5.2.1 Insulating Shield Cover
The insulating shield cover is arranged between the operator and the shielded object to prevent the operator from coming into direct contact with the electrified body and play the protective role in shielding or isolation.
1.Basic Structure and Function of Insulating Shield Cover
The following is a brief introduction of the insulating shield cover for live working of 10kV distribution line(hereinafter referred to as the shield cover).
(1)Basic structure
①The shield cover is made of insulating materials such as epoxy resin material,rubber material,plastic material and polymeric material.
②The shield cover may be hard-shelled or soft-sheathed,shall be suitable for the shielded object,and shall have the function of preventing the human body from directly contacting the electrified body or the grounding body,with its length no more than 1.5m generally.In addition to meeting the necessary electrical characteristics,the dimensions shall be minimized.
③The protected area of the shield cover shall be clearly,obviously and firmly marked.
④All shield covers shall be provided with insulating rods,and shall be provided with lifting rings,holes,hooks and other components.The insulating shield cover is shown in Fig.5-16.
Fig.5-16 Sample Drawing of Insulating Shield Cover
(a)Hard falling fuse insulating shield cover;(b)Soft falling fuse insulating shield cover;(c)Pin insulator insulating shield cover;(d)Cross arm insulating shield cover;(e)Pole insulating shield cover
(2)Basic function
In live working of 10kV distribution line,the shield cover does not play the main insulation role,and it is only suitable for insulation and shielding or isolation protection when the live working personnel are accidentally and briefly collided with each other,that is,when they are in contact with each other.
2.Classification and Technical Specifications of Insulating Shield Cover
(1)Classification
①According to the different shielded objects,it can be divided into hard shell type,soft type or deformed type,and can also be divided into fixed type or flat type.
②According to the use of the shield cover,it can be divided into conductor shield cover,pin insulator shield cover,strain device shield cover,hanging device shield cover,cable clamp shield cover,bar insulator shield cover,cross arm shield cover,pole shield cover,sleeve shield cover,falling fuse shield cover,arrester shield cover,etc.It can also be specially designed according to the shielded object.
③There are five kinds of shield covers with special properties:A,H,C,Wand P.
(2)Technical specifications
①The shield cover shall be made of insulating material with small hygroscopicity,and the insulating material shall be able to meet the requirements of electrical and mechanical properties at certain high and low temperatures.
②According to the electrical properties of the shield cover,it can be divided into five grades:0,1,2,3 and 4.
③The main surface of the insulating shield cover shall be smooth,and there shall be no surface defects such as apertures,joint cracks,floating bubbles,crevasses,unknown sundries,abrasion and scratch,and obvious machining marks on its inner and outer surfaces.
④The shield cover shall have lifting ring,barrel hole,hook and other parts in the structure.
⑤One or more locking parts shall be arranged on the shield cover to prevent it from slipping suddenly in use or under the action of external force.
3.Inspection Contents of Insulating Shield Cover(https://www.daowen.com)
In order to ensure the integrity of the electrical and mechanical properties of the shield cover,a careful appearance inspection and trial assembly shall be carried out before each use of the tool,as follows.
(1)The shield cover shall be free from damage after storage and transportation,and the insulating surface of the tool shall be free from holes,bruises,scratches and cracks.
(2)The surface of shield cover shall be clean and dry.
(3)Removable parts or components of the shield cover shall be complete and intact after being assembled.
(4)The shield cover shall be operated correctly,the tool shall rotate flexibly without jamming,and the locking function shall be correct.
4.Usage of Insulating Shield Cover
(1)It is only for live working of power equipment 10kV or below,such as cross arm shield cover and insulator shield cover shown in Fig.5-17.
Fig.5-17 Use of Insulating Shield Cover
(2)The shield cover does not play the role in main insulation,but allows occasional short-term contact,mainly limiting the motion range of human body.
(3)The shield cover shall be used in conjunction with the human body safety protection appliances.
(4)The overlaps between the insulating shield covers or with the edges of other shielding objects during the shielding operation shall not be less than 150mm.
(5)The shielding scope of each shield cover shall not exceed the protection of the shield cover protection area.
5.Precautions for Storage of Insulating Shield Cover
(1)The insulating shield cover can not be folded and squeezed,because crease will cause the rubber to be oxidized,reducing the insulation performance.
(2)The shield cover shall be stored in a properly sized storage bag,packaged in parts and placed flat.
(3)It is prohibited to store the shield cover near the steam pipe,heat dissipation pipe or other artificial heat source and in the environment with direct sunlight,light or other light source.In particular,it shall be avoided to directly touch sharp objects and cause puncture or scratch when being stored or moved.
(4)It is prohibited to contact the shield cover with oil,acid,alkali or other harmful substances,and it shall be kept more than 1m away from the heat source.The storage environment temperature should be 10-21°C.
(5)The damp shield cover shall be thoroughly dried,but the drying temperature shall not exceed 65°C.
6.Test Contents of Insulating Shield Cover
The test contents of the insulating shield cover are as follows.
(1)Mechanical test.The mechanical test of the shield cover shall be done at low temperature.The mechanical property of the shield cover shall include simulated assembly test,low-temperature folding test of the soft insulating shield cover and low-temperature impulse resistance test of the hard insulating shield cover.
(2)Electrical test.It includes power frequency withstand voltage and leakage current test,certification test,ozone resistance test and special property test.
(3)Preventive tests.The preventive test of the insulating shield cover shall be conducted once every six months.