Protective Relays and Servicing Lab detail DTE Kar Diploma syllabus for Electrical And Electronics Engineering (EE), C15 scheme is extracted from DTE Karnataka official website and presented for diploma students. The course code (15EE56P), and for exam duration, Teaching Hr/week, Practical Hr/week, Total Marks, internal marks, theory marks, duration and credits do visit complete sem subjects post given below. The syllabus PDFs can be downloaded from official website.
For all other electrical 5th sem syllabus for diploma c15 scheme dte karnataka you can visit Electrical 5th Sem Syllabus for Diploma C15 Scheme DTE Karnataka Subjects. The detail syllabus for protective relays and servicing lab is as follows.
Pre-requisites:
Knowledge about – Elements of Electrical Engineering ,Electrical Circuits, Electrical Wiring , Electrical Appliances and Protective Devices.
Course Objectives:
To Develop Technical Skills in the students to :
- Identify, Select and Test various Relays and Protective Devices.
- Trouble shoot faults in Electrical Appliances and suggest suitable remedies.
Course Outcomes:
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PART A
PROTECTIVE DEVICES AND RELAYS
- SI symbols for most commonly used Electrical protective devices and their ANSI Codes. Identify different types of LV Fuses- Rewirable, Cartridge, HRC fuse, Switch Fuse Unit (SFU) and their applications. Note down the specifications. Identify different types of LV circuit breakers and their applications- MCB, MCCB, ELCB, RCCB and MPCB. Note down the specifications. Identify the class of MCB – B ,C, D and Z classes and their applications. 03
- Identify and study power contactors and auxiliary contactors. Note down the specifications. Identify and Study- Spike busters and Domestic range Electronic Voltage Stabilizer. Note down the specifications. 03
- Identify Time Multiplier Setting (TMS) and Plug Multiplier Setting (PMS) devices in Electro-mechanical relays. Note down the specifications of the Electro-mechanical Relay. Identify DIP switch settings and jumper settings in static relays (Microprocessor/microcontroller based relays) for setting Fault Voltage Level / Fault Current Level and Time Multiplier Settings as per supplier’s user manual. Note down the specifications of the Static Relay. Understand time setting and current setting procedure in Numerical relays / Digital relays. Note down the specifications of the Relay. Identify CBCT and its applications. Identify lockout relay. Understand the meaning of 1.3 Sec and 3 Sec relays. 03
CONDUCTING EXPERIMENTS 30 Hours
- Plot the operating characteristics of
- Fuse.
- MCB 03
- Test the operation of a digital or static type Earth leakage relay with CBCT (Adjust mA sensitivity and trip time using DIP switches). 06
- Plot the operating characteristics of ANY ONE of the following electromechanical IDMT relays.
- Over voltage relay
- Under voltage relay.
- Over current and
- Earth Fault Relay. 06
- Plot the operating characteristics of ANY ONE of the following: microprocessor / microcontroller based Over or Under voltage relay for Normal inverse time setting and Definite time setting. 06
- Program , Test and Plot the operating characteristics of ANY ONE of the following numerical / digital relays:
- Over Voltage and Under Voltage Relay.
- Over Current Relay. 06
- Conduct Break Down Voltage Test on transformer oil ( dielectric strength test. 03
PART B
TROUBLE SHOOTING AND SERVICING
- Trouble shoot and suggest suitable remedies for : Fluorescent lamp fitting, High pressure mercury vapour lamp and High pressure sodium vapour lamp sets. 06
- Dismantle, Identify the parts and assemble:- Electric iron box (non automatic and automatic) .Trouble shoot and suggest suitable remedies for the above. Note down name plate details. 03
- Dismantle, Identify the parts and assemble:- Table fan and Ceiling fan Trouble shoot and suggest suitable remedies for the above. Note down name plate details. 03
- Dismantle, Identify the parts and assemble :- food mixer Trouble shoot and suggest suitable remedies for the above. Note down name plate details. 03
- Dismantle, Identify the parts and assemble :- Electric Geyser and Electric Stove. Trouble shoot and suggest suitable remedies for the above. Note down name plate details. 03
- Dismantle, Identify the parts and assemble:- Induction heater. Note down name plate details. 03
- Dismantle, Identify the parts and assemble :- semi automatic washing machine Trouble shoot and suggest suitable remedies for the above. Note down name plate details. 03
- Install and test the UPS with Batteries. Trouble shoot and suggest suitable remedies. Note down name plate details. 03
- Panel wiring practice: – Wire up ANY ONE of the following as per standard practice.
- DOL or starter/star delta starter.
- Small control panel consisting of Isolator, MCB, voltmeter, Ammeter with CT, Indicators etc.
- Small Distribution panel wiring and cable crimping. 06
- Automatic water level controller (commercial type): – Identify the external connections, wire-up the level sensors and test the operation of electronic water level controller. Trouble shoot and suggest suitable remedies for the water level controller. 06
Reference Books:
For complete syllabus and results, class timetable and more pls download iStudy Syllabus App. Its a light weight, easy to use, no images, no pdfs platform to make students life easier.
e-Resource
- http://www.electrical4u.com/low-voltage-switchgear
- http://electrical-engineering-portal.com
- http://myelectrical.com
- http://www.nvistech.com/tutorials – Look for Electrical Portions.
