / digital watch.

CIRCUIT DIAGRAM

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 Switchgear and protection Lab Manual (20EE33P)

PROCEDURE:
1. Connec琀椀ons are made as per the circuit diagram.
2. do not on MCB
3. connect the shor琀椀ng link between dashed line
4. Switch on the current injec琀椀on source and set current to the ra琀椀ng of MCB and observe this current in
meter.
5. Switch o昀昀 the current injec琀椀on unit and remove the shor琀椀ng link.
6. now switch on the current injec琀椀on kit and observe the tripping of MCB
7. Repeat the above procedure for 2 and 3 琀椀mes the rated current of the MCB.
8. in each step note down the 琀椀me taken by the MCB to trip
9. Plot the 琀椀me-current characteris琀椀cs.
TABULAR COLOUMN

Result Signature of staff in charge

2d. Troubleshooting and servicing of LT circuit breaker. Date:
Troubleshooting Circuit Breaker

1. Identify Tripped Circuit Breaker: circuit breaker emits a humming sound when it is overloaded
but has not switched off yet. Inside your electric access panel, the tripped breaker lever can usually
be found between the “on” and “off” position
2. Test the Circuit Breaker; Check the levers by moving it from ‘on’ to ‘off’ a couple of times to
check how lose it is. If breaker has no ‘give’ and moves easily then it is faulty and need to have it
replaced as soon as possible.
3. Switch off All Appliances Again: Switch off all appliances that are connected to circuit breaker but
make sure to do it all at once to prevent a surge of electrical power when you reset it. If circuit
breaker keeps on tripping then hire a professional to come and have a look at it.

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4. Check Wiring: If it has faulty wiring, then circuit breaker will be tripping continuously and it may
give electrical shocks when powering certain appliances. This requires a trained professional so don’t
try this on your own. Simply identify the problem and hire a professional to take care of it.
5. Test for the Necessary Voltage: Touch one probe of the 120-240 volt tester to the tip of the “hot”
wire, while touching the other tip to a bare copper grounding wire within the main electrical box. Use
a neutral grounding terminal which is secured with ground wires and neutral wires for the probe. You
will need to replace your circuit breaker if you find the right amount of voltage present.

Servicing of LT circuit breaker.

Cleaning: Clean all insulating materials with vacuum and/or clean lint free rags. If it is necessary to use
cleaning solvents, use only solvents recommended by the manufacturer.
Contacts: Ensure that all contacts are clean, smooth, and in proper alignment. Ensure that spring
pressures are maintained according to manufacturer’s specifications. On silver contacts, discoloration is not
usually harmful unless caused by insulating deposits. Clean silver contacts with alcohol or silver cleaner
using non-abrasive cloths.
Draw out contacts on the circuit breaker and the stationary contacts in the cubicle should be cleaned and
inspected for overheating, alignment, and broken or weak springs. Coat contact surfaces with contact
lubricant to ease mating.
Arc interrupters: Clean all ceramic materials of loose dirt and examine for signs of moisture, make sure the
assemblies are clean and dry. Examine for cracked or broken pieces. Dirt and arcing deposits may be
removed by light sanding — do not use emery cloth or wire brushes which may leave conductive residue
behind. Repair or replace as necessary.

Signature of staff in charge

2e. Test any commercially available ACCL. Date:
AIM: Test Any Commercially Available ACCL

APPARATUS REQUIRED:
1 ACCL RELAY--- 01
2 MCB /SWITCH--- 02
3 LAMP LOAD--- 01
4 patch cords as required

THEORY: Automatic Changeover with current limiter allows supply from mains as long as the load current
is below programmed current. When the mains supply fails and stand by generator supply is on it connects
the DG power to each consumer in sequence and starts monitoring its load. When the load current exceeds

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the allotment power is automatically switched off until load is below programmed current, and automatically
restored. Apart from Over load an EB and DG it also protects against over voltage from DG side.
Circuit diagram

PROCEDURE:
1. Ensure the main power switch is off KEB and DG supply is OFF.
2. Now connect load to load terminal of ACCL relay’
3. Now connect EB and DG power supply through MCB or any Switch for creating fault.
4. Now switch on DG MCB and observe the load which turns on after few seconds.
5. Now turn on KEB supply and relay switches the load to KEB supply.
6. Now switch off KEB supply again keeping DG supply in ON position and load will be on DG supply,
slowly increase the load above the programmed current value is achieved, the relay will be tripped.

RESULTS:
The tes琀椀ng of any commercially available ACCL relay is conducted.

Signature of staff in charge

3. Visit to Substation.
3a. identify the parts of circuit breaker and check its operation. Date:

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Circuit breaker essentially consists of fixed and moving contacts. These contacts are touching each other and
carrying the current under normal conditions when the circuit is closed. When the circuit breaker is closed,
the current carrying contacts, called the electrodes, engaged each other under the pressure of a spring.
During the normal operating condition, the arms of the circuit breaker can be opened or closed for a
witching and maintenance of the system. To open the circuit breaker, only a pressure is required to be
applied to a trigger.

Whenever a fault occurs on any part of the system, the trip coil of the breaker gets energized and the moving
contacts are getting apart from each other by some mechanism, thus opening the circuit.

The separation of current carrying contacts strikes an arc between them. Once an arc is formed between
contacts, the molecules of the medium surrounded by arc become extremely hot and get ionized, i.e. the
insulating property of it is destroyed, and it becomes a conductor of electricity. Therefore, the arc is
maintained even if the contacts are further drawn. This arc produces heat in a huge quantity which may
cause damage to the system or to the circuit breaker itself.

Signature of staff in charge

3b. Demonstrate test tripping characteristic of circuit breaker for over current and short circuit current.
3c. Demonstrate Installation operation and maintenance of SF6 circuit breaker, Vacuum circuit breaker.

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Installation of SF6 circuit breaker Date;

1 . Remove all packaging material.
2. Li昀琀 the breaker using the crane and following the rigging arrangement.
3. Unbolt the leg extensions and lower them into the posi琀椀on and R ... assemble the legs using the fasteners
provided with the legs.
4. Place the breaker on Its founda琀椀on pad
5. Grout or shim under the breaker foot pads and secure the anchor bolls.
6. Permanently ground the circuit breaker structure. Two NEMA grounding pads, welded to the front and rear
structural legs at opposite comers, are provided for this purpose
7. Ground the control cabinet ground terminal located on the Inside rear wall of the cabinet
8. Clean the entrance bushings to remove any dirt or debris which may have accumulated during shipment and
Installa琀椀on
9. Touch up any areas of damaged or chipped paint using the provided touch-up paint.
10. Complete the Installa琀椀on and commissioning checklist Included in the Checklists module.

Commissioning the Breaker Commissioning follows Installa琀椀on. Commissioning the breaker Involves:
1. Making electrical connections;
2. Filling the breaker with SF, gas;
3. Testing the breaker;
4. Completing the Installation and commissioning checklist (In the Checklists module);
5. Completing the commissioning check list for the mechanism (In the Mechanism module).

Construction of SF6 Circuit Breaker

SF6 circuit breaker is filled with SF6 gas at pressure 5Kaf/cm^2. Sulphur hexafluoride breaker consists of two-part
mainly interrupter unit and gas unit. The below diagram shows the construction of a puffer type SF6 circuit breaker.

