Real load unbalance protection system for parallel variable speed constant frequency electrical power systems
AssigneeWestinghouse Electrical Corp.
InventorsMirza A. Beg, Donal E. Baker
Life of this patent
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Abstract
A method for sensing real load unbalance in an electrical power system having at least two clock based power sources which are connected for parallel operation combines a real load difference current signal, proportional to the difference in real load currents in corresponding phases of the power sources, with a phase angle signal which is proportional to the phase difference between an external clock signal and an internal clock signal of one of the power sources, to produce an error signal. When this error signal exceeds a predetermined threshold level, a trip signal is produced to indicate that an excessive real load unbalance situation exists.
Claims5
A real load unbalance sensing and protection circuit for an electric power system in which at least two clock based power sources are connected for parallel operation, said circuit comprising:
- means for producing a real load difference current signal proportional to the difference in real load currents of the power sources;
- means for producing a phase angle signal proportional to the phase difference between an external clock signal and an internal clock signal of a first one of said power sources;
- means for combining said real load difference current signal and said phase angle signal to produce an error signal;
- and
- means for producing a trip signal when said error signal exceeds a preselected threshold level.
A method of sensing real load unbalance in an electrical system having at least two clock based power sources which are connected for parallel operation, said method comprising the steps of:
- producing a real load difference current signal proportional to the difference in real load currents of the power sources;
- producing a phase angle signal proportional to the phase difference between an external clock signal and an internal clock signal of a first one of said power sources;
- combining said real load difference current signal and said phase angle signal to produce an error signal;
- and
- producing a trip signal when said error signal exceeds a preselected threshold level.
Dependencies are inferred from the claim text.