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The steadily increasing demand of electric energy and the continuing liberalization process of the electricity market raise the utilities’ need to a further reduction in operation costs, increased functionality and power quality. One possibility to do so is by using a fast acting electronic circuit breaker. A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.

The outline of the project is to shut down the power supply when it is overloaded. Conventional circuit breaker is based on a thermal bimetal lever-trip mechanism, which is very slow and the trip time is dependant upon the percentage of overload. Here an electronic circuit breaker is designed which is based on the voltage drop across a series element typically a low-value resistor or a CT (current Transformer). The voltage sensed is compared against the preset voltage proportional to the current by a level comparator to generate an output for a relay or contactor to trip the load. The unit is extremely fast and overcomes the drawback of the thermal type. It uses an 8-bit microcontroller from 8051 family into which program is dumped for the operation.

The conventional circuit breakers such as MCBs take longer time to trip in order to activate trip mechanism at the shortest possible time. This project is implemented for fast tripping mechanism as against the slow one like MCB. During the functionality, the voltage is sensed and rectified to DC which is then compared with a preset voltage by a level comparator to generate an output that drives a relay through a MOSFET to trip the load. The unit is extremely fast and overcomes the drawback of the thermal type.

The power supply consists of a step-down transformer 230/12V, which steps down the voltage to 12V AC. This is converted to a DC using a Bridge rectifier. The ripples are removed using a capacitive filter, and it is then regulated to +5V using a voltage regulator 7805, which is required for the operation of the microcontroller and other components.

Furthermore, in future, the project can be enriched by using a CT for galvanic isolation between mains and control circuit. Power electronic devices such as thyristors / IGBTs can be used for ultra-fast operation compared to all the other methods.

Current Sensing.
Call/mail for Tech Support from 10 am - 7 pm IST.
Easy to use, Self-explanatory kit.
All-inclusive solution kit.
Extensive audio-visuals available.
Branding-free material.
Pre-programmed Microcontroller.
Hardware Requirements
  • 8051 series Microcontroller
  • Op-amp
  • Transformer
  • Diodes
  • Capacitors
  • Resistors
  • LED
  • Crystal
  • LCD
  • Voltage Regulator
  • Relay
  • Lamps
Software Requirements
  • Keil compiler
  • Languages: Embedded C or Assembly
Q & A
Q:  Which microcontroller is used in this project?
A:  A 40 pin microcontroller from 8051 family is used in this project.
Q:  What is the difference between Electronic circuit breaker and normal circuit breaker?
A:  Normal circuit breaker is dependent on thermal bimetal lever trip mechanism, whereas Electronic circuit breaker is formed using current sensing element and comparators
Q:  What is the role of microcontroller in this project?
A:  The microcontroller is programmed to display the circuit breaker conditions.
Q:  Will it auto return after fault (overload) clearance?
A:  No, one has to restart the device, as it would toggle between on and off till overload condition is cleared.
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