WO1999005761A1

WO1999005761A1 - Surge protectors that indicate failure to a remote location

Info

Publication number: WO1999005761A1
Application number: PCT/US1998/015007
Authority: WO
Inventors: Glenn Davis; David Poche
Original assignee: Scientific-Atlanta, Inc.
Priority date: 1997-07-22
Filing date: 1998-07-21
Publication date: 1999-02-04
Also published as: AU8757798A

Abstract

Apparatus and methods for detecting failure of a circuit protection device such as a surge protector and signaling the failure to a remote location via a telecommunications system. Failure of the circuit protection device causes failure of a fuse, which in turn causes a LED to emit light. The light causes a phototransistor to produce a signal to a signaler which signals the remote location via the telecommunications system. In one embodiment, the signaler is an autodialer which dials the remote location using a telephone number that indicates failure of the circuit protection device. The remote location uses the ANI and DNI protocols to obtain the called telephone number, which indicates the type of problem, and the calling telephone number, which indicates the location of the problem. Other implementations of the signaler employ DTMF tones or digital packets to convey the failure information. The digital packet may be communicated to the remote location by means of an analog phone line and modems or by means of digital communications networks. Both the telephone and digital communications networks may be wired or wireless.

Description

Surge Protectors that Indicate Failure to a Remote

Location

Cross-Reference to Related Applications

This application is a continuation under 37 C.F.R. 1.53 of U.S.S.N. 08/898,428, filed 7/22/97. The present patent application has the same title, inventors, and assignee as the parent.

Background of the Invention

1. Field of the Invention

The invention concerns systems for indicating failures to remote locations generally and more specifically concerns systems for indicating failure of a surge protector or a fuse to a location which is so remote that it can be economically reached only by means of telecommunications techniques. One use of the invention is to inform an electric company of the failure of a surge protector connected to an electric meter.

2. Description of the Prior Art: FIG. 1

The connection between the electrical power grid and a customer's premises must include some kind of surge protector, that is, a device which protects at least the electric meter on the premises from power surges in the electrical power grid. Surges occur whenever there is arcing within the power grid; the arcing hav many causes, including a malfunction of the power generation or distribution equipment within the power grid itself, lightning strikes on the power grid, or damage to the power grid caused by accidents or inclement weather. The surge protection for electric meters has typically been a simple spark gap to ground: any surge strong enough to damage the electric meter sparks across the gap to ground, rather than going through the electric meter.

Nowadays, most households contain electrical and electronic equipment that is far more sensitive to surges than an electric meter is, and such equipment is subject to severe damage if the household is protected by nothing more than the spark gap that protects the electric meter. Consequently, power companies have begun to sell add-on surge protectors like the one shown in FIG. 1. As shown there, power lines 101 from the power grid and power lines 111 to the premises are connected to an electric meter socket 102. Normally, electric meter 109 is simply inserted into this socket. If the customer desires surge protection, however, the electric company provides a surge protector 103 which fits into socket 102 and itself has a socket for electric meter 109. If a power surge occurs on power lines 101, surge protector 103 diverts the surge to ground line 107 and thereby prevents it from entering either electric meter 109 or power lines to premises 111. In diverting the surge to ground line 107, surge protector 103 thus protects electric meter 109, the wiring in the customer premises, and customer equipment connected to that wiring.

The chief aim in designing surge protectors 103 has been low cost. Typically, surge protectors have been used which fail when the surge is larger than a threshold value. In failing, the surge protectors still divert the surge to ground line 107, but the failed surge protector offers no protection whatever against succeeding surges. In order to detect that a surge protector has failed, one must visually inspect surge protector 103; typically, a peephole 105 gives visual access to the interior of surge protector 103; as with fuses, a failed surge protector either clouds over the peep hole or can be seen visually to be broken.

