Study On On-line Monitoring Of Capacitive Equipment In Intelligent Substation

The safe and reliable operation of the equipment in substation is the foundation for thethe fast development of national economy, and electrical equipment accidents are mostlycaused by the damage of insulation.the equipments’ insulating can be reflected properties bythe tangent value of dielectric loss angle tanδ, therefore the the power system can be welloperated as long as we get the the dielectric loss angle tanδ precisely by the onlinemonitoring.The theory of current situation in capacitive equipments’ insulation on-line monitoring inintelligent substations as well as the significance of the dielectric loss on-line monitoring andthe factors that influence measurement accuracy are disserted in the thesis.A system by usingintelligent electronic device which is based on IEC61850communication protocol canachieve the capacitive equipments’dielectric loss on-line monitoring in intelligent substationsand this system abides by the ideas of the national intelligent power grid strategic thought andthe requirements of intelligent substation’s development. The main works are as follows:Aiming at requirements of the capacitive equipments’ insulation on-line monitoring inintelligent substations, the high-accuracy monitoring methods of tanδ，the filtering algorithmof on-line monitoring data and the fault diagnosis algorithm are studied deeply;ICAalgorithmbased on windowed harmonics analysis algorithm and independent variables are put forward;the application of intelligent electronic devices in intelligent substations and the achievementof IEC61850communication protocol are introduce in detail. Based on the study of keytechnology, a system of on-line monitoring of dielectric loss in capacitive equipments inintelligent substations is design.The System of on-line monitoring of dielectric loss in capacitive equipments inintelligent substation is mainly consisted of site monitoring terminals，intelligent electronicdevice and backend server.Site monitoring terminals is designed by FPGA and DSP andsensors, signal amplification circuit, filter circuit, digital signal processing circuit isincluded. Adopting nickel-cadmium, sensors accomplish real-time collecting the screen leakcurrent of capacitive equipments and reference voltage signal. Signal amplification circuit andfilter circuit accomplish the front-end processing of analog signal, and then accomplishmeasuring signal frequency as well as A/D conversion. System adopts two completely samechannels,signal collection, processing, conversion circuit, accomplishes synchronoussampling of signal in different places through B code synchronous clock; Samplingconversion sequence is controled through the programmable logical component and the requirement in both sampling rate and accuracy can be meet well in dielectric loss on-linemonitoring. The capacitive equipment IED is designed by ARM and DSP and main worksinclude accomplishing command issue, computing the data that collected, uploadingprocessed data to server following IEC61850communication protocol. The IED’s realizationof IEC61850protocol, not only accomplishes the requirement of on-line monitoring ofdielectric loss in capacitive equipments, but also meets the requirement of information sharingin intelligent substation, which improve the system reliability as well as reduce repeatedinvestment and maintaining cost at the same time.The results have been runned successflly in ningxia substation and realized the insulationonline monitoring of capacitive equipment such as current transformer and transformerbushing,The leakage current,dielectric loss,capacitive current and equivalent capacitance aremeasured accurately. The analysis of the monitoring data show that the design works stablyand the precision meets on-line monitoring requirements.