Device and method for de-icing of ultra-high voltage ground wires and fiber optic composite overhead ground wires

Abstract

This invention discloses a live-line de-icing device and method for ultra-high voltage (UHV) ground wires and fiber optic composite overhead ground wires. The device includes a high-voltage busbar, a high-voltage circuit breaker, a converter transformer, two converter valves, a protective ball gap, a protective surge arrester, three fast grounding switches, a control and protection device, two de-icing output high-voltage lines, a de-icing switch, and a de-icing short-circuit switch. When a steady-state overvoltage occurs due to electrostatic induction voltage and electromagnetic induction voltage, the fast grounding switch quickly grounds, and the protective ball gap breaks down and discharges. When a transient overvoltage occurs, the surge arrester activates, protecting the de-icing device. This invention achieves overvoltage protection and insulation coordination of the de-icing device under live-line de-icing conditions, ensuring the safe operation of the de-icing device, and effectively realizing reliable de-icing of UHV ground wires and OPGWs under live-line operation.

Description

Technical Field

[0001] This invention belongs to the field of high voltage and insulation technology, and specifically relates to a live de-icing device and method for ultra-high voltage ground wires and fiber optic composite overhead ground wires. Background Technology

[0002] In recent years, some regions have gradually shifted from traditional non-re-icing areas to re-icing areas, leading to an increase in tripping faults of ultra-high voltage and extra-high voltage lines caused by icing. This has seriously affected the safe and stable operation of the power system and severely impacted the normal lives of residents and industrial production.

[0003] When power resources are located far from power load centers, ultra-high voltage (UHV) and extra-high voltage (UHV) transmission have become the inevitable choice for solving long-distance, large-capacity power transmission problems. UHVDC transmission lines have long transmission distances, and in winter, they are prone to conductor and ground wire icing due to rain and snow. Icing can cause ground wire overload, easily leading to discharge and line breakage accidents. For two consecutive years, a ±800kV UHV line experienced ground wire and OPGW line breaks due to icing overload, causing line outages and seriously affecting the safe and stable operation of the UHV line. Currently, line de-icing is carried out using AC or DC de-icing after a power outage, which has advantages such as fast de-icing speed and safety. However, de-icing is generally carried out on conductors, while ground wire de-icing is extremely rare. However, UHV and UHV lines have large transmission capacities and are highly important in the system; de-icing during power outages would cause significant load losses and changes in grid operation, making it difficult to implement in practice. Furthermore, ground wires do not carry current under normal operating conditions, and their icing is more severe than that of conductors, making ground wire de-icing even more necessary in practice.

[0004] However, there are the following problems with DC energized de-icing of ground wires and optical fiber composite overhead ground wires (OPGW) under normal operating conditions of ultra-high voltage lines: (1) The operating DC line generates electrostatic induction voltage on the ground wire and OPGW to be de-iced, which will cause damage to the de-icing device; (2) The AC line that crosses the operating line in parallel will generate electromagnetic induction voltage on the ground wire and OPGW to be de-iced, which will cause damage to the de-icing device; (3) During the de-icing process, a sudden fault occurs in one pole of the DC line, which generates transient overvoltage on the ground wire and OPGW, which will cause damage to the de-icing device. Summary of the Invention

[0005] This invention provides a live de-icing device and method for ultra-high voltage and extra-high voltage ground wires and fiber optic composite overhead ground wires. It can ensure safe and reliable live de-icing of ground wires and OPGWs under line operation conditions, and also ensure the safety and reliability of the de-icing device under live de-icing conditions, avoiding faults such as line breakage and discharge caused by ice accumulation on ultra-high voltage and extra-high voltage lines.

