Power monitoring and load shedding system

• US 4,075,699 A
• Filed: 06/24/1976
• Issued: 02/21/1978
• Est. Priority Date: 06/24/1976
• Status: Expired due to Term

• Current Assignee: Lockheed Electronics Co., Inc., (Martin Marietta Corporation)
• Original Assignee: Lockheed Electronics Co., Inc., (Martin Marietta Corporation)
• Inventors: Schneider, Richard A., Freed, Gerald L., Lipnick, Richard
• Primary Examiner(s): Wise, Edward J.
• Application Number:
  US05/699,571
• Time in Patent Office: 607 Days
• Field of Search: 235/151.21, 235/92 EL, 444/1, 340/172.5, 324/103 R, 307/57, 307/87, 307/29, 307/31
• US Class Current: 700/291
• CPC Class Codes: G01R 11/64 Maximum meters, e.g. tariff for a period is based on maximum demand within that period
• CPC Class Codes: G01R 21/00 Arrangements for measuring electric power or power factor G01R7/12 takes precedence

Abstract

An electrical power controlling/load shedding system includes power consumption metering and meter interfacing circuitry for entering overall power consumption into a central processing unit. The CPU memory includes a data storage table characterizing each system electrical load under each of a hierarchy of operational levels, and circuitry is provided for turning local and remote loads on/off, responsive to CPU-issued commands.

The digital computing apparatus operates on the meter supplied information and projects energy consumption over the monitoring interval. If power must be shed to obviate an excessive projected demand, loads are examined seriatim and selectively shed on a priority basis as required, depending upon the operational parameters and status characterizing each load for the then prevailing load level condition.

Claims

1. In combination in a power load shedding system for controlling the operative status of plural controllable system loads each selectively connectable to a source of energy, comprising stored program controlled digital computer means including a central processing unit and memory means communicating with said central processing means, said memory means including data storage means for each load for storing the characteristics and status of the associated load, plural controlled switch means for selectively connecting and disconnecting the controllable system loads with the energy source, control circuitry responsive to signals issued by said computer means for controlling the status of said controlled switch means, and means for signaling to said computer means the power being consumed by the system loads, said computer means including means for projecting energy consumption over a measuring interval, excessive power signaling means for comparing said projected energy consumption with a permissible bound therefor and for signaling when the projected consumption exceeds said permissible bound therefor, load shedding means responsive to said excessive power signaling means indicating an excessive energy consumption projection for examining said data storage means for the system loads in said memory means for selectively operating said controlled switch means via said control circuitry to operatively disconnect selected system loads from the energy source, wherein said control circuitry comprises a register having plural stages each signaling the desired relative operative condition for a different system load, and plural relays each responsive to the output of an associated register stage for controlling the state of an associated one of said plural controlled switch means, further comprising plural multi-position switches including a first pole serially included between said register and one of said controlled switch means associated therewith, further comprising status circuitry for supplying information to said central processing unit, said status circuitry including an additional register having a first plurality of stages, wherein each of said multi-position switches of said control circuitry includes an additional pole connected to a different stage to said additional register.

2. A combination as in claim 1 wherein said additional register includes an additional plurality of stages, and wherein each said controlled switch means includes a contact connected to a different one of said second stage plurality of said additional register.

3. In combination in a power load shedding system for controlling the operative status of plural controllable system loads each selectively connectable to a source of energy, comprising stored program controlled digital computer means including a central processing unit and memory means communicating with said central processing means, said memory means including data storage means for each load for storing the characteristics and status of the associated load, plural controlled switch means for selectively connecting and disconnecting the controllable system loads with the energy source, control circuitry responsive to signals issued by said computer means for controlling the status of said controlled switch means, and means for signaling to said computer means the power being consumed by the system loads, said computer means including means for projecting energy consumption over a measuring interval, excessive power signaling means for comparing said projected energy consumption with a permissible bound therefor and for signaling when the projected consumption exceeds said permissible bound therefor, load shedding means responsive to said excessive power signaling means indicating an excessive energy consumption projection for examining said data storage means for the system loads in said memory means for selectively operating said controlled switch means via said control circuitry to operatively disconnect selected system loads from the energy source, further comprising a power distribution bus, and wherein said power consumption signaling means comprises power meter means coupled to said bus, further comprising demand meter interface circuitry connecting said power meter means and said central processing unit, said demand meter interface circuitry including counter means for accumulating impulses each representative of a fixed quantity of energy consumption.

