Design of a modular wideband high-voltage divider for metrological purposes with a greenhouse friendly isolation gas

Summary

A new modular wideband HVDC divider for calibration purposes has been designed and developed at the Physikalisch-Technische Bundesanstalt (PTB). Since the typical insulation gases of high voltage dividers have a bad environmental impact, one of the research issues of the PTB is the reduction of emissions. Especially in the case of a new development the use of SF6 needs to be avoided whenever possible. This paper introduces the design of a modular wideband high-voltage divider for metrological purposes with a greenhouse friendly insulation gas. Each of the four modules has a nominal voltage of 400 kV and an expanded measurement uncertainty of less than 10 ppm resulting in an overall expanded uncertainty below 100 ppm and a nominal voltage of 1.6 MV. The divider is equipped with a shield arm to ensure homogeneous electrical field around the precision arm. The shield arm consists of reliable high ohmic resistors combined with pulse rated metalized polypropylene capacitors. The precision divider contains thin film resistors which are combined in matched pairs of five to achieve a maximum temperature coefficient of not more than 2 ppm/°C. Parallel to the precision resistors capacitors are arranged to measure higher frequencies and transients. The insulation gas in use is a combination of dodecafluoro-2-methylpentan-3-1 with carbon dioxide as a carrier gas to guarantee its dielectric strength at low pressure. The insulation gas was compared to other gases including sulfur-hexafluoride and nitrogen using the sphere gap method. The results indicate higher insulation properties at pressures between 1 and 2 bar compared with sulfur-hexafluoride. Additionally, the insulation gas prevents partial discharges to ensure good linear behaviour. This research will lead to a new divider for voltages up to 1.6 MV at lowest uncertainty level including a greenhouse friendly gas.

Additional informations

Authors

Sun, HEINRICH, MATERN, KLOSINSKI, HEMDAN, HILBERT, KURRAT, WATT

Keywords

HVDC, isolation gas, metrology, precision divider