Abstract:
A meter-base surge protector adapted to be connected between multiple incoming power lines and a neutral line at a meter comprises first and second metal oxide varistors, which are each respectively connected in series to first and second thermal cut-offs and a gas discharge tube. The first and second thermal cut-offs are each connected to separate incoming power lines. The gas discharge tube is also connected to the incoming neutral line. The meter-base surge protector also includes a microcontroller for monitoring and detecting the voltage status at monitoring points within the circuit, or system, for detecting circuit, or system, malfunction. Upon the detection of a malfunction, the microcontroller activates a non-surge protection status indicator.

Description:
FIELD OF THE INVENTION  
       [0001]     The apparatus according to the present invention relates generally to building entrance surge protectors and, more particularly, to a building entrance power meter-base surge protector connected between a building entrance power meter and the power meter base and to the display of surge protection status of the apparatus.  
       BACKGROUND OF THE INVENTION  
       [0002]     The field of surge protectors connected between electrical AC power lines and building entrances has focused on the use of a surge protector circuit, or a plurality of sub-circuits, each comprised of a plurality of electrically parallel metal oxide varistors (MOV) connected in series to a gas discharge tube (GDT). One such surge protector is the building entrance surge protector disclosed in U.S. Pat. No. 6,778,375, entitled “Hybrid MOV/Gas-Tube AC Surge Protector For Building Entrance”, issued on Aug. 17, 2004 to Gerald B. Hoopes and assigned to Panamax, Petaluma, Calif., hereinafter referred to as “the Hoopes patent”. The Hoopes patent utilizes a surge protector circuit or plural sub-circuits connected between single-phase or multi-phase AC power lines, at the MOV side of each protector circuit or sub-circuit, and the building ground, at the GDT side of each protector circuit or sub-circuit. With this type of arrangement, multiple surge protection circuit paths between the same AC power line and the building ground are available through any one of a plurality of MOV and GDT combinations. In such a multi-phase arrangement, each of the multi-phase power lines are connected to the building ground through a plurality of separate and distinct gas discharge tubes in which a breakdown on at least one of the multi-phase lines will not cause a breakdown on any of the other multi-phase power lines.  
         [0003]     The Hoopes patent, however, does not disclose a building entrance power meter-base multi-phase surge protector in which each multi-phase power line is connected, at the building entrance, to a neutral line through an MOV in series with a single GDT, wherein each MOV is connected to an electrode of the GDT and a separate electrode of the GDT is connected to the neutral line. The Hoopes patent also does not disclose a device that monitors the voltage status of the surge protector circuit, or sub-circuits, to determine a protector malfunction and displays a non-surge protection condition.  
         [0004]     In addition, the Hoopes patent discloses a thermal fuse connected between each of the MOVs and their respective AC power line to limit surge voltage. One distinct disadvantage of thermal fuses is that once they have been disabled they must be replaced. Although the Hoopes patent teaches the use of multiple thermo fuses to protect each AC power line, the surge protector disclosed thereby is only functional for a limited number of over voltage occurrences.  
         [0005]     Another type of surge protector is shown in U.S. Pat. No. 4,455,586, entitled, “High Voltage Filtering And Protection Circuit”, issued Jun. 19, 1984, to Thomas McCartney, and assigned to ONEAC Corporation, Bannockburn, Ill., hereinafter referred to as “the McCartney patent”. The McCartney patent discloses a multi-phase surge protection circuit connecting each AC power line and neutral line to ground via various protection circuits. In one embodiment of the McCartney patent, each AC power line and the neutral line is connected to ground via a series of two protection circuits made up of transient voltage suppressors, such as, high voltage rated silicon p-n junction devices, in parallel with capacitors. In another embodiment of the McCartney patent, an arrangement formed using a series of transient voltage suppressors in parallel with a series of capacitors is utilized to connect the AC power lines to ground. A further embodiment of the McCartney patent uses parallel transient voltage suppressors directly connected in series with a common transient voltage suppressor that is connected in series with a gas discharge tube. An additional embodiment of McCartney utilizes parallel bi-directional transient voltage protectors directly connected to a common bi-directional transient voltage protector that connects to ground via a gas discharge tube.  