In the past, the arrangements described above were adequate to protect power customers; surges large enough to cause the surge protector to fail are relatively rare events and the surge protector was inspected monthly by the meter reader for the power company. In recent years, however, the electric power companies have made great efforts to reduce the number of times a meter is read or even to eliminate meter reading entirely. One of the forces driving this effort has been the expense and danger of meter reading; suburban sprawl has added to the expense of meter reading, while meter reading in slum areas has become more dangerous both by virtue of the condition of the customer premises and by virtue of the high rate of violent crime. Another force driving this effort has been the desire to increase the efficiency with which the customers of the electric utility use electric power. One of the ways in which efficiency is encouraged is to give the customer differential rates, depending on the time of day, so that the customer will do jobs like running an electric dishwasher or cooling the house down at times other than peak load times. Another way is to give the customer a lower rate if the customer is willing to help the electrical utility "shed load" during peak load times, that is, to reduce his power consumption at the request of the electrical utility. Clearly, such efforts to increase efficiency require more interaction between the electrical utility and the customer than was the case when the customer paid rates which were variable only in the sense that the rate per kwH went down as the number of kwH's used went up and the meter reader simply recorded the number of kwH's used since the last time the meter reader read the meter.

The desire to decrease the expense of meter reading and to increase the interaction of the electrical utility with the customer have resulted in many proposals for establishing a telecommunications link between the customer premises and the electrical utility. These have ranged from simple telemetry systems for reading meters, see for example U.S. Patent 4,357,601, through entire energy management and building automation systems, as disclosed in U.S. patent 5,572,438. As far as can be determined, however, none of the discussions of remote meter reading or of close interaction between the customer and the electrical utility deal with the problem of failed surge suppressors; this is the case even though the replacement of the meter reader by remote meter reading clearly increases the risk that a failed surge suppressor will result in damage to the customer's premises or equipment.

The use of surge protectors is of course not limited to the connection between the electrical power grid and the customer premises; surge protectors are also employed within the customer premises for tasks such as protecting computer systems. These surge protectors may fail in the same fashion as those employed in electric meters, and various systems have been designed which notify the user of the surge protector of its failure by sounding an audio or visual alarm. See for example Corey, Transient Surge Suppressor with Alarm Signal Circuit, U.S. patent 5,153,806, issued Oct. 6, 1992 (audio alarm) or Misencik, et al., Electrical Surge Suppressor with Dual Indicator Apparatus, U.S. patent 4,912,590, issued Mar. 27, 1990 (LEDs indicate status of surge protector). None of this technology, however, provides any hint of how to notify a remote location of the failure of a surge protector.

In the fuse arts, LEDs are used to indicate which fuse of a set of fuses has blown. See, for example, Greenberg, Blade Terminal Fuses with Integrity Indicator, U.S. patent 4, 499,447, issued Feb. 12, 1985. The fuse arts have further provided techniques for informing a control system that a fuse has blown while isolating the control system from the consequences of the blown fuse. Clark, Status-indicating Current Interrupter, U.S. patent 4,604,613, issued Aug. 5, 1986, discloses a system in which the fuse includes an optical cable through which a remote monitor station continuously transmits a light signal to itself. When the fuse blows, the optical cable is broken and the failure of the monitor station to receive the light signal indicates to the monitor station that the fuse is blown. Mora, Fuse Loss Indicating Circuit, U.S. patent 4,5 54,607, issued Nov. 19, 1985, discloses a system in which a blown fuse causes a warning LED to light. A photo transistor in a control circuit responds to the warning LED with a signal that indicates to the control circuit that the fuse has blown. Again, there is nothing in this art which is useful to one who is trying to communicate the failure of a surge protector or fuse to a location so remote as to be economically reachable only through the use of telecommunications technologies.

It is thus an object of the present invention to provide techniques whereby failure of a fuse or surge protector may be determined at a remote location reachable through the use of telecommunications technologies.

Summary of the Invention

The object of the invention is achieved by means of apparatus which includes a failure detector that detects failure of the fuse or surge protector by producing a failure indication and a failure signaller that responds to the failure indication by accessing a telecommunications system and signalling the failure to a remote location via the telecommunications system. In another aspect, the failure signaller is electrically isolated from the failure detector, so that the failure signaller is not itself affected by the failure. One way of achieving elecrical isolation is by using an optical signal as the failure indication. The failure signaller signals the failure either by simply dialing a telephone number (the telephone number itself indicates the type of failure to the remote location or by placing a packet with a failure message on a wide-area packet network, either directly or by way of a local-area packet network.

