Patent Publication Number: US-11031812-B1

Title: Electric field powered devices in electric power systems

Description:
TECHNICAL FIELD 
     The present disclosure pertains to powering line sensors using electric fields in proximity to electric power lines. More particularly, but not exclusively, the present disclosure pertains to devices that generate power from electric fields emanating from the electric power lines on which or in proximity to which such devices are installed. Such devices may be used, in connection with other equipment, to monitor, automate, and/or protect the electric power system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments of the disclosure are described, including various embodiments of the disclosure with reference to the figures, in which: 
         FIG. 1  illustrates a conceptual representation of an electric field power conversion system to convert electric fields emanating from a reference conductor in an electric power to a usable output voltage consistent with embodiments of the present disclosure. 
         FIG. 2  illustrates a simplified one-line diagram of an electric power delivery system including an electric power conversion system consistent with embodiments of the present disclosure. 
         FIG. 3A  illustrates a representation of a system including an electric field power conversion system device consistent with embodiments of the present disclosure. 
         FIG. 3B  illustrates a circuit equivalent for the system illustrated in  FIG. 3A  consistent with embodiments of the present disclosure. 
         FIG. 3C  illustrates a Thevenin equivalent for the circuit illustrated in  FIG. 3B  consistent with embodiments of the present disclosure. 
         FIG. 3D  illustrates the Thevenin equivalent circuit of  FIG. 3C  with a matched resistance, R L , consistent with embodiments of the present disclosure. 
         FIG. 4  illustrates a circuit comprising a Thevenin equivalent of an electric field power conversion system, a full bridge rectifier, a bulk capacitor, and a load consistent with embodiments of the present disclosure. 
         FIG. 5A  illustrates a circuit comprising a Thevenin equivalent of an electric field power conversion system, a full bridge rectifier, a bulk capacitor, a switch mode power supply, and a load consistent with embodiments of the present disclosure. 
         FIG. 5B  illustrates one embodiment of a spark gap device consistent with embodiments of the present disclosure. 
         FIG. 5C  illustrates a plot over time of a voltage across a bulk capacitor in  FIG. 5A  consistent with embodiments of the present disclosure. 
         FIG. 5D  illustrates a plot of voltage across the bulk capacitor and a current through an inductor while an electric arc exists across the spark gap and consistent with embodiments of the present disclosure. 
         FIG. 5E  illustrates a plot of the voltage across the bulk capacitor, the output voltage at a node, and current through the inductor over time consistent with embodiments of the present disclosure. 
         FIG. 6  illustrates a circuit diagram of a flyback converter that may provide power for use by a distributed sensor consistent with embodiments of the present disclosure. 
         FIG. 7  illustrates a functional block diagram of a system to monitor electrical parameters in an electric power system using a distributed sensor powered by an electric field power conversion subsystem consistent with embodiments of the present disclosure. 
         FIG. 8  illustrates a flowchart of a method of collecting and using information from a system to monitor a condition affecting an electric power system. 
     
    
    
     DETAILED DESCRIPTION 
     Electric power systems are used to generate, transmit, and distribute electric power to loads, and serve as an important part of critical infrastructure. Electric power systems and equipment may be monitored and protected by a variety of types of equipment. Protection relays may analyze the parameters of an electric power system to implement protective functions. The primary protective relays may communicate with various other supervisory devices such as automation systems, monitoring systems, supervisory (SCADA) systems, and other intelligent electronic devices (IEDs). IEDs may collect data from various devices within an electric power system and monitor, control, automate, and/or protect such devices. 
     Sensors distributed throughout an electric power system may be used to perform various tasks. For example, faulted circuit indicators (FCI) may include electrostatic power systems capable of gathering small amounts of power (e.g., about 10 microwatts) that is stored in capacitors to trip or reset a visual indicator on current conditions of an electric power line on which the FCI is mounted. The amount of power generated by an FCIs is too small to power electronics that acquire voltage or current samples and to power communications systems to transmit this data. Other power sources include solar or wind generators; however, these sources are intermittent and may require batteries to operate reliability. Further, inclusion of batteries in distributed sensors may increase the maintenance associated with such devices because batteries degrade over time. 
     Existing distributed sensor systems may also rely on physical connections, which may be resistive or capacitive, between one electric power conductor and an adjacent phase or ground. Such systems are more complex to install and maintain in comparison to devices that are not resistively or capacitively connected between phases or between one phase and ground. 
