The present disclosure relates generally to a system and method for detecting degradation in branching underground electrical cables.
The increasing practice of underground residential distributed (URD) cables being installed in power systems requires utility companies to know the health of these cables. Since the health of URD cables cannot be determined by visual methods like overhead lines, a better understanding of the power cable and its aging process is needed. Insulation of medium voltage URD power cables age due to a phenomenon called water treeing. Water trees are important to utility companies, because water trees cannot be detected using traditional protection methods. Also, water trees are the main reason for URD cable failures, yet water trees can grow in cables without any effect on the voltage or currents. For example, water trees can grow across the insulation and still not cause the cable to fault. Also, water trees do not produce partial discharges, which are a common cable diagnostic tool. Accordingly, detecting water trees becomes very difficult and expensive.
Aspects and advantages of the present disclosure will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the present disclosure.
In one aspect, the present disclosure relates to a system for detecting water trees in branching underground electrical cables. The system includes a pulse generator configured to inject a pulse into a first underground cable that branches into a second underground cable and a third underground cable. The system includes a first sensor, a second sensor, and a third sensor. The first sensor is associated with the first underground cable. The second sensor is associated with the second underground cable. The third sensor is associated with the third underground cable. The system includes a control device configured to perform operations. The operations include obtaining a first, second, and third signal associated with the first, second and third sensors, respectively. The operations include determining a lead-lag relationship between the second signal and the third signal. The operations include determining presence of a water tree within at least one of the second underground cable and the third underground cable based on the lead-lag relationship. When the control device determines presence of a water tree, the control device generates one or more control actions associated with repairing or replacing at least one of the second underground cable and the third underground cable.
In another aspect, the present disclosure relates to a method for detecting water trees in branching underground electrical cables comprising a first underground cable that branches into a second underground cable and a third underground cable. The method includes injecting, by a pulse generator, a pulse into the first underground cable. The method includes obtaining, by one or more control devices, a first signal associated with a first sensor configured to detect signals traveling along the first underground cable. The method includes obtaining, by the control device(s), a second signal associated with a second sensor configured to detect signals traveling along the second underground cable. The method includes obtaining, by the control device(s), a third signal associated with a third sensor configured to detect signals traveling along the third underground cable. The method includes determining, by the control device(s), a lead-lag relationship between the second signal and the third signal. The method includes determining, by the control device(s), presence of a water tree within at least one of the second underground cable and the third underground cable based on the lead-lag relationship. When presence of a water tree is detected, the method includes generating, by the control device(s), one or more control actions associated with repairing or replacing at least one of the second underground cable and the third underground cable.
In yet another aspect, the present disclosure relates to a sensor for a system for detecting water trees in branching underground electrical cables. The sensor includes a circuit board comprising a first side and a second side. The sensor includes a filter circuit disposed on the circuit board. The filter circuit can be configured to filter alternating current associated with an underground cable of the branching underground cables. The sensor includes a spring coupled to the first side of the circuit board. The spring can be configured to electrically couple the circuit board to the underground cable. The sensor includes one or more circuit components coupled to the second side of the circuit board.
These and other features, aspects and advantages of the present disclosure will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the present disclosure.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Time Domain Reflectometry (TDR) is a traveling wave based method that can be used to determine whether water trees are present within an underground cable. TDR can be performed off-line or on-line. When a traveling wave is sent down an underground cable, a reflection of the wave will be generated when the wave reaches the end of the underground cable or an element (e.g., water tree) having a different impedance compared to the impedance of the cable. This reflection can be used to locate water trees in an underground cable, because the section of the underground cable with the water tree will change the impedance in that section. An early reflection is indicative of water trees in the underground cable.
Traveling wave theory indicates that an injected electrical pulse will travel through a medium at a specific speed until the pulse reaches a mismatch in properties at which a reflection will occur. Conventional systems inject a pulse into a network and record a reference response. Any deviation from the reference response indicates a change in network health. However, due to the topology of the network, determining the location of the change in network health is very difficult.
In one example embodiment, the present disclosure uses signals from branching underground cables as reference signals relative to each other to isolate changes in insulation health. Utilizing a leading or lagging reflection pulse, the change in insulation health can be pinpointed to a specific underground cable. The leading or lagging reflection is utilized because of the configuration with which the cables are connected to a bus. When a reflection pulse returns to the beginning of a cable, it is transmitted into all of the cables connected at that bus. A time delay occurs between when the reflection is measured in the corresponding cable and in other cables connected at the bus. Therefore, when looking at all the measured signals at a single bus, the cable's signal with a measurement reflection which leads the others indicates the underground cable which created the reflection. The signals which are lagging are understood to not be related to the underground cable of interest.
