83. Transient Interaction between Coupling Capacitors Voltage Transformers and Transmission Lines
Coupling capacitor voltage transformers (CCVT) are widely used in power systems and failure of this equipment may cause unexpected outages of transmission lines (TL). This study demonstrates that switching-off compensated TL may lead to sustained voltage amplification in secondary of the CCVT, 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 in this work by the means of frequency response mappings, measurements of important parameters of different designs of CCVT, and computer simulations. Besides, this investigation presents proposals to minimize damages in the CCVT and shows oscillographic records of the transmission systems of the Companhia Hidro Elétrica do São Francisco (CHESF), which illustrates the existence of such a phenomenon.