SVC
Static var compensator
A shunt reactive power compensator built from thyristor-controlled reactors, thyristor-switched capacitors and filters.
SLD
Symbols · TSC
Thyristor-switched capacitor
A capacitor bank switched in or out at current zero by anti-parallel thyristors, giving fast stepwise reactive support.
In plain English
What does Thyristor-switched capacitor mean?
A thyristor-switched capacitor connects a capacitor bank through anti-parallel thyristors, usually with a small series reactor to limit inrush. The thyristors switch the capacitor in at the instant when the network voltage equals the capacitor voltage, avoiding transients, and switch it out at current zero. It is either fully on or fully off.
A simple example
Single-line diagrams show a capacitor, a series reactor and the thyristor pair stacked on a shunt branch. Several TSC branches may be drawn to give multiple steps of capacitive output in a static var compensator or a fast power factor correction system.
What the drawings help you do
Because it switches in discrete steps, fine control comes from combining TSC branches with a TCR. The symbol does not show discharge resistors or the valve voltage rating, which must withstand twice the peak voltage when the capacitor is charged and the network reverses.
This particular reference
A capacitor bank switched in or out at current zero by anti-parallel thyristors, giving fast stepwise reactive support. A TSC switches capacitors in steps without transients; a mechanically switched capacitor uses a breaker and is much slower.
- Signal
- Electrical information passed between devices, rather than necessarily the main power supply.
- Rating
- A value stating the conditions for which equipment is specified.
- Schematic
- A drawing showing function and connections rather than physical appearance.
Read the source: Static Var Compensators (SVC) · Capacitive component symbols
SLD / Schematic · TSC
What it represents
A thyristor-switched capacitor connects a capacitor bank through anti-parallel thyristors, usually with a small series reactor to limit inrush. The thyristors switch the capacitor in at the instant when the network voltage equals the capacitor voltage, avoiding transients, and switch it out at current zero. It is either fully on or fully off.
Single-line diagrams show a capacitor, a series reactor and the thyristor pair stacked on a shunt branch. Several TSC branches may be drawn to give multiple steps of capacitive output in a static var compensator or a fast power factor correction system.
Because it switches in discrete steps, fine control comes from combining TSC branches with a TCR. The symbol does not show discharge resistors or the valve voltage rating, which must withstand twice the peak voltage when the capacitor is charged and the network reverses.
How to read it
- A small series reactor is part of the branch, not a separate filter.
- Count branches to find available steps.
Information to show or reference
- State capacitor Mvar per step.
- Show series reactor and valve.
- Reference switching logic.
A distinction that matters
A TSC switches capacitors in steps without transients; a mechanically switched capacitor uses a breaker and is much slower.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Static Var Compensators (SVC)
Public SVC page naming the thyristor-switched capacitor branch.
Capacitive component symbols
Public capacitor symbol family context.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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