Referring now to the FIGS.,
The conductor 110 can be comprised of any suitable conductive material. For instance, the conductor 110 can be comprised of copper. The insulation 120 can be comprised of any suitable insulating material. For instance, the insulation 120 can be comprised of cross-linked polyethylene insulation (XLPE). The ground sheath 130 can be comprised of any suitable conductive material. For instance, the ground sheath 130 can be comprised of copper.
Referring now to
In example embodiments, a pulse P injected into the first end 512 of the first underground cable 510 can travel along the first underground cable 510 and into both the second and third underground cables 520, 530. A reflected pulse in second underground cable 520 can then travel into the first and third underground cables 510, 530. Likewise, a reflected pulse in the third underground cable 530 can travel into the first and second underground cables 510, 520.
Referring briefly now to
In example embodiments, the first, second and third underground cables 610, 620, 630 can each be coupled to a busbar 640. For instance, the second end 614 of the first underground cable 610 can be coupled to the busbar 640, and the first end 622, 632 of both the second and third underground cables 620, 630 can be coupled to the busbar 640. In this manner, a pulse P injected into the first end 612 of the first underground cable 610 can travel along the first underground cable 610 and into both the second and third underground cables 620, 630. A reflected pulse in the second underground cable 620 can travel into the first and third underground cables 610, 610. Likewise, a reflected pulse in the third underground cable 630 can travel into the first and second underground cables 610, 620. As will be discussed below in more detail, the present disclosure provides a system and method for detecting water trees in branching underground cables, such as those depicted in
The system 700 can include one or more control devices 740. In general, the control device(s) 740 can correspond to any suitable processor-based device, including one or more computing devices. For example, the control device(s) 740 may include one or more processors 742 and one or more associated memory devices 744 configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations, and the like disclosed herein). As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit (ASIC), a Field Programmable Gate Array (FPGA), and other programmable circuits. Additionally, the memory device(s) 744 may generally include memory element(s) including, but not limited to, a computer readable medium (e.g., random access memory (RAM)), a computer readable non-volatile medium (e.g., flash memory), a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD), and/or other suitable memory elements or combinations thereof. The memory device(s) 744 may store instructions that, when executed by the processor 742, cause the processor 742 to perform various operations.
The control device(s) 740 can be communicatively coupled to the sensors 710, 720, 730 via any suitable wired or wireless connection 750. In this manner, the control device(s) 740 can receive the signals detected by the sensors 710, 720, 730. As will be discussed below in more detail, the control device(s) 740 can process the signals to determine a location of a water tree in the branching underground cables 500, 600. More specifically, the control device(s) 740 can determine whether a water tree is present within the second underground cable 520, 620, the third underground cable 530, 630, or both.
During the first period of time 840, the pulse P (
During the second period of time 850, the second signal 820 and the third signal 830 each comprise a first reflected pulse. As shown, the first reflected pulse of the second signal 820 leads the first reflected pulse of the third signal 830. Furthermore, since the second signal 820 leads the third signal 830 during the second period of time 850, the one or more control device(s) 740 can determine the first reflected pulse originated in the second underground cable 520, 620 and subsequently traveled into the third underground cable 530, 630. In example embodiments, the first reflected pulse can indicate the presence of a water tree within the second underground cable 520, 630. More specifically, the control device(s) 740 can determine the first reflected pulse is indicative of a water tree in the second underground cable 520, 620. In example embodiments, the water tree can be similar to the water tree 140 depicted in
During the third period of time 860, the second signal 820 and the third signal 830 each comprise a second reflected pulse. As shown, the second reflected pulse of the second signal 820 leads the second reflected pulse of the third signal 830. Furthermore, since the second signal 820 continues to lead the third signal 830 during the third period of time 860, the one or more control device(s) 740 can determine the second reflected pulse originated in the second underground cable 520, 620 and subsequently traveled into the third underground cable 530, 630. In example embodiments, the second reflected pulse can indicate the pulse P reaching the second end 624 of the second underground cable 620, returning to the first end 622 of the second underground cable 620, and subsequently entering the third underground cable 630.
