阅读说明：本技术 使用线装设备的单端行波故障定位 (Single ended traveling wave fault location using a wire-bound device ) 是由 埃德蒙德·O·施维泽三世 雷蒙德·W·赖斯 于 2019-10-01 设计创作，主要内容包括：一种线装设备用于向设备提供电力系统信号以检测故障并使用由此发起的行波来计算故障位置。所述线装设备处的电流用于分离端子处的入射行波和反射行波。比较经过所述线装设备和所述端子的行波的时间和极性,以确定所述故障是位于所述端子与所述线装设备之间还是位于超出所述端子或所述线装设备的位置。可使用来自所述线装设备的电流来计算所述行波的电压。(A line-bound device is used to provide power system signals to the device to detect faults and calculate fault locations using traveling waves initiated thereby. The current at the line mounted device is used to separate the incident traveling wave and the reflected traveling wave at the terminal. Comparing the time and polarity of the traveling wave through the line mounted device and the terminal to determine whether the fault is located between the terminal and the line mounted device or beyond the terminal or the line mounted device. The voltage of the traveling wave may be calculated using the current from the line mounted device.)

1. A system for detecting a location of a fault on a power delivery system, comprising:

a wirebound apparatus at a first location on the power delivery system, comprising:

a power supply for providing operating power to the wirebound apparatus;

a current transformer in electrical communication with the power delivery system at the first location for obtaining an electrical signal related to the current at the first location;

a signal processor in communication with the current transformer to receive the electrical signal and provide a first position current measurement; and the number of the first and second groups,

a transmitter in communication with the signal processor configured to transmit a first position current measurement;

a protection device in electrical communication with a second location on the power delivery system, the first location being a known distance from the second location, the protection device comprising:

a communication interface in communication with the transmitter of the line mounted device to receive the first position current measurement;

an excitation input to obtain a power system signal from the second location;

a signal processor for processing the power system signal from the excitation input;

a traveling wave detector in communication with the signal processor and the communication interface to:

determining a time and polarity of a traveling wave at the first location using the first location current measurement; and

determining a time and polarity of the traveling wave at the second location; and

a fault locator in communication with the traveling wave detector to determine a location of a fault using the time and polarity of the traveling wave at the first and second locations.

2. The system of claim 1, wherein the traveling wave detector is configured to calculate a voltage of the traveling wave at the second location using the first location current measurement and a known impedance.

3. The system of claim 1, wherein the transmitter comprises a fiber optic transmitter.

4. The system of claim 1, wherein the transmitter comprises a radio frequency transmitter.

5. The system of claim 1, wherein the power source is in electrical communication with a supply current transformer, the supply current transformer being in electrical communication with the power delivery system.

6. The system of claim 5, wherein the power source comprises a rectifier for rectifying alternating current from the power delivery system to direct current for use by the line mounted device.

7. The system of claim 1, wherein the fault locator determines that the location of the fault is within the known distance between the first location and the second location when the polarity of the traveling wave at the first location is opposite the polarity of the traveling wave at the second location.

8. The system of claim 1, wherein the fault locator determines that the location of the fault is outside the known distance between the first location and the second location when the polarity of the traveling wave at the first location is the same as the polarity of the traveling wave at the second location.

9. The system of claim 8, wherein the fault locator determines that the location of the fault is on the same line as the line mounted device when the traveling wave is at the second location later in time than the fault is at the first location.

10. The system of claim 8, wherein the fault locator determines that the fault is located on a different line than the line of wire device when the traveling wave is at the second location earlier in time than the fault is at the first location.

11. The system of claim 9, wherein the fault locator determines the distance to the fault using a traveling wave detected with the power system signal from the second location.

12. The system of claim 1, wherein the signal processor of the line mounted device comprises a modulator.

13. The system of claim 1, wherein the signal processor of the line mounted device comprises a phase locked loop and a voltage controlled oscillator.

14. The system of claim 1, wherein the signal processor of the wirebound apparatus comprises:

an analog-to-digital converter for sampling and digitizing the electrical signal from the current transformer; and

a buffer to store the digitized electrical signal.

15. The system of claim 14, wherein the transmitter is configured to continuously transmit the stored digitized electrical signals.

16. The system of claim 14, further comprising an analog trigger for determining a fault and initiating transmission of the stored digitized electrical signal.

17. A method for calculating a location of a fault in a power delivery system, comprising:

detecting a first observation of a traveling wave at a first location on the power delivery system, the first observation comprising a first polarity of the first observation of the traveling wave;

detecting a second observation of the traveling wave at a second location of the power delivery system using a power delivery system signal, the power delivery system signal obtained using a line mounted device at a predetermined distance from the first location, the second observation comprising a second polarity of the second observation of the traveling wave; and

determining that the location of the fault is between the first location and the second location when the first polarity is opposite the second polarity.

18. The method of claim 17, further comprising determining that the location of the fault is not between the first location and the second location when the first polarity is equal to the second polarity.

19. The method of claim 18, further comprising:

when the time of the second observation value is earlier than the time of the first observation value, determining that a power line where the fault position is located is the same as a line where the second position is located; and

and when the time of the second observation value is later than that of the first observation value, determining that the power line where the fault position is located is different from the line where the second position is located.

20. The method of claim 17, further comprising the wirebound apparatus modulating the power delivery system signal and transmitting the modulated signal to an intelligent electronic device at the first location.

21. The method of claim 17, further comprising the wirebound apparatus sampling and digitizing the power delivery system signal and transmitting the digitized signal to an intelligent electronic device at the first location.

