COMPENSATION OF REACTIVE POWER

COMPENSATION
OF REACTIVE
POWER

TABLE OF
CONTENTS
Introduction01
Reactive Power
Impact of Reactive Power
02
03
Compensate Reactive Power04
Static VAR Compensator05

TABLE OF
CONTENTS
Fixed Capacitor TCR06
Operation
MCR-TCR SCV
07
08
Conclusion09

Introduction
What is reactive power compensation?
 Reactive power compensation is defined as the management of reactive power to
improve the performance of alternating-current (ac) power systems. In general, the
problem of reactive power compensation is related to load and voltage support.
What is reactive power compensation on a grid?
 The reactive power demand can be compensated by reactive power compensation
device, which is helpful to reduce the reactive power flow in the grid, reduce the
electric energy loss due to the delivery of reactive power, and in turn, improve the
operating condition of the grid.

Reactive Power
Reactive Power ( Q ) :The power which flows back and forth that means it moves in both
the directions in the circuit or reacts upon itself, is called Reactive Power. The reactive
power is measured in kilo volt-ampere reactive (kVAR) or MVAR.
Formula to calculate Reactive Power (Q):
Q = V I Sinθ
Reactive Power = √ (Apparent Power2– Active power2)
VAR = √ (VA2 – P2)
kVAR = √ (kVA2 – kW2)

Reactive Power
• The portion of power flow that is temporarily stored in the form of magnetic or electric
fields , due to inductive or capacitive network element and then returned to source is
known as reactive power .
• Reactive power can best be described as the quantity of “unused” power that is stored
in reactive components , such as inductors or capacitors . In other words , the reactive
circuit returns as much power to the supply as it consumes .

Impact of reactive power
 For the majority of components, loads and devices comprising the grid, power is
temporarily stored in them as it passes through them, distorting its waveform before
returning energy to the grid
 This distortion, or shifting of current in time with respect to voltage, causes the total
power to be greater than the real power (because the shift causes the presence of
reactive power)
 Inductive loads constitute a major portion of the power consumed in industrial
complexes, and due to their low PF, require much higher currents than their real
power needs would imply
 These higher currents require larger wires and other equipment to transport, and
increase the energy lost in the T&D system

Impact of reactive power
 Due to the costs of larger equipment required and wasted energy, electrical utilities
will often charge a higher price to industrial or commercial customers if their
operations function at low power factor
 Reactive power must balance in the grid to prevent voltage problems.
 The farther the transmission of power, the higher the voltage needs to be raised to
overcome the resistance to current flow.

Why do we need to compensate reactive power?
Due to capacitive and inductive components, reactive power is temporarily stored in the form
of electric or magnetic fields which flow back and forth. Reactive power can be generated as
well as absorbed by power transmission system elements by shunt saucepans and series
reaction respectively. It originates in a phase shift, if the voltage is lagged by the current
through a device, then the device consumes reactive power. Depending on the phase shift
between the voltage and the current, the amount of reactive power consumption of the device
shall be determined. Since the reactive power simply moves back and forth in the line
(transmission line or any other conductor) it acts as an additional load. Reactive power is
therefore considered for the rating of all cables, transformers, switchgear and other electrical
equipment. This implies that all of these installations must be designed for the apparent power
that considers both active and reactive power. If there is an excess of reactive power, the
system power factor will be significantly reduced and therefore the operating efficiency will
be reduced. This causes undesirable voltage drops, increased conduction losses, excess
heating and higher operating costs.

Method of Reactive power compensation
 Shunt Compensation
 Series Compensation
 Synchronous Compensation
 Static VAR Compensation
We only discuss about Static VAR Compensation.

