Reactive Power Compensation

 

EACTIVE POWER REACTIVE COMPENSATION 

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CONTENTS INTRODUCTION DEFINITION NEED FOR REACTIVE POWER COMPENSATION METHOD OF COMPENSATION TYPES OF COMPENSATION FIXED COMPENSATION vs. DYNAMIC COMPENSATION INFORMATION REQUIRED FOR DESIGNING RPC CAPACITOR IN RPC POWER R FACTOR CORRECTION CORRECTION  AUTOMATIC POWE POWER BENEFITS OF RPC CONCLUSION REFERENCE

 

 

INTRODUCTION Major industrial loads e.g. induction motors, furnaces, transformers, etc. need reactive power for  sustaining the magnetic field.As in case of induction  

machine power is needed just to in create airthe gapreactive magnetic field.Series inductance transmission lines implies consumption of reactive power. Reactors, fluorescent lamps and all inductive circuits on the whole require a certain amount of reactive power to work. Thus reactive power is not delivered as effective mechanical power outputconverted of motor unlike the re real al power which is effectively as mechanical output.   

 

Definition:  Any connected in which is connected Any device which shunt or series with the load and which is capable of supplying the reactive power demanded by the load is called a Reactive power  compensation device.

 

 

NEED FOR REACTIVE POWER COMPENSATION The power supplier charges penalty for  excessive consumption of reactive power. Reduced energy losses make reactive power  profitable. machines ines  Additional Additional mach machin es are to be connected to already fully loaded substations, cables or  transformer. The power transmission for a new plant can be planned more economically if power factor  correction is taken into consideration.  

 

METHODS OF COMPENSATION There are two major ways of reactive compensation

1. Shunt compensation:

 

Shunt capacitors are connected in parallel in the system and are used mainly for power factor improvemen improvementt and in harmonic It also boosts the voltage of thefilters. bus. This also known as load compensation.

 

 

2. Series compensation Series capacitor are connected in series in the lines and are used mainly for boosting the receiving end voltage, increase in transmission capacity and reduction in losses in the lines. It also improve power factor at the sending end of the line. Unlike shunt capacitor whose output depends on the voltage, the voltage improvement by series capacitors increase with increase in load current. In other word the series capacitor is a self  regulating type. Series compensation is also known as live compensation.  

 

TYPES OF COMPENSATION There are different types of compensation:

(1)Individual compensation: (1)Individual compensation value limited by the limitation:-compensation: no load KVA of the motor. Risk of the high inrush currents due to parallel switching. Not feasible to design an effe effective ctive harmonic filter. e:- Additional con  Advantag control trol and protection  Advantage:equipments not required. Overcompensation are avoided.   

 

2)Group compensation:   Limitation:-Require separate control and  

device. scheme can be  Advantage:-protection Proper protection provided. It can be used as

effective harmonic filters. (3)Central compensation: Limitation:-Cannot unburden the transformer    from reactive power  loading. Cannot reduce system loss.  Advantage:-This could be most economical.   if single large bank has to be used for improvement of P.F. only to  

avoid the penalty  

FIXED COMPENSATION  VS   DYNAMIC COMPENSATION FIXED COMPENSATION:-Here the reactive power fed by the capacitors to the system is fixed. These are basically breaker controlled capacitors andhaving are used in pattern system of which has constant load a set operation. COMPENSATION:  DYNAMIC COMPENSATION:-Here COMPENSATION:--Here Here the reactive power fedThis by the capacitors the system is dynamic. is done using to thyristor controlled capacitors. These are used in systems where the loads are fluctuating in nature like arc furnace loads.    

 

INFORMATION REQUIRED FOR DESIGNING R.P.C SHUNT COMPENSATION:1. System voltage with variation 2. System frequency with variation 3. Actual system fault level 4. Uncompensated power factor  5. Harmonic generating loads or harmonic current

generated in the system

SERIES COMPENSATION:1. Load details at each bus 2. Line parameters 3. Voltage improvement required 4. Maximum and Minimum load  

 

CAPACITOR IN REACTIVE POWER COMPENSATION Capacitor can be viewed as generator of  reactive power  When a capacitor connected across the load ,the capacitor supplies the reactive power to network the load, by relieving transmission there which can carry only the active power. mac  As opposed to the rotating machines, hines, the machines, capacitor is a device with no moving parts, which generates reactive power. High voltage capacitors are built up a single phase capacitor units.    

 

POWER ER FACTOR  AUTOMATIC POW CORRECTION(APFC) capacitor output is fixed when when the load If the the capacitor decreases, total load will be capacitive at low active load. Thus depending on the actual short circuit capacity of the bus, the additional reactive power  will cause a rise in the voltage on that bus. In order to avoid the disadvantage disadvantage ,plants with fluctuating loads are often provided with automatic regulation.  

 

BENEFITS OF REACTIVE POWER COMPENSATION Better efficiency of power generation, transmission and distribution Improvement Improvement in voltage Reduced KVA demand Higher load capability. Reduced system losses.

 

 

The figure show the relation between apparent (S), active (P),factor and reactive power (Q) at a certain power of the load. The load is uncompensated and if the conductor  or the transformer is fully loaded the arc of the circle defines the maximum power output.  

 

CONCLUSION When a capacitor connected across the load,the capacitor supplies reactive power to the load, thereby network carry only the active power. By reducing the negative impact of reactive power in high voltage AC networks, the capacity of transmission systems can be dramatically increased. This means greater reliability and better use of existing lines. RPC reduce energy loss.  

 

REFERENCE www.abb.com Elements of power system analysis by W.D.Stevenson,TMH

   

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