Course Delivery:
The laboratory Course will be delivered through Tutorial, laboratory interaction, group discussion, practical exercises, instructions, assignments and viva voice.
Tutorial – 1Hr:
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Conduction/ Execution- 2 Hr:
Student group (2 to 3) will rig up the circuits and conduct the experiment individually under the supervision of the course co-ordinator.
Suggested Student Activities:
ANY ONE to be submitted with 3 pages report:
THE FOLLOWING EXERCISES OR SIMILAR EXERCISES MAY BE DISTRIBUTED AMONG THE STUDENT GROUPS (3 STUDENTS/GROUP).
CONDUCTABLE EXPERIMENTS
- Test the operation of an single phase ELCB.
- Test the given Thermal OLR (used in DOL starter).
- Test the given Phase failure relay/single phase preventer.
- Test the given domestic range electronic voltage stabilizer.
- Test the given MPCB (motor protection circuit breaker).
- Conduct Ratio test and Polaritytests on CT and PT.
- Conduct accuracy test on CT and PT
- Conduct Burden test on CT and PT
- Conduct Continuity test, Insulation resistance test and Secondary resistance test on CT and PT.
- Connect and test any one type of mini Motor Protection Relay.
- Design, construct and test an open coil stove of 1 KW to operate on 230V 50 Hz AC supply.
- Design and construct a small transformer ( 15 VA, 230 V/ 12 V).
OR
STUDY EXPERIMENTS
- Study any one control circuit drawing related to protective scheme and understand the significance of ANSI Codes.
- Study the construction and working principle of MCCB and MPCB (Motor Protection Circuit Breaker)
- Study the construction, working principle and applications of Core Balance Current Transformer (CBCT).
- Construction , operation and applications of lockout relay
- Study the construction and working principle of ACB and VCB used in industries.
- Study the Switch gear and protections in distribution transformer centre, HT and LT line/ feeders.
- Study the LV control panels of a Apartment/Hotel / Hospital/ factory / commercial buildings. Draw SLD of Power distribution and protections.
- Identify switch gear and protection schemes in substations.
- Method of conducting Ratio test and polarity test on CT and PT at project sites.
- Study the construction, working, installation and testing of a submersible pump.
Scheme of Valuation for SEE(Semester End Examination):
Note: The SEE Question paper should be set in such a way that Questions in the Question paper should have equal nos. of Questions from Part A and Part B.
- Circuit diagram and procedure. 15
- Conduction /Execution 20
- Results 05
- Viva-voce 10
List of Equipments:
PART A
Note: The experiments may be conducted either by using trainer kits or by using discrete components or by combinations of both depending upon the resources available in the respective institutions. Please refer the example lab manual for further details.
LIST OF DISCRETE COMPONENTS.
- Single phase Auto transformer , 0-270 Volts , 4 A. 06 Nos.
- Transformer – 240V/500V ( for voltage injection purpose) 04 Nos
- Transformer – 240V/24V, 20A (for current injection purpose) 04 Nos
- Rheostats 45ohms 8.5 A, 100 ohms 5 A, 300 ohms 2.5 A 02 Nos. each
- Ammeter 0-5/10 /20A MI type or Digital Ammeter- Single Ph 0-20A, suitable for 1A CT secondary. 05 Nos.
- Milli Ammeter 0-100 mA ( required for earth leakage experiment) 02 Nos.
- Voltmeter 0-300 V MI or Digital Voltmeter, Single Ph, 0-600V AC 06 N0s
- DPST and SPST knife switches or 2 pole, 3way, 6A selector switch 06 Nos. each
- 6 A ,220 V single pole MCB 06 nos.
- 6A ,220 V 30 mA single phase ELCB 02 Nos.
- 10 A or 16 A 415 V 30 mA or 100 mA ELR with 5 A/1A CBCT 02 sets.
- 10A or 16 A or 32 A , 415 V 3 phase power contactor-any model. 05 Nos. each
- 10 A , 415 V 3 phase auxiliary contactor – any model with2 NO + 2 NC. 05 Nos. each
- 500 VA single phase domestic Electronic voltage stabilizer 02 Nos.
- 125 A 415 V MCCB ( for study / identification experiment only) 01 No.
- 3 Phase 415 V MPCB (Motor Protection Circuit Breaker) of any low current rating ( for study / identification experiment only) 02 Nos.
- 3 Phase 415 V Thermal Over Load Relay 0-4.5 or 0-6 A or 0-10 A 04 Nos.
- Motor Protection Relay – any model suitable for 3 HP, 3 Ph Induction Motor. 02 nos.
- Digital multi-meter ( for general purpose) 02 Nos.
- Digital clamp on meter ( for general purpose) 02 nos.
- Digital Time Interval Meter 0-999 ms, 0-99.9 sec, 0-99.9 min ( *Digital stop watch may also be used as alternative) 05 Nos
- Single phase preventer (phase failure relay) 02 Nos.
- Different types of fuses (kit-kat fuse, cartridge fuse, glass fuse etc) (For identification experiment) 02 Nos each
- Lock out relay with 2 NO and 2 NC ( any low rating model). 02 Nos.
