Course Code : EEPE202

Course Title : SWITCHGEAR AND PROTECTION

Semester Four
Number of Credits : 3 (L: 3, P: 0)
Prerequisites : NIL
Course Category : PE
Full Marks 100 [ Internal :40 Marks+ External: 60 Marks]

Course Objective
The aim of this course is to help the student to attain the following industry identified competency through various
teaching learning experiences:
• Maintain switchgear and protection schemes used in electrical power systems.

Contents (Theory): Hrs./Unit

Unit : 1 Fundamental: 5
1.1Necessity & functions of protective system.
1.2 Normal & abnormal conditions.
1.3 Types of faults & their causes.
1.4 Symmetrical and Asymmetrical fault- concept of positive, negative and zero sequence.
1.5.1 Use of current limiting reactors & their arrangements.
1.5.2 Short circuit fault calculations in lines fed by generators through transformers
1.5.3 Short- circuit KVA calculations for symmetrical faults – Numerical problems.
Unit : 2 Circuit interrupting devices: 12
2.1 Basic fuse terminology: fuse element, rated current, fusing current, fusing factor,
prospective current, cut-off current, arcing time, rupturing capacity, total operating time.
Fuse Characteristics
2.1.1 HRC fuses – construction, types, working, characteristics, selection and applications
2.2 Isolators- vertical break, horizontal break & pantograph type
2.3 Arc formation process, methods of arc extinction (High resistance and Low resistance),
Arc voltage, Recovery voltage, Re-striking voltage, RRRV.
2.4 Circuit breakers- Concept, Classification, Working principle, Construction, Specification
& Applications of
2.4.1 E.H.V/H.V – Minimum oil circuit breakers (M.O.C.B.), Air Blast Circuit Breaker
(A.B.C.B),Sulphur Hexafluoride circuit breaker (SF6). Vacuum circuit breaker.
2.4.2 L.V.- Air circuit breakers (ACB), miniature circuit breakers (M C B), Moulded case
circuit breakers (M C C B) , Earth leakage circuit breaker ( E L C B or R C CB ), Comparison
of fuse & MCCB
2.5 Selection of MCCB for motor.
2.6 Selection and rating of HT and LT circuit breakers – breaking capacity, making
capacity, rated operating duty, rated voltage.
2.7 Elementary idea of Auto-reclosing.
2.8 Concept of Gas insulated switchgear.
Unit: 3 Protective Relaying: 12
3.1 Fundamental quality requirements: Selectivity, Speed, Sensitivity, Reliability,
Simplicity, Economy.
3.2 CT & PT used in protection: rating of CT and PT; Accuracy Class of CT and their
significance, PT; Requirements, Basic circuit diagram, working principle & application of
 CVT and CCVT.
3.3 Zones of protection, primary & back-up protection.
3.4 Operating principles and construction (in brief) of: Electromagnetic relays (Attracted
armature type, Solenoid type, Watt-hour meter type) , thermal relays,
3.5 Block diagram and working of static relays and Microprocessor based relays
3.6 Over current relay--- Time-current characteristics of definite time, instantaneous,
inverse time and IDMT Relays. Use of very inverse-type O/C relay and extremely
inverse type O/C relay.
Time-setting, current-setting, PSM – Numerical problems.
3.7 Directional Relay - Construction, Characteristics: Constant product characteristics,
Polar characteristics, Concept of dead zone, 300, 600 and 900connection.
3.8 Distance Protection Relay: Area of applications, Impedance relays, Reactance relay,
MHO relay: operating characteristics, effect of arc resistance on their characteristics.
3.9 Differential Relay: Introduction, Current differential protection for an internal fault –
fed from single & both ends.
Voltage balance differential protection – Schematic diagram & operation (in brief).
Mention the position of operating coil and the restraining coil for both the
cases.

Unit: 4 Equipment Protection: 10

4.1 Protection of Alternators – Types of faults; Percentage differential stator protection,
brief idea of: - rotor protection due to loss of excitation, protection against rotor
overheating because of unbalance in load, overspeed protection, protection against
motoring and field suppression.
4.2 Transformer protection – Types of faults; Percentage biased differential protection –
numerical problems, Buchholz Relay: Construction, Operation, merit and demerits, rate of
rise of pressure relay, WTI and OTI; over-fluxing protection, O/C protection, Earth fault
protection and restricted earth fault protection scheme.
4.3 Protection of Motor: Abnormalities & faults. Short circuit protection, Overload
protection, Single phase preventer.
4.4 Protection of Busbar & transmission line
4.4.1 Bus bar protection: Differential and Fault bus protection.
4.4.2 Transmission line protection: Over current protection (Time graded, current graded),
Distance and Pilot wire protection.

Unit: 5 Over voltage Protection: 6

5.1 Causes of over voltages.
5.2 Lighting phenomena & over voltage due to lightning.
5.3 Protection of transmission line & substation from direct stroke.
5.4 Types of lightning arresters & surge absorbers & their Construction & principle of
operation.
5.5 Protection against traveling waves.
5.6 Insulation co-ordination.

