Utility power restoration indicator for power management system

A system for indicating a power condition in a conductor includes an indicator constructed to provide notification to a user of a utility power condition, and a sensor non-electrically connected to a utility conductor to control operation of the indicator in response to detection of power in the utility conductor.

FIELD OF THE INVENTION

The present invention relates to a power indicator that provides an indication that primary power is being supplied to a load center. More particularly, the invention relates to a power indicator that determines the presence of primary or utility power to a load center without tapping into the current path between the primary power supply and the load center.

BACKGROUND OF THE INVENTION

A building typically has a load center or “breaker box” that distributes power from a primary power supply, such as a utility power supply, to various circuits within the building. The load center generally includes a main breaker, which selectively connects/disconnects the individual circuits or branches of the load center to/from the primary power supply. Increasingly, transfer panels or switches are being used so that critical or emergency circuits, such as those that feed power to water and waste management systems, refrigeration systems, and medical equipment, are sufficiently powered during interruption or failure of the primary power supply. The transfer panel, similar to the load center, will include individual circuits that are connected to the primary power supply through a transfer switch, similar in operation to the main breaker of the load center. During normal operation of the primary power supply, primary power is delivered to the circuits of the load center and the transfer panel. However, during interruption of primary power, the transfer switch disconnects the circuits of the transfer panel from the primary power supply and connects those circuits to an auxiliary power supply, such as an electric power generator.

Transfer switches are generally categorized as either manual transfer switches or automatic transfer switches. Automatic transfer switches automatically detect the interruption of primary power, automatically connect the critical or emergency circuits to the auxiliary power supply, and automatically initiate operation of the auxiliary power supply. Moreover, automatic transfer switches will automatically restore connection of the critical or emergency circuits to the primary power supply when primary power is restored and shut-down the auxiliary power supply. With manual transfer switches, the aforementioned steps are carried out manually by an operator.

Specifically, upon interruption of primary power, the main breaker must be manually disconnected or turned “OFF’ and the circuits connected to the auxiliary power supply. The main breaker is disconnected to prevent power generated by the auxiliary power supply from back-feeding through to the primary power supply. Thus, even when primary power has been restored, the load center remains disconnected from the primary power supply. As a result, the user, e.g., homeowner, is not readily made aware that primary power has been restored and that the auxiliary power supply can thereby be turned “OFF” or shut down and the circuits of the building may be reconnected to the primary power supply. Conventionally, to determine if primary power has been restored, a user must shut down the auxiliary power supply and reconnect the load center to the primary power supply. If the load center circuits are energized, primary power has been restored. If not, the user must then manually disconnect the load center from the primary power supply and reinitiate the auxiliary power supply to provide power to the transfer switch circuits, as described above. Unless the user is ostensibly aware that primary power has been restored, this technique can be hit-and miss, and therefore considerably inefficient.

Additionally, in many applications, the auxiliary power supply is a fuel-driven generator. Thus, if auxiliary power is used to power the critical or emergency circuits notwithstanding the restoration of primary power, the fuel-driven generator may be run much longer than needed thereby increasing its operational costs.

Therefore, there is a need for a device that detects primary power delivery to a load center and provides a suitable indication to a user. Such a device is particularly needed in the context of manual transfer switches in order to provide a signal to a user that primary power has been restored, that the auxiliary power supply may be shut down, and that the load center may be reconnected to the primary power supply.

SUMMARY OF THE INVENTION

The present invention is directed to a power indicator that overcomes the aforementioned drawbacks. In one aspect, the power indicator is electrically isolated from the circuits connected to the primary power supply, and signals an alert that primary power has been restored. The alert may include an audio alert or a visual alert. The power indicator is designed to sense the electromagnetic field around the wires that connect a load center to the primary power supply. Moreover, the electromagnetic field is sensed without direct contact with the current carrying components of the load center or the primary power supply. In one embodiment, the power indicator includes a coil of wire that is wrapped around a supply wire that connects the load center to the primary power supply. When the power indicator wire senses an electromagnetic field from a voltage at the supply wire, the power indicator provides an appropriate audio and/or visual alert signaling that primary power is available at the load center. In the context of an auxiliary power supply arrangement, the alert may signal a user that use of the auxiliary power supply may be terminated. Additionally, the power indicator may include circuitry for wirelessly communicating with a remote receiver that may be carried by a user or conveniently stationed remote from load center. This allows the user to be signaled that primary power is available at the load center without requiring the user to be proximate the load center. In one aspect, the power indicator is powered by a battery. The battery may also be a rechargeable battery that is charged by current induced in a separate sensing coil when the primary power supply is operational. Alternately, the power indicator may be powered by the auxiliary power supply.