4. In combination in a power load shedding system for controlling the operative status of plural controllable system loads each selectively connectable to a source of energy, comprising stored program controlled digital computer means including a central processing unit and memory means communicating with said central processing means, said memory means including data storage means for each load for storing the characteristics and status of the associated load, plural controlled switch means for selectively connecting and disconnecting the controllable system loads with the energy source, control circuitry responsive to signals issued by said computer means for controlling the status of said controlled switch means, and means for signaling to said computer means the power being consumed by the system loads, said computer means including means for projecting energy consumption over a measuring interval, excessive power signaling means for comparing said projected energy consumption with a permissible bound therefor and for signaling when the projected consumption exceeds said permissible bound therefor, load shedding means responsive to said excessive power signaling means indicating an excessive energy consumption projection for examining said data storage means for the system loads in said memory means for selectively operating said controlled switch means via said control circuitry to operatively disconnect selected system loads from the energy source, further comprising a first plurality of system loads controlled by said controlled switch means, a second plurality of system loads, an additional plurality controlled switch means each controlling a different one of said additional loads, a remote system controller, additional control circuitry responsive to signals supplied thereto by said remote system controller for controlling the operative state of said additional controlled switch means, and coupling means interconnecting said stored program digital computer means with said remote system controller.

5. A combination as in claim 4 wherein said coupling means includes universal asyncronous receiver and transmitter means serially connected between said digital computer and said remote system controller.

6. A combination as in claim 5 wherein said remote system controller includes decoder and sequencer means.

7. A combination as in claim 4 wherein said remote system controller includes decoder and sequencer means.

8. In combination in a power load shedding system for controlling the operative status of plural controllable system loads each selectively connectable to a source of energy, comprising stored program controlled digital computer means including a central processing unit and memory means communicating with said central processing means, said memory means including data storage means for each load for storing the characteristics and status of the associated load, plural controlled switch means for selectively connecting and disconnecting the controllable system loads with the energy source, control circuitry responsive to signals issued by said computer means for controlling the status of said controlled switch means, and means for signaling to said computer means the power being consumed by the system loads, said computer means including means for projecting energy consumption over a measuring interval, excessive power signaling means for comparing said projected energy consumption with a permissible bound therefor and for signaling when the projected consumption exceeds said permissible bound therefor, load shedding means responsive to said excessive power signaling means indicating an excessive energy consumption projection for examining said data storage means for the system loads in said memory means for selectively operating said controlled switch means via said control circuitry to operatively disconnect selected system loads from the energy source, further comprising a first plurality of system loads connected to said controlled switch means and at least one additional system load, encoder means communicating with said central processing unit, a source of power, means for multiplexing power supplied by said power source and control signals generated by said encoder, and powerless remote terminal means comprising means selectively responsive to said multiplexed power and encoder supplied signals supplied by said multiplexing means for energizing said at least one additional load with the power supplied thereto.

9. A combination as in claim 8 wherein said powerless remote terminal means includes a separation filter, decoder, and latch and relay means.

10. In combination in a power load shedding system for controlling the operative status of plural controllable system loads each selectively connectable to a source of energy, comprising stored program controlled digital computer means including a central processing unit and memory means communicating with said central processing means, said memory means including data storage means for each load for storing the characteristics and status of the associated load, plural controlled switch means for selectively connecting and disconnecting the controllable system loads with the energy source, control circuitry responsive to signals issued by said computer means for controlling the status of said controlled switch means, and means for signaling to said computer means the power being consumed by the system loads, said computer means including means for projecting energy consumption over a measuring interval, excessive power signaling means for comparing said projected energy consumption with a permissible bound therefor and for signaling when the projected consumption exceeds said permissible bound therefor, load shedding means responsive to said excessive power signaling means indicating an excessive energy consumption projection for examining said data storage means for the system loads in said memory means for selectively operating said controlled switch means via said control circuitry to operatively disconnect selected system loads from the energy source, wherein said energy consumption projecting means includes means for determining the present rate of energy consumption responsive to the signals provided by said consumption signaling means, means for determining the power consumed since the beginning of an operative cycle, means for computing the energy postulated to be consumed over the remainder of a monitoring interval by determining the product of the time remaining to the end of a monitoring period and the present rate of power consumption, and means for summing the energy actually consumed to present with the energy postulated to be consumed within the remainder of the measuring interval, wherein said product determining means includes means for effectively multiplying the power saved by turning a load off with the lesser of the period the load is to be shut off or the remainder of a monitoring interval.