The moving cylinders attached to the movable conductor against the fixed piston. As shown in the diagram of the
Sulphur hexafluoride breaker with a fully closed position of the interrupter and there is the relative movement between
the fixed piston and movable cylinder.
Due to this gas is compressed between this contact. This compressed gas in the cavity is released through the nozzle
during the arc extinguishing process.
Working Principle of SF6 Circuit Breaker

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Normally breakers contacts are closed position when the fault occurs in the power system. The contacts get separated
and arc stuck between the fixed contact and movable contact during contact separation, compressed SF6 gas in cavity
is released over the arc and it reduced arc diameter by axial conversion and radial dissipation. At current zero arc
diameter becomes too small and arc get extinguish.

INSTALLATION OF VACUUM CIRCUIT BREAKER

1. Check goods according with the packing list.
2. Clean the insulating parts with a clean dry cloth.
3. Check that the upper and lower terminals are clean and free of any damage caused by transport or storage.
4. Verify the condition of the vacuum interrupter through power frequency withstand voltage test (Hipot), apply
the rated power frequency withstand phase to phase and phase to ground for 1 min.
5. Breaker/rollout clusters and primary stabs in the cubicle.
6. Ground bar on the bottom of the breaker/rollout and ground shoe in the cubicle.
7. Rollers on the breaker/rollout and the rails with-in the cubicle.
Commissioning
1. All commissioning and opera琀椀on work shall be carried out by persons who have received suitable training
and understand the performance of the circuit breaker
2. Make sure that all control circuits are not energized and that the breaker is removed from the metal-clad
unit.
3. Do not work on or install the breaker or mechanism while it is in the closed posi琀椀on.
4. Do not work on or install the breaker while the closing spring is charged.
5. A昀琀er the installa琀椀on of the circuit breaker into switchgear, the breaker should only be subjected to normal
recommended opera琀椀ng condi琀椀ons.

OPERATION OF VACUUM CIRCUIT BREAKER

A vacuum circuit breaker uses a vacuum for the extinguishing or extinction of arc.
The typical parts of a vacuum circuit breaker are moving contact, 昀椀xed contact,
and an arc shield inside a vacuum interrupter or vacuum chamber. There are
multiple bene昀椀ts of using both the HV and MV vacuum circuit breaker. They have a
longer life span, are compact in size, have high dielectric strength, no 昀椀re or
explosion hazards, no gas generation, and others. They are silent while operating
too.

In a vacuum circuit breaker, the contacts are present in a vacuum chamber. When
the two contacts move away and the circuit breaker is opened inside the contact
vacuum, an arc is produced due to the ionization of the metal vapors of contact.
This arc is quickly quenched by the vacuum since the ionized metal vapors, ions,
and electrons that are generated get condensed on the surface of the circuit
breaker contacts, resulting in the arc extinction.

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Maintenance

1. it is essential that the VCB is first switched off. Once it is off, it should be isolated from all sides.
You need to open up the electrical isolator to do this.
2. Follow the below steps then for proper maintenance:
3. Properly clean the vacuum circuit breaker with a CRC - 226 i.e an electrical contact cleaner. This
will ensure that the lubrication is proper in the VCB.
4. Clear any old grease in the VCB. Grease the VCB again, with new grease, of a similar type
5. Check the conditions of the fixed and the floating contacts
6. Inspect the positioning of the contacts
7. Check the outer layer, and other hardware parts of the VCB, and see that they are fixed properly
8. Use the VCB’s push button to check the breaker tripping
9. Check the electrical current between phase and phase i.e VCB closed state
10. Check the electrical current between phase and earth i.e VCB closed state
11. Check the electrical current between phase and earth i.e VCB open state

Signature of staff-incharge
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3d. Carry out timer test on circuit breakers.

3e. Demo on RMU Date:

https://www.youtube.com/watch?v=IuzNG9tXEgA

Ring Main Unit is a fully enclosed, compact, factory assembled cabinet used for medium-voltage power
distribution. In simple words, this is a switchgear unit that is easily replaceable, requires low maintenance,
and is highly protected in nature. In an electrical power distribution system, a ring main unit (RMU) is a
factory assembled, metal enclosed set of switchgear used at the load connection points of a ring-type
distribution network. It includes in one unit two switches that can connect the load to either or both main
conductors, and a fusible switch or circuit breaker and switch that feed a distribution transformer.

Signature of staff in charge

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4a. demonstrate various parts of the relay and ascertain the operation. Date:

An electromechanical relay works on the simple principle of electromagnetism. When a low voltage direct
current is given to the energizing coil; electrical contacts are made in effect of the magnetic field.

You can consider this phenomenon as a simple switch where circuit is completed on a push of a button. A
simple relay is a two-way switch making the connection with different circuit on its either side; with three
contacts NC, COM and NO.

Relays with one common and two main contacts on a single pole arrangement are called single pole double
throw type. Similarly single throw single pole have one connection NO and double pole double throw have
two NO and NC respectively.

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Initially when no current is supplied to the energizing coil; contact is made with NC and COM. If you
connect a bulb with COM and NC at that time it will glow; similarly when the relay is energized you can
connect your bulb with COM and NO to glow.

While you look at an relay upside down; you will find five contact points. Three at the one side while two on
the opposite; the two contacts on the opposite side is for NO and NC while the others are Coil +, COM and
Coil – respectively.

When we supply current to these two points coil + and Coil – magnetic flux is produced; and the position of
armature is altered. Similarly when we disconnect the supply the armature goes back to its position and NC
contact is closed. To better understand in the given diagram; the load is connected to a 220V 50Hz power
supply through a switch actuated by relay. The relay is controlled using a separate 12 volt D.C supply.

Signature of staff in charge

4b. Demonstrate setting of pick-up current/ time setting multiplier for relay operation.

Pick Up Current of Relay: In all electrical relays, the moving contacts are not free to move. All the
contacts remain in their respective normal position by some force applied to them continuously. This force is
called the controlling force of the relay. This controlling force may be the gravitational force, may be a
spring force, or may be a magnetic force. The force applied to the relay’s moving parts for changing the
normal position of the contacts is called deflecting force. This deflecting force is always in opposition of
controlling force and is present always in the relay. The current for which the relay initiates its operation is
called pick up current of relay.

Current Setting of Relay: The minimum pick up value of the deflecting force of an electrical relay
is constant. The deflecting force of the coil is proportional to its number of turns and the current flowing
through the coil.
Now, if we change the number of active turns of any coil, the required current to reach at minimum pick
value of the deflecting force, in the coil also changes. The current setting of relay is expressed in
percentage ratio of relay pick up current to the rated secondary current of CT.

Plug setting multiplier: Plug setting multiplier of relay is referred as ratio of

fault current in the relay to its pick up current.

Suppose the connected protection CT of ratio 200/1 A and current setting is 150%.
Hence, pick up current of the relay is, 1 × 150 % = 1.5 A
suppose fault current in the CT primary is 1000 A. Hence, fault current in the CT
secondary, i.e., in the relay coil is, 1000 × 1/200 = 5A
Therefore PSM of the relay is, 5 / 1.5 =3.33

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Time Setting Multiplier of Relay; The operating time of an electrical relay mainly
depends upon two factors:
1. How long distance to be travelled by the moving parts of the relay for closing relay contacts and
2. How fast the moving parts of the relay cover this distance. adjusting relay operating time, both of the
factors to be adjusted. The adjustment of travelling distance of an electromechanical relay is
commonly known as time setting. This adjustment is commonly known as time setting multiplier of
relay. The time setting dial is calibrated from 0 to 1 in steps of 0.05 sec.
Hence, actual operating time of the relay is 3 × 0.1 = 0.3 sec. i.e. 10% of 3 sec.

