corrosive sulphur

Involve to Solve Copyrights © 2006 TNB Research

IS IT THE VILLAIN ?

IS IT THE HERO ?

33.2°C

76.9°C

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Transformer Oil Laboratory

Corrosive Sulphur

GOMATHY SETHURAMAN


Sulphur in Transformer Oil

• Unrefined oil may contain : elemental sulphur,

mercapants, sulphide,

disulphide…ext

• Hydro and acid methods are

used during the refinery

process to remove these

sulphur elements.

• Repetition of the refinery

process may remove the

sulphur, but it can never be

zero.

• Sulphur is a natural element contained in crude oil, which is the

basis of transformer oil.

Source: ESI AFRICA Isuues 4, 2005


How to Detect Corrosive Sulphur?

Recommended Test Methods -:

ASTM D1275 – Using Copper Strip

DIN 51353 – Silver Strip

ISO 5662 – Copper Strip

TNBR using ASTM D1275 to detect corrosive sulphur in oil

Methodology – Oil sample is purged with nitrogen and a

clean copper strip is placed in the oil under nitrogen blanket.

Then the oil sample is placed in an oven to age at a high

temperature (≈14oºC) for a period of time (≈ 19 hours). The

copper strip is removed from the oil and visually examined

using a standard chart.



The copper strips from the oil are compared to the

ASTM Copper Strip Corrosion Standard



NONCORROSIVE

• Orange

• Red lavender

• Multicolored with lavender

• Blue or silver or both,

overlaid on claret red, slivery,

brassy or gold,

• Magenta overcast on brassy

strip

• Multicolored with red and

green showing but not grey

CORROSIVE

• Transparent black

• Dark grey

• Dark brown

• Graphite

• Lusterless black

• Glossy

• Jet black


VILLAIN vs HERO Villain Sulphur : -

“ Elemental sulfur and

thermally unstable sulfur

compound in electrical

insulating oil that can cause

corrosion of certain

transformer metals such as

copper and silver…”

ASTM D 2864

Hero Sulphur : -

“ Relatively stable elemental

sulfur that’s left behind after the

refinery stage acts as natural

antioxidant.

These compound exist in the oil,

and are very useful for improving

oil oxidation stability…”


Why is it the Villain ?

Sulphur Elements

• Reacts on contact with copper

• Does not require heat to

promote reaction

• Heat makes the reaction more

pronounce

• May lead to copper sulphide

deposition on insulating

paper, thus weakening the

dielectric strength of the

paper.


RECENT STUDIES CONDUCTED :

• “ There has recently been surprising discovery in small number of

failed transformer and reactors ... deposition of copper corrosion and

copper sulphide…” source Nynas Naphthenics Magazine

• “ Found failure patterns of transformer did not fit the known root

cause… investigation showed that the oil contained elements from

sulphur …” source ESI AFRICA, Issue 4, 2005

• “ Blackened material and foreign deposits were found. Further

investigation showed that the oil contained corrosive element from

sulphur present in the oil…” source ESKOM




Examples of Corrosive Sulphur Related Failures

Source : NETA WORLD 2004,

The Negative Effects of Corrosive Sulfur on

Transformer Components




Source : DOBLE Engineering

The Evolving Problem of Corrosive





Source : ABB

The Evolving Problem of Corrosive



CONCLUSION

• The negative effect pertaining to transformers where

corrosive sulphur is present is a relatively a new

phenomena.

• The effect of corrosive / reactive sulfur not only

adversely affect the internal part of the transformer

but also have drastic effects on insulating materials

such as paper.

• Identifying the sources of sulfur contamination and

being able to monitor concentrations of corrosive and

reactive sulfur will help detect problem areas earlier.

• Therefore, a multifaceted monitoring system should be

in place to avoid failures in the power supply.


Thank You

Contacts:-

Transformer Oil Laboratory

[email protected]

TNB Research Sdn. Bhd.

No. 1, Lorong Ayer Itam,

Kawasan Institusi Penyelidikan,

43000 Kajang, Selangor, MALAYSIA

Tel: +603-89268818 Fax: +603-89223837

corrosive sulphur

Documents

tnb research sulphur

transformer oil unrefined

oil methodology oil

elemental sulphur

hero sulphur

crude oil

sulphur elements

sulphur present