The control device(s) 740 can be configured to determine a location of the water tree within the second underground cable 520, 620. For instance, the control device(s) 740 can determine the location of the water tree based, at least in part, on a time delay between the first and second reflected pulses of the second signal 820. Furthermore, once the control device(s) 740 determine the location of the water tree, the control device(s) 740 can generate one or more control actions associated with repairing or replacing the second underground cable 520, 620. For instance, the control device(s) 740 can provide one or more notifications (e.g., email, text-message, etc.) to authorized personnel. In this manner, the notifications can apprise authorized personnel of the water trees and allow them to take appropriate action (e.g., repair or replace the underground cable with the water tree).
During the fourth period of time 870, the second signal 820 and the third signal 830 each comprise a third reflected pulse. As shown, the third reflected pulse of the third signal 830 leads the third reflected pulse of the second signal 820. Since the third signal 830 leads the second signal 820 during the fourth period of time 870, the one or more control device(s) 740 can determine the third reflected pulse originated in the third underground cable 530, 630. In example embodiments, the third reflected pulse can indicate the pulse P reaching the second end 634 of the third underground cable 630, returning to the first end 632 of the third underground cable 630, and subsequently entering the second underground cable 620.
Although the graph 800 depicted in
The sensor 900 can include a filter circuit 930. The filter circuit 930 can filter alternating current power traveling along the underground cables. More specifically, the filter circuit 930 can filter the alternating current power from the signals traveling along the underground cables. In this manner, the sensing circuit can be isolated from the alternating current power.
In example embodiments, the sensor 900 can include a switch 940 movable between a first position and a second position. When the switch is in the first position, the sensor 900 can be configured to transmit the pulse via the pulse generator 910. When the switch 940 is in the second position, the switch can be configured to receive a pulse that has already been injected into one of the cables. In this manner, the sensor 900 can transmit pulses or receive reflected pulses.
Referring now to
At (1202), the method 1200 comprises injecting a pulse into the first underground cable. In example embodiments, a frequency of the pulse can be different than a frequency associated with alternating current power that is present on the first underground cable. More specifically, the frequency of the pulse can be greater than the frequency associated with the alternating current power.
At (1204), the method 1200 comprises obtaining, by the processor(s), a first signal associated with a first sensor configured to detect signals traveling along the first underground cable.
At (1206), the method 1200 comprises obtaining, by the processor(s), a second signal associated with a second signal configured to detect signals traveling along the second underground cable.
At (1208), the method 1200 comprises obtaining, by the processor(s), a third signal associated with a third sensor configured to detect signals traveling along the third underground cable.
At (1210), the method 1200 comprises determining, by the processor(s), a lead-lag relationship between the second signal and the third signal. In example embodiments, the processor(s) can compare the second and third signals against one another during discrete periods of time. For instance, the processor(s) can compare the second and third signals during a period of time in which both the second and third signal comprise a reflected pulse. If the reflected pulse of the second signal occurs before the reflected pulse of the third signal, the processor(s) can determine the second signal leads the third signal. Additionally, the processor(s) can determine the reflected pulse originated in the second underground cable and subsequently traveled into the third underground cable.
At (1212), the method 1200 comprises determining, by the processor(s), presence of a water tree within at least one of the second underground cable and the third underground cable based on the lead-lag relationship. As an example, if the second signal leads the third signal and both comprise a reflected pulse indicative of a water tree, the water tree resides in the second underground cable. More specifically, the reflected pulse can be inverted relative to the pulse injected into the first underground cable, because the impedance of the water tree is different than the impedance of the underground cables.
At (1214), the method 1200 comprises generating, by the processor(s), one or more control actions associated with repairing or replacing at least one of the second underground cable and the third underground cable. In example embodiments, the one or more control actions can comprise generating a notification (e.g., short message service (SMS) text, electronic mail, etc.) to a remote device, such as a control station at a powerplant. In this manner, the notification can inform appropriate parties of the detected water tree and allow them to take appropriate action.
This written description uses examples to disclose the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
The present application claims the benefit of priority of U.S. Provisional Patent Application No. 62/467,278, entitled “LEADING/LAGGING CABLE REFERENCING PLATFORM FOR MONITORING THE HEALTH OF UNDERGROUND CABLE NETWORKS,” filed Mar. 6, 2017, which is incorporated herein by reference.
This invention was made with Government support under Contract No. DE-AC09-085R22470, awarded by the U.S. Department of Energy. The Government has certain rights in the invention.
Number | Date | Country | |
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62467278 | Mar 2017 | US |