7.1.1 Portable Short Circuit Ground Wire
1.Basic Structure and Function of Portable Short Circuit Grounding Wire
(1)Basic structure
①As shown in Fig.7-1,portable short circuit ground wire is composed of conductor wire clamp,short-circuit wire,bus clamp,ground wire,wiring clip,ground terminal clamp,grounding operating rod,etc.
②wire clamps for conductor terminal and ground terminal are die-cast of high-quality aluminum alloy,and the metal of fasteners matched are nickel plated.
③The grounding operating rod is made of high-grade epoxy resin and glass fiber with excellent insulation performance and mechanical strength.Meanwhile,a silicone rubber sheath is provided at the operating handle to ensure safer and more reliable insulation.
④The short-circuit wire and grounding wire are twisted with multiple strands of high-quality soft copper wires,and are covered with a soft and high-temperature-resistant transparent insulating protective layer,which can prevent the abrasion of the grounding copper wires in use and ensure the safety of operators in operation.
⑤Anew crimping process shall be adopted for the connection nose,bus clamp,grounding copper wire and outer sheath.Soft connection can effectively prevent the copper wire at the connection from breaking during use,thus improving the reliability and service life of the grounding wire.
(2)Basic function
The portable short circuit ground wire can prevent the harm to human body caused by induced voltage generated by adjacent HV electrified equipment,and can also be used for discharging the charge on the conductor in the intense electric field and releasing the residual charge of the power-off equipment.
Fig.7-1 Portable Short Circuit Ground Wire
1-Grounding operating rod;2-Conductor wire clamp;3-Bus clamp;4-Short-circuit wire;5-Wiring clip;6-Ground wire;7-Ground terminal wire clamp
2.Classification and Performance Parameters of Portable Short Circuit Ground Wire
(1)Classification
①According to the use environment,it can be divided into indoor bus-type ground wire(JDX-NL)and outdoor line-type ground wire(JDX-WS).
②According to the voltage grade,it can be divided into 0.4kV,10kV,35kV,110kV,220kV,500kV grounding wires,etc.
③The nominal cross-sectional areas of portable short-circuit grounding wires are:16mm2,25 mm2,35mm2,50mm2,70mm2,95mm2,which can be selected according to voltage grade and rated short-circuit current.
(2)Performance data
See Table 7-1 for performance parameters of 10-110kV portable short circuit ground wire.
Table 7-1 Performance Parameters of 110-110 kV Portable Short Circuit Ground Wire
3.Inspection Contents of Portable Short Circuit Ground Wire
The portable short circuit ground wire must be inspected before use.The inspection contents are as follows.
(1)First of all,check whether the specification of ground wire is consistent with the voltage level of the working line.It is strictly prohibited to use ground wire that does not conform to the specification.
(2)Check whether the portable short circuit ground wire test certificate is within the validity period.
(3)Check the connector of the portable short circuit ground wire(cable clip or wire clamp),which shall be in good contact after installation,and have sufficient clamping force to prevent the wire from being melted due to poor contact in the event of large short-circuit current,or falling off due to electrodynamic force.
(4)Check the connection between the portable short circuit grounding copper wire and the three short-circuited copper wires to see if it is firm.Generally,it shall be tightened by screws and then soldered with tin to prevent fusing due to poor contact.(https://www.daowen.com)
(5)Check whether the plastic sheath of the portable short circuit ground wire soft copper wire is damaged,and whether the soft drawn copper wire is worn and broken.
Fig.7-2 shows the inspection of portable short circuit ground wire.
Fig.7-2 Inspection of Portable Short Circuit Ground Wire
4.Usage of Ground Wire
(1)When in use,the connector of the portable short circuit ground wire(cable clip or wire clamp)shall be in good contact after installation,and have sufficient clamping force to prevent the wire from being melted due to poor contact in the event of large short-circuit current,or falling off due to electrodynamic force.
(2)When the portable short circuit ground wires are used,attention must be paid to the assembling and disassembling sequence.When the ground wires are used,the grounding clip must be connected first,and then the wire clip must be connected,and the contact must be good.The disassembling sequence of portable short circuit ground wires shall be opposite to this.
(3)Installation of portable short circuit ground wire must be carried out by two persons.Insulating gloves shall be worn When the portable short circuit ground wire is installed and removed.
(4)The portable short circuit ground wire shall be inspected thoroughly before each installation.The damaged portable short circuit ground wire shall be repaired or replaced in time.It is forbidden to use the non-conforming conductor as the ground wire or short-circuit wire.
(5)When it is used to release electric charge,the ground wire of the ground terminal must be fixed to the grounding body with a special wire clamp.It is forbidden to perform grounding or short circuit operations by winding.
(6)It is not allowed to connect a disconnector or fuse between the portable short circuit ground wire and the working equipment to prevent the equipment from being not grounded when it is disconnected,causing an electric shock accident to the maintenance personnel.
(7)The maximum swing range of the installed portable short circuit ground wire shall keep a sufficient safe distance from the live part.
5.Precautions for Storage of Portable Short Circuit Ground Wire
(1)Portable short circuit ground wire shall be stored in a well-ventilated and dry environment,and shall be put on the shelf for storage.
(2)Each group of portable short circuit ground wires shall be numbered,and the storage location shall also be numbered.The number of portable short circuit ground wire must be the same as the storage location number,so as to avoid accidents caused by accidental disassembly or missing disassembly of the ground wire during partial interruption maintenance in a complicated system.
Fig.7-3 shows a tool cabinet for storing ground wire.
Fig.7-3 Tool Cabinet for Storage of Ground Wire
6.Preventive Test of Portable Short Circuit Ground Wire
The preventive test of portable short circuit ground wire shall be conducted once a year.The test contents are as follows.
(1)Voltage drop test of grouped portable short circuit ground wire.
(2)Fatigue test of multi-strand flexible conductor.
(3)Grip strength test of wire clip and multi-strand flexible conductor.
(4)Test on over-tightening force of ground wire clamp.
(5)Mechanical strength test of grounding operating rod.
(6)Short circuit current test.