The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 23, 1982
Filed:
Apr. 04, 1980
Richard A Vernier, Princeton, IN (US);
AMF Incorporated, White Plains, NY (US);
Abstract
An improved ground monitoring circuit for detecting the integrity and proper connection of the ground conductors in an electrical cable of an electrical power distribution system of a type that is commonly used at a surface mining site. A complete conductive loop is established between the ground conductor, or conductors, and the ground check, or pilot wire of the cable. A sensing signal at a frequency higher than the power frequency is coupled onto the ground monitoring loop. The monitoring loop includes a terminating resistor of predetermined value. The sensing signal on the ground conductor in the loop is isolated from local ground by means of an impedance element that presents a high impedance at the sensing signal but not at the power frequency. The impedance element is connected between the ground conductor of the power cable and the local ground. When successive lengths of cable are series connected, the impedance elements are connected in parallel with each other and are connected from an end of the ground conductor to the local earth ground, thereby to avoid series connections of the impedance elements in the ground conductors. The voltage and current in the loop are separately sampled. Various comparisons of the voltage and current samples are made to detect any deviation in the resistance of the loop. Any deviations from desired conditions in the loop produce an output signal that changes the condition of a trip relay. The trip relay initiates action that ultimately opens circuit breakers to remove power from the cable.