Mahakal Institute Of Technology Ujjain(mp) Seminar on circuit breakr Submitted to :Submitted by : Prof. sonali pandey pooja rathore

CIRCUIT BREAKER An electrical power system is very complex. For the safety of low voltage distribution ckt a fuse may be used but for heavier electrical equipments and majority of distribution and transmission network,circuit breaker is used for the protection against the fault.

#OPERATING PRINCIPAL:- # A circuit breaker essentially consist of fixed and moving contacts # When fault occurs on any part of the system, the contacts of ckt breaker are separated,the arc is struck between them. # Production of arc not only delay the current interruption but also generates heat which may cause damage to the system or ckt breaker itself. # The main problem in the circuit breaker is extinguish the arc within the shortest possible time so the heat generate by it may not reach a dangerous value. The tracking device, which consists of a GPS unit and a CDMA module, constantly sends out information about the vehicle's position, speed, distance travelled and duration of each halt. This information can then be accessed from a central location through a website or a mobile phone.

M any insulating fluids are used for arc extinction & fluid chosen de pend upon the rating and type of ckt breaker. The insulating fluids commonly used for circuit breaker 1) Air at atmospheric pressure 2) Compressed air 3) Oil which produce hydrogen for arc extinction 4) Ultra high vacuum 5) Sulphur hexafluoride [sf6]

Arc interruption:- # 2 methods 1. High resistance method: arc resistance is made to increase with time so that current reduce to a value insufficient to maintain the arc. THE RESISTANCE OF ARC INCREASED BY a) LENGTHENING THE ARC b) COOLING THE ARC c) SPLITTING THE ARC 2. Low resistance or current zero method: arc resistance kept low until the current is zero the de-ionization of the medium can be achieved by- a) LENGTHENING THE ARC b) COOLING c) blast effect 1. selection criteria.

# types of circuit breaker 1) Oil circuit breaker 2) Air blast circuit breaker 3) Sulphur hexafluoride [sf6] circuit breaker 4) Vacuum circuit breaker

Oil ckt breaker Oil ckt breaker #insulating oil [eg. Transformer oil] is used as an arc quenching medium. # The heat of arc evaporates the surrounding oil and dissociate it into a substantial volume of gaseous hydrogen. Classification:- ckt breaker a) Bulk oil ckt breaker ckt breaker b) Minimum oil ckt breaker

Bulk oil oil ckt breaker Plain break oil circuit breaker Disadvantages- 1)There is no special control over the arc other than the increase in Length by separating moving contact 2)Do not permit high speed interruption Arc control oil ckt breaker 1)Self blast ckt breaker oil 2)Forced blast

Minimum oil ckt breaker Only small percentage of oil is used. Constructin 1.Supporting chamber 2.circuit breaking chamber 3.top chamber #Advantages:- 1.Smaller space 2.Reduce risk of fire 3.Maintanance problems are reduce

Air blast ckt breaker These breaker employ a high pressure air blast as an arc quenching medium. The air blast cools the arc and sweeps away the arcing products to the atmosphere Types of Air blast ckt breaker 1.) Axial-blast type 2.)cross blast type

Sulphur hexafluoride [sf6] circuit breaker Sulphur hexafluoride [sf6] gas is used as the arc quenching medium. The sf6 is an electro negative gas and has a strong tendency to absorb free electron

VCB Vacuum is used as arc quenching medium. It has superior arc quenching properties than any other medium

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