Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
  • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
  • G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
  • G01R15/207—Constructional details independent of the type of device used
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
  • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks

Definitions

• the present invention relates to the field of high voltage electric power transmission and distribution systems and, more particularly, to an electric power monitoring and response system that uses a current monitoring device with electromagnetic field sensors located within a grounded housing to determine the phase currents in an electric power line.
• CTs ring-type current transformers
• these devices are quite expensive when applied at high voltages. This results, in large part, from the need to insulate the current sensors for high-voltage, which is quite expensive for voltages above 1 ,000 volts.
• electromagnetic field sensors such as a Hall Effect sensor
• this technique is complicated by electromagnetic field interference from the adjacent phases, which results in inaccurate measurements.
• the only successful technique using this type technology has been to use a ring of electromagnetic field sensors that completely encircles the conductor to balance out the extraneous error signals from other phases. This approach also requires expensive high-voltage insulation for the electromagnetic field sensors, which makes the system economically feasible only in limited situations.
• United States Patent No. 7,191 ,074 entitled “Electric Power Monitoring And Response System” describes an electric power monitoring and response system that uses remotely located electromagnetic field sensors to determine unknown power system variables, such as the phase currents, phase voltages and/or the distances from the field sensors to the phase conductors.
• this patent describes the fundamental technology, it does not address specific configurations and refinements of the electric power monitoring and response system, such as those suitable for adapting the system for installation high voltage power line support structures, such as those found in transmission and distribution substations. Accordingly, there is an ongoing need for improvements to electric power monitoring equipment specifically adapt and refined for particular applications.
• the present invention meets the needs described above through an electric power monitoring and response system for phase conductors of one or more multiphase power lines that uses electromagnetic field sensors, such as inexpensive electric wire coils, located within one or more grounded housings positioned within the combined electromagnetic fields generated by the phase conductors.
• the system also includes electronics, typically located within the grounded housings, defining impedance networks that combine the measurements received from the electromagnetic field sensors to create output signal indicative of electric current values for the phase conductors.
• the housings can be conveniently attached and electrically grounded to the type of high voltage power line support commonly found in transmission and distribution substations.
• the electric power monitoring and response system may also include a local controller that computes or calibrates the electric current values for the phase conductors based on the output signals received from the electromagnetic sensors and associated electronics.
• a control cable from the electric power monitoring and response system is typically connected to a local circuit interrupter located on the same support structure that opens an affected circuit in response to a detected current fault.
• the local controller can also be connected to a local transmitter that sends control signals to a remote controller that operates remote response equipment, such as a display, a circuit interrupting device, a voltage regulator, a voltage sag supporter, a capacitor bank, communication equipment, and reporting system.
• housing a set of electromagnetic field sensors appropriate for a single power line elongated conductive tubes or wands creates a modular current monitoring device configured to be physically attached and electrically grounded to a high-voltage power line support.
• the current monitoring device can also be connected to a local controller, such as a circuit interrupter for the associated power line. Because the electric power monitoring equipment is electrically grounded, it does not create a potential fault for the electric power line and is electrically isolated from electric system disturbances, such as current faults, voltage spikes, lightening strikes, and the like.
• the invention may be implemented as an electric current monitoring and response system for high voltage electric power lines or an electric power system including one or more electric current monitoring and response systems.
• the electric current monitoring and response system includes one or more electrically conductive, non-electromagnetic housings configured to be electrically grounded in a position within electromagnetic fields created by phase conductors of one or more multi-phase, high-voltage electric power lines.
• Each housing is preferably a modular unit configured to be connected to, physically supported by, and electrically grounded to a support structure that supports high voltage insulators that support the phase conductors, such as a support structure commonly located within a transmission or distribution substation.
• Each housing may also include an elongated slot configured to impart a desired frequency response to the electromagnetic field sensors.
• a set of electromagnetic field sensors laterally distributed within the housings are configured to simultaneously measure the combined electromagnetic fields generated by the phase conductors.
