Method and apparatus for controlling loads in electric power systems by reduction of peak loads

• US 4,135,101 A
• Filed: 07/08/1977
• Issued: 01/16/1979
• Est. Priority Date: 07/08/1977
• Status: Expired due to Term

• Current Assignee: Arthur Laudel Jr, Gleen S. Young
• Original Assignee: Power Monitors, Inc.
• Inventors: Laudel, Arthur Jr., Young, Glenn S.
• Primary Examiner(s): Schaefer, Robert K.
• Assistant Examiner(s): Ginsburg, Morris
• Application Number:
  US05/813,816
• Time in Patent Office: 557 Days
• Field of Search: 307/117, 307/30, 307/34, 307/35, 307/38, 307/39, 307/62, 307/140, 307/3, 307/41, 307/40, 307/51, 324/103 R, 324/103 P, 324/113, 200/56 R, 200/56 A, 340/310 A
• US Class Current: 307/39
• CPC Class Codes: H02J 2310/60 Limiting power consumption in the network or in one section of the network, e.g. load shedding or peak shaving
• CPC Class Codes: H02J 3/14 by switching loads on to, or off from, network, e.g. progressively balanced loading
• CPC Class Codes: Y02B 70/3225 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y04S 20/222 Demand response systems, e.g. load shedding, peak shaving

Abstract

This invention discloses a load management system for reducing the peak load in an electrical power distribution network. This invention monitors, records and reduces the peak load present in an electrical distribution network by deferring power service from and cycling power service to preselected transformer loads during periods of peak power demand. The peak load control function of the present invention is controlled by a power monitor which is located at the distribution transformer. The power monitor measures the ambient temperature and the power load on an associated distribution transformer and initiates the peak load control function whenever the product of the temperature factor and the measured load rises above a preset control point. Initiation of the peak load control function completely defers power service from a first group of low priority loads and activates a timing and switching mechanism which cycles power service among selected groups of controlled loads in a preselected order. As the peak load decreases, the peak load control function is terminated and full service is returned to all of the transformer loads. The point at which the control operation is initiated is a function of the maximum magnitude of the uncontrolled load and is automatically set and retained to provide a control point at which the peak load control function will be initiated in the future.

Claims

1. A load management system for reducing the load in an electrical power distribution network having at least one remotely located distribution transformer that is capable of supplying electrical power to at least one associated transformer load by means of at least one alternating current distribution line, said system comprising:

power monitor means for monitoring the power load on said distribution transformer, said power monitor means comprising a current transformer means for measuring current flow within said alternating current distribution line, said current transformer means being operable to produce a secondary current which is related to the measured current flow and transducer means for converting said secondary current into a reading representation of the load on said distribution transformer, said transducer means being comprised of a bimetal spiral coil, said bimetal spiral coil being electrically coupled with said current transformer means such that said secondary current is caused to flow through said coil to vary the temperature of said coil in accordance with the magnitude of said secondary current, said bimetal spiral coil having one end rigidly anchored and the other end free to move in accordance with the temperature of said coil to provide said reading representation of the load on said distribution transformer;

first switch means for producing an activation signal whenever said reading is above a preset control point; and

means for reducing the power load on said distribution transformer in response to said activation signal.

2. The invention in claim 1 including means for displaying said reading.

3. The invention in claim 1 including means for adjusting said control point as a function of the reduced transformer power load, said adjusting means being operable to change said control point each time the reduced transformer power load reaches a new maximum value, said control point being a function of the magnitude of the reduced transformer power load.

4. The invention of claim 3, including means for displaying the value of said control point.

5. The invention in claim 3 including means for resetting said control point to a preselected value.

6. The invention in claim 5 wherein said resetting means includes means for activating said resetting means from an external locaton.

7. The invention in claim 1 including means for measuring the power demand of said transformer load, said demand measuring means being operable to record the peak demand over a set period of time.

8. The invention in claim 1 including means for measuring the power demand of said transformer load, said demand measuring means being operable to record the average demand over a set period of time.

9. The invention of claim 1 including means for producing said activation signal from a remote location independent of the power load on said distribution transformer.

10. The invention in claim 9 wherein said means for producing said activation signal from a remote location is comprised of:

signal generator means for generating a control signal;

means for transmitting said control signal throughout said electrical power distribution network; and

receiver means for detecting said control signal, said receiver means being operable to generate said activation signal in response to said control signal.

11. The invention in claim 10 wherein said signal generator means includes a frequency encoder means for providing numerous individually coded control signals.

12. The invention in claim 1 wherein said means for reducing the transformer power load is comprised of means for completely interrupting electrical service to said transformer load in response to said activation signal.

13. The invention in claim 12 wherein said means for completely interrupting electrical service is comprised of:

means for generating an interrupt signal in response to said activation signal;

means for interrupting electrical service to said transformer load in response to said interrupt signal; and

means for operably coupling said generating means and said electrical service interrupting means.

