The document discusses reactive power consumption in modern power systems, explaining its importance in maintaining voltage levels and supporting electrical loads. It outlines the need for reactive power control through various equipment like synchronous condensers, capacitor banks, and static var compensators to prevent voltage collapse and ensure system stability. The conclusion emphasizes that reactive power is essential for the efficient operation of electrical systems, influencing both economic benefits for end users and increased capacity for utilities.

1. Reactive Power Consumption In
Modern POWER System
Presented By : Rahul Dey
(Electrical 4th Year)

2. INTRODUCTION
What is Reactive Power?
 It describes the background energy movement in an AC
system arising from the production of electric and
magnetic fields
 It is the combination of continuous forward-moving or
‘real’ energy flow, combined with the sloshing or
‘imaginary’ energy flow
 It is used for core magnetization of Alternators
 It is non-consumable. Only becomes important when
‘electrical load’ contains coils or capacitor

3. AC POWER PHASOR

4. Why Do We Need Reactive Power?
 Reactive power (VARs) is required to
maintain the voltage to deliver active power
(watts) through transmission lines
“Indexing of Active Power consumption is
called Reactive Power !!”
Electro-Mechanical devices and other loads
require reactive power
Reactive power deficiency causes the voltage
to sag down

5. Importance Of Reactive Power
• Refers to the circulating power in the grid that
does no useful work, non consumable
• Results from energy storage elements in the
power grid (mainly inductors and capacitors)
• Has a strong effect on system voltages
• It has to be balanced in the grid to prevent voltage
problems, has to be maintained for a secure and
stable Transmission System
• Reactive power levels have an effect on voltage
collapse

6. NEED FOR REACTIVE POWER
CONTROL
Denoting Reactive Power as “Q”:
Case 1: Q > Qmax
 Excess Q causes excess magnetization
in core
 Eddy current increases to a high value
 Excessive heat generation occurs
 Thermal breakdown of the insulation
 Unwanted Dead Short Circuit occurs

7. Case 2: Q < Qmin
 Insufficient magnetization
causes improper work done
 Results in large gap between
input and output
 Localized oscillations occur
 System becomes unstable

8. EQUIPMENTS
Equipments for Reactive Power Control are:
 Synchronous Condenser
 Capacitor Bank
 Series Compensator
 STATCOM
 Shunt Reactor
 Static VAR Compensator
a) Thyristor-Controlled Reactor (TCR)
b) Thyristor Switched Capacitor (TSC)
c) Saturated Reactors

9. SYNCHRONOUS CONDENSER
Synchronous Condensers - Synchronous motor
running at no load to provide reactive power
support, mainly used to adjust grid’s voltage by
either generating or absorbing reactive power,
improve power factor
Location:
 At the receiving end of long transmission lines
 In important substations
 In conjunction with HVDC converter stations
 Reactive power output is continuously controllable

11. Working Conditions
• Synchronous Motor operating at leading power
factor is used for lagging Reactive power
control
• Under this condition the excitation of motor is
greater than its input terminal voltage
• Hence the characteristics becomes almost
similar to a capacitor
• Motor runs with lagging power factor when it
is under-excited

12. CAPACITOR BANK
• Shunt capacitors - Mechanically switched or
fixed shunt capacitor banks installed at
substations or near loads
• Keeping voltage within required limit
Advantage:
 much lower cost compared to SVCs
 Switching speeds can be quite fast with current
limiting reactors to minimize switching
transients.

14. Working Conditions
 Capacitor bank may be
in Star or Delta
connection
 They generate leading
VAR, hence
compensating the
lagging VAR
 Value of capacitor
should suffice the
excessive lagging VAR

15. DISADVANTAGES
 Reactive power output drops with the voltage squared
 For transient voltage instability the switching may not
be fast enough to prevent induction motor stalling
 Precise and rapid control of voltage is not possible
(capacitor banks are discrete devices, but they are often
configured with several steps to provide a limited
amount of variable control)
 If voltage collapse results in a system, the stable parts
of the system may experience damaging overvoltage,
immediately following separation

16. SERIES COMPENSATOR
 Capacitor connected in series with the load
 The voltage of the line inductance is
compensated by the capacitor voltage
 Capacitor voltage is inversely proportional to
capacitance
 Hence the value of capacitance is chosen
accordingly