22. The method of claim 17, further comprising the wirebound apparatus continuously transmitting power delivery system signals to an intelligent electronic device at the first location.

23. The method of claim 17, further comprising the wirebound apparatus periodically transmitting a power delivery system signal to an intelligent electronic device at the first location upon detection of a fault.

24. A method for calculating a location of a fault in a power delivery system, comprising:

detecting a first observed value of a traveling wave at a first location on the power delivery system, the first observed value of the traveling wave comprising a sum of an incident traveling wave and a reflected traveling wave at a terminal of the power delivery system;

detecting a second observation of the traveling wave at a second location of the power delivery system using a power delivery system signal, the power delivery system signal obtained using a line mounted device at a predetermined distance from the first location, the second observation comprising a current at the second location; and

calculating a traveling wave characteristic at the first location using the current at the second location and a known system impedance; and the number of the first and second groups,

calculating a distance to the fault using the calculated traveling wave characteristic.

25. The method of claim 24, further comprising:

detecting, at the first location, an arrival time of a reflection of the traveling wave from the fault;

wherein the traveling wave characteristic comprises a time of arrival of the traveling wave at the first location; and is

Wherein the step of calculating the distance to the fault uses a traveling wave propagation speed and a time difference between an arrival time of the traveling wave at the first location and an arrival time of a reflection of the traveling wave from the fault.

Technical Field

The present disclosure relates to improvements in the calculation of fault locations in power delivery systems. More particularly, the present disclosure relates to a system for determining the location of a fault by detecting and differentiating traveling wave incidence and reflection at a single end of a power delivery system using signals from a line mounted device.

Drawings

Non-limiting and non-exhaustive embodiments of the present disclosure are described, including various embodiments of the present disclosure with reference to the accompanying drawings, in which:

fig. 1A shows a simplified single line diagram and associated timing diagram of a traveling wave initiated by a fault on an electrical power delivery system.

Fig. 1B shows a simplified single-line diagram including a representation of the incident, transmitted and reflected portions of a traveling wave at one terminal.

Fig. 1C shows a traveling wave timing diagram of a fault near a terminal of the power delivery system.

Fig. 2 shows a simplified single-line diagram of a power delivery system that uses Intelligent Electronic Devices (IEDs) and line mounted devices for monitoring and protection according to several embodiments described herein.

Fig. 3 shows a single line diagram of a power delivery system with a fault and a timing diagram of a traveling wave initiated by the fault.

Fig. 4 shows a single line diagram of a power delivery system with a fault at a different location than the fault of fig. 3, and a timing diagram of a traveling wave initiated by the fault.

Fig. 5 shows a single line diagram of a power delivery system with a fault and a timing diagram of a traveling wave initiated by the fault.

Fig. 6 shows a simplified block diagram of a system for locating faults using signals from the IED and the analog line mounted device.

Fig. 7 shows a simplified block diagram of a system for locating faults using signals from the IED and the analog line mounted device.

Fig. 8 shows a simplified block diagram of a system for locating faults using signals from the IED and the digital line-mounted device.

Fig. 9 shows a simplified block diagram of a system for locating faults using signals from the IED and the digital line-mounted device.

Fig. 10 shows a simplified circuit diagram of a system for supplying power to a line mounted device and transmitting a direct waveform through an optical fiber.

Fig. 11 shows a simplified circuit diagram of a system for supplying power to a line mounted device and transmitting an analog signal over an optical fiber.

Fig. 12A shows a simplified circuit diagram of a system for supplying power to a wirebound apparatus and transmitting via radio frequency.

Fig. 12B shows a simplified circuit diagram of a system for supplying power to a wirebound apparatus, collecting samples, and transmitting via radio frequency.

Fig. 13 shows a simplified circuit diagram of a system for supplying power to a wirebound apparatus and transmitting analog signals over radio frequencies.

Fig. 14 shows a simplified circuit diagram of a system for powering a line mounted device and continuous digital capture by radio frequency transmission.

Detailed Description

Embodiments herein describe improvements to techniques for detecting and locating faults on electrical power systems. The improvement comprises using the line mounted device to provide power system information that can be used to distinguish between incidence and reflection of traveling waves initiated by a fault. Traveling waves at a single end of the power system may be used to detect faults and determine the location of the fault using the traveling wave principle.

The time between an incident traveling wave observed at a single end of a power line and a reflection from a fault location can be used to determine the fault location. Accurate measurements of the arrival time of the traveling wave are required to accurately calculate the position. At the terminals, the traveling wave voltage and current are measured as the sum of the incident traveling wave and the reflected traveling wave. Determining the traveling wave characteristics requires separating the incident and reflected waves. It has proven difficult to separate the incident traveling wave and the reflected traveling wave at the terminals using the existing instrument transformers. Furthermore, in many devices, existing instrument transformers may not provide a signal sufficient to accurately distinguish between an incident traveling wave and a reflection from the location of the fault when the fault is near the terminals. What is needed is a system for separating an incident traveling wave and a reflected traveling wave to provide accurate traveling wave characteristics for fault detection. What is also needed is a system for distinguishing between incident traveling waves and reflections from the location of a fault even when the fault occurs near the terminals. Disclosed herein are devices and systems for detecting faults and determining the location of the fault from traveling waves at a single end of a transmission line. Embodiments disclosed herein may use existing instrument transformers and wire-bound devices.

Embodiments of the present disclosure will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. 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 present disclosure is not intended to limit the scope of the disclosure as claimed, but is merely representative of possible embodiments of the disclosure. Moreover, unless otherwise specified, the steps of the methods need not necessarily be performed in any particular order, even sequentially, nor need the steps be performed only once.

