Research On Electronic Travelling Wave Current Transformer Based On Rogowski Coil

The sensor head of existing Electronic Current Transformer mainly used the low cut-off frequency outside integrator, so it can not pass traveling wave signal. Data acquisition circuit by mainly low-speed microcontroller controlled A/D conversion can only get low-frequency signals, but not provide more than 1MHz traveling wave signal which traveling wave fault location needs. If applying traveling wave fault location technology at digital substation, we must first solve two problems of traveling wave transmission in the electronic current transformers and extracting traveling wave signal from the electronic current transformers.To describe the Rogowski coil for sensing principle and establishes a transfer function model. The paper makes in-depth study about connections Rogowski coil electromagnetic parameters with high frequency transition properties and time-domain properties. The results show that the cut-off frequency of the Rogowski coil can reach hundreds MHz if reducing the resistance and distributed capacitance under keeping self-inductance certain as possible as. Rogowski coils can meet bandwidth requirements of high-frequency traveling wave signal and have a fast response speed so as to measure the traveling Wave. To design an active analog integrator circuit with more than 1MHz cut-off frequency. To carry on simulation about Traveling Wave Transfer characteristics of Rogowski coil with integral circuit through fault transient traveling wave signals. The simulation results show that the Rogowski coil can transfer high-frequency traveling wave signal.To raise an act on adding a high-speed data acquisition channel in the electronic current transformers to extract traveling wave signals, without affecting to collect the original low-frequency signal.This paper use the high number of integrated CPLD control high-speed ADC as a data collector. ADC have analog input bandwidth of 700MHz,and sampling frequency up to 130MHz, the bandwidth meets requirements to the traveling wave. CPLD solve the problems of high-speed data acquisition and storage which the microcontroller can not solve because of low-speed. CPLD can control ADC to carry on high-frequency simultaneous sampling, therefore ADC can successfully get traveling wave signal from electronic current transformer.Electronic traveling wave Current Transformer is bound to promote the development of new fault locating algorithm matching with digital traveling wave signals, and offers a new development direction for traveling wave fault locating technology. It also will promote the electronic traveling wave current transformer applications at digital substation, and will bring new development opportunities for electronic transformer industry.