Electric utility demand limiting device and method

Claims

What is claimed is:

1. An electrical power demand limiting device for controllably disconnecting a local load extraneous the device from a power source comprising

signal generating means for generating a first signal representative of the electrical power consumption of the load,

comparing means responsive to the signal generating means for comparing the first signal to a preset electrical power consumption limit,

receiving means for receiving a remote control signal from a power production source responsive to conditions at said power production source for providing an enable output in response thereto to enable the operation of the device,

disconnecting means responsive to the comparing means and to the enable output of the receiving means for disconnecting the said extraneous local load entirely from the power source when the first signal exceeds the preset limit and when the receiving means has enabled the device, and

resetting means for resetting the disconnecting means to reconnect the local load to the power source such reconnected load being the entire initial load or a locally selected portion of said initial load.

2. An electrical power demand limiting device for controllably disconnecting a local load extraneous the device from a power source comprising

signal generating means for generating a first signal representative of the electrical power consumption of the load,

comparing means responsive to the signal generating means for comparing the first signal to a preset electrical power consumption limit,

receiving means for receiving a remote control signal a power production source responsive to conditions at said power production source for providing an enable output in response thereto to enable the operation of the device,

disconnecting means responsive to the comparing means and to the enable output of the receiving means for disconnecting the said extraneous local load entirely from the power source when the first signal exceeds the preset limit and when the receiving means has enabled the device wherein said disconnecting means further includes timing means for disconnecting the entire load from the power source after the first signal has exceeded the preset limit for a predetermined period, and

resetting means for resetting the disconnecting means to reconnect the local load to the power source such reconnected load being the entire initial load or a locally selected portion of said initial load.

3. A device as in claim 2 wherein said timing means is further responsive to the enable output of the receiving means for disconnecting the entire load from the power source when the first signal has exceeded the preset limit and the enable output from the receiving means are concurrently present for said predetermined length of time.

4. A device as in claim 1 wherein said preset limit is adjustable.

5. An electrical power demand limiting device for controllably disconnecting a local load extraneous the device from a power source comprising

signal generating means for generating a first signal representative of the electrical power consumption of the load,

comparing means responsive to the signal generating means for comparing the first signal to a preset electrical power consumption limit,

receiving means for receiving a remote control signal from a power production source responsive to conditions at said power production source for providing an enable output in response thereto to enable the operation of the device, said receiving means includes timing means for providing the enable output for a predetermined period of time in response to the remote control signal,

disconnecting means responsive to the comparing means and to the enable output of the receiving means for disconnecting the said extraneous local load entirely from the power source when the first signal exceeds the preset limit and when the receiving means has enabled the device, and

resetting means for resetting the disconnecting means to reconnect the local load to the power source such reconnected load being the entire initial load or a locally selected portion of said initial load.

6. A device as in claim 1 wherein said receiving means is further responsive to a second remote control signal for terminating said enable output.

7. A device as in claim 1 wherein said resetting means is operated manually or when the enable output is not present from said receiving means.

8. An electrical power demand limiting device for controllably disconnecting a local extraneous the device load from a power source comprising

signal generating means for generating a first signal representative of the electrical power consumption of the load,

comparing means responsive to the signal generating means for comparing the first signal to an adjustable preset electrical power consumption limit,

receiving means for receiving a remote control signal from a power production source responsive to conditions at said power production source for providing an enable output in response thereto to enable the operation of the device,

disconnecting means responsive to the signal generating means and to the receiving means for disconnecting the said extraneous local load entirely from the power source when the first signal exceeds the preset limit and the receiving means has enabled the device, said disconnecting means including timing means for disconnecting the entire load from the power source after the first signal has continuously exceeded the preset limit for a predetermined period of time, and

resetting means for resetting the disconnecting means to reconnect the local load to the power source, said resetting means being operated manually or when the enable output is not present from the receiving means, and such reconnected load being the entire initial load or a locally selected portion of said portion of said initial load.

9. A device as in claim 8 further including alarm means for providing an alarm signal when the first signal exceeds the preset limit and said enable output is present.

10. A device as in claim 9 further including means for providing a second alarm signal when said first signal exceeds the preset limit for a second predetermined period of time, said second predetermined period of time being less than said first predetermined period of time.

11. A device as in claim 8 wherein said device further includes alarm means for providing an alarm when said enable output is present.