LIST OF TRAINER KITS
- Electro-mechanical Relay Trainer Kit or module with 4 mm banana pin sockets and patch cords. (TYPE – Over Load Relay or Over Voltage Relay or Under Voltage Relay or Earth Fault Relay – ANY ONE) 01 set
- Static Relay ( OLR or OVR or UVR or EFR – ANY ONE) Trainer Kit or module with 4 mm banana pin sockets and patch cords. 01 set
- Numerical relay or Digital relay (OLR or OVR or UVR or EFR -ANY ONE)-Trainer Kit or module with 4 mm banana pin sockets and patch cords. 01 set
- 15A AUX. Current source / current injection kit suitable for the above trainer kits with 4 mm banana pin sockets and patch cords. 03 Nos.
- 220 V AC /110 V DC AUX Voltage source / voltage injection kit suitable for the above trainer kits with 4 mm banana pin sockets and patch cords. 03 Nos.
- Fuse and MCB testing- trainer kit 02 Nos.
NOTE: The trainer kits may be of any one of the following types.
- Relay with current / voltage injection source-complete set as a single unit.
- Separate relay module and separate current / voltage injection source.
OR
*PLEASE REFER THE EXAMPLE MANUAL FOR BLOCK DIAGRAMS.
PART B
- 500 V Megger and multimeter ( tong tester) 04 Nos.Each
- Series Test lamp 06 Nos.
- Tool kit consisting of spanner set, screw driver, combination plier hammer/mallet etc, 04 set
- Fluorescent lamp fitting (electronic and non electronic) 10 Nos each
- High pressure mercury vapour lamp 04 sets
- High pressure sodium vapour lamp 04 sets
- Electric Iron ( non automatic and automatic) 04 Nos.Each
- Table fan 04 Nos.
- Ceiling fan 04 Nos.
- Geyser (small capacity) and immersion heater 02 Nos. Each
- Electric stove ( three heat ) 02 nos.
- Food mixer 04 Nos.
- Domestic Induction heater (1500 w ) 02 nos
- Semi automatic washing machine (small capacity) 02 Nos.
- Single phase induction motor ( CSCR and CSIR types) 02 Nos.Each
- Empty panel box with provision to fix various switch gears and accessories like Isolator, MCB, voltmeter, Ammeter with CT, Indicators etc( for DOL starter or main control panel or distribution panel) 04 Nos.
- Commercial Electronic Automatic water level controller 02 Nos.
- 2 KVA 220 V ,36 V or 48 V DC OFF line UPS with batteries 01 set
Note: Any other similar domestic appliances already available in the laboratory may also be used.
MODEL LAB MANUAL
STUDY EXPERIMENTS
SOME OF THE TYPES OF FUSES
FOLLOW THE PHOTOS FROM PDF.
If any current leaks from any electrical installation, there must-be any insulation failure in the electrical circuit, it must be properly detected and prevented otherwise there may be a high chance of electrical shock if-anyone touches the installation. An earth leakage circuit breaker does it efficiently. Means it detects the earth leakage current and makes the power supply off by opening the associated circuit breaker. There are two types of earth leakage circuit breaker, one is voltage ELCB and other is current ELCB.
Voltage Earth Leakage Circuit Breaker
The working principle of voltage ELCB is quite simple. One terminal of the relay coil is connected to the metal body of the equipment to be protected against earth leakage and other terminal is connected to the earth directly. If any insulation failure occurs or live phase wire touches the metal body, of the equipment, there must be a voltage difference appears across the terminal of the coil connected to the equipment body and earth.
This voltage difference produces a current to flow the relay coil.
If the voltage difference crosses, a predetermined limit, the current through the relay becomes sufficient to actuate the relay for tripping the associated circuit breaker to disconnect the power supply to the equipment. The typicality of this device is, it can detect and protect only that equipment or installation with which it is attached. It cannot detect any leakage of insulation in other installation of the system.
Current ELCB or RCCB or Residual Current Circuit Breaker
The working principle of current earth leakage circuit breaker or RCCB is also very simple as voltage operated ELCB but the theory is entirely different and residual current circuit breaker is more sensitive than ELCB. Actually, ELCBs are of two kinds, but it is general practice to refer voltage based ELCB as simple ELCB. And current based ELCB is referred as RCD or RCCB. Here one CT core is energized from both phase wise and neutral wire.
SINGLE PHASE RCCB OR CURRENT ELCB:
The polarity of the phase winding and neutral winding on the core is so chosen that, in normal condition mmf of one winding opposes that of another. As it is assumed that, in normal operating conditions the current goes through the phase wire will be returned via neutral wire if there’s no leakage in between. As both currents are same, the resultant mmf produced by these two currents is also zero-ideally. The relay coil is connected with another third winding wound on the CT core as secondary. The terminals of this winding are connected to a relay system. In normal operating condition there would not be any current circulating in the third winding as here is no flux in the core due to equal phase and neutral current. When any earth leakage occurs in the equipment, there may be part of phase current passes to the earth, through the leakage path instead of returning via mental wire. Hence the magnitude of the neutral current passing through the RCCB is not equal to phase current passing through it.
THREE PHASE RESIDUAL CURRENT CIRCUIT BREAKER OR CURRENT ELCB:
When this difference crosses a predetermined value, the current in the third secondary winding of the core becomes sufficiently high to actuate the electromagnetic relay attached to it.
