BACKGROUND OF INVENTION Monitoring a. c. powerlines, in both overhead and underground and primary and secondary applications, is a useful practice for electric utility companies in order to anticipate outages which occur due to faulty equipment and overloads on a. c. powerlines and which result in loss of service for potentially a large number of customers. The potential for an outage and for the loss of the greatest number of customers is increased during peak periods when power usage is at a maximum and delivery of continuous power is most critical. Outages caused by faulty and overloaded lines, transformers and other equipment are expensive to repair, dangerous for utility company employees and costly to the electric utility company in terms of income lost for lost service and in terms of damage to the utility's reputation.

The effects of an unexpected outage as a result of a faulty or overloaded powerline are exacerbated if the powerline is underground. Replacing a damaged underground line requires more man hours and increased safety precautions due to the fact that the majority of work required occurs underground in cramped, sometimes wet, and always less than ideal conditions. As a result, repairing such a damaged underground line is even more costly, time consuming and dangerous.

Thus, a. c. powerline sensors which sense electrical conditions, such as power, voltage and current-are very useful to electric utility companies in monitoring a. c. powerlines and associated equipment such as transformers and switches, in order to better anticipate the likelihood of an unexpected outage occurring due to faulty and overloaded equipment. If the electric utility companies are able to monitor the conditions on the powerlines, they are better able to perform maintenance on and replacement of powerlines which are likely to become de-energized as a result of an overload or fault, thereby lowering the number of unexpected outages. By replacing and maintaining such equipment, the utility company can significantly decrease outage time to the customer. The costs associated with repair or replacement of damaged cables will also be decreased: the cost of replacing or repairing damaged, stolen, or compromised cables is often significantly greater in comparison to normal scheduled maintenance or replacement because of the overtime pay involved.

Accordingly, the significant body of work has been devoted to various powerline sensors but none have gained favor in the industry. For example, self- powered non-contacting powerline sensors do not always work reliably on low- voltage powerlines which may not provide enough power to supply the required electronic circuitry of the sensor usually including some kind of a microprocessor and transmitter. Examples of these self-powered powerline sensors include Chenier, U. S. Patent No. 4,831,327 which uses a Rogowski coil; Schweitzer, U. S.

Patent No. 4,794,329; Bubash, U. S. Patent No. 5,015,944; Sieron, U. S. Patent No. 4,786,862; Smith-Vaniz, U. S. Patent No. 4,808,916; Fernandez, U. S. Patent No. 4,801,937; and Schweitzer, U. S. Patent No. 3,428,896. These self-powered sensors do not always work reliably in low-power conditions, which can occur, for example, in rural areas near the end of a powerline transmission link.

Lau, U. S. Patent No. 5,550,476 discloses the use of photovoltaic cells to power a microprocessor and a radio transceiver which transmits the sensor output signals to a remote location. A capacitively coupled voltage sensor is used to determine the voltage level and a separate current coil is used to monitor the current level. Since power is supplied by the photovoltaic cells, such a device will not work in underground installations, or environments when sunlight is not received directly for long periods of time (e. g., shadows, at night, during storms, or cloudy or foggy conditions). In addition, the radio transceiver limits the range of the data transmission. Finally, there are no means for indicating the specific location of a fault in a powerline grid.

SUMMARY OF INVENTION It is therefore an object of this invention to provide a modular and integrated powerline monitor for non-high voltage applications.

It is a further object of this invention to provide such a modular and integrated powerline monitor which works reliably even inlow-power conditions.

It is a further object of this invention to provide such a modular and integrated powerline monitor which is easy to install and which is fully integrated to provide the required sensing and reporting functions.

It is a further object of this invention to provide such a modular and integrated powerline monitor which is capable of indicating not only the presence of a fault, but the location of the fault.

This invention results from the realization that the limitations of prior self- powered powerline sensors can be overcome in non-high voltage applications by directly extracting power from the powerline and that the expense and the limitations involved in using an external transmitter to transmit data from the monitor to remote locations can be overcome by directly coupling the data back onto the powerline and sending the data over the powerline to a remote location.

