Research On Fault Detection Method Of Dry-type Air-core Reactor Based On High Frequency Sweep Method

As an important primary equipment,reactor plays an irreplaceable role in power system.Once it fails,it will pose a major threat to the safety of power system.At present,the defect detection of air core reactor is limited to physical detection methods such as turn-to-turn defect detection and infrared temperature measurement,which can only be used as a basis for fault analysis when a turn-to-turn short circuit or a large scale fault occurs in the reactor,and cannot guarantee timely warning before a fault occurs in the air core reactor.To address this problem,the thesis proposes a fault warning method for dry-type air-core reactor based on high frequency sweep method,which makes use of the sensitivity of capacitance parameter changes at high frequencies to assess the operational status of reactor windings by detecting the changes in reactor capacitance parameters.Firstly,the equivalence distribution circuit is constructed according to the structural characteristics of the dry hollow reactor in the high frequency domain,and the theoretical derivation of the parameters of the distribution equivalence circuit is carried out one by one,mainly including the calculation of the stray capacitance to ground,the inter-turn capacitance,the inter-layer capacitance,the self-inductance and mutual inductance of the winding coils,and the composite resistance of the conductor resistance and eddy current losses at high frequencies.Secondly,a programming method for the calculation of the nodal voltage of the high frequency distributed equivalent circuit of dry hollow reactors based on the nodal numbering method is proposed to achieve the analysis of the internal electrical quantity relationship of any envelope layer reactor at high frequencies.It is found that at low frequencies,the reactor voltage drop is uniformly distributed;at high frequencies,the reactor voltage drop is distributed according to capacitance,with the main voltage drop concentrated in the first end impedance section;while in the resonance region the reactor first end current frequency response curve has a significant wave peak,when the first end current is sensitive to changes in capacitance parameters,allowing the detection of parameter changes.Then,the modeling simulation with and without local water ingress is carried out for a specific type of reactor to simulate the capacitance parameter variation,and based on the simulation results,the required sweep range and the best measurement end for capacitance parameter detection are determined.Finally,an improved frequency response curve diagnosis method based on the idea of frequency banding is proposed based on the characteristics of the frequency response curve of reactors at high frequencies.By comparing with the traditional diagnostic indexes,it is found that the improved algorithm is significantly more sensitive in detecting the high frequency frequency response curve of the reactor.The RC model is then built to carry out practical experiments to verify the feasibility of the method and the reliability of the results in this thesis.