Other objects and advantages of the invention will be apparent to those skilled in the arts to which the invention pertains upon perusing the following Detailed Description and Drawing, wherein:

Brief Description of the Drawing

FIG. 1 is a schematic drawing of a prior-art electric meter with an add-on surge protector;

FIG. 2 is a schematic drawing of an electric meter with an add-on surge protector that reports failure to a remote location; FIG. 3 is a detailed schematic drawing of a surge protection circuit and failure detector employed in a preferred embodiment; FIG. 4 is a block diagram of a first technique for communicating between the failure detector and the remote location; and FIG. 5 is a block diagram of a second technique for communicating between the failure detector and the remote location. The reference numbers in the drawings have at least three digits. The two rightmost digits are reference numbers within a figure; the digits to the left of those digits are the number of the figure in which the item identified by the reference number first appears. For example, an item with reference number 203 first appears in FIG. 2.

Detailed Description

The following Detailed Description will begin with an overview of an electric meter with a surge protector which embodies the technology disclosed herein and will then present detailed implementations of components of the surge protector in the preferred embodiment.

Overview of a Surge Protector which Indicates Failure to a Remote Location: FIG. 2

FIG. 2 is an overview of a preferred embodiment of the invention as employed in a surge protector for an electric meter. Electric meter 109 is connected between lines 101 from the electric power grid and lines 111 to the customer premises, and has a surge protector to protect electric meter 109, the premises wiring, and equipment connected to the premises wiring from surges in the electric power grid by directing the surge to ground 107, exactly as described with regard to FIG. 1 above. There is, however, nothing in surge protection system 201 of FIG. 2 corresponding to peephole 105. Instead, surge protector 203 is coupled to failure detector 205, which detects failures in surge protector 203 by causing light emitter 207 to emit light. The light emitted by light emitter 207 is detected by light detector 211 in failure signaler 209, which responds to the detected light by sending a failure indication via telecommunications link 214 to remote location 215, indicating that surge protector 203 has failed. As will be explained in more detail below, the signal contains information from which at a minimum the location of electric meter 109 may be determined. Remote location 215 then informs the electric utility of the failure and the utility may send a crew to replace surge protection system 201. As may be seen from FIG. 2, the use of lite emitter 207 together with light detector 211 establishes optical isolation 213 between failure detector 205 and failure signaler 209 and ensures that failure signaler 209 will not be disabled by the surge that damaged surge protector 203.

While the following discussion will describe the preferred embodiment in more detail, it should be pointed out here that the techniques shown in FIG. 2 may be used whenever it is worthwhile to indicate failure of a fuse or surge detector to a remote location; further, the principles of the invention are independent of the techniques used to detect failure of the surge protector or fuse, of the techniques used to indicate the failure to the failure signaler, or of the telecommunications techniques used to provide the failure indication to remote location 215. Any suitable technique may be used to perform any of these functions, and the technique used will depend upon factors such as cost and the environment in which the implementation of system 201 is to function.

Preferred Embodiment of Surge Protector 203 and Failure Detector 205: FIG. 3

FIG. 3 shows details of surge protector 203 and failure detector 205 in a preferred embodiment. Beginning with surge protector 203, surge protector 203 contains two metal oxide varistor (MOV) surge protection devices, MOVl and MOV2. MOVl is connected to

L2 of lines 101 from the power grid; MOV2 is connected to line LI of lines 101. MOVl is further connected via fuse FI to ground line 107 and MOV2 is similar connected by fuse F2 to ground line 107. When a surge occurs on line LI, MOV2 shunts it to ground line 107, and MOVl does the same when a surge occurs on line L2.

Failure detector 205 works by connecting a fuse (FI, F2) in series with each MOV (MOVl, MOV2) and a LED (LED1, LED2) in parallel with each fuse. As long as a fuse is intact, current flows through the fuses and not through the LED connected in parallel with it. A power surge that causes a MOV to fail will also blow the fuse that is connected in series with the MOV. That in turn will cause current to flow through the LED connected in parallel with the MOV, and that will cause the LED to emit light.