• the system also includes electronics defining an impedance network, typically located within a grounded housing, that combines the measurements received from the electromagnetic field sensors to create an output signal indicative of the electric current value for an associated phase conductor.
• the electromagnetic field sensors may be formed from a continuous wire in which the coil lengths and coil winding directions differ among the coils.
• the electromagnetic field sensors and electronics defining the impedance networks may consist of passive components that do not require an electric power source other than the electromagnetic fields generated by the phase conductors.
• a local controller may compute or calibrate the electric currents values indicative of the electric currents flowing in the phase conductors based on the output signals and to produce control signals based on the electric current values.
• the system also includes some type of response equipment that implements a response action based on the control signals.
• the response equipment may include local response equipment electrically connected to the controller, such as a circuit interrupter, and the controller may be configured to trigger operation of the circuit interrupter in response to determining that an electric fault has occurred involving one of the monitored the phase conductor based on an associated electric current value.
• the system may include a local transmitter, a remote controller, and remote response equipment such as a display, a circuit interrupting device, a voltage regulator, a voltage sag supporter, a capacitor bank, communication equipment, and reporting system.
• the invention may also be practiced as a method for obtaining electric current values for a multi-phase, high-voltage electric power line.
• An electric current monitoring system is installed within the electromagnetic fields created by phase conductors of one or more multi-phase, high-voltage electric power lines.
• the electric current monitoring system includes a set of electromagnetic field sensors laterally distributed within one or more electrically conductive, non-electromagnetic, electrically grounded housings and, for each electric current value, electronics defining an impedance network operative for combining the measurements received from the electromagnetic field sensors to create an output signal indicative of the associated electric current value.
• Known electric currents are then applied to the phase conductors and output values representing computed electric current values are obtained from the electric current monitoring system. Parameters of the electric current monitoring system are then calibrated to conform the computed electric current values to the known electric currents. The calibration equipment is then removed, and the calibrated electric current monitoring system is used to compute electric current values for unknown electric current values.
• FIG. 1 is a perspective view of a high-voltage power line support with an associated electric current monitoring and response system.
• FIG. 2 is a front view of the a high-voltage power line support and an associated electric current monitoring and response system of FIG. 1.
• FIG. 3 is a perspective view of an alternative electric power monitoring and response system with two current monitoring wands in separate grounded housings.
• FIG. 4 is a conceptual illustration of a current monitoring device with three wand located on orthogonal axes.
• FIG. 5 is a perspective view of a current monitoring device wand for an electric current monitoring and response system.
• FIG. 6 is a front view of the wand of FIG. 5 with the housing removed to reveal the interior components.
• FIG. 7 is an schematic illustration of the wand of FIG. 5.
• FIG. 8 is a conceptual illustration of a calibrated electric current monitoring and response system.
• FIG. 9 is a front view of an alternative wand for an electric current monitoring and response system that includes a tuning slot.
• FIG. 10 is a front view of another wand for an electric current monitoring and response system that includes a tuning slot with a different width.
• FIG. 1 1 is a front view of a high-voltage power line support with an internal electric current monitoring and response system.
• FIG. 12 is a side view of an alternative electric current monitoring and response system that includes a local transmitter, remote controller and remote response equipment.
• FIG. 13 is a side view of a wand for an alternative current monitoring and response system with the housing removed to reveal the interior components.
• FIG. 14 is a logic flow diagram illustrating the operation of an electric current monitoring and response system.
• FIG. 15 is a logic flow diagram illustrating a routine for calibrating an electric current monitoring and response system. DETAILED DESCRIPTION OF THE EMBODIMENTS
• the improved electric power monitoring and response system includes a current monitoring device ("CMD") in which a set of electromagnetic sensors located within one or more electrically grounded, non-electromagnetic housings.
• the grounded housings may also contain electronics defining impedance networks for combining the measurements from the sensors into current values. Placing the electromagnetic sensors and electronics within a grounded housing forms a modular unit typically referred to as a "wand" that can be easily attached to a strategically located structure within the electromagnetic field of a high voltage power line.
