Reactive power compensation

A
PRESENTATION
ON
“REACTIVE
POWER COMPENSATION”
_______________________________
KHALIQ AHMED (TEQIP026588)
KHALIQ AHMED
Assistant Professor
1

Contents
 Introduction
 Need of Reactive power
 Reactive power Compensation
 Principal of Power Transmission
 Types of Compensation
 FACTS Devices
 Static VAR Compensation (SVC)
 Static Compensator (STATCOM)
 Synchronous Condenser
 Conclusion
2

Introduction
Reactive power is an essential tool to transmit the active power
through the AC Network. It required to maintain voltage of
transmission network for the smooth transmission of Active power.
 In an ac transmission, when the voltage and current go up and
down at the same time, only real power is transmitted.
 When there is a time shift between voltage and current both active
and reactive power are transmitted.
 The portion of power averaged over a complete AC waveform, is
the real power .
 The portion of power flow that is temporarily stored in the form of
magnetic or electric fields, due to inductive and capacitive network
elements, and then returned to source is known as Reactive Power.
3

It can also be defined as the agent of energy required for
establishment of the magnetic field inside the system. It is very
essential in electromechanical energy conversion process.
Q = V * I sin Ø
This reactive power generated or consumed must be within the
limit as: Qmin < Q < Qmax
If Q > Qmax: The excess reactive power will set up flux to be more
with core thereby eddy current increases which causes excessive
heating of core by which thermal breakdown of insulation is possible.
If Q < Qmax: The insufficient magnetic path is created inside the
machine which may cause improper work done thereby output is not
proportional to the input which leads to problem of instability.
4

Need of Reactive power
 In resistive loads the current produces the heat energy which
produces the desired output but in case of inductive loads the
current creates the magnetic field which further produces the
desired work. Therefore reactive power is the non working power
caused by the magnetic current to operate and sustain magnetism in
the device .
 Reactive power (vars) is required to maintain the voltage to deliver
active power (watts) through transmission lines. When there is not
enough reactive power the voltage sags down and it is not possible to
deliver the required power to load through the lines.
5

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. So to avoid the circulation between
the load and source it needs to be compensated.
 To regulate the power factor of the system and to maintain the
voltage stability we need to compensate reactive power.
 Voltage regulation
 Stability
 Proper Utilization of machines connected to the system.
 Overcome the losses associated with the system.
 Preventing the system from the voltage sag and voltage collapse.
Reactive Power Compensation
6

Principal of Power Transmission
In an electrical power network when the power is transmitted through
EHV AC System then certain parameters plays a key role. In
Alternating Current System actual power is enabled by virtual of
imaginary power. To understand the basic phenomena behind the
power transmission let us model a transmission line one which contain
an equivalent Electrical circuit like a two voltage source separated to
each other by means of a inductance which is usually transmission
line reactance.
7

Active and reactive power of the system is given by:
Power flow can be controlled by applying one of the following means:
 Shunt voltage at the midpoint
 Varying the Line Reactance X
 Voltage with the variable magnitude in series with line
8

Types of Compensation
Compensation in electrical power system is an essential tool for the
improvement of the performance of EHV AC transmission line. For the
smooth transmission of electrical power we need to balance the voltage
violation limit to achieve this objective we can either inject current to
control the voltage or inject the voltage to control the current. However
the two basic types of compensation technique have been used i.e.
 Shunt Compensation.
 Series Compensation.
9

Shunt Compensation
The device that is connected in parallel with the transmission line is
called the shunt compensator. It is also known as load compensation.
Shunt compensation used two kind of technique to improve the system
performance in terms of voltage regulation and reactive power
compensation i.e.
 Shunt connected reactors
 Shunt connected capacitors
10

Series Compensation
Series compensation is basically a powerful tool to improve the
performance of EHV lines. It consists of capacitors connected in series
with the line at suitable locations. A capacitor in series with a line gives
control over the effective reactance between line ends. It is also known as
line compensation.
Xeff = X - Xc
Where X = line reactance
Xc = capacitor reactance
11

