2.1.1 Insulator Clamp
The main tools used for live replacement of insulators are clamps,leading screws,insulating pulling plates,hanging hooks,insulating bars,etc.Among them,insulator clamps are the most important tools and instruments for replacing insulators in live working of transmission lines.When replacing,first install the clamps at the cross arm position of the insulator string hanging point,tighten the conductor through the leading screw and the insulating pulling plate to loosen the insulator string,and replace the insulator with the insulating bar.
According to different tower types,insulator string types and hardware types,the most commonly used insulator clamps for live replacement of insulator of power transmission line include wing-shaped clamp,broadsword clamp and closed clamp.These three types of insulator clamps will be detailed herein.
1.Basic Structure,Function and Usage of Common Insulator Clamps
(1)Airfoil clamp
①Basic structure
The clamps assembled on the conductor end of the insulator string are called the front clamps,and the clamps assembled on the cross arm end of the insulator string are called the rear clamps,as shown in Fig.2-1.
Fig.2-1 Wing-shaped Clamp Structure Drawing
1-front clamp;2-rear clamp;3-screw rod
②Basic function
Mainly used for live replacement of single tension insulator string.During operation,it is necessary to fix the fittings on both sides of the insulator string with clamps and tighten the conductor through lead screw and insulating pulling plate,so that the insulator string can be relaxed on the insulator cradle for replacement(silicone rubber composite insulator is not suitable for the insulator cradle).
③Usage
Before the electrician climbs up the tower,the ground electrician shall first assemble the insulator clamp,the leading screw and the insulating pulling plate.After the operator on the tower arrives at the designated position,the assembled wing-shaped clamp,the insulator cradle and the operating rod are successively transferred to the tower.
No.1 electrician holds the clamp,and No.2 electrician holds the insulating bar.They cooperate with each other to fix the front clamp of the wing-shaped clamp to the lowest position of the bolt-type strain clamp,as shown in Fig.2-2.Locking device that prevents the clamp from sliding down is locked,as shown in Fig.2-3.Fix the cross arm side clamp on the cross arm and insulator string insulator set fitting,and confirm that the fitting is properly embedded in the slot,as shown in Fig.2-4.During the installation process,the body part of the No.1 electrician shall not be beyond the first insulator.
Fig.2-2 Laying the Wing-shaped Clamp
Fig.2-3 Installing the Front Clamp and Locking It up
Fig.2-4 Installation of the Rear Clamp
Fig.2-5 Installation of Insulator Cradle
The No.2 electrician holds the insulating bar and cooperates with the No.1 electrician to insert the insulating tube of the insulated insulator cradle into the conductor side support frame,and the triangular supporting structure of the insulated insulator cradle is connected with the cross arm side clamp and the bolt is tightened.Before installing the insulated insulator cradle,adjust the height of the conductor side support frame so that the insulating tube of the insulator cradle can be parallel and close to the insulator string.After installation,check whether the two insulating tubes of the insulator cradle are inserted into the conductor support frame,as shown in Fig.2-5.
The No.1 electrician performs impact test on the insulator string and the clamp,tightens the leading screw and performs impact test on the stringing tool.When the leading screw is tightened,the stress of the leading screws on both sides shall be balanced and the tightening length shall be about the same.When the leading screw is shaken,the force shall be even,and the twisting amplitude of the insulating pulling plate shall be minimized.
(2)Broadsword clamp
①Basic structure
Broadsword clamp installed at the conductor end of the insulator string is called front clamp whose top is provided with a lifting pulley,and the one assembled at the cross arm end of the insulator string is called rear clamp,as shown in Fig.2-6.When the broadsword clamp is used,a pulling plate,aleading screw,etc.are also needed,as shown in Fig.2-7.
Fig.2-6 Broadsword Clamp
1-front clamp;2-rear clamp;3-lifting pulley
Fig.2-7 Assembled Broadsword Clamp
1-insulating pulling plate;2-leading screw
②Basic functions
Method:It is mainly used for replacing tension duplex insulator string with the ground potential operation method.
