This document discusses various methods of reactive power compensation including shunt compensation using shunt reactors and capacitors, series compensation using series reactors and capacitors, static VAR compensators (SVCs) which use thyristor-controlled reactors and capacitor banks to regulate voltage, and synchronous condensers which are synchronous machines that can generate or absorb reactive power by varying excitation current to control reactive power flow. The purpose of reactive power compensation is to improve power factor, regulate voltage, eliminate current harmonics, and increase transmission capacity.
3. • Reactive power (VAR) compensation is defined as the management of
reactive power to improve the performance of ac systems. There are two
aspects:-
• Load Compensation – The main objective is to :-
• increase the power factor of the system to balance the real power
drawn from the system compensate voltage regulation
• to eliminate current harmonics.
• Voltage Support – The main purpose is to decrease the voltage fluctuation
at a given terminal of transmission line.
• Therefore the VAR compensation improves the stability of ac system by
increasing the maximum active power that can be transmitted.
INTRODUCTION
4. WHAT IS REACTIVE POWER?
Reactive power can be best described as the quantity of unused power that is developed
By reactive components such as inductors or capacitors in an Ac circuit or system.
Or
The power flows back and forth without being used up is called reactive power .
5. POWER TRIANGLE
▪ POWER FACTOR=COSø =REAL POWER/APPARENT POWER =Kw/Kva
▪ Whenever there is a phase shift between V and I we have:-
a) real power(kW)
b) reactive (imaginary) power (kVAR)
c)the combination is a complex or apparent power(kVA)=√(kW) ² +(kVAR²)
Apparent power
(VA)
Reactive Power
(VAR)
Real Power
(watts)
Impedance
angle
6. Need for Reactive Power Compensation
Reactive power generated by the ac power source is stored in a capacitor or a reactor
during a quarter of a cycle and in the next quarter of the cycle it is sent back to the power
source.
Therefore the reactive power oscillates between the ac source and the capacitor or reactor
at a frequency equals to two times the rated value (50 or 60 Hz). So to avoid the circulation
between the load and source it needs to be compensated .
Also to regulate the power factor of the system and maintain the voltage stability we need to
compensate reactive power .
7. Methods of Reactive Power
▪ Shunt compensation
▪ Series compensation
▪ Synchronous condensers
▪ Static VAR compensators
▪ Static compensators
8. Shunt compensation
▪ The device that is connected in parallel with the transmission line is called the shunt
compensator.
▪ A shunt compensator is always connected in the middle of the transmission line.
SHUNT REACTOR
▪ In night time the system will be subjected to light load.
▪ At that time VR >VS.
SHUNT CAPACITOR
▪ Suppose here we have excessive amount of load connected or large size of induction
motors are connected.
▪ And requires a huge amount of reactive power.
9. Series compensation
▪ When a device is connected in series with the transmission line it is called a
series compensator. A series compensator can be connected anywhere in
the line.
▪ There are two modes of operation – capacitive mode of operation and
inductive mode of operation.
Series Reactor
Line has its own reactance but sometimes when fault occurs the fault current
will flow through transmission line.
The fault current is limited by reactor.
Series Capacitor
Whenever the line reactance is more PR will be less so if X is high PR is going to
be reduced.
10. Static VAR compensators
▪ A static VAR compensator (or SVC) is an electrical device for providing
reactive power on transmission networks.
▪ The term "static" refers to the fact that the SVC has no moving parts (other
than circuit breakers and disconnects, which do not move under normal SVC
operation).
▪ The SVC is an automated impedance matching device, designed to bring
the system closer to unity power factor. If the power system's reactive load is
capacitive(leading), the SVC will use reactors (usually in the form of thyristor-
Controlled Reactors) to consume VARS from the system, lowering the system
voltage.
▪ Under inductive (lagging) conditions, the capacitor banks are automatically
switched in, thus providing a higher system voltage.
11. Synchronous Condensor
▪ Synchronous condenser is a synchronous machine which is used to generate or absorb
reactive power.
▪ When it is absorbing power it acts like an inductor and when it is generating power it acts
like a capacitor.
▪ When absorbing power it is underexcited and when generating power it is over excited.
▪ Its reactive power can be controlled by varying excitation current.
▪ It is used for shunt reactive power compensation and to improve the stability of the system
and to maintain the voltage at desired limits.
