Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Reexamination Certificate
2000-12-07
2004-02-17
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
C361S020000, C361S023000, C361S044000
Reexamination Certificate
active
06693778
ABSTRACT:
BACKGROUND OF THE INVENTION
Existing Ground Fault Detection (GFD) systems for brushless exciters rely on simple circuit designs generally operating by being powered directly from the circuit upon which they are trying to make measurements. Their simplicity makes them poor measurement devices, susceptible to variations in field voltages. Those units are also prone to false trips even when adjusted by the best technician using his best guess. Those GFD systems can only operate when power is supplied to the rotor windings and therefore cannot indicate an existing fault prior to start-up. Start-up during ground fault conditions may be disastrous.
Existing Diode Fault Detection (DFD) systems are also simple monitors generally relying upon the interpretation of a wave shape to guess a diode failure has happened somewhere in the system.
No known systems combine a ground fault detection system with a diode fault detection system. Diode and ground fault conditions have been a concern for years.
Ground fault and diode fault detection systems are needed to protect generators and motors from major breakdowns from ground faults, with attendant destruction of expensive equipment and loss of capacity during replacement or repair.
Needs exist for improved diode fault and ground fault protection systems.
SUMMARY OF THE INVENTION
The present invention is unique in its components, its non-contact measurement, its ground fault system independence from the field voltages, its ability to identify the location of the ground fault, its electronic diode fault system, and its ability to monitor both functions.
The GFD System is unique in its construction and operation. An induced power supply allows operation before start up and without power being supplied to the rotor windings. It also uses a non-contact data transmission for electrical isolation. The GFD System operation is independent from the field voltages, and provides a method to measure and inform the user of insulation resistance condition and the fault location regardless of motor or generator operational conditions.
The DFD System identifies the specific failed diode or diodes that has triggered an alarm, for ease of replacement.
The present invention provides systems that detect ground faults and detect diode faults. More particularly, the present invention provides systems that detect ground faults and detect diode faults in large generators and motors.
The present invention is a telemetry system for detecting diode faults and detecting ground faults in generators or motors. An objective of the invention is to provide a complete system, using unique low power transmitters, ground fault interface modules, diode fault interface modules to detect either ground faults, diode faults or both. Additionally the system provides reliable alarm signals of lights and/or electrical control signals.
The new Ground Fault Detection and Diode Fault Detection (GFD/DFD) Systems have rotating and stationary component assemblies. The rotating assembly has four interface modules, which are normally encapsulated, in a specially configured support ring. The GFD/DFD Systems support ring assembly is bolted to the brushless exciter. The brushless exciter is attached to a generator or motor. The GFD/DFD System support ring is provided power by an induction loop antenna attached to a stationary Induction Power Supply (IPS). A Receiver Control Unit provides power to the IPS and receives and conditions the RF (radio frequencies) data transmitted from the GFD/DFD System support ring assembly.
These units together provide the means to detect ground faults, to detect diode faults, and to activate alarm lights and electrical control signals for normal and faulty operating conditions.
REFERENCES:
patent: 4403218 (1983-09-01), Beal et al.
patent: 4556946 (1985-12-01), Taniguti
patent: 4714917 (1987-12-01), Counter et al.
patent: 4812751 (1989-03-01), Roberts et al.
patent: 4864242 (1989-09-01), Hurley
patent: 5508620 (1996-04-01), Pfiffner
patent: 5557216 (1996-09-01), Dailey et al.
patent: 5691643 (1997-11-01), Ishiguro et al.
Pittman Wayne A.
Swartz David P.
Creighton Wray James
Jackson Stephen W.
Narasimhan Meera P.
Sensotec, Inc.
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