Smart Grid Substation OPGW Down Cable Safety Operation and Inspection Grounding System

Abstract

The OPGW down-lead cable safety operation and inspection grounding system of the smart grid substation of the present application, after the OPGW down-lead cable enters the substation, first passes through the lightning arrester, and realizes the three-point connection and grounding of the OPGW terminal reserved cable, OPGW reserved safety cable fork plate and junction box by means of a grounding knife switch, which completely solves the problem that the OPGW down-lead cable is inconvenient to measure the resistance of the substation grounding network, and completely solves the problem of personal safety threat caused by the OPGW down-lead cable detecting the resistance of the substation grounding network; the OPGW down-lead cable fork plate is designed and improved, and the material, structure and size are designed respectively, and the method of hanging the safety cable fork plate is reserved, and the OPGW terminal reserved cable plugging design is improved; TS-704 silicone rubber is used to replace the fireproof mud plugging sleeve to solve the problem of the fireproof mud plugging falling off of the OPGW down-lead cable; finally, the improved pin-type insulator is applied to the OPGW optical cable down-leading system to ensure the insulation distance between the down-lead cable and the pole body, solve the cable detachment problem, and the operation is more reliable, which is worthy of large-scale promotion and application.

Description

Technical Field

[0001] The present application relates to a substation OPGW down-conductor grounding system, and in particular to a smart grid substation OPGW down-conductor safe operation and inspection grounding system, belonging to the smart grid OPGW operation and inspection technical field. Background Art

[0002] As a special overhead optical cable for power communication, OPGW can be installed on the same tower as the transmission line. It not only has the function of communication optical cable, but also can be used as an overhead lightning protection line. Since OPGW optical fiber communication network has the advantages of saving line resources, not being interfered by electromagnetic radiation, and high transmission rate, optical fiber composite overhead ground wires have been widely used around 2000. The current power system communication network is mainly based on OPGW optical cable channels, which lays a solid foundation for the safe transmission of various reliable real-time information for power grid operation.

[0003] With the rapid development of today's technology, optical fiber composite overhead ground wire not only has the functions of traditional overhead ground wire, but also has modern communication capabilities. It is precisely because of the advantages of OPGW, such as high reliability, good mechanical properties and low cost, that optical fiber composite overhead ground wire plays an important role at home and abroad, especially in communication systems.

[0004] Since the reserved OPGW optical cable entering the substation portal frame is in a state of no one cares for the transmission operation and maintenance unit, the substation operation and maintenance unit and the communication operation and maintenance unit, the grid operation and maintenance personnel have unclear boundaries for the maintenance of the OPGW down-cable, which makes the OPGW design simply consider the grounding problem of the line tower, and does not fully consider the design problems of the OPGW down-cable fastening installation channel, the OPGW down-cable cable winding device and grounding when the OPGW enters the substation portal frame pole body, resulting in frequent problems of induced electric corrosion and broken strands of the portal frame OPGW down-cable, and this section of the optical cable is not fully protected. With the widespread application and operation of OPGW in the power grid, the defects of the OPGW down-cable section of the station section have gradually been exposed, and a large number of OPGW down-cable damage or even burning incidents have occurred in substations of various voltage levels. In the area under the jurisdiction of the zj provincial power grid company alone, eight similar accidents occurred within three years. If the optical cable leading down part of the OPGW into the substation tower is improperly designed and the optical cable short-circuit capacity is insufficient, if there is a lightning strike or the substation bus short-circuit generates a large current, the optical cable will be damaged or even burned, resulting in interruption of communication services, which will seriously threaten the safe and stable operation of the power grid.

[0005] According to the grid regulations, no matter what the voltage level is, after entering the substation, OPGW must be reliably grounded at three points: OPGW residual cable grounding, optical fiber splicing box grounding, and cable reel residual cable rack grounding. At present, the design of OPGW terminal optical cable only considers the grounding of the line tower, and does not fully consider the grounding method of OPGW down-lead cable entering the substation portal frame pole.

[0006] Since there is no unified technical specification, the grounding safety treatment methods of the structures and substations in different places are also different. In the actual substation on-site implementation process, the OPGW down-lead cable is directly suspended and connected to the optical cable junction box without sufficient grounding, resulting in arc burns in the OPGW down-lead cable connecting to the substation structure section in 110kV and above substations. In severe cases, not only will the outer strands of the OPGW be melted, but the inner stainless steel tube and optical fiber core will also be damaged.

[0007] Currently, power grid companies still do not have a reasonable system solution. As the application scope of OPGW optical cable technology in domestic power grids continues to expand, the hidden dangers and failures of OPGW down cables during operation continue to increase year by year. It is urgent to conduct a systematic analysis of the above problems and establish solutions.

[0008] In summary, the existing technology still has several problems and defects. The key technical difficulties of the OPGW down-lead cable of the substation are as follows:

[0009] (1) The reserved optical cable of OPGW entering the portal frame of the substation is in a state of no one-man-war between the transmission operation and maintenance unit, the substation operation and maintenance unit and the communication operation and maintenance unit, resulting in unclear maintenance boundaries for the OPGW down-cable by the power grid operation and maintenance personnel. When designing OPGW, the grounding problem of the line tower is simply considered, and the design problems of the OPGW down-cable fastening installation channel, the cable winding device and the grounding of the OPGW down-cable are not fully considered when the OPGW enters the portal frame pole of the substation. As a result, the induced electric corrosion and breakage of the portal frame OPGW down-cable frequently occur, and this section of the optical cable is not fully protected. At present, the defects of the optical cable down-cable of the OPGW entry section are gradually exposed. A large number of OPGW down-cable damage or even burning incidents have occurred in substations of various voltage levels. If the optical cable down-cable part of the OPGW entering the substation tower is improperly designed and the optical cable short-circuit capacity is insufficient, if it is struck by lightning or the substation busbar short-circuits to generate a large current, the optical cable will be damaged or even burned, resulting in interruption of communication services, which seriously threatens the safe and stable operation of the power grid.

