Dr B Pahlavanpour Senior Techncal Co-ordinator Nynas Naphthenics LTD UK

Dr B Pahlavanpour Senior Techncal Co-ordinator Nynas Naphthenics LTD UK

IEC specification and maintenance guide for mineral insulating oil Dr B Pahlavanpour Nynas Naphthenics Ltd UK

Three Important oil related IEC standards IEC60296, Specification for supply of unused MIO IEC60422, Maintenance guide for in-service MIO IEC60599, Interpretation of DGA Although these standards have maintenance cycle but, if required, they can be revised if and when require

Reason for revision During 2005 there was report of some transformer failure due to copper sulphide formation IEC, TC10 meeting in Cape Town decision was to revise these two standard to address this issue, Also to develop a method for detection of potentially corrosive sulphur

Revised IEC60296, 2012 ed Introduction of corrosive sulphur test methods: IEC62535 ASTM D1275B Introduction of IEC60666 test method for: passivator content Test method for antioxidant content to 0.01% Lower level of Furfural in oil (<0.05 ppm) If passivator is detected then oil should tested for 500 hours for oxidation stability test (IEC61125C) Introducing test method for detection of DBDS, limit of <5 ppm IEC62697 Nynas- 2012 5 2013-05-

Nynas- 2012 6 2013-05-

Table 2 General specification No changes to 2003 ed Nynas- 2012 7 2013-05-

Nynas- 2012 8 2013-05-

Nynas- 2012 9 2013-05-

1 Nynas- 2012 0 2013-05-

Special requirement for special application (high grade oil) 1 Nynas- 2012 1 2013-05-

IEC 60422 Oil maintenance guide A tool for keeping the oil in good condition Oil tests divided into 3 groups Routine Complementary Special investigative Different recommended property limits depending on voltage class (also type of equipment) < 72.5 kv 72.5-170 kv < 170 kv For each measured property 3 levels of assessment Good No action Fair More frequent sampling Poor Action required

Revision of IEC60422 Originally was to address potentially corrosive sulphur in oil First meeting January 2007 Report to TC10 Test the oil for presence of corrosive sulphur, corrective actions recommended (i.e change the oil, passivate the oil) MT22 members take the opportunity to revise IEC60422 and IEC central office agreed with this proposal. To bring it in line with current practice in industry, and address industries need.

Main changes Moisture content Inhibitor content Passsivator content DBDS content Potentially Corrosive Sulphur

Water content 2005 ed. corrected to 20 ºC then limit for each category of equipment FDIS, at transformer operating temperature together with breakdown voltage. Consequently higher limits are used Correction to 20 ºC is transferred to annex (informative).

2005 ed Water content (mg/kg at transformer operating temperature) O, A <15 15 to 20 >20 B, D <20 20 to 30 >30 C, E <30 30 to 40 >40 F G Action necessit y >40 Not a routine test. 2013 ed

Inhibitor content 2005 ed Category Recommended Action Limits 2013 ed All Good Fair Poor >60 % of original value 40 % to 60 % of original value <40 % of original value

Passivator content (new) O, A, B, C, D, E, F >70 and stable, (rate of decrease <10mg/kg/year) 50-70 mg/kg or <70 mg/kg, with a significant rate of decrease of >10mg/kg/year <50 and decreasing at >10mg/kg/year

Interfacial tension 2005 ed 2013 ed O, A, B, C, D Inhibited Uninhibited E >28 >25 22 to 28 20 to 25 Not a routine test. F, G Not applicable. <22 <20

Corrosive sulphur Three corrosive sulphur test are recommended Introducing new test IEC62535 ASTM D1275B DIN51353 Category Recommended Action Limits Recommended Action Good Fair Poor (1) (2) O, A, B, C, D, E, F Non corrosive Corrosive For corrosive oil: - conduct risk assessment - reduce the corrosivity of the oil by adding a copper passivator (e.g. triazole derivates) or - remove the source of corrosivity by changing the oil [see 12] or by removing corrosive compounds by mean of suitable oil treatments. See NOTE 3.

Passivator content, test method IEC60666, annex B O, A, B, C, D, E, F >70 and stable, (rate of decrease <10mg/kg /year) 50-70 mg/kg or <70 mg/kg, with a significan t rate of decrease of >10mg/kg /year <50 and decreasin g at >10mg/kg /year Good: less frequent monitoring acceptable. Fair: maintain regular monitoring. Poor: remove the source of corrosivity by changing the oil [see 12] or by removing corrosive compounds by mean of suitable oil treatments, or as a short-term solution, top up with new passivator, to at least 100mg/kg [see 13].

DBDS content IEC62697-1 is introduce as test method. No limit for in-service oil as good, fair, bad Reference to CIGRE Brochure 378 is made

IEC60422, 205 ed.

Table of 2013 ed. Appearance Property Highest voltage for equipment (kv) <72,5 72,5 to 170 >170 Clear, free from sediment and suspended matter Colour (on scale given in ISO 2049) Max. 2,0 Max 2,0 Max. 2,0 Breakdown voltage (kv) >55 >60 >60 Water content (mg/kg) a 20 b <10 <10 Acidity (mg KOH/g) Max. 0,03 Max. 0,03 Max. 0,03 Dielectric dissipation factor at 90 C and 40 Hz to 60 Hz c Max. 0,015 Max. 0,015 Max. 0,010 Resistivity at 90 C (G.m) Min. 60 Min. 60 Min. 60 Corrosive sulphur Non-corrosive DBDS content (mg/kg) <5 Interfacial tension (mn/m) Min. 35 Min. 35 Min. 35 Total PCB content (mg/kg) Not detectable (< 2 mg/kg total) Particles - - See Table 9 d

Compatibility The following functional tests are recommended for each individual oil and for the mixture: Foaming Oxidation stability according to IEC 61125 C, including acidity, sludge and DDF after ageing. Test time should be according to the oil group as stated in IEC 60296 Corrosive sulphur and/or potential corrosivity after ageing according to IEC 61125C