A new type of micro current measurement device for dielectric response diagnosis

Summary

There is a high demand for micro-current measurement in the field of high voltage electrical equipment diagnosis, and it offers a promising possibility for nondestructive insulation estimation with several kinds of dielectric response methods such as the return voltage method (RVM), polarization and depolarization current (PDC) and frequency domain spectroscopy (FDS). However, the dielectric response measurement requires a high-precision circuit, which can meet the requirements of field with complex electromagnetic interference. Ultra low bias current amplifiers are commonly used in micro current measurements to complete I-V transformation. However, the feedback resistance of the amplifier circuit is large. The test process is easily disturbed by external power frequency and electromagnetic noise in the form of radiation. In this paper, the principle of feedback resistance method in micro current test is analyzed. At the same time, this paper analyzes the effect of the error caused by the amplifier and circuit on the test results. On the basis of error analysis, a novel current test topology is proposed, which can effectively suppress the power frequency interference and temperature drift of chip. Through the introduction of differential architecture, the purpose of low power frequency content and high accuracy current measurement under limited component accuracy is achieved. Experimental results show that test results of the proposed circuit having high linearity in the current range of 10-7A to 10-10A. Additional current testing results using a FDS test system which contains proposed circuit are also given, which reveals the stability of the designed micro-current measurement device.

Additional informations

Authors

STENKVIST, ELSNER, Li, PROVOOST, AESCHLIMANN, TRIPP, KEIL

Keywords

Micro-current signal measurement, dielectric response test, interference suppression