Edward P Hudson

US Patent:

40217299, May 3, 1977

Filed:

Dec 3, 1975

Appl. No.:

5/637233

Inventors:

Edward C. Hudson - Derry NH

Assignee:

I-T-E Imperial Corporation - Spring House PA

International Classification:

G01R 3102
G01R 1916

US Classification:

324 51

Abstract:

A differential transformer having a core of low permeability ferromagnetic material, a pair of identical primary windings and a secondary winding of relatively few turns capable of producing a large voltage output for a small magnitude ground fault current. A cross-field winding is utilized to periodically saturate a portion of the flux path in the transformer core to produce sudden changes in magnetic flux, which flux changes vary in magnitude proportional to the amount of fault current. During the time interval when the cross-field portion of the sensor is not saturated by a pulse of sampling current, a second pulse of current is introduced into the sensor secondary winding for detecting a grounded neutral wire by sensing the output voltage produced in response thereto.