THREE-PHASE POWER DISTURBANCE MONITOR

• US 3,813,667 A
• Filed: 05/29/1973
• Issued: 05/28/1974
• Est. Priority Date: 05/29/1973
• Status: Expired due to Term

• Current Assignee: Maurice N. Smith
• Original Assignee: Maurice N. Smith
• Inventors: Smith, Maurice N.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Myer, Daniel
• Application Number:
  US05/364,844
• Time in Patent Office: 364 Days
• Field of Search: 340/248 317/253,31 328/148
• US Class Current: 340/521
• CPC Class Codes: G01R 19/16547 voltage or current in AC supplies switching for protection H02H; circuits for emergency power supply H02J9/00

Abstract

A three-phase power disturbance monitor for sensing and recording anomalies occurring in electrical power systems which cause operational malfunctions in, and damage to, critical loads such as computers and synchronous communication equipment. The system senses and counts over and under voltage conditions, over and under frequency variations, and high or low threshold pulse transients. The monitor provides visual and audio warnings of power supply conditions which could damage equipment if left uncorrected for a period of time. The number of disturbances exceeding certain values is displayed on a digital counter. The monitor is equipped with a common input voltage section, a common 24 volt d.c. power supply and a front panel a.c. volt meter. Upper and lower threshold values for each condition are adjustable between certain limits determined from particular applications of the monitor. The audio and visual warning systems remain on if the disturbance continues to exceed a predetermined value for length of time. An external voltage feature has the capability of triggering a remote alarm system, powering down critical equipment and initiating the switching of critical loads to another power source.

Claims

1. A power disturbance monitor for detecting and indicating anomalies occurring in a source of electrical power comprising:

an input buffer circuit for measuring the power input and supplying rectified and filtered voltages to disturbance detection circuits;

a d.c. power supply connected to the rectified output of the input buffer for supplying power to the disturbance detection circuits;

means for connecting the power source to the input buffer circuit;

an overvoltage detection circuit receiving a rectified voltage from the input buffer for sensing voltage above a preset threshold;

an undervoltage detection circuit receiving a rectified voltage from the input buffer for sensing voltages below a preset threshold;

a frequency variation detection circuit connected to the input buffer for sensing frequency variations above and below preset thresholds;

a high pulse transient detection circuit receiving a filtered voltage from the input buffer for sensing pulse transients above a preset threshold level;

a low pulse transient detection circuit receiving a filtered voltage from the input buffer for sensing pulse transients below a preset threshold level;

a power disturbance readout circuit receiving the outputs of the power disturbance detection circuits for counting the number of each type of disturbance; and

an alarm indicating circuit receiving overvoltage, undervoltage, and frequency variation outputs from the power disturbance readout circuit for giving visual and audio alarms when a disturbance is detected by one or more of the circuits.

2. The power disturbance monitor of claim 1 wherein the input buffer includes:

means for connecting a three-phase power source to be monitored;

an a.c. voltmeter for measuring the input line voltage;

switching means for selecting any one of the three phases to be measured;

three transformers for isolating the detection circuits for the input power source, each transformer having one phase of the power source connected to its primary side; and

a capacitor and diode connected to the secondary of each transformer for providing a filtered and rectified output to the disturbance detection circuits.

3. The power disturbance monitor of claim 1 wherein the overvoltage and undervoltage detection circuits include:

an adjustable input attenuator;

a switch for selecting the threshold at which a voltage disturbance will be detected; and

a transistor switching and charging circUit adapted to provide an output by conducting at a predetermined voltage.

4. The power disturbance monitor of claim 3 wherein the threshold selector switch for the overvoltage is adapted to provide threshold selections of 120, 125, 130, 135 and 140 volts.

5. The power disturbance monitor of claim 3 wherein the threshold selector switch of the undervoltage detection circuit is adapted to provide threshold selections of 115, 110, 105, 100, 95 and 90 volts.

6. The power disturbance monitor of claim 1 wherein the frequency variation detection circuit includes:

an input attenuator;

means for differentiating the input;

a multi-vibrator for producing a squarewave connected to the output of the differentiating means;

means for selecting over frequency threshold level by adjusting the on time of the multi-vibrator;

means for selecting the under frequency threshold level by differentiating the output of the multi-vibrator;

means for inverting and amplifying the output of the under frequency threshold selecting means; and

means for comparing the output of the inverting means with a negative pulse from the differentiating means to prevent an output when the two signals are in coincidence; and

a transistor switching and charging circuit adapted to provide an output by conducting at a predetermined voltage.

7. The power disturbance monitor of claim 6 wherein the over frequency threshold level selecting means is comprised of:

a plurality of potentiometers for adjusting the on time of the multi-vibrator; and

a switch for selecting any one of the potentiometers thereby setting a particular threshold level for over frequency detection.

8. The power disturbance monitor of claim 7 wherein the means for selecting the under frequency threshold level is comprised of:

a capacitor;

a plurality of potentiometers;

a switch for selectively connecting any one of the potentiometers in series with the capacitor thereby setting the particular threshold level for under frequency detection.

9. The power disturbance monitor of claim 8 wherein the switch for setting the over frequency threshold level and under frequency threshold level are connected to simultaneously select the over frequency and under frequency settings.

10. The power disturbance monitor of claim 9 wherein the frequency variation circuit is adapted to select frequency ranges of 59-61, 58-62 or 57-63 Hertz.

11. The power disturbance monitor of claim 10 wherein the coincidence comparing means is comprised of:

two transistors having a common connection for their collectors and a common collection for their emitters.

12. The power disturbance monitor of claim 1 wherein the high and low pulse transient detection circuits are comprised of:

an adjustable input attenuator network;

a switch for selecting the threshold level at which a pulse transient will be detected; and

a phase splitter network for providing a positive pulse whenever a pulse transient occurs.

13. The power disturbance monitor of claim 12 wherein the high pulse transient detection circuit is adapted to provide threshold level settings of 300, 450 and 600 volts peak-to-peak.

14. The power disturbance monitor of claim 12 wherein the low pulse transient detection circuit is adapted to provide threshold level settings of 50, 100, 150 and 200 volts peak-to-peak.

15. The power disturbance monitor of claim 1 wherein the power disturbance readout circuit is comprised of:

a separate electro-mechanical counter associated with each power disturbance detection circuit respectively; and

a switching circuit associated with each counter and adapted to be energized by a power disturbance from the detection circuit with which it is associated, thereby causing the counter to advance one count.

16. The power disturbance monitor of claim 1 wherein the alarm indicating circuit is comprised of:

a separate indicating light associated with each of the overvoltage, undervoltage, and frequency variation detection circuits respectively;

a switching circuit associated with each light and adapted to be energized by a power disturbance from the detection circuit with which it is associated; and

a speaker adapted to be energized by any one of the switching circuits.

17. The power disturbance monitor of claim 16 further including:

a switch in the alarm indicating circuit for de-energizing the speaker.

18. The power disturbance monitor of claim 17 further including:

external terminals connected to the speaker for providing a remote alarm.

19. The power disturbance monitor of claim 1 further including:

a time and event register for recording the time and indicating the particular type of power disturbance which occurred.

20. The power disturbance monitor of claim 19 wherein the time and event register is comprised of:

a binary coded time clock; and

a printer connected to the output of the binary coded time clock.