     The inventors of the present disclosure have recognized improved techniques disclosed herein for powering devices using electric fields emanating from conductors in electric power systems. Systems and methods disclosed herein may provide sufficient power to operate electronics for generating and communicating measurements of electrical parameters. Further, such systems may operate on conductors with minimal or no current flow, without the need for sun or wind, and without batteries. Such systems may also physically couple exclusively to one electrical conductor, without the need for physical connections between phases or between one phase and ground, thus simplifying installation of such systems. 
     Systems and methods consistent with the present disclosure may generate power from electric fields emanating from electric conductors for sensors that monitor electrical parameters, such as current and voltage, or other conditions (e.g., environmental conditions, integrity of electric power system devices, etc.). Various types of systems may be used to convert energy from the electric fields to useable energy, including a thermoelectric device, an electrostatic motor, and/or a switch mode power supply. 
     Sensors consistent with the present disclosure may be used to generate electrical parameter measurements that may be used in a wide range of applications such as fault current magnitude, fault direction, and high impedance fault detection, etc. Such data may be provided to a variety of equipment used to automate, monitor, and protect the power system, such as protective relays, IEDs, control systems, etc. 
     As used herein, an IED may refer to any microprocessor-based device that monitors, controls, automates, and/or protects monitored equipment within a system. Such devices may include, for example, differential relays, distance relays, directional relays, feeder relays, overcurrent relays, voltage regulator controls, voltage relays, breaker failure relays, generator relays, motor relays, remote terminal units, automation controllers, bay controllers, meters, recloser controls, communication processors, computing platforms, programmable logic controllers (PLCs), programmable automation controllers, input and output modules, and the like. The term IED may be used to describe an individual IED or a system comprising multiple IEDs. Further, IEDs may include sensors (e.g., voltage transformers, current transformers, contact sensors, status sensors, light sensors, tension sensors, etc.) that obtain information about the electric power system. 
     The embodiments of the disclosure will be best understood by reference to the drawings. It will be readily understood that the components of the disclosed embodiments, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the systems and methods of the disclosure is not intended to limit the scope of the disclosure, as claimed, but is merely representative of possible embodiments of the disclosure. In addition, the steps of a method do not necessarily need to be executed in any specific order, or even sequentially, nor do the steps need to be executed only once, unless otherwise specified. 
     In some cases, well-known features, structures, or operations are not shown or described in detail. Furthermore, the described features, structures, or operations may be combined in any suitable manner in one or more embodiments. It will also be readily understood that the components of the embodiments, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. For example, throughout this specification, any reference to “one embodiment,” “an embodiment,” or “the embodiment” means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, the quoted phrases, or variations thereof, as recited throughout this specification are not necessarily all referring to the same embodiment. 
     Several aspects of the embodiments disclosed herein may be implemented as software modules or components. As used herein, a software module or component may include any type of computer instruction or computer-executable code located within a memory device that is operable in conjunction with appropriate hardware to implement the programmed instructions. A software module or component may, for instance, comprise one or more physical or logical blocks of computer instructions, which may be organized as a routine, program, object, component, data structure, etc., that performs one or more tasks or implements particular abstract data types. 
     In certain embodiments, a particular software module or component may comprise disparate instructions stored in different locations of a memory device, which together implement the described functionality of the module. A module or component may comprise a single instruction or many instructions and may be distributed over several different code segments, among different programs, and across several memory devices. Some embodiments may be practiced in a distributed computing environment where tasks are performed by a remote processing device linked through a communications network. In a distributed computing environment, software modules or components may be located in local and/or remote memory storage devices. In addition, data being tied or rendered together in a database record may be resident in the same memory device, or across several memory devices, and may be linked together in fields of a record in a database across a network. 
     Embodiments may be provided as a computer program product including a non-transitory machine-readable medium having stored thereon instructions that may be used to program a computer or other electronic device to perform processes described herein. The non-transitory machine-readable medium may include, but is not limited to, hard drives, floppy diskettes, optical disks, CD-ROMs, DVD-ROMs, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, solid-state memory devices, or other types of media/machine-readable media suitable for storing electronic instructions. In some embodiments, the computer or another electronic device may include a processing device such as a microprocessor, microcontroller, logic circuitry, or the like. The processing device may further include one or more special-purpose processing devices such as an application-specific interface circuit (ASIC), PAL, PLA, PLD, field-programmable gate array (FPGA), or any other customizable or programmable device. 