This relay causes tripping of the associated circuit breaker to disconnect the power supply to the equipment under protection. Residual current circuit breaker is sometimes also referred as residual current device (RCD) when we consider the device by disassociating the circuit breaker attached to RCCB. That means, the entire parts of RCCB except circuit breaker are referred as RCD.
DIFFERENCE BETWEEN EARTH LEAKAGE RELAY AND ELCB:
According to IEC 60947-2, Annex B,earth fault current is the current flowing to earth due to insulation fault and Earth leakage current is the current flowing from the live parts of the installation to earth in the absence of an insulation fault. Earth Leakage Circuit breaker (ELCB or RCCB) has integral current breaking device. It detects as well as protects
the system by opening the protected circuit when the residual current exceeds the set value.
ELR is a relay that send a signal to the shunt coil of a circuit breaker (MCCB or ACB) whenever the leakage current exceeds the set level.
DIFFERENT BETWEEN MCB AND MCCB.
MCB
- These are thermal / thermo-magnetic devices
- Provides protection against over currents and short circuits.
- Available up to 100A and have a maximum short circuit capacity of 25kA.
- Commonly used in lighting circuits.
- Trip level cannot be varied.
MCCB
- May be Thermal/ Thermo-Magnetic/ Electronic trip type
- Primarily provide protection against over-current and short circuit.
- Can provide protection against Earth Fault, Residual Currents, Under voltage etc
- Available up to the rating of2500A.
- Trip level can be varied in adjustable trip type MCCBs.
- Remote ON/OFF is possible with additional accessories
- Commonly used is loads over 100A and motor protection circuits.
- Some MCCBs are microcontroller based.
- Available in single, two, three and four pole versions.
DIFFERENCE BETWEEN MPCB AND MCCB
- MPCBs are used to manually turn on and off electric motors and at the same time protect them from different types of faults occurring in motors MCCBs are used in power distribution and protect Low voltage distribution circuits as well as motor loads.
- MPCBs can protect motors against overload, short circuits, phase loss and under-voltage faults. MCCBs can protect motors against overload and short circuits. MCCBs can also provide under-voltages, earth faults and phase failure faults but these features are made available with additional accessories.
- MPCBs are specially designed for motor protection. MCCBs are used for general purpose circuit protection.
- Maximum load current can be set based on the full load current of motor. Overload, short circuit and trip delay time can be set based on the application.
- MPCBs are selected based on the full load current of motors and maximum possible short circuit current. MCCBs are selected based on the maximum load current and maximum short circuit current it must interrupt safely.
- MPCBs can withstand the starting currents without interrupting the circuit. When an MCCB is used as backup protection for a motor, it may interrupt the circuit if it is selected based on its full load current. So while selecting backup MCCB for motor it must be selected based on starting current of the motor.
- MPCBs have adjustable bimetallic strip for overload protection. This strip can be adjusted between two set values. Overcurrent value of MCCBs can be adjusted from 40% to 100% of its rated value.
- Overload relay is not required for motor circuits with MPCB backup. Overload relay is required.
- MPCBs can protect motor against overload and short circuit. MCCBs, when used in motor protection circuits can protect against short circuits only. Hence additional overload relay and contactor is required.
- Motor can be directly turned ON and OFF manually using a MPCB. Contactor is optional. Contactor is a must in these cases.
- Some MPCBs come with an auto resetting feature which allows motors to resume its operation after a short period from the occurrence of overload trip. This feature is not available in MCCBs
STANDARD SIZE OF MCB / MCCB / ELCB / SFU / FUSE
- MCB Up to 63 Amp (80Amp and 100 Amp as per Request)
- MCCB Up to 1600 Amp (2000 Amp as per Request)
- ACB Above 1000 Amp
- Sen. of ELCB 30mA (Domestic),100 mA (Industrial),300mA
- TPN Fuse Unit ( Rewire-able ) 16A,32A,63A,100A,200A
- Change over switch ( Off Load ) 32A,63A,100A,200A,300A,400A,630A,800A
- SFU ( Switch Fuse Unit ) 32A,63A,100A,125A,160A,200A,250A,315A,400A,630A
- HRC Fuse TPN ( Bakelite ) 125A,160A,200A,250A,400A, 630A
TESTING OF CT AND PT
Installation of protective relays at project sites has a number of possibilities for errors while implementation of the scheme due to incorrect connection of CT/PTs. The impact of such errors may result in unwanted tripping or failure to trip under fault conditions, leading to major equipment damage, disruption to supplies and potential hazards to personnel.
Commissioning tests at site are therefore invariably performed before protection equipment is set to work. The aims of commissioning tests are:
- To ensure that the equipment has not been damaged during transit or installation
- To ensure that the installation work has been carried out correctly
- To prove the correct functioning of the protection scheme as a whole
Instruments transformers (CT and PT) are devices through which current and voltage are sensed for operating the relays.
The following are some of the important tests conducted on CTs and PTs
Continuity test.
Ratio test
Polarity test
Insulation resistance test
Secondary resistance test
Accuracy test.
Burden test.
Burden test is to ensure that the connected burden to CT is within the rated burden as per the name plate details.
