2024-04-23 23:43:44
Inspection carried out by Inmetro (National Institute of Metrology, Quality and Technology) carried out recently detected irregularities in 14 brands of electrical conductors sold in Brazil. According to the Institute, which establishes conformity assessment programs for various products, samples of wires, cables and cords were collected in five states in the country and the companies were cited and fined.
According to a survey of Qualifio (Brazilian Association for the Quality of Electrical Wires and Cables), at least 70% of the 460 brands of electrical conductors existing in the country are irregular. Between January and October last year alone, the entity carried out 855 tests on electrical wires and cables in the national market and irregularities were found in 66% of the brands.
“Due to the fact that electrical conductors are not visible (they are inside walls, channels, conduits, etc.), many people end up not giving due importance when purchasing. Therefore, saving money is prohibited when purchasing electrical wires and cables, as obtaining products of dubious quality will compromise the functioning and safety of the electrical installation, and problems will arise such as an increase in electrical energy consumption, as well as short-circuits. circuits and even fires”, highlights professor and electrical engineer Hilton Moreno, who is also a technical consultant at COBRECOM.
The professor warns that before purchasing the material it is essential to research its origin, whether the manufacturer is a Qualifio member and also carry out all the technical tests required by the technical standards of ABNT (Brazilian Association of Technical Standards) and also Inmetro.
According to Rosevaldo Toaliari, product and process development supervisor at COBRECOM, the test specifications are in the ABNT standards for each type of cable and Inmetro, through its accredited bodies, tests samples every six months to check whether the cables meet the values specified in the standard. .
“As these are products with compulsory certification, if they meet the requirements of the standard, Inmetro certifies the product and it can be sold by companies”, adds Toaliari.
Main technical tests
Among the essential tests carried out on all lines of electrical wires and cables are dimensional, electrical, chemical and mechanical, all of which must be carried out by the manufacturer.
“Dimensional tests check the diameter of the conductor, the diameter over the insulation and over the cover and the thickness of the insulation and cover, among others; Electrical tests check the voltage that can be supported by the insulation, the electrical resistance and resistivity of the conductive material, in addition to the insulation resistance. Chemical tests include vertical burning, checking insulation crosslinking and conductor aging; and mechanical tests evaluate the elongation of the conductor and the tensile strength, the elongation of the insulation and the hardness of the insulating compounds”, explains Rosevaldo Toaliari.
The professional also emphasizes that the tests are carried out by sampling in 100% of the batches, in which one sample is separated per batch.
“This is to ensure that the cable insulation complies with the standard and that the conductor supports the passage of the specified electric current to the section used without leakage or short circuits in the cables when in operation”, adds Toaliari.
According to Hilton Moreno, other tests must also be carried out by manufacturers of electrical wires and cables, such as: hot deformation of the insulating material; elasticity at low temperatures; thermal shock; and no flame propagation.
Tests are classified as: on samples or special (E); of type (T); and routine (R).
Main types of essays
Hot deformation of the insulating material: checks whether the insulating material adequately withstands high temperatures to which the cable may be subjected during operation, thus avoiding deformations in the material that might lead to the insulation breaking.
Elasticity at low temperatures: checks whether the insulating material adequately withstands low temperatures to which the cable may be subjected during operation, thus avoiding cracks and splits in the material that might lead to loss of insulation.
Thermal shock: checks whether the insulating material adequately supports the heating and cooling cycle to which the cable will be subjected during its operation, thus avoiding damage to the material that might lead to the insulation breaking.
Non-flame propagation: analyzes the degree of flame propagation that the cable presents when subjected to a simulated fire condition. Depending on the result, the cable can be classified as “flame propagating” to “non-flame propagating”.
Test on samples or special (E): is carried out on test specimens of a complete cable or on components removed from a complete cable, with a frequency defined by the manufacturer, with the aim of verifying whether the finished product meets the requirements specified for he.
Type test (T): is carried out before the start of regular manufacturing of a given type of cable, with the purpose of demonstrating the satisfactory design of the product to meet the requirements specified for it.
Routine test (R): is carried out on all shipping units in order to prove the integrity of the cable.
Irregular cables should be avoided
These materials should never be purchased, as they do not comply with ABNT technical standards and/or do not have the mandatory Inmetro certification. Furthermore, this type of material compromises the electrical installation, as low quality products with insufficient dimensions are used in its manufacture.
“These electrical conductors are ‘out of gauge’, as they have less copper than required by technical standards. Furthermore, the copper used often does not have the minimum purity required for electrical purposes, which is 99.99%”, points out Hilton Moreno.
Furthermore, as it is undersized, the product conducts less energy and can result in undue heating of the conductors (overload) and a consequent increase in the electricity bill, as well as short circuits and fires.
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