THREE PHASE FAULT ANALYSIS WITH AUTO RESET ON TEMPORARY FAULT AND PERMANENT TRIP

A fault in a power system is any failures which interface with the normal flow of current. The cause of electric power system faults is insulation breakdown. This breakdown can be due to a variety of different factors such as Lightning stroke, Spray on insulators, Trees coming in contact with wires, Equipment failure, Human Errors as per the studies 70%90%.Various studies have shown that anywhere from 70%, to as high as 90%, of faults on most overhead lines are transient [1]. A transient fault, such as an insulator flashover, is a fault which is cleared by the immediate tripping of one or more circuit breakers to isolate the fault, and which does not recur when the line is re-energized. Faults tend to be less transient (near the 80% range) at lower, distribution voltages and more transient (near the 90% range) at higher, sub-transmission and transmission voltages. Lightning is the most common cause of transient faults, partially resulting from insulator flashover from the high transient voltages induced by the lightning [2].other possible causes are swinging wires and temporary contact with foreign objects. Thus, transient faults can be cleared by momentarily deenergizing the line, in order to allow the fault to clear. Autoreclosing can then restore service to the line [3]. The remaining 10-30% of faults are semi-permanent or permanent in nature. A small branch falling onto the line can cause a semi-permanent fault. In this case, however, an immediate de-energizing of the line and subsequent auto reclosing does not clear the fault. Instead, a co-ordinate timedelayed trip would allow the branch to be burned away without damage to the system [4]. Semi-permanent faults of this type are likely to be most prevalent in highly wooded areas and can be substantially controlled by aggressive line clearance programs. Permanent faults are those that will not clear upon tripping and reclosing. An example of a permanent fault on an overhead line is a broken wire causing a phase to open, or a broken pole causing the phases to short together. Faults on underground cables and overhead lines [5]. Although auto reclosing success rates vary from one company to another, it is clear that the majority of faults can be successfully cleared by the proper use of tripping and autoreclosing [8]. This de-energizes the line long enough for the fault source to pass and the fault arc to de-energize, then automatically recloses the line to restore service. Thus, autoreclosing can significantly reduce the outage time due to faults and provide a higher level of service continuity to the customer [9]. Furthermore, successful high-speed reclosing auto reclosing. On transmission circuits can be a major factor Abstract: This project to develop an automatic tripping mechanism for the three phase supply system. The project output reset automatically after a brief interruption in the event temporary fault while it remains in tripped condition in case of permanent fault. The major advantage of the project is, it is not only save the appliance but it will also show the type of fault that has been occurred in the system so it will be easy for the operator to solve the problem easily. It will also check whether the fault is permanent or temporary fault. If the fault is temporary fault then the supply will be restored after a predefined time of 15sec otherwise permanent trip signal is given to the relay. The concept in the failure can be extended to developing a mechanism to send message t the authorities via SMS by interfacing a GSM model.