         [0006]     Still another type of surge protector is shown in U.S. Pat. No. 5,428,494, entitled, “Power Line Protector, Monitor And Management System”, issued Jun. 27, 1995, to Om Ahuja, and assigned to Omtronics Corporation, Bellaire, Tex., hereinafter referred to as “the Ahuja patent”. The Ahuja patent discloses a multi-stage, multi-function power line based power protection, monitoring, and management system, which includes over voltage protection utilizing a three-electrode GDT, MOVs for providing line to ground and line to line transient protection and voltage limiting across the line connected equipment, ground fault circuit interrupter, fuses, and positive temperature coefficient resistors integrated with the GDT, MOV, and transient suppressor. The Ahuja patent also includes a stage that includes, for example, a microcontroller, or microprocessor, that continually monitors and responds to power line and power load conditions, and in accordance with other predetermined internal/external hardware or software conditions switching on or off power sources or other loads.  
         [0007]     Neither the McCartney patent nor the Ahuja patent discloses a building entrance power meter-base multi-phase surge protector in which each multi-phase power line is connected, at the building entrance, to a neutral line through an MOV in series with a single GDT, wherein each MOV is connected to an electrode of the GDT and a separate electrode of the GDT is connected to the neutral line. Likewise, neither the McCartney patent nor the Ahuja patent discloses a device that monitors the voltage status of the surge protector circuit, or sub-circuits, to determine a protector malfunction and displays a non-surge protection condition.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention overcomes the disadvantages of the prior art surge protectors as exemplified by the patents already discussed. The present invention discloses a meter-base surge arrestor/protector that mounts between a residential meter and meter base at the building entrance. The present invention discloses a novel and improved building entrance power meter-base multi-phase surge protector in which each multi-phase power line is connected at the building entrance to a neutral line through an MOV in series with a single GDT, wherein each MOV is connected to an electrode of the GDT and a separate electrode of the GDT is connected to the neutral line. The GDT and MOV combination surge protector circuit of the invention has a reduced capacitance, which enables high speed broadband data transmission over power lines without significant attenuation, and leakage current though the MOVs is reduced ensuring a long service life for the meter-base surge protector.  
         [0009]     The GDT and MOV combination surge protector circuit also includes thermal cut-offs (TCO) connected in series and thermal communication with the MOVs. The use of TCOs in lieu of fuses allows the surge protector to operate at higher temperatures and loads. Each TCO is physically positioned within the surge protector circuit so as to be in at least thermal communication with its respective MOV. Such thermal communication includes any relative physical positioning between the TCOs and the MOVs that allows heat dissipated by the MOVs to be received by the TCOs, including placement of the TCOs in actual physical contact with the MOVs. With this arrangement, heat buildup in the MOVs will be distributed to the TCOs.  
         [0010]     The present invention overcomes the functional limitations of the prior art fuses by utilizing TCOs which protect the surge protector circuit through an increase in resistance with an increase in temperature. During a surge condition that exceeds the electrical capabilities of the surge protector of the present invention, the TCOs will eliminate current flow therethrough due to excessive heat build-up in the TCO. When the excessive surge condition has subsided, current flow is reestablished through the TCOs once the TCOs have cooled to an operating temperature.  
         [0011]     The GDT and MOV combination surge protector circuit of the present invention also includes a microcontroller, or microprocessor, for monitoring the voltage status at various monitoring point locations within the surge protector circuit itself to determine whether or not the surge protector circuit is providing surge protection. The microcontroller receives negligible operating power via the AC power lines. In the event one or more of the components of the surge protector circuit fails, or otherwise malfunctions, the microcontroller will sense a voltage status change at one or more of the monitoring points within the circuit and signal the premises owner, via a blinking light emitting diode, audible alarm, or other warning mechanism, that surge protection has been interrupted and is currently not available. The microcontroller also sends low frequency signals over the power lines, or other means, to alert the power utility of the surge protection circuit failure or malfunction.  
         [0012]     The foregoing specific objects and advantages of the invention are illustrative of those that can be achieved by the present invention and are not intended to be exhaustive or limiting of the possible advantages which can be realized. Thus, these and other objects and advantages of this invention will be apparent from the description herein or can be learned from practicing the invention, both as embodied herein or as modified in view of any variations which may be apparent to those skilled in the art. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The accompanying figures illustrate the details of the preferred meter-base surge arrestor/protector of the present invention. Like reference numbers and designations used herein refer to like elements.  