Signature of staff in charge

4c. Test the Earth Leakage Relay. (Anyone type). Date:

AIM: to test the opera琀椀on of a earth fault/ earth leakage relay

APPARATUS REQUIRED:
01. Power contactor with 230 V coil voltage.
02. Earth Leakage Relay with suitable CBCT set.
03. Push bu琀琀on switches
04. SPST
05. Lamps

Note: The circuit given above is basically a DOL starter circuit. This may be treated as equivalent to a circuit
breaker (MCCB or ACB) with Earth Fault/Leakage Relay and CBCT. The lamp load may be assumed as the
equipment (motor or generator or transformer) is protected against earth fault. The pickup current and trip

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time should be adjusted using the DIP switches provided on the front face of the Earth Leakage/fault relay.
(Static type relays have dip switches whereas digital relays have touch key pads)

PROCEDURE:
01. Connec琀椀ons are made as per the circuit diagram.
02. Switch ON the main supply switch with SPST switches in open condi琀椀on.
03. Press the ON push bu琀琀on switch so that the lamp is ON.
04. Now close SPST switch and observe the Earth Leakage Relay which will trip the contactor (Circuit Breaker)
05. Note down and verify the tripping 琀椀me and current as per DIP se琀�ngs. (The secondary current of CBCT may be
measured using a ammeter in the CT circuit or using a clamp-on meter)

Result

Signature of staff in charge

4d. Test the Electromechanical over current relay OR over voltage relay Date:

Aim: To Test the Electromechanical over current OR over voltage relay

Apparatus Required
1.Electromechanical over current relay module MCDG 11 – 1NO
2.Current injection kit – 1no
3. patch cords

Circuit Diagram

Sequence of operation

1.reset the rely under test by operating the reset lever and ensure that its trip flag is not showing
2.turn the current control to zero initially by operating the knob in the anti clockwise direction .
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3.reset the count down timer and then set it to about 20sec.
4.reset the time interval meter so that it reads zero.
5.press the output AC current OFF push button .this is necessary to release an internal NC contact.
6.press the output AC current ON push button and adjust the output current to the desired value as indicated by
the digital ammeter provided on the panel.

Procedure
1.make the connection as per circuit diagram
2.set the pick up value of current Ip and actual value of injected current I
3.Calculate and set plug multiplier setting (PSM) PSM = I/I p
4.keep the selector switch in position-2 because of electromechanical type relay corresponding to PSM.
5.draw the charecteristics as per the observed value in the tabular column.
Calculation
PSM = Injected current (I)/ plug setting (P) =
=
=
=
Tabular coloumn
Sl no Injected current(I) Plug setting (P) PSM= I/P Operating time (t) in sec
1 0.5
2 0.5
3 0.5
4 0.5
5 0.5

Result
Signature of staff in charge

5a.Test the Static over Voltage and Under Voltage Relay and Plot its inverse time – Voltage Characteristics. OR

Aim; To test the Static over Voltage and Under Voltage Relay and Plot its inverse time – Voltage
Characteristics
For under voltage
Apaaratus required
1. microcontroller based under voltage relay MV-12
2. single phase voltage injection kit
3. patch cords
Procedures
1. make the connection as per the circuit diagram
2. Set the fault voltage level by using formula Vs =(1- [0.05+∑a]Vn) with nominal voltage Vn=110v.the
relay operates whenever the input voltage is less than 110v .
3. set the operating time of the relay by using formula T=k(0.1+∑t) where k=5.7 sec and t=weight of
switch constant
4. switch on the power supply and vary the current control to set voltage Vs and selector switch
position2
5. observe the operating time of relay
6. compare the displayed value and calculated value of set voltage and operating time
7. Plot the characteristics for the observed value.

Circuit diagram
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 Switchgear and protection Lab Manual (20EE33P)

Tabular column
Sl no Fault voltage Operating time in sec Displayed value
Vs =(1- [0.05+∑a]Vn) Vn =110v T=k(0.1+∑t) where k=5.7 sec

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 Switchgear and protection Lab Manual (20EE33P)

Result: the inverse time voltage characteristics of static under voltage relay is drawn

Signature of staff in charge

5a.Test the Static over Voltage and Under Voltage Relay and Plot its inverse time – Voltage Characteristics. OR
Aim; To test the Static over Voltage Relay and Plot its inverse time – Voltage Characteristics
For over voltage
Apaaratus required
1. Microcontroller based under voltage relay MV-12
2. Single phase voltage injection kit
3. patch cords
Procedures
1. Make the connection as per the circuit diagram
2. Set the fault voltage level by using formula Vs =(1+ [0.05+∑a]Vn) with nominal voltage Vn=110v.the relay
operates whenever the input voltage is less than 110v .
3. Set the operating time of the relay by using formula T=k(0.1+∑t) where k=3.5 sec and t=weight of switch
constant
4. Switch on the power supply and vary the current control to set voltage Vs and selector switch position2
5. Observe the operating time of relay
6. Compare the displayed value and calculated value of set voltage and operating time
7. Plot the characteristics for the observed value.

Circuit diagram

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 Switchgear and protection Lab Manual (20EE33P)

Sl no Fault voltage Operating time in sec Displayed value

Vs =(1+ [0.05+∑a]Vn) Vn =110v T=k(0.1+∑t) where k=3.5 sec
1

Result: the inverse time voltage characteristics of static over voltage relay is drawn

Signature of staff in charge

5a.Test static Over Current Relay (Anyone type of static relay).

5b. Program and test the Numerical over Current/ Earth Fault Relay for Normal inverse curve for various PSM
and TMS and for definite Time operations.
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 Switchgear and protection Lab Manual (20EE33P)

Aim : program and test the numerical over current for definite time operation

Apparatus required
1. Numerical / digital over current relay kit
2. Patch cords
Procedure
1connections are made as per the circuit diagram
2. Switch on the main supply
3. Set the current and time as per the operation procedure of relay
4. Switch off and switch on the main supply then apply the current more than the set value using current
source.
5. Now switch to starts operation and observe the timer, trip condition
6. Set the relay for difference current and time
7. Repeat the steps no 4&5
8. Switch off the main supply and disconnect the circuit

circuit diagram

Result

Signature of staff incharge

5c. Demonstrate multifunctional numerical relays.

6a.Test the operation of Buchholz Relay. Date:
AIM: To test the operation of buchholz relay.

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 Switchgear and protection Lab Manual (20EE33P)
APPARATUS REQUIRED:
1 BUCHHOLZ RELAY TRAINING KIT ------------------------ 01

PROCEDURE:
1. Plug in the power adopter and switch on the mains power supply.
2. Open the main ball valve on the right side with care (oil seals are fragile****).
3. Now turn on the air compressor for fault injection.
4. Now open the fault injection valve and turn on the air compressor.
5. As soon as the air inside buchholz relay fills above 250cc (cubic centimeter) the alarm will raise.
6. Now shut down the fault injection valve and then turn off the air compressor.
7. Now the alarm will be continuous, make sure alarm switch is on, when explaining one can turn off alarm
and then can turn on alarm switch.
8. Now release the fault air through air relief valve and the, oil level should be in the 100cc level close the
valve.
Observation table

Result

Signature of staff in charge

6b. Conduct BDVT on Transformer oil. Date:
Aim: To Conduct BDVT on Transformer oil.