Several aspects of the described embodiments may be implemented as software modules or components. In some embodiments, a particular software module or component may include different instructions stored in different locations of a memory device that together implement the described functionality of the module. Indeed, 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 distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network.

Fig. 1A shows a timing diagram of the incidence and reflection of a traveling wave initiated by a fault 150 at time t 0 on line 102 of the power delivery system. A fault 150 at a location m from the terminal 104 initiates traveling waves in both directions. Wave from fault towards line terminal L104 and R106. Timing diagram 170 shows the timing of traveling wave propagation. Initial incident traveling wave at time t₁To terminal L104. A portion of the incident wave is reflected from terminal L104 back to fault location 150. A portion of the reflected wave reflects from the fault location 150 and at time t₂To terminal L104. Similar reflection at time t₃To terminal L104. At a known traveling wave propagation speed, the detected incident traveling wave t can be used₁And reflection t₂The time difference between them to calculate the distance from the fault location 150. Therefore, to determine the fault location, traveling waves and reflections as well as time need to be accurately detected.

Fig. 1B shows a portion of the single line diagram of fig. 1A, with more details of the traveling wave. As indicated above, the fault 150 initiates a traveling wave 182 toward the terminal L104. The traveling wave 182 is composed of voltage and current components, related to the characteristic impedance of the power line. When having a current i_IAnd voltage v_IReaches the line terminal 104, a part of the incident traveling wave is supplied with a current i_TAnd voltage v_TIs transmitted and the rest is supplied with a current i_RAnd voltage v_RAnd (4) reflecting. The amount of transmitted and reflected energy depends on the characteristic impedance Z beyond the transition point_TAnd the characteristic impedance Z of the line on which the wave travels_C. The device at the line terminal measures current and voltage values, which are the sum of the incident traveling wave and the reflected traveling wave. The fidelity of measuring voltage values may be low within the frequencies of interest of a traveling wave, especially when voltage measurements are made via a capacitive-coupled voltage transformer (CCVT). If the voltage can be measured accurately, the equipment at the line terminals can calculate the incident traveling wave and the reflected traveling wave accurately. Because the device is only capable of measuring v and i, and because the CCVT distorts the voltage measurements, the device is unable to accurately calculate the incident and reflected waves, and this limits the ability to accurately calculate the location of the fault.

Equations 1 and 2 show the terminal voltage v and the terminal current i as the incident voltage v_IAnd a reflected voltage v_RAnd incident current i_IAnd a reflected current i_RFunction of (c):

v＝v_I+v_R equation 1

i＝i_I+i_REquation 2

In addition, equations 3 and 4 are based on v_IAnd v_RShow i and solve for v_R：

v_R＝v_I-iZ_CEquation 4

V from equation 4_RSubstituting equation 2A and solving for v_IEquation 5 is derived:

similarly, equation 6 is obtained to represent the voltage of the reflected wave at the line terminal as a function of v and i:

equations 5 and 6 are performed for the modal current and voltage using the corresponding characteristic impedance of the line. The challenge in separating the incident traveling wave from the reflected traveling wave is to properly measure the voltage and current at the terminals. As discussed above, therefore, high fidelity voltage and current measurements at a single line end are important to distinguish between incident and reflected traveling waves. Typical instrument transformers such as CT and PT (e.g., CCVT) are optimized for use at nominal frequency conditions. The frequency of the traveling wave signal is much higher than the typical nominal frequency of the power delivery system. Dedicated high frequency transducers may be used, but the high cost and custom nature of these devices makes this approach impractical for typical power system installations. Further, instrument transformers are often already installed in the power system devices. The voltage is typically measured using CCVT tuned to the nominal signal frequency, and shows very large attenuation for higher frequencies (e.g., in the kHz and MHz range). CCVT is generally not suitable for travelling wave measurements using its standard secondary voltage output. Conventional CT has a good high frequency response, with the available pass band typically reaching 100kHz and possibly even approaching 200kHz or 500 kHz.

Therefore, the first problem is to distinguish the incident traveling wave and the reflected traveling wave by a device near the terminal to perform the fault detection and the position calculation. What is needed is a system that separates such incident traveling waves from reflected traveling waves even when existing instrument transformers are used at the terminals.

Figure 1C shows another timing diagram of the incident and reflected traveling waves initiated by fault 150. In the graph shown here, fault 150 is a close range fault, occurring only 1 mile from terminal L104. Using the known traveling wave propagation velocity, it can be seen that the time between the initial arrival of the incident traveling wave (5 μ s from the time of the fault) and the arrival time of the portion of the traveling wave reflected from the fault location (15.9 μ s from the time of the fault) is less than 11 μ s. Faults occurring closer to the line terminals result in a shorter time difference between the arrival of the incident travelling wave and the reflection from the fault. These time differences may be close to the sampling resolution of the equipment responsible for detecting and locating the fault. Thus, the instrument transformer can obscure the initial traveling wave and reflections from faults. Therefore, the second problem is to distinguish between an incident traveling wave and a reflection from a fault when the fault is close to a terminal. What is needed is a system that separates such incident traveling waves from reflections from faults.