This invention features a modular, integrated powerline monitor for non- high voltage applications comprising sensing means for providing a sensor signal representative of conditions of or about a powerline; a processor, responsive to the sensor signal, for providing an output signal related to the sensor signal; means, connected directly to the powerline, for providing a reliable source of power for the processor; and means for transmitting output signal to a remote location over the powerline.

The sensing means typically includes a current sensor comprising an inductor having a plurality of current measurement windings wound about a separating material disposed about the powerline. The sensing means may also include a voltage sensor responsive to the means for providing power. The means for providing power typically includes an electrical tap connected directly to the powerline to be monitored which is also connected to the means for transmitting for simultaneously powering the processor and providing a channel for the means for transmitting to transmit the output signal over the powerline. The tap includes a housing for circumferentially engaging the powerline, a porting structure connected to the housing, and a needle receivable within the porting structure for piercing the powerline. Further included is a sealing layer proximate the needle for sealing the needle with respect to the powerline.

The processor includes programming which provides the output signal to the means for transmitting according to a set of rules.

The rules include a first routine which provides the output signal on a predetermined scheduling basis, a second routine which provides the output signal on a polling basis, and/or a third routine which provides the output signal whenever a predetermined threshold has been exceeded. The processor may also include programming for statistically analyzing the sensor signal. A voltage sensor and a current sensor is used in conjunction with the processor for calculating the phase angle between the current sensed and the voltage sensed to be used in determining the location of a powerline fault.

DISCLOSURE OF PREFERRED EMBODIMENT 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. 1 is a three dimensional diagrammatic view of the modular, integrated powerline monitor of the subject invention installed on a powerline; Fig. 2 is a schematic block diagram of the primary components of the modular, integrated powerline monitor shown in Fig. 1; Fig. 3 is a partially exploded view of the modular, integrated powerline monitor shown in Fig. 1; Figs. 4A-4C are schematic cross-sectional views with portions broken away showing the progressive installation of a tap used to extract power for the powerline monitor of this invention; Fig. 5 is a three dimensional diagrammatic view of the current sensor component of the powerline monitor shown in Fig. 1 and 2; Fig. 6 is a circuit diagram for the microprocessor, powerline carrier electronics, and signal conditioning circuitry of the powerline monitor of this invention; Fig. 7 is a circuit diagram of the power supply circuitry of the powerline monitor of this invention; Fig. 8 is a flow chart depicting the primary components of the programming resident on the microprocessor of the powerline monitor of the subjectinvention; Figs. 9A and 9B are schematic views depicting the operation of the fault location methodology in accordance with the subject invention; Fig. 10 is an aerial view showing the installation of a number of powerline monitors in accordance with the subject invention for isolating the location of a fault in a powerline grid; and Fig. 11 is a chart showing the readout data provided to the user located at a remote base station from the powerline monitor of this invention.

Powerline monitor 10, Fig. 1, includes modular housing 12 which fully integrates all of the primary components of monitor 10. Current sensor 14 includes clip 16 for securing it and housing 12 about a typical non-high voltage powerline 18.

Monitor 10 is powered directly by non-high voltage powerline 18 via taps 20 and 22 and thus works reliably even in low power conditions. Non-high voltage as used in this specification means voltage levels ranging generally up to about 1000 volts. Higher voltage systems could pose a safety concern due to the use of direct taps 20 and 22. Taps 20 and 22 also provide a means for directly transmitting data processed by monitor 12 over powerlines 18 or 19 to a remote location for further analysis thus overcoming the prior art limitations which use radio or other non-direct communication links.

The primary components of monitor 10 include power extraction module 30, Fig. 2 connected to taps 20 and 22 for providing power to processor 32 which receives input data from current sensor 14 and voltage sensor 34. Processor 32 then provides an output signal to transmission circuitry 36 which in turn transmits the output signal to a remote location via taps 20 and 22 over the powerline to which the monitor is attached. Other sensor devices 37, such as smoke detectors and temperature sensors may also be coupled to microprocessor 32.

