ULTRA-FAST ACTING ELECTRONIC CIRCUIT BREAKER

ULTRA-FAST ACTING ELECTRONIC CIRCUIT BREAKER

ABSTRACT

The steadily increasing population has more demand and consumption of electric energy in the market as raised and that of equipment’s used like electrical and electronics are also costlier. So to protect the electrical system from overload or short circuit here is one possibility, which is by ultrafast acting electronic circuit breaker. A circuit breaker is automatic operated switch designed to shut down the power supply when overloaded. The tripping depends on the current passing through the CT’s which is connected in series with load. It uses the PIC- microcontroller into which program is dumped for the operation. The unit is extremely fast and over comes the drawback of thermal type circuit breaker like MCB based on a thermal bimetal lever-trip mechanism which is very slow. Here an electronic circuit breaker is designed which is based on the current sensing across a series element typically a CT (current Transformer). The current sensed which is compared against the preset value proportional to the voltage by comparator which is inbuilt in PIC Micro controller to generate an output that drives a relay through a MOSFET to trip the load very fastly.

Keywords: Microcontroller, CT, Relay, MOSFET.

INTRODUCTION

In this project electrical system can be protected from the over load condition. Industrial instruments or home appliances failures have many causes and one of the main causes is over load. The primary of the distribution transformer or any other transformer is designed to operate at certain specific current, if that current flowing through that instrument is more than the rated current, then immediately the System may burn because of over load, through this project we are going to protect the system from over load condition. In this project work for generating high current or over load current more loads are applied to the circuit; so that the current will be increased. Whenever the over current is drawn by load the circuit will be tripped. To trip the circuit we are using one relay which will be controlled through PIC microcontroller. When over load occurred the relay will trip the total circuit. And it will be monitored on the LCD. LCD displays are used to display the status of circuit breaker. For protection from over current condition first we have to measure the total load current. Here we are using CT for measuring the load current and the output of CT is given to ADC for converting analog output of CT into digital data. Hence ADC output is given for monitoring purpose. When current increases behind certain limit then we are going to trip the load by using relay. In this project we are using 230v bulbs as a load. We are going to increase the load by increasing the number of bulbs ON. When we ON more bulbs it causes over load condition and microcontroller will detect that and it will trip the total load by using relay through MOSFET which acts as switching circuit.

EXPLANATION

The main power supply is given directly to load through CT and step down transformer. 230 volt is Step down to 12v and supplied to regulated supply unit which consist of bridge rectifier to convert ac to dc and passed through 7805 regulator to get 5v supply for working of microcontroller, capacitor filters are used to remove the ripples to get pure constant dc voltage. The current passing to load is sensed by the current transformer and output of CT will be in analog form is given to the ADC pin of PIC microcontroller for converting the analog output to digital data. The current sensed is compared with the inbuilt comparator of microcontroller which as pre-set reference value. If the current sensed is less than the pre-set value than MOSFET will be in OFF state and relay will not trip the supply to load. As we increase the load current drawn is more so if the current is increase than the pre-set value than MOSFET will turn ON and energizes the relay. Thus LED used as an indicator is properly biased, and it glows. The relay coil gets energized, causing the armature to shift its position to the normal open point from the normal closed point.

The AC supply to the load is thus cut off from the load and the load is tripped. Once the circuit is tripped it must be reset for further use using reset button as shown in Fig.1. In either case, the microcontroller is programmed so as to show the status of the output on the LCD interfaced to it. In case of normal operation microcontroller will pin will receive 5v dc from regulator and accordingly displays the status on the LCD. In case of any abnormalities, the microcontroller pin doesn’t receive the 5V input signal and the related status is accordingly displayed on the LCD.

 

Fig.1. Block Diagram of Proposed System.

TABLE I: Trip Current Setting

 

Fig.2. PIC Microcontroller.

During this implementation an 8 bit peripheral interfaced controller microcontroller is used with following specifications as shown in Fig.2.

·       RAM 256 bytes

·       ROM 4 kilo bytes

·       8 bit Processor

·       4 I/O Ports

·       Timers 2

·       Power saving mode

·       RXD TXD interfacing

HARDWARE IMPLEMENTATION

The fig.3 shows the hardware implementation of ultra fast acting electronic circuit breaker using microcontroller.

 

Fig.3. Hardware implementation.

CONCLUSION

Now A days the protection and control of equipment plays a very important role. To avoid electrical failure we use fast responding circuit breakers because of its considerable accuracy in fault detection and cut off- time, and also its smooth operation compared to conventional type. Future Scope: The operating time of electromagnetic relay can be improved by using sophisticated electronic components.

REFFERENCE

[1]Raj kamal –Microcontrollers Architecture, rogramming, Interfacing and System Design.

[2]Mazidi and Mazidi –Embedded Systems.

[3]PIC-Microcontroller Manual – Microchip.

[4]A M S Almadji & J G J Sloot review of Current limitting IEEE.

[5]T. Genji , Nakamar: high speed circuit Breaker for electric power system.

[6]200WAS RI BIN ABU ,HARUN:Over Current protection using PIC Microcontroller IEEE.