Tamper detection system for load management device

• US 5,345,225 A
• Filed: 10/30/1992
• Issued: 09/06/1994
• Est. Priority Date: 10/30/1992
• Status: Expired due to Term

• Current Assignee: Comverge Incorporated (Itron, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Davis, Glenn A.
• Primary Examiner(s): SWANN III, GLEN R
• Application Number:
  US07/969,123
• Time in Patent Office: 676 Days
• Field of Search: 340/653, 340/644, 340/635, 340/664, 340/540, 307/38, 307/40
• US Class Current: 340/635
• CPC Class Codes: G08B 21/185 Electrical failure alarms
• CPC Class Codes: H02J 13/00022 using wireless data transmission
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 40/126 using wireless data transmission

Abstract

A tamper detection system for promptly warns a utility that it has lost control of a load which is part of a load management system, and may be giving price incentives to a customer without receiving the corresponding benefit arising from the intended control of the load. A monitor circuit automatically determines whether the load management device is connected to the load by detecting whether a current is passing via the load control device to the load, and generates a warning signal when no current is detected for a first predetermined period of time. The load current is detected either by inductively coupling a conductor to the load with a sensing conductor, or by sensing current induced in the load control relay as the load current passes through the relay contacts. The tamper detection feature operates without any activity of the load management device, and detects disconnection of the load even when the load management device itself is powered up and working properly.

Claims

1. An apparatus for monitoring the connection status of a load control device, comprising:

monitoring means for detecting whether a current is passing via said load control device to a load; and

signal means responsive to said monitoring means for generating a warning signal when no current is detected by said monitoring means for a first predetermined period of time.

2. The apparatus of claim 1, wherein said monitoring means continuously detects whether a current is passing via said load control device to said load.

3. The apparatus of claim 2, wherein said load control device includes a relay circuit connected to alternately supply and terminate current to the load, and wherein said monitoring means comprises means for sensing a field induced in said relay circuit when current is passing via said load control device to said load.

4. The apparatus of claim 2, wherein said monitoring means comprises:

a sensing conductor;

a coupling loop, formed of magnetic material, surrounding said sensing conductor and a conductor connected to said load; and

means for detecting current induced in said sensing conductor when current is passing via said load control device to said load.

5. The apparatus of claim 4, wherein said coupling loop comprises a ferrous toroid.

6. The apparatus of claim 1, further comprising:

reset means for restarting said predetermined period of time upon detection of a current by said monitoring means.

7. The apparatus of claim 6, wherein said reset means is operable to restart said first-recited predetermined period of time after detection of a current by said monitoring means continuously for a predetermined second period of time.

8. The apparatus of claim 7, further comprising means for altering said first period of time.

9. The apparatus of claim 1, wherein said said load control device further comprises a data storage device including at least one memory location;

and wherein said signal means is connected to said data storage device such that said warning signal sets a predetermined memory location in said data storage device to a predetermined state.

10. The apparatus of claim 9, further comprising means responsive to said predetermined memory location'"'"'s being in said predetermined state for activating a visual indicator positioned on said load control device.

11. The apparatus of claim 9, further comprising data collection means for reading the state of said predetermined memory location.

12. The apparatus of claim 11, wherein said data collection means is operable at a location remote from said load control device.

13. A method for monitoring the connection status of a load control device, comprising the steps of:

detecting whether a current is passing via said load control device to a load; and

responsive to detection of no current passing via said load control device to said load for a predetermined period of time, generating a warning signal.

14. The method of claim 13, wherein said detecting step comprises continuously determining whether a current is passing via said load control device to said load.

15. The method of claim 14, wherein said load control device includes a relay circuit connected to alternately supply and terminate current to the load, and wherein said detecting step comprises sensing a field induced in said relay circuit when current is passing via said load control device to said load.

16. The method of claim 14, wherein said detecting step comprises:

magnetically coupling a sensing conductor with a conductor connected to said load; and

detecting current induced in said sensing conductor when current is passing via said load control device to said load.

17. The method of claim 16, wherein said coupling step comprises surrounding said sensing conductor and said conductor connected to said load with a ferrous toroid.

18. The method of claim 13, further comprising the step of restarting said predetermined period of time upon detection of a current.

19. The method of claim 18, wherein said restarting step comprises restarting said first-recited predetermined period of time after detection of a current continuously for a predetermined second period of time.

20. The method of claim 13, further comprising the steps of communicating said warning signal to a data storage device including at least one memory location;

and in response to receipt of said warning signal setting a predetermined memory location in said data storage device to a predetermined state.

21. The method of claim 20, further comprising the step of activating a visual indicator positioned on said load control device responsive to said predetermined memory location'"'"'s being in said predetermined state.

22. The method of claim 20, further comprising the step of reading the state of said predetermined memory location.

23. The method of claim 20, further comprising the step of reading the state of said predetermined memory location from a site remote from said load control device.

24. An apparatus for monitoring the connection status of a load control device, comprising:

a monitor operative to detect whether a current is passing via said load control device to a load; and

a signal generator, responsive to said monitor, operative to generate a warning signal when no current is detected by said monitor for a predetermined period of time.

25. The apparatus of claim 24, wherein said monitor continuously detects whether a current is passing via said load control device to said load.

26. The apparatus of claim 25, wherein said load control device includes a relay circuit connected to alternately supply and terminate current to the load, and wherein said monitor comprises a sensor operative to sense a field induced in said relay circuit when current is passing via said load control device to said load.

27. The apparatus of claim 25, wherein said monitor comprises:

a sensing conductor;

a coupling loop, formed of magnetic material, surrounding said sensing conductor and a conductor connected to said load; and

a detector operative to detect current induced in said sensing conductor when current is passing via said load control device to said load.

28. The apparatus of claim 27, wherein said coupling loop comprises a ferrous toroid.

29. The apparatus of claim 24, further comprising:

a reset circuit for restarting said predetermined period of time upon detection of a current by said monitor.

30. The apparatus of claim 29, wherein said reset circuit is operable to restart said first-recited predetermined period of time after detection of a current by said monitor continuously for a predetermined second period of time.

31. The apparatus of claim 30, wherein said first-recited predetermined period of time is altered in response to said load control device'"'"'s receiving a selected command from a command center remotely located from said load control device.

32. The apparatus of claim 24, wherein said load control device further comprises a data storage device including at least one memory location;

and wherein said signal generator is connected to said data storage device such that said warning signal sets a predetermined memory location in said data storage device to a predetermined state.

33. The apparatus of claim 32, wherein a visual indicator positioned on said load control device is activated when said predetermined memory location is set to said predetermined state.

34. The apparatus of claim 32, further comprising a data collector operative to rad the state of said predetermined memory location.

35. The apparatus of claim 34, wherein said data collector is operable at a location remote from said load control device.