• one or more CMD wands can be conveniently attached directly to the support structure for a high voltage power line, such as a transmission line tower, a distribution line pole, or a disconnect switch located in a transmission or distribution substation.
• a high voltage power line such as a transmission line tower, a distribution line pole, or a disconnect switch located in a transmission or distribution substation.
• the outer housing of the wand is electrically conductive and designed to be electrically grounded, it can be conveniently grounded through metal brackets or ground straps at the time of installation.
• the CMD includes a single wand connected to a local CMD controller.
• the wand is typically installed adjacent to an electric power line, for example the wand can be mounted directly to a high voltage power line pole, tower, or disconnect switch in a substation.
• the CMD wand measures the electromagnetic field in the wand location, and the CMD controller implements computations using adjustable calibration parameters to convert or calibrate the electromagnetic field measurements into current values for the associated electric power line.
• the CMD controller implements computations using adjustable calibration parameters to convert or calibrate the electromagnetic field measurements into current values for the associated electric power line.
• the grounded housing for the electromagnetic sensors could have any desired shape, including a sphere or square box.
• the electronics could be located entirely within the grounded housings that contain the sensors, located entirely within a separate local controller, distributed between these and other components, or located in whole or in part in another enclosure or location.
• locating the sensors and impedance networks in elongated, tubular wands suitable for grounding close to the electric power lines, and locating calibration equipment in a more easily accessible local controller is a convenient and practical configuration for a distribution substation application, but other configuration may be preferred for other applications.
• CMDs designed for installation on transmission towers and distribution poles may be more conveniently deployed with all of the CMS equipment located a single housing, including internal radio equipment, and an antenna extending from the housing.
• the CMD controller is typically calibrated by obtaining known current values for the power line after the wand has been installed.
• conventional ring-type current transformers may be temporarily connected to the power line, and the adjustable calibration parameters of the CMD controller are adjusted to calibrate the readings of the CMD to correspond to the measured current values obtained form the CTs .
• the CTs are then removed and the calibrated CMD is ready for service with the wand in its installed position.
• the local CMD controller is functionally connected to some type of response equipment, which may range from a local disconnect switch to a sophisticated centrally-controlled electric power control system including a wide range of equipment, such as displays and reporting systems, sectionalizing switches, circuit interrupting devices, voltage regulators, voltage sag supporters, capacitor banks, communication equipment, transmission or distribution interconnect switches, generation stations, and so forth.
• a robust system of CMDs distributed throughout an electric power system can be used to monitor line currents and other values (it should be noted here that variations of the current monitoring CMD can be used to monitor line voltages and physical sag, as described in U.S.
• a robust system of CMDs deployed in strategic locations throughout an electric power system provides a technically and economically feasible way to obtain real-time knowledge of electric power operating conditions throughout the system and, as a result, provides the ability to respond quickly, effectively, and in many cases automatically to system disturbances from relatively minor to potentially severe.
• the CMDs further allow system operators to monitor changes in system operating conditions in real time as they implement response actions to potentially serious or dangerous system conditions. It should therefore be appreciated that a robust system of CMDs and response equipment provides an effective way to detect and respond to electric power system disturbances before they multiply and become unstable, resulting in the types of cascading faults that have plagued the U.S. electric grid with major blackouts in recent years.
• the particular CMD shown in the figures and described below has a number of important attributes.
• the basic devices shown in the figures include only one or two wands connected to a local controller, any number of wands may be connected to any number of controllers to improve accuracy and system control.
• multiple wand stations, each having multiple wands positioned in different orientations and elevations, may be deployed in strategic locations in a multi-line substation.
• a multi-wand CMD with a sufficient number of properly distributed electromagnetic sensors can be used to monitor all of the line currents in a complex substation with sufficient accurately to automatically operate disconnect switches, circuit breakers and other fault response equipment within the substation.
• SCADA Local substation communication and control equipment
• SCADA Local substation communication and control equipment
• CMDs can also be installed on distribution line poles and transmission line towers along many or perhaps all of the significant transmission and distribution lines in the power system to monitor line conditions throughout the electric power grid.
