Abb Power Td & Company

Abb Technology Ag

Robert A Smith

David G Hart

Damir Novosel

Yi Hu

William M Egolf

Graeme N McClure

Aftab H Khan

Jeffrey L McElray

Ian J Harvey

James E Smith

Carl LaPlace

A system and methods that enable a restoration scheme for power distribution systems that is independent of power distribution system component configuration, the number of power distribution system components, and component settings are provided. In a power distribution system, a number of intelligent reclosers having restoration control modules are deployed that execute a restoration scheme. The intelligent reclosers constantly poll cooperating power distribution lines to determine changes in current or voltage provided by the power distribution lines. In the event of a power distribution system fault, the reclosers act in accordance to a predefined restoration scheme to reanimate the unaffected portions of the failing power distribution system.

Loop restoration scheme for distribution feeders

A high sample rate cosine filter eliminates DC components by summing them such that they sum to zero. A non-orthogonal cosine filter is also provided. When the cosine filter is applied for N=4 samples per cycle, the samples are separated by 90 degrees. However, at higher sampling rates, it is not necessary to wait for 90 degrees to estimate the phasor value. Non-orthogonal components are used to estimate the phasor value. The time delay associated with the cosine filter is reduced in the process.

Modified cosine filters

An electromagnetic actuator and an automatic recloser incorporating such actuator are disclosed. The actuator is shown to include a housing, a permanent magnet member, a coil, an armature, mounted to move axially within the housing between first and second positions, and a non-magnetic spacer. The armature, when in the second position, is spaced a distance from the housing by the spacer. The spacer is mounted to stop movement of the armature in the second position. In the preferred embodiment, the permanent magnet member includes a core and a number of magnet segments attached thereto. It is especially preferred for each of the permanent magnet segments to be arcuate shaped and that each segment be polarized substantially radially or in a direction parallel to the center radius of each segment. In a preferred embodiment, the housing is formed from a material having a high permeability and the spacer is formed from material having a relative permeability close to one or from a substantially non-magnetic material, such as acetal resin. The circuit recloser is shown to include the bistable magnetic actuator, a contact switch, a connecting member, connected between the actuator the contact switch and a spring, connected to bias the connecting member in relation to the contact switch. When the actuator is in its second position the end of the connecting member is spaced from the end of the contact switch, i.e., over travel is present. An indicator is provided for indicating whether the contact switch is open or closed.

Molded pole automatic circuit recloser with bistable electromagnetic

A system for implementing accurate V/Hz value measurement and trip time determination for generator/transformer overexcitation protection independent of the conventional frequency tracking and phasor estimation based on Discrete Fourier Transformation (DFT) techniques. The half-cycle summation technique of the invention is a non-recursive digital technique which measures the per unit V/Hz value by summing the sampled data points in every half cycle of a sinusoidal input signal and dividing the sum with the ideal base sum value. When the input voltage signal is sampled at a reasonable frequency, the technique of the invention approximates the accurate per unit V/Hz value of the input voltage signal and thus obtains an accurate V/Hz characteristic directly without computing voltage and frequency separately.

Half-cycle summation V/Hz relay for generator and transformer

A method and system for estimating phasors and tracking the frequency of a signal is provided. The method uses a variable N-point DFT to compute one or more phasors based on data acquired from one or more sampled signals. At each sampling interval the change in phasor angle between the current sampling interval and the previous sampling interval is determined and used to estimate the instantaneous frequency of the signal. Instantaneous frequencies are averaged over a cycle of the signal. In addition, a number of discrete frequencies and corresponding DFT windows based on a fixed sampling rate and a predetermined fundamental frequency of the signal are defined and used in estimating the instantaneous frequency. Once the average cycle frequency is determined the DFT window is adjusted by setting it equal to the DFT window corresponding to the discrete frequency closest to the average cycle frequency.

System and method for phasor estimation and frequency tracking in

A system for implementing accurate V/Hz value measurement and trip time determination for generator/transformer overexcitation protection independent of the conventional frequency tracking and phasor estimation based on Discrete Fourier Transformation (DFT) techniques. A sampled sinusoidal voltage signal is passed through a digital integrator and the magnitude of the digital integrator's output is measured as representative of the V/Hz ratio. The digital integrator is implemented in software using a difference equation in a generator protection unit. The technique may be used with either a fixed or a variable sampling frequency. When the sampling frequency is variable, the filter coefficients of the digital integrator are recalculated on-line each time the sampling frequency is changed, and a new value for the peak magnitude of the output of the digital integrator is calculated using the recalculated filter coefficients. Non-linear frequency response characteristics of the voltage sensors and non-ideal characteristics of the digital integrator are also adjusted using the measured frequency and error-frequency characteristics of the particular digital integrator and voltage sensors used.

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Cary, NC, United States of America

Robert A Smith