       FIG. 1  illustrates a conceptual representation of an electric field power conversion system  100  to convert electric fields emanating from a reference conductor in an electric power to a usable output voltage consistent with embodiments of the present disclosure. An electric field power conversion system  112  is mounted to the reference conductor  106 . A peripheral conductor  102  (or multiple conductors depending on the system) may be an adjacent phase conductor (e.g., conductors in a three-phase system) and/or any ground conductors, grounded structures, or the earth ground. 
     An electric field node conductor  104  may be a part of a system that converts energy from an electric field emanating from a conductor in an electric power system to a usable power source. The electric field node conductor  104  may be disposed in proximity to reference conductor  106 . The electric field node conductor  104  may have any shape, size, composition, location, and design. For example, spherical or toroidal surfaces may increase capacitance and/or decrease corona discharge. Electric field node conductor  104  may maximize a parasitic capacitance  108  between the electric field node conductor  104  and the peripheral conductor  102 , while minimizing a parasitic capacitance  110  between the electric field node conductor  104  and the reference conductor  106 . The parasitic capacitances  108  and  110  are illustrated in dashed lines because the capacitances are not physical connections. In various embodiments, the reference conductor  106  could also be a ground conductor, grounded structure, or earth ground and the peripherical conductor  102  may comprise one or more electric power phase conductors. 
     Electric field power conversion system  112  is electrically attached to the electric field node conductor  104  and reference conductor  106 . Electric field power conversion system  112  converts the electric field power emanating from reference conductor  106  to a usable electric potential, V out . In various embodiments, the voltage output may be less than 100 Volts and may be referenced to the electronic circuitry ground. 
     The usable electric potential generated by electric field power conversion system  112  may be used to power a variety of devices, such as voltage sensors, current sensors, fallen conductor sensors, environmental sensors, and the like. Further, the power generated by electric field power conversion system  112  may power a communication system to transmit measurements generated by such sensors. Electric field power conversion system  112  may generate sufficient power for both a sensor and a communication system. In various embodiments, the power generated by electric field power conversion system  112  is on the order of tens of milliwatts. Other embodiments may generate more power. 
     The usable voltage output (i.e., V out  with respect to electronic circuitry ground) may be unregulated. The output may be a direct current with a ripple or an alternating current (at any frequency, fixed or variable, with any harmonic content). Additional circuitry (e.g., a voltage regulator) may be included to condition the output for specific applications. 
     In some embodiments, the “ground” value of the usable electric potential generated by the electric field power conversion system  112  may equal (or approximately equal) the potential of the reference conductor  106 . In such embodiments, the electric field power conversion system  112  may comprise an isolated supply to allow the reference conductor  106  to serve as the “ground” value of the output. 
     Electric field power conversion system  112  may comprise a variety of energy conversion devices to generate a useful electrical output from the electric fields emanating from reference conductor  106 . In some embodiments, a resistive device may be in  112  and placed across nodes  104  and  106 , and a thermoelectric device may convert the heat to a useable voltage at V out . The thermoelectric device may provide a stable output that can be used to power a variety of devices for various applications. Thermoelectric devices may be solid-state devices that operate reliably for long periods of time and in severe environments without maintenance. 
     In other embodiments, an electrostatic motor (e.g., a corona motor) may be in  112  and placed across nodes  104  and  106  that produces mechanical energy. The mechanical energy from the electrostatic motor may be converted to electric energy with an electric generator. The output of the generator V out  may be either alternating current or direct current depending on the application. Electrostatic motors may tolerate high input voltages and may allow for use of systems consistent with the present disclosure on high-voltage applications, such as high-voltage electric transmission lines. 
     In still other embodiments a switch mode power supply may be in  112  and the input of the power supply placed across nodes  104  and  106  and the output of the power supply generating V out . The switch mode power supply may be embodied in a variety of ways, including without limitation: a semiconductor (e.g., an insulated-gate bipolar transistor (IGBT) or a metal oxide silicon field effect transistor (MOSFET)), a spark gap, a non-isolated buck converter, an isolated flyback converter, and an isolated forward converter. Several of these switch mode power supplies are discussed in greater detail below. 