Inject the rated secondary current of the CT, from CT terminals towards load side by isolating the CT secondary with all connected load and observe the voltage drop across the injection points. The burden VA can be calculated as
Burden VA = Voltage drop x rated CT sec. Current.
Limits:
The calculated burden should be less than rated CT burden.
The ammeter connected to the secondary of the current transformer should be a robust moving coil, permanent magnet, centre-zero type. A low voltage battery is used, via a singlepole push-button switch, to energize the primary winding. On closing the push-button, the DC ammeter, A, should give a positive flick and on opening, a negative flick.
The voltage transformer polarity can be checked using the method for CT polarity tests. Care must be taken to connect the battery supply to the primary winding, with the polarity ammeter connected to the secondary winding.
ANSI CODE FOR SWITCH GEAR AND PROTECTION DEVICES.
- – Master Element
- – Time delay Starting or Closing Relay
- – Checking or Interlocking Relay
- – Master Contactor
- – Stopping
- – Starting Circuit Breaker
- – Rate of Change Relay
- – Control Power Disconnecting Device
- – Reversing Device
- – Unit Sequence Switch
- – Multi-function Device
- – Overspeed Device
- – Synchronous-speed Device
- – Underspeed Device
- – Speed – or Frequency, Matching Device
- – Data Communications Device
- – Shunting or Discharge Switch
- – Accelerating or Decelerating Device
- – Starting to Running Transition Contractor
- – Electrically Operated Valve
- – Distance Relay
- – Equalizer Circuit Breaker
- – Temperature Control Device
- – Volts Per Hertz Relay
- – Synchronizing or Synchronize-Check Device
- – Apparatus Thermal Device
- – Under voltage Relay
- – DC under voltage Relay
- – Flame detector
- – Isolating Contactor or Switch
- – Annunciator Relay
- – Separate Excitation
- – Directional Power Relay or Reverse Power Relay
- – Position Switch
- – Master Sequence Device
- – Brush-Operating or Slip-Ring Short-Circuiting Device
- – Polarity or Polarizing Voltage Devices
- – Undercurrent or Under power Relay
- – Bearing Protective Device
- – Mechanical Condition Monitor
- – Field (over/under excitation) Relay
- – Field Circuit Breaker
- – Running Circuit Breaker
- – Manual Transfer or Selector Device
- – Unit Sequence Starting Relay
- -DC over voltage Relay
- – Reverse-phase or Phase-Balance Current Relay
- – Phase-Sequence or Phase-Balance Voltage Relay
- – Incomplete Sequence Relay
- – Machine or Transformer, Thermal Relay-OLR
- – Instantaneous Over current Relay
- G – Instantaneous Earth Over Current Relay (Neutral CT Method) 50N – Instantaneous Earth Over Current Relay (Residual Method) 50BF – Breaker failure
- – AC Inverse Time Over current Relay
- G- AC Inverse Time Earth Over current Relay (Neutral CT Method)
- N- AC Inverse Time Earth Over current Relay (Residual Method)
- – AC Circuit Breaker
- a- AC Circuit Breaker Position (Contact Open when Breaker Open) 52b- AC Circuit Breaker Position (Contact Closed when Breaker Open)
- – Exciter or DC Generator Relay
- – Turning Gear Engaging Device
- – Power Factor Relay
- – Field Application Relay
- – Short-Circuiting or Grounding Device
- – Rectification Failure Relay
- – Overvoltage Relay
- – Voltage or Current Balance Relay
- – Density Switch or Sensor
- – Time-Delay Stopping or Opening Relay
- – Pressure Switch
- – Ground Detector Relay
- R – Restricted earth fault
- S – Stator earth fault
- – Governor
- – Notching or Jogging Device
- – AC Directional Over current Relay
- – Blocking Relay
- – Permissive Control Device
- – Rheostat
- – Liquid Level Switch
- – DC Circuit Breaker
- – Load-Resistor Contactor
- – Alarm Relay
- – Position Changing Mechanism
- – DC Over current Relay
- – Telemetering Device
- – Phase-Angle Measuring Relay or “Out-of-Step” Relay
- – AC Reclosing Relay (Auto Reclosing)
- – Flow Switch
- – Frequency Relay
- – DC Reclosing Relay
- – Automatic Selective Control or Transfer Relay
- – Operating Mechanism
- – Communications, Carrier or Pilot-Wire Relay
- – Lockout Relay/Master Trip
- – Differential Protective Relay
- – Auxiliary Motor or Motor Generator
- – Line Switch
- – Regulating Device
- – Voltage Directional Relay
- – Voltage and Power Directional Relay
- – Field Changing Contactor
- – Tripping or Trip-Free Relay( trip circuit supervision Relay)
- – For specific applications where other numbers are not suitable
- – Busbar Trip Lockout relay
- – For specific applications where other numbers are not suitable
- – For specific applications where other numbers are not suitable
- – For specific applications where other numbers are not suitable 150 – Earth Fault Indicator
- AFD – Arc Flash Detector
- CLK – Clock or Timing Source
- DDR – Dynamic Disturbance Recorder
- DFR – Digital Fault Recorder
- DME – Disturbance Monitor Equipment
- ENV – Environmental Data
- HIZ – High Impedance Fault Detector
- HMI – Human Machine Interface
- HST – Historian
- LGC – Scheme Logic
- MET – Substation Metering
- PDC – Phasor Data Concentrator
- PMU – Phasor Measurement Unit
- PQM – Power Quality Monitor
- RIO – Remote Input/output Device
- RTU – Remote Terminal Unit/Data Concentrator
- SER – Sequence of Events Recorder
- TCM – Trip Circuit Monitor
- LRSS – LOCAL/REMOTE SELECTOR SWITCH
- SOTF – Switch On To Fault
CONDUCTING EXPERIMENTS
NOTE:
- Relay based experiments may be done using trainer kits and other experiments may be done using discrete components.
