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4 Main Means For The Generation Of Reactive Power
electrical-engineering-portal
...
Synchronous alternators
2
...
Static var compensators (SVC) and
4
...
Synchronous alternators
Synchronous alternators are the main machines used for the generation of electrical energy
...

Besides, without going into technical details, by acting on the excitation of alternators, it is possible to vary the
value of the generated voltage and consequently to regulate the injections of reactive power into the network, so
that the voltage profiles of the system can be improved and the losses due to joule effect along the lines can be
reduced
...
Synchronous compensators
They are synchronous motors running
no-load in synchronism with the
network and having the only function
to absorb the reactive power in
excess (under-excited operation) or
to supply the missing one (overexcited
operation)
...
The design also takes into account optimum erection, commissioning, testing
and plant layout

Where:
E = e
...
f
...
The use of synchronous compensators in power distribution
networks is not favourable from an economic point of view because of their high installation and

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maintenance costs
...
Static var compensators
The considerable development of power
electronics is encouraging the replacement
of synchronous compensators with static
systems for the control of the reactive
power such as for example TSC (thyristor
switched capacitors) and TCR (thyristor
controlled reactors)
...


Figure 1 – Under-excited synchronous compensator

Figure 2 – Over-excited synchronous compensator

TSC allow a step-by-step
control of the reactive power
delivered by groups of
capacitors, whereas with TCR
a continuous control of the
reactive power drawn by the
inductors is possible
...

From the point of view of
applications, these devices are
used above all in high and
very high voltage networks
...
Banks of static capacitors
A capacitor is a passive dipole consisting of two conducting surfaces called plates, isolated from one another

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by a dielectric material
...

The last generation capacitors are dry-type and undergo a specific treatment which improve their electrical
characteristics
...

According to the geometry of
the metal plates, it is possible
to have:
Plane capacitors;
Cylindrical capacitors;
Spherical capacitors
...
The rated capacitance
C – the value obtained from
the rated values of power,
voltage and frequency of
the
capacitor;

Chenier Static VAR Compensator Substation – 735 kV by ABB / Hydro-Quebec

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The rated voltage Un – the r
...
s
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The rated frequency f n – the frequency for which
the capacitor has been designed
...

Such energy is given by the following relation:
where:
C is the capacitance;

Figure 4 – Bank of static capacitor

U is the voltage applied to the terminals of the
capacitor
...


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In particular, the power factor correction capacitors used for low voltage applications are constituted by singlephase components of metalized polypropylene film and can be of the self-healing type
...

Go

Figure 5 – Capacitor types (plane, cylindrical and spherical)

back to Index ↑
Reference // Power factor correction and harmonic filtering in electrical plants – ABB

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