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 Switchgear and protection Lab Manual (20EE33P)

Apparatus required

1. BDV Test kit----0—60V/1KVA -1no

2. Transformer oil –1lit
3. Patch cords

Theory: The sample is taken out from the transformer tank and the BDV of the oil is checked by BDV
tester. The BDV test kit is basically a high voltage unit and the voltage can be regulated from 0–70 KV. The
BDV tester has two electrodes separated by 2.5 mm distance (4.00 mm separation units are also available).
Procedure

1. Collect the 300-400 ml oil sample of transformer oil from the bottom valve of the transformer in a
glass or plastic vessel.
2. Pour the oil sample in oil pot of the machine.
3. Keep the oil pot in open air for 5 Minutes so that air bubble if any gets out
4. Now put the oil sample in the machine.
5. Increase the KV at the rate of 2 KV/Sec and observe the oil sample through a glass window.
6. Continuously observe the oil sample through an inspection window while increasing the voltage.
7. Note down the KV at which sparking is observed in the oil. The voltage at which sparking observed
is the breakdown voltage of oil.
8. Repeat the step No. 4, 5, 6 and 7 for the same sample for six times and note down the breakdown KV
in each case.
9. Take the average of BDV values observed in step 7 and 8.
10. If oil BDV value is above 30 KV, transformer oil is good.
Circuit diagram

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 Switchgear and protection Lab Manual (20EE33P)

The main factors affecting the breakdown voltage of insulating oil are follows.

1. The water is the major contaminant in transformer oil. Moisture delivers charge carriers and
therefore decreases the dielectric withstand strength of the oil.
2. Aging by-products such as acids also deliver charge carriers through dissociation. Additionally
they are surface-active, decreasing the surface tension. Thus they support bubble evolution following
into a decreased dielectric strength.
3. Pressure influences bubble evolution too. With increasing pressure the breakdown voltage increases.
For pressures below the atmospheric pressure the breakdown voltage should decreases.
4. Dry particles of cellulose fibers decrease the breakdown voltage since they support bubble
generation.

Transformer oil BDV Test Report

Result: the breakdown voltage of given transformer oil is observed

Signature of staff in charge

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 Switchgear and protection Lab Manual (20EE33P)

6c. Demo on Restricted earth fault protection of Transformer. Date:

7.Simulate/Test Alternator protection scheme. Date:

8.Simulate/Test the operation Distance Relay. Date:

8b.Simulate/Test the operation of Differential Relay. Date:

9. Test the operation of the LV circuit breaker. Date:

9b. Demonstrate Substation earthing. Date:

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Signature of staff in charge

10.Typical low voltage power distribution panel- Date:

Identify and study the types of contactors- Power contactors and auxiliary contactors.
Dis-assemble, perform preventive maintenance, service, assemble and test the contactors. Testing of control
panel
a. Visual test
b. Insulation test
c. Testing of control circuit.
d. Testing of power circuit
e. Conduct Logic tests

Signature of staff in charge

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 Switchgear and protection Lab Manual (20EE33P)

11a.Install and test Multifunction meter. Date:

AIM: to install and test multifunction meter
APPARATUS REQUIRED
1. MULTI FUNCTION METER -01
2. CT (CURRENT TRANSFORMER) -03
3. PATCH CHORDS As required
4. 3phase load -1
Circuit diagram

PROCEDURE:
1. Make the connection as per the circuit diagram.
2. Connect 3 current transformers to multifunction meter.
3. Connect any line and neutral to auxiliary power supply, auxiliary power supply must be 230v AC.
4. Connect load through Current transformer.
5. Observe the voltage, current, frequency, power factor, active power Wh, apparent power Vah, reactive
power Varh.
Observation table

Sl voltage current frequency pf Active power(WH) Apparent Reactive

no power(VAH) power(VARH)

RESULT:

Signature of staff in charge

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11b. Identify and test various Auxiliary relays Date:

An auxiliary relay is a relay that assists another relay or device in performing an ac琀椀on. It
does this when its opera琀椀ng circuit is opened or closed. These relays are used in nearly
all electronic devices to assist them in func琀椀oning correctly

1. Instantaneous trip relays: whose contacts change instantaneously from the rest position to the working
position when the coil is energized. The contacts return to the rest position when the coil is no longer
energized. This range includes relays with 2 and 4 contacts, with standard operating times (20 ms) or fast
operating times (8 ms). Instantaneous trip relays can operate directly to the tripping and control circuit and
usually have 4 changeover contacts.

2. Trip and lockout relay: Used to ensure that once a circuit breaker has been tripped by the protection
scheme it cannot be reclosed either manually or automatically until the trip relay has been reset . The
reset function may be either manual or electrical. Trip relays with 2 stable positions for the output
contacts. Depending on which coil is energized, the contacts will change from one position to the other.

3. Trip circuit supervision relay: Through a small supervision current the whole circuit is supervised, in
both positions of the circuit breaker (opened or closed). The output contacts change their position if the
relay detects a failure in the continuity of the circuit.

4. Auxiliary supply circuit supervision relay: Since small and reliable silicon diodes are available it is
nowadays common practice to rectify the AC and use ordinary highly reliable DC relays.

Signature of staff in charge

11c. Demonstrate(video) Interlocking operation. Date:

https://www.youtube.com/watch?v=X7reolFx1I4

Signature of staff in charge

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12a.Test the Motor Protection Relay. Date:

AIM: To test the motor protec琀椀on relay.

APPARATUS REQUIRED:
1. MOTOR PROTECTION RELAY -01
2. CONTACTOR------ 01
3. PATCH CORDS AS REQUIRED

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 Switchgear and protection Lab Manual (20EE33P)
UC-UNDER CURRENT
LR-LOCKED ROTOR
EF-EARTH FAULT
SP-SINGLE PHASE PREVENTION
OL-OVER LOAD
AUX -230V AUXILARY POWER SUPPLY
1,2-NORMALLY CLOSED CONTACT
3,4-NORMALLY OPEN CONTACTS

PROCEDURE:
1. Adjust the relay over load settings and earth fault settings.
2. Adjust the DIP switches to on position for locked rotor and under current switches to activate protection.
3. Make the motor connection to load as shown in circuit diagram from KEB source, through relay, to the
motor.
4. Apply the load and test the relay ,by creating faults manually by single phasing and locking the rotor
5. Note: 3phase 440v is dangerous it can destroy the motor and relay or even electric shock.

Result:

Signature of staff in charge

12b.Test the operation of Thermal OLR Date:

AIM: To test the opera琀椀on of thermal over load relay and plot the 琀椀me - current characteris琀椀cs.

Apparatus required
01. Thermal over load relay0-10 A, 415 V
02. Ammeter 0-10A MI
03. 15 A SP switch
04. 10A 0-300 V Single phase Auto-transformer (dimmer-stat)
05. 220V/12V, 20 A Single phase transformer (CURRENT INJECTION).
06. Stop clock / digital watch.

