Patents by Inventor John R Nightall

John R Nightall has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Apparatus for and method of monitoring an earth-leakage state of a power distribution system
    Patent number: 5990685
    Abstract: An earth-leakage monitoring method for a power distribution system, and in particular a DC 4-rail traction system, incorporating a pair of current-conductors (current rails) and an earth reference (a pair of running rails or an earthing system), comprises measuring the conductor-to-earth voltage for each conductor; forming a ratio of these voltages; connecting a known resistance between one conductor and earth; re-measuring the two conductor-to-earth voltages; forming a new voltage ratio, and calculating the value of leakage resistance existing between each conductor and earth using the known resistance value and the two voltage ratios.
    Type: Grant
    Filed: September 5, 1997
    Date of Patent: November 23, 1999
    Assignee: Cegelec Controls Limited
    Inventor: John R Nightall