③Usage
The ground electrician shall first assemble the broadsword clamp,the leading screw and the insulating pulling plate,and adjust the distance between the leading screw and the insulating pulling plate,and the connection of each part is firm and reliable.After the operator on the tower arrives at the designated position,the assembled broadsword clamp,the insulator cradle and the operating rod are successively transferred to the tower.
The No.1 electrician holds the insulating pulling plate and the clamp,and the No.2 electrician holds the insulating bar,and they cooperate with each other to fix the front clamp of the broadsword clamp to the conductor side yoke plate for 2-bundle conductors,and fix the rear clamp of the broadsword clamp on the cross arm side yoke plate for 2-bundle conductors.When installing the front clamp of the broadsword clamp,check that the clamp is inserted in place,as shown in Fig.2-8.When installing the rear clamp of the broadsword clamp,check that the pin is inserted in place and locked,as shown in Fig.2-9.During the installation process,the body part of the No.1 electrician shall not be beyond the first insulator.
Fig.2-8 Installation of the Front Clamp of the Broadsword Clamp
Fig.2-9 Installation of the Rear Clamp of the Broadsword Clamp
After adjusting the leading screw and making the stringing device slightly stressed,the No.2 electrician holds the insulating bar and cooperates with the No.1 electrician to insert the insulating tube of the insulated insulator cradle into the conductor side support frame,and the triangular supporting structure of the insulated insulator cradle is connected with the rear clamp of the broadsword clamp and the bolt is tightened,as shown in Fig.2-10.Before installing the insulated insulator cradle,adjust the height of the conductor side support frame so that the insulating tube of the insulator cradle can be parallel and close to the insulator string,and fix the front clam,as shown in Fig.2-11.After installation,check whether the two insulating tubes of the insulator cradle are inserted into the conductor support frame.When installing the triangular supporting structure of the insulator cradle,the No.1 electrician shall pay attention to the safe distance between the hand and the foot and the jumper wire under the cross arm for 1.8m and above.
After the tool is assembled,the No.1 electrician performs an impact test on the insulator string and the clamp.Finally,the No.1 electrician tightens the leading screw at a constant speed to loosen the insulator string.
Fig.2-10 Installation of Insulator Cradle
Fig.2-11 Fixing the front clamp and installing the insulator cradle
(3)Closed clamp
①Basic structure
Closed clamp includes front clamp movable cover,front clamp bolt,rear clamp movable cover,rear clamp bolt,etc.,as shown in Fig.2-12.When using a closed clamp,you need to tighten the leading screw,as shown in Fig.2-13.
②Basic functions
It is suitable for replacing conductor at the side of tension string conductor by the equipotential working method.
③Usage
Fig.2-12 Closed Clamp
1-movable cover;2-bolt(https://www.daowen.com)
Fig.2-13 Assembled Closed Clamp
1-front clamp;2-rear clamp;3-tightening the leading screw;4-crankshaft
A.In the case of a porcelain insulator string,the ground electrician transmits the spark gap detector to the equipotential electrician,and the equipotential electrician detects the insulator to determine whether the number of good insulator pieces required for the operation is satisfied.
B.The equipotential electrician fastens a safety belt and an anti-fall rope,carries the insulated transmission rope and enters the operation point along the insulator string.When entering the potential,grasp the work string with the two hands,and step on the non-work string with the two feet.Move by the"two-span and three-short-circuit"method.
C.The ground electrician transfers the assembled closed clamp to the equipotential electrician's work position.
D.The equipotential electrician installs the closed clamp on the adjacent two steel caps of the replaced insulator,as shown in Fig.2-14.
Fig.2-14 Installation of Closed Clamp
Fig.2-15 Removing the Insulator
E.The equipotential electrician tightens the leading screw to make it slightly stressed.After checking and confirming that there is no abnormality in the force,remove the fitting pins on both sides of the replaced insulator.Continue to balance the tightening of the leading screw to remove the insulator,as shown in Fig.2-15.