[0006] To achieve the above objectives, the present invention provides a live-line de-icing device for ultra-high voltage ground wires and fiber optic composite overhead ground wires, comprising a high-voltage busbar, a high-voltage circuit breaker, a converter transformer, a first converter valve, a second converter valve, a protective ball gap, a protective surge arrester, a first fast grounding switch, a second fast grounding switch, a third fast grounding switch, a control and protection device, a first de-icing output high-voltage line, a second de-icing output high-voltage line, a de-icing switch, and a de-icing short-circuit switch; one end of the high-voltage circuit breaker is connected to the high-voltage busbar, and the other end is connected to the input end of the converter transformer; the two output ends of the converter transformer are respectively connected to the input ends of the first converter valve and the second converter valve; the output ends of the first converter valve and the second converter valve are respectively connected to one end of the first de-icing output high-voltage line and the second de-icing output high-voltage line; the other ends of the first de-icing output high-voltage line and the second de-icing output high-voltage line are connected separately. The first overhead ground wire and the second overhead ground wire are connected via two de-icing switches. The first overhead ground wire and the second overhead ground wire are connected to the first optical fiber composite overhead ground wire and the second optical fiber composite overhead ground wire via two de-icing short-circuit switches respectively. The first optical fiber composite overhead ground wire and the second optical fiber composite overhead ground wire are connected by a drain wire. Both the first de-icing output high voltage line and the second de-icing output high voltage line are connected to a protective ball gap and a protective surge arrester. The first fast grounding switch is connected to the first de-icing output high voltage line. The second fast grounding switch is connected to the second de-icing output high voltage line. The third fast grounding switch is connected to the neutral point of the first converter valve and the second converter valve. The control and protection device is connected to the control terminals of the high voltage circuit breaker, the first converter valve, the second converter valve, the first fast grounding switch, the second fast grounding switch, and the third fast grounding switch via control cables.

[0007] Furthermore, the high-voltage circuit breaker is a high-voltage vacuum circuit breaker, housed within a gas-filled high-voltage switchgear.

[0008] Furthermore, the converter transformer is a three-phase, three-winding rectifier transformer. The high-voltage side winding of the converter transformer is a delta-connected transformer, and the low-voltage side winding is a Y-connected and delta-connected transformer. The rated voltage is determined by the rated output voltage of the de-icing device and the resistance of the de-icing line.

[0009] Furthermore, both the first and second converter valves are 6-pulse controllable converter valves, and the first and second converter valves are connected in series to form a 12-pulse converter valve; the 12-pulse converter valve is equipped with an interphase surge arrester, a DC current sensor and a DC voltage divider.

[0010] Furthermore, the protective sphere gap includes two spherical electrodes. The protective sphere gap is placed in a sealed container and filled with gas. The diameter of the spherical electrodes is greater than twice the sphere gap distance, and the sphere gap discharge voltage is less than or equal to the DC withstand voltage of the converter device.

[0011] Furthermore, the protection surge arrester is a metal oxide surge arrester, whose continuous operating voltage is greater than the maximum output DC voltage of the de-icing device, whose lightning impulse residual voltage is less than or equal to the lightning impulse withstand voltage of the converter device, and whose maximum current carrying capacity must ensure that the surge arrester is not damaged during the protection operation time under the maximum induced voltage of the line.

[0012] Furthermore, the first and second high-voltage de-icing output lines are overhead lines or cables, and the de-icing switch is a bidirectional switch. When the switch is closed at position ② during de-icing, the de-icing device is connected to the ground wire to be de-iced. When the de-icing switch is closed at position ① during non-de-icing, the de-icing device is disconnected from the ground wire, and the ground wire is grounded.

[0013] Furthermore, the first and second optoelectronic separation junction boxes are used at the beginning and end of the ice melting section to achieve electrical isolation and fiber optic communication between the ice melting section and the non-ice melting section, respectively. A ground wire junction box is used in the middle of the ice melting section to achieve electrical and fiber optic communication.

[0014] The method for de-icing ultra-high voltage ground wires and fiber optic composite overhead ground wires based on the above-mentioned de-icing device includes the following steps:

[0015] Step S1: Based on the parameters of the line to be de-iced, meteorological conditions, and ice thickness, calculate the de-icing voltage, maximum de-icing current, and minimum de-icing current required for the ground wire and OPGW to de-ic.

[0016] Step S2: Select the on / off state of the first fast grounding switch, the second fast grounding switch, and the third fast grounding switch according to the de-icing voltage;

[0017] Step S3: Close the de-icing short-circuit switch and place the de-icing switch at position ② to connect the de-icing device to the ground wire to be de-iced and form a closed circuit;

[0018] Step S4: The control and protection device controls the closing of the high-voltage circuit breaker via the control cable to begin the de-icing of the ground wire and the fiber optic composite overhead ground wire;

[0019] Step S5: Use a tension sensor to monitor the icing weight online and determine whether the online icing weight < 0.1M is true, where M is the initial total icing weight of the overhead ground wire and the fiber optic composite overhead ground wire: if true, proceed to step S7; otherwise, proceed to step S6.

