Apparatus for reducing subsynchronous frequencies in a power supply
First Claim
1. In a power transmission system comprising a turbine-driven multiphase synchronous generator for supplying power signals at a predetermined rated frequency to a transmission line network by means of a multiphase block transformer, wherein at least one of said generator and said transformer includes a secondary winding having a plurality of phase windings, the high-voltage terminals of which are respectively connected to respective transmission lines of said network, and further including a line of shafts connecting the turbine to the generator that exhibit one or more natural frequencies lower than said rated frequency, a system for protecting said line of shafts from damage due to oscillations at said natural frequencies, comprising:
- a plurality of damping resistors directly and separately connecting the low voltage terminals of said phase windings to a neutral potential terminal; and
a series resonant circuit tuned to said predetermined rated frequency connected in parallel with each of said damping resistors whereby said damping resistors have negligible effect on signals at said predetermined rated frequency and are effective to damp out signals at frequencies other than said predetermined rated frequency.
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Abstract
A protective circuit for reducing subsynchronous natural resonant frequency signals in a multiphase power supply system includes a damping resistor connected in series with each phase winding of the system. A resonant circuit tuned to the rated line frequency of the system is connected in parallel with each resistor so that signals having frequencies other than the rated line frequency will be damped by the resistors. An inductor can also be placed in parallel with each resistor to maximize the damping effect of each resistor at predetermined subsynchronous frequencies.
57 Citations
9 Claims
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1. In a power transmission system comprising a turbine-driven multiphase synchronous generator for supplying power signals at a predetermined rated frequency to a transmission line network by means of a multiphase block transformer, wherein at least one of said generator and said transformer includes a secondary winding having a plurality of phase windings, the high-voltage terminals of which are respectively connected to respective transmission lines of said network, and further including a line of shafts connecting the turbine to the generator that exhibit one or more natural frequencies lower than said rated frequency, a system for protecting said line of shafts from damage due to oscillations at said natural frequencies, comprising:
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a plurality of damping resistors directly and separately connecting the low voltage terminals of said phase windings to a neutral potential terminal; and a series resonant circuit tuned to said predetermined rated frequency connected in parallel with each of said damping resistors whereby said damping resistors have negligible effect on signals at said predetermined rated frequency and are effective to damp out signals at frequencies other than said predetermined rated frequency. - View Dependent Claims (2, 3, 6, 7, 8, 9)
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- 4. The power transmission system of cliam 1 wherein said resonant circuit comprise a series connection of an inductor and a capacitor.
Specification