HK1018868A - Non-invasive powerline communications system - Google Patents

Description

Non-invasive powerline communication system

The present invention relates to power line communication systems and, more particularly, to such a system for coupling communication signals between a communication device and a power line in a substantially non-intrusive manner by reactively coupling signals to and from the power line.

The present invention is a continuation-in-part application entitled "molded-core, self-powered powerline sensor" filed by the present inventors on even date herewith.

It is a useful practice for power companies to monitor conditions in or around the ac power line for both overhead and underground applications and for primary and secondary applications in anticipation of power outages due to equipment failure and overload on the ac power line, as well as power outages that may cause power loss to a large number of users. The likelihood of powering down and losing the largest number of users increases during peak load when power usage is at a maximum and continuous power transmission is most critical. The restoration of outages caused by lines, transformers and other equipment is expensive, presents a hazard to utility employees, and can be costly to the utility in terms of lost power, lost revenue, and reputation damage. If the power line is an underground line, the effects of an unexpected power outage caused by a power line fault or overload are more severe.

Therefore, in order to better anticipate the potential for an unexpected power outage due to equipment failure and overload, ac power line sensors that sense electrical conditions such as power, voltage and current are very useful for utility companies to monitor ac power lines and associated equipment such as transformers and switches. If power companies are able to monitor conditions on the power line, they are better able to service and replace power lines that may become blacked out due to overload or failure, thereby reducing the number of unexpected power outages.

To most effectively perform such monitoring, communication links are typically established between the sensors on the monitored system and a remote base station. This allows the utility company to monitor all of its sensors at a remote location rather than having to individually check each sensor locally. One way of establishing a communication line is by transmitting signals to a local earth station, for example using a frequency modulated radio communication line. The signals are then transmitted, for example, by radio, land line or satellite channels to a remote central monitoring location. See U.S. patent No.4,786,862 to Sieron. Such communication lines are complex, expensive, and require the use of a large amount of hardware.

A better approach involves transmitting high frequency communication signals between the sensors and the base station using the monitored power line. This is accomplished by making direct electrical connections between the sensors and the power lines and the base station and the power lines. However, direct electrical connections require invasive electrical connections to be made to the monitored circuitry. Because it requires a large number of people to install, such installations are expensive to the utility company, can be dangerous to the installer, and can cause a power outage to the customer. Due to these limitations, power line communication has not been widely used in the power industry for communicating with power line sensors.

It is therefore an object of the present invention to provide a power line communication system that non-invasively couples communication signals to and from a power line.

It is a further object of this invention to provide such a non-intrusive powerline communication system that does not require a direct electrical connection to the powerline.

It is a further object of this invention to provide such a non-intrusive powerline communication system that is very easy, inexpensive and safe to install on a powerline.

It is a further object of this invention to provide such a non-intrusive powerline communication system that can be installed without causing a power outage to the user.

It is a further object of this invention to provide such a non-intrusive powerline communication system which requires less hardware than prior systems which do not perform powerline communication because it transmits communication signals using the monitored powerline.

The present invention is formed by the realisation that a truly simple, safe and inexpensive power line communication system can be realised by providing means for generating a communication signal for transmission over a power line at a first location, reactively coupling the generated communication signal to the power line, and receiving the communication signal at a second location.

The invention features a non-intrusive powerline communication system. The system includes means for generating a communication signal at a first location for transmission over a power line. There is a means for reactively coupling the communication signal to the power line and a means for receiving the communication signal at a second location, such as a base station.

In a preferred embodiment, the generating means may comprise first communication means. The reactive coupling means may comprise means for inductively coupling the communications signal to the power line. The inductive coupling device may include a communications core element disposed about the power line and a plurality of windings disposed about the communications core element to couple the communications signal to the power line.

The reactive coupling means may comprise means for capacitively coupling the communication signal to the power line. The capacitive coupling device may also include a capacitor having first and second partitions disposed proximate the power line and a dielectric disposed between the partitions to capacitively couple the communication signal to the power line. The first and second plates of the capacitor may be arranged coaxially around the power line.