Housing 12, Fig. 3, includes circuit board 40, Fig. 3, discussed in more detail with reference to Fig. 6 and another circuit board (not shown) underneath circuit board 40 including the power supply circuitry discussed in more detail with reference to Fig. 7. Because of its modular and integrated nature, monitor 10 is easy to install and maintain.

As shown for tap 20, Fig. 4A, housing 50 circumferentially engages powerline 18 and porting structure 52, connected to the housing, receives needle 54 therein. A sealing layer 51 such as a"Geltek"sealant strip of a tape like construction, resides in housing 50 to seal needle 54 with respect to powerline 18 and housing 50. Pressure is applied to needle 54 during installation as shown in Figs. 4B and 4C to drive the needle through the insulating layer of the powerline and to contact the conductive portion of the powerline as shown in Fig. 4C. Boot 55 provides the electrical connection via line 15, Fig. 1, to the circuitry in housing 12.

Current sensor 14, Fig. 5, includes inductor 60 having a number of current measurement windings 62 wound about toroidal shaped separating material (e. g. foam) 64. Current from powerline 18 induces a voltage in winding 62 proportional to the current flowing in powerline 18. Because inductor 60 is wound about separating material 64 which contains air or foam material, it does not become magnetically saturated as does a typical iron core. Therefore, the current is sensed in a more linear manner which makes the sensed information more accurate and easier to interpret. In iron core structures, in contrast, saturation can occur due to high fault currents in either the powerline being monitored and/or adjacent conductors.

Separating material 64 acts as a form for windings 62 and the material thereof has a low magnetic permeability like air. Separating material 64 can have a higher permeability but care must be taken to include gaps to control the magnetic permeability so that the material does not become magnetically saturated rendering the current sensed by inductor 60 less than linear and more difficult to interpret. A non-linear current measurement could be sensed by inductor 60 and interpreted accurately, however, this would require somewhat greater complexity in other elements of the monitor. Current sensor 14 includes gap 66 formed therein for installing it and removing it from AC powerline 18.

Circuit board 40, Fig. 3 is shown in more detail in Fig. 6. Taps 20 and 22, Fig. 1 are connected to power transformer 70 and coupling transformer 72 connected to sensor head bus 74 which is also connected to current sensor 14.

Optional auxiliary power 76 in the form of a battery pack or a photovoltaic cell based power supply may be coupled to these connections as shown and used during power outages. Power transformer 70 steps down the voltage received from the powerline and provides a voltage input to a power supply coupled to power supply bus 78. Coupling transformer 72 receives data from microprocessor 32 to be transmitted over the powerline as discussed above and also transmits signals sent on the powerline from a remote location to processor 32.

Current sensor 14 is connected via bus 74 to amplifier and signal conditioning circuit 82 which provides a signal to microprocessor 32 representative of the current sensed by current sensor 14 over line 84. The voltage level on the powerline is determined via amplifier and signal conditioning circuity 34 which is coupled directly to power transformer 70 via bus 74 as shown over lines 88 and thus provides a signal over line 90 representative of the voltage level on the powerline. The output of microprocessor 32 is coupled to powerline carrier electronics circuitry 36.

Powerline carrier electronics 36 can be any technology that superimposes a high frequency data signal on the powerline. This includes spread spectrum, frequency hopping, discrete frequency, frequency shift keying (FSK), phase shift keying (PSK), or quadrature modulation. These techniques may employ bi- directional data transfer. This feature allows the sensor to be polled by the collector so specific data can be immediately accessed instead of waiting for the sensor to send data periodically.

Reset circuitry 35 is used to reset the microprocessor when there is a power failure and the power is reapplied. A"power on"reset circuit may be used.

