Remotely-controllable relays and filters therefor
AssigneeEnertec
InventorAnthony J. Ley
Life of this patent
Estimating the term…
Abstract
A remotely-controllable relay which is controlled by 175 Hz ripple voltage superimposed on the mains supply voltage in an electric-power distribution network contains an oscillator generating a signal at 173 Hz. This is mixed with the network voltage so that, when ripple voltage is present, a beat note at a frequency of 2 to 3 Hz is generated. This beat note is separated from the unwanted signals, such as the mains supply voltage, by a third order active low-pass filter to control operation of the relay. A similar technique provides simplified detection of output signals from correlation-type filters.
Claims21
A remotely-controllable relay for effecting a switching operation in response to a control signal in the form of an alternating ripple voltage at a first predetermined frequency superimposed upon and asynchronous with an alternating power supply voltage in an electric-power distribution network, comprising:
- an input for receiving the network voltage and supplying a signal derived therefrom;
- means for generating a signal at a second predetermined frequency independent of the power supply frequency and selected to be different from the nominal value of said first frequency and further selected such that the difference frequency of the first and second frequencies is less than any of the first, second and power supply frequencies;
- means connected for receiving and mixing said second-frequency signal and said signal supplied by the input, whereby to produce an output signal including, if said control signal is present on the network, a component at the difference frequency;
- filter means connected to receive the output signal of the mixing means, and arranged to pass said difference frequency and to attenuate higher frequencies;
- and
- means connected to the filter means to detect the presence of said component and to effect said switching operation in accordance therewith.
A remotely-controllable relay for effecting a switching operation in response to a control signal in the form of an alternating ripple voltage at a first predetermined frequency superimposed upon and asynchronous with an alternating power supply voltage in an electric-power distribution network, comprising:
- an input for receiving the network voltage and supplying a signal derived therefrom;
- means for generating a signal at a second predetermined frequency independent of the power supply frequency and selected to be different from the nominal value of said first frequency and further selected such that the difference frequency of the first and second frequencies is less than any of the first, second and power supply frequencies;
- means connected for receiving and mixing said second-frequency signal and said signal supplied by the input, whereby to produce an output signal including, if said control signal is present on the network, a component at the difference frequency;
- filter means connected to receive the output signal of the mixing means, and arranged to pass said difference frequency and to attenuate higher frequencies;
- means connected to the filter means to detect the presence of said component and to effect said switching operation in accordance therewith, and wherein said relay further includes:
- means for generating first and second correlation signals at said first predetermined frequency and in phase quadrature with one another, wherein said mixing means is arranged to effect tuned filtering at said first predetermined frequency and comprises first and second multiplying means connected to receive and multiply said signal supplied by the input with said first and second correlation signals respectively;
- first and second low-pass filters connected to receive the outputs from said first and second multiplying means respectively;
- and
- third multiplying means connected to receive and multiply the outputs from said first and second low-pass filters respectively by first and second multiplying factors dependent on said generated first and second frequency signals and in the same phase relationship as said first and second correlation signals.
Dependencies are inferred from the claim text.