Automatic transfer control device and frequency monitor

• US 4,231,029 A
• Filed: 02/28/1978
• Issued: 10/28/1980
• Est. Priority Date: 02/28/1978
• Status: Expired due to Term

• Current Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Johnston, Paul M.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Myer, Daniel
• Application Number:
  US05/881,926
• Time in Patent Office: 973 Days
• Field of Search: 340/658, 340/171 R, 361/182, 328/138, 235/92 FQ, 307/129, 307/64, 307/65, 307/86, 307/87, 324/78 D, 324/78 Q, 324/78 Z, 324/186
• US Class Current: 340/658
• CPC Class Codes: G01R 23/15 Indicating that frequency of pulses is either above or below a predetermined value or within or outside a predetermined range of values, by making use of non-linear or digital elements (indicating that pulse width is above or below a certain limit)
• CPC Class Codes: H02H 3/46 responsive to frequency deviations
• CPC Class Codes: H02H 7/266 involving switching on a spare supply in general H02J9/00
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: Y02B 70/30 Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
• CPC Class Codes: Y04S 20/20 End-user application control systems

Abstract

An automatic transfer control device for generating signals to cause associated circuit interrupters to selectively energize an electrical distribution system from either of a pair of electrical power sources. The device includes an over- and under-frequency monitoring circuit to determine if the power source frequency is within preset limits. The frequency monitoring circuit includes a zero-crossing detector which activates a clock oscillator, the output pulses of which are accumulated by a counter for one half cycle. The number of pulses occurring during the half cycle is compared with a limit value stored in a read-only memory. An alarm signal is activated if the number of pulses accumulated is out of limits. The address inputs of the read-only memory are connected to the alarm signal generator and to a flip-flop toggled by the zero-crossing detector so that any of four limit values are selectively accessed for input to the comparator: high limit, low limit, return-to-normal after high alarm, and return-to-normal after low alarm. A strobe circuit is provided to only momentarily energize the read-only memory, thereby reducing power consumption.

Claims

1. Apparatus for monitoring the frequency of an alternating current power source, comprising:

means for measuring the frequency of said source during each cycle;

means having an address input and a data output for storing a plurality of limit values;

means connected to said measuring means and said storage means for comparing measured and stored values;

means connected to said comparing means for generating an alarm signal when a measured value falls outside a limit value;

and means connected to said storage means for selecting alternate limit values to present to said comparing means on alternate cycles, whereby alternate testing functions are performed on alternate cycles.

2. Apparatus as recited in claim 1 comprising a latch means for storing alarm signals, and means for selecting alternate limit values for presentation to said comparing means depending on whether or not an alarm signal is stored in said latch means.

3. Apparatus as recited in claim 2 wherein said storage means contains a "high limit" value, a "low limit" value, a "return to normal after over frequency alarm" value, and a "return to normal after under frequency alarm" value;

said limit value selecting means comprising a flip-flop connected to said power source and means for toggling said flip-flop on each power souce cycle to alternately select a "high limit" value or a "low limit" value; and

said alarm limit selecting means input is connected to said flip-flop and to said latch means so that a stored over frequency alarm in said latch means causes said alarm limit select means to select said "return to normal after over frequency alarm" value for presentation to said comparing means when said flip-flop is calling for a "high limit" value, and a stored under frequency alarm in said latch means causes said alarm limit select means to select said "return to normal after under frequency alarm" value for presentation to said comparing means when said flip-flop is calling for a "low limit" value.

4. Apparatus as recited in claim 3 wherein said alarm limit select means comprises first, second, and third two-input NAND gates;

the output of said first gate being connected to said storage means address input, the outputs of said second and third gates being connected to the inputs of said first gate, one input of said second and third gates being connected to said flip-flop, and the other input of said second and third gates being connected to said latch means.

5. Apparatus for monitoring the frequency of an alternating current power source, comprising:

an oscillator;

a counter connected to said oscillator for generating binary representations of the number of output pulses of said oscillator;

means responsive to said power source for activating said oscillator for a predetermined number of cycles of said power source, whereby said counter accumulates a number of pulses inversely proportional to frequency of said power source;

memory means for storing a binary representation of a pulse count corresponding to a frequency limit value;

means connected to said counter and said memory means for comparing the binary representation accumulated by said counter with said binary representation stored in said memory means; and

means for generating an alarm signal whenever the binary representation of said counter falls outside of said limit value binary representation.

6. Apparatus as recited in claim 5 wherein said memory means comprises means for storing a plurality of binary representation of pulse counts corresponding to frequency limit values, and said apparatus comprises means to selectively address said memory means to present any of said plurality of binary representations to said comparator means, whereby any of a plurality of frequency checking functions are selectively performed.

7. Apparatus as recited in claim 6 wherein said selective addressing means are connected to said alarm generating means and are operable to vary the binary representations addressed according to the presence or absence of a previously generated alarm signal.

8. Apparatus for monitoring the frequency of an alternating current power source, comprising:

means for producing a test value proportional to time;

synchronizing means connected to said test value producing means and responsive to the output of said power source for operating said test value producing means for a predetermined number of cycles of said power source;

memory means for storing a reference value proportional to permissible frequency limits;

comparator means for comparing said test value and said reference value, said comparator means producing an alarm signal when said test value is outside of the limits defined by said reference value;

means connected to the power source and said memory means for momentarily supplying operating energy to said memory; and

means for latching the output of said memory means and for supplying the output of said memory means to said comparator means.

9. Apparatus as recited in claim 8 comprising energy storage means connected to said energy supply means and said memory for storing an amount of energy sufficient to allow said memory to operate for a period of time after said energy supply means are deactivated.

10. Apparatus as recited in claim 9 wherein said energy storage means comprises a capacitor.

11. Apparatus for monitoring the frequency of an alternating current power source, comprising:

means for producing a test value proportional to time;

synchronizing means connected to said test value producing means and responsive to the output of said power source for operating said test value producing means for a predetermined number of cycles of said power source output;

memory means comprising a plurality of data value storage locations for storing a plurality of reference values proportional to permissible frequency limits each corresponding to a specific function to be performed by said apparatus;

comparator means for comparing said test value and one of said reference values; and

means to selectively present one of said references values to said comparator means;

said comparator means producing an alarm signal when said test value is outside of the limits defined by said reference value.

12. Apparatus as recited in claim 11 wherein:

said synchronizing means comprises a zero-crossing detector;

said memory means comprises address input and data outputs;

said presenting means comprises means connected to said zero-crossing detector and said address inputs for supplying alternate inputs signals to said address inputs upon alternate source voltage cycles, and means connected to said address inputs and said comparator means for supplying either of two signals to said address inputs dependent upon whether or not said comparator means have generated an alarm signal, whereby a selected one of said plurality of reference values appears at said memory data outputs.