Fundamental of Switchgear & Potection - Technical Kranti

Fundamental of Switchgear.

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In this Blog, You can learn Fundamental of Switchgear.
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∆ Fundamentals of Power System  Protection:-

1.Switchgear:-  Such type of apparatus which is used for controlling and protecting the electrical circuit and equipment is called Switchgear.
Eg.:- Switch, fuse, Isolator, etc.

The essential feature of Switchgear:-

📍 Complete Reliability:-
The ability of the protection system is to operate under the predetermined condition is called Reliability.  So, Switchgear is added to the power system to improve the reliability of the power system.


📍Quick Operations:-
To minimize the damage to the faulty part the switchgear must operate as quickly as possible after the occurrence of a fault.

📍Provision for the instrument :-
For the metering purpose, there should be the provision for connecting instrument Transformer to the power system. So, the measuring instrument may be mounted on the main switchboard.

📍Provision for manual control:- 
A Switchgear must have provision for manual control.

➡Classification Of Switchgear:-

🔹Air Break Type Switch. 
🔹Oil Switch. 
🔹Isolators. 
🔹Relays. 
🔹Circuit Breakers. 
🔹HRC fuse & CT -PT. 
🔹Lighting Arrestor. 

1. Switches:- Such type of device which is used to open or close an electrical circuit is called Switch.
it can be used under full load or no load condition but it cannot block the fault current.
🔹Type of Switch:-
                    A.  Oil Switch.
                    B.  Air Switch.

2. Isolator:- Such type of mechanical switching device that operates at no-load condition is called isolator.
It is operated Manually.
🔹Type of Isolator:-
  A. Double Break isolator.
  B. Single Break isolator.
  C. Pantograph type isolator.

3. Circuit Breaker:- Such type of switching device which disconnects the circuit at on load condition is called a circuit breaker.
it is operated automatically.
it is an electronic device made by using MOSFET or BJT.

4. Realy: Such type of switching device which gives a signal to the circuit breaker as soon as the fault occurs in the power system is called Relay.
it cannot break the circuit at fault condition because it only senses the errors or fault in the power system.

5. Fuse:- A fuse is a short piece of thin strip wire which melts when excessive current flow through it for sufficient time.
➡it is inserted in series with the circuit to the protected.
➡Under the normal operating condition, the Fuse element it at a temperature below its melting point so it carries the normal Load current without overheating but when is short-circuited or overloads occurs then the current through fuse element increased beyond its rated capacity. So, the temperature is increased so the fuse is melted and protects the all equipment to a Short circuit.

🔴 Normal Conditions:--The electrical quantity like the voltage, current, phase angle, and frequency which remain constant under the working condition of the power system is called Normal condition.

🔴Abnormal Condition:-  The electrical quantity like the voltage, current, phase angle, and frequency which change due to the occurrence of fault under the working condition of a power system is called Abnormal condition. 

               ➡Faults➡

 An imperfection in the electrical circuit due to which current is deflected from the intended path is called a fault.

🔹Reason of Fault Occurrences:-
A. By Breaking of the conductor. 
B. failure of insulation. 
C. By lightening or switching surges. 

➡Types Of Electrical Faults:- ➡

1. Open circuit fault :-  The open-circuit fault mainly occurs because of the failure of one or two conductors.
The open-circuit fault takes place in series with the line. so, it is also called series faults.
 Such type of fault affected the reliability of the power system.
🔹Type of open-circuit fault:-
A. One conductor open fault. 
B. Two conductors open fault.
C. Three conductor open faults. 

2. Short Circuit fault:-  In this type of fault, the conductor of the different phase come into contact with each other with a power line, power transformer or any other circuit element due to which the large current flow in one or two-phase of the system.
When a  short circuit occurs a heavy current called short circuit current flows through the circuit.

➡ Causes of Short Circuits:- 

A. Internal Effect:-  
This effect occurs due to the aging of insulation, inadequate design or improper installations, etc.

B. External Effect:-  This effect is Occurs due to lighting Surge, overloading, heating, mechanical damage by the public.

➡ Type of short circuit faults:-
A.  Symmetrical fault. 
B.Unsymmetrical fault. 

A. Symmetrical fault:- The fault which involves all the three-phase gives rise to symmetrical fault current is called an asymmetrical fault.
.The symmetrical fault mainly occurs at the terminal of the generator.

➡ Type of Symmetrical fault:-
    🔹L-L-L- G fault. 
    🔹L-L-L fault. 


B.  Unsymmetrical faults:- 
Such type of faults which give rise to unsymmetrical current is called an unsymmetrical fault.

➡ Type of Unsymmetrical faults:-
🔹 L-G Faults. 
🔹L-L-L Faults. 
🔹L-L-G Faults. 

C. Simultaneous fault:-
When two or more fault occurs simultaneously on the power system is called multiple or simultaneous faults.
Eg:- L-G Faults

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