Reasereh On Insulator Leakage Current Detection Of High Accuracy And Data Compression For Transmission Lines

Insulator leakage current detection of high accuracy is a fundamental and key link to know the operating state of an insulator well and exactly. Efficient data compression on its leakage current signal is an important means to guarantee the real-time performance of an insulator state monitoring system. The research relating to this dissertation is focused on the above these two issues.Through analyzing the error sources of leakage current transducers in details, we can obtain the following conclusions:(1) an excitation current brings the steady-state error;(2) the local magnetic hysteresis and parameters change of broadband transducer circuit causes the transient error, which is just neglected in current error compensation methods. The existing zero-flux error compensation method can't meet the requirements for a leakage current transducer of broadband, wide range and high accuracy.To meet for the requirements of a leakage current transducer on high accurate and broadband charactistics, micro-flux-variation dynamic error compensation method is proposed in this dissertation. Its error compensation model is studied theortically. The mathematical analysis to its transient micro-flux-variation characteristics in the compensation process is presented, and the basic calculation methods of steady-state error and transient error are given. With micro-flux-variation error compensation mathematical model, the influence to the proposed transducer by the exciting current, hysteresis and broadband signal is discussed deeply.A design scheme of Rogowski leakage current transducer of broadband and high accuracy with iron core is proposed based on the micro-flux-variation error compensation method. Experiments with four kinds of situations are carried out on the developed transducer. Results show the transducer has higher accuracy and better linearity within the given amplitude range and frequency band, and has a very good transient response to a transient current signal.To solve numerous problems resulting from the different gaps of the clamped-on leakage current transducers in their field installation, and the temperature drift of electronic circuits, an online calibrating method is put forward based on given current injection. The principle, calibrating process and experimental results of this method is stated in details.It is diffcult to achieve high resolution under wide-range for a measurement with current technology. To solve this problem, a wide-range and multi-resolution measuring method of the leakage current is proposed based on Schmitt trigger. The control strategies on the output grade switching is designed. The validity of this method is verified through experiments.Considering the non-stationary and periodic characteristics of leakage current data, a combinatorial method on their compression is put forward based on predictive coding and adaptive SPIHT. Experiments show that the method has distinct advantages in compression performance and calculation speed.The developed leakage current transducer has been applied to high voltage transmission line monitoring. Results show that it can meet the requirements of high accurate detection on the insulator leakage current.