Means for reactively (inductively or capacitively) coupling the communication signal from the power line to the base station may also be included. There may also be means for reactively (inductively or capacitively) coupling the communication signal generated by the base station back to the power line for transmission to the first location. There may also be means for reactively (inductively or capacitively) coupling the base station signals to the first location.

The invention also features a non-intrusive powerline communication transmitter that includes means for generating a communication signal for transmission over a powerline and means for reactively coupling the communication signal to the powerline.

The invention also features a non-intrusive powerline communication receiver for receiving a communication signal transmitted over a powerline. The receiver includes means for receiving a communication signal transmitted over the power line, and means for reactively coupling the communication signal from the power line to the receiver.

Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:

FIG. 1A is a three-dimensional view of a modular core, self-powered powerline sensor in accordance with the present invention;

FIG. 1B is a schematic drawing depicting the winding interconnections of the molded core element of FIG. 1;

FIG. 1C is a three-dimensional view of a sensing device of the modular core, self-powered powerline sensor of FIG. 1A;

fig. 2 shows the modular core, self-powered powerline sensor of fig. 1, wrapped around with a protective cover and having electronic components arranged between the protective cover and the sensor winding.

FIG. 3 is a schematic block diagram of both the sensor and base station of FIG. 1 coupled to an AC power line; and

fig. 4 is a flow chart of software that may be used by the microcontroller of fig. 3 to establish a time-based nominal level for a sensed condition in or around the ac power line to determine a change in or around the ac power line from the nominal condition.

Fig. 1A shows a modular core, self-powered powerline sensor 10 arranged around an ac powerline 12 in accordance with the present invention. The power line 12 includes a conductive strand (or single core) 14 and an insulating rubber layer 16. The illustrated ac power line 12 is a cable of the type typically used in underground secondary power distribution applications; however, this is not a necessary limitation of the present invention, as the sensor 10 can be used for overhead secondary voltage applications with insulated or non-insulated cables, as well as overhead and underground primary voltage applications.

The sensor 10 comprises low profile moulded core elements 18,20 and 22 arranged around the power line 12 by pushing open gaps 19,21 and 23 therein to mount the core elements on the power line 12 and then resiliently returning the gaps to their original positions to secure the core elements in position. The core element is formed of a high permeability ferromagnetic material, such as steel, and is typically encased in an insulating material.

The core elements 18,20 and 22 are annular in shape and have a cross-sectional thickness T approximately equal to their width W, typically approximately 1/2 inches. Thus, as previously described, they are approximately configured to most efficiently extract power from the ac power line 12. As also previously described, for a single core system, in order to improve the amount of power extraction from the ac power line, the width of the core must be increased and its cross-sectional thickness must be increased commensurately to maintain efficiency. However, increasing the cross-sectional thickness to maintain efficiency makes the cross-section of the sensor very thick and prohibits its use in confined volumes and on closely spaced lines. According to the invention, the core consists of several, in this case three, moulded core elements. This maintains efficiency by having the core elements have a cross-sectional thickness approximately equal to their width, and by using several core elements, the cross-sectional thickness of the sensor can be limited to maintain a low profile while allowing increased power extraction.

The size of the core elements 18,20 and 22 that optimizes power extraction is a combination that minimizes losses while maximizing coupling between the multiple windings on the core (secondary windings) and the power line cable passing through the center of the core (primary windings).

The three fundamental losses observed in practice are those caused by the resistance of the secondary winding, those caused by the induction of leakage flux, and those caused by the induction of eddy currents in the core material. Other losses are present and they may affect performance to a greater or lesser extent depending on design details. However, the three losses mentioned above are the major losses observed.