[0020] Step S6: Fix the de-icing current to I, and return to step S5; minimum de-icing current < I < maximum de-icing current;

[0021] Step S7: Disconnect the high-voltage circuit breaker through the control protection device, close the de-icing knife switch to position ①, ground the ground wire to be de-iced, and the de-icing is completed.

[0022] Furthermore, the rated currents of the first, second, and third fast grounding switches are greater than the maximum induced current on the ground wire during a line fault. When the de-icing device needs to output ±5kV rated voltage, the third fast grounding switch is in the closed position, and the first and second fast grounding switches are in the open position. When the de-icing device needs to output 10kV rated voltage, the second fast grounding switch is in the closed position, and the first and third fast grounding switches are in the open position. When the de-icing device needs to output -10kV rated voltage, the first fast grounding switch is in the closed position, and the second and third fast grounding switches are in the open position.

[0023] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0024] This invention discloses a live-line de-icing device for ultra-high voltage (UHV) ground wires and fiber optic composite overhead ground wires. It employs protective ball gaps, surge arresters, and fast grounding switches to protect the line. When a steady-state overvoltage occurs due to electrostatic induction voltage and electromagnetic induction voltage, the fast grounding switch quickly grounds the line, causing the protective ball gap to break down and discharge. When a transient overvoltage occurs, the surge arrester activates, protecting the de-icing device. This achieves overvoltage protection and insulation coordination for the de-icing device under live-line de-icing conditions, ensuring the safe operation of the device and effectively enabling reliable de-icing of UHV ground wires and OPGWs under live-line operation.

[0025] Furthermore, both converter valves are 6-pulse controllable converter valves, and the two stages are connected in series to form a 12-pulse converter valve; the 12-pulse converter valve is equipped with a phase-to-phase surge arrester, a DC current sensor and a DC voltage divider to realize phase-to-phase overvoltage protection, overcurrent protection and overvoltage protection of the converter valve.

[0026] Furthermore, the protective ball gap is placed in a sealed container and inflated to protect the DC side equipment from damage under steady-state overvoltage, and to ensure that the de-icing equipment is not damaged under electrostatic induction voltage of the operating DC line and electromagnetic induction voltage of the parallel AC line.

[0027] The de-icing method described in this invention first calculates the de-icing voltage and current based on actual conditions. Then, based on the de-icing voltage, it determines the on / off state of the fast grounding switch and applies an appropriate current to de-ic the line until the ice weight is less than a set value, thus completing the de-icing process. Multiple voltage outputs can be achieved through the fast grounding switch, providing a suitable voltage to the affected line and improving the overall flexibility of the de-icing method. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of an ultra-high voltage ground wire and an OPGW energized de-icing device according to an embodiment of the present invention;

[0029] 1—High-voltage busbar, 2—High-voltage circuit breaker, 3—Converter transformer, 4-1—First converter valve, 4-2—Second converter valve, 5-1—First protective ball gap, 5-2—Second protective ball gap, 6-1—First protective surge arrester, 6-2—Second protective surge arrester, 7-1—First fast grounding switch, 7-2—Second fast grounding switch, 7-3—Third fast grounding switch, 8—Control and protection device, 9-1—First de-icing output high-voltage line, 9-2—Second de-icing output High-voltage line, 10-1—First de-icing switch, 10-2—Second de-icing switch, 11-1—First overhead ground wire, 11-2—Second overhead ground wire, 12-1—First de-icing short-circuit switch, 12-2—Second de-icing short-circuit switch, 13-1—First fiber optic composite overhead ground wire, 13-2—Second fiber optic composite overhead ground wire, 13-3—Drain wire, 14-2—Ground wire junction box, 14-1—First optoelectronic separation junction box, 14-3—Second optoelectronic separation junction box.