     In various embodiments, a mounting system may be used to mount electric field power conversion system  100  to reference conductor  106 . The mounting system may include physical connections to secure electric field power conversion system  112 . Further, the mounting system may allow electric field node conductor  104  to be mount to reference conductor  106 . 
       FIG. 2  illustrates a simplified one-line diagram of an electric power delivery system  200  including an electric power conversion system consistent with embodiments of the present disclosure. Electric power delivery system  200  may be configured to generate, transmit, and distribute electric energy to loads. Electric power delivery systems may include equipment such as electrical generators (e.g., generators  210 ,  212 ,  214 , and  216 ), transformers (e.g., transformers  217 ,  220 ,  222 ,  230 ,  242 ,  244 ,  250 , and  274 ), power transmission and delivery lines (e.g., lines  224 ,  234 ,  236 , and  258 ), circuit breakers (e.g., breaker  260 ), busses (e.g., busses  218 ,  226 ,  232 , and  248 ), loads (e.g., loads  240  and  238 ) and the like. A variety of other types of equipment may also be included in electric power delivery system  200 , such as voltage regulators, capacitor banks, and the like. 
     Substation  219  may include a generator  214 , which may be a distributed generator, and which may be connected to bus  226  through step-up transformer  217 . Bus  226  may be connected to a distribution bus  232  via a step-down transformer  230 . Various distribution lines  236  and  234  may be connected to distribution bus  232 . Load  240  may be fed from distribution line  236 . Further, step-down transformer  244  in communication with distribution bus  232  via distribution line  236  may be used to step down a voltage for consumption by load  240 . 
     Distribution line  234  may lead to substation  251  and deliver electric power to bus  248 . Bus  248  may also receive electric power from distributed generator  216  via transformer  250 . Distribution line  258  may deliver electric power from bus  248  to load  238  and may include further step-down transformer  242 . Circuit breaker  260  may be used to selectively connect bus  248  to distribution line  234 . IED  208  may be used to monitor and/or control circuit breaker  260  as well as distribution line  258 . 
     Electric power delivery system  200  may be monitored, controlled, automated, and/or protected using IEDs, such as IEDs  204 ,  206 ,  208 ,  215 , and  270 , and a central monitoring system  272 . In general, IEDs in an electric power generation and transmission system may be used for protection, control, automation, and/or monitoring of equipment in the system. For example, IEDs may be used to monitor equipment of many types, including electric transmission lines, electric distribution lines, current transformers, busses, switches, circuit breakers, reclosers, transformers, autotransformers, tap changers, voltage regulators, capacitor banks, generators, motors, pumps, compressors, valves, and a variety of other types of monitored equipment. 
     Central monitoring system  272  may comprise one or more of a variety of types of systems. For example, central monitoring system  272  may include a supervisory control and data acquisition (SCADA) system and/or a wide area control and situational awareness (WACSA) system. A central IED  270  may be in communication with IEDs  204 ,  206 ,  208 , and  215 . IEDs  204 ,  206 ,  208 , and  215  may be remote from the central IED  270  and may communicate over various media such as a direct communication from IED  206  or over a wide-area communications network  262 . According to various embodiments, certain IEDs may be in direct communication with other IEDs (e.g., IED  204  is in direct communication with central IED  270 ) or may be in communication via a communication network  262  (e.g., IED  208  is in communication with central IED  270  via communication network  262 ). 
     A common time signal  268  may be used to time-align measurements for comparison and/or synchronize action across system  200 . Utilizing a common or universal time source may allow for the generation of time-synchronized data, such as synchrophasors. In various embodiments, the common time source may comprise a time signal from a GNSS system  290 . IED  204  may include a receiver  292  configured to receive the time signal  268  from the GNSS system  290 . In various embodiments, IED  206  may be configured to distribute the time signal  268  to other components in system  200 , such as IEDs  204 ,  208 ,  215 , and  270 . 
     A voltage transformer  274  may be in communication with a merging unit (MU)  276 . MU  276  may provide information from voltage transformer  274  to IED  215  in a format useable by IED  215 . MU  276  may be placed near to voltage transformer  274  and may digitize discrete input/output (I/O) signals and analog data, such as voltage measurements. These data may then be streamed to IED  215 . In various embodiments, MU  276  may be located outside of a substation enclosure or control house, thus increasing safety by removing high-energy cables from areas where personnel typically work. In various embodiments, MU  276  may be embodied as an SEL-2240 available from Schweitzer Engineering Laboratories of Pullman, Wash. 
