Ground monitoring system and method
US4153923A · kind A · utility
Inventor
Key dates
| Filing date | Feb 15, 1977 |
| Grant date | May 8, 1979 |
| Priority date | — |
| Expiry date | Feb 15, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H11/001
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A system for monitoring the continuity of at least the ground wire of a cable connected between a mining machine and a power center. At the power center, a monitor signal is coupled to multi-phase power conductors of the cable through a multi-phase filter. The monitor signal from the conductors is coupled to the ground wire at the mining machine through another multi-phase filter. The signal returns through the ground wire to the power center where a current transformer couples the signal from the ground wire to a receiver. The receiver which receives and senses the characteristics of the returned signal includes parallel phase locked loop discriminators to prevent false tripping of the main power breaker if the monitor frequency should vary only slightly. The parallel discriminators provide a fail safe arrangement to prevent the main power breaker from remaining closed if one of the parallel discriminators should malfunction. A decrease in amplitude or change in frequency beyond a pre-selected range of the monitor signal at the receiver discontinues the receiver output so the main power breaker will open and cut off the A-C power to the mining machine.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.