In a test embodiment of the sensor, the core comprises a design made of tape wound magnetic steel material. By tape winding is meant that the core is made by spirally winding a continuous strip of steel to form a loop much like a coil of co-tape. The advantage of this manufacturing method is that it is relatively easy and inexpensive, and it allows the use of magnetic steel that is preferentially oriented so that the maximum permeability is in line with the length of the steel strip. When the steel strip so oriented is wound in a toroid, the maximum permeability is approximately arranged in a loop along the toroidal core. Thus, the maximum permeability path is in line with the path of the magnetic flux created by the flow of current in the primary conductor through the toroidal core. If the tape wound core is made of a magnetic material coated with an electrically insulating layer, the material will form a core structure that effectively restricts eddy current flow in the path directed radially outward from the center of the primary winding through the core. However, such a configuration does not tend to restrict eddy currents flowing in paths in the core parallel to the primary winding, and eddy currents induced in the core by the primary winding current will tend to follow these parallel paths. Irrespective of other issues, if a toroidal core can be electrically divided into a plurality of side-by-side cores to provide an open circuit in the core eddy current path parallel to the primary winding, these eddy currents will be significantly reduced with their associated losses (reactive power).

The cross section of the core can be optimized to minimize losses and maximize coupling between the primary and secondary windings. The typical core has an inner diameter R₁Outer diameter R₂And a width W. Core cross-sectional thickness T of R₁And R₂The difference between, namely:

T=R₂-R₁ (1)

the coupling between the primary and secondary windings may be characterized by the number of flux turns in the core. The secondary winding resistance and leakage inductance may be characterized by the length of each secondary band on the core or the length of the perimeter of the core cross-section (2T + 2W). The core size can be optimized by maximizing the number of flux turns and minimizing the core cross-sectional perimeter. For the expected size range of the sensor, the optimal core size requires a ratio of W to T (W/T) in the approximate range of 1 to 3. As noted, the experimental embodiment of the sensor utilizes three cores 18,20 and 22, each having a W/T ratio of approximately 1.

By winding a wire, such as 28 gauge magnetic wire, in a number of turns around each core element 18,20 and 22 and interconnecting the windings of each core element in series as shown in fig. 1B, a winding layer is formed comprising windings 24,26 and 28. Alternatively, the windings may be connected in parallel. The ac power in the power line 12 induces currents in the windings 24,26 and 28 by the contactless transformer action. The appropriate winding ratio is selected so that when the ac power line 12 is energized, the desired current will be induced in the windings. The number of winding turns determines the ratio between the current induced in the winding and the current in the alternating power line 12 to the extent that the core elements 18,20 and 22 contain an induced magnetic flux density equal to or less than their saturation level. For line currents as small as 20 amps, a typical number of windings for each core element is 75 in order to extract enough power to operate the sensor 10. By increasing the number of core elements or windings, or both, the sensor 10 can be made to extract more power and thus be able to operate at even smaller ac currents.

The sensor 10 also includes the voltage and current sensing device 36 of fig. 1A and 1C. The voltage is sensed by a capacitor 37 having a first inner surface conductor 38 adjacent the insulating layer 16 of the ac power line 12 and an outer surface conductor 40 spaced from the inner conductor 38. The two conductors are arranged coaxially around the ac power line 12 and contain a dielectric 42, such as air or a foam core, between them. The capacitor 37 is used to sense the voltage capacitively coupled from the ac power line 12, which is proportional to the voltage of the power line 12, and as described below, serves as a receiver to capacitively couple high frequency power line communications from the power line 12. Because capacitor 37 is arranged coaxially around power line 12, it tends to counteract the effects of power in multiple power lines that may be near power line 12, rather than in power line 12.