     A variety of sensors, such as sensor  280 , may be distributed throughout system  200  to obtain information regarding electrical conditions used for automation, monitoring, and protection. Sensor  280  may track the frequency of alternating current through transmission line  258  to determine a data sampling period and obtain a specified number of samples per cycle. The sampled data may be provided to IED  208  or another device for use in a variety of applications, such as determining a fault current magnitude, determining a fault direction, and detecting a high impedance fault, etc. 
       FIG. 3A  illustrates a conceptual representation of a system  300  including an electric field power conversion system  302  device consistent with embodiments of the present disclosure. System  300  comprises a three-phase power system that includes three power sources (VA, VB, and VC), each of which is out of phase by 120°. The three power sources are connected to respective conductors (A, B and C). The electric field power conversion system  302  is mounted to conductor A. As one of skill in the art will appreciate, the conceptual representation illustrated in  FIG. 3A  is intended to reflect an abstraction of various concepts disclosed herein rather than details of a specific implementation. 
     In the illustrated embodiment, electric field power conversion system  302  includes a cylinder  304  with length l and radius r surrounding a portion of conductor A. In other embodiments, other designs may be used. Parasitic capacitances between the cylinder  304  and each phase are shown using dashed lines. The parasitic capacitance between the cylinder  304  and Earth or ground  312  is also shown. The value of the capacitance  306  between the cylinder  304  and phase A is influenced by the radius (r) and length (I) of the cylinder  304 . The value of the capacitance  308  between the cylinder  304  and phase B is influenced by the distance between conductor A and conductor B (dab) and the surface parameters of  304 . The value of the capacitance  310  between the cylinder  304  and phase C is influenced by the distance between conductor A and conductor C (dac) and the surface parameters of  304 . Finally, the value of the capacitance  312  between the cylinder  304  and ground is influenced by the height (h) of conductor A above the ground and the surface parameters of  304 . 
       FIG. 3B  illustrates a circuit equivalent for the system illustrated in  FIG. 3A  consistent with embodiments of the present disclosure. The electric field from conductor A creates a voltage, V cyl , across capacitor  306 . As such, electric field power conversion system  302  of  FIG. 3A  may be designed to minimize the value of capacitor  306  while maximizing the other capacitances. A usable electric potential may be developed between node  304  (i.e., cylinder  304  in  FIG. 3A ) and the reference conductor (i.e., conductor A in  FIG. 3A ). Various designs, materials, and configurations of the device may be used in various embodiments. 
       FIG. 3C  illustrates a Thevenin equivalent for the circuit illustrated in  FIG. 3B  consistent with embodiments of the present disclosure. Power transfer from conductor A to the electric field power conversion system  302  of  FIG. 3A  is maximized when the input impedance of electric field power conversion system  302  approximately matches the Thevenin impedance of the conductors. The Thevenin equivalent capacitance C th ,  314  is based on the values of capacitors  306 ,  308 ,  310 , and  312 . The Thevenin equivalent source is the voltage across the capacitor V cyl . 
       FIG. 3D  illustrates the Thevenin equivalent circuit of  FIG. 3C  with a matched resistance, RL, consistent with embodiments of the present disclosure. The optimum power transfer occurs when the load, RL, matches the capacitive reactance of the of the Thevenin capacitance, C Th ,  314  of  FIG. 3C . The available power to the load, RL, is proportional to the square of the line-to-line voltage. The optimal value of the load, RL, can be calculated using Eq. 1. 
     
       
         
           
             
               
                 
                   
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     The impedance for systems consistent with the present disclosure may be in the range of 10s of megaohms to  100   s  of megaohms. Matching this high impedance is one of the challenges for implementing an electric field power conversion system. Although optimum power transfer occurs when the load matches the input impedance, some mismatch may still allow for satisfactory performance. Accordingly, various systems consistent with the present disclosure may seek to approximately match the impedance within two orders of magnitude. 
