VPKBIET BARAMATI
ELECTRICAL DEPARTMENT
VOL. 1
VIDYA PRATISHTHAN’S
Kamalnayan Bajaj Institute of Engineering and Technology Vidyanagari, Bhigwan Road, Baramati, Dist. Pune – 413 133. Web: www.vpkbiet.org
DEPARTMENT OF ELECTRICAL ENGINEERING
LABORATORY MANUAL
SUBJECT: SWITCHGEAR AND PROTECTION [SUBJECT CODE: 403147]
CLASS: B.E. (ELECTRICAL) YEAR: 2016-17
APPROVED BY:
Subject Teacher
H.o.D. [Electrical] Prepared by Mr. rohit s. tarade
VALIDITY UP TO: ACADEMIC YEAR 2017 – 2018
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VPKBIET BARAMATI
ELECTRICAL DEPARTMENT
VOL. 1
VIDYA PRATISHTHAN’S
Kamalnayan Bajaj Institute of Engineering and Technology Vidyanagari, Bhigwan Road, Baramati, Dist. Pune – 413 133. Web: www.vpkbiet.org
B. E (Electrical) – Switchgear and protection
Experiment No: Title: ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Class: b. e Electrical
Batch: ------------------
Roll No: ----------------------------
Date: ---------------------
Sign: -------------------------------------
Grade: -----------------
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ELECTRICAL DEPARTMENT
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LIST OF EXPERIMENTS EXP.NO:
LIST OF EXPERMENTS
1
Study of Operational Working of Switchgear/Protective Relay Testing System
2
Fusing Factor of Rewirable Fuse
3
Study the Fusing Characteristics of Fuse Element
4
Study of Miniature Circuit Breaker (MCB) & their testing
5
Study & testing of contactors
6
Study & testing of MCCB.
7
Study & testing of thermal overload relay for Induction Motor protection
8
Study & plotting Characteristics of IDMT type Induction over current relay
9
Percentage differential protection of transformer
10
Protection of alternator
11
Protection of Transmission line using P441 relay
3
PG. NO:
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ELECTRICAL DEPARTMENT
VOL. 1
GUIDELINES FOR WRITING AN OBSERVATION BOOK
1. Experiment Title, Aim, Apparatus, Procedure should be on right side. 2. Circuit diagrams, Model graphs, Observations table, Calculations table should be left side. 3. Theoretical and model calculations can be any side as per your convenience. 4. Result should always be in the ending. 5. You all are advised to leave sufficient no of pages between experiments for theoretical or model calculations purpose.
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DO’S AND DON’TS IN THE LAB DO’S:1. Proper dress has to be maintained while entering in the Lab. (Boys Tuck in and shoes, girls with apron) 2. Students should carry observation notes and record completed in all aspects. 3. Student should be aware of operating equipment. 4. Students should be at their concerned experiment table, unnecessary moment is restricted. 5. Student should follow the indent procedure to receive and deposit the equipment from the Lab Store Room. 6. The results must be shown to the Lecturer In-Charge for verification. 7. Students must ensure that all switches are in the OFF position. DON’Ts:1. Don’t come late to the Lab. 2. Don’t enter into the Lab with Golden rings, bracelets and bangles. 3. Don’t make or remove the connections with power ON. 4. Don’t switch ON the supply without verifying by the Staff Member. 5. Don’t leave the lab without the permission of the Lecturer In-Charge.
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ELECTRICAL DEPARTMENT
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EXPERIMENT NO. : Study of Operational Working of Switchgear/Protective Relay
Testing System AIM: Study of Operational Working of Switchgear/Protective Relay Testing System APPARATUS REQUIRED:
Patch Cords
Protective Relay Technical Specifications S. No. Equipment 1. Mains Supply 2. DC Variable Source
Ratings 230V ±10%, 50Hz 0-500V
3.
AC Variable Source
0-500V
4. 5. 6. 7. 8. 9.
