A Compact High-Precision Guarded Volt Box

A new high-precision guarded volt box providing output voltages of 1.5 V for all input voltage ranges up to a maximum of 1500 V with ranges selected by a single rotary switch for tap changing is described. The design, test results, field experience, as well as the effects of voltage ratio errors, resistance value drift with time, self-heating errors, leakage errors, rod resistance, and temperature coefficients are discussed.