[0030] Figure 2 This is a schematic diagram of a live de-icing method for an ultra-high voltage ground wire and OPGW according to an embodiment of the present invention. Figure 2 Explanation of the markings in the text:

[0031] S1—Calculates the voltage and current required for de-icing based on line parameters, meteorological conditions, and ice thickness;

[0032] S2—Selects the on / off state of the fast grounding switch;

[0033] S3—Close the de-icing short-circuit switch and the de-icing switch;

[0034] S4—Close the high-voltage circuit breaker and begin de-icing;

[0035] S5—Set the initial total icing weight of the ground wire to M, and determine whether the online icing weight is less than 0.1M;

[0036] S6—Fixed ice-melting current is I;

[0037] S7—High-voltage circuit breaker with tripping function; de-icing switch grounded; de-icing complete. Detailed Implementation

[0038] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0039] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] To better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] like Figure 1 As shown, the present invention discloses a live de-icing device for ultra-high voltage ground wire and fiber optic composite overhead ground wire, comprising a high voltage busbar 1, a high voltage circuit breaker 2, a converter transformer 3, a first converter valve 4-1 and a second converter valve 4-2, a first protective ball gap 5-1, a second protective ball gap 5-2, a first protective surge arrester 6-1, a second protective surge arrester 6-2, a first fast grounding switch 7-1, a second fast grounding switch 7-2, a third fast grounding switch 7-3, a control and protection device 8, a first de-icing output high voltage line 9-1, a second de-icing output high voltage line 9-2, a first de-icing switch 10-1, a second de-icing switch 10-2, a first de-icing short-circuit switch 12-1, and a second de-icing short-circuit switch 12-2.

[0042] High-voltage busbar 1 is generally led out from the 35kV overhead line T-connection or from the 35kV side busbar of the substation, and its leading capacity should meet the rated output capacity requirements of the de-icing device. One end of the high-voltage circuit breaker 2 is connected to high-voltage busbar 1, and the other end is connected to the input end of converter transformer 3. The two output ends of converter transformer 3 are respectively connected to the input ends of the first converter valve 4-1 and the second converter valve 4-2. The output end of the first converter valve 4-1 is connected to one end of the first de-icing output high-voltage line 9-1, and the output end of the second converter valve 4-2 is connected to one end of the second de-icing output high-voltage line 9-2. The other end of the first de-icing output high-voltage line 9-1 is connected to the first overhead ground wire 11 through the first de-icing switch 10-1. -1 is connected, and the other end of the second de-icing output high-voltage line 9-2 is connected to the second overhead ground line 11-2 through the second de-icing switch 10-2. The first overhead ground line 11-1 is connected to the first optical fiber composite overhead ground line 13-1 through the first de-icing short-circuit switch 12-1. The second overhead ground line 11-2 is connected to the second optical fiber composite overhead ground line 13-2 through the second de-icing short-circuit switch 12-2. The first optical fiber composite overhead ground line 13-1 and the second optical fiber composite overhead ground line 13-2 are connected by a drain line 13-3. The first protective ball gap 5-1, the first protective surge arrester 6-1, and the first fast grounding switch 7-1 are connected to the first de-icing output high-voltage line 9-1. The second protective ball gap 5-2, the second protective surge arrester 6-2, and the second fast grounding switch 7-2 are connected to the second de-icing output high-voltage line 9-2. One end of the third fast grounding switch 7-3 is connected to the neutral point of the first converter valve 4-1 and the second converter valve 4-2, and the other end is grounded. The control and protection device 8 is connected to the control terminals of the high-voltage circuit breaker 2, the first converter valve 4-1, the second converter valve 4-2, the first fast grounding switch 7-1, the second fast grounding switch 7-2, and the third fast grounding switch 7-3 via control cables.

[0043] High-voltage circuit breaker 2 is a 40.5kV high-voltage vacuum circuit breaker, which is placed in a gas-filled high-voltage switchgear to enable the safe connection of the high-voltage bus voltage to the input terminal of converter transformer 3.

[0044] The converter transformer 3 is a three-phase, three-winding rectifier transformer. Its high-voltage side winding is a delta-connected transformer with a rated voltage of 35kV, and its low-voltage side winding is a Y-connected and delta-connected transformer. Its rated voltage is determined by the rated output voltage of the de-icing device (either the first de-icing output high-voltage line 9-1 or the second de-icing output high-voltage line 9-2) and the resistance of the de-icing line, ensuring that the voltage delivered to the first overhead ground line 11-1 and the second overhead ground line 11-2 reaches the de-icing voltage. In this embodiment, the rated output voltage of the de-icing device is 10kV, and the rated output current is 1kA. The calculated rated voltage of the low-voltage side of the converter transformer is 4.14kV.

