US 11,855,442 B2
Systems and methods of grounded neutral fault detection by single frequency excitation and leakage spectral analysis
John Paul Filipetti, Bloomfield, CT (US); Cecil Rivers, Jr., Bloomfield, CT (US); and Lucas James McPhee, Bloomfield, CT (US)
Assigned to ABB Schweiz AG, Baden (CH)
Filed by ABB Schweiz AG, Baden (CH)
Filed on Sep. 16, 2021, as Appl. No. 17/476,822.
Prior Publication US 2023/0090349 A1, Mar. 23, 2023
Int. Cl. G01R 31/52 (2020.01); H02H 3/33 (2006.01); H02H 3/16 (2006.01)
CPC H02H 3/331 (2013.01) [G01R 31/52 (2020.01); H02H 3/162 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A grounded neutral fault detector, comprising:
induction circuits configured to:
generate a leakage signal corresponding to a current imbalance between a line conductor and a neutral conductor for a load; and
a controller configured to:
determine a frequency of a test signal by:
measuring load noise based on a first leakage signal without the test signal being injected, the first leakage signal corresponding to a first current imbalance between the line conductor and the neutral conductor for the load when the test signal is not being injected into the neutral conductor;
analyzing a frequency spectrum of the load noise; and
selecting the frequency of the test signal based on the frequency spectrum of the load noise;
inject the test signal at the selected frequency to the neutral conductor;
measure impedance of a current loop formed by a potential grounded neutral fault based on a second leakage signal corresponding to a second current imbalance with the test signal being injected; and
determine a grounded neutral fault based on the measured impedance.