Granted Patent
Utility
US 5,909,656 · App. 08/811,646
Protective relay with improved DFT function
Inventor:
Lifeng Yang
Patented Case
View Patent ↗
Granted: Jun 1, 1999
Filed: Mar 5, 1997
Inventor
Lifeng Yang
Assignee (at issue)
ABB Power T&D Company Inc.
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.