To further reduce noise and/or unwanted effects of external magnetic fields, such as those generated by adjacent power lines or other sources of electromagnetic fields, the inner surface conductor 38 is electrically connected to additional coaxial plates 39 and 41, the plates 39 and 41 being spaced externally of the plate 38 in the same manner as the plate 40 and with the same dielectric between the plates 39 and 38 and the plates 38 and 41. The additional plates 39 and 41 each have approximately half the surface area of the outer coaxial plate 40 and are electrically connected to the inner coaxial plate 38 as shown. Thus, any external signal will tend to be picked up equally by both the inner and outer coaxial plates 38, 40 and no differential measurement is exhibited between the inner and outer surface conductors 38, 40. There may be only one coaxial plate, such as plate 39, which has the same surface area as outer plate 40. Alternatively, there may be three coaxial plates, each having one third of the surface area of the outer plate 40. Generally, if there are n plates, the surface area of each plate is 1/n of the surface area of outer plate 40.

Around the capacitor 37 is arranged an inductor 43 with a number of current measuring windings 44 wound around a ring-shaped separation material (e.g. foam) 45. The current of the ac power line 12 induces a current in the winding 44 that is proportional to the current flowing in the ac power line 12. Because the inductor 43 is wrapped around a separate material 45 containing air or foam, it does not become saturated as with a typical iron core. The sense current is therefore more linearized, making it more accurate and easier to interpret.

The separating material 45 contributes to the shape of the winding 44 and its material has a low permeability like air. The separation material 45 may have a higher magnetic permeability, but care must be taken to include a gap or control the magnetic permeability so that the material of the shape 45 does not become magnetically saturated and the current sensed by the inductor 43 becomes less linear and harder to interpret. The non-linearised current measurement can be sensed and accurately interpreted by the inductor 43, however this requires a somewhat greater complexity for the other components of the sensor.

The voltage and current sensing device 36 also includes a gap 46 formed therein to allow the sensing device to be installed on the ac power line 12 or removed from the ac power line 12. Although the voltage sensor device (capacitor 37) and the current sensor device (inductor 43) of the voltage and current sensing device 36 are shown as being arranged at the same location around the power line 12, this is not a necessary limitation of the present invention. They may be arranged close to each other or even spaced apart from each other.

The communication device 48 is comprised of a communication core element 50 and a plurality of windings 52 wound around the core element 50 to transmit communications from the sensor 10 noninvasively to the ac power line 12 by contactless transformer action. Preferably, the communication device 48 functions as a high frequency communication transmitter and the capacitor 37 of the sensor 36 functions as a high frequency communication receiver in addition to a voltage sensor. However, any one may be used to transmit or receive or both. Thus, non-invasive coupling for signal communication with a power line in accordance with the present invention can be described as reactive coupling to encompass both capacitive and inductive coupling techniques.

The sensor 10 typically includes a protective cover 62 that provides electrical insulation, as shown in FIG. 2. The cover 62 is typically formed of rubber and is secured to the windings with self-curing tape, adhesive, or other suitable means. Straps 63 and 64 removably secure power line sensor 10 in place about alternating current power line 12. The overlay 62 performs the additional function of effectively sandwiching the electronic components 66 mounted on the flexible printed circuit board 68 between it and the winding surface. The electrical connection between the winding (fig. 1B) and the electronic component is made by an electrical connection that is not visible in the figure but is schematically represented in fig. 3. The electronic components 66 include various types of sensors to sense virtually any phenomenon, such as temperature, pressure, radiation, humidity, etc.; a power source supplied by windings 24,26 and 28 (fig. 1), windings 24,26 and 28 being energized by a non-contact transformer action with ac power line 12; a microcontroller; as well as various other elements, which are discussed in more detail below with reference to fig. 3.

Although all of the electronic components depicted in fig. 2 are shown as being fixed to the flexible circuit board 68, this is not necessary as the sensors may be arranged off the circuit board 68 and sandwiched between the protective cover 62 and the windings, or the sensors may even be positioned outside of the protective cover 62 to sense certain types of phenomena around the outside of the protective cover 62.