Fig. 2 illustrates a simplified single-line diagram of a power delivery system 200 monitored by an IED210 providing fault detection and localization according to several embodiments herein. The IED210 can use signals from instrument transformers already used for traditional line monitoring and protection to detect faults and calculate fault locations according to the traveling wave principle. The IED210 can include a processor 211, and the processor 211 can include one or more general purpose processors, special purpose processors, application specific integrated circuits, programmable logic elements (e.g., FPGAs), and the like. The IED210 may also include a non-transitory machine-readable storage medium 212 having one or more disks, solid state storage (e.g., flash memory), optical media, and the like. The IED210 may communicate with a network (not separately shown) that may include a dedicated network (e.g., a SCADA network, etc.) for monitoring and/or controlling the power system 200. In some embodiments, the IED210 may include Human Machine Interface (HMI) components (not shown), such as a display, input devices, and the like.

The IED210 may also include one or more communication interfaces 213. The communication interface 213 can include a wired and/or wireless communication interface (e.g., serial port, RJ-45, IEEE 802.11 wireless network transceiver, fiber optic transceiver, etc.) for communicating with the wirebound devices 222.

The IED210 may be communicatively coupled to the power system 200 by one or more CTs, PTs (which may be implemented as CCVT, etc.), merging units, etc. The IED210 may receive the excitation 208 from the power system 200 in the form of electrical signals related to current, electrical signals related to voltage, digitized analog signals related to current and/or voltage, and the like.

The IED210 may include a plurality of protection elements, such as a traveling wave fault localization element 220, and the fault localization element 220 may be embodied as instructions stored on a computer-readable medium, such as storage medium 212, that when executed on the processor 211, cause the IED210 to detect one or more incidences of a traveling wave and calculate a location of the fault. The fault location calculation may be based on the time of the traveling wave. The traveling wave fault localization element 220 may include instructions for a traveling wave detector 244 and a fault locator 246 configured to determine a fault location. When a fault is detected within a predetermined protection zone, the IED210 may also include instructions for taking protective action, such as signaling the breaker 232 to open, thereby removing power from being fed to the fault. Protective action may be taken to prevent additional damage to the power system. In addition, the calculated location of the fault facilitates the staff to go to the location and repair the damaged equipment.

Traveling wave detector 244 may use the voltage and/or current signals to detect traveling wave incidence and reflection. The time of the traveling wave may be based on the time the signal was obtained from the power delivery system. Traveling wave detector 244 may also determine the polarity of the detected traveling wave. The fault locator 246 may use the following information to calculate the location of the fault: travelling wave related information from the travelling wave detector, and travelling wave related information using a signal obtained with the line-mounted device. The line-bound device 222 may provide processed traveling wave information (e.g., traveling wave time and polarity) or raw information from the power delivery system for processing by the IED210, or a combination thereof.

Further, the IED210 may include a monitored equipment interface 234 in electrical communication with monitored equipment (such as a circuit breaker 232). Monitored equipment interface 234 may include hardware for providing signals to circuit breaker 232 to open and/or close in response to commands from IED 210. For example, upon detection of a fault, traveling wave element 220 may signal monitored equipment interface 234 to provide an open signal to circuit breaker 232, thus effecting a protective action on the power delivery system. In some embodiments, the protection actions may be implemented by additional or separate devices, such as a merging unit.

As described above, the time difference between the incidence of the traveling wave and the reflection from the fault location can be used to calculate the distance to the fault. The fault location from a single end can be calculated using equation 7:

wherein:

m is the distance from the fault;

t_L2is the arrival time at the L terminal of the first reflection from the fault;

t_L1is the arrival time at the L terminal of the initial wavefront from the fault; and the number of the first and second groups,

v_TWis the traveling wave propagation velocity.

To address both of the problems described above, the improvements herein use a wirebound apparatus 222. The line mounted device 222 may be installed at a predetermined location on the line 202 to provide a signal that assists in determining the location of the fault. The IED210 may communicate with the tethered device 222 for receiving information related to the power delivery system at the location of the tethered device 222. In several embodiments, the line-mounted device 222 is used to provide an incident current i of a traveling wave_IIs measured. At a known impedance Z_CIn the case of (3), the incident voltage v of the traveling wave can be calculated according to equation 5_I. Thus, the incident voltage v can be determined whether or not it is possible to measure the travelling wave incident voltage and current at the terminals_IAnd the reflection from the fault can be used to calculate the fault location.

The wirebound apparatus 222 may include a power source 254 for providing power to several components of the wirebound apparatus 222. As described in more detail herein, the power source may obtain power from the power system 200, from an internal power source, and the like. The line mounted device 222 may include a signal processing module 256 that communicates with the current transformer 252 to obtain a current signal therefrom and process the signal for transmission to the IED210 via a transmitter 258. The signal processing module 256 may provide modulated analog signals for transmission, digitized signals for transmission, and the like, as disclosed in more detail herein.

The line-mounted device 222 is operable to provide a signal related to a traveling wave passing the location of the line-mounted device 222 for use by the traveling wave fault locating element 220 of the IED 210. In some embodiments, the location of the wirebound apparatus 222 may be outside the resolution region of the CCVT. For example, if the shortest resolving time is about 10 μ s, the wire-mounted sensor may be placed about one mile from the terminal where the CCVT is located. The line-mounted device 222 detects the wavefront of the traveling wave passing through the line-mounted device and its polarity; and sends information related thereto to the IED210 for use in determining the fault location using the traveling wave.

Traveling wave fault locating element 220 may use a signal from line mounted device 222 to separate the incident traveling wave from the reflected traveling wave. That is, the traveling wave current measured using the line mounted device 222 may be used to determine the traveling wave voltage (using a known system impedance). That is, the IED210 may calculate the incident traveling wave voltage using the current from the wire-bound device multiplied by the impedance. Thus, the voltage of the incident traveling wave can be calculated using the current from the line mounted device, thereby eliminating the need to separate the incident and measured traveling wave voltages at the terminals. According to this improvement, there is no need for high fidelity voltage measurements at the IED to separate the incident and reflected traveling waves.