- Proper protections like fuse and MCB should be used for all circuits as a safety precaution.
- All the experiments shall be done for low current and voltage ranges.
- The circuit diagrams given are for reference only. Alternate safe methods may be adopted.
EXPERIMENT NO.01
FUSE
AIM: TO STUDY THE OPERATION OF A FUSE AND PLOT THE TIME-CURRENT CHARACTERISTICS.
-Rationale / importance of this experiment: A fuse is a simplest, cheapest and most reliable protective device which provides protection against over current and short circuit. One or the other type of fuse is used in all the equipments/ power circuit wirings/meter boards/ metering panels/ service connections/LT lines/HT lines/Auto-electricals/control panels etc.It is the most fundamental element of any electrical circuit. A fuse is definitely present in all electrical circuits irrespective of other protective device like MCBs.
The study of fuse characteristics forms the base / foundation for interpreting the characteristics of protective relays. Because the reliability of any protection scheme depends on the time taken by the relay to sense ,operate and open the circuit breaker . The more the delay, greater will be the damage due to fault current. Hence by plotting the time-current characteristics the students will be able practically understand the importance of time (quick operation) when the magnitude of fault current is high.
After doing this experiment, the students will be able to interpret the characteristic of fuse, identify the different types of fuses and fuse elements.
APPARATUS REQUIRED
- Fuse wire (preferably lower rating like 1 A ,2 A ,2.5Aand 5 A).
- Ammeter 0-5/10A MI
- SPST Knife switch
- 5A,230V single phase variable lamp/resistive load.
- Stop clock / digital watch.
- Rheostat (38 Ohm, 8.5 A) may be used in series with ammeter for adjusting the current.
- Single phase 0-300 V,10 A Auto transformer.
- Single phase 220 V / 24V 20 A, transformer ( for current injection)
( Items 7 and 8 are used in alternate circuit in which current can be injected without actual load)
CIRCUIT DIAGRAM ( see alternate circuit also)
PROCEDURE :
- Connections are made as per the circuit diagram.
- Switch ON the main supply by keeping the Auto-transformer in zero position and SPST switch in open position.
- Close the SPST switch and adjust the autotransformer and the load until the ammeter reads 1.25 times the rated current of the fuse.
- Now open the SPST switch and observe the fuse to melt.
- Replace the fuse wire and repeat the above procedure for 2, 3, 4 times the rated current of the fuses.
- In each step note down the time taken by the fuse to melt (from the instant the SPST switch is opened till the fuse melts and ammeter reads zero).
- Plot the time- current characteristics.
Viva Questions
- Characteristics of fuse wire.
- Comparisons of fuse and circuit breaker
- Types of fuses and their applications
- Type of fuse required for protection of transformer, generator and induction motor
ALTERNATE CIRCUIT ARRANGEMENT FOR TESTING FUSE / MCB.
EXPERIMENT NO 2
AIM : STUDY THE OPERATION OF MCB AND PLOT THE OPERATING CHARACTERISTICS
MCB has two characteristics.
- Inverse time characteristics during over load.
- Instantaneous characteristics during short circuit.
[MCB TYPE TRIPPING CURRENT]
- TRIP CURVE CLASS B Above 3 to 5 times rated current. Suitable for cable protection
- TRIP CURVE CLASS C Above 5 to 10 times the rated current. Suitable Domestic and residential applications and electromagnetic starting loads with medium starting currents
- TRIP CURVE CLASS D Above 10(excluding 10) to 20 times the rated current. Suitable for inductive and motor loads with high starting currents.
- TRIP CURVE CLASS K Above 8 to 12 times the rated current. Suitable for inductive and motor loads with high inrush currents.
- TRIP CURVE CLASS Z Above 2 to 3 times the rated current. These type of MCBs are highly sensitive to short circuit and are used for protection of highly sensitive devices such as semiconductor devices
APPARATUS REQUIRED:
- Single Pole MCB (preferably lower rating like 6 A)
- Ammeter 0-10A MI
- 5 A SPST switch.
- Single phase Auto-transformer (dimmer-stat) 0-300 V 10A
- Resistive load,10 A single phase.
- Stop clock / digital watch.
CIRCUIT DIAGRAM: (see alternate circuit also)
PROCEDURE :
- Connections are made as per the circuit diagram.
- Switch ON the main supply by keeping the Auto-transformer in zero position and SPST switch in open position.
- Close the SPST switch and adjust the autotransformer and the load until the ammeter reads 1.5 times the rated current of the MCB.
- Now open the SPST switch and observe the MCB to Trip.
- Repeat the above procedure for 2 and 3 times the rated current of the MCB.
