带量程扩展器的工频感应分流器的原理与应用

Principle and Application of Range Extended Inductive Current Dividers

准确度通常高于0.001级工频电流比较仪用于检定0.01级的标准TA,其一、二次部分均为分段串并联结构,变换一个电流比需要改动多个连接片。因电流比相当多,检定时换接线工作量大,容易出错。而工频感应分流器准确度可以达到10-6量级,只要选择适当的抽头就能得到所需的电流比,可以大大减轻检定工作量。如果用零磁通TA作为量程扩展器就可覆盖TA的全部量程,与电流比较仪共同检定精密TA。

Current comparators are widely used in calibration of current transformers. In its application, a great number of connecting sheets are wanted for each range. The reconnection could easily cause errors. An inductive current divider is also in high accuracy ratio standard but rarely used in current transformer calibration for its poor ranges. To cascade zero-flux current transformers the measuring rang of inductive current divider can be largely extended. In an actual application there is a 50A inductive current divider in 12 segments, which offers ratios from 5/ 5 to 60/5. When it is cascade with a 500A/50A zero-flux current transformer, ratios from 60/5 to 600/5 are obtained. Meanwhile, when the 50A inductive current divider is cascade with a 5000A/50A zero-flux current transformer, ratios from 600/5 to 5000/5 are obtained. The 50A inductive current dividers in 12 segments can be calibrated by a reference current method without other current standards. The reference current is supplled by a 50A/SA （60A/SA） zero-flux current transformer. By experiments the ratio uncertainty is less than 0. 2 ×10^6. 500A/50A zero-flux current transformer can be calibrated by comparing with 50A inductive current divider, and 5000A/50A zero-flux current transformer can be calibrated by comparing with 50A inductive current divider in cascade with 500A/ 50A zero-flux current transformer. By experiments the ratio tmcertainty is less than 1 N 10-6. It is feasible that the extended inductive current dMders serve as ratio standards in current transformer calibration together with current comparators.