In more detail, failure detector 205 includes the following components:

• resistor Rl, connected in parallel to MOVl, and resistor R2, connected in parallel to MOV2;

• fuse FI, connected in series between MOVl and ground line 107, and fuse F2, connected in series between MOVl and ground line 107;

• resistor R3, connected in series with LED1 and resistor R4. connected in series with LED2; and

• light emitting diode (LED) 1, connected in series between R3 and ground line 107, and LED2, connected in series between R4 and ground line 107.

Fuse FI and fuse F2 are chosen such that a surge which may cause the MOVs corresponding to the fuses to fail will cause the fuse to blow.

Failure detector 205 operates when MOVl is intact as follows: since MOVl is intact, it transmits no current from L2; current flows via Rl and FI to ground 107, and no current flows through LED1, which remains unlit. Failure detector 205 operates in the same fashion when MOV2 is intact, with current flowing via R2 and FI to ground 107 and no current flowing through LED2. When MOVl has failed, it transmits current, but the surge which caused it to fail also caused

FI to blow, so the only path between L2 and ground line 107 is via Rl, R3, and LED1, which lights up, signaling that MOVl has failed. Similarly, when MOV2 has failed, F2 has blown and the only path between LI and ground line 107 is via R2, R4, and LED2, which lights up, signaling that MOV2 has failed. LED1 and LED 2 thus function as light emitter 207.

When either LED1 or LED2 is illuminated, the light output from LED1 or LED 2 is received by light detector 211, which in a preferred embodiment is a photo transistor. The photo transistor responds to the light from LED1 or LED 2 by beginning to conduct, which in turn signals microprocessor 313 that a MOV has failed in meter 109. As will be explained in more detail below, microprocessor 313 then provides a failure message via telecommunications link 214 to remote location 215. As pointed out above. LEDs 1 and 2 together with photo transistor 211 provide optical isolation 213 between failure detector 205 and failure signaler 209 and thereby assure that microprocessor 313, which receives its power ultimately from load lines 111, is not affected by the surge which caused the failure of MOVl or 2.

Failure Signaler 209 implemented with an Autodialer: FIG. 4

FIG. 4 shows an implementation 209A of failure signaler 209 which employs an autodialer to send an indication of a failure of MOVl or MOV2 via a wired or wireless public switched telephone system to remote location 215. In this implementation, light detector 211 generates a failure signal 401 when LED1 or LED2 is illuminated, and autodialer 403 responds to the failure signal by automatically dialing a telephone number of remote location 215 on telephone connection 404 to the premises to which meter 109 is attached. The telephone connection may of course be used for purposes other than communication between autodialer 403 and remote location 215. The telephone call is routed by telephone company central office switch 405 which has the ANI and DNI features, that is, switch 405 is capable of signaling protocols which return the telephone number from which the call came (ANI) and the telephone number which is the destination of the call (DNI) to the device which answered the call. In a simple implementation, the number dialed by autodialer 403 is used in remote location 215 only for calls identifying failure of a surge protector, and consequently, the fact of the call itself indicates the type of failure. To determine the location of the failure, remote location 215 uses the ANI protocol to obtain the number of the telco connection to premises 404 and then, as shown at 407-11, applies number 409 to location database 407 to obtain location 411. The failure type 415 indicated by the fact that the particular number was called and location 411 are combined in failure message 413, which indicates to a human attendant at remote location 215 or elsewhere the fact of the failure and its location. In a preferred embodiment, autodialer 313 is implemented with microprocessor 313 and a standard telephone dialing interface; microprocessor 313 is programmed to respond to the signal produced by photo transistor 211 when a LED is emitting light by causing the standard telephone dialing interface to dial the number that indicates failure of a surge protector.

It should be pointed out here that detectors for other conditions discernible at electric meter 109 can be included in surge protection system 201 and these conditions can be signaled in to remote location 215 in the same way as the failure of a surge protector is signaled. There would of course be a different telephone number for each condition.