12. A device as in claim 8 wherein said disconnecting means includes bistable switch means including solenoid means for performing said disconnecting and reconnecting of the load and the power production source.

13. An electrical power demand limiting device adapted for installation at a utility customer site for controllably disconnecting the utility customer from a utility power service comprising

signal generating means for generating a first signal representative of the electrical power consumption of the utility customer,

comparing means responsive to the signal generating means for comparing the first signal to a preset electrical power consumption limit, said preset limit being adjustable by the utility company,

receiving means for providing an enable output to enable the operation of the device and for terminating the enable output, at least said enable output being provided in response to a control signal from the utility company,

disconnecting means responsive to the comparing means and to the receiving means for disconnecting the load from the utility power service when the first signal exceeds the preset limit and the enable output is present, said disconnecting means including timing means for delaying said disconnection until at least the first signal has exceeded the preset limit for a predetermined length of time,

reset means operable at the utility customer site for generating a reset signal,

means responsive to the reset signal and responsive to the receiving means for resetting the disconnecting means when either the reset signal is present or the enable output is not present to reconnect the utility customer to the utility power service to thereby restore the utility power service to the utility customer, and

said device being housed in a housing having an adaptor including first connector means for plugging into a utility meter socket and second connector means for receiving a utility meter and said disconnecting means includes switch means for connecting or disconnecting said first connector means and said second connector means.

14. A device as in claim 13 wherein said switch means is a bistable switch.

15. A device as in claim 13 wherein said predetermined length of time is reset when the first signal is less than the preset limit.

16. A method for controllably limiting power demand from a power source by a local extraneous load including the steps of

generating remotely a first signal at a power production source responsive to conditions at said power production source to enable the power demand limiting,

generating a second signal representative of electrical power consumption by the load,

comparing the electrical power consumption to a preset electrical power consumption limit,

receiving the first signal from said power production source and providing an enable output in response thereto,

disconnecting the said extraneous local load entirely from the power source when the electrical power consumption exceeds the consumption limit and the enable output is present, and

reconnecting the local load to the power source in response to reset means or when the enable output is no longer present, such reconnected load being the entire initial load or a locally selected portion of said initial load.

17. A method for controllably limiting power demand from a power source by a local extraneous load including the steps of

generating remotely a first signal at a power production source responsive to conditions at said power production source to enable the power demand limiting,

generating a second signal representative of electrical power consumption by the load,

comparing the electrical power consumption to a preset electrical power consumption limit,

receiving the first signal from said power production source and providing an enable output in response thereto,

disconnecting the said extraneous local load entirely from the power source when the electrical power consumption exceeds the consumption limit and the enable output is present, wherein the disconnecting step further includes delaying disconnecting the load from the power source until the electrical power consumption has exceeded the preset limit for a continuous predetermined time period, and

reconnecting the local load to the power source in response to reset means or when the enable output is no longer present, such reconnected load being the entire initial load or a locally selected portion of said initial load.

18. A method as in claim 16 further including the step of

providing an alarm when the electrical power consumption exceeds the preset limit.

19. A method for controllably limiting power demand from a utility power source at a utility customer site including the steps of

generating a first signal remotely at said utility power source to enable the power demand limiting,

generating a second signal representative of electrical power consumption at the utility customer site,

comparing the electrical power consumption to an adjustable preset electrical power consumption limit,

receiving the first signal from said utility power source and providing an enable output in response thereto,

disconnecting the utility customer site from the utility power source when the electric power consumption exceeds the consumption limit and the enable output is present, said disconnecting being delayed until the electrical power consumption has exceeded the preset limit for a continuous predetermined time period, and

reconnecting the utility customer site to the utility power source in response to reset means operated at the utility customer site or when the enable output is no longer present.

20. A method as in claim 19 wherein said disconnecting step further includes applying a third signal to a bistable switch means for disconnecting the utility customer site from the utility power source and applying a fourth signal to the bistable switch means for reconnecting the utility customer site to the utility power source.