[0045] Both the first converter valve 4-1 and the second converter valve 4-2 are 6-pulse controllable converter valves. The first converter valve 4-1 outputs a positive voltage when connected in the forward direction, and the second converter valve 4-2 outputs a negative voltage when connected in the reverse direction. The two stages of the first converter valve 4-1 and the second converter valve 4-2 are connected in series to form a 12-pulse converter valve. The 12-pulse converter valve is equipped with auxiliary devices such as phase-to-phase surge arresters, DC current sensors, and DC voltage dividers to realize phase-to-phase overvoltage protection, overcurrent protection, and overvoltage protection of the converter valve. The 12-pulse converter valve and the auxiliary devices constitute a converter device.

[0046] Among them, the phase-to-phase surge arrester provides phase-to-phase overvoltage protection for the converter valve, the DC current sensor provides overcurrent protection for the converter valve, and the DC voltage divider provides overvoltage protection for the converter valve.

[0047] The first protective ball gap 5-1, the second protective ball gap 5-2, the first protective surge arrester 6-1, the second protective surge arrester 6-2, the first fast grounding switch 7-1, the second fast grounding switch 7-2, the third fast grounding switch 7-3, and the control and protection device 8 are all used to realize overvoltage protection for the converter device. The first protective ball gap 5-1 and the second protective ball gap 5-2 are placed in a sealed container and filled with gas to protect the DC side equipment from damage under steady-state overvoltage, especially to ensure that the de-icing equipment is not damaged under the electrostatic induction voltage of the operating DC line and the electromagnetic induction voltage of the parallel AC line. Specifically, the protective sphere gap includes two spherical electrodes with a diameter greater than twice the sphere gap distance to ensure a slightly non-uniform electric field in the discharge gap and reduce discharge dispersion. The discharge voltage of the protective sphere gap is less than or equal to the DC withstand voltage of the converter device to ensure that the sphere gap breaks down and discharges first under electrostatic induction voltage and electromagnetic induction voltage. The protective sphere gap is filled with SF6, N2, or air, and the gas gap distance is determined by the gas type and gas pressure. In this embodiment, the sphere gap breakdown voltage can be selected as 15kV, which is less than or equal to the insulation level of the de-icing device.

[0048] Both the first protective surge arrester 6-1 and the second protective surge arrester 6-2 are metal oxide surge arresters. Their continuous operating voltage is greater than the maximum output DC voltage of the de-icing device, their lightning impulse residual voltage is less than or equal to the lightning impulse withstand voltage of the converter device, and their maximum current capacity must ensure that the surge arrester is not damaged during the protection operation time under the maximum induced voltage of the line. This ensures that during the de-icing process, if a sudden fault occurs on one pole of the DC line and a transient overvoltage is generated on the ground wire and OPGW, the surge arrester will not be damaged. In this embodiment, the metal oxide surge arrester can be a power station type composite-jacketed zinc oxide gapless surge arrester with a rated voltage of 14kV, a lightning impulse residual voltage of 25kV, and a rated current capacity of 100kJ.

[0049] The grounding status of the first fast grounding switch 7-1, the second fast grounding switch 7-2, and the third fast grounding switch 7-3 is determined by the output voltage type of the de-icing device. Their rated current should be greater than the maximum induced current on the ground wire during a line fault. When the de-icing device needs to output ±5kV rated voltage, the third fast grounding switch 7-3 is in the closed position, and the first fast grounding switch 7-1 and the second fast grounding switch 7-2 are in the open position. When the de-icing device needs to output 10kV rated voltage, the second fast grounding switch 7-2 is in the closed position, and the first fast grounding switch 7-1 and the third fast grounding switch 7-3 are in the open position. When the de-icing device needs to output -10kV rated voltage, the first fast grounding switch 7-1 is in the closed position, and the second fast grounding switch 7-2 and the third fast grounding switch 7-3 are in the open position. The control and protection device 8 is used to control the rapid switching of the high-voltage circuit breaker 2, the first converter valve 4-1 and the second converter valve 4-2, the first fast grounding switch 7-1, the second fast grounding switch 7-2 and the third fast grounding switch 7-3 when an overvoltage occurs. Specifically, it controls the high-voltage circuit breaker 2 to open and controls the first fast grounding switch 7-1, the second fast grounding switch 7-2 and the third fast grounding switch 7-3 to quickly ground, so as to ensure that the de-icing device is not damaged by overvoltage.