         [0014]      FIG. 1  is a schematic diagram of the surge protector circuit in accordance with an embodiment of the present invention;  
         [0015]      FIG. 2  is a partial schematic diagram showing the physical proximity of a thermal cut-off and a metal oxide varistor in accordance with an embodiment of the present invention;  
         [0016]      FIG. 3  is a longitudinal view of the gas discharge tube in accordance with an embodiment of the present invention;  
         [0017]      FIG. 4  is a block diagram of the microcontroller in accordance with an embodiment of the present invention; and  
         [0018]      FIG. 5  is a flow diagram of the surge protector circuit monitoring method in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]      FIG. 1  is a schematic diagram of surge protector circuit  100  of the present invention. Surge protector circuit  100  includes conductors  110 ,  111 , and  112  that are respectively adapted to be connected, via building power meter  113 , to AC power line  114 , AC power line  115 , and neutral line  116 . Conductor  110  is connected to first TCO  120 , which is connected in series with first MOV  130  and first electrode  142  of three-electrode GDT  140 . Conductor  111  is likewise connected to second TCO  120 , which is connected in series with second MOV  130  and second electrode  144  of three-electrode GDT  140 . Any arrangement and number of AC power lines, conductors, MOVs, TCOs, electrodes and GDTs may be utilized in the invention in order to achieve the functions and advantages stated herein.  
         [0020]     As shown in  FIG. 2 , the TCOs and MOVs are physically positioned in proximity, or physical contact, with one another so as to allow heat generated and dissipated by for example MOV  130  to be distributed to for example respective TCO  120 . The proximity of TCO  120  and MOV  130  allows TCO  120  to monitor and react to heat build up in respective MOV  130  and, more particularly, excessive heat build up in MOV  130 . Suitable TCOs are available as Microtemp Thermal Cutoffs made by Thermodisc, Incorporated, 1320 South Main Street, Mansfield, Ohio, 44907-0538, under part number G4A01084C. Suitable MOVs are available from MAIDA Development Company under part number ZV0181 RA  630 , which have a breakdown voltage of about 300 volts and a maximum clamping voltage of about 465 volts.  
         [0021]      FIG. 3  illustrates an exemplary gas discharge tube  140  suitable for use in the invention. Gas discharge tube  140  has three electrodes, one on each end and one disposed between the end electrodes, for example, in the middle of gas discharge tube  140 . Any number or arrangement of electrodes can be utilized in the invention. Gas discharge tube  140  may preferably have a length  147  of approximately 1.75 inches and width  148  of approximately 0.335 inches and may include any number of electrodes, preferably, at least three electrodes. The dimensions of the gas discharge tube are preferably substantially larger than the dimensions of prior art gas discharge tubes utilized in surge detectors in order to accommodate higher surge currents, preferably, at least as high as 40 KAmps. A suitable GDT may be a TII 31 D gas tube, which is available from TII Network Technologies, Inc., Copiague, N.Y., and has a breakdown voltage in the range of 350 volts to 600 volts.  
         [0022]     The unique configuration of the surge protector circuit of the invention wherein each AC power line is connected at the building entrance to a neutral line through an MOV in series with a single GDT, and wherein each MOV is in thermal contact with a TCO, enables high speed broadband data transmission over power lines to pass through without significant attenuation. The GDT and MOV combination surge protector circuit preferably has an effective capacitance as low as about 15 pF. In addition, the use of TCOs instead of fuses enables the surge protector of the invention to operate at higher temperatures and loads preferably greater than 20 KAmps.  
         [0023]     The surge protector circuit  100 , as shown in  FIG. 1 , includes microcontroller  150  that is connected via conductor  151  to both the neutral line  112  and a third electrode  146  of three-electrode GDT  140 . A suitable microcontroller is microchip 12F629 available from DigiKey Inc., although other microcontrollers, or microprocessors, may be used. An LED  152  is included between the microcontroller  150  and neutral line  112 , as shown in  FIG. 1 , via conductor  151 . An LED  153  is also included between the microcontroller  150  and neutral line  112  via conductor  154 . Preferably, LED  152  may be red and LED  153  may be green, although other colors may respectively be used. Moreover, any number or arrangement of LEDs may be used in the invention.  
