Purpose/Aim
Overhead transmission lines are easily disturbed by the overvoltages, which endangers the insulation performance of transmission lines. The overhead transmission line overvoltage measurement system based on the voltage divider has good accuracy. However, the long-term access of the voltage divider to the gird is easy to brings potential dangers to the power system. Therefore, it is necessary to use the non-contact, accurate, and real-time overvoltage measurement system to monitor the overvoltages of the overhead transmission lines.
Experimental/Modeling methods
In order to measure such as the lighting overvoltage and the transient overvoltage accurately, a non-contact overvoltage sensor was designed. The measuring principle of the sensor is capacitor dividing. The overhead transmission line and the sensor plate constitute the capacitance of the high voltage arm. And the low voltage arm is chip capacitors mounted to the PCB board. The real-time acquisition and long-distance transmission of the overvoltage waveform were realized by using the data acquisition card based on FPGA. The bandwidth of the sensor was calibrated. Using this system, the transient overvoltage of the transmission line was measured and transmission synchronously.
Results/discussion
According to the calibration results, the bandwidth of the non-contact on-line overvoltage measurement system was from 8 Hz to 80 MHz. The result of measuring the transient overvoltage showed that the characteristic of the transient overvoltage can be measured accurately. And the waveform can be transmitted remotely.
Conclusions
The non-contact on-line overvoltage measurement system can synchronously realize overvoltage waveform acquisition and remote waveform transmission. The non-contact overvoltage sensor of this system has a broad bandwidth, which is suitable for measuring lighting overvoltage and transient overvoltage. Furthermore, the use of a non-contact sensor and the data acquisition card based on FPGA makes the installation of the system convenient and has the ability of on-line monitoring.
 

overvoltage,overhead transmission line,on-line measurement,frequency bandwidth,sensor