Circuit diagram

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 Switchgear and protection Lab Manual (20EE33P)

PROCEDURE:
1. Connec琀椀ons are made as per the circuit diagram.
2. Adjust the current ra琀椀ng on OLR (using pointer or knob in the front side).
3. Switch ON the main supply by keeping SPST in closed posi琀椀on.
4. Switch ON and the vary the autotransformer and set the ammeter current to the desired test current ( say 1.5 or 2
琀椀mes the rated current of the OLR)
5. Now open the SPST and observe the OLR to trip.
6. Note down the 琀椀me for tripping.
7. Reset the OLR and wait for 10 minutes for the OLR to cool down.
8. Repeat the above experiment for 2.5, 3 , 4 琀椀mes the rated current of OLR).
9. The opera琀椀on of NO and NC of OLR while tripping may be checked with the help of series test lamp as shown in
the circuit diagram.
10. Plot the 琀椀me-current characteris琀椀cs.

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 Switchgear and protection Lab Manual (20EE33P)

Tabular column

Result

Signature of staff in charge

13a.Test the operation of APFC. Date:

AIM: To Test the operation of APFC relay.

APPARATUS REQUIRED:
1. APFC TRAINER KIT----- 01
2. PATCH CORDS AS REQUIRED

THEORY: Automatic Power Factor Control or APFC Panels are mainly used for the improvement of Power
Factor. Power Factor is the ratio of active power to apparent power and it is a major component in measuring
electrical consumption. APFC is an automatic power factor control panel which is used to improve the
power factor, whenever required, by switching ON and OFF the required capacitor bank units automatically

Circuit Diagram

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 Switchgear and protection Lab Manual (20EE33P)

PREVIEW OF VOLTAGE AND CURRENT WAVEFORMS:

The increasing demand of electrical power and the awareness of the necessity of energy saving is very up to
date these days. Also the awareness of power quality is increasing, and power factor correction (PFC) and
harmonic filtering will be implemented on a growing scale. Enhancing power quality – improvement of
power factor – saves costs and ensures a fast return on investment. In power distribution, in low- and
medium-voltage networks, PFC focuses on the power flow (cos Ø ) and the optimization of voltage stability
by generating reactive power – to improve voltage quality and reliability at distribution level.
HOW REACTIVE POWER IS GENERATED: Every electric load that works with magnetic fields (motors,
chokes, transformers, inductive heating, arc welding, generators) produces a varying degree of electrical lag,
which is called inductance. This lag of inductive loads maintains the current sense (e.g. positive) for a time
even though the negative-going voltage tries to reverse it. This phase shift between current and voltage is
maintained, current and voltage having opposite signs. During this time, negative power or energy is
produced and fed back into the network.

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When current and voltage have the same sign again, the same amount of energy is again needed to build up
the magnetic fields in inductive loads. This magnetic reversal energy is called reactive power.

Reactive power compensation systems (detuned /conventional) are installed for larger loads like industrial
machinery. Such systems consist of a group of capacitor units that can be cut in and cut out and which are
driven and switched by a power factor controller
Typical power factor correction circuit diagram:

CALCULATION OF CAPACITOR BANK:

Calculation of KVAR required
In electrical installations, the operating load kW and its average power factor (PF) can be
ascertained from the electricity bill. Alternatively, it can also be easily evaluated by the
formula:
Average PF = kW/kVA
Operating load kW = kVA Demand x Average PF

The average PF is considered as the initial PF and the final PF can be suitably assumed as
target PF. In such cases, required capacitor kVAr can be calculated as explained in the
example below:
Example: To calculate the required kVAr compensa琀椀on for a 500 kW installa琀椀on to improve
the PF from 0.75 to 0.96
CALCULATION OF CAPACITOR BANK:
kVAr required = kW (tan Φ1 - tan Φ2)
where Φ1= cos-1 (PF1) and Φ2 = cos-1 (PF2).
PF1 =0.75
PF1= 0.96
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Φ1= cos-1 (0.75)

Φ1= 41.4096
Φ2 = cos-1 (0.96)
Φ2 = 16.2602
kVAr required = kW (tan Φ1 - tan Φ2)
kVAr required = 500 (tan (41.4096) – tan(16.2602))
kVAr required = 295.1249 =295 KVAR

kW to kVA calcula琀椀on
The apparent power S in kilovolt-amps (kVA) is equal to the real power P in kilowa琀琀s (kW),
divided by the power factor PF:
S(kVA) = P(kW) / PF
S(kVA) = 500(kW) / 0.75 S(kVA) = 500(kW) / 0.96
S(kVA) = 666.66 KVA S(kVA) = 520.88 KVA

Case 1:
Apparent power =666.66 kVA; connected load =500 kW; power factor= 0.75 Current drawn,
I1 =KVA/( √3*V*PF), √3=1.732
I1=666.66 x 1000/(1.732 x 415 x0.75)=1236.61 A
Case 2:
Apparent power =520.88 kVA; connected load =500 kW; power factor= 0.96 Current drawn,
I2 =KVA/( √3*V*PF) , √3=1.732
I2=520.88 x 1000/(1.732 x 415 x0.96)=754.84 A

Observa琀椀on table

RESULT:
APFC (AUTOMATIC POWER FACTOR CONTROL) was studied successfully.

Signature of staff in charge

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 Switchgear and protection Lab Manual (20EE33P)

13b.Test the operation of AMF panel. Date:

AIM: To Test the opera琀椀on of AMF relay.

APPARATUS REQUIRED:
1. AMF TRAINER KIT---- 01
2. PATCH CORDS AS REQUIRED
THEORY: The AMF relay is a micro-controller based unit which automates generator start and stop actions
during mains failure by controlling both mains and generator contactors. It also measures voltage, current
and frequency and displays it on a LCD.

Circuit Diagram

PROCEDURE:
1. Turn off EB incomer and DG incomer mcb in trainer kit .
2. By using patch cords connect load to load terminal.
3. Now connect mains breaker terminal to EB Incomer terminal.
4. Now connect dg breaker terminal to DG incomer terminal.
5. Now provide 3 phase 4wire supply to the AMF trainer kit.
6. After providing power supply to the kit the AMF relay automatically senses the voltages in the DG and EB
incomer terminal, now the EB & DG mcb is off so it senses power failure.
7. Now the AMF relay automatically sends signal to start DG (observe the FUEL SOLENOID DG START
indicator glowing).
8. Now turn on DG Incomer mcb and after few seconds AMF relay automatically closes DG incomer to
LOAD.

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 Switchgear and protection Lab Manual (20EE33P)

9. Now turn on EB Incomer MCB and after few seconds AMF relay automatically opens DG incomer and
switches EB incomer breaker to the load.
10. When the FUEL SOLENOID DG START indicator turns off manually open the DG INCOMMER
MCB.
11. If AMF relay raises alarm at any point reset the relay and continue the procedure.
12. Always keep the AMF relay in AUTO mode only.

RESULT: Study of AMF relay was conducted successfully.

Signature of staff in charge

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 Switchgear and protection Lab Manual (20EE33P)

1 Portfolio evaluation of Practice Sessions (week1-week13) - 10Marks

2. i. Selection of switch gears and its ratings for given application. – 5marks
There are many devices designed to interrupt power, from a source to a load, and they each
have di昀昀erent functions and characteristics. Selecting the right device for the right application
is therefore vital.
Miniature Circuit Breakers (MCBs) are probably the most common form of protective
device used in electrical installations. rating of MCB for single pole and four pole are 6A to 32
A

Moulded Case Circuit Breakers (MCCBs) or simply circuit breakers (CBs), are commonly
used for sub-main distributing loads in switchgear. Rating of MCCB with three pole is from
100A to 1000A.