14. The invention in claim 12 wherein said means for completely interrupting electrical service is comprised of:

signal generator means for generating an interrupt signal in response to said activation signal;

means for injecting said interrupt signal into said at least one alternating current distribution line; and

receiver means for detecting the presence of said interrupt signal on said distribution line and for interrupting electrical service to said at least one transformer load in response to said interrupt signal.

15. The invention in claim 14 wherein said injecting means is comprised of an injection transformer located at said one distribution line, said injection transformer having a primary coil for accepting said interrupt signal from said signal generator means and a secondary coil comprised of said one distribution line, said primary coil being coupled with said signal generator means so as to circulate the 60Hz current present in said distribution line.

16. The invention in claim 14 wherein said signal generator means includes a frequency encoder means for providing numerous individually coded control signals.

17. The invention in claim 1 wherein said means for reducing the transformer power load is comprised of means for intermittently interrupting electrical service to said at least one transformer load in response to said activation signal.

18. The invention of claim 17 wherein said means for intermittently interrupting electrical service is comprised of:

timing and switching means for intermittently generating an interrupt signal in response to said activation signal;

means for interrupting electrical service to said at least one transformer load in response to said interrupt signal; and

means for operably coupling said generating means and said electrical service interrupting means.

19. The invention of claim 18 including means for producing said activation signal from a remote location independent of the power load on said distribution transformer.

20. The invention of claim 19 wherein said remote activating means includes means for varying the timing and switching sequence of said timing and switching means from said remote location.

21. The invention in claim 17 wherein said means for intermittently interrupting electrical service is comprised of:

timing and switching means for intermittently generating a timing signal in response to said activation signal;

signal generator means for generating an interrupt signal in response to said timing signal;

means for injecting said interrupt signal into said at least one alternating current distribution line; and

receiver means for detecting the presence of an interrupt signal on said distribution line and for interrupting electrical service to said at least one transformer load in response to said interrupt signal.

22. The invention in claim 21 wherein said injecting means is comprised of an injection transformer located at said at least one distribution line, said injection transformer having a primary coil for accepting said interrupt signal from said signal generator means and a secondary coil comprised of said one distribution line, said primary coil being coupled with said signal generator means so as to circulate the 60Hz current present in said distribution line.

23. The invention in claim 21 wherein said signal generator means includes a frequency encoder means for providing numerous individually coded control signals.

24. The invention as in claim 1 wherein said first switch means is comprised of an activation arm rigidly secured to the free end of said coil and protruding outward therefrom and a first switch mechanism biased toward an open position wherein said activation signal is precluded, said first switch mechanism being located adjacent to said coil at a position representative of said preset control point, said first switch mechanism being further arranged to be engaged and closed by said activation arm whenever said coil is in a position representative of a distribution transformer load which is greater than said control point, closure of said first switch mechanism being effective to produce said activation signal.

25. The invention as in claim 24 including:

a freely rotatable shaft, said first switch mechanism being mounted on said shaft such that any movement of said coil to a position representative of a distribution transformer load which is greater than said control point causes said activation arm to forceably rotate said first switch mechanism about said shaft to a new position which is representative of a new control point;

a circular ratchet gear rigidly secured to said shaft to rotate co-axially with said shaft; and

a pawl which cooperates with said circular ratchet gear to retain said first switch mechanism at said new position, said pawl being arranged to allow movement of said ratchet gear in a direction representative of an increasing distribution transformer load and to prevent movement of said ratchet gear in a direction representative of a decreasing distribution transformer load.

26. The invention as in claim 1 including a second switch means for generating a second activation signal whenever said reading is above a second present control point.

27. The invention as in claim 26 wherein said reducing means is comprised of means for completely interrupting electrical service to at least one transformer load in response to said activation signal and means for intermittently interrupting electrical service to a different transformer load in response to said second activation signal.

28. The invention as in claim 1, including a switch means for generating a valley control signal whenever said reading drops below a valley preset control point and means for supplying electrical service to at least one preselected transformer load in response to said valley control signal.

29. A load management system for reducing the load in a three-phase alternating current distributing network capable of providing electrical service to at least one network load by means of three separate phase conductor lines, said system comprising:

signal generator means for generating a control signal;

means for injecting said control signal into said three separate phase conductor lines, said injecting means comprising means for separating said control signal into a first control signal, a second control signal and a third control signal, each control signal being separated in phase from the other two control signals by a set amount and a three-phase coupling transformer for introducing each of the three phase shifted control signals into a different phase conductor line, said coupling transformer having three separate primary coils, each primary coil being arranged to receive a different one of the phase shifted control signals, said coupling transformer also having three separate secondary coils, each secondary coil being electrically coupled with a different phase conductor line;

receiver means for detecting the presence of said control signal on said three separate phase conductor lines and for interrupting electrical service to said at least one network load in response to said control signal.

30. The invention as in claim 29 wherein said injecting means includes coupling capacitors and coupling inductors for restricting the amount of 60Hz voltage feed to said signal generator means.