[0010] (2) The reserved safety cable fork of the prior art substation is made of metal flat steel with ferromagnetic properties, which causes inter-turn discharge and electric corrosion to break the cable strands. However, the use of metal flat steel or raw steel with ferromagnetic properties to make the reserved safety cable fork of the substation OPGW terminal has the following defects: First, the ferromagnetic material forms a closed magnetic circuit, which passes through the OPGW reserved cable, providing electromagnetic induction conditions for the OPGW reserved cable, causing the reserved cable inter-turn discharge and electric corrosion to break the cable strands. The cross-sectional area of ​​the bolt is 78 square millimeters, and the cross-sectional area of ​​the iron wire is 1 square millimeter. The core area is 35 square centimeters, which is similar to a 750VA transformer. Therefore, when the original cable drum structure encounters system overvoltage or lightning overvoltage to generate a large current (>10KA), the current will be discharged through the cable grounding, causing the turn-to-turn voltage in the cable drum to increase, resulting in turn-to-turn discharge and electrical corrosion and broken strands; secondly, the process of bundling the OPGW reserved cable with iron wire causes the iron wire to directly contact the OPGW optical cable, forming a metal galvanic corrosion and broken strand problem, which poses a major hidden danger to the power grid optical cable line and directly threatens the safe production of the power grid.

[0011] (3) In the prior art, most of the reserved optical cables at the OPGW terminals of substations are sealed with fireproof mud. The fireproof mud protects the OPGW down-lead cables at the frame in a short time. However, due to the defects of the fireproof mud itself, it will crack or even fall off if used for too long, especially when exposed to wind and sun for a long time, and its service life will be shortened. At the same time, if the fireproof mud is not sealed tightly, too much rain in winter will cause ice, which will increase the attenuation of the OPGW reserved cable in the sealed pipe. In severe cases, the OPGW reserved cable will be terminated, causing communication failures and threatening the safe production of the power grid; the fireproof mud will be affected by external conditions over time and will have gaps or cracks. Only using fireproof mud for sealing can easily cause problems such as loose sealing and loose tightening, which poses certain safety risks; usually, communication operation and maintenance personnel will only seal the casing mouth of the OPGW down cable. When the fireproof mud is used to seal the casing mouth, only the pipe mouth will be tightly sealed, and there is only air inside the casing. Therefore, the fireproof mud is very easy to fall off. At the same time, the fireproof mud is easy to crack due to wind and sun. Excessive rain in winter seeps into the casing, which will cause ice, resulting in the termination of the OPGW down cable.

[0012] (4) The prior art substation OPGW down-conductor is fastened with stainless steel belts and insulated rubber wire clamps. The substation gate pole is basically made of metal. The use of stainless steel belts to tie the OPGW down-conductor will cause the following problems: First, indirect grounding will be formed between the gate pole and the stainless steel belt, which will invisibly increase the grounding resistance of the substation grounding network; second, the contact resistance between the OPGW down-conductor and the metal gate pole will increase due to the use of stainless steel belts. When the transmission line fails or lightning strikes, high voltage will be generated, causing the OPGW down-conductor to discharge and corrode and break; third, due to thunderstorms and strong winds, the stainless steel belt is easily overloaded, which will cause the OPGW down-conductor fork to fall off and fall to the ground; fourth, some substation OPGW down-conductors are fastened with rubber wire clamps that are easy to age. If rubber wire clamps are used for a long time, the OPGW down-conductor will be disconnected. In strong winds, the down-conductor will swing, affecting the safe operation of the substation primary equipment. The rubber insulated wire clamps will age and disconnect, causing serious accidents. Summary of the invention

[0013] The present application is aimed at the research and development of related components for the OPGW optical cable downleading, and solves the difficult problems of the OPGW downleading cable system involving the safe and stable operation of the line, high voltage and communication joint parts, including the following three aspects: First, it solves the problem of unsafe, inconvenient and unreliable operation of detecting the resistance of the substation grounding network, and creatively adopts the GW9-10 / 1000 type isolation knife switch as the OPGW terminal cable grounding. The OPGW downleading cable, fork plate and junction box respectively use metal double-slot double-hole wire clamps with insulated wires, which are connected to the terminals on the grounding knife switch, and the wiring terminals under the grounding knife switch are reliably connected to the grounding point at the bottom of the gate-type pole with wires. The connecting wire is BV120MM2. When testing the grounding resistance of the grounding grid in the substation, the grounding switch must be placed in the open position with an insulating rod, and then the grounding grid in the station is tested. After the test is completed, the grounding switch must be placed in the closed position with an insulating rod; secondly, a non-metallic reserved safety cable fork based on modified polyurethane glass fiber composite material is used in the substation. It has good insulation and corrosion resistance, solves the problem of cable breakage caused by voltage corrosion between turns of the reserved cable at the OPGW optical cable terminal, and effectively solves the problem of cable breakage caused by lightning strike, thereby improving the safe operation rate of the OPGW terminal in the substation; thirdly, the 10kV pin-type insulator is improved and applied to the OPGW optical cable downlead system, which ensures the insulation distance between the downlead cable and the pole body, solves the cable detachment problem caused by the existing technical method, and is more reliable in operation and has a longer service life.

[0014] In order to achieve the above technical effects, the technical solutions adopted in this application are as follows:

[0015] Smart grid substation OPGW down-conductor safety operation and inspection grounding system, including OPGW down-conductor grounding method, OPGW terminal reserved safety cable fork plate and OPGW terminal operation and inspection reserved device fasteners;

[0016] The present application is designed to pass through a lightning arrester after the OPGW down-conductor cable enters the substation, and realizes the three-point connection and grounding of the OPGW terminal reserved cable, the OPGW reserved safety cable fork plate and the junction box by means of a grounding knife switch, so as to solve the problem that the OPGW down-conductor cable is inconvenient to measure the resistance of the substation grounding network, and solve the problem of personal safety threats caused by the OPGW down-conductor cable detecting the resistance of the substation grounding network; the OPGW down-conductor cable fork plate is designed and improved from three aspects: material, structure and size, and a method for hanging the reserved safety cable fork plate is proposed to improve the OPGW terminal reserved cable plugging design; TS-704 silicone rubber is used to replace the fireproof mud plugging sleeve to solve the problem of the fireproof mud plugging of the OPGW down-conductor cable falling off; finally, the improved pin-type insulator is applied to the OPGW optical cable down-conducting system to ensure the insulation distance between the down-conductor cable and the pole body, and solve the cable detachment problem;

[0017] First, the GW9-10 / 1000 type isolation knife switch is used for OPGW terminal cable grounding. The OPGW down-lead cable, fork plate, and junction box are respectively connected to the grounding knife switch with insulated wires using metal double-slot double-hole wire clamps and connected to the terminals. The lower wiring terminal of the grounding knife switch is reliably connected to the grounding point at the bottom of the gate-type pole with a wire; the connecting wire is BV120MM2. When testing the grounding resistance of the grounding grid in the substation, the grounding knife switch must be operated with an insulating rod to the open position, and then the grounding grid in the station is tested. After the test is completed, the grounding knife switch must be operated with an insulating rod to the closed position for operation;

[0018] Second, a non-metallic reserved safety cable fork tray based on modified polyurethane glass fiber composite material is used in the substation to solve the problem of cable breakage caused by voltage corrosion and lightning strike between turns of the reserved cable at the OPGW optical cable terminal;

[0019] Third, the 10kV pin-type insulator is improved and applied to the OPGW optical cable downlead system to ensure the insulation distance between the downlead cable and the pole body and solve the cable detachment problem.

[0020] Furthermore, the grounding method of the OPGW down-lead cable is as follows: adopting the operation scheme of connecting to the substation grounding network, when the substation OPGW terminal reserved cable is led down from the pole tower, it is installed with a non-insulated metal wire clamp, and the OPGW terminal reserved cable is reliably connected to the frame at the top of the pole tower frame, and is also connected to the substation grounding network via the ground wire at the OPGW end to ensure that the discharge current is reliably introduced into the earth. At the same time, to prevent the OPGW down-lead cable from being broken due to a transmission line fault or lightning strike when the contact resistance with the pole body increases when the OPGW down-lead cable is installed with a metal wire clamp, an insulating down-lead cable clamp is installed at the contact between the two to eliminate the discharge condition.

[0021] Furthermore, the OPGW down-conductor lightning arrester design: a customized zinc oxide combined voltage-limiting unit is used. After the OPGW down-conductor enters the substation, it first passes through a zinc oxide combined voltage-limiting unit. The OPGW down-conductor is reliably connected to the top of the tower frame through the device to protect the OPGW optical cable.

[0022] 1) When the OPGW down conductor operates at normal operating voltage, the arrester does not have any effect, which is equivalent to a circuit breaker to the ground;

[0023] 2) When a transmission line fault or thunderstorm causes the induced voltage of the OPGW down-conductor to increase, the zinc oxide combined voltage limiting unit first limits the voltage value flowing through the device, and then guides the impact current generated by the high voltage to the ground to protect the OPGW down-conductor. When the overvoltage disappears, the zinc oxide combined voltage limiting unit returns to its original state, and the OPGW down-conductor will work normally;

[0024] A customized HY1.5W-O.26 / 1.3 zinc oxide combined voltage limiting unit is used.

[0025] Furthermore, the design of the OPGW down-lead cable isolation knife switch: the outdoor single-pole isolation knife switch is used for grounding. The outdoor single-pole isolation knife switch adopts a knife-type structure, which consists of four parts, from top to bottom, namely, the safety hook, the conductive part, the support porcelain bottle and the base. The switch is self-locking when closed, and the insulating hook rod is opened and closed through the side of the knife.

[0026] The GDW9-10 / 1000 grounding switch is used to realize the three-point connection grounding of the OPGW terminal reserved cable, OPGW reserved safety cable fork plate and junction box, solving the problem of unsafe, inconvenient and unreliable operation of detecting the resistance of the substation grounding network;

[0027] The OPGW terminal reserved safety cable fork is equipped with a GW9-10 / 1000 disconnector, which is used for grounding the OPGW terminal system. The OPGW terminal reserved safety cable fork is equipped with a GW9-10 / 1000 disconnector. The OPGW terminal reserved cable, OPGW reserved safety cable fork and junction box are connected at three points through aluminum reducer and groove clamps at the upper wiring terminal of the grounding disconnector. The grounding conductor is connected to the substation grounding network at the bottom of the grounding disconnector. Under normal circumstances, the knife switch is normally closed. When the substation grounding resistance needs to be measured, the knife switch only needs to be pulled open to disconnect the grounding wire, eliminating the risk of induced electric shock for operation and maintenance personnel when climbing the pole to operate the grounding wire, thereby shortening the operation and maintenance time.

[0028] Furthermore, the reserved safety cable fork tray is made of non-metallic materials, and a cross-shaped reserved safety cable fork tray is used;

[0029] There are no less than 4 points for OPGW cable winding and bundling. The remaining length of each cable coil is no less than the length of the cable laid on the ground plus 5 meters. The diameter of the OPGW cable is 13mm, and the diameter formed by the fork coil is ≥ (13×40=520mm);

[0030] The fork plate rod is 1m long and the inner diameter formed by the cross is 760mm.

[0031] Further, the reserved safety cable fork tray hanging height method: the OPGW terminal reserved safety cable fork tray is designed according to two situations: one is the single-pole hanging height process design; the other is the double-pole hanging height process design. Regardless of the single-pole hanging height or double-pole hanging height, the OPGW terminal reserved safety cable fork tray includes the following parts:

[0032] 1) The OPGW terminal reserves the upper and lower cross arms of the safety cable fork tray, where the lower cross arm is installed 2.5 meters above the ground and the upper cross arm is installed 0.39 meters above the lower cross arm;

[0033] 2) The reserved safety cable fork tray of the OPGW terminal is composed of two modified polyurethane glass fiber insulation rods and equipped with special insulation sleeves, so that the fork tray composed of the insulation rods is insulated from the upper and lower cross arms;

[0034] Furthermore, the OPGW terminal reserved cable plugging design: a four-step plugging method is proposed to solve the OPGW down-lead cable terminal reserved cable plugging problem:

[0035] The first step is to clean the surface: remove rust, dust and oil from the casing and clean the surface;

[0036] Step 2: Glue application: Evenly squeeze glue on the clean surface of the casing, and make sure that the casing mouth is closed and fixed by the glue;

[0037] The third step is curing: seal the OPGW cable casing and place it in the air to allow the glue to cure naturally. Curing requires a long enough time. Before further processing or packaging the bonded parts, wait long enough to ensure that the bonding firmness and integrity are not affected.

[0038] The fourth step is sealing: the heat shrink tubing is used to strengthen the sealing of the protective tube, and no cracking or falling off will occur during long-term use;

[0039] During the cable sealing process, in order to avoid unnecessary damage to the optical cable and ensure that the force on the optical cable is evenly distributed, it is prohibited to pull or step on the optical cable.

[0040] Furthermore, the fasteners of the reserved device for OPGW terminal operation and inspection: the insulators are applied to the OPGW optical cable downleading system, the pin insulators are used, and the high-voltage lines use composite pin insulators. The pin insulators have special steel hardware heads. The most critical thing is to solve the problem of electrical breakdown at the insulator interface:

[0041] The 10kV pin-type insulator is combined with the galvanized clamp used in power engineering to form the fastening assembly of the OPGW down-conductor. The OPGW down-conductor fastener adopts this method;

[0042] 1) After the OPGW terminal reserved cable passes through the tension wire clamp at the upper end of the portal frame tower in the substation, the OPGW down-lead cable at the portal pole is bundled along with the extended fastener, so that the OPGW terminal reserved cable maintains a sufficient distance from the tower at the upper end of the portal frame tower. The distance between the OPGW down-lead cable and the pole body in this section is designed to be more than 300mm;

[0043] 2) Ensure that the OPGW down-lead cable is at a tower insulation distance of more than 150mm on the portal frame crossbeam platform. The OPGW down-lead cable here is generally installed with a card-type fastening assembly;

[0044] 3) The down-lead cable after passing through the crossbeam of the portal frame pole should maintain a distance of more than 80mm from the pole tower, and is designed to be installed using the fastening components of the power engineering galvanized clamp and pin-type insulator.

[0045] Compared with the prior art, the innovations and advantages of this application are:

[0046] First, this application develops related components for OPGW optical cable downleading, and solves many difficult problems of OPGW downleading cable system involving safe and stable operation of line, high voltage and communication junction, including the following three aspects: First, it solves the problem of unsafe, inconvenient and unreliable operation of detecting the resistance of the substation grounding network, and creatively adopts GW9-10 / 1000 type isolation knife switch for OPGW terminal cable grounding. The OPGW downlead cable, fork plate and junction box respectively use metal double-slot double-hole wire clamps with insulated wires, which are connected to the terminals on the grounding knife switch, and the wiring terminals under the grounding knife switch are reliably connected to the grounding point at the bottom of the gate pole with wires. The connecting wire is BV120MM2. When testing the grounding resistance of the grounding grid in the substation, the grounding switch must be placed in the open position with an insulating rod, and then the grounding grid in the station is tested. After the test is completed, the grounding switch must be placed in the closed position with an insulating rod; secondly, a non-metallic reserved safety cable fork based on modified polyurethane glass fiber composite material is used in the substation. It has good insulation and corrosion resistance, solves the problem of cable breakage caused by voltage corrosion between turns of the reserved cable at the OPGW optical cable terminal, and effectively solves the problem of cable breakage caused by lightning strike, thereby improving the safe operation rate of the OPGW terminal in the substation; thirdly, the 10kV pin-type insulator is improved and applied to the OPGW optical cable downlead system, which ensures the insulation distance between the downlead cable and the pole body, solves the cable detachment problem caused by the existing technical method, and is more reliable in operation and has a longer service life.

[0047] Second, the present application designs that after the OPGW down-lead cable enters the substation, it first passes through a lightning arrester, and realizes the three-point connection and grounding of the OPGW terminal reserved cable, the OPGW reserved safety cable fork plate and the junction box by means of a grounding knife switch, which completely solves the problem that the OPGW down-lead cable is inconvenient to measure the resistance of the substation grounding network, and completely solves the problem of personal safety threats caused by the OPGW down-lead cable detecting the resistance of the substation grounding network; the OPGW down-lead cable fork plate is designed and improved from three aspects: material, structure and size, and a method for hanging the reserved safety cable fork plate is proposed to improve the OPGW terminal reserved cable sealing design; TS-704 silicone rubber is used to replace the fireproof mud sealing sleeve to solve the problem of the fireproof mud sealing falling off of the OPGW down-lead cable; finally, by applying the improved pin-type insulator to the OPGW optical cable down-lead system, the insulation distance between the down-lead cable and the pole body is guaranteed, the cable falling problem is completely solved, and the operation is more reliable. After operation practice, it was verified that this method not only effectively solved the problem of broken strands caused by electric corrosion and induction discharge in the OPGW down-conductor of the substation, which further improved the operation index of the OPGW down-conductor; but also greatly facilitated the operation and maintenance personnel, and solved the long-standing problems of heavy workload, high operation risk and increased power grid operation and inspection cost in the substation grounding grid resistance operation in the power transmission and transformation profession. This method is worthy of large-scale promotion and application.

[0048] Third, the OPGW terminal system of the present application adopts an operation scheme of connecting to the substation grounding network. When the substation OPGW terminal reserved cable is led down from the pole tower, it is installed with a non-insulated metal wire clamp. The OPGW terminal reserved cable is reliably connected to the frame at the top of the pole tower frame, and is also connected to the substation grounding network via the ground wire at the OPGW end to ensure that the discharge current is reliably introduced into the earth. At the same time, in order to prevent the OPGW down-lead cable from being installed with a metal wire clamp and the contact resistance with the pole body increases, causing a communication interruption accident due to a transmission line fault or a broken strand caused by lightning, an insulating down-lead cable clamp is installed at the contact between the two to eliminate the discharge conditions, and the grounding of the OPGW down-lead cable is safer and more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is the design drawing of the OPGW down-lead cable isolation switch.

[0050] Figure 2 This is a schematic diagram of the design and installation of the grounding switch.

[0051] Figure 3 It is a schematic diagram of the parameters of the reserved safety cable fork disk made of non-metallic materials.

[0052] Figure 4 This is a schematic diagram of the size design of the OPGW reserved cable.

[0053] Figure 5 This is a schematic diagram of the uplink packet loss rate when the UAV is 2 km away from the ground station.

[0054] Figure 6 This is a front view diagram of the OPGW substation architecture installation for this application. DETAILED DESCRIPTION

[0055] The following, in conjunction with the accompanying drawings, further describes the technical solution of the smart grid substation OPGW down-lead cable safe operation and inspection grounding system provided by the present application, so that technicians in this field can better understand the present application and implement it.

[0056] In recent years, a large number of optical fiber composite overhead ground wires (OPGW) have been built and applied in substations. Since the reserved optical cable of OPGW entering the portal frame of the substation is in a no-man's land state among the transmission operation and maintenance unit, the substation operation and maintenance unit, and the communication operation and maintenance unit, the grid operation and maintenance personnel have unclear maintenance boundaries for the OPGW down-cable, which makes the OPGW design simply consider the grounding problem of the line tower, and does not fully consider the design problems of the OPGW down-cable fastening installation channel, the cable winding device and grounding of the OPGW down-cable when the OPGW enters the portal frame pole of the substation, resulting in the OPGW down-cable of the portal frame hanging in the air, and this section of the optical cable is not fully protected. Multiple accidents have occurred, seriously threatening the safety of the power grid. This application aims at a series of problems existing in the OPGW down-cable of the substation, and provides a safe operation and inspection grounding system solution for the OPGW down-cable of the substation.

[0057] The present application is designed to pass through a lightning arrester after the OPGW down-conductor enters the substation, and realizes the three-point connection and grounding of the OPGW terminal reserved cable, OPGW reserved safety cable fork plate and junction box by means of a grounding knife switch, which completely solves the problem that the OPGW down-conductor cable is inconvenient to measure the resistance of the substation grounding network, and completely solves the problem of personal safety threat caused by the OPGW down-conductor cable detecting the resistance of the substation grounding network; the OPGW down-conductor fork plate is designed and improved from three aspects: material, structure and size, and a method for hanging the reserved safety cable fork plate is proposed to improve the OPGW terminal reserved cable sealing design; TS-704 silicone rubber is used to replace the fireproof mud sealing sleeve to solve the problem of the fireproof mud sealing falling off of the OPGW down-conductor; finally, the improved pin-type insulator is applied to the OPGW optical cable down-conducting system to ensure the insulation distance between the down-conductor cable and the pole body, which completely solves the cable falling problem and makes the operation more reliable.

[0058] After operation practice, it was verified that this method not only effectively solved the problem of broken strands caused by electric corrosion and induction discharge in the OPGW down-conductor of the substation, which further improved the operation index of the OPGW down-conductor; but also greatly facilitated the operation and maintenance personnel, and solved the long-standing problems of heavy workload, high operation risk and increased power grid operation and inspection cost in the substation grounding grid resistance operation in the power transmission and transformation profession. This method is worthy of large-scale promotion and application.

[0059] It includes three aspects: OPGW down-lead cable grounding method, OPGW terminal reserved safety cable fork plate and OPGW terminal operation and inspection reserved device fasteners.

[0060] 1. Grounding method of OPGW down-lead cable

[0061] The OPGW terminal system adopts the operation scheme of connecting to the substation grounding network. When the substation OPGW terminal reserved cable is led down from the pole tower, it is installed with a non-insulated metal wire clamp. The OPGW terminal reserved cable is reliably connected to the frame at the top of the pole tower frame, and is also connected to the substation grounding network through the ground wire at the OPGW end to ensure that the discharge current is reliably introduced into the earth. At the same time, in order to prevent the OPGW down-lead cable from being installed with a metal wire clamp and the contact resistance with the pole body increases, causing a transmission line fault or a broken strand caused by lightning strike, resulting in a communication interruption accident, an insulated down-lead cable clamp is installed at the contact between the two to eliminate the discharge conditions.

[0062] When the OPGW down cable just enters the pole tower, it will first pass through a lightning arrester and then introduce a grounding switch at the grounding point.

[0063] (I) Design of OPGW down conductor arrester

[0064] A customized zinc oxide combined voltage limiting unit is used. After the OPGW down-lead cable enters the substation, it first passes through a zinc oxide combined voltage limiting unit. The OPGW down-lead cable is reliably connected to the top of the tower frame through the device to protect the OPGW optical cable.

[0065] 1) When the OPGW down conductor operates at normal operating voltage, the arrester does not have any effect, which is equivalent to a circuit breaker to the ground;

[0066] 2) When a transmission line fault or thunderstorm causes the induced voltage of the OPGW down-conductor to increase, the zinc oxide combined voltage limiting unit first limits the voltage value flowing through the device, and then guides the impact current generated by the high voltage to the ground to protect the OPGW down-conductor. When the overvoltage disappears, the zinc oxide combined voltage limiting unit returns to its original state, and the OPGW down-conductor will work normally;

[0067] This application uses a customized HY1.5W-O.26 / 1.3 zinc oxide combined voltage limiting unit.

[0068] (II) Design of OPGW down-lead cable isolation switch

[0069] An outdoor single-pole isolating knife switch is used for grounding. The outdoor single-pole isolating knife switch adopts a knife-type structure, which consists of four parts, from top to bottom: a safety hook, a conductive part, a supporting porcelain bottle and a base. It will be self-locking when closed and will not automatically trip due to its own weight or electric force. The insulating hook rod is opened and closed through the side of the knife.

[0070] The GDW9-10 / 1000 outdoor single-pole disconnector used in the design is used in a 10kV power system. The structural diagram of the disconnector is as follows: Figure 1 shown.

[0071] The GDW9-10 / 1000 grounding switch is used to realize the three-point connection grounding of the OPGW terminal reserved cable, OPGW reserved safety cable fork plate and junction box, solving the problem of unsafe, inconvenient and unreliable operation of detecting the resistance of the substation grounding network. Figure 2 The figure shows the installation diagram of grounding switch.

[0072] The OPGW terminal reserved safety cable fork is equipped with a GW9-10 / 1000 disconnector, which is used for grounding the OPGW terminal system. The OPGW terminal reserved safety cable fork is equipped with a GW9-10 / 1000 disconnector. The OPGW terminal reserved cable, OPGW reserved safety cable fork and junction box are connected at three points through aluminum reducer and groove clamps at the upper wiring terminal of the grounding disconnector. The grounding conductor is connected to the substation grounding network at the bottom of the grounding disconnector. Under normal circumstances, the knife switch is normally closed. When it is necessary to measure the grounding resistance of the substation, just pull the knife switch open and the grounding wire can be disconnected, eliminating the risk of induced electric shock for the operation and maintenance personnel when climbing the pole to operate the grounding wire, shortening the operation and maintenance time and greatly facilitating the operation and maintenance personnel.

[0073] 2. OPGW terminal reserved safety cable fork tray

[0074] The reserved safety cable fork tray used in the prior art substation is made of metal flat steel with ferromagnetic properties, which provides electromagnetic induction conditions for the OPGW reserved cable, causing inter-turn discharge and electric corrosion to break the strands. However, the reserved safety cable fork tray of the OPGW terminal of the substation made of metal flat steel or raw steel with ferromagnetic properties has the following defects:

[0075] First, the ferromagnetic material forms a closed magnetic circuit, which passes through the OPGW reserved cable, providing electromagnetic induction conditions for the OPGW reserved cable, causing inter-turn discharge, electrical corrosion and broken strands of the reserved cable. The cross-sectional area of ​​the bolt is 78 square millimeters, the cross-sectional area of ​​the iron wire is 1 square millimeter, and the core area is 35 square centimeters, which is similar to a 750VA transformer. Therefore, when the original cable drum structure encounters system overvoltage or lightning overvoltage to generate a large current (>10KA), the current will be discharged through the residual cable grounding, causing the inter-turn voltage in the cable drum to increase, inter-turn discharge, and electrical corrosion and broken strands.

[0076] The second is the process of bundling the OPGW reserved cable with iron wire, which causes the iron wire to directly contact the OPGW optical cable, resulting in a problem of metal galvanic corrosion and breakage, causing major hidden dangers to the power grid optical cable line and directly threatening the safe production of the power grid.

[0077] (I) Design of reserved safety cable fork tray materials

[0078] The reserved safety cable fork made of metal flat steel or raw steel with ferromagnetic properties can easily provide electromagnetic induction conditions for the OPGW reserved cable, causing the reserved cable to break due to discharge and corrosion between turns. Therefore, non-metallic materials are used to make the reserved safety cable fork, such as Figure 3 As shown, a comparison of the flexural strength, tensile strength, stability, corrosion resistance and life of non-metallic materials is shown.

[0079] By comparing and analyzing the parameters of different non-metallic materials, it is found that modified polyurethane glass fiber composite materials have advantages in various indicators, especially in the indicator of outdoor life, which can reduce the number of years of maintenance. Therefore, modified polyurethane glass fiber composite materials are used.

[0080] (II) Design of reserved safety cable fork tray structure

[0081] The reserved cable is wound on the fork disc. Based on the comparison of manufacturing complexity and manufacturing cost parameters, a cross-shaped reserved safety cable fork disc is adopted.

[0082] (III) Design of reserved safety cable fork tray dimensions

[0083] There are no less than 4 points for OPGW cable winding and bundling. The reserved space for each cable drum is no less than the cable laid on the ground plus 5 meters. The size design drawing of OPGW reserved safety cable fork drum is as follows: Figure 4 As shown, the diameter of the OPGW optical cable used in this application is 13 mm, and the diameter formed by the fork plate is ≥ (13×40=520 mm).

[0084] like Figure 4 As shown, the fork rod is 1m long and the inner diameter of the cross is 760mm, which is larger than 520mm and meets the specification requirements.

[0085] (IV) Method for hanging the safety cable fork tray at a high height

[0086] In order to facilitate the management and operation of the substation operation and maintenance personnel, this application designs the OPGW terminal reserved safety cable fork tray according to two situations: one is a single-pole hanging height process design; the other is a double-pole hanging height process design. Regardless of the single-pole hanging height or double-pole hanging height, the OPGW terminal reserved safety cable fork tray includes the following parts:

[0087] 1) The OPGW terminal reserves the upper and lower cross arms of the safety cable fork tray, where the lower cross arm is installed 2.5 meters above the ground and the upper cross arm is installed 0.39 meters above the lower cross arm;

[0088] 2) The reserved safety cable fork tray of the OPGW terminal is composed of two modified polyurethane glass fiber insulation rods and equipped with special insulation sleeves, so that the fork tray composed of the insulation rods is insulated from the upper and lower cross arms;

[0089] The structure of the reserved cable rack of the OPGW terminal is shown as follows: Figure 5 As shown, the front view of the substation OPGW terminal reserved cable installation is as follows Figure 6 shown.

[0090] (V) OPGW terminal reserved cable plugging design

[0091] In the prior art, most substation OPGW terminal reserved optical cables are sealed with fireproof mud. The fireproof mud protects the OPGW down-lead cables at the frame in a short time. However, the fireproof mud itself has its own functional defects. If it is used for too long, it will crack or even fall off, especially if it is exposed to wind and sun for a long time, and its service life will be shortened. At the same time, if the fireproof mud is not sealed tightly, too much rain in winter will cause ice, which will increase the attenuation of the OPGW reserved cable in the sealing pipe. In severe cases, the OPGW reserved cable will terminate, causing communication failures and threatening the safe production of the power grid. The reasons for this problem are as follows:

[0092] 1) Fireproof mud will be affected by external conditions over time and will have gaps or cracks. Using only fireproof mud for plugging can easily cause problems such as loose plugging and loose fastening, which poses certain safety risks;

[0093] 2) Normally, communication operation and maintenance personnel will only seal the casing opening of the OPGW down-lead cable. When the fire-proof mud is used to seal the casing opening, only the opening will be tightly sealed, and there is only air inside the casing. Therefore, the fire-proof mud is very easy to fall off. At the same time, the fire-proof mud is easy to crack due to wind and sun. Excessive rain in winter seeps into the casing, which will cause ice to form and lead to the termination of the OPGW down-lead cable.

[0094] In view of the problems existing in the blocking method of the OPGW down-lead cable of the prior art substation, this application designs and proposes a four-step blocking method based on the actual situation to solve the problem of blocking the reserved cable at the OPGW down-lead cable terminal.

[0095] The first step is to clean the surface: remove rust, dust and oil from the casing and clean the surface;

[0096] Step 2: Glue application: Evenly squeeze glue on the clean surface of the casing, and make sure that the casing mouth is closed and fixed by the glue;

[0097] The third step is curing: seal the OPGW cable casing and place it in the air to allow the glue to cure naturally. Curing requires a long enough time. Before further processing or packaging the bonded parts, wait long enough to ensure that the bonding firmness and integrity are not affected.

[0098] The fourth step is sealing: the heat shrink tubing is used to strengthen the sealing of the protective tube, and cracking and falling off will not occur during long-term use.

[0099] In the process of cable sealing, in order to avoid unnecessary damage to the optical cable and ensure that the optical cable is evenly stressed, it is prohibited to pull or step on the optical cable. Since there is static electricity in the optical cable casing, communication operation and maintenance personnel should wear insulating gloves to prevent excessive static electricity. Since the optical cable casing is located at a high position, a safety belt should be used to prevent people from falling.

[0100] 3. Fasteners for OPGW terminal inspection and maintenance reserved device

[0101] The existing substation OPGW down-conductor is fastened with stainless steel belts and insulated rubber wire clamps. The substation gate pole is basically made of metal. The use of stainless steel belts to tie the OPGW down-conductor will have the following problems: First, indirect grounding will be formed between the gate pole and the stainless steel belt, which will invisibly increase the grounding resistance of the substation grounding network; second, the contact resistance between the OPGW down-conductor and the metal gate pole will increase due to the use of stainless steel belts. When the transmission line fails or lightning strikes, high voltage will be generated, causing the OPGW down-conductor to discharge and corrode and break; third, due to thunderstorms and strong winds, the stainless steel belt is easily overloaded, which will cause the OPGW down-conductor fork to fall off and fall to the ground; fourth, some substation OPGW down-conductors will be fastened with rubber wire clamps that are easy to age. If rubber wire clamps are used for a long time, the OPGW down-conductor will have the problem of cable detachment. In strong winds, the down-conductor will swing, affecting the safe operation of the substation primary equipment. The rubber insulated wire clamps age and detach.

[0102] The present application applies insulators to the OPGW optical cable downleading system, using pin-type insulators. High-voltage lines use composite pin-type insulators. The pin-type insulators have special steel hardware heads. The most critical thing is that the electrical breakdown problem of the insulator interface is solved.

[0103] The present application combines a 10kV pin-type insulator with a galvanized clamp for power engineering to form a fastening component for an OPGW down-conductor. The use of this type of OPGW down-conductor fastener solves the risk of stainless steel strips increasing the grounding resistance of the substation grounding grid. The fastener has high mechanical strength, which prevents the down-conductor from swaying due to wind in windy weather, thereby affecting the safe operation of the substation primary equipment.

[0104] 1) After the OPGW terminal reserved cable passes through the tension wire clamp at the upper end of the portal frame tower in the substation, the OPGW down-lead cable at the portal pole is bundled along with the extended fastener, so that the OPGW terminal reserved cable maintains a sufficient distance from the tower at the upper end of the portal frame tower. The distance between the OPGW down-lead cable and the pole body in this section is designed to be more than 300mm;

[0105] 2) Ensure that the OPGW down-lead cable is at a tower insulation distance of more than 150mm on the portal frame crossbeam platform. The OPGW down-lead cable here is generally installed with a card-type fastening assembly;

[0106] 3) The down-lead cable after passing through the crossbeam of the portal frame pole should maintain a distance of more than 80mm from the pole tower, and is designed to be installed using the fastening components of the power engineering galvanized clamp and pin-type insulator.

Claims

1. Smart grid substation OPGW down-lead cable safety operation and inspection grounding system, characterized by: It includes three aspects: OPGW down-lead cable grounding method, OPGW terminal reserved safety cable fork plate and OPGW terminal reserved device fasteners; After the OPGW down-lead cable enters the substation, it first passes through the lightning arrester and is grounded at three points by means of a grounding switch, namely, the OPGW terminal reserved cable, the OPGW reserved safety cable fork plate and the junction box. This solves the problem that it is inconvenient to measure the resistance of the substation grounding network with the OPGW down-lead cable, and solves the problem of personal safety threats caused by the OPGW down-lead cable detecting the resistance of the substation grounding network. The design and improvement of the OPGW down-lead cable fork plate was carried out from three aspects: material, structure and size. A method for hanging the reserved safety cable fork plate was proposed to improve the design of the reserved cable plugging of the OPGW terminal. TS-704 silicone rubber was used to replace the fireproof mud plugging sleeve to solve the problem of the fireproof mud plugging of the OPGW down-lead cable falling off. Finally, the improved pin-type insulator was applied to the OPGW optical cable down-lead system to ensure the insulation distance between the down-lead cable and the pole body, solving the problem of cable detachment. First, use GW9-10 / 1000 type isolation switch for OPGW terminal cable grounding. The OPGW down-lead cable, fork plate, and junction box use metal double-slot double-hole wire clamps with insulated wires, which are connected to the grounding switch and connected to the terminal. The wiring terminal under the grounding switch is reliably connected to the grounding point at the bottom of the gate-type pole with a wire. The connecting wire adopts BV120MM2. When testing the grounding resistance of the grounding grid in the substation, the grounding switch must be placed in the open position with an insulating rod, and then the grounding grid in the station is tested. After the test is completed, the grounding switch must be placed in the closed position with an insulating rod for operation; Second, a non-metallic reserved safety cable fork tray based on modified polyurethane glass fiber composite material is used in the substation to solve the problem of cable breakage caused by voltage corrosion and lightning strike between turns of the reserved cable at the OPGW optical cable terminal; Third, the 10kV pin-type insulator is improved and applied to the OPGW optical cable down-lead system to ensure the insulation distance between the down-lead cable and the pole body and solve the cable debonding problem; OPGW down-lead cable grounding method: adopt the operation scheme of access to the substation grounding network. When the substation OPGW terminal reserved cable is led down from the pole tower, it is installed with a non-insulated metal wire clamp. The OPGW terminal reserved cable is reliably connected to the frame at the top of the pole tower frame, and is also connected to the substation grounding network through the ground wire at the end of the OPGW to ensure that the discharge current is reliably introduced into the earth. At the same time, to prevent the OPGW down-lead cable from being broken due to power transmission line faults or lightning strikes when the contact resistance between the OPGW down-lead cable and the pole increases when the metal wire clamp is used for installation, an insulated down-lead cable clamp is installed at the contact between the two to eliminate the discharge conditions; The OPGW terminal reserved safety cable fork is equipped with a GW9-10 / 1000 disconnector, which is used for grounding the OPGW terminal system. The OPGW terminal reserved safety cable fork is equipped with a GW9-10 / 1000 disconnector. The OPGW terminal reserved cable, OPGW reserved safety cable fork and junction box are connected at three points through the aluminum material reducer and groove wire clamp at the upper wiring terminal of the grounding disconnector. The grounding wire is connected to the substation grounding network at the bottom of the grounding disconnector. Under normal circumstances, the knife switch is normally closed. When the substation grounding resistance needs to be measured, the knife switch only needs to be pulled open to disconnect the grounding wire, eliminating the risk of inductive electric shock for the operation and maintenance personnel who climb the pole to operate the grounding wire, thus shortening the operation and maintenance time. OPGW terminal inspection and maintenance reserved device fasteners: Insulators are applied to the OPGW optical cable downleading system, using pin-type insulators. High-voltage lines use composite pin-type insulators. Pin-type insulators have special steel hardware heads to solve the problem of electrical breakdown at the insulator interface: The 10kV pin-type insulator is combined with the galvanized clamp used in power engineering to form the fastening assembly of the OPGW down-conductor. The OPGW down-conductor fastener adopts this method; 1) After the OPGW terminal reserved cable passes through the tension wire clamp at the upper end of the portal frame tower in the substation, the OPGW down-lead cable at the portal pole is bundled along with the extended fastener, so that the OPGW terminal reserved cable maintains a sufficient distance from the tower at the upper end of the portal frame tower. The distance between the OPGW down-lead cable and the pole body in this section is designed to be more than 300mm; 2) Ensure that the OPGW down-lead cable is at a tower insulation distance of more than 150mm on the portal frame crossbeam platform. The OPGW down-lead cable here is generally installed with a card-type fastening assembly; 3) The down-lead cable after passing through the portal frame pole crossbeam should maintain a distance of more than 80mm from the pole tower, and is designed to be installed using the fastening components of the power engineering galvanized clamp and pin-type insulator.

