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Introduction of Three Phase Fault
Six numbers of steps down transformers are used for forming star and delta secondary‟s
at low voltage output. Fault condition is created with a set of switches to input LL, LG, 3L fault to the circuit. This triggers a 555 timer in monostable to reset after fault clearance in a short duration temporary fault or permanently trip the output in case of prolonged fault. We know that if the fault accurse then it creates many problems to the load. Many times load is damaged. So it is very important to protect the system again the faults.
Different type of fault in 3 phase is
:
L-L fault (line to line fault) L-G fault (line to ground fault) 2L-G fault (double line to ground fault) Mostly L-G fault (line to ground) fault is occurs in industries, sub station and any other places where three phase supply is used, other fault is occur in bed condition compare to L-G fault. This type fault is damage the load so we prepared the protection circuit which is introduce below;
Introduction of Block Diagram
In prevention circuit six numbers of steps down transformers are used for forming star
and delta secondary‟s at low voltage output.
Fault condition is created with a set of switches to input LL, LG, 3L fault to circuit. This triggers a 555 timer in monostable to reset after fault clearance in a short duration temporary fault clearance in short duration temporary fault or permanently trip the output incase of prolonged fault
The electrical substation which supply the power to the consumers i.e. industries or domestic can have failures due to some faults which can be temporary or permanent. These faults lead to substantial damage to the power system equipment. In India it is common to observe the failures in supply system due to the faults that occur during the transmission or distribution. The faults might be LG (Line to Ground), LL (Line to Line), 3L (Three lines) in the supply systems and these faults in three phase supply system can affect the power system. To overcome this problem a system is built, which can sense these faults and automatically disconnects the supply to avoid large scale damage to the control gears in the grid sub-stations.
This system is built using three single phase transformers which are wired in star input and star output, and 3 transformers are connected in delta connections, having input 220 volt and output at 12 volt. This concept low voltage testing of fault conditions is followed as it is not advisable to create on mains line. 555 timers are used for handling short duration and long duration fault conditions. A set of switches are used to create the LL, LG and 3L fault in low low voltage side, for activating the tripping mechanism. Short duration fault returns the supply to the load immediately called as temporary trip while long duration shall result in permanent trip.
In an electric power system, a fault is any abnormal electric current. For example, a short circuit is a fault in which current bypasses the normal load. An open-circuit fault occurs if a circuit is interrupted by some failure. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a "ground fault" or "earth fault", charge flows into the earth. The prospective short circuit current of a fault can be calculated for power systems. In power systems, protective devices detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.
In a poly-phase system, a fault may affect all phases equally which is a "symmetrical fault". If only some phases are affected, the resulting "asymmetrical fault" becomes more complicated to analyze due to the simplifying assumption of equal current magnitude in all phases being no longer applicable. The analysis of this type of fault is often simplified by using methods such as symmetrical components.
Design of systems to detect and interrupt power system faults is the main objective of power system protection.
Chapter:3
1.HARDWARE COMPONENT
2.TRANSFORMER
3.VOLTAGE REGULATOR
4.FILTER
5.555 TIMER
6.DIODE
7.RELAY
8.RESISTOR
9.CAPACITOR
3.1 Transformer
A transformer is a static electrical device that transfers energy by inductive coupling between its
winding circuits. A varying current in the primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic flux through the secondary winding.This
varying magnetic flux induces a varying electromotive force (emf) or voltage in the secondary winding. Transformers can be used to vary the relative voltage of circuits orisolate them, or both. Transformers range in size from thumbnail-sized used in microphones to units weighing hundreds of tons interconnecting the power grid. A wide range of transformer designs are used in electronic and electric power applications. Transformers are essential for the transmission, distribution, and utilization ofelectrical energy. Fig: Transformer Circuit. The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself. In practice, some flux traverses paths that take it outside the windings. Such flux is termed leakage flux, and results in leakage inductance in series with the mutually coupled transformer windings. Leakage flux results in In an electric power system, a fault is any abnormal electric current. For example, a short circuit is a fault in which current bypasses the normal load. An open-circuit fault occurs if a circuit is interrupted by some failure. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a "ground fault" or "earth fault", charge flows into the earth. The prospective short circuit current of a fault can be calculated for power systems. In power systems, protective devices detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.
In a poly-phase system, a fault may affect all phases equally which is a "symmetrical fault". If only some phases are affected, the resulting "asymmetrical fault" becomes more complicated to analyze due to the simplifying assumption of equal current magnitude in all phases being no longer applicable. The analysis of this type of fault is often simplified by using methods such as symmetrical components.
Design of systems to detect and interrupt power system faults is the main objective of power system protection.
3.1 Transformer
A transformer is a static electrical device that
transfers
energy by inductive coupling between its
winding
circuits. A varying current in the
primary
winding creates a varying magnetic flux in the transformer's core and thus a varying
magnetic
flux through
the
secondary
winding.
This
varying magnetic flux induces a varying electromotive force (emf) or voltage in the secondary winding. Transformers can be used to vary the relative voltage of circuits orisolate them, or both. Transformers range in size from thumbnail-sized used in microphones to units weighing hundreds of tons interconnecting the power grid. A wide range of transformer designs are used in electronic and electric power applications. Transformers are essential for the transmission, distribution, and utilization ofelectrical energy.
Fig: 3.1 Transformer Circuit
The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself. In practice, some flux traverses paths that take it outside the windings. Such flux is termed
leakage flux
, and results in leakage inductance in series with the mutually coupled transformer windings. Leakage flux results in