Air Circuit Breakers (ACBs) are often used at the origin of larger installations, due to their
rating and ability to withstand high levels of faults. the available rating of ACB is above 600A.

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Motor Protection Circuit Breakers (MPCBs), as their name implies, are speci昀椀cally
designed to protect motors, compressors and other motive power loads. Like a typical MCCB,
these devices o昀昀er additional protection against motor overload and phase loss in balanced 3-
phase systems. The available rating of MPCB is from 10A onwards.

ii. Selection of MCB rating and class as per applications / selection of fuse rating and type for given
application.
- 5marks
Selection of MCB rating and class as per applications

The current rating is the value of the current over which the breaker gets tripped. The Rated current of the
MCB to be used depends on the load current of the equipment to be protected. For a typical MCB, this rating
is 6 amperes to 125 amperes. They are available in the following ratings: 6A, 10A, 16A, 20A, 25A, 32A,
45A, 50A, 63A, 80A, 100A, 125A. For example, if you use AC in your then it is advisable to use 20 amps
MCB. 6 amps

Type B Miniature Circuit Breakers: type B MCB trips when the current is 3 to 5 times the rated current with
an operating time of 0.04 to 13 Seconds. It is used for purely resistive loads that are non-inductive loads or
with a very small inductive load which has no considerable amount of inductance. These types are mainly
used for low power domestic applications like lighting circuits, home wirings, etc.
Type C Miniature Circuit Breakers: Type C operates for a current value of 5 to 10 times than the rated current
with an operating time of 0.04 to 5 Seconds. These are used with inductive loads like motors, fans,
transformers, etc. where have a chance of sudden current rush or surges.Mainly used in commercial and
industrial applications.
Type D Miniature Circuit Breakers: Type D has a trip current of 10 to 20 times than the rated current with an
operating time of 0.04 to 3 Seconds. It is used for very high inductive loads.Mainly used in high power
industrial applications for types of equipment like heavy motors, transformers, x-rays, welding, etc.
Type K Miniature Circuit Breakers: Type K trip when the current reaches 8 to 12 times than the rated current
with an operating time of less than 0.1 Second. These are used for inductive loads which have a chance of
high inrush currents.
Type Z Miniature Circuit Breakers: Type Z MCBs operates for a current value between 2 to 3 times the rated
current with an operating time of less than 0.1 Second.

Type A, K and Z MCBs have extremely small operating time compared to type B, C, and D MCBs. Class A,
K, and Z are highly sensitive breakers which operate very quickly in a short time used to protect sensitive
devices.

Selection of fuse rating and type for given application.

Once the current value is determined, then a fuse rating should be selected as to be 125% of this value (taken
to the next standard value).
For example, if the normal steady-state current is calculated to be 10 amps, then a 15A fuse rating should be
selected [10 amps x 125% = 12.5 amps, the next larger standard size is 15A].

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It is important to note that if the fuse is intended to be used in an environment with possibly very high or low
ambient temperatures, then the nominal fuse current would need to be sized significantly higher or lower.

Rating Size of Fuse

While selecting the proper fuse and its rated size for electrical appliances are based on different factors and
environments. But the following basic formula shows how to choose the right size of fuse
Fuse Rating = (Power / Voltage) x 1.25
(1000W / 230V) x 1.25 = 5.4A
In the above example, 1kW is the power rating which can be controlled and the main supply voltage is single
phase 230V AC.
But you should go for the maxes i.e. 6A fuse rating instead of 5.4A for safe and reliable operation of the
circuit.

DC Fuses
1. CARTRIGE FUSE: This is the most common type of fuse. The fuse element is encased in a glass
envelope that is terminated by metal caps. The fuse is placed in an appropriate holder; it is easy to visually
determine if the fuse is blown. Cartridge fuses also exist for direct PCB mounting. it is available from
1Ampsto 5Amps

2. AUTOMOTIVE FUSE: These fuses are specifically designed for automotive systems that run up to
32V and occasionally 42V. They come in ‘blade’ form (a transparent plastic envelope with flat contacts) and
are colour coded according to rated current. Some of these types are also used in other high-power
circuits.1Amps to 20Amps.

AC FUSES
LOW VOLTAGE FUSES: These fuses are used in the relatively low voltage distribution networks.
3. CARTRIDGE FUSES: They are very similar to cartridge DC fuses. They consist of a transparent envelope
surrounding the fuse element. They can be plugged in (blade type) or screwed into a 昀椀xture (bolt
type).1Amps to
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4. DROP OUT FUSES: They contain a spring-loaded lever arm that retracts when a fault occurs
and must be rewired and put back in place to resume normal operation. They are a type of
expulsion fuse.

5. REWIREABLE FUSE: They are a simple reusable fuse used in homes and o昀케ces. They
consist of a carrier and a socket. When the fuse is blown, the carrier is taken out, rewired and
put back in the socket to resume normal operation. They are somewhat less reliable than HRC
fuses.

6. STRIKER FUSE: These fuses are provided with a spring-loaded striker that can act as a
visual indicator that the fuse has blown and also activate other switchgear.

7. SWITCH FUSE: A handle that is manually operated can connect or disconnect high current
fuses.

HIGH VOLTAGE FUSES: These fuses are used in high voltage AC transmission lines where
voltages can exceed several hundreds of kilovolts.
8. HRC (HIGH RUPTURE CURRENT) FUSES: HRC fuses are cartridge type fuses consisting of a transparent
envelope made of steatite (magnesium silicate). The fuse is filled with quartz powder (and in the case of a liquid-filled
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HRC fuses, a non-conducting liquid like mineral oil) that acts as an arc extinguishing agent. These fuses are used for
very high fault currents.

9. EXPULSION FUSES: These fuses are 昀椀lled with chemicals like boric acid that produce gases
on heating. These gases extinguish the arc and are expelled from the ends of the fuse. The
fuse element is made of copper, tin or silver.

10. HORN GAP FUSE: The main function of Horn Gap Fuse Set is to protect transformer and system for
interrupting large currents by disconnecting transmission power distribution lines

3. Demonstrate the operation of a given Switchgear and plot its characteristics -60 marks
i. Drawing of the Circuit diagram using the right symbols 15 marks
ii. Demonstrate testing of (relay/fuse/MCB) for a Given operation 30marks
iii. plotting the characteristics 15marks

1.Test the Earth Leakage Relay

AIM: to test the opera琀椀on of a earth leakage relay
APPARATUS REQUIRED:
01. Power contactor with 230 V coil voltage.
02. Earth Leakage Relay with suitable CBCT set.
03. Push bu琀琀on switches
04. SPST
05. Lamps

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 Switchgear and protection Lab Manual (20EE33P)

PROCEDURE:
01. Connec琀椀ons are made as per the circuit diagram.
02. Switch ON the main supply switch with SPST switches in open condi琀椀on.
03. Press the ON push bu琀琀on switch so that the lamp is ON.
04. Now close SPST switch and observe the Earth Leakage Relay which will trip the contactor (Circuit Breaker)
05. Note down and verify the tripping 琀椀me and current as per DIP se琀�ngs. (The secondary current of CBCT may be
measured using a ammeter in the CT circuit or using a clamp-on meter)

Result
2.Operation of Thermal OLR

AIM: To test the opera琀椀on of thermal over load relay and plot the 琀椀me - current characteris琀椀cs.
Apparatus required
01. Thermal over load relay0-10 A, 415 V
02. Ammeter 0-10A MI
03. 15 A SP switch
04. 10A 0-300 V Single phase Auto-transformer (dimmer-stat)
05. 220V/12V, 20 A Single phase transformer (CURRENT INJECTION).
06. Stop clock / digital watch.