         [0024]     Microcontroller  150 , as shown in  FIG. 1 , receives power for operation via conductors  155  and  156 , respectively. Conductor  155  is connected between microcontroller  150  and AC power in line  115  up-line of TCO  120 . Conductor  156  is connected between microcontroller  150  and neutral line  112 . A central processing unit (CPU)  157  is included in the architecture of microcontroller  150 , as shown in  FIG. 4 , as well as an electrically erasable programmable read-only memory (EEPROM)  158 . CPU  157  of microcontroller  150  monitors the status of the voltage condition at a point between each of the serially connected TCO  120  and MOV  130 , through software applications stored in EEPROM  158 , and, provides visual, audio, and/or electronic signals as to whether or not the surge protector circuitry is providing surge protection. In this manner, microcontroller  150  provides the owner with a visual signal that surge protection is currently being provided by the surge protection circuit  100  or, when the surge protector circuit has experienced a malfunction, a visual, audio, or electronic signal to the owner and/or power utility that a malfunction has occurred and surge protection is not currently being provided. Once programmed, EEPROM  158  of microcontroller  150  can sustain the software for more than 40 years. Each conductor  157  and  158  connect microcontroller  150  to the monitoring point (MP) between each pair of serially connected TCO and MOV, as shown in  FIG. 1 .  
         [0025]     During operation of surge protector circuit  100 , microcontroller  150  draws negligible power from conductors  111  and  112  through conductors  155  and  156 , as shown in  FIG. 1 . Surge protector circuit  100  uses negligible power for operation. Microcontroller  150  continually monitors the status of the voltage condition at monitoring points MP located between each pair of serial connected TCO  120  and MOV  130 . In step  201  of  FIG. 5 , if CPU  157  of microcontroller  150 , via software modules stored in EEPROM  158  of microcontroller  150 , determines that the surge protector circuit is properly providing surge protection, then a signal is sent by CPU  157  to activate LED  153  in step  202  of  FIG. 3 . Activating LED  153 , which is visible on the outside of the surge protector, by, for example, a green light, provides a visible indication that the surge protector circuit is in a surge protection status and properly functioning.  
         [0026]     However, when surge protector circuit  100  experiences a malfunction, such as, for example, when one or more of the surge protector circuit components malfunction or completely fail, or otherwise fails to provide surge protection, microcontroller  150  detects a change in the voltage status at one or more of the monitoring points MP. During a malfunction, no surge protection along either, or both, of AC power lines in  114  and  115  may be available. In that instance, CPU  157  of microcontroller  150 , during step  203 , determines that no surge protection is available; a signal is sent in step  203  to activate the non surge protection status indicator, such as, for example, LED  152 , as shown in  FIG. 1 . In one embodiment, LED  152  is controlled to begin blinking a red light on and off at a rate of about two seconds on and one second off until the malfunction has been resolved or the surge protector has been replaced. The blinking LED  152  provides a visual indication that a malfunction has occurred and that surge protection is currently not available.  
         [0027]     In step  205  of  FIG. 5 , CPU  157  of microprocessor  150  transmits a non surge protection status signal to the power utility. The non surge protection status signal takes the form of a low power frequency signal that is transmitted to the power utility over the power lines connected to the surge protector circuit. Alternatively, the non surge protection status signal also includes a signal readable by way of electronic meter readers, or other visual indicators at the meter. Furthermore, surge protector circuit  100  may also include means for producing an audible alarm in a form of, for example, short audio beeps for audibly alerting the premises owner that a malfunction has occurred and that no surge protection is currently available. When the surge protector malfunction has been repaired, or a replacement surge protector has been installed, microprocessor  150  extinguishes the blinking red LED  152  and/or audio alarm and steadily illuminates the green LED  153  signifying that surge protection has been restored and is currently available. During a malfunction, or other non surge protection condition, the green LED  153  is extinguished in step  204 , as shown in  FIG. 5 .  
         [0028]     Although illustrative embodiments have been described herein in detail, it should be noted and understood that the descriptions and drawings have been provided for purposes of illustration only, and that other variations both in form and detail can be added thereupon without departing from the spirit and scope of the invention. The terms and expressions have been used as terms of description and not terms of limitation. There is no limitation to use the terms or expressions to exclude any equivalents of features shown and described or portions thereof.