Research of error influence mechanism of CVT by electric field

Abstract

The capacitor voltage transformer running on the grid must carry out error detection within a fixed time according to the requirements of JJG 1021 《Instrument Transformer in Power System》 verification regulation. When CVT conducts offline error detection, there is no other running equipment around. However, when the CVT is connected to the grid for operation, there are electric field effects produced by metal supports, lightning arresters and other grounding and electrified bodies around. There are differences in the environment between offline error detection and online operation status. Firstly, the paper analyzes the characteristics of the intermediate voltage change of the capacitor cell of CVT under the influence of high voltage under the condition of grid connected operation. Secondly, the equivalent model simulation model is established to analyze the quantitative impact of the electric field generated by these objects on the CVT error. These objects include metal supports, lightning arresters and multiple CVTs. Finally, the verification test of the influence of external electric field on CVT error is carried out. The test results show that the external electric field will cause the CVT ratio difference to shift in the negative direction, and the influence degree will be in the thousandth place, and the influence amount will become smaller with the increase of the distance between it and the surrounding objects. The conclusion of this paper provides technical support for the off-line error detection of CVT and the correction of additional errors caused by external electric field.