     In various embodiments, the load, RL, may comprise a variety of devices. In some embodiments, the load, RL, comprises sensors and electronics used to monitor conditions associated with an electric power system (e.g., electrical parameters, environmental conditions, equipment status, etc.). In other embodiments, the load, RL, comprises circuitry that ultimately drives sensors and electronics. Such circuitry may include, for example, a resistive element that generates heat used by a thermo electric device to generate electrical energy. Further, the circuitry may include a generator that converts the output voltage to mechanical energy and a generator to convert the mechanical energy to electrical energy. 
       FIG. 4  illustrates a circuit  400  comprising a Thevenin equivalent  402  of an electric power system and electric field power conversion system  410  consistent with embodiments the present disclosure. Electric power conversion system  410  includes a full bridge rectifier  404  and a bulk capacitor  406 . Operation of diodes in the full bridge rectifier  404  converts alternating current provided by a source to a direct current. In some embodiments, a half-bridge rectifier may be used; however, is such embodiments, the available power available to provide to load  408  would be reduced. Capacitor  406  may smooth the voltage output from full bridge rectifier  404 . The smoothed output of the electric power conversion system  410  may be a useable electric power source that provides power to a load  408 . In various embodiments, load  408  may represent a variety of devices (e.g., electric parameter sensors, environmental sensors, communication devices, etc.) powered by an electric field power conversion system consistent with the present disclosure. 
       FIG. 5A  illustrates a circuit  500  comprising a Thevenin equivalent  502  of an electric power system and an electric field power conversion system consistent with embodiments of the present disclosure. In the illustrated embodiment, electric power conversion system  510  includes a full bridge rectifier  504 , a bulk capacitor  506 , and a switch mode power supply  518 . Switch mode power supply  518  comprises a spark gap  528 . Charge builds across bulk capacitor  506  until the voltage exceeds a breakdown threshold across the spark gap  528 . The spark transfers electrical energy to inductor  516 . 
       FIG. 5B  illustrates one embodiment of a spark gap device  550  consistent with embodiments of the present disclosure. The device may comprise a housing  570  that contains a plurality of components. A pair of conductors  552  and  554  may enter the housing  570  and may be connected to circuit  500  at nodes  522  and  524  (shown in  FIG. 5A ), respectively. Contact between the conductors  552  and  554  and a pair of conductive spheres  556  and  558  may be maintained by springs  560  and  562 , respectively. An insulator  568  may be disposed between the conductive spheres  556  and  558 . A spark gap  566  may allow an electrical arc to transmit electrical energy between the conductive spheres  556  and  558  when the voltage difference exceeds a breakdown voltage. 
       FIG. 5C  illustrates a plot over time of a voltage across a bulk capacitor  506  in  FIG. 5A  consistent with embodiments of the present disclosure. As shown, the voltage increases over time until it reaches the breakdown voltage of spark gap  528 . The increasing voltage stores energy in the bulk capacitor that is discharged by an arc across spark gap  528 . 
       FIG. 5D  illustrates a plot of the voltage across bulk capacitor  506  (shown in  FIG. 5A ) and the current through inductor  516  while an electric arc exists across spark gap  528 , consistent with embodiments of the present disclosure. As may be appreciated, when the voltage across bulk capacitor  506  is below the breakdown voltage, there is no energy transfer across the spark gap  528 . Any voltage at node  512  is maintained by the output capacitance  520 . As energy is collected from the input power supply (i.e., a line-mounted electric field energy conversion device), the voltage increases toward the breakdown voltage. 
     Once the voltage across bulk capacitor  506  reaches the breakdown voltage of the spark gap  528 , an electric arc forms across the spark gap  528 . The charge in the bulk capacitor  506  redistributes with the parasitic capacitance of the diode  526  and parasitic capacitance of the inductor  516 . While the arc continues, the remaining energy in these capacitances transfers to the inductor and the output load  508 . Over time, the current in the inductor begins to flow through diode  526  and the arc in the spark gap  528  extinguishes. The inductor current continues to decrease until all the energy that was stored in the inductor is transferred to the output load (RL and CL). 
       FIG. 5E  illustrates a plot of the voltage across bulk capacitor  506 , the output voltage at node  512 , and current through inductor  516  over time consistent with embodiments of the present disclosure. The current in the inductor  516  ramps down to zero as the energy in the inductor transfers to the output load. The output voltage remains relatively constant at approximately 30 V dc . Once the energy in inductor  516  ramps down to zero, the voltage at node  524  exhibits the typical ringing that occurs at the beginning of the discontinuous mode for a buck converter. 