2.Classification,Technical Parameters and Precautions for Use of Insulator Clamps
(1)Classification
①Clamps can be classified as the following series:tension string clamps,linear string clamps and monolithic insulator clamps according to the function.The codes are indicated as follows:
"N"-Tension string clamp;
"Z"-Linear string clamp;
"D"-Monolithic insulator clamp.
Tension string clamp is used to replace clamp of tension insulator and hardware,which can be classified as airfoil clamp,broadsword clamp,turning plate clamp,bending plate clamp,oblique card,etc.according to its structure shape.Linear string clamp is used to replace clamp of linear insulator and hardware which can be classified as V-shaped string clamp,bracket clamp,flower-shaped clamp,linear hook clamp,hook plate clamp,etc.according to its structure shape.Monolithic insulator clamp is used to replace clamp of monolithic insulator,which can be classified as closed clamp,end clamp,etc.according to its structure shape.
②Clamp is identified by the first letter of its name in Chinese Pinyin plus"K"according to its structure style.For example:"wing-shaped clamp"is identified as"YK",and"broadsword clamp"is identified as"DK".
(2)Technical Parameters
The general rated load value of clamp is:
Where:P represents the rated load of the clamp,kN;P0 is the applicable insulator or fitting grade,kN.
①Performance parameters of strain insulator string clamps
See Table 2-1 for specifications and technical parameters of tension string clamp.
Table 2-1 Specifications and Technical Parameters of Tension String Clamp
Table(Cont'd)
②Technical parameters for linear string clamps
See Table 2-2 for specifications and technical parameters of tension string clamp.
Table 2-2 Specifications and Technical Parameters of Linear String Clamp
③Technical parameters for monolithic insulator clamps
See Table 2-3 for specifications and technical parameters of monolithic insulator clamps.
Table 2-3 Specifications and Technical Parameters of Monolithic Insulator Clamp
(3)Precautions for use
①When the clamp is selected,the maximum actual working load shall be checked.If there are special requirements or adverse weather conditions that may cause the working load to exceed the rated load of clamp,the clamp with higher specification shall be selected.
②The appearance of the clamp shall be inspected before use,and the clamp shall not be used if any crack is found.Collision shall be avoided during transportation,and it is not allowed to knock and fall hard in use to avoid affecting its mechanical and working performance.
③The contact surface between the clamp and the hanging point shall be closely and reliably matched,and the non-contact surface shall have a gap of 1-2mm,so as to facilitate the installation or disassembly of the clamp.
④All parts of the clamp shall have smooth and flat surface without burr,sharp edge,crack and other defects.
3.Inspection Items of Insulator Clamps
The insulator clamp must be inspected before use as follows.
(1)All parts of the clamp shall have smooth and flat surface without burr,sharp edge,crack and other defects.
(2)Dimensional tolerances,shape tolerances,and overall dimensions of each part of the clamps shall comply with the design drawings.
(3)The raw materials used in the main body of the clamps and other major parts must be re-inspected for chemical composition and mechanical properties before use.The aluminum alloy material shall also be re-inspected for macrostructure.
(4)The clamp shall be fitted with the hanging point to ensure that it is reliable and easy to handle.
4.Precautions for Storage of Insulator Clamps
(1)The insulator clamps shall be kept in a dry and well-ventilated tools and instruments warehouse,stored in a special tools and instruments box or placed at the fixed point of the shelf.The tool cabinet for storing the insulator clamps is shown in Fig.2-16.
(2)The clamp label shall be provided on an easily identifiable part by imprinting or other methods,and the indentation depth shall not exceed 0.1mm.
(3)The label includes the model specification of the clamps,the name of the manufacturer or the code name,trademark,and factory number.
Fig.2-16 Storage Cabinet for Insulator Clamps
5.Preventive Test for Insulator Clamps
For preventive tests,static load test and dynamic load test shall be carried out on the insulator clamps as required,and the test cycle is 1 year.