Are these Switchgear and Protection handwritten notes free?

Yes. Fill in the short form on this page and the PDF downloads right away. There is no fee for the notes.

Are these official university notes?

No. These are original Uncodemy revision notes for Switchgear and Protection. They are not issued or approved by AKTU or any other university, and they are not past papers.

Which syllabus do they follow?

They follow the common B.Tech syllabus for Switchgear and Protection used by most Indian universities, including AKTU and colleges on the AICTE model curriculum. Unit order and depth differ, so match the notes with your own university syllabus.

Do the notes include relay numericals?

Yes. There is a worked IDMT relay example covering relay current, plug setting multiplier and operating time.

Should I study power systems first?

Yes. Fault calculations and symmetrical components from Power Systems are used throughout this subject, so revise those notes first if needed.

Switchgear and Protection Handwritten Notes PDF

Key takeaways

Eight units, from protection basics to lightning arresters and the Peterson coil.
Restriking voltage and RRRV are worked through with a solved example.
IDMT relay time is solved step by step from CT ratio, plug setting and TMS.
Distance and differential relays, Buchholz relay, alternator and transformer protection are covered.
Original Uncodemy revision notes, not official university notes. Check your own syllabus.

About these handwritten notes

These Switchgear and Protection notes are original Uncodemy revision notes, written in a clean handwritten style so they are quick to read before an exam. They follow the common B.Tech syllabus for Switchgear and Protection (B.Tech EE and EEE, and GATE EE basics). They are not official university notes and not copied from any textbook or past paper.

Topic order, unit numbers and depth vary between universities, so first place each unit below against your own university syllabus. If your syllabus has a topic that is missing here, add it in the margin from your class notes or textbook. Use these notes for revision after you have studied the topic once in class, not as your only study material. They are short on purpose: the aim is to help you recall the main ideas, formulas and diagrams quickly, so that your exam time goes into writing good answers.

What's inside the Switchgear and Protection notes

The notes go from the devices that interrupt current to the relays that decide when to trip, and then to protection of each part of the system. Each unit has a sketch, formula boxes and an exam tip.

Unit 1: Introduction. Types of faults, zones of protection and the requirements of a protective system.
Unit 2: Fuses, Isolators and MCB. Fuse types and characteristics, isolators, MCBs and their uses.
Unit 3: Arc Phenomena and Circuit Breaker Theory. Arc formation, arc extinction methods, restriking and recovery voltage, RRRV and current chopping.
Unit 4: Types and Ratings of Circuit Breakers. Air blast, oil, SF6 and vacuum breakers, and breaking, making and short-time ratings.
Unit 5: Protective Relays. Overcurrent and IDMT relays, distance relays (impedance, reactance, mho) and differential relays.
Unit 6: Protection of Generators and Transformers. Alternator protection schemes, transformer differential protection, magnetising inrush and the Buchholz relay.
Unit 7: Protection of Lines and Busbars. Distance and pilot protection of lines and busbar protection schemes.
Unit 8: Overvoltage Protection and Neutral Earthing. Causes of overvoltage, lightning arresters, insulation coordination, neutral earthing and the Peterson coil.

The last page of the PDF lists the most asked practice questions for the whole subject, so you can test yourself after finishing all the units.

Formulas and solved examples in the PDF

Formula boxes cover the natural frequency of restriking voltage, peak restriking voltage and RRRV, the making current factor, PSM and the IDMT operating time, and the Peterson coil inductance L = 1/(3ω²C). Solved examples include RRRV for a 100 kV system, an IDMT relay with a 400/5 A CT and TMS 0.2, and the arc suppression coil for 1 μF per phase.

How to revise Switchgear and Protection with handwritten notes

Handwritten-style notes work best when you read actively. Keep a pen and a rough notebook beside you, cover the formula or diagram, and try to write it yourself before you look.

Solve the IDMT relay steps in the same order each time: relay current, plug setting current, PSM, then time.
Draw the R-X diagram for impedance, reactance and mho relays on one page and note where each one is used.
Make one comparison table for SF6 and vacuum circuit breakers and one for the main relay types.
Sketch the Buchholz relay and the transformer differential scheme from memory. Both are common diagram questions.

In the last week, read only the formula boxes and exam tips, and solve one numerical or long question per unit from memory. If you study with friends, ask each other to explain one diagram or derivation aloud. Explaining a topic is the fastest way to find the gaps in it.

A short revision plan

If your exam is about a week away, this plan covers every unit in the PDF once and leaves time for practice. Stretch it over two weeks if you are starting from scratch.

Day 1: Introduction, Fuses, Isolators and MCB.
Day 2: Arc Phenomena and Circuit Breaker Theory, Types and Ratings of Circuit Breakers.
Day 3: Protective Relays, Protection of Generators and Transformers.
Day 4: Protection of Lines and Busbars, Overvoltage Protection and Neutral Earthing.
Day 5: Solve the practice questions in the exam focus section below, one per unit, without the notes.
Day 6: Read only the formula boxes and exam tips, redo the numericals you got wrong, and sleep early.

Common mistakes to avoid

Using the primary fault current directly in the PSM. Convert it to relay current with the CT ratio first.
Taking making current as equal to breaking current. Making current is about 2.55 times the symmetrical breaking current.
Saying the Buchholz relay detects external faults. It works only for internal faults below the oil level.
Forgetting the factor of 3 in the Peterson coil formula.

How Switchgear and Protection links to other subjects

Switchgear and Protection builds on Power Systems (faults and symmetrical components) and Electrical Machines. It links to power system operation, substation design and work in utilities and protection engineering.

Exam focus: high-weightage topics

University papers usually give the most weight to arc interruption and RRRV, circuit breaker types and ratings, IDMT and distance relays, transformer differential protection and overvoltage protection. GATE EE protection questions are mostly RRRV, IDMT relay time, PSM, distance relay characteristics, making current factor and the Peterson coil.

Typical long and numerical questions to practise:

Explain arc interruption theories and define restriking voltage, recovery voltage and RRRV.
Derive the expression for restriking voltage and RRRV, and explain current chopping.
Compare SF6 and vacuum circuit breakers, and define breaking, making and short-time ratings.
Find the operating time of an IDMT relay for a given CT ratio, PSM and TMS.
Compare impedance, reactance and mho distance relays and explain zones of protection.
Explain transformer differential protection and the problem of magnetising inrush.

When you write a long answer, start with a one-line definition, draw the diagram or circuit, write the derivation in clear steps and end with the final result and its unit. For numericals, write the formula first, then substitute, so you can still earn step marks if the arithmetic slips.

These are practice questions based on common syllabus topics. They are not verified past papers, and we do not claim any question will appear in your exam. For real previous papers, use your university's official archive.

Who these notes are for

These notes are for B.Tech EE and EEE students preparing for their Switchgear and Protection or Power System Protection semester exam, and for students revising GATE EE basics such as RRRV, IDMT relay time, PSM and the Peterson coil. They are also useful before interviews with power utilities, PSUs and substation equipment companies, where breakers and relays are standard topics.

Download Switchgear and Protection Handwritten Notes PDF