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BS 148:2020 pdf download

BS 148:2020 pdf download.Recycled mineral insulating oil for transformers and switch gear —Specification.
A.1 Water content
A low water Content of mineral Insulating oil Is necessary to achieve adequate breakdown voltage and low dissipation losses. To avoid separation of free water, recycled mineral insulating oil should have limited water content, Before filling the electrical equipment, the oil should be treated to meet the requirements of BS EN 64)422.
A.2 Acidity
Mineral insulating oil produces acids and other oxidation by-products when in service. These should be removed from the oil to an acceptable level by a recycling process before it can be reused In electrical equipment to achieve suitable resistance to oxidation
A.3 Anti—oxidants
Antioxidants in inhibited oil slow down the oxidation of oil and therefore the Formation of degradation products such as acidity and other oxidation by-products, It Is necessary to know the concentration of antioxidants for the correct classification of the oil. Additionally, periodic measurement of the concentration is required to prevent premature ageing of the oil.
Antl-oxldants Include:
a) inhibitors such as phenols and amines. The most widely used inhibitors are di-tert-butyl-para-cresol (DBPC) and di-tert-butyl-phenol (DBP). Standard test methods are not available for other types of inhibitors, and
b) other antioxidant additives such as sulfur- and phosphor-containing compounds. e.g organic polysullldes and dithiophosphates. An antioxidant additive of this type is dibenzyl dlsulfide I)I3DS. DuDS should not be present in recyded oils as it is known to be corrosive to copper and can generate copper sulfide in service in electrical equipment.
A.4 Gassing tendency
The gas absorbing property of oil when subjected to corona partial discharges is only necessary and important for special equipment like llV (high voltage) Instrument transformers and bushings. It Is a measure of the rate of absorption or evolution of hydrogen into oil under prescnbed laboratory conditions. Gas absorption properties could be related to oil aromatic content.
NUTE Adthtñs such us 1,2.3,4 tetrohydronaphthakne (tetnhlin), mono or dabenzyltohaes’ie and others have been proposed to reduce the gassing tendency of some oils, but ore noe dewri bed in 8S EN 60666 Mono and dlbenzylto?uene are described In 8S EN 60867.
A.5 Polycyclic aromatic hydrocarbon (PCAs) content
Sortie PCA.s are classified to be carcinogens and therefore need to be controlled to an acceptable level in mineral insulating oil. Suppliers are therefore required to demonstrate the non-carcinogenicity of their products.
A.6 Polychiorinated biphenyl content (PCBs)
PCBs are sometimes found as residual contamination in used oil. They are subject to regulation; recycled mineral insulating oil should be Iree from PCBs.
NOTE Accrpwbk limUs of total or indh,Idual PCBs ore specified I,, national and local regulations Further European specifwotons are described in PCB Council Dtrectwe %/59/EC ii).
A.7 Furfural (2-FAL) and related compounds content
2-FAL and related compounds in recycled oil can result from improper redistillation after solvent extraction, From cellulose degradation within equipment that previously contained the oil or from contamination with used oil.
Recycled mineral Insulating oils should have a non-detectable level of 2-FAL. and related compounds.
a) The related compounds are: S-hydroxymethyl-2-furfural (SH MF). 2-lurfurylalcohol (2F01), 2-acetylfuran (2ACF) and 5-methyl-2-furfural (SMEF).
b) Trace levels of furanic compounds might be detectable in recycled oil using modilicd methods in accordance with 1L61198. The limIt 010.05 ingfkg should still be applied.
A.8 Appearance
Appearance may be evaluated by examining a representative sample of the oil in transmitted light under an oil depth olapproxirnately 100 mm and at ambient temperature. Under these conditions, the requirements of 1abIe 1 may be met
A.9 Density
Density can be measured by any recognized test method or. in the event ola dispute, the method
given In BS EN ISO 3675 should be used. Density may be measured at 20°C or converted to 20°C
using Table 59 D of Petroleum measurement paper No.3 121.

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