Circuit diagram

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 Switchgear and protection Lab Manual (20EE33P)

PROCEDURE:
1. Connec琀椀ons are made as per the circuit diagram.
2. Adjust the current ra琀椀ng on OLR (using pointer or knob in the front side).
3. Switch ON the main supply by keeping SPST in closed posi琀椀on.
4. Switch ON and the vary the autotransformer and set the ammeter current to the desired test current ( say 1.5 or 2
琀椀mes the rated current of the OLR)
5. Now open the SPST and observe the OLR to trip.
6. Note down the 琀椀me for tripping.
7. Reset the OLR and wait for 10 minutes for the OLR to cool down.
8. Repeat the above experiment for 2.5, 3 , 4 琀椀mes the rated current of OLR).
9. The opera琀椀on of NO and NC of OLR while tripping may be checked with the help of series test lamp as shown in
the circuit diagram.
10. Plot the 琀椀me-current characteris琀椀cs.
Tabular column

Result

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 Switchgear and protection Lab Manual (20EE33P)

3.Test the Electromechanical over current relay

Aim: To Test the Electromechanical over current OR over voltage relay

Apparatus Required
1.Electromechanical over current relay module MCDG 11 – 1NO
2.Current injection kit – 1no
3. patch cords

Circuit Diagram

Sequence of operation

1.reset the rely under test by operating the reset lever and ensure that its trip flag is not showing
2.turn the current control to zero initially by operating the knob in the anti clockwise direction .
3.reset the count down timer and then set it to about 20sec.
4.reset the time interval meter so that it reads zero.
5.press the output AC current OFF push button .this is necessary to release an internal NC contact.
6.press the output AC current ON push button and adjust the output current to the desired value as indicated by
the digital ammeter provided on the panel.
Procedure
1.make the connection as per circuit diagram
2.set the pick up value of current Ip and actual value of injected current I
3.Calculate and set plug multiplier setting (PSM) PSM = I/I p
4.keep the selector switch in position-2 because of electromechanical type relay corresponding to PSM.
5.draw the charecteristics as per the observed value in the tabular column.
Calculation
PSM = Injected current (I)/ plug setting (P) =
=
=
=

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 Switchgear and protection Lab Manual (20EE33P)

Result

4.Demonstrate testing of fuse for a given operation and plot its characteristics
Aim: To test the fuse by performing a Load test.

Apparatus required

1. fuse wire - 0- 15A

2. resistive load – 10-20A
3. fuse board
4. Autotransformer

Circuit diagram

Tabular column

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 Switchgear and protection Lab Manual (20EE33P)

Result:

5. Demonstrate testing of MCB for a given operation and plot its characteristics
AIM: study the opera琀椀on of MCB and plot the opera琀椀ng characteris琀椀cs .MCB has two characteris琀椀cs.
1. Inverse 琀椀me characteris琀椀cs during over load.
2. Instantaneous characteris琀椀cs during short circuit

APPARATUS REQUIRED:
01. Single Pole MCB (preferably lower ra琀椀ng like 6 A)
02. Ammeter 0-10A MI
03. 15 A SPST switch.
04. Single phase Auto-transformer (dimmer-stat) 0-300 V 10A
05. Resis琀椀ve load, 10 A single phase.
06. Stop clock / digital watch.

CIRCUIT DIAGRAM

PROCEDURE:
1. Connec琀椀ons are made as per the circuit diagram.
2. Do not on MCB
3. Connect the shor琀椀ng link between dashed line
4. Switch on the current injec琀椀on source and set current to the ra琀椀ng of MCB and observe this current in
meter.
5. Switch o昀昀 the current injec琀椀on unit and remove the shor琀椀ng link.
6. Now switch on the current injec琀椀on kit and observe the tripping of MCB
7. Repeat the above procedure for 2 and 3 琀椀mes the rated current of the MCB.
8. in each step note down the 琀椀me taken by the MCB to trip
9. Plot the 琀椀me-current characteris琀椀cs.

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 Switchgear and protection Lab Manual (20EE33P)
TABULAR COLOUMN

Result

OR

Demonstration of protection scheme -60marks

i. Drawing of the Circuit diagram using the right symbols 05marks
ii. Simulate/ Demonstrate working of protection scheme 55marks

1.
Aim; To test the Static Under Voltage Relay and Plot its inverse time – Voltage Characteristics

Apparatus required
4. microcontroller based under voltage relay MV-12
5. single phase voltage injection kit
6. patch cords
Procedures
8. make the connection as per the circuit diagram
9. Set the fault voltage level by using formula Vs =(1- [0.05+∑a]Vn) with nominal voltage Vn=110v.the
relay operates whenever the input voltage is less than 110v .
10. set the operating time of the relay by using formula T=k(0.1+∑t) where k=5.7 sec and t=weight of
switch constant
11. switch on the power supply and vary the current control to set voltage Vs and selector switch
position2
12. observe the operating time of relay
13. compare the displayed value and calculated value of set voltage and operating time
14. Plot the characteristics for the observed value.

Circuit diagram

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 Switchgear and protection Lab Manual (20EE33P)

Tabular column
Sl no Fault voltage Operating time in sec Displayed value
Vs =(1- [0.05+∑a]Vn) Vn =110v T=k(0.1+∑t) where k=5.7 sec
1

Result: the inverse time voltage characteristics of static under voltage relay is drawn

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 Switchgear and protection Lab Manual (20EE33P)

2. Test the operation of Buchholz Relay

AIM: To test the operation of buchholz relay.

APPARATUS REQUIRED:
1 BUCHHOLZ RELAY TRAINING KIT ------------------------ 01

PROCEDURE:
1. Plug in the power adopter and switch on the mains power supply.
2. Open the main ball valve on the right side with care (oil seals are fragile****).
3. Now turn on the air compressor for fault injection.
4. Now open the fault injection valve and turn on the air compressor.
5. As soon as the air inside buchholz relay fills above 250cc (cubic centimeter) the alarm will raise.
6. Now shut down the fault injection valve and then turn off the air compressor.
7. Now the alarm will be continuous, make sure alarm switch is on, when explaining one can turn off alarm
and then can turn on alarm switch.
8. Now release the fault air through air relief valve and the, oil level should be in the 100cc level close the
valve.
Observation table

Result

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 Switchgear and protection Lab Manual (20EE33P)

3.Test the Motor Protection

AIM: To test the motor protec琀椀ve device against single phasing and overload
APPARATUS REQUIRED:
1. MOTOR PROTECTION RELAY -01
2. CONTACTOR------ 01
3. PATCH CORDS AS REQUIRED

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 Switchgear and protection Lab Manual (20EE33P)
UC-UNDER CURRENT
LR-LOCKED ROTOR
EF-EARTH FAULT
SP-SINGLE PHASE PREVENTION
OL-OVER LOAD
AUX -230V AUXILARY POWER SUPPLY
1,2-NORMALLY CLOSED CONTACT
3,4-NORMALLY OPEN CONTACTS

PROCEDURE:
1. Adjust the relay over load settings and earth fault settings.
2. Adjust the DIP switches to on position for locked rotor and under current switches to activate protection.
3. Make the motor connection to load as shown in circuit diagram from KEB source, through relay, to the
motor.
4. Apply the load and test the relay ,by creating faults manually by single phasing and locking the rotor
5. Note: 3phase 440v is dangerous it can destroy the motor and relay or even electric shock.