21. A method for controllably limiting the power demand from a utility power source at a utility customer site including the steps of

generating a first signal remotely at said utility power source to enable the power demand limiting,

generating a second signal representative of electrical power consumption at the utility customer site,

comparing the electrical power consumption to an adjustable preset electrical power consumption limit,

receiving the first signal from said utility power source and providing an enable output in response thereto,

applying a third signal to bistable switch means to disconnect the utility customer site from the utility power source when the electrical power consumption exceeds the consumption limit and the enable output is present, said disconnecting being delayed until the electrical power consumption has continuously exceeded the preset limit for a predetermined time period, and

applying a fourth signal to the bistable switch means to reconnect the utility customer site to the utility power source in response to reset means operated at the utility customer site or when the enable output is no longer present.

22. An electrical power demand limiting device adapted for installation at a utility customer site for controllably limiting power demand from a utility power source comprising

signal generating means for generating a first signal representative of the electrical power consumption of the utility customer,

comparing means responsive to the signal generating means for comparing the first signal to a preset electrical power consumption limit, said preset limit being adjustable by the utility source,

receiving means for providing an enable output to enable the operation of the device and for terminating the enable output, at least said enable output being provided in response to a control signal from the utility source,

disconnecting means responsive to the comparing means and to the receiving means adapted for disconnecting load from the utility power source when the first signal exceeds the preset limit and the enable output is present, said disconnecting means including timing means for delaying said disconnection until at least the first signal has exceeded the preset limit for a predetermined length of time,

reset means operable at the utility customer site for generating a reset signal,

means responsive to the reset signal and responsive to the receiving means for resetting the disconnecting means when either the reset signal is present or the enable output is not present to reconnect the utility customer to the utility power source to thereby restore utility power to the utility customer, and

said device being housed in a housing having an adapter including first connector means for plugging into a utility meter socket and second connector means for receiving a utility meter.

23. An adapter as claimed in claim 22 wherein said disconnecting means is connected with switch means and is adapted to activate said switch means.

24. An adapter as claimed in either claim 22 or claim 23 wherein said housing includes a substantially cylindrical horizontal meter extender, and a substantially rectangular casing mounting on a support column between the extender and casing.

25. A method for controllably limiting power demand from a utility power source at a utility customer site including the steps of plugging into a meter utility socket an adapter for receiving a meter at the end remote from the socket,

generating a first signal representative of the electrical power consumption of the utility customer,

generating a second signal remotely from said power utility source to enable the power demand limiting,

comparing the first signal to a preset electrical power consumption limit, said preset limit being adjustable by the utility company,

receiving the second signal and providing an enable output in response to the second signal from the utility company,

disconnecting load from the utility power service when the first signal exceeds the preset limit and the enable output is present, said disconnecting being delayed until at least the first signal has exceeded the preset limit for a predetermined length of time,

generating a reset signal at the utility customer site, and

reconnecting load when either the reset signal is present or the enable output is not present thereby to reconnect the utility customer to the utility power source and restore utility power to the utility customer.

26. A method as claimed in claim 25 wherein disconnection includes applying a third signal to switch means for disconnecting the utility customer site from the utility power.

BACKGROUND OF THE INVENTION

The present invention relates generally to utility power conservation devices and more particularly to an electric utility demand limiting device and method for controllably connecting and disconnecting a utility customer from a utility power system.

As the cost and difficulty of providing additional electrical power generating capacity increases, electrical power utilities have sought ways to limit or decrease the peak electrical power demand that may occur throughout a typical operating day. By limiting or lowering this peak demand, additional generating capacity need not be added and the existing generating capacity may be more efficiently utilized.

Various devices, systems and methods have been proposed toward this end. For example, in order to vary the cost of electric power to a customer and to thus discourage power consumption when overall demand is high, U.S. Pat. No. 3,683,343 to Feldman, et al. describes a remotely controlled demand metering system. The meter, upon reception of suitably coded signals from a power station, records a number of kilowatt-hours greater than actually consumed. This metering system, however, only encourages voluntary conservation by the customer and thus does not effectively limit the customer's electrical power consumption to some preset limit.

As another incentive for reducing power consumption during peak demand periods, the utilities have instituted demand billing wherein the cost of electrical power varies with the customer's maximum demand during a predetermined time period. Various devices, systems and methods are known that can be used at the utility customer's site to monitor power consumption and to disconnect one or more loads to thus control the customer's peak power consumption. Such devices, systems and methods are described, for example, in U.S. Pat. Nos. 3,789,236, 4,075,699, 4,117,537, 4,125,782, 4,125,895, 4,153,936, 4,167,679 and 4,168,491. The patent to Lacroix, U.S. Pat. No. 3,789,236, also describes a device that can sound an alarm when power consumption reaches a preselected threshold.