Total 45

References:

1. Mehta V K; Rohit Mehta, Principles of Power System – S. Chand & Company Ltd., New Delhi.ISBN-13- 978-
8121924962; ISBN:10- 9788121924962
2. Rao. Sunil S., Switchgear and Protection, Khanna Publishers, New Delhi, ISBN: 978-81-7409- 232-3.
 3. Singh, R. P., Switchgear and Power System Protection, PHI Learning, New Delhi, ISBN: 978-81-203-3660-5.
4. Gupta. J. B. Switchgear and Protection, S. K. Kataria and Sons, New Delhi, ISBN: 978-93-5014- 372-8.
5. Bhavesh R. Bhalja, R. P. Maheshwari,Nilesh G Chothani ; Protection and Switchgear (Second edition) Oxford
University Press; New Delhi; ISBN: 13: 978-0-19-947067-9
6. C L Wadhwa; Electrical Power System (Seventh Edition); New Age International Publishers; New Delhi; ISBN: 978-
93-86070-19-7
7. Ram, Badri; Vishwakarma D. N., Power System Protection and Switchgear, McGraw-Hill, New Delhi. ISBN :
9780071077743
8. Ingole Arun; Switchgear and Protection; Pearson

Course Outcomes

The theory and relevant soft skills associated with this course are to be taught and implemented, so that the
student demonstrates the following industry oriented COs associated with the above mentioned competency:

1. Identify various types of faults in power system and apply the knowledge to calculate the fault current.
2. Understand the construction and working of various types of current interrupting devices and apply suitably for
different applications.
3. Understand construction and working of various types of protective relays and their applications.
4. Know about the protection systems of alternators, transformers. Busbars, Motors.
5. Understand different protection schemes for power system against over voltages.

Internal Assessment (40 Marks)

Mid Semester Class Test:20 Marks Quizzes, viva-voce, Assignment: 10 Marks Attendance: 10

External Assessment (End Semester Examination:60 Marks)

GROUP UNIT
A 1,2
B 3
C 4,5
Course Code : EEPE204
Course Title : SWITCHGEAR AND PROTECTION LABORATORY
Number of Credits : 1 (L: 0, T: 0, P: 2)
Prerequisites : NIL
Course Category : PE

Course objectives:
The aim of this course is to help the student to attain the following industry identified
competency through various teaching learning experiences:
• Maintain switchgear and protection schemes used in electrical power systems.

Course contents
List of Practical:(at least EIGHT are to be done)

1. Identify various components of different switchgears (through visit or video or model) viz
A. Circuit Breaker [: i) LT air circuit breaker; ii) Minimum Oil Circuit Breaker; iii) Air Blast Circuit Breaker; iv) SF6
Circuit Breaker; v) Vacuum Circuit Breaker]
B. Isolator [vertical break, horizontal break]
C. CTs and PTs
D. Power and distribution Transformers
and write their specifications
2. Test HRC fuse by performing the load test
3. Test MCB by performing the load test
4. Dismantle MCCB/ELCB/ RCCB and identify various parts
5. Testing of Induction type/ Microprocessor Based Over Current relay using Relay Testing Kit to plot
the inverse characteristics.
6. Testing of static distance protection relay using Relay Testing Kit.
7. Testing of static Overcurrent protection relay using Relay Testing Kit.
9. Testing of Directional Over Current Relay (DOCR) by Relay Testing Kit.
10. Testing of percentage Differential Protection of Transformer Using Transformer Differential Relay
(Electromagnetic/Microprocessor based/ static).
11. Simulate differential protection scheme for transformer with power system simulation kit.
12. Demonstrate the operation of single phasing preventer by creating single phasing fault for a given
3-ph induction motor with D.O.L. starter.
13. Simulate transmission line protection by using the impedance relay/over current relay for various
faults. (On transmission line protection simulation Kit).
14. Study of different lightning arrester and identify different parts.
15. Study of ACB/VCB and identify different parts.
 Course outcomes:
The practical experiences and relevant soft skills associated with this course are to be taught
and implemented, so that the student demonstrates the following industry-oriented COs
associated with the above-mentioned competency:
a) Select suitable switchgears for different applications.
b) Test the performance of different protective relays.
c) Maintain protection systems of alternators and transformers.
d) Apply the knowledge of different protection schemes through simulation.
e) Select suitable arrester against lightning.

E X A M I N A T I O N S C H E M E (SESSIONAL)
1. Continuous Internal Assessment of 60 marks is to be carried out by the teachers throughout
the fourth Semester. Distribution of marks: Continuous evaluation:50 Marks; Class
Attendance: 10 Marks
2. External Assessment (end Semester examination) of 40 marks shall be held at the end of the
fourth Semester on the entire syllabus. Assignment on the day of Viva-voce and practical
report submission:20; Viva-voce:20