Invalidity dossier
US 6185482
System and method for rms overcurrent backup function
Current assignee: ABB Inc USA
Added 9/23/2026, 4:47:02 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 6,185,482 B1
Title: System and method for rms overcurrent backup function
Patent number / application: US 6,185,482 B1; Application US 09/037,359
Inventors: Michael Egolf, David G. Hart, James D. Stoupis
Original assignee: ABB Power T&D Co Inc. Current assignee listed as ABB Inc USA.
Dates: Filed 1998-03-10; priority 1998-03-10; granted/published 2001-02-06; anticipated expiration 2018-03-10; status "Expired – Lifetime." An assignment to ABB Power T&D Company Inc. is listed 1998-06-29.
Purpose (plain language): The invention addresses fault detection in digital protection systems — for example a generator protection unit (GPU) — when the input voltage signals normally used for frequency tracking and phasor estimation become unavailable. The patent states that conventional systems use sensed voltage signals to generate phasor and frequency data for fault detection, so if none of the three phase voltage signals is available, the protection system cannot operate. The described backup function instead derives an overcurrent indication from current samples alone, and must work across a wide frequency range because generators operate over a wide frequency range, particularly during startup or shutdown.
Scope (as described in the supplied text): A method of overcurrent backup samples the current signal to produce current samples, generates a plurality of root mean square (rms) current values from those samples, generates a current estimate from the rms values, and activates a fault protection mechanism if the estimate exceeds a predetermined threshold. Sampling uses a predetermined fixed rate; the method determines whether frequency tracking is available and uses it if so. A sufficient number of measurements may be 32, with N = 32 samples per cycle; each successive rms value may use eight current samples collected after the previous value. The current estimate may be the average of four consecutive rms values. The threshold may be about 70% of the rated system value, and the protection mechanism may open a circuit breaker. An apparatus counterpart includes a current sensor, A/D converter, digital signal processor, and microprocessor.
Source: https://patents.google.com/patent/US6185482/en
Not established by this excerpt: the full claims and their exact scope; the complete description and drawings; detailed operation of the incorporated DFT/frequency-tracking application (Ser. No. 08/574,357); and any legal conclusions about validity, infringement, or prior art. The excerpt is partial.
Generated 10/1/2026, 9:44:12 PM
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