Planar Rogowski Coil Current Transducer Used for Three-phase Plate-form Busbars

For measuring current in three-phase plate-form busbars, this paper proposed an indirect method that used planar Rogowski coil as the current sensing part. Based on the electromagnetic induction law, Biot-Savart law and the numerical integration arithmetic, the vector potential of the busbar was calculated and the Electromotive force of the planar coil for the single phase and three-phase busbar current was deduced. The relative error that was caused by vertical displacement, flat displacement and rotated displacement of coil is measured and calculated when the coil is used for the measurement of plate-form busbar current. The results of the theoretical calculation about the coil have good accordance with the experiments. More than two years of field testing shows that the current transducers based on the planar Rogowski coil proposed by this paper meets the practicality.

I. INTRUDUCTION

Plate-form busbar conductors are commonly used in many electrical power distribution equipments, such as high voltage switchgear, et al. Due to the narrowly measuring range, the inductive current transformers manifest magnetic saturation phenomena and waveform distortion in the secondary side, and can't measure heavy current accurately. The closed loop Rogowski coil current transducer can eliminate the magnetic saturation phenomena in the measurement of heavy current, but the closed loop structure transducer can't install conveniencely in the field of fixed current loop. Magnetic field transducer, however, to measure the magnetic field at a point near the conductor, can be used to measure the current indirectly. There are many magnetic field transducers, such as transducers based on electric optical effect [1]–[3], Hall effect[4]–[6], and magnetoresistive effect[7], et al. For improving the accuracy of the measurement, magnetic transducer circular arrays can be used, the sensing elements are assembled on a circle around the conductor[4]–[7]. But the structure of these transducers are complex and can't install easily in the field test.