Further, the disclosed wirebound apparatus may be used to determine if a fault: 1) between the terminal and the wire dress apparatus; 2) an out-of-line device; or 3) on another conductor. The determination is based on the relative times of arrival of the traveling wave at the terminal and the line-mounted device, and the polarity of the traveling wave at the terminal and the line-mounted device. The IED may take or block protective actions depending on the determined location of the fault.

Fig. 3 shows a simplified single line diagram of a power system monitored using the line mounted device 322 and a timing diagram of traveling waves and reflections caused by a fault 350. The system includes a remote terminal R306, a local terminal L304, and a power line 302, which can be monitored by an IED (such as IED 210) to obtain power system signals and determine fault conditions and fault locations using traveling wave principles. In addition, the wire dress device 322 is a known distance 312 from the terminal L304. The known distance 312 may be determined as a distance required for useful resolution of the voltage signal from existing equipment. The line mounted device 322 obtains power system measurements (such as current) from the line 302 and transmits information related thereto to the IED. In certain embodiments, the line mounted device 322 may transmit the current measurements to the IED. In other embodiments, the line-mounted device 322 can calculate the traveling wave properties (e.g., time, voltage, polarity, etc.) and transmit information related to the traveling wave properties to the IED. The IED may use information from the inline device 322 and information obtained by the IED to determine the location of the fault 350.

The incident traveling wave of the first polarity arrives at the line mounted device 322 at time 326 and arrives at the L terminal 304 at time 352. The line-mounted device 322 may measure the current of the incident traveling wave at the location of the line-mounted device 322. In some embodiments, the line mounted device may calculate the incident traveling wave voltage as a characteristic impedance Z_CThe product of the current measured at the line equipment 322. In still other embodiments, the voltage at the wired device may be calculated at the IED using the current measured by the wired device and transmitted to the IED. After a known time 358 (which may be near zero in various embodiments or may be related to processing time in some embodiments), the line mounted device 322 transmits traveling wave information or current measurements to the IED, which arrive at the IED at time 360.

When the incident traveling wave reaches the terminal at 352, the IED may calculate the traveling wave properties. When a fault 350 occurs outside of the line set 322 (not within zone 312), the incident wave detected using the measurements of the line set 322 and the incident wave detected using the voltage and current at terminal L304 will have the same polarity. Thus, the IED may determine that the fault is outside zone 312. The IED may determine the incident voltage wave using a voltage calculated using a current measured at the inline device and a characteristic impedance.

Thus, it may be determined that the fault is outside of region 312 (due to the time at which the incident traveling wave arrives at the line-up device before arriving at the terminal, and the incident traveling wave at the line-up device has the same polarity as the incident traveling wave at the terminal). Travelling wave incident current i measured at an in-line device 322_ICan be used for calculating the traveling wave incident voltage v_I. The IED may use measurements from the line mounted device 322 to separate the incident traveling wave from reflections from the fault location. The IED may use such a time difference to calculate the distance to the fault using the time of the initial wavefront and the time of the reflection from the fault location.

In certain embodiments, the wirebound device 322 may transmit only current measurements, and the IED may use these measurements and the system impedance to calculate the incident wave voltage at the wirebound device. In other embodiments, the line-mounted device 322 can calculate and transmit information about the incident traveling wave (such as the time at which the incident traveling wave was detected, current measurements, voltage calculations, polarity, etc.) to the IED. Communications from the wired device 322 arrive at the IED at time 360.

The IED may include a delay 358 from the line mounted device 322 and a setting of the communication travel time so that the received measurement or calculated value at time 360 may be aligned with the measurement or calculated value made at time 352 for proper comparison.

Fig. 4 shows the simplified single-line diagram of fig. 3, but with the fault 450 located between terminal L304 and the line mounted device 322 (within zone 312). The fault 450 initiates a traveling wave toward the terminal L304 and a traveling wave toward the line mounted device 322. The traveling wave front arrives at the line mounted device 322 at time 326 and arrives at terminal L304 at time 352. Traveling wave information collected at the inline device is transmitted at time 358 and arrives at the IED at time 460. The traveling wave at the line mounted device and the traveling wave at terminal L304 exhibit opposite polarities. Accordingly, the IED may determine that the fault 450 is between terminal L304 and the line mounted device 322. In addition, the resolution of the CCVT will not be sufficient for the IED to separate the incident traveling wave 352 from the reflection from the fault 454. However, because the IED determines that the fault is within zone 312, the IED may determine to take protective action against the close-range fault.

Further, the IED may determine the fault location using the arrival time 352 of the incident traveling wave at the IED and the arrival time 326 of the incident traveling wave at the inline device 322. The arrival time 326 of the incident traveling wave at the lineup device 322 may be calculated by subtracting the processing time 358 and the communication time from the receive time 460 of the communication from the lineup device 322. The location of the fault between terminal L304 and the line mounted device 322 can be calculated according to equation 8, which is expressed as the distance M of the fault 450 from terminal L304:

wherein:

SL is the section length 312 between terminal L304 and the wirebound apparatus 322;

t_Lis the arrival time 352 of the traveling wave front at terminal L304; and the number of the first and second electrodes,

t_LMDis the arrival time 326 of the traveling wave front at the line-up device, which is reported by the line-up device or calculated using processing and communication delays.

