5.2.3 Insulating Blanket
1.Basic Structure and Function of Insulating Blanket
(1)Basic structure
①The shape of the insulating blanket can be flat,slotted or specially designed to meet the needs of special use.Flat insulating blanket is shown in Fig.5-20 and Fig.5-21,while slotted insulating blanket is shown in Fig.5-22.
Fig.5-20 Flat Resin Insulating Blanket
Fig.5-21 Flat Rubber Insulating Blanket
Fig.5-22 Slotted Rubber Insulating Blanket
②The insulating blanket is generally made of epoxy resin,rubber and other insulating materials.
(2)Basic function
①The insulating blanket shall have very high insulation property,good corrosion resistance and high heat resistance,and play the role in temporary insulation and protection of electric operators from mistakenly touching the electrified body and isolating the electrified parts during live working,and improving the insulation level of adjacent phases.
②It has stable withstand voltage and the functions of blocking electric arc,voltage and partial current.
2.Classification and Technical Specifications of Insulating Blank
(1)Classification
①The insulating blanket is divided into resin insulating blanket and rubber insulating blanket.
②The insulating blanket with special properties and multiple special properties can be divided into 6 types:A,H,Z,M,S and C.
(2)Technical specifications
①The insulating blanket is divided into four grades:0,1,2 and 3 according to its electrical properties.
②The insulating blanket shall be made of insulating rubber and plastic materials in seamless manufacturing technology.The edge of perforations in the insulating blanket must be reinforced with a non-metallic material,usually 8 mm in diameter.(https://www.daowen.com)
③There shall be no harmful irregularities on the upper and lower surfaces of the insulating blanket,and the protection area of the insulating blanket shall be clearly,obviously and firmly marked.
3.Inspection Contents of Insulating Blanket
In order to ensure the integrity of the electrical and mechanical properties of the insulating blanket,its both sides shall be carefully inspected before each use.Its appearance and surface shall be flat and smooth,uniform in color,free from impurities,pinholes,cracks,cutting and other obvious defects;the surface of the insulating blanket shall be clean and dry;the insulating blanket shall have a test certificate within the test time limit.
4.Usage of Insulating Blanket
(1)It is only for live working of power equipment 10kV or below,as shown in Fig.5-23.
Fig.5-23 Use of Insulating Blanket
(2)It does not play the role in main insulation,but occasional short-term contact is allowed,and it shall be used in conjunction with the human body safety protection appliances.
(3)The isolation scope of each insulating blanket shall not exceed the protection of the protected area.
(4)After the insulating blanket is installed,it shall be securely fixed with the insulating blanket clip.
(5)The overlaps between the insulating blankets or with the edges of other shielding objects during the shielding operation shall not be less than 150mm.
5.Precautions for Storage of Insulating Blanket
(1)The insulating blankets shall be stored one by one in packing bags of sufficient strength.The insulating blanket shall be carefully placed to ensure that it is not squeezed and folded,especially to avoid direct contact with sharp objects,resulting puncture or scratching.It is prohibited to store it near steam pipe,heat dissipation pipe or other artificial heat source,and it shall be kept more than 1m away from the heat source.It is prohibited to store it in the environment with direct sunlight,light or other light source;no contact with oil,acid,alkali or other harmful substances is allowed.The storage ambient temperature should be between 10°C and 21°C.
(2)The damp insulating blanket shall be dried,but the drying temperature shall not exceed 65°C.
6.Test Contents of Insulating Blanket
The test contents of the insulating blanket are as follows.
(1)Mechanical test.The mechanical property test of the insulating blanket includes tensile strength and elongation test,mechanical puncture resistance test,tensile permanent deformation test and tear resistance test.
(2)Electrical test.AC voltage test includes AC voltage certification test and AC withstand voltage test.
(3)Preventive tests.The preventive test of the insulating blanket shall be conducted once every six months.