The analysis of the factors affecting the performance of Clamp Rogowski coil

Clamp Rogowski coil current transformer (CT) with strong anti-interference ability, high installation flexibility and operational safety, are now being widely used to detect the partial discharge (PD) of the XLPE (cross-linked polyethylene) cables, especially in the situation where the cables are in operation and therefore needed to be on-line monitored in practical applications. Since Clamp Rogowski coil CT can be easily mounted on the cables without changing the structure of the cable accessories, a large degree of flexibility and convenience can be expected when they are used in electrical industries. Compared with uncut Rogowski coil CT, the windings of Clamp Rogowski coil CT are concentrated in half side and thus introduce air gap on the grounds that the core has to be cut into two parts. In this paper, the amplitude-frequency characteristics of Clamp Rogowski coil CT and uncut Rogowski coil CT were measured and analyzed in detail. During the measurement, a sine wave current with constant amplitude was input from the primary side of the coil, and the voltage amplitudes output from the secondary side of the coil were recorded by changing the frequency of the current. The experimental data were summarized and drawn into amplitude-frequency curves using Matlab software package. The comparative analysis of the experimental results showed that, within the frequency band of XLPE cable PD detection (500kHz~10MHz), the difference in the output amplitudes of uniformly-winding and unevenly-winding Rogowski coil CT is less than 3.2%, while the difference between those of Rogowski coil CT and uncut Rogowski coil CT is less than 6%. It also shows that the influences of uneven winding and air gas on the amplitude-frequency characteristics of the transformer is very small after clamp Rogowski coil sensors have been used. The findings of this work may trigger some useful conceptions in the design of modern electronic transformer.