BS_6522-1984.pdf

BS6522:1984ContentsPageCommittees responsibleInside front coverForeword1Scope12Principle13Apparatus14Sample preparation15Procedure16Calculation of results27Precision2Figure 1-Arrangement of equipment for the measurementof dew-point3Publications referred toInside back coveroBSI11-1999iBS6522:1984ForewordThis British Standard has been prepared under the direction of the GeneralElectrotechnical Engineering Standards Committee.The degradation of cellulosic materials used in oil filled equipment such astransformers is affected by their water content.This can only be estimated froma measurement of the water content of the oil.The presence of water alsoadversely affects the electrical insulating properties of the oil and cellulose,andit is therefore desirable to maintain the water content at a low level.The determination of absolute water content in insulating oil has in recent yearsgenerally been carried out by the Karl Fischer method.This determinationrequires considerable care and skill and may present additional difficulties ifcarried out on site.Moreover,the information obtained has to be interpreted inthe light of experience;a moderate water content may suggest potential troublewith an unoxidized oil but may be innocuous when found in an oxidized oil.The method described in this standard determines the percentage saturation ofthe oil rather than its absolute water content.If the percentage saturation of asample of oil from a transformer is determined at,say,three temperatures,thiswill enable a curve to be drawn,using extrapolation if necessary,showing thepercentage saturation as a function of oil temperature over the range oftemperatures found in the oil of that transformer in operation.This immediatelyreveals whether water condensation is likely,i.e.whether 100 saturation maybe approached;such conditions may arise at the coldest regions of the oil,e.g.inthe conservator.This information is independent of the age or state of the oil.In addition,since if oil and cellulose are in water equilibrium and at the sametemperature their percentage saturations are approximately equal,the curveproduced as described above,showing percentage saturation against temperaturefor the oil,may be regarded as applying also to the paper,etc.in the transformerover the range of temperature found in the paper.While this application to thepaper is subject to several sources of error,the indication of paper condition sogiven is much more revealing than can possibly be obtained from an absolutewater determination by the Karl Fischer method.NOTE It has been assumed in the drafting of this British Standard that all users of this standardwill,if not themselves fully trained,at least be under the supervision of a responsible trained personwho will be familiar with all normal laboratory practice and engineering practice as appropriate andsafety precautions,and that all such precautions will be observed.A British Standard does not purport to include all the necessary provisions of acontract.Users of British Standards are responsible for their correct applicationCompliance with a British Standard does not of itself confer immunityfrom legal obligations.Summary of pagesThis document comprises a front cover,an inside front cover,pages i and ii,pages 1 to 4,an inside back cover and a back cover.This standard has been updated(see copyright date)and may have hadamendments incorporated.This will be indicated in the amendment table on theinside front cover.BSI11-1999