gcsc seminar

1. GCSC - GTO THYRISTOR
CONTROLLED SERIES CAPACITOR
PRESENTED BY
LEO PAUL
CHITTILAPPILLY

2. INTRODUCTION
• Proposed by Karady & others in 1992.
• It consists of Fixed capacitor in parallel with anti parallel GTO
pair or valve.
• Thyristor valve has the capability to turn on and turn off
mechanism.
• Act as a dual of TCR.

3. BASIC SCHEME OF GCSC

4. • The GCSC controls the voltage across the capacitor (Vc) for a
given line current.
• when the GTO is closed the voltage across the capacitor is zero
• when the GTO is open the voltage across the capacitor is at its
maximum value
• The magnitude of the capacitor voltage can be varied continuously
by the method of delayed angle control
• For practical applications, the GCSC compensates either the
voltage or reactance

5. WORKING
• Closing and opening of valve is carried out in each half cycle in
synchronism with supply frequency.
• Turn off instant of each half cycle is controlled by a delay angle ᵞ
wrt peak of line current.
• Here ᵞ varies from 0 to 90 degrees.
• Line current i and Vc are shown for ᵞ =0 and at an arbitary value
of ᵞ

6. principle of turn-off delay angle control

7. • Variation of VCF is
normalized to maximum
voltage
• GCSC can be operated
in either to control
Voltage or reactance
• Fundamental
component of the series
capacitor voltage vs.
the turn-off delay angle
γ.

8. GCSC IN VOLTAGE COMPENSATING MODE
• GCSC can be operated either to compensate voltage or to compensate
Xc(ᵞ).
• In first case, GCSC is used to maintain the rated compensating voltage
in association with decrease of line current over an interval
I min ≤ I ≤I max
• n this case, Xc is selected in such a manner that Vc max/I min = Xc.
• When I is increased from I min to I max, ᵞ is also increased

9. GCSC IN REACTANCE COMPENSATING
MODE
• GCSC is used to maintain the max rated compensating reactance
at any line current up to max.
• In this case, Xc is selected in such a manner that
Vc max/I max = Xc.
• GCSC can be used to vary Xc from
0≤ Xc(ᵞ) ≤ Xc