Other implementations of failure signaller 209 are of course possible. In the foregoing implementation, the fact of the phone call itself carries the information needed concerning the failure. In other implementations, the connection established between failure signaler 209 and remote location 215 could be used to carry DTMF tones generated under control of microprocessor 313, and these in turn could provide information from which remote location 215 could determine failure type 415 and location 411. Such an implementation would not require that the telephone connection to premises 404 be connected to a central office switch with ANI and DNI. In still other implementations, failure signaler 209 and remote location 215 could include analog modems connected to telecommunications link 214 and failure information generated by microprocessor 313 could be carried in digital form.

Implementation of Failure Signaler 209 in a System for Communication between a Customer Premises and a Utility: FIG. 5

As indicated above, electrical utilities are beginning to deploy information and control systems which employ telecommunications systems to collect information about energy use and the status of equipment on customer premises and even to control equipment on customer premises. One example of such a system is disclosed in U.S.S.N.08/751,946, Glenn Davis and Paul M. Huddleston, Method and Apparatus for Communicating Information between a Headend and Subscriber over a Wide Area Network, filed November 19, 1996, which is incorporated herein by reference.

Of course, failure signaler 209 may be implemented as part of a system of the type disclosed in the above patent application. FIG. 5 shows a failure signaler 209B which is so implemented. Again, light detector 211 responds to illumination of LED1 or LED 2 by generating failure signal 401, which is received by microprocessor 313. Microprocessor 313 has access to a memory 501 which contains a surge protector failure program (SPFP) 507 which is executed by microprocessor 313 in response to failure signal 401. When executed, SPFP 507 causes microprocessor 313 to generate failure information 510, place it in a local area network (LAN) packet addressed to LAN/WAN interface 515, and outputs the packet to LAN 509. Failure information 510 contains at a minimum a failure identifier 511, which specifies the kind of failure, in this case, the failure of the surge protector, a location identifier 513, which identifies the location of the customer premises, and the WAN address of remote location 215. The location identifier 513 may be a network address, for example, an IP address, of microprocessor 313. Interface 515 receives the LAN packet, places the failure information in a WAN packet addressed to remote location 215, and places the packet on WAN 517. WAN 517 may be implemented using any kind of suitable wired or wireless technology. Remote location 215 receives the packet and produces failure message 413 by applying location identifier 513 from the packet to location database 519 to obtain location 411 and failure identifier 511 to failure data base 521 to obtain failure type 415.

Conclusion

The foregoing Detailed Description has disclosed to those skilled in the arts to which the apparatus and methods disclosed herein pertain the best ways presently known to the inventor of making and using the apparatus and methods. It will be immediately apparent to those skilled in the relevant arts that there are many other ways of implenting circuit protection devices of the general class disclosed herein. Any available communications technique may be used to communicate the fact and location of the failure of a circuit protection device to the remote location and the information that communicates the fact and location may have any usable form. There are similarly many ways of achieving electrical isolation between the failure detector and the signaler and many ways of implementing the failure detector. For these reasons, the Detailed Description is to be regarded as being in all respects exemplary and not restrictive, and the breadth of the invention disclosed herein is to be determined not from the Detailed Description, but rather from the claims as interpreted with the full breadth permitted by the patent laws.

Claims

What is claimed is:

1. Apparatus for signaling failure of a circuit protection element to a remote location accessible by means of a telecommunications system, the apparatus comprising: a failure detector coupled to the circuit protection element, the failure detector responding to a failure of the circuit protection element by producing a failure indication; and a failure signaler, the failure signaler being capable of accessing the telecommunications system and the failure signaler responding to the failure indication by signaling the failure to the remote location via the telecommunications system.

2. The apparatus set forth in claim 1 wherein: the failure indication is a non-electrical signal, whereby the failure signaler is electrically isolated from the failure detector.

3. The apparatus set forth in claim 2 wherein: the failure indication is an optical signal.

4. The apparatus set forth in claim 1 wherein: the telecommunications system is a telephone system; the failure signaler includes an autodialer; and the failure signaler responds to the failure indication by causing the autodialer to automatically dial a telephone number of the remote location.

5. The apparatus set forth in claim 1 wherein: the telecommunications system is a wide-area packet network; the failure signaler is capable of placing a packet on the wide-area packet network; and the failure signaler responds to the failure indication by placing a packet on the wide area network that is addressed to the remote location and contains information about the failure.