As shown in fig. 3 and 4, the polarity of the incident traveling wave using the measurement value observed at the in-line device 322 can be compared with the polarity of the incident traveling wave observed at the terminal L304. When the polarities are the same, it can be concluded that the fault is outside the zone 312. The voltage measurement from the CCVT at terminal L304 can be used to separate the incident traveling wave from the reflection from the fault. The time between the incident traveling wave and the reflection from the fault can be used to calculate the distance to the fault. When the polarities are reversed, it can be concluded that the fault is within region 312 and the voltage obtained by the CCVT at terminal L304 may not be used to separate the incident traveling wave from the reflection from the fault for calculation of the fault location. However, since the fault is known to be close to the terminal, protective action may be taken.

Fig. 5 shows another simplified diagram of a power delivery system comprising three lines 502, 504, 506. Each line may be a single conductor or each line may contain a plurality of conductors. For the illustrated example, the IED210 monitors and protects the line 506, where other IEDs (not shown) may be used to monitor and protect other lines and equipment. The fault 550 occurs on line 502. The travelling wave thus initiated travels through the terminal L304 to the other lines 504, 506. The lines 502, 504, 506 may be parallel lines as shown, radial lines, transmission lines to different substations, etc. At time 352, the IED210 detects an incident traveling wave initiated by the fault 550 on line 502. After the traveling wave propagates, the line-mounted device 322 transmits traveling wave information at time 526, which arrives at the IED at time 556. As described above, the IED compares the polarity of the traveling wave detected by the IED210 with the polarity of the traveling wave arriving at the line-mounted device 322. Since the traveling waves at the IED210 and at the line-mounted device 322 have the same polarity, and thus it is determined that the traveling wave is not between the terminal L304 and the line-mounted device 322. Further, because the traveling wave reaches terminal L304 before reaching the line-mounted device 322, the IED determines that the fault occurred after terminal 304 (not between terminal 304 and line-mounted device 322, nor between line-mounted device 322 and remote terminal R306). Thus, the IED may prevent protective action on line 506 due to the location of the fault on line 502.

Fig. 6-12 generally illustrate different embodiments of a wire-bound device that may be used to provide signals to an IED for fault detection and location calculation using the traveling wave principles described herein. Fig. 6 shows a simplified block diagram of a wirebound apparatus 622 in communication with the IED 210. The tethered device 622 can be powered using the power supply 634. In various embodiments, power supply 634 may receive power from line 202 via CT 652 or a separate CT for obtaining power from the power system. The power supply 634 may condition and supply power for use by various components of the cord set apparatus. In some embodiments, the power source may obtain power using a battery, a capacitor, or an intermittent power source (e.g., solar energy).

The CT 652 may provide the current secondary signal to a modulator 632, which modulator 632 is configured to use the current secondary signal to control the signal provided on the fiber interface 613. As used herein, "modulator," "modulation," and the like may refer to any modification of a signal used to represent a current, including, for example, changing a carrier signal (e.g., changing a frequency, amplitude, etc.) or changing a communication signal to a direct representation of the signal. The fiber interface 613 may provide an optical signal corresponding to the modulated current signal on the fiber medium 642. The fiber medium 642 may be a dedicated fiber between the line mounted device 622 and the IED 210. Optical medium 642 may be a dedicated medium or may be an optical ground fiber already present in the power system (e.g., an optical ground wire "OPGW"). The IED210 may be configured to use the modulated signal to determine the fault location according to several embodiments described above. In particular, the IED210 may use the excitation 104 to obtain local current and/or voltage signals to determine the occurrence, time, and polarity of traveling waves, and may use the communication interface 213 to receive current information from the tethered device 622 to determine the traveling wave occurrence, time, and/or polarity at the location of the tethered device 622. Using the traveling wave information at the location of the terminal and the line-mounted device, the IED210 can be configured to use the techniques described herein to determine whether the fault is within the zone 312 (opposite polarity), outside the zone 312 on the same line (same polarity, traveling wave arrives at the line-mounted device before arriving at the terminal), or outside the zone 312 on another line (same polarity, traveling wave arrives at the terminal before arriving at the line-mounted device).

The IED210 may have stored on the medium 642 the predetermined time delay associated with processing and communication time of the wired device 622. The predetermined time delay may be relatively constant. The predetermined time delay may be tested based on testing of the line mounted equipment, the length of the fiber optic medium 642, and the known propagation speed of light through the fiber optic medium 642. The IED210 may use a predetermined time delay to calculate the time that the traveling wave passes through the CT 652 of the line-mounted device 622.

Fig. 7 shows a simplified block diagram of a wire-bound device 722 that communicates with the IED210 using a radio frequency communication system, similar to the system described in fig. 6. A CT 652 in communication with the modulator 632 is configured to modulate the radio interface 713. The radio interface 713 provides radio signals corresponding to the modulated current signals using a suitable medium. As described above, the modulated current signal is provided for use by the IED 210.

Fig. 8 shows a simplified block diagram of another system for determining the location of a fault using signals available from instrument transformers and traveling wave principles. The signal from the CT 652 may be sampled and digitized using an a/D converter 832. The digitized analog signal from a/D converter 832 may be provided to processor 834. The various components, such as the time source 836, the processor 834, and the computer-readable storage medium 840 may communicate directly or using additional components (via the bus 838).

The time source 836 may be any suitable time source, such as a crystal oscillator, temperature compensated crystal oscillator, etc., or may obtain a time signal from a common time source, such as a Global Navigation Satellite System (GNSS), WWB signal, WWVB signal, etc., or even a time signal distributed over a common network using, for example, IEEE-1588, NTP, SNTP, etc.

