Post on 15-Mar-2018
transcript
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
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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
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Table 2 General specification
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No changes to 2003 ed
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Special requirement for special application
(high grade oil)
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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).
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 Action
necessit
y >40
G Not a routine test.
2005 ed
2013 ed
Inhibitor content
Category Recommended Action Limits
Good Fair Poor
All >60 % of
original
value
40 % to 60
% of
original
value
<40 % of
original value
2005 ed
2013 ed
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
O, A, B, C, D
Inhibited
Uninhibited
>28
>25
22 to 28
20 to 25
<22
<20
E Not a routine test.
F, G Not applicable.
2005 ed
2013 ed
Corrosive sulphur Three corrosive sulphur test are recommended
Introducing new test IEC62535
ASTM D1275B
DIN51353
Category Recommended Action Limits Recommended Action (1) (2)
Good Fair Poor
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.
Property Highest voltage for equipment (kV)
<72,5 72,5 to 170 >170
Appearance 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 20b <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