• Communication equipment in the power line CMDs can be used to send the current monitoring information for the power lines to the central control station, for an improved degree of system monitoring and control.
• each conventional electric system monitoring station rely on current and voltage sensors at line voltage and, and a result, each sensor presents a potential source of electric system fault. That is, one would not install hundreds or thousands of conventional CT current sensors on every power line support in every substation, and on power line poles and towers on every power line throughout the electric power system, because each CT could malfunction, for example as a result of a lightening strike, and itself cause an electric fault.
• conventional current and voltage monitoring technology in other words, the benefit of greater system knowledge is offset by the detriment of increasing the number of potential fault locations in the system.
• the CMD wands of the present invention cannot cause electric faults because they are electrically grounded. Hundreds, or even thousands, of these devices can be deployed throughout the electric power grid without increasing the number of potential electric fault locations. This difference is an important distinction separating the CMD of the present invention from conventional CTs, opening a new category of inexpensive, electrically grounded current monitoring devices for high voltage electric power lines.
• the frequency response of the CMD wand can be adjusted by placing a thin elongated tuning slot in the outer, grounded housing.
• the grounded housing is formed from a non-electromagnetic, electrically conductive material, such as aluminum or stainless steel, it serves as an electrostatic shield regardless of whether it has a slot.
• the frequency response of the wand as an electromagnetic shield can be adjusted by placing a tuning slot along the housing. With no slot, the housing typically shields high frequency electromagnetic signals down to less than the thousand Hertz range. Placing a tuning slot in the casing, however, allows high frequency electromagnetic signals to enter the wand, where they are picked up by the internal electromagnetic sensors.
• the width of the tuning slot can be selected to impart a desired frequency pass response to the wand.
• the electric power engineer is typically interested in measuring the harmonic content of the electric power flowing on the monitored power line up to about the 15th to 30th harmonic. This application calls for a sufficient wide slot to allow the desired harmonic content up to several thousand Hertz range to pass through the shield.
• the accuracy of the CMD can be improved by using a single wire to form multiple coils along the wand, in which the winding direction and number of turns in the coils vary among the coils.
• the CMD wand can be implemented with entirely passive electromagnetic sensors (e.g., wire coils) and electronics (e.g., impedance networks) that operate entirely from power induced from the electromagnetic field of the monitored electric power line.
• the CMD controller could also be implemented with entirely passive components, although there are significant advantages to separately powering the CMD controller, such as allowing communication equipment in the CMD controller to operate regardless of whether the monitored power line is energized.
• the skilled electric power engineer will appreciate that many variations of the basic CMD may be implemented once the underling principles are understood. The following description of specific embodiments, with reference to the figures, will help to further illustrate those underling principles in the context of specific embodiments for practicing the invention.
• FIG. 1 is a perspective view and FIG. 2 is a front view of a high- voltage power line support 10 with an associated electric current monitoring device (“CMD”) system 30.
• CMD electric current monitoring device
• This particular high-voltage power line support is a circuit interrupter (also called a disconnect switch) typically found in an electric power distribution substation.
• the same type of CMD can be installed on a higher voltage transmission line in connection with an associated circuit breaker, on a transmission line tower, on a distribution line pole, and in many other strategic locations in an electric power system.
• the CMD 30 shown in FIGS 1 and 2 is a relatively simple and highly desirable example of the invention because electric power distribution lines are very numerous and vulnerable to a wide range of line faults and disturbances from lightening, tree limbs, animals, motor switching, and so forth.
• This particular high-voltage power line support 10 is designed for a three-phase power line, and therefore includes three similar conductor supports 12a-c.
• the high- voltage power line support 10 includes an insulator support for a three-phase power line and a circuit interrupter or disconnect switch for the power line. Referring to the conductor support 12a, it includes a lower high voltage bus 13a and an upper high lower high voltage bus 15a separated by a circuit interrupter 14a. An insulator 16a separates the lower high voltage bus 15a from a support structure 20, which is electrically grounded and physically supports the associated power line.