A modular core, self-powered powerline sensor 10 is schematically depicted in the system 100 of fig. 3. The power of modular core, self-powered powerline sensor 10 is derived from the a.c. powerline 12 using windings 24,26 and 28. the a.c. powerline 12 can be a single phase powerline, which can be either individual or part of a polyphase transmission or distribution system, with windings 24,26 and 28 being shown as single windings in this figure for clarity. These windings are connected to a power supply 102 by wires 103 and 104, the power supply 102 being arranged on the flexible circuit board 68. The power supply 102 may be an ac to dc regulator integrated circuit that provides 5 vdc to the microcontroller 106, and it also provides 12V and +5V outputs that may be used by one or more sensors or other electronic components.

The microcontroller 106 may be an 8-bit embedded controller with an analog-to-digital converter. The sensors 108 and 112 are shown as being interconnected with the microcontroller 106, however, a different number of sensors may be used. The sensors 108 to 110 are arranged on the flexible circuit board 68, while the sensors 111 and 112 are arranged outside the protective cover 62 of fig. 2. Only one sensor, sensor 112, is powered by power source 102 because the remaining sensors do not require an external power source to operate. These sensors provide an analog or digital signal to the microcontroller 106 indicative of the particular condition sensed in or around the ac power line 12. In addition to these sensors, a capacitor 37 operating as a voltage sensor and an inductor 43 operating as a current sensor are shown.

Capacitor 37 is interconnected by lines 114 and 115 with signal conditioner 116, and signal conditioner 116 performs amplification and filtering of the sensed signal to match the input requirements of microcontroller 106. The signal of the voltage sensor 37 is a capacitively coupled voltage representing the instantaneous voltage on the ac power line 12. Because there is no reference voltage, the voltage sensor 37 does not provide an absolute voltage reading to the microcontroller 106. However, by monitoring the instantaneous voltage level provided by capacitor 37 over a period of time, an average or nominal voltage level can be determined, and after the nominal level is established, the change from the nominal voltage level can be resolved by the instantaneous input provided by capacitor 37. The microcontroller 106 may perform other statistical calculations, such as weighting, on the non-reference voltage input signals and may determine the deviation from these other types of statistical determinations.

Current sensing is performed by an inductor 43, and the inductor 43 induces a current that is proportional to the ac line current in the power line 12. The sensed current is then provided to a current pickup signal conditioner 117, which amplifies and filters the signal before it is provided to the microcontroller 106.

Sensors 108 and 110 are disposed on flexible circuit board 68 and sensors 111 and 112 are disposed on the exterior of protective cover 62. These sensors may sense, for example, temperature, pressure, gas, humidity, radiation or light (visible or infrared). In fact, sensors that actually sense any phenomenon may be utilized. Some sensors, such as temperature sensors or radiation sensors, may be mounted directly on the flexible circuit board 68, while other sensors, such as sensors 111 and 112, operate only under the exterior arranged in the protective cover 62, such sensors sensing gases and light, for example.

The sensors 108 and 112 and the voltage and current sensors 36 continuously sense various conditions in or around the ac power line 12 and provide analog or digital signals representative of these sensed conditions to the microcontroller 106. If necessary, the controller 106 converts the signals provided by the sensors into digital signals, and the controller 106 then generates communication data representative of the sensed conditions, and this data is provided over line 118 to power line carrier electronics 120, which encodes the data. The power line carrier electronics 120 then provides the encoded data to the output exciter 112, which sends low voltage, high current pulses to the windings 52 of the communication device 48 to non-invasively couple the transmissions of the microcontroller 106 of the sensor 10 to the ac power line 12 via a contactless transformer action. To locally sense the condition of the power line, a storage device 129 may be connected on lines 118 and 119. The storage device 129 is arranged at some convenient location near the power line.

Alternatively, as shown in dashed lines, the output of driver 122 may be provided to inner surface conductor 38 and outer surface conductor 40 of capacitor 37 of fig. 1 via lines 124 and 125, respectively. In this arrangement, the signal sent from the microcontroller 106 is capacitively coupled to the ac power line 12, and the exciter 122 must be configured to provide a high voltage, low current output pulse. It is presently preferred that the exciter 122 be configured to excite the windings 52 of the communication device 48. Driver 122 may be a high voltage amplifier (inverting or non-inverting).