The computer-readable storage medium 840 may be a repository of various computer instructions for execution on the processor 834 to cause the tethered device to perform certain functions. The instructions may include instructions that, when executed, cause the wirebound apparatus 822 to determine traveling wave occurrence, time, and polarity using the digitized analog signals. Based on this determination, the processor may format the communication including the traveling wave properties and cause the communication to be transmitted to the IED210 via the fiber medium 642 using the fiber interface 613. Although embodiments are described using a processor and instructions stored on a computer-readable medium, any such processing mechanism may be used to perform the present tasks. For example, a Field Programmable Gate Array (FPGA) with resident instructions may be used. An Application Specific Integrated Circuit (ASIC) or the like may be used. In another embodiment, the instructions, when executed, cause the wirebound apparatus 822 to obtain, format, and transmit the current measurement to the IED210 via the interface 613 for use by the IED to determine the traveling wave properties.

Furthermore, the known time delay from the CT 652 to the receipt of the communication at the communication interface 213 of the IED may be known. The IED210 may be configured to use the transmitted information related to the detected traveling wave and the known time delay to determine when the traveling wave passes the CT 652 and use this with the polarity to determine the location of the fault as described above.

In one embodiment, the line mounted device may process the digitized analog signals to determine and transmit traveling wave information to the IED 210. In another embodiment, the line mounted device may continue to monitor the power delivery system and transmit information related to further reflections of the traveling wave to the IED 210. In still other embodiments, the line-mounted device may constantly transmit digitized analog information from the a/D converter to the IED210 for processing by the IED210 to detect traveling wave and traveling wave information therefrom. In yet another embodiment, the line mounted device may be configured to detect the traveling wave and, upon detection, may transmit a communication with the traveling wave information and begin a continuous flow of digitized analog signals from the a/D to the IED 210. Variations in such transmissions are also contemplated. The power system information may be transmitted continuously or only when the line equipment detects a fault.

Fig. 9 shows a simplified block diagram of yet another system, similar to that of fig. 8, except that communications from the wire-bound device 922 are provided to the IED210 using a radio interface 713 and radio frequency signals.

Returning to several embodiments described and illustrated in fig. 6-9, during nominal operation of the power system, the line mounted device may remain in a sleep or low power mode. In this mode, the line mounted device may not send a communication to the IED210, or may only periodically send a communication or heartbeat signal indicating that the line mounted device has not detected a fault. During this low power mode, the tethered device can use the power supply 634 to obtain and store power for use whenever needed. The line mounted device may include circuitry for detecting a current surge and initiate an active mode. During the active mode, the line mounted device may transmit communications to the IED 210. For example, the analog embodiments shown in fig. 6 and 7 may begin transmitting modulated signals to the IED 210; the digital embodiment shown in fig. 8 and 9 may begin processing the digitized analog signal and transmitting the communication upon entering the active mode (detecting a fault) as described above.

The power supply 634 may include a power storage device of sufficient capacity to provide power to the various components of the line mounted device 922 during a period of time sufficient to detect and communicate information related to the fault. In one embodiment, the power storage device may be a capacitor of sufficient size to power the various components of the line mounted device 922 for at least the time it takes the traveling wave to traverse the power line four times. Even if a fault occurs at the other end of the line, it is sufficient to detect the first occurrence of a travelling wave, a reflection from the location of the IED and a reflection from the location of the fault.

Fig. 10-14 show circuit diagrams of several embodiments of a line-powered line mounted device for sending information to an IED for fault location. Fig. 10 shows a simplified circuit diagram for providing power and transmitting an analog signal proportional to current via a fiber optic medium 642. The illustrated embodiment uses direct waveform transfer over a fiber optic medium. The first supply CT 1002 may be in electrical communication with the rectifier 1004 to rectify the alternating current to a direct current for the regulator 1006. The regulated power is supplied to various components of the line installation 1022. The measurement CT 1010 produces a scaled version of the current on the power line on which it is installed. Resistor 1016 provides a path for the scaled current and produces a voltage that is scaled according to the current. The resistance of 1016 is small enough compared to the sum of the resistances of 1018 and 1020 that the voltage measured at the node common to 1016 and 1018 with respect to ground is nearly symmetrical about ground, i.e., the DC current through the coil of the CT 1010 is small. The node common to resistor 1020 and resistor 1018 is a voltage source for the + terminal of operational amplifier 1012. This voltage is representative of the current in resistor 1016 to which the DC voltage is added. The purpose of this DC voltage is to have the operational amplifier 1012 always bias the optical component 1014 so that it produces light for all desired current levels (including negative currents) in the resistor 1016. Resistor 1021 converts the current through optical component 1014 to a voltage such that operational amplifier 1012 can drive the current through the optical device as a scaled representation of the voltage at the + terminal of operational amplifier 1012. A light source (e.g., a light emitting diode, a Vertical Cavity Surface Emitting Laser (VCSEL)1014, etc.) may emit a signal onto medium 642 as a scaled version of the on-line current.