18. Advantages: Disadvantages:
• Reduces line voltage • Once a capacitor in a
drops transmission line gets
• Limits load-dependent damaged, then the entire
voltage drops power flow scheme is
• Influences load flow in interrupted
parallel transmission lines • Maintenance is difficult
• Increases transfer
capability
• Reduces transmission
angle
• Increases system stability

19. FACTS
 Flexible AC Transmission System : System composed of
static equipment, used to enhance controllability and
increase power transfer capability of AC transmission
 Classifications :
 Series Compensation – FACTS connected in series, acts as a
controllable Voltage source
 Shunt Compensation –FACTS connected in parallel, acts as
a controllable Current source
1. Shunt Capacitive Compensation – Used to improve power
factor
2. Shunt Inductive Compensation – Used for charging
transmission line

20. Applications Of FACTS
 Series Compensation:  Shunt Compensation:
• Static synchronous series • Static synchronous
compensator (SSSC) compensator (STATCOM)
• Thyristor-controlled series • Static VAR compensator
capacitor (TCSC) (SVC)
• Thyristor-controlled series a) Thyristor-controlled
reactor reactor (TCR)
• Thyristor-switched series b) Thyristor-switched
capacitor reactor (TSR)
• Thyristor-switched series c) Thyristor-switched
reactor capacitor (TSC)

21. Static VAR Compensator (SVC)
 Static VAR Compensator – Provide fast acting reactive power, regulates
voltage and stabilizes system
 Automated impedance match device, brings the system near unity power
factor
 Principle :
 Thyristor controlled reactor (TCR) – Consume VARs from capacitive load
system
 Thyristor switched capacitor (TSC) – Add VARs to a inductive load system
 Harmonic filter – Eliminates harmonic distortions
 Mechanically switched capacitors or reactors (MSC)
 Location :
Near high and rapidly varying loads, Exmp. Arc Furnaces

22. Static VAR Compensator (SVC)

23. STATCOM
 Static Synchronous Compensator :
 Regulating device, acts as either a source or sink of
reactive AC power
 Voltage source converter (VSC)-based device
 STATCOM generates reactive current if the terminal
voltage of the VSC is higher than the AC voltage at the
point of connection
 It absorbs reactive power when amplitude of the
voltage source is lower than the AC voltage
 STATCOM can be designed to be an active filter to
absorb system harmonics

24. Advantages Over SVC
• Maximum reactive output current will not be
affected by the voltage magnitude
• Therefore it exhibits constant current
characteristics when the voltage is low under the
limit
• SVC's reactive output is proportional to the
square of the voltage magnitude, hence reactive
power decreases rapidly when voltage decreases,
reducing system stability
• Speed of response of STATCOM faster than SVC
• Harmonic emission is lower than SVC

25. STATCOM Based On Current STATCOM Based On Voltage
Source Converter Source Converter

26. SHUNT REACTORS
 Shunt reactors – mainly
used to keep the voltage
down
 Absorb reactive power
in the case of light load
and load rejection
 Compensate the
capacitive load of
transmission lines

27. HARMONIC FILTER
 Large quantities of harmonics can lead to
malfunctioning of the system that results in
downtime and increase in operating costs.
 A harmonic filter is used to eliminate the
harmonic distortion caused by appliances.
 The harmonic filter is built using an array of
capacitors, inductors, and resistors that deflect
harmonic currents to the ground.
 Each harmonic filter could contain many such
elements, each of which is used to deflect
harmonics of a specific frequency.

28. Harmonic Filter

29. CONCLUSION
 Voltage control is essential to reduce transmission losses and to
maintain the ability of the system to withstand and prevent voltage
collapse
 Decreasing reactive power causing voltage to fall while increasing it
causing voltage to rise
 Raising power factor is a proven way of increasing the efficient use
of electricity by utilities & end users
 Economic benefits for end users may include reduced energy bills,
lower cable, transformer losses & improved voltage conditions,
while utilities benefit from increased system capacity by improving
reactive power management
 Finally we can say, reactive power is essential in order to supply real
power, without it transformers, induction motors will not run in
absence of magnetic excitation which is supplied by reactive power

30. References
A Course In Power Systems
by J.B.Gupta
Modern power System Analysis
by D.P.Kothari & I.J.Nagrath
www.wikipedia.com
www.google.co.in