Surge measurement errors of coaxial cables

NEARLY ALL surge or impulse voltage measurements involve the use of a cathode ray oscillograph (CRO) and measuring cable. All cables have a certain amount of attenuation and their surge impedance is never the same for all frequencies as indicated in several studies. In low-voltage impulse work (where very short cables can be used) such factors may be negligible under certain conditions, but for measuring high-voltage surges, a fairly long cable (50 feet or longer) is usually required and possible errors caused by the cable should be considered, especially for measuring steeply rising surges. The purpose of this paper is to discuss such errors and devise method for measuring and minimizing them.