VOLTAGE COMPENSATION
REYES, SABAÑA, SOMBRADO, VALENZUELA AND
VIVO
It is defined as the management of reactive
power to improve the performance of ac
systems. There are two aspects:
• Load Compensation – The main objectives
are to :
1. increase the power factor of the system
WHAT IS 2. to balance the real power drawn from the
REACTIVE POWER system
COMPENSATION? 3. compensate voltage regulation
4. 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.
When the voltage is below the required level,
reactive power produced by inductance needs
WHAT IS to be offset by capacitance.
REACTIVE POWER
COMPENSATION?
When the voltage is above the required level,
reactive power produced by capacitance
needs to be offset by inductance.
• Power is referred as the product of voltage
and current i.e. power = V x I The portion of
electricity that establishes and sustains the
electric and magnetic fields of alternating-
current equipment. Reactive power must be
WHAT IS supplied to most types of magnetic
REACTIVE equipment, such as motors and transformers.
POWER? In an ac transmission, when the voltage and
current go up and down at the same time,
only real power is transmitted and when
there is a time shift between voltage and
current both active and reactive power are
transmitted.
POWER TRIANGLE
𝑃𝑜𝑤𝑒𝑟 𝑓𝑎𝑐𝑡𝑜𝑟 = 𝑐𝑜𝑠φ
𝑟𝑒𝑎𝑙 𝑝𝑜𝑤𝑒𝑟 𝑘𝑊
= =
𝑎𝑝𝑝𝑎𝑟𝑒𝑛𝑡 𝑝𝑜𝑤𝑒𝑟 𝑘𝑉𝐴
1. 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. It can be provided
METHODS OF by either a current source, voltage source or a
capacitor.
REACTIVE
An ideal shunt compensator provides the reactive
POWER power to the system.
COMPENSATION Shunt-connected reactors are used to reduce the
line over-voltages by consuming the reactive
power, while shunt-connected capacitors are used
to maintain the voltage levels by compensating the
reactive power to transmission line.
TRANSMISSION LINE WITH SHUNT COMPENSATION
2. 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.
METHODS OF
There are two modes of operation –
REACTIVE capacitive mode of operation and inductive
POWER mode of operation.
COMPENSATION A simplified model of a transmission system
with series compensation is shown in Figure
.The voltage magnitudes of the two buses are
assumed equal as V, and the phase angle
between them is δ.
TRANSMISSION LINE WITH SERIES COMPENSATION
3. 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
METHODS OF operation).
REACTIVE The SVC is an automated impedance matching device,
POWER designed to bring the system closer to unity power
factor. If the power system's reactive load is
COMPENSATION 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.
CALCULATIONS OF
COMPENSATION FOR
REACTIVE POWER
• Reactive power is
necessary to generate
magnetic fields, e.g. in
motors, transformers and
generators. This power
oscillates between the
source and the load and
represents an additional
loading.
DETERMINATION OF CAPACITIVE POWER
A load has an effective power of P = 50 kW at 400 V and the power factor is
to be compensated from cosφ = 0.75 to cosφ = 0.95. Determine the required
capacitive power. The power and current before compensation are:
The power and current after compensation are: The required capacitive power is:
CAPACITIVE POWER WITH K FACTOR
The capacitive power can be determined with the factor k for a given effective
power. The k factor is read from a table 1 – Multipliers to determine capacitor
kilovars required for power factor correction and multiplied by the effective
power. The result is the required capacitive power.
For an increase in the power factor from cosφ = 0.75 to cosφ = 0.95, from the
table 1 we find a factor k = 0.55:
DETERMINATION OF CABLE CROSS-SECTION
• A three-phase power of 250 kW, with Un = 400 V, at 50 Hz is to be
transmitted over a cable 80 m in length. The voltage drop must not exceed
4% =16 V. The power factor is to be increased from cosφ = 0.7 to cosφ =
0.95. What is the required cable cross-section?
The current consumption before compensation is:
The current consumption after compensation is:
The effective resistance per unit length for 516 A is:
We must choose a cable with a cross-section of 4 × 95 mm2. The effective resistance per unit length for
380 A is:
CONCLUSION
• From all the previous discussion we can conclude reactive power compensation
is a must for improving the performance of the ac system. By reactive power
compensation we can control the power factor and reduce the consumption of
electricity.
REFERENCES
• Naveen, Venkata Satya. Apr 1, 2014. Reactive power compensation .
Retrieved from: https://www.slideshare.net/NaveenKssvs/reactive-power-
compensation-
33009860?fbclid=IwAR3VqCcmBbQg5cuL__ddwgVLfaYSyWSvko8W39aMxreLD6
N8oC_L6AehjrU
• Csanyi, Edvard. January 20, 2017. 4 example calculations of compensation for
reactive power.
Retrieved from: https://electrical-engineering-portal.com/calculations-compensation-
reactive-
power?fbclid=IwAR3TZXYC135bGdO9pFpSyNa8GmspQDJ1xu5SforLGlBEhxmt3BO
fFTDiBZg