Accordingly, in one aspect, the present invention is directed to a power indicator that senses primary power available at a load center without direct electrical contact with the current carrying components of the load center or the primary power supply.

In another aspect, the power indicator provides an audio or visual signal when primary power at the load center is sensed. In one embodiment, primary power at the load center is sensed by a coil wrapped around an input power line that provides primary power from the primary power supply to the load center.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be described with respect to a power indicator that may be used to sense power at a load, such as a load center or “breaker box” of a dwelling, building, or other structure. The power indicator will be described and shown as being independent of the load center; however, it is understood that the power indicator may be integrated with the load center. Moreover, it is contemplated that the power indicator may similarly be integrated with a transfer switch.

FIG. 1shows a load center10having utility conductors12,14that communicate power from a utility to load center10. Understandably, the number and size of utility conductors12,14will depend upon the amount of utility power intended or desired to be provided to load center10. A main breaker16electrically connects and disconnects utility conductors12,14from a series of load breakers18. Load breakers18electrically connect or disconnect respective load conductors20, which extend beyond a housing22of load center10to respective branches or circuits to which various electrical loads are connected, such as lights, outlets, electronics, and the like. Each of load breakers18includes an ON/OFF switch24, which is used to connect and disconnect load conductors20from utility conductors12,14. Main breaker16electrically connects and disconnects all of load breakers18from power communicated from utility conductors12,14. Similarly, each of load breakers18electrically connects or disconnects the associated load conductor20from power provided from utility conductors12,14. A generator breaker26electrically connects or disconnects generator conductors28,30from load center10.

During failure of utility power, operator manipulation of a main switch32associated with main breaker16electrically isolates utility conductors12,14from load center10. An interlock member, shown schematically at33, is positioned to maintain switch32in the OFF position, and the switches of generator breaker26, which are interconnected by a handle tie34, are then movable to the ON position so as to and electrically connects generator conductors28,30to load center10. In a manner as is known, interlock member33functions to prevent movement of main breaker switch33away from the OFF position while the generator breaker switches are in the ON position, to ensures that power provided from generator conductors28,30is not back-fed through utility lines beyond the building via utility conductors12,14. Depending in part upon the amount of power provided from generator conductors28,30, an operator may selectively configure load center10to provide power to critical loads, such as a furnace, sump pump, refrigerator, freezer or the like, by selective manipulation of switches24of load breakers18. Accordingly, a user can configure load center10such that the load demand does not exceed the power supplied across generator conductors28,30.

Load center10includes a power return indicator assembly40in accordance with the present invention, which is not electrically connected to the circuits of load center10. Power return indicator assembly40includes an indicator42, which indicates when utility power is communicated to load center10via utility conductors12,14. It is appreciated that indicator42be any of a visual, acoustical, vibrational, or other sensory indicator. Power return indicator assembly40includes a switch44, which allows an operator to turn power return indicator assembly40“ON” and “OFF”. A condition indicator46is connected to power return indicator assembly40and indicates a condition of the power return indicator assembly, such as being “ON” or “OFF”. Power return indicator assembly may also include an additional condition indicator56that indicates a battery condition. A threaded stem48of power return indicator assembly40passes through housing22of load center10and is engaged with a ring nut or the like to secures power return indicator assembly40to housing22. A sensor wire50extends from power return indicator assembly40through stem48, and is configured to be positioned in close proximity to one of utility conductors12,14. In the illustrated embodiment, sensor wire50is wrapped about utility conductor12.

