Air clearance calculation under consideration of atmospheric, statistic and geometric influences for HVDC converter stations based on normative procedures

Summary

Two major technologies are under operation in today's High Voltage Direct Current (HVDC) market. These are on the one hand line commutated converters (LCC) and on the other hand voltage source converters (VSC). Both technologies differ from their basic capability regarding power reversal and fault handling. Moreover, fault handling is influenced by the converter design. It can be summarized that the highest transient voltages are occurring during fault scenarios. The resulting overvoltages are mostly impulse voltages and are depending on the fault handling strategy. Further to insulation for general operation conditions, the insulation needs to withstand those fault scenarios to ensure a safe and reliable energy transmission. According to these influences a standardized way for insulation coordination, as it is established for alternating current (AC) applications, is more demanding for HVDC applications. Installation locations are varying and atmospheric influences differ in a wide range. It's well known that the disruptive strength of air is affected by several parameters such as occurring humidity, air pressure and temperature. Further influences are the general statistic behaviour of disruptive discharges and geometric parameters such as electrode design or minimum discharge path. All of these aspects have to be taken into account for dimensioning of air clearances. This paper presents a method which enables the calculation of indoor air clearances for HVDC converter stations for the purpose of insulation coordination based on simulated or calculated impulse (withstand) voltages. Atmospheric influences, statistical and geometric parameters are considered within this calculation method. Mostly normative procedures which are mentioned within several AC or test standards are used to promote method acceptability.

Additional informations

Authors

Kluge Michael, Schultz Niko, Rüdinger Bernd