[0050] The first high-voltage output line 9-1 and the second high-voltage output line 9-2 can be 10kV overhead lines or 10kV cables, and are respectively connected to the first overhead ground line 11-1 and the second overhead ground line 11-2 through the first de-icing switch 10-1 and the second de-icing switch 10-2. The first de-icing switch 10-1 and the second de-icing switch 10-2 are bidirectional switches. When de-icing, the switches are closed at position ②, connecting the de-icing device to the ground line to be de-iced. When not de-icing, the switches are closed at position ③. At point ①, disconnect the de-icing device from the ground wire and ground the ground wire. The two ends of the overhead ground wire are connected to the first optical fiber composite overhead ground wire 13-1 and the second optical fiber composite overhead ground wire 13-2 via the first de-icing short-circuit switch 12-1 and the second de-icing short-circuit switch 12-2, respectively. The two ends of the drain wire 13-3 are connected to the first optical fiber composite overhead ground wire 13-1 and the second optical fiber composite overhead ground wire 13-2, respectively, forming a closed loop for OPGW de-icing of the ultra-high voltage ground wire. The first overhead ground wire 11-1 and the second overhead ground wire 11-2 are electrically insulated from the line tower via supporting insulators. During de-icing, both the first de-icing short-circuit switch 12-1 and the second de-icing short-circuit switch 12-2 are in the closed position.

[0051] The first and second optoelectronic separation junction boxes 14-1 and 14-3 are used at the beginning and end of the ice melting section to achieve electrical isolation and fiber optic communication between the ice melting section and the non-ice melting section. The ground wire junction box 14-2 is used in the middle of the ice melting section to achieve electrical and fiber optic communication between the ice melting section and the non-ice melting section.

[0052] Reference Figure 2 A method for de-icing energized ultra-high voltage ground wires and fiber optic composite overhead ground wires includes the following steps:

[0053] Step S1: Based on the parameters of the line to be de-iced, meteorological conditions, and ice thickness, calculate the de-icing voltage and current required for de-icing the overhead ground wire and OPGW. In this step, the actual de-icing current of the conductor should be selected between the minimum and maximum de-icing current, taking into account the de-icing time. If the de-icing current is less than the minimum de-icing current, the de-icing will be ineffective; if the de-icing current is greater than the maximum de-icing current, it will cause permanent deformation of the conductor, resulting in increased sag or damage to the conductor's mechanical strength.

[0054] Step S2: Based on the de-icing voltage, select the on / off state of the first fast grounding switch 7-1, the second fast grounding switch 7-2, and the third fast grounding switch 7-3. In this step, generally one of the grounding switches 7-1 or the second fast grounding switch 7-2 is selected for grounding.

[0055] When the de-icing device needs to output ±5kV rated voltage at both ends, the third fast grounding switch 7-3 is in the closed position, and the first fast grounding switch 7-1, fast grounding switch 7-2 are in the open position. When the de-icing device needs to output 10kV rated voltage, the second fast grounding switch 7-2 is in the closed position, and the first fast grounding switch 7-1 and the third fast grounding switch 7-3 are in the open position. When the de-icing device needs to output -10kV rated voltage, the first fast grounding switch 7-1 is in the closed position, and the second fast grounding switch 7-2 and the third fast grounding switch 7-3 are in the open position.

[0056] Step S3: Close the first de-icing short-circuit switch 12-1 and the second de-icing short-circuit switch 12-2, close the first de-icing switch 10-1 and the second de-icing switch 10-2 at position ②, connect the de-icing device to the ground wire to be de-iced and form a closed circuit.

[0057] Step S4: The control and protection device 8 closes the high-voltage circuit breaker 2 via the control cable to begin de-icing the ground wire and OPGW. In this step, after de-icing begins, the DC output current is adjusted to between the maximum and minimum de-icing current by adjusting the trigger conduction angle of the converter valve.

[0058] Step S5: Set the initial total icing weight of the overhead ground wire and the fiber optic composite overhead ground wire to M. During the de-icing process, a tension sensor is used to monitor the icing weight online. During the de-icing process, the control and protection device determines whether the online icing weight of the overhead ground wire and the fiber optic composite overhead ground wire meets the requirement of <0.1M. If it meets the requirement, proceed to step S7; otherwise, proceed to step S6. In this step, the change in icing weight is monitored by the tension sensor. When the icing weight is less than 10% of the initial total icing weight M, the de-icing work is considered complete.