In operation, during a power outage, an operator manipulates main switch32to electrically disconnect utility conductors12,14from load center10, and manipulates the switches of generator breakers26using handle tie34to electrically connect generator conductors28,30thereto. The user also turns “ON” power return indicator assembly40via switch44such that, when utility power is restored, sensor wire50senses such power restoration by sensing the electromagnetic field caused by the return of electrical power to utility conductor12when voltage is present in utility conductor12, thereby activating indicator42. Upon such an indication, a user can shut down the generator associated with generator conductors28,30and reinitiate the electrical connection of load conductors20with utility conductors12,14via actuation of main switch32. Such a construction is effective in reducing the operating time of the generator so that the generator is not operated for an extended duration beyond the restoration of power at utility conductors12,14.

FIG. 2shows power return indicator assembly40removed from load center10. A housing52encloses the majority of the components of power return indicator assembly40. A removable cover54is connected to housing52and encloses a battery (not shown). In one embodiment, the battery may be a rechargeable battery. Condition indicator46, preferably an LED, indicates that switch44is in an “ON” position and that power return indicator assembly40is thereby activated. An optional battery condition indicator56, preferably an LED, is also visible through housing52, and indicates when the batteries of power return indicator assembly40need to be replaced or recharged. Alternatively, indicator42could be configured to provide an audible alert of a specific tone, frequency, duration, or pattern that indicates a low battery condition. Switch44turns power return indicator assembly40both “ON” and “OFF” and also controls the volume of indicator42in an embodiment in which indicator42is an audible indicator.

Sensor wire50of power return indicator assembly40extends from housing52through stem48. A proximal portion58of sensor wire50is enclosed within a sheath60, which isolates the proximal portion58of sensor wire50. In this manner, the sheathed proximal portion58of sensor wire50prevents inadvertent tripping of power return indicator assembly40that otherwise may be caused by sensing of power distributed through load leads20when power is provided by generator conductors28,30. A distal tip portion62of sensor wire50is constructed to be positioned in close proximity to one of utility conductors12,14. As noted previously, the distal tip portion62of sensor wire50is wound about one of utility conductors12,14. The close proximity of tip portion62of sensor wire50to utility conductor12,14allows sensor wire50to sense the electromagnetic field created about the utility conductors12,14when power is present in utility conductors12,14. Accordingly, when sensor wire50senses or detects an electromagnetic field about utility conductors12,14, power return indicator assembly40activates indicator42thereby alerting a user that power is present in utility conductors12,14. With this construction, power return indicator assembly40, although physically connected to load center10, is not electrically connected to utility conductors12,14nor to any circuit of the circuits of load center10, yet functions to indicates the power condition of utility conductors12,14.

FIG. 3shows an exemplary circuit diagram of power return indicator assembly40. As shown inFIG. 3, switch44electrically connects a battery64to the circuitry of power return indicator assembly40, thereby arming a circuit66of power return indicator assembly40. During operation of power return indicator assembly40, circuit66detects the electromagnetic signal associated with power at utility conductors12and14using distal tip portion62of sensor wire50, which functions as an antenna, and activates indicator42upon such detection. Such a construction provides a non-contacting power return indication. It is recognized that other circuit configurations, using various electronic components different from those illustrated herein, may be used.

Referring again toFIG. 1, the power return indicator assembly40may optionally include circuitry (not shown) for wirelessly transmitting status information to a remote receiver (not shown). The power return indicator assembly40may include an antenna68coupled to a transmitter (not shown) that wirelessly transmits a signal to the remote receiver regarding the status of primary power restoration. This allows the user to be remote from the load center10yet still be apprized of the status of primary power at the load center. It is contemplated that the receiver may be a desk-top-type device or may be a portable-type device that the user may carry or affix to an article of clothing. It is recognized that other communication techniques may be used to provide status information directly to a user without requiring the user to be proximate the load center. For example, the power return indicator assembly40may be interfaced with a building's telephone system and include circuitry that automatically dials one or more telephone numbers when primary power is restored.

In one embodiment, the power return indicator assembly40has a battery to provide power to its internal circuitry. It is contemplated that the battery may be a rechargeable battery. It is also contemplated that the battery may be recharged by current induced in a split-core transformer (not shown) positioned near the utility conductor12. This allows the battery to be charged and connected to the power return indicator assembly40when utility power is present across utility conductor12.