28-12-2012, 06:14 PM
OVER CURRENT PROTECTION RELAY USING PIC MICRO CONTROLLER
OVER CURRENT PROTECTION RELAY USING PIC.doc (Size: 1.9 MB / Downloads: 126)
Overview of Over Current Relay Project
An "Over Current Relay" is a type of protective relay which operates when the load current exceeds a preset value. In a typical application the over current relay is used for over current protection, connected to a current transformer and calibrated to operate at or above a specific current level. This project will attempt to design and fabricate over current protection relay using PIC micro controller. The PIC micro controller will cause the circuit breaker to trip when the current from load current reaches the setting value in the PIC micro controller.
In order to design it, first the load current need to measure in order to monitor it using current sensor including testing the fault (over current) and when such condition arise, it will isolate in the shortest time possible without harming the
any other electrical devices. It will also including in developing the algorithm for
instantaneous over current relay and IDMT (Inverse Definite Minimum Time) relay for the circuit breaker to trip. In this project, PIC microcontroller will be used to control and operate the tripping coil in circuit breaker.
Objective
The objectives of this project are;
1)To design and fabricate over current protection relay using PIC micro controller which can operate on the permissible conditions by setting theover current value.
2) To test unwanted conditions (over current) and when such conditions
arise to isolate the fault condition in the shortest time possible.
3)To investigate IDMT curve characteristic.
THEORY AND LITERATURE REVIEW
What Is Over Current
The National Electrical Code defines over current as any current in excess of the rated current of equipment or the ampacity of a conductor. It may result from overload, short circuit, or ground fault. Current flow in a conductor always generates heat. The greater the current flow, the hotter the conductor. Excess heat is damaging to electrical components. For that reason, conductors have a rated
continuous current carrying capacity or ampacity. Over current protection devices
are used to protect conductors from excessive current flow. These protective devices are designed to keep the flow of current in a circuit at a safe level to prevent the circuit conductors from overheating.
Why Protection System Is Important
Fault impose hazard to both user and the system itself and when it comes to user, life is the concern and when it concern the system it is merely to provide stable electrical power system on top of that prevent damage to the expensive equipmentused.