31. A load management system for reducing the load in an electrical power distribution network having at least one remotely located distribution transformer that is capable of supplying electrical power to at least one associated transformer load by means of at least one alternating current distribution line, said system comprising:

power monitor means for monitoring the power load on said distribution transformer, said power monitor means comprising a current transformer means for measuring current flow within said alternating current distribution line, said current transformer means being operable to produce a secondary current which is related to the measured current flow and transducer means for converting said secondary current into a reading representative of the load on said distribution transformer, said transducer means being comprised of a first rotatable shaft and a bimetal spiral coil, said bimetal spiral coil being electrically coupled with said current transformer means such that said secondary current is caused to flow through said coil to vary the temperature of said coil in accordance with the magnitude of said secondary current, said bimetal spiral coil having one end connected to said first rotatable shaft and the other end anchored so that said coil is effective to rotate said first rotatable shaft in response to the temperature of said coil to provide said reading representative of the load on said distribution transformer;

switch means for producing an activation signal whenever said reading is above a preset control point; and

means for reducing the power load on said distribution transformer in response to said activation signal.

32. The invention as in claim 31 including a cam rigidly secured to said first rotatable shaft so as to rotate in unison with said first rotatable shaft.

33. The invention as in claim 32 wherein said switch means is comprised of a switch mechanism biased toward an open position wherein said activation signal is precluded and a cam follower to operate said switch mechanism in accordance with a preselected pattern, said pattern being arranged to close said switch mechanism whenever said cam is in a position representative of a distribution transformer load which is greater than said control point, closure of said switch mechanism being effective to produce said activation signal.

34. The invention as in claim 32 wherein said switch means is comprised of an activation arm rigidly secured to said cam and protruding outward therefrom and a switch mechanism biased toward an open position wherein said activation signal is precluded, said switch mechanism being located adjacent to said cam at a position representative of said preset control point, said switch mechanism being further arranged to be engaged and closed by said activation arm whenever said cam is in a position representative of a distribution transformer load which is greater than said control point, closure of said switch mechanism being effective to produce said activation signal.

35. The invention as in claim 34 including:

a second freely rotatable shaft, said switch mechanism being mounted on said second rotatable shaft such that any movement of said cam to a position representative of a distribution transformer load which is greater than said control point causes said activation arm to forceably rotate said switch mechanism about said second rotatable shaft to a new position which is representative of a new control point;

a circular ratchet gear rigidly secured to said shaft to rotate co-axially with said shaft; and

a pawl which cooperates with said circular ratchet gear to retain said switch mechanism at said new position, said pawl being arranged to allow movement of said ratchet gear in a direction representative of an increasing distribution transformer load and to prevent movement of said ratchet gear in a direction representative of a decreasing distribution transformer load.

36. The invention as in claim 31 wherein said means for reducing the transformer power load is comprised of means for completely interrupting electrical service to said at least one transformer load in response to said activation signal.

37. The invention in claim 31 wherein said means for reducing the transformer power load is comprised of means for intermittently interrupting electrical service to said at least one transformer load in response to said activation signal.

38. The invention as in claim, 31 including a second switch means for generating a second activation signal whenever said reading is above a second present control point.

39. The invention as in claim 38 wherein said reducing means is comprised of means for completely interrupting electrical service to at least one transformer load in response to said activation signal and means for intermittently interrupting electrical service to a different transformer load in response to said second activation signal.

40. The invention as in claim 31, including a switch means for generating a valley control signal whenever said reading drops below a valley present control point and means for supplying electrical service to at least one preselected transformer load in response to said valley control signal.

41. A load management system for reducing the load in an electrical power distribution network having at least one remotely located distribution transformer that is capable of supplying electrical power to at least one associated transformer load by means of at least one alternating current distribution line, said system comprising:

power monitor means for monitoring the power load on said distribution transformer, said power monitor means comprising a current transformer means for measuring current flow within said alternating current distribution line, said current transformer means being operable to produce a secondary current which is related to the measured current flow and sensor means electrically coupled with said current transformer means such that said secondary current flows through said sensor means, said sensor means being operable to cause a forward voltage drop across said sensor means, said forward voltage drop being a nonlinear function of the magnitude of said secondary current;

means for measuring the forward voltage drop across said sensor means, said mesuring means being operable to generate an output signal representative of the measured forward voltage drop; and

means for converting said output signal into a reading representative of the load on said distribution transformer;

switch means for producing an activation signal whenever said reading is above a preset control point; and

means for reducing the power load on said distribution transformer in response to said activation signal.

42. The invention as in claim 41 wherein said switch means is comprised of means for comparing said reading with said control point and means for producing said activation signal if said reading is greater than said control point.

43. The invention in claim 41 wherein said means for reducing the transformer power load is comprised of means for completely interrupting electrical service to said at least one transformer load in response to said activation signal.

44. The invention in claim 41 wherein said means for reducing the transformer power load in comprised of means for intermittently interrupting electrical service to said at least one transformer load in response to said activation signal.

45. The invention as in claim 41, including a switch means for generating a valley control signal whenever said reading drops below a valley preset control point and means for supplying electrical service to at least one preselected transformer load in response to said valley control signal.