Research Of A Novel Rogowski Coil With Special Magnetic Core

Current transformer is one of the most important devices in power system. Its application get throughout the production, research and testing of the related power sectors in many areas. It is being regarded as important facility for electric energy measurement and relay protection in power system. Current Transformer's precision and reliability have close relation to the power system's security, reliability and economical operation. However, the disadvantages of traditional current transformers such as magnetic saturation and poor insulation are getting more and more apparent with the development of transmitting power capability and voltage gradation. Therefore, improving the related technical indicators of the Current Transformer makes a great practical value in ensuring stable and safe running of power system and its interrelated equipments.The transient current transformer in power system can be divided in iron-core current transformer with current output and air coil with voltage output according to its detecting principle. Through national and international research, we can know that traditional iron-core current transformer and air core have its own advantages, but the disadvantages are also exist and unavoidable because of the limitation of detecting principle. Traditional iron-core current transformers have been applied in power system to detecting and relay protection because of its advantages such as: high signal-to-noise ratio, high stabilization, etc. But meanwhile, its disadvantages are also been noticed in course of power system developing to high capability and high voltage gradation such as: narrow frequency band, magnetic saturation, etc. which will provoke the distortion of the second waveform of current transformers result in the fault-action and refusal-action of relay protection. Although the magnetic saturation problem result from non-periodic current can be solved by means of opening air-space in iron-core, the bulk will enlarge and the cost will increase because the iron-core must be design in big cubic content result from the existence of air-space in iron-core. The detecting frequency band is narrow because of the limitation of magnetic performance of iron-core material. Meanwhile, the output of traditional current transformer couldn't be connected with internet directly, which restrict its widespread usage in power system. Air coil have many advantages such as: no magnetic saturation problem, wide detecting frequency band, wide dynamic domain, small capacity, low cost, etc. It have been wide accepted in power system combine with modern electric technology, and it will be used more and more widespread with the power system developing to high capacity and high voltage gradation. But its disadvantages couldn't be neglected meanwhile such as: low output signals, low signal-to-noise, etc.This paper presents a novel Rogowski coil with special magnetic core. It contains the advantages of both current transformers with iron-core and air coil. It wouldn't have the problem of magnetic saturation in holding the advantages such as: high signal-to-noise, wide frequency band, wide dynamic domain, etc. which will solve the problems of fault-action and refusal-action of relay protection result from inaccurate detecting basically.According to Faraday effect principle, the secondary output of Rogowski coil is a differential relationship with primary current. So an integral circuit in the secondary side is needed. For the increase of magnetic iron particle ratio in the frame of the novel Rogowski coil, its magnetic permeability and signal-to-noise are properly increased. In the same condition, the secondary output is significantly enhanced compared to Rogowski Coil, and its frequency band is increased significantly also.The theoretical analysis and experimental proving show that this transducer gets a very wide frequency band measurement range after signal processing. From 10 Hz to 100k Hz and ampere to kiloampere, the measurement error of current can be assured within the framework of international standards.