- In each step note down the time taken by the MCB to Trip (from the instant the SPST switch is opened till the MCB Trips)
- Plot the time-current characteristics.
Viva questions:
- What is an MCB.
- Different Classes of MCB.
- Which class of MCB is choosen for motor protection.
- What is meant by instantaneous characteristics and inverse time characteristics of MCB.
ALTERNATE CIRCUIT ARRANGEMENT FOR TESTING FUSE / MCB.
EXPERIMENT NO 3
AIM : TO TEST THE OPERATION OF SINGLE PHASE ELCB / RCCB
APPARATUS REQUIRED:
- 10 A /16 A ,30 mA / 60mA sensitivity single phase ELCB.
- 5 A socket with Earth pin connected to the earthing.
- 0-100 mA Ammeter.
- 1 A 250 V ,4k POT
- 100 W incandescent bulb.
CIRCUIT DIAGRAM
PROCEDURE:
- Connections are made as per the circuit diagram.
- Switch ON the main supply and ELCB.
- Switch ON SPST .
- Vary the POT and note down the current at which the ELCB trips.
- Verify the whether the ELCB tripped as per current sensitivity specification.
EXPERIMENT NO 4
AIM : TO TEST THE OPERATION OF A EARTH FAULT/ EARTH LEAKAGE RELAY
APPARATUS REQUIRED:
- Power contactor with 230 V coil voltage.
- Earth Leakage Relay with suitable CBCT set.
- Push button switches
- SPST
- Lamps
CIRCUIT DIAGRAM
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 ) being protected against earth fault.
The pick up current and trip 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:
- Connections are made as per the circuit diagram.
- Switch ON the main supply switch with SPST switch in open condition.
- Press the ON push button switch so that the lamp is ON.
- Now close SPST switch and observe the Earth Leakage Relay which will trip the contactor (Circuit Breaker)
- Note down and Verify the tripping time and current as per DIP settings. (The secondary current of CBCT may be measured using a ammeter in the CT circuit or using a clamp-on meter)
TRIANER KITS BASED EXPERIMENTS
EXAMPLE WIRING FOR TESTING – OVER / UNDER VOLTAGE RELAY USING
Relay testing may be done using discrete components / devices or by using trainer kits.
Keeping the cost of relays in mind and multiple handling /usage of the components, it is preferred to conduct relay testing experiments using trainer kits. The above diagram shows two kits namely voltage injection kit and the other one is the relay under test. (similarly, for testing over current relay current injection kit will be used). The wirings are made using patch cords as shown in the diagram.
The concept of wiring is same for testing other relays like over current relay, earth fault relay.
The voltage injection kit has the following features:
- DC, 110 V Aux power supply for relay.
- Variable Voltage Source to test the operation of the relay ( over voltage or under voltage).
- Digital timer for measuring the time taken by the relay to operate when the voltage exceeds the set value.
CONDUCTION OF THE EXPERIMENT
Initially the plug setting and the time setting will be made on the relay.( In case of static relays, DIP switches will be adjusted as per requirement and in case of digital / numerical relays , programming will be done by using touch pads / buttons / keys on the numerical relay)
Selector switches are provided for set and test positions on the voltage injection kit.
First the selector switch will be put onset position and the voltage source will be varied until the relay operates. After setting the voltage at which relay operates, the position of variable voltage will be kept constant (i.e, it will be not be disturbed) and the relay and the timer will be reset. Now the selector switch will be put on test position and the time taken by the relay to operate is noted. The experiment is repeated for different voltages, plug setting and time settings.
The above procedure is common for all trainer kit based relay experiments.
NOTE: The trainer kits may of separate voltage / current injection kit and separate relay kits as shown above OR combine kits as shown below.
ACTIVITY EXPERIMENTS
EXPERIMENT NO. 5
AIM: TO STUDY THE OPERATION OF DOMESTIC VOLTAGE STABILZER AND TEST IT.
-RATIONALE: Voltage stabilizer is the most common protective device used in every house hold for protection of expensive gadgets like LED TV , Fridge, Air conditioner etc., against over voltage.
By doing this experiment the student will learn to test the operating voltage range of the stabilizer specified the manufacturer.
APPARATUS.
- Single phase Voltage stabilizer 500 VA .
- Voltmeter 0-300V MI
- 10A 0-30 V Single phase Auto-transformer (dimmer-stat)
CIRCUIT DIAGRAM
PROCEDURE:
- Connections are made as shown in the circuit diagram.
- Keep the power ON switch of the stabilizer in OFF condition.
- Switch On the main supply and set the voltmeter Vin to normal operating voltage (220 V)
- Switch on the stabilizer and note the output voltage Vout.
- Now slowly increase the voltage by varying the autotransformer and observe both Vin and Vout until the stabilizer trips. Note down the over voltage Vin at trip.
- Repeat the above procedure for under voltage trip by decreasing the input voltage.
EXPERIMENT NO.6
AIM: TO TEST THE OPERATION OF THERMAL OVER LOAD RELAY AND PLOT THE TIME – CURRENT CHARACTERISTICS.
APPARATUS REQUIRED
- Themal over load relay0-10 A ,415 V
- Ammeter 0-10A MI
- 15 A SP switch
- 10A 0-300 V Single phase Auto-transformer (dimmer-stat)
- 220V/12V ,20 A Single phase transformer( CURRENT INJECTION).