11. A combination as in claim 10 wherein said means for determining the present rate of consumption includes means for effecting a weighted average of signals indicative of power consumption during a most recent sampling interval and consumptions measured during earlier intervals.

12. In combination in a power load shedding system for controlling the operative status of plural controllable system loads each selectively connectable to a source of energy, comprising stored program controlled digital computer means including a central processing unit and memory means communicating with said central processing means, said memory means including data storage means for each load for storing the characteristics and status of the associated load, plural controlled switch means for selectively connecting and disconnecting the controllable system loads with the energy source, control circuitry responsive to signals issued by said computer means for controlling the status of said controlled switch means, and means for signaling to said computer means the power being consumed by the system loads, said computer means including means for projecting energy consumption over a measuring interval, excessive power signaling means for comparing said projected energy consumption with a permissible bond therefor and for signaling when the projected consumption exceeds said permissible bound therefor, load shedding means responsive to said excessive power signaling means indicating an excessive energy consumption projection for examining said data storage means for the system loads in said memory means for selectively operating said controlled switch means via said control circuitry to operatively disconnect selected system loads from the energy source, wherein said data storage means for each load includes means for storing the relative priority of the associated load, and wherein said load shedding means comprises means for iteratively examining said data storage for the system loads on a monotonically increasing priority basis, said central processing unit shedding loads via said control circuitry and said controlled switch means on a monotonically increasing priority basis, wherein said data storage means for said loads includes load characteristics which are differently defined depending upon a system operation level variable, and means for prescribing a value for said system operational level variable.

13. A combination as in claim 12 wherein said data storage means for the system loads includes level dependent minimum on and off times and priority variables, and level independent status, power and transaction time variables.

14. In combination in a power load shedding system for controlling the operative status of plural controllable system loads each selectively connectable to a source of energy, comprising stored program controlled digital computer means including a central processing unit and memory means communicating with said central processing means, said memory means including data storage means for each load for storing the characteristics and status of the associated load, plural controlled switch means for selectively connecting and disconnecting the controllable system loads with the energy source, control circuitry responsive to signals issued by said computer means for controlling the status of said controlled switch means, and means for signaling to said computer means the power being consumed by the system loads, said computer means including means for projecting energy consumption over a measuring interval, excessive power signaling means for comparing said projected energy consumption with a permissible bound therefor and for signaling when the projected consumption exceeds said permissible bound therfor, load shedding means responsive to said excessive power signaling means indicating an excessive energy consumption projection for examining said data storage means for the system loads in said memory means for selectively operating said controlled switch means via said control circuitry to operatively disconnect selected system loads from the energy source, wherein said data storage means for each load includes parameters dependent upon an operational level, and wherein said load shedding means includes nested iteratively operative means, wherein the inner of said iteratively operative means selectively sheds loads by examining data storage for each load at given load characterizing priority, and wherein the outer of said nested iterative loops monotonically indexes on increasing priority.

15. In combination in a power load shedding system for controlling the operative status of plural controllable system loads each selectively connectable to a source of energy, comprising stored program controlled digital computer means including a central processing unit and memory means communicating with said central processing means, said memory means including data storage means for each load for storing the characteristics and status of the associated load, plural controlled switch means for selectively connecting and disconnecting the controllable system loads with the energy source, control circuitry responsive to signals issued by said computer means for controlling the status of said controlled switch means, and means for signaling to said computer means the power being consumed by the system loads, said computer means including means for projecting energy consumption over a measuring interval, excessive power signaling means for comparing said projected energy consumption with a permissible bound therefor and for signaling when the projected consumption exceeds said permissible bound therefor, load shedding means responsive to said excessive power signaling means indicating an excessive energy consumption projection for examining said data storage means for the system loads in said memory means for selectively operating said controlled switch means via said control circuitry to operatively disconnect selected system loads from the energy source, wherein said data storage means for each load includes means for storing plural values for at least one load descriptor each operative for a distinct operational level, and said memory means includes means defining the then obtaining operational level.

16. A combination as in claim 15 wherein said central processing unit and memory means include indirect addressing means for processing load descriptors dependent upon said level defining means.