AC Current Source Digital Meters : AC Voltmeter DC Voltmeter AC Current Time interval Meter with reset MCB
0-200V 1 No. 1 No. 1 No. 1 No. 1 No.
10.
1No. (TPN)
PRE-LAB: 1. How the electrical power system protection is divided? The overall system protection is divided into
Generator protection
Transformer protection
Bus bar protection
Transmission line protection and Feeder protection 2. What is the function of circuit breaker in the Power system?
It is one of the protective equipments in substation. The main function of the CB is to open or close a circuit under normal as well as fault conditions. 3. What are the major electrical equipments used in the power system? Generator, power transformer, bus bars, circuit breakers, switching circuits
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ELECTRICAL DEPARTMENT
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THEORY: Power System: An electric power system is a network of electric components used to supply, transmit and use electric power
Power system can be broadly divided into:
Generation system Transmission system Distribution systems Components of Power System:
Supply Transformer Loads Protective devices
Need of protective devices: Power systems contain protective devices to prevent injury or damage during failures. Protection devices 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. Choices of protective devices vary according to the strength of power in the system. Earlier, Safety fuses were used in lower powered applications but now-a-days, in lower powered applications, miniature circuit breakers are used and in higher powered applications, protective relays are used. Early relays’ working was based upon electromagnetic principles, but modern relays are application-specific computers that determine whether to trip based upon readings from the power system. Different relays initiate trips depending upon different protection schemes.
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Faults in power system: Line faultsElectrical line faults are characterized as:
Line to Ground Fault Line to Line Fault Line-Line to Ground Fault L-L-L Fault(Line-Line-Line Fault) L-L-L-G Fault(Line-Line-Line to Ground Fault)
Line to Ground Fault: In this type of Electrical fault all the three sequence components (positive, negative and zero sequence components) are present and are equal to each other. In case of isolated neutral connection to the generator, there will be no return path for the current. So for such fault, fault current is zero. Line to Line fault: These are unsymmetrical faults as these faults give rise to unsymmetrical currents (Current differ in magnitude and phase in the three phases of power system).In case of Line to Line fault, positive and negative sequence component of current are present, they are equal in magnitude but opposition in phase. Zero sequence components are absent. Line-Line to Ground Fault: These faults are of unsymmetrical nature. In this type of faults negative and zero sequence faults are in opposition with positive sequence components. Line-Line-Line Fault: This type of faults are called symmetrical fault. Such types of faults occur very rarely but are more severe as compared to other faults. In these faults, negative and zero sequence component currents are absent and positive sequence currents are present. To summarize:
Positive sequence currents are present in all types of faults
Negative Sequence currents are present in all unsymmetrical faults 8
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Zero sequence currents are present when the neutral of the system is grounded and the fault also involves the ground, and magnitude of the neutral currents is equal to 3Io. Open circuit faults:
These faults are caused either due to parting of the overhead line or due to the partial opening of pole of the circuit breaker.
Overloading:
Overloading can occur due to various reasons.Generally,overloading takes place when excess amount of current flows through a single conductor.It can also occur due to the sudden hike in supply voltage.
Interturn faults:
Interturn faults occur in machines i.e. Transformers, Motors and Generators. An Interturn fault occurs due to the insulation breakdown between the turns of the same phase or between the parallel windings belonging to the same phase of the machine. The cause of the interturn fault is usually an overvoltage or mechanical damage of the insulation. Protective Device: All electrical circuits must be protected against over current therefore a protective device has to be installed in order to isolate the fault from the supply so as to protect the equipment and appliances from being damaged. Over current is caused by: Short circuit
Two or more live conductors touching each other
Overload
Adding loads greater than that of the rated value
Earth fault
A phase conductor touching the protective conductor by means of direct or indirect contact
Relay:
A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. Each relay contains a few simple parts that all work together to allow the relay to function. A simple relay contains the following components: 9
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Electromagnet-It controls the opening and closing of relay. Armature-It actually opens and closes. Spring-Spring forces the relay back to its original state after each cycle. Set of electrical contacts-For transferring of power.