- Stop clock / digital watch.
CIRCUIT DIAGRAM
PROCEDURE:
- Connections are made as per the circuit diagram.
- Adjust the current rating on OLR (using pointer or knob in the frontside).
- Switch ON the main supply by keeping SPST in closed position.
- Switch ON and the vary the autotransformer and set the ammeter current to the desired test current ( say 1.5 or 2 times the rated current of the OLR)
- Now open the SPST and observe the OLR to trip.
- Note down the time for tripping.
- Reset the OLR and wait for 10 minutes for the OLR to cool down.
- Repeat the above experiment for 2.5, 3 , 4 times the rated current of OLR).
- The operation of NO and NC of OLR while tripping may be checked with the help of series test lamp as shown in the circuit diagram.
- Plot the time-current characteristics.
EXPERIMENT NO. 7
AIM: TO CONDUCT BURDEN TEST ON CT AND DETERMINE ITSVA RATING.
APPARATUS REQUIRED:
- CT on which burden test has to be conducted.
- Ammeter 0-5A MI
- Voltmeter 0-300 V MI
- Auto-transformer 0-300 V , 10 A
- Current injection transformer- 220/12 V, 20 A
CIRCUIT DIAGRAM
PROCEDURE:
- Connections are made as per the diagram.
- Switch ON the main supply and slowly vary the autotransformer till rated current passes through secondary of the CT.
- Note down the voltage drop across the secondary of the CT.
- Calculate the VA burden = Voltmeter reading x Ammeter reading.
SOME USEFUL TIPS / INFORMATION
Evolution of Relays:
Mechanical relays developed in the 1800s were the first form of electrical protection. While still being reliable and widely used these were superseded by static relays in the early 1980s. Static relays have no moving parts (hence the name) and operated onthe basis of analogue circuitry. More recently static relays have been superseded by first digital relays and now numerical microprocessor based devices.
Tripping Curves
IEC 60255 Characteristics
The IEC 60255 standard defines four standard current time characteristics -standard inverse (SI), very inverse (VI), extremely inverse (EI) and long-time inverse. Each characteristic can be calculated from:
where:
t = tripping time in (‘S’)
I = fault (actual) secondary CT current (‘A’)
Is = relay pick-up current setting)
TMS = time multiplier setting
[Characteristic a K]
Standard Inverse 0.02 0.14
Very Inverse 1.0 13.5
Extremely Inverse 2.0 80
Long-time 1.0 120
Inverse
Relay characteristics are sometimes classified according to the tripping time at 10 times the setting current (i.e. [3s/10] – a standard inverse curve which will trip in 3 seconds at 10 times the current setting). Tripping times for the various relays are:
Standard Inverse (SI. [3s/10] or [1.3s/10]
Very Inverse (VI. [1.5s/10]
Extremely Inverse (EI. [0.8s/10]
Long Time Standard Earth Fault [13.3s/10]
North American Characteristics
Current time characteristics in North America as classified as IEEE Moderately Inverse, IEEE Very Inverse, IEEE Extremely Inverse, US C08 Inverse and US CO2 Short Time Inverse. These are given by:
where:
t = tripping time in (‘S’)
I = fault (actual) secondary CT current (‘A’)
Is = relay pick-up current setting
TD = time dial setting (multiplier)
Characteristic a p K
IEEE Moderately Inverse 0.02 0.114 0.0515
IEEE Very Inverse 2.0 0.491 19.61
IEEE Extremely Inverse 2.0 0.1217 28.2
US CO8 Inverse 2.0 0.18 5.95
US CO2 Short 0.02 0.01694 0.02394
Time Inverse
Setting Example (IEC 60255)
An 1000 Amp breaker protected by relay with Standard Inverse characteristic. The relay pick-up current value is set at 0.8, time multiplier setting is 7 and the fault current is 8000 A. What will be the tripping time?
- – from the table a = 0.02, K = 0.14
- – pick-up current setting = 1000 A x 0.8 = 800 A
- – using the IEC 60255 equations, the tripping time is:
If you have the 3sec relay’s trip curve, you can just multiply the time with 1.3 and divide the answer with 3 . That is the time for the 1.3sec relay.
GEC / English Electric / Alstom /Areva
Labelingthe model from left to right, using number CDG31 etc. 1=C, 2=D c=G etc.:
- operating quantity (C – current, D – differential, V- voltage)
- basic movement (D – induction disc, M – balanced armature, T – static)
- Application (G- general or generator, E – earth, U – definite time, F – flag, M – motor, D – directional)
- number of units (ie CDG3x is a 3 element / unit CDG relay)
- characteristic (for CDG, 1= std inverse (3s), 2= long time delay, 3=very inverse (1.55s), 4=extremely inverse (0.6s), 6=Long Time Standard Earth Fault)
- case size (15 different cases, A=size 1 draw out, 10 terminal etc)
- case mounting (F=flush etc)
- identification (identifies rating, contact arrangement etc. 2= ‘metricated’)
- suffix (‘5’ is for 50Hz only relays, ‘6’ for 60Hz)
Example – CDG 34EG0022A5 is a current operated, induction disc general relay, with three extremely inverse elements and is a 50 Hz unit.
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