[0059] Step S6: By controlling the protection device 8 to fix the converter valve trigger conduction angle and fix the de-icing current to I, return to step S5.

[0060] Step S7: Disconnect the high-voltage circuit breaker 2 via the control and protection device 8, and connect the first de-icing switch 10-1 and the second de-icing switch 10-2 to position ①, that is, ground the first overhead ground wire 11-1 and the second overhead ground wire 11-2, thus ending the de-icing process. In this step, after the de-icing is completed, disconnect the high-voltage circuit breaker 2 and the de-icing switch to electrically isolate the de-icing device from the power supply and the lines.

[0061] The above description is merely a specific embodiment of the present invention, but the scope of application of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of application of the present invention. Therefore, the scope of application of the present invention should be determined by the scope of protection of the claims.

Claims

1. A live de-icing device for ultra-high voltage ground wires and fiber optic composite overhead ground wires, characterized in that, It includes a high-voltage busbar (1), a high-voltage circuit breaker (2), a converter transformer (3), a first converter valve (4-1), a second converter valve (4-2), a protective ball gap, a protective surge arrester, a first fast grounding switch (7-1), a second fast grounding switch (7-2), a third fast grounding switch (7-3), a control and protection device (8), a first de-icing output high-voltage line (9-1), a second de-icing output high-voltage line (9-2), a de-icing switch, and a de-icing short-circuit switch; One end of the high-voltage circuit breaker (2) is connected to the high-voltage busbar (1), and the other end is connected to the input end of the converter transformer (3). The two output ends of the converter transformer (3) are respectively connected to the input ends of the first converter valve (4-1) and the second converter valve (4-2). The output ends of the first converter valve (4-1) and the second converter valve (4-2) are respectively connected to one end of the first de-icing output high-voltage line (9-1) and the second de-icing output high-voltage line (9-2). The other end of the high-voltage line (9-2) is connected to the first overhead ground line (11-1) and the second overhead ground line (11-2) through two de-icing switches. The first overhead ground line (11-1) and the second overhead ground line (11-2) are connected to the first optical fiber composite overhead ground line (13-1) and the second optical fiber composite overhead ground line (13-2) through two de-icing short-circuit switches. The first optical fiber composite overhead ground line (13-1) and the second optical fiber composite overhead ground line (13-2) are connected by a drain line (13-3). Protective ball gaps and surge arresters are connected to both the first de-icing output high-voltage line (9-1) and the second de-icing output high-voltage line (9-2); the first fast grounding switch (7-1) is connected to the first de-icing output high-voltage line (9-1); the second fast grounding switch (7-2) is connected to the second de-icing output high-voltage line (9-2); the third fast grounding switch (7-3) is connected to the neutral point of the first converter valve (4-1) and the second converter valve (4-2); The control and protection device (8) is connected to the control terminals of the high-voltage circuit breaker (2), the first converter valve (4-1), the second converter valve (4-2), the first fast grounding switch (7-1), the second fast grounding switch (7-2), and the third fast grounding switch (7-3) via control cables.

2. The energized de-icing device for an ultra-high voltage ground wire and fiber optic composite overhead ground wire according to claim 1, characterized in that: The high-voltage circuit breaker (2) is a high-voltage vacuum circuit breaker, which is placed inside an inflatable high-voltage switch cabinet.

3. The energized de-icing device for ultra-high voltage ground wires and fiber optic composite overhead ground wires according to claim 1, characterized in that: The converter transformer (3) is a three-phase three-winding rectifier transformer. The high-voltage side winding of the converter transformer (3) is a Δ-connected transformer, and the low-voltage side winding is a Y-connected and Δ-connected transformer. The rated voltage is determined by the rated output voltage of the ice-melting device and the resistance of the ice-melting line.

4. The energized de-icing device for an ultra-high voltage ground wire and fiber optic composite overhead ground wire according to claim 1, characterized in that: The first converter valve (4-1) and the second converter valve (4-2) are both 6-pulse controllable converter valves. The first converter valve (4-1) and the second converter valve (4-2) are connected in series to form a 12-pulse converter valve. The 12-pulse converter valve is equipped with a phase-to-phase surge arrester, a DC current sensor and a DC voltage divider.