• the three conductor supports 12a-c are arranged in a line on top of the support structure 20.
• a controller 22 located under the support structure 20 operates the circuit interrupters 14a-c.
• the circuit interrupter includes a penetrating contactor located within a hollow insulator that is filled with a dielectric gas, typically SF 6 .
• the exterior of the insulators are the visible portions of the circuit interrupters 14a-c shown in FIGS. 1 and 2.
• the penetrating contactors are operated by a toggle mechanisms located within the caps located on top of the conductor supports 12a-c, and the controller 22 operates a motor that actuates a push rod that triggers the toggle mechanisms to open and close the penetrating contactors, which are typically operated together.
• the CMD 30 includes a wand 32 and a CMD cable 36 connecting the wand to a
• the CMD controller 34 is typically electrically grounded and physically connected to the support structure 20 by one or more metal brackets.
• the outer housing of the wand is made from a non-electromagnetic, electrically conductive material, such as aluminum or stainless steel.
• a controller cable 37 connects the CMD controller 34 to the controller 22 for the circuit interrupter. The allows the circuit interrupters 14a-c to be operated in response to the measurements obtained by the CMD 30 of the currents flowing in the conductors of the three-phase electric power line supported by the high-voltage power line support 10.
• the CMD controller 34 may also include (internal or external to the box indicated as the CMD controller) communication equipment, such as SCADA equipment, transmitting the current measurements to a remote controller and associated remote motoring and response equipment.
• the remote motoring and response equipment may include a wide variety of local and remotely located electric power system resources, such as circuit breakers, voltage regulators, capacitor banks, voltage sag supporters, sectionalizing switches, interconnect switches, generating stations, central displays, reporting and analysis systems, and so forth.
• FIG. 3 shows an alternative CMD configuration, in which the single CMD wand 32 shown in FIGS 1 and 2 has been replaced by a pair of wands 33a-b in separate grounded housings.
• the wands 33a-b are collinear, but that need not be the case.
• the CMD may include multiple wands installed in different orientations and elevations. This is illustrated conceptually in FIG. 4, which shows three wands 35a-c located along orthogonal axes.
• several CMD wand stands with multiple wands in different orientations could be located in strategic positions in a complex substation to simultaneously measure the line currents in multiple transmission and distribution lines. If the CMD wands are not directly supported by a grounded structure, a ground strap can be used to connect the wands to the substation ground grid, a nearby grounded structure, or a ground rod installed for the CMD wand.
• FIG. 5 is a perspective view of the CMD wand 32, which can include any suitable type of electrically conductive, non-electromagnetic tube that serves as a grounded housing or container 40.
• the housing is shown as a tube with a square crosssection, which is amenable to having a flat base supporting the internal coils and circuit boards.
• the tube could also be a round pipe or any other suitable structure.
• the sensors and electronics may be located on a removable plate, and the tube may include a hinged side, doors or windows, as desired, to allow access to the internal components.
• FIG. 6 shows the CMD wand with the housing 40 removed to reveal the internal components, which in this simple example includes four wire coils 44a-d and two electronics boards 46a-b.
• the first electronics board 46a implements impedance networks for the coils 44a-b
• the second electronics board 46b implements impedance networks for the coils 44c-d.
• the coils 44a-d may be wound from a single wire 48, and the four coils may have different numbers of turns, with some coils winding clockwise and others winding counterclockwise.
• FIG. 8 is a conceptual illustration for calibration of the CMD 30, which may be installed in a potentially complex electrostatic and electromagnetic environment 52, such as an electric power substation with multiple electric power lines at different voltages located at different elevations extending in different directions.
• the electromagnetic environment may also include one or more sources of electromagnetic and electrostatic interference 54.
• any large metal structure such as a transformer or oil tank, would present source of electrostatic interference, which could potentially be non-linear as experienced at the CMD wand.
• the interference source might also be electromagnetic, in which case it could also present a source of electromagnetic interference, again potentially nonlinear.
