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MPSC Assistant Engineer EE Mains 2019 - Paper 1

Option 4 : a high impedance

CT 1: Engineering Mathematics

1077

10 Questions
10 Marks
12 Mins

__TCSC (Thyristor controlled series capacitor):__

- A TCSC is a series-controlled capacitive reactance that can provide continuous control of power on the ac line over a wide range.
- TCSC consists of a series compensating capacitor (C) shunted by a thyristor controlled reactor (TCR).
- TCR is a variable inductive reactor (XL) tuned at firing angle α.

Figure: Equivalent circuit of TCSC

The variation of X_{L} with respect to α can be given as \({{\rm{X}}_{\rm{L}}}\left( α \right) = {{\rm{X}}_{\rm{L}}}\frac{\pi }{{\pi - 2α - \sin 2α }}\)

- For the variation of α from 0 to 90, XL(α) varies from actual reactance (XL) to infinity.
- This controlled reactor is connected across the series capacitor so that the variable capacitive reactance is possible across the TCSC which modifies the transmission line impedance.

Reactance characteristic curve:

- It is drawn between the effective reactance of TCSC and firing angle α.
- The effective reactance XTCSC(α) of TCSC operates in three regions, inductive region, capacitive region, and resonance region.
- The inductive region starts increasing from TCR reactance XL||XC value to infinity and decreasing from infinity to capacitive reactance XC for the capacitive region.
- Between the two regions, resonance occurs (Parallel resonance) when XL(α) = XC. In this region due to parallel resonance, the parallel combination of TCR and capacitor will act as an open circuit and offers very high impedance to the network.