     The values of circuit components may be selected based on particular applications. For example, if the value of bulk capacitor  506  is too low, an appreciable loss of energy may occur; however, if the value is too high, the energy efficiency is reduced as energy transfers from the Thevenin capacitance to the bulk capacitance. Further, the ratio of the forward voltage drop of diode  526  and the output voltage impacts the efficiency of the buck converter if the diode voltage drop is a significant fraction of the output voltage. 
     Embodiments may also be optimized for use at different voltages that typically exist at different segments in an electric power system. For example, embodiments used in high-voltage applications (e.g., high-voltage transmission lines) may utilize different components in comparison to embodiments used in lower-voltage applications. Corona motors may be well-suited to high-voltage applications, where other energy conversion devices, such as a spark gap converter, may not be well suited for high voltages, both due to component limitations. 
       FIG. 6  illustrates a circuit diagram of a flyback converter  600  that may provide power for use by a distributed sensor consistent with embodiments of the present disclosure. A Thevenin equivalent  602  of an electric field power conversion system may provide power to a full bridge rectifier  604  and to flyback converter  600 . In operation, a switch  612  may close to connect the primary of a transformer  614  to the input voltage source. The primary current and magnetic flux in the transformer  614  increases and stores energy. The voltage induced in a secondary winding is negative, which reverse biases the diode  610 . The reverse bias prevents current flow, which leaves an output capacitor  606  to provide power to a load  608 . 
     When switch  612  is opened, the primary current and magnetic flux in transformer  614  drops, resulting in a positive secondary voltage. The positive secondary voltage allows current to flow from the transformer  614  through diode  610 . The energy from the transformer  614  recharges output capacitor  606  and provides power to load  608 . 
     In various embodiments, switch  612  may be implemented using a spark gap or a semiconductor switching device. In some embodiments, the semiconductor switching device may comprise an IGBT or a MOSFET. In other embodiments, switch  612  may be embodied as a spark gap. As one of skill in the art will appreciate, semiconductor switching devices may also be used in other types of devices that provide power for use by a line-mounted sensor consistent with embodiments of the present disclosure. 
       FIG. 7  illustrates a functional block diagram of a system  700  to monitor electrical parameters in an electric power system using a line-mounted sensor powered by an electric field power conversion subsystem  722  consistent with embodiments of the present disclosure. System  700  may be implemented using hardware, software, firmware, and/or any combination thereof. The specifically illustrated configuration is merely representative of one embodiment consistent with the present disclosure. 
     Line-mounted sensor  720  is mounted to conductor  754 , which is suspended between pylons  750 ,  752 . Only a single line-mounted wireless sensor  720  is illustrated. In other embodiments, multiple line-mounted sensors may be used. Additional line-mounted sensors may be disposed at other locations or mounted to other conductors. Conductor  754  may comprise a high-voltage transmission line or a medium-voltage distribution line. 
     Line-mounted sensor  720  and IED  730  each contain various subsystems represented by functional blocks. The functional blocks in line-mounted sensor  720  may communicate using data bus  724 , and the functional blocks in IED  730  may communicate using data bus  748 . Although the illustrated embodiment comprises a line-mounted sensor  720 , in other embodiments a line mounted device may include a environmental sensors, communication devices (e.g., repeaters), and the like. 
     A wireless communication subsystem  712  may be configured to communicate information, such as measurements obtained by line-mounted sensor  720 , to IED  730 . Communication subsystem  712  may utilize various technologies to enable wireless communication. Such communication may include radio frequency communications and may employ analog or digital modulation techniques and protocols. 
     Communication subsystem  712  may enable transmission of data from line-mounted sensor  720  related to electrical parameters associated with conductor  754 . In some embodiments, communication subsystem  712  may enable bi-directional communication between line-mounted sensor  720  and IED  730 , while in other embodiments, communication may be unidirectional. 
     An electric parameter sensor  714  may measure electric parameters associated with electric energy in conductor  754 . Electric parameter sensor  714  may comprise a voltage sensor, a current sensor, or any other type of device to monitor an aspect of electrical energy in conductor  754 . 