Application of Relays:
Amplification of a digital signal: Relays can be used for switching a large amount of power with a small operating power. Some special cases are: A telegraph relay, repeating a weak signal received at the end of a long wire
Controlling a high-voltage circuit with a low-voltage signal, as in some types of modems or audio amplifiers,
Controlling a high-current circuit with a low-current signal, as in the starter solenoid of an automobile,
As a protective device:-Detect and isolate faults on transmission and distribution lines by opening and closing circuit breakers (protection relays)
Isolate the controlling circuit from the controlled circuit when the two are at different potentials, for example when controlling a mains-powered device from a low-voltage switch. The latter is often applied to control office lighting as the low voltage wires are easily installed in partitions, which may be often moved as needs change. They may also be controlled by room occupancy detectors to conserve energy, Implementation of Logic functions:-For example, the Boolean AND function is realized by connecting normally open relay contacts in series, the OR function by connecting normally open contacts in parallel. The change-over or Form C contacts perform the XOR (exclusive or) function. Similar functions for NAND and NOR are accomplished using normally closed contacts.
Protective relays: · ·
For protection of electrical apparatus and transmission lines, electromechanical relays with accurate operating characteristics were used to detect overload, short-circuits, and other faults. Such relays are called protective relays. These relays monitor the current, voltage, frequency, or any other type of electric power measurement either from a generating source or to a load for the purpose of triggering a circuit breaker to open in the event of an abnormal condition.
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· ·
Basic Connection diagram of Protection relay
PRECAUTIONS: 1. All connections should be tight. 2. Don’t touch live terminals. 3. The meter used should be of proper range. 4. The zero settings of the various instruments should be checked before switching the circuit on. 5. Don’t insert the resistance in field winding, when motor begins to start. 6. In case starter for d.c motor is not available, rheostat of proper rating should be used in the armature circuit. 7. Reading should be obtained carefully.
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ELECTRICAL DEPARTMENT
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CIRCUIT DIAGRAM:
PROCEDURE: First make sure that three phase mains supply is ‘Off’.
For Using AC and DC Voltage Source.
Connect three phase variable supply to the testing system
Switch On three phase MCB provided at the testing system and vary three phase variac knob (connected externally) upto 415V
By the time user varies three phase supply, three phase indicator with respective color will glows, shows three phase supply appears on testing system As shown in above figure, there is a separate switch to enable AC and DC Voltage Source 12
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ELECTRICAL DEPARTMENT
VOL. 1
Now user has an option to either use AC Voltage or DC Voltage source at the same time, for the same, one more switch is there (placed at the middle of selector switch as shown in above figure) to select EITHER AC or DC SOURCE.
Turn the switch to AC Voltage Source and make sure that DC Voltage source mains switch is at Off position Now, as shown in figure, two push button switches are there which helps user to increase or decrease the voltages as per their application and that can go upto 500V
Now to use DC Voltage Source.
Firstly, ensure that AC Source is at zero volt or else DC Voltage source will not operate
Now turn Off AC Voltage Source Mains Switch and Move the middle switch to DC Position.
· ·
Now turn On DC Voltage Source Mains Switch and increases / decreases voltage by using available push button switch. After completing respective experiment, make sure that either of the Voltage Source is at zero volts or else, it will not operate again Reduce three phase supply to zero volt by using three phase variac and turn all the selector switch from AC or DC Voltage source is at Off position.
Now to analyze AC Current Source Section
Make sure that AC Current source knob is at zero position as shown in above figure.
Turn the selector switch (placed at Current Source Section) at On position and press green push button to enable the same.
Digital timer is provided to count the tripping time of the IDMT Relay.
Toggle switch is placed just below the digital timer meter to stop or start the timer, it is usually at upward side to start the timer.