Fig. 11 shows another simplified circuit diagram for providing a continuous frequency modulated signal corresponding to the current at the wire-mounted device 1122. In addition to providing power to the components of the wirebound apparatus 1122, a rectified and regulated power signal is provided to the bias current source 1108. The current signal from the measurement CT 1010 is conditioned using a signal conditioner 1112 and provided to a Voltage Controlled Oscillator (VCO)1114, the voltage controlled oscillator 1114 driving a light source 1014 for providing a frequency modulated optical signal to the IED via an optical fiber 642. The bias current from the power supply 1108 pushes the operation of the light source 1014 above its threshold current to allow the VCO 1114 to make a negative transition without turning off the light source 1014. In addition, a low pass filtered signal representative of the current in the VCSEL is used to generate a feedback signal 1132, and this feedback signal 1132 is used by a bias current source to adjust the bias current to a predetermined value. The signal entering the low pass filter may be generated by an optical monitoring device 1142 optically coupled to the VCSEL. Thus, an analog frequency modulated signal corresponding to the current is continuously provided to the IED via the optical fiber for determining the fault location using the traveling wave properties as disclosed above.

Fig. 12A shows another simplified circuit diagram that may be used to provide power system measurements using radio frequency transmission upon fault detection. The power supply CT 1002 provides current to the power block 1202, which power block 1202 may include the various elements (such elements may include, for example, surge suppressors, maximizing capacitors, energy storage devices, buck converters, etc.) necessary to provide rectified DC power to the components of the wirebound 1222 as described above. Such power may be selectively supplied using a switch 1204 operated by an analog trigger 1206. Analog flip-flop 1206 receives a signal from measurement CT 1010 that is representative of the current of the power system. The high pass filter 1208 may be used to filter out signals at a nominal frequency (e.g., 60Hz or 50Hz, depending on the power system). The residual signal is between the upper and lower thresholds of the window detector 1210. Upon exceeding either threshold, the window detector 1210 closes the switch 1204 to power the signal conditioning 1212, the processor 1214, and the transmitter 1220 for transmitting the digitized analog signals to the IED.

Signal conditioning 1212 may include an anti-aliasing filter and signal gain. The conditioned signal representing the current is provided to the microprocessor 1214 for conversion of the analog signal to a digitized signal, storage and transmission to the IED. The microprocessor may include (or be associated with) an analog-to-digital converter (a/D)1218 for sampling and digitizing analog input. The microprocessor may include (or be associated with) an interface, such as a Serial Peripheral Interface (SPI)1216 for transmitting digital signals to the RF transmitter 1210 and to the IED via wireless dielectric 1224. Thus, the line mounted device may, upon detecting a fault, store information about the detected fault and transmit the stored information to the IED via radio frequency.

Fig. 12B shows a simplified circuit diagram for digitizing and buffering power system information and sending the digitized power system information to the IED upon detection of a fault, similar to the embodiment shown in fig. 12A. The a/D and buffer section 1260 continuously receives power from the power block 1202. The conditioned signal from 1212 is sampled and digitized using a/D1262, with the samples stored in a circular buffer 1264. Buffer 1264 may be used with microprocessor 1214 so that when a fault is detected by analog trigger 1206, switch 1204 is closed and the processor may obtain the samples stored in buffer 1264 for transmission. The processor 1214 may be configured to transmit samples from immediately before and during the occurrence of the fault. In some embodiments, processor 1214 may continue to send samples from the buffer for a period of time after the failure detection. Thus, the circular buffer can be used to take power system measurements before and during a fault and transmit them to the IED via radio frequency when a fault is detected.

Fig. 13 shows a simplified circuit diagram for transmitting an analog signal corresponding to a current via radio frequency. The illustrated embodiment may only transmit periodically when a condition is detected that a signal should be transmitted. The power supply CT 1002 obtains power signals from the power system for rectification 1004 and conditioning 1006 to provide operating power to the various components of the wirebound apparatus 1322. Measurement CT 1010 obtains a secondary current that is converted to a voltage signal in resistor 1016. This signal is provided to a Phase Locked Loop (PLL) Voltage Controlled Oscillator (VCO) synthesizer 1304 for providing a modulated signal related to the current on the power system to a radio frequency power amplifier 1306. Thus, the wirebound apparatus 1322 is continuously ready to transmit a pending activation of the power amplifier 1306. The filtered signal from filter 1208 is provided to window detector 1210, which operates as described above. While the assertion window detector 1210 is active, the time-out device 1308 provides an enable signal to the power amplifier 1306 to allow for RF transmission of signals for a predetermined time associated with the time-out device 1308. Thus, the line mounted device 1322 sends analog power system signals to the IED via RF only when a fault is detected.

Fig. 14 shows a simplified circuit diagram for continuous digital acquisition and periodic transmission from the in-line device 1422 to the IED via radio frequency. As shown, regulated power is continuously provided from power block 1202 to microcontroller 1214, which microcontroller 1214 continuously obtains, samples, digitizes, and stores measurements related to current on the power system from measurement CT 1010. The measurements may be stored in a buffer (such as a circular buffer 1262). The microprocessor 1214 may also use the digitized samples to determine the occurrence of a fault. The determination may be made by comparing the current magnitude to a predetermined threshold. The frequency of the signal may be used for the determination. In alternative embodiments, analog flip-flops may be used, such as the high pass filter and window detector described in fig. 12A, 12B, and 13. Upon detection of a fault, the microprocessor 1214 can signal the switch 1204 to close, thereby providing power to the radio frequency transmitter 1220. The microprocessor 1214 may be further configured to output the stored measurements to the transmitter 1220 using, for example, the SPI 1216. Accordingly, digital signals related to the current on the power system may be continuously stored by the line mounted device 1422 and periodically transmitted to the IED for use in determining the location of the fault as described above.

While particular embodiments and applications of the present disclosure have been illustrated and described, it is to be understood that the disclosure is not limited to the precise configuration 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 the disclosure. Accordingly, the scope of the invention should be determined only by the following claims.