     An electric field power conversion subsystem  722  may convert power emanating from conductor  754  to a usable electric output. Electric field power conversion subsystem  722  may further incorporate a power storage device that may be used to transmit information when current is not flowing through conductor  754  and power cannot be generated from electric fields. A power storage device may be embodied as a battery, a supercapacitor, and the like. 
     A memory  716  may include computer system readable media in the form of volatile memory, such as random-access memory (RAM) and/or cache memory. The memory  716  may further include other removable/non-removable, volatile/non-volatile computer system storage media. In various embodiments, the memory  716  may include at least one program product having a set of program modules that are configured to carry out the functions described herein. 
     A processing subsystem  710  may be configured to process information received from other functional blocks in line-mounted sensor  720 . Processing subsystem  710  may operate using any number of processing rates and architectures. Processing subsystem  710  may be configured to perform various algorithms and calculations described herein. Processing subsystem  710  may be embodied as a general-purpose integrated circuit, an application-specific integrated circuit, a field-programmable gate array, and/or any other suitable programmable logic device. 
     Turning now to the functional blocks associated with IED  730 , a monitored equipment subsystem  732  may be in communication with monitored equipment that is operable to control an aspect or a portion of an electric power system. The monitored equipment subsystem  732  may be configured to issue commands to and/or receive status information from monitored equipment. In certain embodiments, monitored equipment subsystem  732  may be in communication with, for example, a circuit breaker and may issue commands to the circuit breaker to selectively connect or disconnect portions of the electric power system. 
     Memory  746  may include computer system readable media in the form of volatile memory, such as random-access memory (RAM) and/or cache memory. The memory  746  may further include other removable/non-removable, volatile/non-volatile computer system storage media. In various embodiments, the memory  746  may include at least one program product having a set of program modules. 
     Processing subsystem  736  may be configured to perform various algorithms and calculations described herein. In various embodiments, processing subsystem  736  may be embodied as a general-purpose integrated circuit, an application-specific integrated circuit, a field-programmable gate array, and/or any other suitable programmable logic device. 
     Communication subsystem  738  may receive information from and/or send information to line-mounted sensor  720 . Communication subsystem  738  may be compatible with communication subsystem  712 , utilizing the same communication technology and communication protocol(s). In various embodiments, IED  730  may also comprise other communication interfaces (e.g., a wired communication interface) to communicate with other devices, such as other IEDs, a SCADA system, etc. 
     A control action subsystem  742  may implement control actions based on information received from line-mounted sensor  720  and other electrical parameters associated with electric energy in conductor  754 . In some embodiments, control action subsystem  742  may control a circuit breaker, which may be selectively activated and deactivated based on electrical conditions. Control action subsystem  742  may issue commands to selectively connect and disconnect portions of an electric power system using monitored equipment subsystem  732 . 
       FIG. 8  illustrates a flowchart of a method  800  of collecting and using information from a system to monitor a condition affecting an electric power system. At  802 , a sensor may be mounted to a reference conductor in an electric power system. The sensor may be configured to monitor electrical parameters (e.g., voltage, current, etc.), environmental conditions (temperature, humidity, wind, etc.), and/or conditions of the electric power system (e.g., equipment status, etc.). 
     At  804 , a useable electric potential may be generated from an electric field created by the electric power system and existing between the reference conductor and a peripheral conductor. In some embodiments, the reference conductor may be one phase of a multi-phase power system, and the peripheral conductor may be another phase. Alternatively, the peripheral conductor may comprise a ground or neutral conductor. 
     At  806 , a sensor powered by the usable electric potential between the reference conductor and the peripheral conductor may determine a measurement of a condition. In some embodiments, the measurement of the condition may be used to monitor, automate, and/or protect the electric power system. For example, the sensor may be embodied as a current sensor, and upon detection of an over-current condition, an IED or protective relay may actuate a breaker to interrupt the flow of current. 
     At  808 , a measurement generated by the sensor may be communicated using a communication system powered by the usable electric potential. In some embodiments, the communication system may allow for wireless transmission of measurements. Such systems may facilitate installation of sensors without the need for physical connections to wired communication systems. 
     While specific embodiments and applications of the disclosure have been illustrated and described, it is to be understood that the disclosure is not limited to the precise configurations and components disclosed herein. Accordingly, many changes may be made to the details of the above-described embodiments without departing from the underlying principles of this disclosure. The scope of the present invention should, therefore, be determined only by the following claims.