5. The energized de-icing device for an ultra-high voltage ground wire and fiber optic composite overhead ground wire according to claim 1, characterized in that: The protective spherical gap includes two spherical electrodes. The protective spherical gap is placed in a sealed container and inflated. The diameter of the spherical electrodes is greater than twice the spherical gap distance. The spherical gap discharge voltage is less than or equal to the DC withstand voltage of the converter device.

6. The energized de-icing device for an ultra-high voltage ground wire and fiber optic composite overhead ground wire according to claim 5, characterized in that: The protective surge arrester is a metal oxide surge arrester, whose continuous operating voltage is greater than the maximum output DC voltage of the de-icing device, whose lightning impulse residual voltage is less than or equal to the lightning impulse withstand voltage of the converter device, and whose maximum current carrying capacity must ensure that the surge arrester is not damaged during the protection operation time under the maximum induced voltage of the line.

7. The energized de-icing device for an ultra-high voltage ground wire and fiber optic composite overhead ground wire according to claim 1, characterized in that: The first high-voltage output line (9-1) and the second high-voltage output line (9-2) for de-icing are overhead lines or cables. The de-icing switch is a bidirectional switch. When the switch is closed at position ② during de-icing, the de-icing device is connected to the ground wire to be de-iced. When the de-icing switch is closed at position ① during non-de-icing, the de-icing device is disconnected from the ground wire and the ground wire is grounded.

8. The energized de-icing device for an ultra-high voltage ground wire and fiber optic composite overhead ground wire according to claim 1, characterized in that: The first and second photoelectric separation junction boxes (14-1 and 14-3) at the beginning and end of the ice melting section are respectively used to achieve electrical isolation and fiber optic communication between the ice melting section and the non-ice melting section. The ground wire junction box (14-2) in the middle of the ice melting section is used to achieve electrical and fiber optic communication.

9. A live-line de-icing method based on the live-line de-icing device for ultra-high voltage ground wires and fiber optic composite overhead ground wires as described in claim 1, characterized in that, Includes the following steps: Step S1: Based on the parameters of the line to be de-iced, meteorological conditions, and ice thickness, calculate the de-icing voltage, maximum de-icing current, and minimum de-icing current required for the ground wire and OPGW to de-ic. Step S2: Select the on / off state of the first fast grounding switch (7-1), the second fast grounding switch (7-2), and the third fast grounding switch (7-3) according to the de-icing voltage; Step S3: Close the de-icing short-circuit switch and place the de-icing switch at position ② to connect the de-icing device to the ground wire to be de-iced and form a closed circuit; Step S4: The control and protection device (8) controls the closing of the high-voltage circuit breaker (2) through the control cable to start the de-icing of the ground wire and the fiber optic composite overhead ground wire; Step S5: Use a tension sensor to monitor the icing weight online and determine whether the online icing weight < 0.1M is true, where M is the initial total icing weight of the overhead ground wire and the fiber optic composite overhead ground wire: if true, proceed to step S7; otherwise, proceed to step S6. Step S6: Fix the de-icing current to I, and return to step S5; minimum de-icing current < I < maximum de-icing current; Step S7: Disconnect the high-voltage circuit breaker (2) by controlling the protection device (8), close the de-icing knife switch at position ①, and ground the ground wire to be de-iced, thus ending the de-icing process.

10. The electrified de-icing method according to claim 9, characterized in that, The rated currents of the first fast grounding switch (7-1), the second fast grounding switch (7-2), and the third fast grounding switch (7-3) are greater than the maximum induced current in the ground wire during a line fault. When the de-icing device needs to output ±5kV rated voltage at both ends, the third fast grounding switch (7-3) is in the closed position, and the first fast grounding switch (7-1) and the second fast grounding switch (7-2) are in the open position. When the de-icing device needs to output 10kV rated voltage, the second fast grounding switch (7-2) is in the closed position, and the first fast grounding switch (7-1) and the third fast grounding switch (7-3) are in the open position. When the de-icing device needs to output -10kV rated voltage, the first fast grounding switch (7-1) is in the closed position, and the second fast grounding switch (7-2) and the third fast grounding switch (7-3) are in the open position.

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