The data transmitted by the microcontroller 106 includes an identification code identifying the power line sensor 10 and an identification code indicating the type of data transmitted to each individual specific sensor (108, 112, 37, and 43) on the power line 10. That is, the transmission includes information about the source of the transmission (many power line sensors may be used at various locations in the power distribution system of the utility company), as well as information about the type of data being transmitted, i.e., whether it is data about voltage, current, temperature, radiation, etc. The transmissions and identification codes and data of interest may occur on a regular basis, by time when a particular threshold is sensed, or by any desired criteria. The communication code may conform to a selected formal communication system specification or protocol. The protocol may be based on the OSI (open systems interconnection) reference model for communication proposed by ISO (international organization for standardization) Geneva, Switzerland. Any other communication code suitable for power line communication may be utilized.

The data transmitted by the sensor 10 is received by the remote base station 126. The base station 126 is interconnected with the power line 12 with direct electrical connections 127 and 128 connected to the power line 12 ', the power line 12 ' being part of a power distribution or transmission system power line and typically being either a ground line, a neutral line, or a power line that is out of phase with the power line 12 ' (in a polyphase system). However, the connection to the power line may be accomplished with a non-contact transformer action or capacitive coupling, as described above with respect to sensor 10. For example, inductor 43 'may be used to provide a connection to the power line through non-invasive inductive coupling and/or capacitor 37' may be used to provide non-invasive capacitive coupling. The transmitted data is provided to a computer 132 via a standard power line carrier modem 130 that matches the communication analog to digital of the sensor 10. The base station 126 is also capable of transmitting data from a computer 132 to the ac power line 12 via a power line carrier modem 130. Thus, for example, the base station 126 may query the molded core self-powered power line sensor 10 and any other power line sensors on the system for sensor information on demand, rather than passively waiting for the power line sensor to transmit. In addition, the power line sensors may be reprogrammed from the base station 126.

The coded communications transmitted by the remote base station 126 are preferably received by the capacitor 37 from the ac power line 12 with capacitive coupling. These high frequency communication signals are provided to high pass filters 134 and 136, pass them therethrough, and are provided to power line carrier electronics 120. The power line carrier electronics 120 decodes the communication signals and sends them to the microcontroller 106 via line 119.

Alternatively, the winding 52 of the communication device 48 may be used to receive communications from a remote base station 126. This is achieved by providing leads 138 and 139 (drawn in dashed lines) interconnecting the winding 52 with the high pass filters 134 and 136.

It should be noted that while it is preferred to use non-intrusive powerline communication between the sensors 10 and the base station 126, this is not a necessary limitation of the present invention. Direct contact power line communication or non-power line communication may be utilized, such as radio frequency, telephone line modem, cable television, cellular telephone, infrared, fiber optic cable, microwave, or ultrasonic communication.

The microcontroller 106 performs analog-to-digital conversion of sensed conditions, performs calculations and updates to memory locations storing previously sensed conditions, performs numerical operations such as determining running time averages and the like, tracks time for synchronization, and controls communication between the modular core self-powered powerline sensor 10 and the base station 126.

The microcontroller 106 can provide the base station 126 with the actual instantaneous value of a particular sensed condition, such as an actual temperature or radiation reading. However, it can also provide an indication to the base station 126 that the particular condition being sensed has changed from a nominal level, and the amount of such change. As briefly mentioned above, voltage sensing requires such data transmission because no sensing voltage can be compared to determine a reference level for an absolute voltage. Thus, the sensed voltage is compared to a nominal level and the change in the sensed voltage from the nominal level is determined and transmitted to the base station 126. The nominal level may be an average voltage level, or other types of statistical calculations may be performed on the sensed voltage data, such as weighting, and may be compared to the nominal level to determine changes from the nominal level. Furthermore, while this process is not required to be performed for all types of sensors (as many sensors provide absolute values of the sensed condition), it may be used for any condition being sensed. In fact, it may be more useful to provide a change in the nominal level relative to the sensed condition than to provide an actual absolute sensed value. This is because in many instances the monitored conditions are not monitored as actual values, but rather as changes from some nominal value.