6. The apparatus set forth in claim 5 wherein: the failure signaler is connected by means of a local area packet network to an interface to the wide area packet network; and the failure signaler places the packet on the local area packet network.

7. The apparatus set forth in any one of claims 1 through 6 wherein: the circuit protection element is a fuse.

8. The apparatus set forth in any one of claims 1 through 6 wherein: the circuit protection element is a surge protector.

9. The apparatus set forth in claim 8 wherein: the surge protector is made to be installed at an electric power meter.

10. A method of signaling failure of a circuit protection element to a remote location accessible by means of a telecommunications system, the method comprising the steps of: automatically responding to failure of the circuit protection element by producing a failure indication; and automatically responding to the failure indication by employing the telecommunications system to signal the failure to the remote location.

11. The method set forth in claim 10 wherein: the failure indication is a non-electrical signal; and the step of automatically responding to the failure indication is performed in apparatus which is electrically isolated from the failure detector.

12. The method set forth in claim 10 wherein: the telecommunications system is a telephone system; and the step of automatically responding to the failure indication includes the step of automatically dialing a telephone number of the remote location.

13. The method set forth in claim 10 wherein: the telecommunications system is a wide-area packet network; and the step of automatically responding to the failure indication includes the step of placing a packet on the wide area network that is addressed to the remote location and contains information about the failure.

14. The method set forth in any one of claims 10 through 13 wherein: the circuit protection element is a fuse.

15. The method set forth in any one of claims 10 through 13 wherein: the circuit protection element is a surge protector.

16. The method set forth in claim 15 wherein: the surge protector is made to be installed at an electric power meter.

17. An improved surge protector for installation at an electric power meter, the improvement comprising: a failure detector coupled to the surge protector, the failure detector responding to a failure of the surge protector by producing a failure indication; and a failure signaler, the failure signaler being capable of accessing a telecommunications system and the failure signaler responding to the failure indication by signaling the failure to a remote location via the telecommunications system.

18. The improved surge protector of claim 17 wherein: the failure indication is a non-electrical signal, whereby the failure signaler is electrically isolated from the failure detector.

19. The improved surge protector of claim 18 wherein: the failure indication is an optical signal.

20. The improved surge protector of any one of claims 17 through 19 wherein: the telecommunications system is a telephone system; the failure signaler includes an autodialer; and the failure signaler responds to the failure indication by causing the autodialer to automatically dial a telephone number of the remote location.

21. The improved surge protector of any one of claims 17 through 19 wherein: the telecommunications system is a wide-area packet network; the failure signaler is capable of placing a packet on the wide-area packet network; and the failure signaler responds to the failure indication by placing a packet on the wide area network that is addressed to the remote location and contains information about the failure.

22. The improved surge protector of claim 21 wherein: the failure signaler is connected by means of a local area packet network to an interface to the wide area packet network; and the failure signaler places the packet on the local area packet network.

23. A memory device characterized in that: the memory device contains code which when executed in a processor coupled to the failure detector in the improved surge protector of any one of claims 17 through 19 causes the processor to function as the failure signaler.

24. Apparatus for responding to failure of a circuit protection element in a device, the apparatus having access to a telecommunications system and the device also having access thereto, the apparatus comprising: a receiver for receiving an indication via the telecommunications system that the failure has occurred; and an indication analyzer for analyzing the indication to determine at least a location of the failure.

25. The apparatus set forth in claim 24 wherein: the telecommunications system is a telephone system: the indication is a call which the device automatically generates in response to the failure; and the indication analyzer determines the telephone number at which the call originated and determines the location of the failure from the telephone number.

26. The apparatus set forth in claim 24 wherein: the telecommunications system is a wide area network; the indication is a packet which the device automatically generates in response to the failure, the packet being addressed to the apparatus and containing at least location information; and the indication analyzer uses the location information to determine the location of the failure.

27. The apparatus set forth in any one of claims 24 through 26 wherein: the device is a surge protector and the circuit protection element is a surge protection element.

28. A memory device characterized in that: the memory device contains code which when executed in a processor causes the processor to function as the indication analyzer of the apparatus of any one of claims 24 through 26.