Computer Aided Design of Synthetic Test Circuits for High Voltage Circuit-Breakers

Developments in electrical power transmission systems require the use of circuit-breakers with increasing breaking capacity. To test these equipments, direct testing is no longer feasible. This means that synthetic tests are necessary. These tests require circuits with a response specified by ANSI, IEC, ..., standards. Specific software has been created to permit automatic synthesis and optimum design of these circuits. This tool is used at the High Power Test Laboratories LEP of Electricite de France at Les Renardieres. In the paper, three different high voltage circuits are considered (fig. 1, 2, 3). They enable to provide ANSI and IEC (2, 4-parameter) transient recovery voltages (TRV). In view of the method by which the standards define the parameters of the transient recovery voltage it is quite impossible to analytically link these parameters with the value of the components of the test circuit. A digital computation is necessary to determine the parameters of the TRV corresponding to a given test circuit. Laplace transformation is used to determine the response of the circuit. Moreover an iterative process is required to establish the synthesis of the proposed circuit. Iterative formulae, which make the process converge at a satisfactory speed, have been developed. As a general rule, with the usual shapes of TRV and requiring an accuracy of 1 % on the parameters, the solution is obtained after approximately twenty iterations, taking 30 seconds on a HP 1000 computer.