Result:

OR
Testing of control panel wiring in LV control panels 60marks
i. Reading electrical drawings and demonstrate control panel wiring 15marks
ii. cable size and bus bar rating selection for given application. 15marks
iii. Testing control panel – Tracing control wiring, identifying components as per IEC and ANSI codes, test the
components. 30marks

i. Reading electrical drawings and demonstrate control panel wiring -10marks

1. Familiarize with Standardized Electrical Symbols

Knowing the meanings of basic electrical symbols in your electrical drawing will
help you quickly understand and troubleshooting the circuit.

A fuse is represented by a slight zigzag in the line. Motors are displayed by bumps along the line. It looks
like an "M" with 5 or 6 humps.

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The ground is represented by either a triangle pointing down or a set of parallel

lines that become shorter as they appear below each other, in e昀昀ect representing

the inner area of the triangle pointing down

Wires are used to link the devices together. All points along the wire are identical
and connected. Wires may cross each other on an electrical drawing,.

2. Learn Reading Pattern: Read schematics in the pattern that you would read the text. With rare
exceptions, schematics should be read left to right and top to bottom. The signal generated or used by the
circuit will flow in this direction. The user can follow the same path that the signal uses to understand what
the signal does or how it is being modified.

3. Identify Polarity: Some components to a circuit board are polarized, meaning that one
side is positive and the other negative. It means that you have to attach it in a speci昀椀ed
way. For most symbols, polarity is included in the symbol. To identify the polarity of the
physical part, a general rule of thumb is to 昀椀nd out which metal lead wire is longer. The
longer part is the + side.
4. Understand Names and Values: Values help define what a component is. For electrical
components like contactor,circuit breaker,fuse etc the value shows the rating

Component names usually consist of one or two letters and a number. The letter
part of the name represents the type of component circuits, etc. Each component
name in an electrical drawing should be unique. Components' names help us
reference speci昀椀c points in schematics. The pre昀椀xes of names are pretty well
standardized

Control panel wiring

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ii. Cable size and bus bar rating selection for given application. -10marks
find out the size of cable required to connect into incomming of control panel for the onnected load
10HP,20HP,15HP ,5HP ,440V,50HZ ,PF=0.8 AC power supply.

50,000/1.732*440*0.8
82Amps
factor of safety for future extension= 82x2 164 Amps
35sqmm cable is selected from given chart as a incomming cable into control panel

Busbar rating
Bus bar rating is calculated 120% of total load current
Therefore 1.2 times of load current
164x1.2= 196.8 Amps
The busbar rating for a given cintrol panel is 200Amps.

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iii. Testing control panel – Tracing control wiring, identifying components as per IEC and ANSI codes, test the
components- 20marks

To trace a wire with a multimeter, set multimeter to continuity; place your red probe on one wire ending and
then place the black probe on a suspected ending. If the multimeter reads “0” or beeps, then that is where the
wires traces to and use a multimeter to do a point-to-point continuity check on all wiring based on the
electrical drawings.

The insulation resistance shall be checked across earth and every control wiring in the panel. The insulation
resistance should be mega ohms.

Tracing Wires with Electrical Testers

Types of Electrical Testers and How to Use Them

1. Electrical Wire Testers

a. There are a many great testers that can be used to identify wiring .
2. Non-Contact Voltage Testers
a. One type of tester is the Non-Contact Voltage Detector which can be used to detect voltage in
wires and cables.
3. Testing for Broken Wires
a. This non contact tester can also find breaks in electric wires, and helps to identify the hot and
neutral conductors.

The most common control panel components are,

1. Enclosure
2. bus bar
3. incomer
4. cables
5. Terminal Blocks
6. Circuit Breaker
7. Isolators
8. Protective Devices
9. Relays
10. Indication Lamps
11. Buzzer
12. Cooling Fan
13. Connectors
14. Contactors
15. Timers
16. Wire Duct
17. CT and PT
18. Measuring Instruments
19. Power Supply
CONTROL PANEL: Control panel is a metal box, usually made of aluminium or stainless steel that serves to be the
body of the control panel. It consists of power, control components,indicators,measuring instruments,busbar etc.
CABLES: Cables are used for the interconnection. Two types of cables are used. Power cable and control
cable.
INCOMER: The main supply is connected to this incomer.
BUS BAR: Incoming supply is connected to bus bar and distributed from bus bar. It is normally made by
Aluminum .
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Fuses - Fuse protect loads from pulling too much current

Terminals Blocks: A terminal block is an arrangement that makes electrical connection easy, safe, and
simple. Circuit Breaker: A circuit breaker is an electrical protective device that breaks a circuit automatically
when a short circuit or overload fault occurs.

Isolator: An isolator is a device that is used to isolate or disconnect a circuit from a power source
completely with a hundred percent surety.

Protective Devices: Other important protective devices used in control panels are Fuses, ELCB(Earth
Leakage Circuit Breaker), RCCB(Residual Current Circuit Breaker), MPCB(Motor Protection Circuit
Breaker), Phase Sequence Meter, Surge Protector, etc.

Relays: Relays are used in the control panel for controlling, sensing, switching, detecting, and indicating
purposes.

Indication Lamps: Indication Lamps are also known as pilot lamps. Indication lamps are used in electrical
control panels to indicate whether a circuit is on, off, or tripped condition

SELECTOR SWITCH: Selector is switch is used for ON/OFF purpose and for selec琀椀ng the mode of opera琀椀on
like auto/manual.

Buzzer: Buzzers is used in the in control panels to aware operators during any fault or abnormal condition.

Cooling Fan; Cooling Fans are also used in the control panels to cool the heat produced during their
operation.

Measuring Instruments; measuring instruments such as voltmeter, ammeter, wattmeter, energy meter,
frequency meter to measure the electrical quantities.

MCB (Miniature Circuit Breakers): MCB is a protecting device.

MCCB (Mould Case Circuit Breaker): MCCB used as an incomer for higher capacity protec琀椀on

TESTING OF COMPONENTS

BUSBAR: Three of the most important tests performed on the busbar are the High Potential and the Insulation
resistance test, also known as a Megger Test

CABLE-Load test: the cable is energized to1.5 times the working voltage. The cable should not show any
sign of damage.
Thermal test; the cable is energized with a voltage 1.5 times the working voltage for a cable of 132 kV
rating and the loading current is so adjusted that the temperature of the core of the cable is 5°C higher than
its specified permissible temperature.
RELAY: Energize the electromagnet coil with a 9-12V battery across the pins. The relay should make an
audible "click" as the electromagnet coil energizes and closes the switch.

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CLOSING AND OPENING TIME OF ISOLATOR: Closing and opening time of isolator contacts is
needed to check whether they are operating within specified permissible time limit or not. For this purpose
we can use stopwatch.

4. Viva voce- 20marks

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