These devices, however, do not respond to a remote control signal from a utility company. Thus, although there may actually be no necessity for limiting power demand, the devices will still function to disconnect loads or sound alarms, consequently resulting in greater customer inconvenience than is necessary. Also, these devices generally integrate power consumption with respect to time. If the customer's load includes devices or machines that have a high inrush current as occurs, for example, during the start of electric motors, this integration technique can cause the control device to disconnect loads prematurely.

Moreover, since these devices disconnect or connect specific loads in response to excessive power consumption, it is not possible for the customer to easily select the particular load that is desired to be disconnected at a particular time. This can result in inconvenience where, for example, the control device controls an air conditioning compressor but the customer instead desires to continue operation of the compressor and to instead disconnect some other load such as a swimming pool pump motor or an electric water heater. This leads not only to increased customer inconvenience but also can result in substantial customer dissatisfaction.

Further disadvantages of the control devices discussed in the above-referenced patents is that the devices are generally relatively complex and that it is often difficult to retrofit such a device at the customer's site because extensive wiring and modification of various of the customer's loads is required.

Yet other devices and systems are known which disconnect specific customer loads in response to a control signal generated at a remote point. Such devices and systems are generally described in U.S. Pat. Nos. 3,906,242, 4,023,043, 4,130,874, 4,135,181, 4,152,605 and 4,161,720. The systems can allow an electric utility to disconnect certain of the consumer's loads during peak power demand times so that the peak power demand can be reduced.

Such devices and systems, however, disconnect or shed selected customer loads regardless of the total power consumption by the individual customer. Although this can help to limit peak demand, some customers may still retain a relatively large power demand during this period. Also, as discussed above, these devices and systems do not allow an individual customer to select the particular load that the customer desires to do without during the peak demand period.

Also, several of the systems require relatively complex and expensive control centers and correspondingly complex and expensive devices at the customer's site. The individual customer loads to be disconnected must also be modified and connected to the control device. Although the control devices may disconnect specified loads, these control devices do not encourage overall utility customer conservation since the remaining customer load is unaffected. Furthermore, since only a portion of the customer's total load is controlled, it is more difficult for the utility company to accurately project the peak power demand that may occur at a given time.

SUMMARY OF THE INVENTION

A demand limiting device and method in accordance with the present invention overcomes the limitations and disadvantages described above. The device and method of the present invention are not limited to utility customer power limiting or shedding applications. For example, the present invention may be advantageously employed within an energy producing facility such as an integrated refinery or coal gassification plant which produces as well as consumes electrical energy to thereby adjust peak load conditions. However, the invention will be described in terms of a preferred embodiment suitable for use by an electrical utility. Other applications will be readily apparent to those skilled in the art.

One demand limiting device of the invention includes, in an exemplary embodiment, detectors which provide an output that is proportional to the power consumption of a utility customer. The output from the detectors is compared with a preset electrical power consumption limit and when the power consumption exceeds the preset limit and the device is enabled in response to a remote control signal from the power utility, a switch is operated to disconnect the customer from the utility power source. To restore service, the device includes resetting means to reconnect the customer to the utility power source to thereby restore the utility power to the customer. One or more alarms may be provided to the customer to indicate various operational states. The demand limiting device may be advantageously contained in a housing that includes an adaptor which may be quickly and easily installed between a conventional kilowatt-hour meter and an associated meter socket.

A method according to the present invention includes generating a signal that is representative of electrical power consumption at a utility customer site and comparing this signal with a preset electrical power consumption limit. When enabled by a remote control signal, the utility customer is disconnected from the utility power source when the electrical power consumption exceeds the consumption limit. However, the utility customer can be reconnected to the utility power source by reset means operated at the utility customer site or when the power demand limiting method is no longer enabled.

