SIMULATIONS AND CALCULATIONS AS VERIFICATION TOOLS FOR DESIGN AND PERFORMANCE OF HIGH-VOLTAGE EQUIPMENT

SUMMARY Recognizing an increasing role of commercial modelling software in the power industry, Study Committee A3 decided to evaluate existing simulation technologies to determine the extent to which they can be used as verification tools to enhance understanding of equipment performance, to extrapolate test results, to provide an alternative to testing, or to replace some of the tests. WG A3.20 compiled an inventory of electrical, mechanical, thermal, magnetic, and other stresses which “A3-type” components (substation equipment except transformers) are subjected to in service, based on the relevant tests mandated by IEC/ANSI standards. For all investigated applications, WG A3.20 listed expected simulation results and the preferred numerical methods to be used for different specific problems. An assessment has been made to determine to what degree such stresses can be simulated. The purpose of the assessment is to analyse the accuracy of modelling the behaviour of a device under certain physical constraints as re-produced during the tests. This process is performed in two steps: 1. Stress calculation: the ability of the model to compute certain physical parameters such as temperature, electric and magnetic field, pressure etc. 2. Performance forecast: prediction of capability to withstand the stresses. It has been found to be much more difficult task, because models of physical failure processes like breakdown, burst, re-ignition, melting, rupture or explosion are generally not yet available, let alone software that would implement them. Instead, "design rules" based on practical experience and observations from tests are applied. Several examples of this assesment are presented in this paper. These include: • Application of electric field analysis to estimate the dielectric stresses and to predict the withstand voltages of HV equipment: A benchmark of dielectric simulation tools has been conducted by the WG. An experimental SF6 circuit breaker has been manufactured and subjected to high voltage tests specifically for this purpose. Based on the digital CAD files, the electric field was calculated by six major manufacturers. The analysis showed that different software tools predicted almost identical