• an electrostatic and electromagnetic environment involving multiple power lines at multiple orientations and voltages can be extremely complex to model mathematically based on theoretical calculations.
• FIG. 9 is a front view of the wand 32 for an electric current monitoring and response system that includes a tuning slot 70 in the grounded housing 40.
• FIG. 10 shows the wand with a housing having a slightly wider tuning slot 80.
• the tuning slot adjusts the frequency response of the wand, as described preciously.
• a housing with no slot shields high frequency electromagnetic components down below the thousand Hertz range.
• the tuning slot allows higher frequency electromagnetic components to enter the housing , where they can be registered by the internal coils.
• the frequencies passed by the slot are controlled by the width of the slot, with a wider slot allowing higher frequencies to pass into the housing .
• the electric power engineer is usually interested in measuring the harmonic content of the currents on the power line up to about the 15th to the 30th harmonic (i.e., 900 to 1 ,800 Hz), and frequencies above about the 10th to 15th harmonic (i.e., 600 to 900 Hz) may be shielded by a wand housing with no tuning slot. Therefore, the tuning slot should be sufficiently wide to allow the desired harmonic content to be measured by the wand.
• FIG. 1 1 is a front view of a high-voltage power line support 90 with an internal electric current monitoring and response system including a CMD wand 92 and a CMD controller 94 located inside the power line support itself.
• This is a convenient configuration for new power line supports, whereas the external CMD shown in FIG. 1 can be readily installed on existing power line supports.
• FIG. 12 Another alternative is illustrated in FIG. 12 by the CMD 100, which includes a local transmitter 102, remote controller 104, and remote response equipment 106.
• this configuration allows CMDs throughout an electric power system to be integrated for a wide range of electric power monitoring and response activities, for example from a central control station.
• FIG. 13 conceptually illustrates multiple coils 110 and multiple electronics board 112 within the CMD wand 100. In general, varying the size, spacing, number of coils, and winding directions among the coils can improve the accuracy of the CMD.
• FIG. 14 is a logic flow diagram illustrating a routine 120 for calibrating and operating the CMD 30 shown in FIG. 1. In routine 122 (shown in greater detail in FIG.
• step 122 is followed by step 124, in which the CMD monitors the associated electric power line and detects a current fault on the power line.
• step 124 is followed by step 126, in which the CMD 30 sends a disconnect signals to the controller 22 for the circuit interrupter.
• step 126 is followed by step 128, in which the controller 22 activates the circuit interrupters 14a-c to open the associated electric power lines.
• FIG. 15 is a logic flow diagram illustrating routine 122 for calibrating the CMD 30.
• the CMD wand 32 is installed and electrically grounded within the electromagnetic field of the associated electric power line, as shown in FIG. 1.
• the CMD controller 34 is also installed and the necessary cables 36, 37 are connected.
• step 132 is followed by step 134, in which temporary calibration equipment is installed. In particular, conventional CTs can be temporarily installed to measure the currents flowing on the phase conductors of the monitored power line.
• step 134 is followed by step 136, in which the calibration equipment is used to obtain known measurements for the line currents.
• step 136 is followed by step 138, in which adjustable calibration parameters of the CMD are adjusted to match the line currents computed by the CMD to the known current values.
• each line current is typically computed as a weighted sum of the sensor values received from the various electromagnetic sensors.
• the weighting factors applied to signals received from various electromagnetic sensors are typically adjusted until the CMD computed all of the line currents correctly. Different current levels with different conductors energized can be tested to ensure that the CMD works acceptably for a reasonable range of current values that it is likely to encounter.
• Step 138 is followed by step 140, in which the temporary calibration equipment is removed, and in step 142 the calibrated CMD is used to monitor the power line.

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• 2007
  • 2007-07-09 CN CN200780032664A patent/CN101646950A/zh active Pending
  • 2007-07-09 WO PCT/US2007/073050 patent/WO2008008726A2/en active Application Filing
  • 2007-07-09 EP EP07812723A patent/EP2038662A2/de not_active Withdrawn

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