Thus, a device according to the present invention is easily installed and provides a power consumption comparison at the customer's site in response to a utility company remote control signal. Moreover, such a device continuously performs this comparison rather than summing or integrating power consumption over a time period so that large transient loads will not inadvertently and inconveniently cause the device to disconnect the customer from the utility power service. Because a demand limiting device according to the present invention may be installed for individual customers, each customer can allocate electrical power up to the preset limit during a peak demand period, thus increasing the freedom of choice available to the customer in the determination of the specific loads that will or will not be maintained. Furthermore, since the preset limit may be adjusted by the utility company, the utility company can then offer various preset limits to which individual customers may "subscribe" with, for example, lower preset limits resulting in lower electrical power costs and thereby encouraging electrical power conservation. This enhances the ability of the utility company to more accurately predict peak demand power levels. Also, the various alarms available to the customer allow the customer to adjust individual loads during peak demand periods so that the customer's electrical power service will not be interrupted. Similarly, a method practiced in accordance with the present invention provides comparable advantages.

It is thus an object of the present invention to provide an improved demand limiting device and method.

It is another object of the present invention to provide a demand limiting device that is easily installed at the customer's site and a method that is easily implemented.

It is a further object of the present invention to provide a demand limiting device and method wherein power demand is individually determined for each customer.

These and other advantages and objects of the present invention will become apparent from the following detailed description in conjunction with the drawings wherein:

FIG. 1 is an exploded perspective view of an exemplary electrical power service entrance employing a device in accordance with the present invention;

FIG. 2 is a simplified sectional view of the device and a kilowatt-hour meter taken substantially along the line 2--2 of FIG. 1;

FIG. 3 is a simplified schematic diagram of a demand limiting device according to the present invention.

A demand limiting device 10, as shown in FIG. 1 and as is described below, includes power detectors which provide an output that is proportional to the power delivered from a power source, such as an electric utility company, to a load which can be, for example, a residential utility customer. The device 10 further includes a receiver which, in response to a remote control signal from the utility company, enables the power demand limiting function performed by the device 10. When a comparator output indicates that the output from the detectors exceeds a preset electrical power consumption limit and when the receiver has enabled the device 10, a timer operates a switch after a predetermined time period to disconnect the load from the power source. Electrical power may be restored by operating reset means or when the device 10 is no longer enabled by the receiver. One or more alarms may be provided to indicate, for example, that the device has been enabled, that the power consumption exceeds the preset limit, or that the power consumption has exceeded the preset limit for a second predetermined length of time.

With reference to FIG. 1, a demand limiting device 10 may be contained in a housing generally designated 12. The housing 12 includes a cylindrical horizontal meter extender or adaptor 14, a rectangular receiver and control module case 16 and a support column 18 extending between the adaptor 14 and the case 16. The adaptor 14 includes a plurality of connecting plugs 20-26 as seen in FIGS. 1 and 2 extending from a rear plug surface 28 of the adaptor 14. Similarly, a plurality of connecting jacks 30-36 extend from a front jack surface 38 of the adaptor 14.

With continued reference to FIG. 1, an electric utility service entrance 40 for, for example, a residential customer, generally includes a kilowatt-hour meter socket 42 that has a plurality of connecting jacks 44-50. Incoming 240 volt lines 52 and 54 are connected to the jacks 44 and 46, respectively. The lower jacks 48 and 50 are connected to the customer's circuit breaker box 56 to thus provide electrical power service to the customer. Conventionally, a common or return line 58 passes through the meter socket 42 to the circuit breaker box 56. A conventional kilowatt-hour meter 60 may be connected to the socket 42 by connecting a plurality of meter connecting plugs 62-68 to the corresponding socket connecting jacks 44-50. The meter 60 completes the circuit from the incoming utility lines 52 and 54 to the customer's circuit breaker box 56.

The connecting plugs 20-26 of the device 10 are disposed on the rear plug surface 28 in a configuration similar to the connecting plugs 62-68 of the meter 60. Similarly, the connecting jacks 30-36 are disposed on the front socket surface 38 in a configuration similar to the meter socket connecting jacks 44-50.

To install the demand limiting device 10 of the present invention, the meter 60 is removed from the meter socket 42. In its place, the device 10 is installed into the meter socket 42 so that the connecting plugs 20-26 are inserted into and thus connect to the corresponding connecting jacks 44-50. The meter 60 may then be installed on the front connector surface 38 of the device 10 to connect the meter connecting plugs 62-68 to the device connecting jacks 30-36. In this way, the device 10 is easily and quickly installed. Conversely, the device 10 can be quickly and easily removed by disconnecting the device 10 from the meter socket 42, disconnecting the meter 60 from the device 10 and reinstalling the meter 60 into the meter socket 42.

Turning now to FIG. 2,