Signal attenuation and distortion in coaxial cables for high voltage measurements

Coaxial cables of about ten meters in length are commonly used in high voltage laboratories to interconnect high voltage lightning impulse dividers output to the digital recorder located in the control room. Common practice in testing laboratories is to check the characteristic impedance of the measuring coaxial cable to analyse if it is matched to the low voltage arm of the divider and to the measuring instrument. In addition, cable shielding must also be checked to proof immunity against interference signals, specially, when the disruptive a discharge occurs. Although it is not usual in testing to consider the signal attenuation caused by the measuring coaxial cable, it should be considered in calibration measurements or when the cable is too long (longer than 15 m). Effects caused by a measuring coaxial cable when a high voltage lightning impulse is measured can be determined by modelling.