Series compensation of radial power system by a combination of SSSC and dielectric capacitors

This paper shows that the addition of dielectric capacitors lowers the cost of series compensation by static synchronous series compensator (SSSC). Normally the capacitor resonates with the line inductance and the L-C electrical resonance can interact with the torsional resonances of the multiple-inertia elastic shaft of steam turbinegenerators to give rise to subsynchronous resonance (SSR) instability. The SSSC has two functions: (1) to provide some series capacitive reactance compensation; (2) to damp out incipient unstable SSR modes. Digital simulation using HYPERSIM shows that for an overall degree of capacitive compensation of 0.7 pu, the SSSC component is only about 1/3 of the capacitive Mvar. Based on the transient stability limit, the transmissibility of the line is increased by a factor of 2.23.