Design And Research Of On-load Tap Changer Operation Condition Monitoring And Management System

On-Load Tap Changer(OLTC)is an important component of power transformer.It plays an important role in stabilizing the central load voltage,increasing the flexibility of power grid regulation and effectively improving the power quality of power grid.Its operation state has an impact on the safe operation of the transformer.In order to effectively obtain the operation status and fault information of OLTC,this thesis designs an OLTC monitoring and management system based on OLTC working parameters to monitor the operation status of OLTC scientifically and systematically.It mainly obtains the fault information in OLTC vibration signal through wavelet analysis,pre judges the fault,puts forward reasonable equipment operation and maintenance suggestions according to the equipment working conditions,and realizes the life cycle management of OLTC equipment.The system can effectively eliminate the hidden trouble of OLTC and prevent the occurrence of faults,which is of great significance to the safe operation of power transformer and distribution network.In order to intuitively monitor the operation status of OLTC and subsequent parameter analysis,this thesis first designs an OLTC monitoring and management system based on SCADA system,which is composed of "lower computer upper computer".Through program and script editing,a unified MODBUS-RTU communication protocol is established,and the OLTC working parameters are sent to all levels of display terminals to realize the communication between devices.Because the OLTC working parameters contain rich OLTC operation status information,the OLTC working parameter acquisition system is built.Through DSP /CCS platform,the working parameters of OLTC are collected by connecting vibration and temperature sensors,the vibration signals under normal OLTC,contact burning and contact loosening conditions are obtained,and the over temperature alarm is realized.The results show that the vibration signal of OLTC is closely related to its mechanical characteristics,and the vibration signal waveform is different between different working conditions and different gear switching.In order to obtain and quantify the equipment state information of OLTC vibration signal,an analysis method combining discrete wavelet and wavelet packet energy is proposed in this thesis.The occurrence time nodes of contact burning and loosening faults are obtained by discrete wavelet analysis,the fault severity is quantified by calculating the wavelet packet energy transformation ratio,and the OLTC vibration signal information is extracted.The results show that OLTC has medium contact burning failure and serious contact loosening failure.The contact burning and loosening faults can be distinguished according to the large number of vibration signal pulses of contact loosening fault and the obvious signal mutation characteristics of contact burning fault detail signal.Finally,this thesis designs an expert database OLTC fault diagnosis system based on VB language.The system uses wavelet analysis to obtain the fault variation ratio and characteristics of OLTC vibration signal,and compares it with the sample database information in the system to realize fault diagnosis and prediction.According to the causes and hazards of faults,reasonable operation and maintenance suggestions are put forward.At the same time,the processed fault information and maintenance information are entered into the system to form a complete OLTC expert database fault diagnosis system,which realizes the life cycle management of OLTC.