To detect and transmit changes in the nominal level relative to the sensed condition, the microcontroller 106 operates according to the flow chart 150 of FIG. 4. At step 152, the modular core, self-powered powerline sensor is installed and the condition or conditions (e.g., voltage, current, temperature, radiation, etc.) are continuously and instantaneously acquired at step 154. At step 156, the instantaneous value of the sensed condition over time t is averaged over time, or other type of statistical calculation, such as weighting, is performed to determine the nominal level of the condition on the ac power line. At this point, the initial calibration is complete to the extent that the desired type of statistically calculated nominal levels has been determined. The calibration process may be performed anywhere from a few seconds to weeks or even months to obtain an accurate nominal level reading. After the initial calibration process is complete, the instantaneous value obtained in step 154 is compared to a nominal level in step 158. After the initial nominal level is determined, it is continuously recalculated from the new instantaneous sensor data. At step 160 it is determined whether the instantaneous value has changed from the nominal level and if so, a signal is sent to the remote base station indicating the change and the extent of the change at step 162. Regardless of whether a change is detected, the system returns to step 154 to obtain another instantaneous value, and the process continues until the sensor is removed from the ac power line or determination of the particular condition being sensed is no longer required.

Thus, the capacitor 37 of fig. 1 and 3 performs the following functions. First, the capacitor 37 is used to sense the voltage on the power line. Second, capacitor 37 is used to reactively couple the communication signal to the power line. Third, the capacitor 37 is used to transfer the signal reactive transmitted by the base station 126 to the microcontroller 106. Finally, a capacitor 37' disposed proximate the base station 126 is used to reactively receive the communication signal from the sensor 10 and transmit the communication signal from the base station 126 back to the sensor 10.

The inductor 43 operates in a similar manner. It is not only capable of sensing the current on the power line, but it is also capable of reactively coupling the communication signal to the power line for transmission to the base station 126. The inductor 43' also serves to reactively receive communication signals from the sensor 10 and transmit signals from the base station 126 to the sensor 10.

Although the power line communication system described with respect to the preferred embodiment is related to sensed conditions in or around the ac power line, the present invention is not limited to non-intrusive sensor data transmission and reception. Of course, the non-intrusive powerline communication system of the present invention can be used for any type of powerline communication.

Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention.

Other embodiments will occur to those skilled in the art and are within the following claims.

Claims (37)

1. A non-intrusive powerline communication system, comprising:

means for generating a communication signal at a first location for transmission over a power line;

means for reactively coupling a communication signal to the power line; and

means for receiving the communication signal at a second location.

2. The non-intrusive powerline communication system of claim 1 in which said means for generating includes first means for communicating.

3. The non-intrusive powerline communication system of claim 1 in which said reactive coupling means includes means for inductively coupling said communications signal to said powerline.

4. The non-intrusive powerline communication system of claim 3 in which said inductive coupling means includes a communications core element disposed about the powerline and a plurality of windings disposed about said communications core element for coupling said communications signal to said powerline.

5. The non-intrusive powerline communication system of claim 1 in which said reactive coupling means includes means for capacitively coupling said communication signal to said powerline.

6. The non-intrusive powerline communication system of claim 5 in which said capacitive coupling means includes a capacitor having inner and outer diaphragms disposed adjacent said powerline and a dielectric disposed between said diaphragms for capacitively coupling said communication signal to said powerline.

7. The communication system of claim 6, wherein the dielectric is air.

8. The communication system of claim 6 wherein said inner and outer bulkheads are coaxially arranged about said ac power line.

9. The communication system of claim 6, further comprising n additional boards electrically connected to said inner coaxial board to reduce noise.

10. The communication system of claim 9, wherein said n additional plate surface areas are each approximately 1/n of the surface area of said outer plate.

