Research on mechanical fault diagnoses methodology of a circuit breaker based on the voltage and current during its operation
The performance of a circuit breaker during its operation has great impact to the power system security and is of great concern to the operation and management department of power grid. This paper presents a new method to acquire the performance information of the circuit breaker during its connecting/disconnecting operation through the voltage and current waveforms‥ Due to capacitance effects between dynamic and static contact, the voltage and current parameters in the process of connecting/disconnecting can be decomposed into two parts by orthogonal transformation method. The two parts are active and reactive power. The reactive component is generated by the capacitance effects. When the circuit breaker mechanical failure, particularly in velocity of contact anomalies, the capacitance effects will naturally be affected, that is, the reactive component will contain abnormal part inevitably. This method can effectively suppress interference, highlight the major characteristic quantities of the circuit breaker, and evaluate its mechanical performance.
Fault Diagnosis for High Voltage Circuit Breakers With Improved Characteristic Entropy of Wavelet Packet
Based on the introduction of wavelet packet and characteristic entropy,a new method to diagnosis fault for high voltage circuit breakers is presented,and its steps and analysis are also introduced. The method combines the strongpoint of wavelet packet and characteristic entropy. Firstly,vibration after clearing up noise is wp-decomposed at the third level,and the eight signals of each junction at the third level are reconstructed; Secondly,the vector is extracted with the segmental energy of reconstructed signals based on the theory of entropy; and lastly the classification of characteristic parameter is realized with simple BP neural network for fault diagnosis. The experimentation without loads indicates the method can easily and accurately diagnose breaker faults,and exploit a new road for fault diagnosis of HV circuit breakers.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).