User need to connect IDMT Relay at current source terminal so that system start injecting current based on the rating of Relay At the right side of the testing system, as shown in above figure, one selector switch is there with selecting option as “SET”, “Off” and “TEST” When user select “SET” option, means user can set the current for which they want relay to get tripped 13
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ELECTRICAL DEPARTMENT
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When user select “TEST” option, means user enables RELAY and test its current versus time characteristic. Also at this, digital timer will stops by the time relay gets tripped so that user can record this value into observation table. At just below to this switch, N-O and N-C points are there, which user will have to use while testing IDMT or any Current Relay with shorted N-C points itself and connect N-O to respective N-O terminal of Relay. After conducting experiments, make sure that all the switches are at Off position, current source is at zero position and three phase mains as well as its MCB is Off.
POST –LAB: 1. What is protective relay 2. How relays are connected in the power system? 3. What are the different relays that employed for protection of apparatus and transmission lines?
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EXPERIMENT NO.
VOL. 1
: FUSING FACTOR OF REWIRABLE FUSE
AIM: Fusing Factor of Rewirable Fuse APPARATUS REQUIRED: Switchgear Testing Kit, Rewirable Fuse Element, Flexible Wires, Fuse Wires
TECHNICAL SPECIFICATIONS S. No. 1. 2.
Equipment Mains Supply DC Variable Source
Ratings 230V ±10%, 50Hz 0-500V
3.
AC Variable Source
0-500V
4. 5. 6. 7. 8. 9.
AC Current Source Digital Meters : AC Voltmeter DC Voltmeter AC Current Time interval Meter with reset MCB
0-200V 1 No. 1 No. 1 No. 1 No. 1 No.
10.
1No. (TPN)
PRELAB: 1. What is mean by HRC Fuse? 2. What is the difference between MCB, MCCB, RCCB, and ELCB? CIRCUIT DIAGRAM
:
Circuit Diagram: Fusing Factor of Rewirable Fuse
Sw itch
20 A
Com.
230 V A . C. Supply
(0 -300 V )
V 20 - 100 A
A uto-2 CR
Current Source TR-2
Com. Zero Current Detector A
Pow er Contact To Stop
15
(0 - 500 A ) Timer Command
Test Object
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ELECTRICAL DEPARTMENT
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Procedure: 1. Connect the Testing Kit to power supply. 2. Connect the Rewirable fuse element to be tested to output terminals of A.C. source. 3. Make the connection to determine terminal co-efficient of A.C. current source capacity. 4. Make sure that source input switches are ‘OFF’. 5. Make sure that variac on zero position. 6. Switch ‘ON’ the main switch, this gives supply to logic control circuit. The digital meter displays are ‘ON’ showing zero reading. 7. Short the external interlock terminals, if it is not used in the test set up then terminals should be shorted through the potential free NC contact of device under test. 8. Start the kit by pushing ‘PUSH’ button (Pb). The Pb is ‘ON’ which energizes the input contactor coil ‘C’ when contactor is ‘ON’. 9. Now switch ‘ON’ A.C. current source control switch which gives supply to variac and to indicating lamp. 10. Increase A.C. current source output current to desirable value with the help of variac. 11. The timer selector switch is kept on the internal position for using the timer. 12. Adjust the source output to desired values, stop the kit power contactor by stop Pb2. Reset the timer with reset Pb keep variac to set value. 13. start kit power contactor with start Pb, this will also start the timer, when device trips, the kit power contactor is de-energized and timer stops, showing required time period on display. 14. Repeat the same procedure for 15A and 5A element and also note down the fusing elements current i.e. fusing current and fusing time and then calculate fusing factor both.
Fusing Factor: Fusing factor is the ratio of minimum fusing current to the rated current of fuse element.
Observation Table Sr. No. 1 2 3
:
Rated Ampere (A)
Trip Ampere (A)
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Calculations
Results
ELECTRICAL DEPARTMENT
: The Fusing Factor = Trip Ampere / Rated Ampere
:
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