Static VAR Compensator
In order to compensate reactive power, we found out that Static VAR Compensator (SVC), one
of the most common FACTS device used for reactive power compensation. It’s a variable
impedance device where the current through a reactor is controlled using back to back
thyristor valves. The thyristor valves are used in SVC are rated lower voltage connected by step
down transformer or connected to the secondary winding of a power transformer. The
application of SVC is highly noticed for load compensation of fast charging loads such as steel
mills and ace furnaces. One of the most significant advantages of this SVC is it doesn’t have any
rotating part; it is compensating the reactive power by switching or another word we can say
that SVC is manipulating the angle between voltage and current. Types of SVC is described in
the next slides:

Type of Static VAR Compensator
 Fixed capacitor Thyristor controlled reactor (FC-TCR)
 Thyristor switched capacitor Thyristor Control capacitor (TSC-TCR)
 Mechanically switched capacitor bank (MSC) or reactor bank (MSR)

Fixed Capacitor Thyristor-Controlled Reactor
The Fixed Capacitor Thyristor-Controlled Reactor (FC-TCR) is a var generator arrangement
using a fixed (permanently connected) capacitance with a thyristor controlled reactor as
shown in Fig.
• To maintain the desired voltage at a high voltage bus.
• FC-TCR is a var generator arrangement using a
• Fixed capacitance with a TCR.
• The current in the reactor is varied by the method of firing
delay angle control method. (Qc) of the fixed capacitor
is opposed by the (QL) of the TCR.

Operation
If the voltage bus begins fall below its set point range, the SVC will inject reactive power into
the system, thereby increasing the bus voltage back to its desired voltage level. If bus voltage
increases, the SVC will inject less (or TCR will absorb more) reactive power (within its control
limits), and the result will be to achieve the desired bus voltage.
Capacitive var output :
1) By increasing current in TCR lead to decrease in output.
2) When TCR is off results in max var output.
Zero var output :
1) Cancelling var by equalling both capacitive and
inductive current.

MSC-TCR SVC
• In this instead of fixed capacitor,
mechanically switched capacitors are used
• It is normally used where less number of
switching required
• Like FC-TCR SVC, a small inductance is
connected series with capacitors and tuned
for selected harmonics
• In this also high pass filters are also used for
mitigation of harmomics

MSC-TCR SVC
The purpose of mechanically switched capacitor is to generate stepped reactive power
TCR perform as controlled reactive power absorption when there is excess Var generation
In MSC_TCR SVC the rating if TCR is almost equal to single Mechanically switched
capacitor rating
As Per the requirement of reactive power generation the number of switch is on(for less
reactive power generation less number of switch is on)
Advantages are the lower cost and lower power loss
Disadvantage is slow response due to mechanical switching, switch closes in 2 cycles and
opens in 8 cycles

TSC-TCR SVC
• TSC-TCR type compensator was developed for dynamic compensation with minimized
standby losses and providing increased operating flexibility
• A basic single-phase TSC-TCR typically consists of n TSC branches and one TCR
• The number of branches, n, is determined by practical considerations that include the
operating voltage level, maximum Var output, current rating of the thyristor valves, etc.
• The individual range can also be expanded to any maximum rating by employing
additional TCR or TSR(Segmented TCR) branches
• Total Capacitive output range is divided into n intervals

• In the first interval, the output of the var generator is controllable in the zero to
Qcmax/n range, where Qcmax is total rating provided by all TSC branches.
• In this interval, ope capacitor bank is switched ON and simultaneously the current in
the TCR is set by the appropriate firing delay angle
• So that the sum of the var output if the TSC and that of the TCR equals the capacitive
output required
• In the second, third…, and nth intervals, the output is controllable in the Qcmax/n to
2Qcmax/n, 2Qcmax/n to 3Qcmax by nad,…, and (n-1)Qcmax/n to Qcmax
• In all intervals surplus reactive powe absorbed by using TCR so theoretically TCR
should have the same Var rating as the TSC but switching conditions at the endpoins of
the intervals are not indeterminate. So the var rating of the TCr has to be somewhat
larger in practice that of one TSC in order to provide enough overlap(hysteresis)
between the ‘switching in’ and ‘switching out’ var levels.

Advantages of Static VAR Compensator
 It increased the power transmission capability of the transmission lines.
 It improved the transient stability of the system.
 It controlled the steady state and temporary over voltages.
 It improved the load power factor, and therefore, reduced line losses and improved
system capability.

Conclusion
 Static var compensator perform an important rule for voltage
security and power factor correction.
 The range of reactive power control can be increased by
varying thyristor firing angle.
 Hence it is concluded that SVC (Static VAR Compensator) will
successfully control the dynamic performance of power system
and voltage regulation of the power system.

COMPENSATION OF REACTIVE POWER

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COMPENSATION OF REACTIVE POWER