Apparatus providing on-line indication of frequency of an AC electric power system
US6519537B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | May 9, 2000 |
| Grant date | Feb 11, 2003 |
| Priority date | — |
| Expiry date | May 9, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R23/02
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Apparatus for determining the frequency of an ac power signal, includes sensing circuitry to sense the ac signal. In a digital implementation of the invention, a double average of the samples is generated by a processor as the sum of the most recent sample, twice the next most recent sample plus the third most recent sample. The least mean square of a running window of the most recent double average signals is generated to avoid discontinuities at the zero crossings and to reduce the effects of noise. The frequency is determined from this least mean square value of the window of double average signals. As implemented in a protective relay, a trip signal is generated if the frequency is out of limits.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.