Power supply 100 which makes up a portion of power extraction module 30, Fig. 6, includes rectifier 102, Fig. 7, step down circuitry 104, switching network 110, and capacitor block 108 responsive to supply 110 as the primary components. Power supply 100 uses two large capacitors 112 and 114 to store significant energy to allow a number of transmissions after power is lost. Diodes 116 and 118 stop current from flowing back into the power supply 104. The loss of line voltage is sensed by the microprocessor voltage sensing circuitry 82, Fig. 6.

At this time, a distress signal may be sent out to the collector.

Microprocessor 32, Fig. 6, is programmed with an initialization routine, step 150, Fig. 8. All the ports are checked, the powerline carrier electronics is initialized, and the microprocessor reads the individual addresses of the powerline carrier electronics. Next, step 152, the voltage is read from signal conditioning circuitry 82, Fig. 6, the current is read from signal conditioning circuit 34 for one cycle, approximately 16 milliseconds (at 60Hz), thereby obtaining approximately 64 data points. The root mean square value for each of these values is then calculated, step 154 and the peak values and the relative times at which the respective current and voltage peak values occur are calculated and used to determine the phase angle between the voltage and current, step 156. This data will later be used to assist in isolating the location of a fault among various links of a powerline grid. Various statistical processing techniques are used, step 158, to keep track of various trends such as high and low current levels and voltage variations over a particular period of time.

Reporting is then accomplished in accordance with reporting rules established in the microprocessor or triggered from a remote base station as desired based on the user's preference, step 160. The options include scheduled reporting as shown at 162 wherein for example, data is transmitted from the microprocessor on a scheduled basis ; poll reporting as shown at 164 wherein data is transmitted by the microprocessor only when the microprocessor is polled from a remote location; and/or threshold/condition reporting, as shown at 166 wherein the microprocessor transmits data only upon the occurrence of a particular sensed parameter exceeding or failing to meet a preset threshold/condition. The microprocessor will follow the reporting rules established or triggered and then send the output data to the powerline electronics module, step 168 which then tags the data for transmission, step 170 in order to provide the user with the address and/or location of the particular sensor transmitting the output data. Finally, the data is transmitted, step 172.

In order to assist in isolating the location of a particular fault, a plurality of monitors 180,182,184,186,188, and 189 Fig. 9A are installed and distributed about links 190,192,194,196,198 and 199 of powerline distribution grid 200.

Each monitor is programmed in accordance with the flow chart shown in Fig. 8 to calculate the phase angle between the current and the voltage waveforms thereby providing an indication of the direction of the power flow in each link. As shown at 210 for waveforms 212 and 214, when voltage is leading the current waveform, power is flowing in the positive direction shown by arrow 216. As shown at 218, Fig. 9B, however, if the power flow direction changes as shown by arrow 220 for monitor 182, current waveform 212 as shown at 218 will lead voltage waveform 214. So, for example, if there is a fault on link 194, the technician who is reviewing the data from all of the monitors distributed about grid 200 may observe a change in the power flow direction on link 192, a no or low-current condition on link 194, and a change in the power flow direction on link 199 via monitor 189.

Using this data, the technician will be able to accurately predict that the fault is located on link 194.

Other indicators used to isolate the location of a fault on the various links of grid 200 include the historical current levels sensed by each monitor, the present current level sensed by each monitor, the historical direction of power flow, the present direction of power flow, the overall voltage level, and the overall current level as well as the data received from other types of sensors such as smoke detectors, temperature sensors, and the like. The ability to isolate a fault to a specific link of a distribution grid can mean the difference between searching a ten or fifteen block square area including ten or more transformer vaults and being able to isolate the fault to a single transformer vault. In the example shown in Fig.

10, a monitor in accordance with the subject invention is placed at each location shown by an arrow to accomplish this unique function.

Thus, each monitor transmits a signal which, for example, may show a record of the voltage level as shown for graph 230, Fig. 11, a record of the current level in amps as shown for graph 240, the present power flow direction as shown at 242, and some indication of a change in power flow direction as shown at 244.

Although specific features of this invention are shown in some drawings and not 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 followingclaims: What is claimed is: