Design of portable quick assembly and disassembly device for short-circuit grounding wire

Ying ZHAO，Xiang MENG*，Yan-juan LI

（1 Electrical&Information Engineering College，Beihua University，Jilin 132021，China）

（2 College of Information and Computer Engineering，Northeast Forestry University，Harbin 150040，China）

Abstract：In order to solve the problems of complicated assembly and disassembly of existing grounding wire devices，such as high working strength，weak connection and easy falling off，a portable quick assembly and disassembly device for short-circuit grounding wire is designed in this paper，which uses fast connection and energy storage technology to realize quick reliable assembly and disassembly for high-voltage grounding wire devices，and makes a great breakthrough in the integration of rapidity and reliability of assembly and disassembly for grounding wire devices.The application in the field shows that the device can improve the efficiency and safety of electricalwork.

Key words：Grounding wire device，Energy storage technology，Assembly and disassembly device

1 Introduction

In order to ensure the safety of workers，technical measures should be taken to ensure the safety of electrical equipment and power line during power failure maintenance.Grounding wires should be installed on all or part of the electrical equipment.Usually，grounding wires are connected to the electrical equipmentmanually；its role is tomake the work place always in the protection of“ground potential”，and at the same time to prevent the damage of the residual charge and the induced charge to the human body.In the event of power transmission error，it can make the protection work，quickly cut off the power supply，to prevent the dangerous voltage and arc generated by accidental call.

At present domestic 220 kV transmission linemaintenance work，the installation form of common ground wire is completed by connecting and fixing the insulation operating rod of the front assembly gap with the ground wire clip with assembly handle，in the existing technology，the common wire terminal clamp of carrying type groundingwire is classified into two types according to the working principle of the wire clamping mechanism：screw compression type and spring compression type［1-2］.According to the different situation of the scene from the two kinds ofworking principle，it evolves into the single tongue spring type，double tongue spring type，flatmouth type and other styles ofwire clip.Screw compression type has the advantages of relatively stable connection，good durability，but it is difficult to install and disassemble，timeconsuming and laborious，manual rotation of bolts to tighten the connection with the wire.Spring compression type has a simple structure，easy to assemble and disassemble，but the shrapnel is easy to damage，and is not suitable for line wire.The above two structures cannot achieve rapid disassembly，and easy to shake，even in the process of tightening off.This phenomenon increases the working intensity and grounding time.When the ground wire is installed and the operating rod iswithdrawn，it is lack of portability because the position of the front borehole cannot be seen and the operating rod is pulled out only by feeling［3］.

A portable quick assembly and disassembly device for short circuitgroundingwire design use the technology of quick connection and energy storage to realize the quick reliable assembly and dis-assembly of high voltage grounding line device.Application in the field shows that the device is simple，fast，reliable and can improve the efficiency and safety of electricalwork.

2 System com positions of quick assemb ly and disassem b ly device for short circuit grounding

The quick assembly and disassembly device for short circuitgroundingwire are shown in Fig.1，including four parts：grounding wire，wire terminal clamp，clamp rod interface and insulating operating rod.

Fig.1 Com position of the quick assemb Iy and disassemb Iy device for short circuit grounding w ire

3 Work ing p rincip le of quick assem b ly and disassem b ly device for short circuit grounding

3.1 Principle of butt joint

The interface between the wire terminal clamp and the clamp rod is directly connected by thread，while the interface between the insulating operating rod and the clamp rod is automatically extended into the center through the conical circular hole.The action sequence diagram is shown in Fig.2［4］.In the long-distance butt joint，the butthead of the insulating operating rod first contacts with the outer wall of the tapered hole，and then slowly enters the interface of the clamp rod through the guiding function of the cone surface，and then the locking is completed.

Fig.2 Tim ing diagram of the interface between the insu Iated operating rod and the c Iam p rod

3.2The operating principle of locking

In the process of insulating operating rod entering into the clamp rod interface，insulating operating rod pushes the block inside the clamp rod interface，make the compression spring compression in the clamp rod interface and store energy.Due to the limitation of the inner wall diameter of the interface，the locking block on the insulating operating rod has been shrinking inside the insulating operating rod during the entry process.With the continuous deepening of the insulating operating rod，when the locking block moves to the position of the internal clamp slot on the interface of the clamp rod，due to the sudden expansion of the inner wall diameter，the locking block on the insulating operating rod pops up rapidly under the action of the elastic force of the compression spring and the axial displacement of the locking block inside the restricting insulating operating rod completes the locking.At this point，the internal state of the locking device of the insulating operating rod is shown in Fig.3.

Fig.3 Diagram of Iocking working state

3.3 The operating principle of unlocking

In the locking state，the clamp block is restrained by the clamp slot on the axis and cannotmove in the axial direction.The shape of the clamp slot in the interface of the clamp rod is shown in Fig.4（a）.In case of locking，the circumferential motion of the clamp block is unrestrained.When the insulating rod is rotated in hand，the clamp block can come out of the clamp slot from the circumferential direction.At this time，the clamp block retracted the insulating operating rod and the axial direction of the insulating operating rod is no longer restrained，as shown in Fig.4（b）and（c）.Under the action of the elastic force of the compression spring on the interface of the clamp rod，the insulating operating rod is automatically ejected to complete the unlock.

Fig.4 The operating p rincip Ie of un Iocking

3.4 Principle of connection and release between insulated operating rods

The connection between the two insulating rods is the same as the connection between the clamp rod interface and the insulating operating rod，which is realized by restricting the axialmotion when the clamping device enter the clamp slot in the pipe.In unlocking，the clamp block leaves the clamp slot to re-enter the insulating operating rod by rotating circumferentially and achieves separation［5］.The shape of the slot of the insulating operating rod is different from thatof the slot in the interface of the clamp rod，and one end of the slot is in the shape of a barb.Therefore，when the locking block rotates counterclockwise，it cannot get out of the slot，as shown in Fig.4（b）.The slot of this shape limits the circumferentialmovement of the clamp block in the counterclockwise direction.Only when the clamp block rotates clockwise can it get out of the slot.

4 Detailed structural design of the device

4.1 Design of wire terminal clamp

As shown in Fig.5，the wire terminal clamp adopts the existing product.On the basis of the product，a bolt interface is added at the end，which is used for threaded connection with the clamp rod to the interface.The interface uses studs.One end is connected to the wire terminal clamp and the other end is connected to the clamp rod interface.

Fig.5 Term ina Ic Iam p of w ire

4.2 Structure design of clamp rod interface

The clamp rod interface consists of a pair of nozzles and an internal spring assembly.The shape of the pair of nozzles is shown in Fig.6.It is a rotating body structure，with a conical structure containing a large angle at one end，used for connecting with the insulating operating rod，and the other end is a straight pipe hole，and the end is an internal thread，which is connected with the end of the wire clip at the wire end.The inner part of the pipe is divided into three areas，which are distinguished by different inner diameters.They are respectively used to place the spring，the spring pushing the block and toform the arc clamp groove with symmetrical distribution，which is used to match the insulating clamp block in the insulating operating rod.

Fig.6 The three-dim ensiona Istructure of the pipe

The spring assembly inside the clamp rod interface includes a compression spring and a push block，as shown in Fig.7.One end of the compression spring is in contactwith the threaded end of the wire clip，and the other end is in contactwith the spring push block.

Fig.7 Assemb Iy diagram of c Iam p rod interface

The spring push block is a rotating body，containing two diameters.The small diameter is inserted into the compression spring，and the large diameter end face is used to withstand the thrust.It is located in the inner pipe，and its axialmovement displacement is limited by the pipe wall diameter，so that itwill not be ejected by the spring elastic force.

4.3 Structure design of insulated operating rod

The insulating operating rod includes an insulating rod and a locking device.The overall structure of the insulating operating rod is shown in Fig.8.The insulating operating rod is a rotating body，which is divided into two different diameters.The small diameter is the joint，and the length is100mm.The large diameter pipe is a pipewith a length of900mm.The end of the pipe is a hollow circular pipe，and the inside is equipped with an arc-shaped slot for connecting with other insulating operating rods.

Fig.8 Structure d raw ing of insu Iated operating rod

The clamping device on the insulating operating rod is composed of a clamp block，a compression spring and a shell.As shown in Fig.9.A pass-way is arranged in themiddle of the shell to place the compression spring and the locking clamp block.The upper end face of the clamp block is provided with a boss，which limits the displacement of the locking clamp block by contacting with the upper end face of the housing pass-way to prevent the locking clamp block from being ejected under the action of the pre-tightening force of the spring.

Fig.9 Structure d raw ing of Iocking device

5 Reliability checking of the device

In the state of locking，since the locking force of the whole grounding wire all acts on the clamp block，when the high voltage wire is clamped and removed by wire clip，great axial force will be generated.When the clamp block is subjected to plastic deformation，it will be unable to enter the clamp slot，unable to complete the locking，or the clamp block will have a gap between the clamping state and the clamping slot，resulting in loose locking.Therefore，to ensure the reliability of the device，strength checking of the clamp block and the deformation caused by the pressure of the clamp block on the contact surface between the clamp slot and the clamp block should be calculated and checked［6］.

When the clamp block is subjected to axial force，the force state of the clamp block can be equivalent to the cantilever beam，and the force acts vertically on the contact surface between the clamp block and the clamp slot.The reliability of the clamp block can be determined by calculating its axial deformation.Firstly，through softwaremodeling，themaximum stressed section area of the clamp block is 20.1 mm2，as shown in Fig.10.

Fig.10 Fo rce area of the b Iock

Since the axial force value in the specific working statewas unknown，multiple pressure values should be selected in the analysis，and finally the pressure curve was simulated to analyze the deformation curve of the corresponding block.The constraint surface and constraint conditions are shown in Fig.11 and Fig.12，and the loaded pressure load is set as shown in Fig.13.

The pressure parameters were set as shown in table 1.

According to the pressure formula：

The stress value corresponding to the set pressure can be obtained by substituting the stressed area and pressure value，as shown in table 2.

Fig.11 Constraint surface of the b Iock

Fig.12 Constraint condition

Fig.13 Pressure Ioad setting

Tab Ie 1 Pressu re param eter tab Ie

Tab Ie 2 Pressure va Iue

The above force value parameterswere used to simulate the stress curve，as shown in Fig.14.The curve was substituted into the finite element analysis to calculate the deformation and safety factor corresponding to each point on the curve.

Fig.14 Curve of app Iied force

According to the actualworking condition，the axial force applied in the working process does not exceed 35 N，so the set analysis parameter is deemed to be credible here［7］.

The analysis results are shown in Fig.15，Fig.16 and Fig.17.

Fig.15 BIock strain nephog ram

Fig.16 CIam p b Iock safety factor

Fig.17 CIam p b Iock stress deform ation

As can be seen from the figure，the maximum deformation of the clamp block is at its end under stress.When the pressure ismaximum，themaximum deformation is 0.000 6 mm and the safety factor is greater than 6.5.Since the actual working stress is less than the design stress value during the analysis，it can be considered that the analysis is reliable，that is，the structure size of the clamp blockmeets theworking requirements of the device.

6 Conclusion

The design of the device focuses on three aspects：the structural design of quick assembly and disassembly joints，the general use of the rod body and the application of connection reliability in the device.Through the organic integration of the high pressure jaw and the quick joint，the quick disassembly and assembly operation of the joint can be realized without multi-turn rotation and other auxiliary tools.The unified design of the operating rod and the quick joint，and the integration of themulti-bar locking connection design mode，can realize the combined application scenarios of different heights，effectively reduce the type of operating rod，reduce the risk of error，and facilitate the field carrying and connection operation.Built-in energy storage spring of the joint can provide automatic ejection and indentability during dis-assembly and assembly，so as to realize a reliable connection without gap and provide a stable operation feel even inmulti-bar operation.The left-handed and righthanded operation modes reduce the difficulty of highaltitude work，effectively improve work efficiency and reduce labor intensity.Through theoretical calculation and finite element analysis，the strength of the device conforms to the technical requirements，and the device is feasible，which can avoid the complicated installation and disassembly of the current grounding wire，large working strength，weak connection and easy tofall off.Therefore，the design value is high，with strong market competitiveness.The device has been applied in the state grid tonghua power supply company（including agricultural power system），the application of the device shorten the time of assembly and disassembly of grounding line for power failure maintenance，improve the work efficiency，reduce labor costs，reduce the labor intensity of operation，improve the quality of grounding line connection，and bring good economic and social benefits.