36results about "Form factor measurements" patented technology

Provided are methods and apparatus for characterizing a power waveform. Some such methods include sampling the power waveform to generate a plurality of samples and, for each of the samples, recursively processing the sample to generate an aggregate signal energy value, processing the sample to generate a harmonic component signal energy value associated with at least one target harmonic frequency, and accumulating the aggregate signal energy value and the component signal energy value with previously generated aggregate signal energy values and component signal energy values to generate an accumulated aggregate signal energy value and an accumulated harmonic component signal energy value. Methods also include characterizing the power waveform responsive to the accumulated aggregate signal energy value and the accumulated harmonic component signal energy value.

Embodiments of the present invention provide systems, devices and methods for efficiently calculating a true RMS values (either voltage or current) of an AC signal. The RMS value is generated from both high and low frequency components of the AC signal without a high speed ADC being integrated within the system. The high frequency component is processed by calculating an average current waveform of the high frequency component and approximating a corresponding RMS value using a waveform factor. The waveform factor is effectively a scalar that relates the average current waveform of the high frequency component to an appropriate RMS value.

The invention discloses a method for recognizing magnetizing rush current of a transformer based on dynamic quadrangle shape analysis. The method specifically comprises the steps of acquiring differential current waveforms of current mutual inductors at two differential protection sides of the transformer, and sampling; dividing the current waveforms into two parts according to the equal area condition; gradually moving the sampling points in the two waveform parts and forming a quadrangle set; determining the shape of each quadrangle; counting the proportion of parallelogram in the quadrangle set; determining whether the type of the current waveform is the type of magnetizing rush current or internal fault current according to the proportion. With the adoption of the method for recognizing magnetizing rush current of the transformer based on dynamic quadrangle shape analysis, the magnetizing rush current of the transformer can be effectively and reliably recognized, and thus the influence of local deformation of the sampled waveforms on the determining result can be effectively avoided.

A current transformer saturation detection method based on the third-order central moment. Firstly, the secondary side current of the current transformer is sampled; secondly, the data window is used to intercept the current waveform again near the peak value of the waveform, and the sampling points symmetrical about the peak value are obtained. Waveform; after the waveform image transformation is performed on the intercepted waveform, the discrete coefficient is calculated with the third-order central moment; finally, the judgment result is output. In this process, it is necessary to calculate the discrete coefficient after mirroring of the standard sinusoidal current waveform, which can be regarded as a fixed value through analysis and calculation as a basis for comparison. The invention focuses on solving the problems of slow detection rate and low detection accuracy when the current transformer is saturated, and can quickly and accurately detect the occurrence of CT saturation by only using the sampling data of half a cycle, which improves the reliability of relay protection to a certain extent. Reliability has certain practical significance in ensuring its accurate and reliable action.

The invention relates to a lightning stroke fault recognition method for an EHV (extra-high voltage) DC transmission line based energy spectrum similarity, and belongs to the technical field of power system relay protection. The method comprises the steps: extracting the ratio of a positive time domain waveform to an area formed by the enclosing of the zero axis of the positive time domain waveform and the ratio of a positive time domain waveform of any fault type to the area formed by the enclosing of the zero axis of the positive time domain waveform during stable operation when the voltage of the EHV DC transmission line fluctuates, and recognizing the fault and lightning stroke interference according to the ratios; switching to fault classification recognition if the interference is a fault, carrying out the wavelet decomposition recognition of an additional component through wavelet, and judging whether the fault is a grounding fault or a lightning stroke fault; and switching to a shielding failure and back flashover fault recognition if the fault is the lightning stroke fault. The method achieves the time frequency analysis of the simulation data, achieves the extraction of data in a short time period, and integrates area ratios, energy spectrum similarity and modular maximum value. The method achieves the extraction of a set of criteria for thunder interference, grounding faults, back flashover faults and shielding failures, and can achieve the accurate, quick and effective recognition of various types of conditions.