Generally power systems operate under varying conditions. This variation is due to imbalance between the reactive power generated and absorbed. A power system is said to be stable, when it is operating at unity power factor, maintaining flat voltage profile and it should have tendency to operate under desirable mode even when the system is subjected to undesirable condition such as faults or sudden change of load etc.
Due to reactive power, it is difficult to maintain flat voltage profile i.e; when the reactive power generated is more than consumed at the load, then the voltage at the receiving end will be high and when the reactive power generated is less than consumed at the load, then the voltage at the receiving end is less. This also leads to change in power factor which directly effects the power transfer capability of the system. When power is given to the load through transmission network with fixed sending end voltage, the receiving end voltage changes, because in a power transmission line the receiving voltage depends upon the magnitude and power factor of the load.
By connecting shunt capacitors across the inductive loads the reactive VAR transmitted over the line is reduced. This is because a part of the reactive VAR required by the load will be supplied by shunt capacitors, resulting in power factor improvement. Also, if shunt capacitors are connected across capacitive loads or light loads then they absorb some of the leading VAR resulting in power factor correction and also the voltage across the load is balanced. Capacitors are connected either directly to bus bar or to the tertiary winding of a main transformer and are disposed along the route to minimize the losses and voltage drops.
The voltage boost due to shunt capacitor is evenly distributed over the transmission lines and the power factor of the load is improved by the use of shunt capacitor. When the kVA demand on the distribution system rises and bus voltage drops, shunt capacitors are switched to raise the line voltage.
Due to reactive power, it is difficult to maintain flat voltage profile i.e; when the reactive power generated is more than consumed at the load, then the voltage at the receiving end will be high and when the reactive power generated is less than consumed at the load, then the voltage at the receiving end is less. This also leads to change in power factor which directly effects the power transfer capability of the system. When power is given to the load through transmission network with fixed sending end voltage, the receiving end voltage changes, because in a power transmission line the receiving voltage depends upon the magnitude and power factor of the load.
By connecting shunt capacitors across the inductive loads the reactive VAR transmitted over the line is reduced. This is because a part of the reactive VAR required by the load will be supplied by shunt capacitors, resulting in power factor improvement. Also, if shunt capacitors are connected across capacitive loads or light loads then they absorb some of the leading VAR resulting in power factor correction and also the voltage across the load is balanced. Capacitors are connected either directly to bus bar or to the tertiary winding of a main transformer and are disposed along the route to minimize the losses and voltage drops.
The voltage boost due to shunt capacitor is evenly distributed over the transmission lines and the power factor of the load is improved by the use of shunt capacitor. When the kVA demand on the distribution system rises and bus voltage drops, shunt capacitors are switched to raise the line voltage.
1 comments:
was quite hlpful..
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