Transient interaction between coupling capacitors voltage transformers and transmission lines

Coupling capacitor voltage transformers (CCVT) are widely used in power systems and the failure of this equipment may result unexpected outages of transmission lines (TL). This study shows that switching-off shunt reactor compensated TL may lead to sustained voltage amplification in the secondary of the CCVT, the product of a transient interaction between the TL and CCVT, which causes thermal and dielectric stress to its components. This interaction is chiefly influenced by the design of the CCVT and the TL-compensation degree, as assessed by means of frequency response mappings, measurements of several parameters of different designs of CCVT, and computer simulations. Besides, this investigation presents proposals to minimize damages in the CCVT and shows digital records of the Companhia Hidro Eleacutetrica do Satildeo Francisco (CHESF) transmission systems, which illustrate the existence of such a phenomenon.