All-fiber optical current transformer (FOCT) based on Magneto-optical Faraday effect plays a pivotal role in current metering and protection of smart grid. However, the fault diagnosis of FOCT is one of the most critical issues to be solved. In order to ensure the proper functioning of FOCT, a fault diagnosis system is presented by monitoring the intensity variation of the light interference with Square wave bias modulation of FOCT, which is measured by digital signal processing unit using correlation detection technology. Afterwards, the faulty types of FOCT are recognized by the amount of the optical power variation. The experimental results show that the system can effectively detect these kinds of fault types, such as the broken of optical fiber, the increasing loss of optical fiber and the breakdown of light source in FOCT.
The development of power grid has put forward higher requirements on the performance of current sensors. Traditional current sensors already can not meet these needs of grid metering and protection. This paper proposes a fiber-optic current sensor (FOCS) based on fuzzy PI control strategy which combines fuzzy control with PI control. These parameters of fuzzy PI controller can be adjusted online at different stages of the system response. Simulation results show that the FOCS based on fuzzy PI control has a fast dynamic response and no overshoot, compared with FOCS based on traditional PI control. These advantages of accuracy in metering and rapidity in protection of power grid, can be satisfied simultaneously.
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