Method and apparatus for supervising an electrical line for short circuits
US4179651A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 22, 1977 |
| Grant date | Dec 18, 1979 |
| Priority date | — |
| Expiry date | Sep 22, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H7/265
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An arrangement for supervising an electrical line for short circuits in which current and voltage signals are derived from the line current and line voltage at a predetermined measuring point. The current and voltage signals are relatively weighted by multiplying at least one of these signals by a weighting factor which is at least approximately free of phase rotation. At least one auxiliary signal is formed corresponding to the sum or difference in each case of a pair of relatively weighted current and voltage signals. An amplitude comparison is carried out between the auxiliary signal and a reference signal. The weighting factor is related to the current signal and the voltage signal, and is a quantity at least approximately corresponding to the characteristic line resistance or its reciprocal value. Two auxiliary signals may be formed by addition and subtraction respectively of a pair of relatively weighted current and voltage signals, and one of these auxiliary signals is used, in the amplitude comparison, as a reference signal for the other.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.