For the fixed level of power transmission voltage profile is relatively
flat corresponding to the natural loading or Surge impedance loading
(SIL). The reactive power requirements increase with line length. The
line is said to be naturally loaded if its loading is equal to surge
Impedance Loading (SIL). At SIL the reactive power absorbed is
exactly equal to the reactive power Generation.
QLoss = QGen
jωLI2 = jωCV2
Z = √ L/C (Surge Impedance)
Voltage Profile
12

FACTS Technology
In 1980 Electrical power research institute (EPRI) introduced the
concept of FACTS Technology which intensively increase the use of
power semiconductor devices for the compensation of reactive power.
 Developed by Electrical Power Research Institute (EPRI) in the 80s.
 FACTS devices are used to optimize existing transmission lines.
 FACTS employ high speed Thyristor for switching in or out
transmission line components such as capacitors, reactors or phase
shifting transformer.
 The FACTS technology is not a single high-power controller, but
rather a collection of controllers, which can be applied individually or
in coordination.
13

Types of FACTS Devices
The FACTS controllers can be classified as
1. Shunt connected controllers
2. Series connected controllers
3. Combined series-series controllers
4. Combined shunt-series controllers
Depending on the power electronic devices used in the control, FACTS
controllers can be classified as
(A) Variable impedance type
(B) Voltage Source Converter (VSC)
14

SVC belongs to the category of FACTS devices where the Variable
impedance is found by controlling the firing angle of power
semiconductor devices used. The SVC is designed to bring the system
closer to unity power factor. Types of Static VAR Compensation (SVC)
are:
 Thyristor Switched Capacitor (TSC).
 Thyristor Controlled Reactor (TCR).
 Thyristor Switched Capacitor - Thyristor Controlled Reactor
 Fixed Capacitor Thyristor - Controlled Reactor (FC-TCR).
 Thyristor controlled series compensator (TCSC). (Series Connected)
Static Var Compensator (SVC)
15

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
uses reactors (usually in the form of TCR) to consume VAR from
the system to lowering the system voltage.
 Under inductive (lagging) conditions, the capacitor banks are
automatically switched in, thus providing a higher system voltage.
16

STATCOM
STATCOM is also known as advanced static VAR compensators,
which is essentially a Voltage Source Converter. Advanced version of
SVC with Voltage source Converter is basically known as STATCOM
or Static Compensator.
Basically the VSC based STATCOM are divided into the following
categories.
 Static synchronous Compensator (STATCOM) (shunt connected)
 Static Synchronous Series Compensator (SSSC) (series connected)
 Interline Power Flow Controller (IPFC) (combined series-series)
 Unified Power Flow Controller (UPFC) (combined shunt-series) 17

Basically, the STATCOM system is comprised of
Power converters,
Set of coupling reactors or a step up transformer,
Controller
Advantages of STATCOM:-
 Better reactive power support during faults.
 Fast dynamic response.
 Ability to generate more reactive power
 Both inductive & Capacitive region of operation is possible
 Lower generation of harmonics
18

Synchronous machine working at Variety of operation (leading or
lagging) is known as synchronous machine. It can be obtained by
varying the field excitation of the system.
 An overexcited synchronous motor is working at leading power
factor and supplying the leading VAR to the system.
 An under excited synchronous machine is working at lagging power
factor and taking lagging VAR from the system.
Synchronous Condenser
19

From all the previous discussion we can conclude reactive power
compensation is a must for
 Improving the performance of ac system.
 By reactive power compensation power factor can be improved.
 Reduce the consumption of electricity.
 Increased system efficiency.
 It helps to maintain transmission voltage within the limit.
 Reduced system losses.
 Reduced KVA demand.
Conclusion
20

Reactive power compensation

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