2. According to claim 1, the OPGW down-lead cable safety operation and inspection grounding system for smart grid substation is characterized in that: OPGW down-conductor lightning arrester design: A customized zinc oxide combined voltage-limiting unit is used. After the OPGW down-conductor enters the substation, it first passes through a zinc oxide combined voltage-limiting unit. The OPGW down-conductor is reliably connected to the top of the tower frame through this device to protect the OPGW optical cable. 1) When the OPGW down conductor operates at normal operating voltage, the arrester does not have any effect, which is equivalent to a circuit breaker to the ground; 2) When a transmission line fault or thunderstorm causes the induced voltage of the OPGW down-conductor to increase, the zinc oxide combined voltage limiting unit first limits the voltage value flowing through the device, and then guides the impact current generated by the high voltage to the ground to protect the OPGW down-conductor. When the overvoltage disappears, the zinc oxide combined voltage limiting unit returns to its original state, and the OPGW down-conductor will work normally; A customized HY1.5W-O.26 / 1.3 zinc oxide combined voltage limiting unit is used.

3. According to claim 1, the OPGW down-lead cable safety operation and inspection grounding system for smart grid substation is characterized in that: OPGW down-lead cable isolation switch design: outdoor single-pole isolation switch is used for grounding. The outdoor single-pole isolation switch adopts a knife-type structure, which consists of four parts, from top to bottom, including the safety hook, the conductive part, the support porcelain bottle and the base. It is self-locking when closed, and the insulating hook rod is opened and closed through the side of the knife. The GDW9-10 / 1000 grounding switch is used to realize three-point connection and grounding of the OPGW terminal reserved cable, OPGW reserved safety cable fork plate and junction box, thus solving the problem of unsafe, inconvenient and unreliable operation in detecting the resistance of the substation grounding network.

4. According to claim 1, the OPGW down-lead cable safety operation and inspection grounding system for smart grid substation is characterized in that: The reserved safety cable fork tray is made of non-metallic materials and a cross-shaped reserved safety cable fork tray is used; There are no less than 4 points for OPGW cable winding and bundling. The remaining length of each cable reel shall not be less than the length of the cable laid on the ground plus 5 meters. The diameter of the OPGW cable used is 13mm, and the diameter formed by the fork reel is ≥ (13×40=520mm); The fork plate rod is 1m long and the inner diameter formed by the cross is 760mm.

5. According to claim 1, the OPGW down-lead cable safety operation and inspection grounding system for smart grid substation is characterized in that: Reserved safety cable fork tray hanging method: The reserved safety cable fork tray of the OPGW terminal is designed according to two situations: one is the single-pole hanging height process design; the other is the double-pole hanging height process design. Regardless of the single-pole hanging height or double-pole hanging height, the reserved safety cable fork tray of the OPGW terminal includes the following parts: 1) The OPGW terminal reserves the upper and lower cross arms of the safety cable fork tray, where the lower cross arm is installed 2.5 meters above the ground and the upper cross arm is installed 0.39 meters above the lower cross arm; 2) The reserved safety cable fork tray of the OPGW terminal is composed of two modified polyurethane glass fiber insulation rods and equipped with special insulation sleeves to insulate the fork tray composed of the insulation rods from the upper and lower cross arms.

6. According to claim 1, the OPGW down-lead cable safety operation and inspection grounding system for smart grid substation is characterized in that: OPGW terminal reserved cable plugging design: A four-step plugging method is proposed to solve the problem of plugging the reserved cable at the OPGW down-lead cable terminal: The first step is to clean the surface: remove rust, dust and oil from the casing and clean the surface; Step 2: Glue application: Evenly squeeze glue on the clean surface of the casing, and make sure that the casing mouth is closed and fixed by the glue; The third step is curing: seal the OPGW cable casing and place it in the air to allow the glue to cure naturally. Curing requires a long enough time. Before further processing or packaging the bonded parts, wait long enough to ensure that the bonding firmness and integrity are not affected. The fourth step is sealing: the heat shrink tubing is used to strengthen the sealing of the protective tube, and no cracking or falling off will occur during long-term use; During the cable sealing process, in order to avoid unnecessary damage to the optical cable and ensure that the force on the optical cable is evenly distributed, it is prohibited to pull or step on the optical cable.

Images