Electricity: electrical systems and devices – Safety and protection of systems and devices – Transient responsive
Reexamination Certificate
2000-12-15
2003-04-15
Leja, Ronald W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Transient responsive
C361S127000
Reexamination Certificate
active
06549388
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to electric power service to homes and buildings and, more specifically, to overvoltage and/or overcurrent devices used with watthour meters mounted in watthour meter sockets at homes and buildings.
2. Description of the Art
Electrical power is supplied to an individual site or service by external electrical power line conductors located above or below ground. In a conventional arrangement, electrical power line conductors are connected to contacts in a watthour meter socket mounted on a building wall. Electrical load conductors are connected to another set of contacts in the meter socket and extend to the electrical distribution network in the building. A watthour meter is connected into the contacts in the meter socket to measure the electric power drawn through the load conductors.
Due to the current trend toward the use of plug-in watthour meters, A to S type socket adapters have been devised which convert A-base type bottom connected watthour meter sockets to receive plug-in watthour meters. Another type of socket adapter has been devised which allows the installation of other devices between the watthour meter socket and a plug-in watthour meter.
Such watthour meter socket adapters have also been provided with power disconnect devices, such as circuit breakers or ground fault circuit interrupters, both for protecting the electrical service as well as, in certain applications, to limit the amount of power supplied to the site. Such power disconnect devices may include an elongated plunger, the end of which extends outwardly through an opening in the annular side wall of the socket adapter when the circuit breaker is in the open or power disconnected position. The exposed end of the plunger can be pushed through the side wall of the watthour meter socket adapter to close the circuit breaker and to reapply power to the site. In certain of these devices, the ends of the plungers extending through the sidewall of the adapter have been colored red for high visibility of a tripped or open condition of the circuit breaker, etc.
Many older homes and buildings, even where originally wired with bottom connected watthour meters, have been converted by electrical utilities to socket style meters by the use of the above-described A to S socket adapter. This type of socket adapter does not require the existing wires to be moved which could cause the insulation which has become brittle with age to fall apart exposing the conductor. If this happens, the conductors and the socket itself need to be replaced which is a time consuming and costly process. This also creates further problems since the service entrance cables into the building should also be replaced and so on down the line through the distribution network as individual conductors are moved.
Currently, homes and buildings often have various electrically powered devices, such as a large number of appliances, computers, medical systems, video display systems, etc., which were not envisioned when the original distribution network conductors were sized to meet a particular maximum load at the time of the original installation. Older homes and buildings have been wired with smaller gauge wires, as small as #12 AWG, with up to and including #6 AWG also being common. The amperage usage in many of these systems exceeds the safe capacity of the individual wires or conductors. Further, due to the age of such wiring installations, the insulation on the individual wires typically is brittle and any movement of the wires for service upgrade could lead to the aforementioned deterioration or separation of the insulation from the wires which could lead to arcing between adjacent conductive elements and electrical fires.
One method to reduce fires in older installations where the insulation on the system wires is deteriorating is to prevent the system voltage levels from becoming too high and arcing. A socket type watthour meter has built-in surge air gaps will generally arc across the gaps at about 2,500 to 5,000 volts in the event of a voltage surge or transient thereby protecting the wiring system up to this voltage level. However, surge or transient voltages less than this level can often cause arcing between the building wires where the wire insulation has deteriorated. Once arcing begins, the arc itself can eventually form a conductive path and fault thereby creating a potential fire hazard. Of course, it is also important that voltage surges and transients be blocked from the distribution system to protect the electrical appliances and electronic devices attached thereto.
To address this problem, current limiting fuses and circuit breakers have been connected by wires between the load jaw contacts and load blade terminals in the socket adapter to create an open circuit at excessive amperage levels. Other surge voltage limiting devices have been connected between the line jaw contacts or blade terminals and ground to shunt voltage surges and transients to ground before such excessive voltages reach the watthour meter or load distribution network.
One such watthour meter base surge suppression system is disclosed in U.S. Pat. No. 5,023,747. In this device, a pair of surge suppressors in the form of metal oxide varistors are each connected to an electrical contact element which is in turn connected to the jaw contacts of a watthour meter socket. Voltage surges present on the blade terminals are conducted via the metal oxide varistors to respective fuses in the form of fusible links and then to ground to prevent the surges from being transmitted through the watthour meter and onto the electrical load distribution network. This surge suppression system also includes a diagnostic circuit which couples the varistors to an audible signal generator, such as a buzzer, which indicates that one of the fusible links has ruptured upon the occurrence of a line surge.
Such surge suppression systems have also been proposed with a visual indication that one of the fusible links or MOVs has opened due to the occurrence of a line surge. However, the surge suppression elements are mounted within the interior of a watthour meter socket adapter or socket and not visible exteriorly of the socket or socket adapter due to the need to sealingly enclose the watthour meter in the socket in order to prevent contact with the high voltage in the socket or to prevent tampering with and/or theft of electric power from the socket. Thus, unless an individual is within the vicinity of the socket adapter to hear the audible sound generator, the occurrence of an open circuit in the surge suppression device due to a line surge is not likely to be detected. Further, after the surge has passed and voltage and current levels have returned to normal, there is no indication the exteriorly of the socket adapter that one or more of the surge suppression devices is open and thereby not providing any surge suppression protection for the meter socket.
Small neon lamps have been mounted on the sidewall of the adapter or surge to indicate a change in state of the surge suppression devices. However, such lamps are prone to breakage and could leave unsafe, broken or disconnected electrical wires in the housing.
Thus, it would be desirable to provide the watthour meter socket adapter having a provision for providing a signal indicative of the opening of a surge suppression device within the socket adapter. It would also be desirable to provide the watthour meter socket adapter which provides an external visual signal to indicate that one or more of the surge suppression devices within the socket adapter has opened.
SUMMARY OF THE INVENTION
The present invention is an electrical service apparatus having surge suppression protection.
The electrical service apparatus, such as a watthour meter socket adapter, includes a housing having a hollow interior. A plurality of line and load jaw contacts are mounted in the housing for receiving the line and load blade terminals of a watthour meter. A p
Ekstrom Industries, Inc.
Leja Ronald W.
Young & Basile PC
LandOfFree
Electrical service apparatus with surge suppression protection does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrical service apparatus with surge suppression protection, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrical service apparatus with surge suppression protection will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3103489