11. The communication system of claim 1 wherein said reactive coupling means comprises an inductor.

12. The non-intrusive powerline communication system of claim 1 in which said means for receiving includes means for reactively coupling said communication signal on said powerline at said second location.

13. The non-intrusive powerline communication system of claim 12 in which said reactive coupling means includes means for capacitively coupling said communication signal on said powerline.

14. The non-intrusive powerline communication system of claim 13 in which said capacitive coupling means includes a capacitor having inner and outer diaphragms disposed adjacent said powerline and a dielectric disposed between said diaphragms for capacitively coupling said communication signal to said powerline.

15. The communication system of claim 14, wherein the dielectric is air.

16. The communications system of claim 14, wherein said inner and outer bulkheads are coaxially arranged about said ac power line.

17. The communication system of claim 14, further comprising n additional boards electrically connected to said inner coaxial board to reduce noise.

18. The communication system of claim 17, wherein said n additional plate surface areas are each approximately 1/n of the surface area of said outer plate.

19. The non-intrusive powerline communication system of claim 12 in which said reactive coupling means includes means for inductively coupling said signal to and from said powerline.

20. The non-intrusive powerline communication system of claim 19 in which said inductive coupling means includes a communications core element disposed about the powerline and a plurality of windings disposed about said communications core element for coupling said communications signal to and from said powerline.

21. The non-intrusive powerline communication system of claim 1 further including means for extracting from said powerline said communication signal transmitted from said second location.

22. The non-intrusive powerline communication system of claim 21 in which said means for extracting includes means for reactively coupling from said powerline said communication signal transmitted from said second location.

23. The non-intrusive powerline communication system of claim 22 wherein said means for reactively coupling said communications signal transmitted from said second location from said powerline includes means for inductively coupling said signal transmitted from said second location from said powerline.

24. The non-intrusive powerline communication system of claim 23 in which said inductive coupling means includes a communications core element disposed about the powerline and a plurality of windings disposed about said communications core element.

25. The non-invasive powerline communication system of claim 22 in which said reactive coupling means includes means for capacitively coupling said communication signal transmitted from said second location from said powerline.

26. The non-intrusive powerline communication system of claim 25 in which said capacitive coupling means includes a capacitor having inner and outer diaphragms disposed adjacent said powerline and a dielectric disposed between said diaphragms.

27. The communication system of claim 26, wherein the dielectric is air.

28. The communications system of claim 26, wherein said inner and outer bulkheads are coaxially arranged about said ac power line.

29. The communication system of claim 26, further comprising n additional boards electrically connected to said inner coaxial board to reduce noise.

30. The communication system of claim 29, wherein said n additional plate surface areas are each approximately 1/n the surface area of said outer plate.

31. The non-intrusive powerline communication system of claim 1 further including means for encoding said communication signal.

32. The non-invasive powerline communication system of claim 4 in which said inductive coupling means further includes exciter means for providing low voltage, high current pulses of said communication signal to said plurality of windings to inductively couple said pulses to said powerline.

33. The non-intrusive powerline communication system of claim 1 further including a memory device proximate said first location.

34. The non-intrusive powerline communication system of claim 33 further including means for transmitting said communication signal to said storage means.

35. A non-intrusive powerline communication transmitter, comprising:

means for generating a communication signal for transmission over the power line; and

means for reactively coupling the communication signal to the power line.

36. A non-intrusive powerline communication receiver that receives a communication signal transmitted over a powerline, comprising:

means for receiving a communication signal transmitted over a power line; and

means for reactively coupling a communication signal from a power line to the receiver.

37. A non-intrusive powerline communication system, comprising:

a sensor for sensing a condition of the power line;

a base station remote from the sensor;

means for reactively coupling signals from the sensors to the power line for transmission to a remote base station;

means for reactively coupling said signal transmitted on said power line from the power line to a remote base station;

means for reactively coupling signals generated by the base station to the power line; and

means for reactively coupling a signal from a base station on a power line to a sensor.