The present invention relates to a power monitoring system and, more specifically, to a method of mounting a plurality of sensors of a power monitoring system in an electric power distribution panel.
Referring to
In many business environments a set of electrical loads, such as motors, lighting, heating units, cooling units, machinery, etc., may be electrically interconnected to one or more circuits, each of which may be a single phase or multi-phase. Obtaining the total power usage of the facility may be readily obtained by reading the power meter provided by the electrical utility. The utility's power meter is normally electrically interconnected between the power panel and the utility's transformer. In many circumstances, it is desirable to monitor the power consumption of individual loads or groups of loads. The use of power meters permits effective monitoring of the power consumption of particular loads. Also, a set of power meters permits effective sub-metering of different loads, buildings, or groups of loads to attribute and monitor the power usage of the business. For example, the power sub-metering may be used to attribute the power costs charged by the utility to different buildings, departments, or cost centers. The traditional approach to monitoring such power usage is to install a power meter at a location proximate the load itself. To install a typical power meter on a three phase load, a current sensor is located around each wire of the three phases and a voltage connection is electrically interconnected to each wire. Such a power meter is available from Veris Industries, LLC under the name H8035 Power Meter. Unfortunately, it is burdensome to interconnect a significant number of power meters and in particular the voltage connections to the wires, especially if an interconnection to the wires are not readily available. In addition, it is burdensome to interconnect the output of the power meters, if any, to a computer network because of the need to provide communication wiring or other wireless communication channels to each of the remotely located power meters. Also, installing the power meters requires significant expense for the technician to locate a suitable location near each device, in addition to the further expense of servicing the installed power meters.
What is desired, therefore, is a method for mounting a plurality of current transformers of a power monitoring system in an electric power distribution panel.
A power distribution panel provides a centralized location where the currents in the wires to several different loads and the voltages in the bus bars that correspond with the currents may be sensed, with both being readily available. Moreover, the voltage potential and phase relationship of the power is the same for each of the multiple different loads connected to a bus bar. In other words the power factor, a phase relationship between the voltage and current supplied to a load, may be determined based on the current to the particular load and the voltage in the respective bus bar. For a plurality of different loads the relationship between the respective currents/voltages and power factor may be determined using the same bus bars. This commonality of voltages among different loads may be used as the basis to simplify the power monitoring system. In particular, the power monitoring system may be substantially improved by sensing the voltage potential together with its phase from each of the bus bars, preferably using one and only one electrical interconnection for each phase. The voltage potential together with its phase relationship sensed from one or more bus bars may be used together with the respective sensed currents provided to the different loads to determine the instantaneous power usage and power consumed over a period of time for any particular load. In this manner, only a single interconnection for sensing the voltage potential is necessary for each phase for multiple loads, each of which may have one or more associated current sensors. The use of a single interconnection for sensing the voltage of each phase for multiple different loads decreases the time for installation, the cost of the power monitoring system, and decreases the likelihood of inadvertently misconnecting the voltage sensing connections. The use of a generally centralized location for sensing the voltage and current for several different loads potentially permits easier connection of the power monitoring system to a computer network for subsequent processing. Moreover, the centralized location reduces the cost by avoiding the need for a technician to locate a suitable location for the power meter for a particular load. Further, the servicing of the power meters is more readily done because of their proximity to one another.
Referring in detail to the drawings where similar parts are identified by like reference numerals, and, more particularly to
It takes considerable time to install, at significant expense, all of the individual current sensors 20 and the available space within the power panel 10 may be insufficient for the desired number of current sensors. Also, the limited space available along the circuit breakers 16 may result in significant difficulty installing the current sensors 20, thus requiring lateral spacing of the current sensors and bending the wires from the circuit breakers to different locations within the power panel 10 in an attempt to locate sufficient available space for the current sensors 20. In addition, the large number of wires 22 from the current sensors 20 to the power monitor 24 may require considerable space within the power distribution panel 10. Further, because of the significant number of individual wires 22 an installer has a significant tendency to interconnect the wires 22 to improper places within the power current monitor 24 and in particular to mismatch pairs of wires 22 from the same current sensor 20 rending the current sensors 20 ineffective. Moreover, it is problematic to ensure that the wires 22 indicated by the installer that relate to a particular current sensor 20 actually are interconnected to the desired current sensor 20. In summary, the potential installation problems are significant, especially when the power meter is installed by untrained technicians.
Referring to
The openings 64 defined by the sensors 60 are preferably oriented in a substantially parallel relationship with respect to each other and/or oriented in a substantially perpendicular relationship with respect to the longitudinal axis 66 of the support 62 or otherwise the general alignment of the sensors. Preferably, one set of the aligned sensors have a first linear arrangement and another set of the aligned sensors have a second linear arrangement, which may be parallel to each other. Also, preferably at least two of the aligned sensors have a first linear arrangement and at least two others of the aligned sensors have a second linear arrangement. A single aligned set of sensors 60 may be used or more than two sets of sensors 60 may be used, as desired.
Referring also to
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A sensor assembly may be located on both sides of a set of circuit breakers 16, if desired. Another sensor assembly is illustrated in
To provide effective monitoring of the power usage used by the loads, the power monitor 24 may monitor the current levels of each of circuit breakers 16 together with the associated voltage potential and phase relationship.
The power monitor 24 may likewise be used to monitor the load balance between the different phases of the power panel 10. Frequently, the circuit breakers may be interconnected to a single phase when the loads require 120 volts, interconnected to two phases when the loads require 240 volts, and interconnected to three phases when the loads require three phase power. For example, the first phase of the power panel 10 may be supplying 70 amps, the second phase of the power panel 10 may be supplying 30 amps, and the third phase of the power panel 10 may be supplying 150 amps. This significant imbalance in the current supplied by the different phases is sub-optimal. For example, the greater the current levels the greater the voltage drop from the power source to the power panel, which may result in significant variations in the voltage levels provided to the power panel from the three phase power source. Monitoring the current (or power) provided from each phase using the sensors enables redistribution of the loads between the different phases to re-balance the loads.
The detailed description, above, sets forth numerous specific details to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuitry have not been described in detail to avoid obscuring the present invention.
All the references cited herein are incorporated by reference.
The terms and expressions that have been employed in the foregoing specification are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.
This application claims the benefit of U.S. Provisional App. No. 61/285,106, filed Dec. 9, 2009.
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