The Flexible Optical Current Transformer Runs Successfully

The flexible optical current transformer (CT) operates steadily at Datang Guanyinyan hydro-power station in Yunan province and Guoxin power plant in Jiangsu province, marking successful application of this kind of CT in the large-scale hydro-power and thermal power units for the first time.

The CT is an essential element for electric system. Its core role is to measure the current or voltage, and provide accurate measurement value of primary current and voltage for secondary protection and control equipment. Measurement precision, transient characteristics, stability and anti-interference are important indicators to evaluate the quality of CT. As the voltage grade of electric system rises and the transmission capacity improves, some disadvantages of traditional CT become remarkable, such as hard to insulate, easy to saturate, bad transient performance and large volume etc.

The core equipment of this CT adopts full optical structure and can correctly transmit DC component, fundamental component and high harmonic wave. One coil can measure hundreds of thousands of current. The instantaneous error of transient current falls below 10%, which effectively improves the precision of harmonic wave control and capability of anti-electromagnetic interference. This kind of CT is suitable to promote and use in different industries. Also, it can quickly check and locate underground cable faults.

Soft sensing fiber-optics and flexible bend are made full use of to produce sensing rings in cable forms in order to overcome problems, such as small unit, large volume and heavy weight of CT. Those can be installed around conductors with any form and the weight can reduce above 90%. It is easy to install and maintain, and has strong  adaptability. Meanwhile, when installing the sensing fiber ring, it is allowable that the original primary circuit is not off for increasing measuring points in the system temporarily or forever. That is especially suitable for the upgrading of substations and power plants.