dga furan analysis

8/9/2019 DGA Furan Analysis

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TRANSFORMER OIL TESTING &

QUALITY

:: Furan Analysis ::

| Slide 1

HGE120025 Ling Wei Zui

HGE120018 Komaleshwari

HGE120023 Shahrizal JelaniHGE120021 Shefian


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| Slide 2


>>Overview


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>>Overview1. Transformer is an important component in the electricity network.2. Transformer insulation consists of the following & the performance of the

transformer itself depends on the integrity of these materials eg. mineral oil,

paper insulation or cellulosic materials i.e pressboard or woods

3. Life of transformer is determined by the life of its paper insulation.

4. Age of the paper insulation is determined by the mechanical strength of thepaper and is measured in terms of its Degree of Polymerisation (DP).

5. Estimating DP from the oil furan concentration in particular is a non-intrusivemethod as it need not take the transformer out of service as it is not possible totake paper samples during running operation.

6. Therefore, the DP value is determined on the basis of cellulose decompositionproducts i. e. furans. These are partly oil-soluble and give some indication ofthe rates of decomposition of the solid insulation.


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>>Introduction (Komal)


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>>Introduction1. Main objective of furan testing is to determine whether the paper in a given

transformer has been or is being damaged by:• Heat• Oxygen• Moisture

2. Furanic compounds found in transformers are solely formed by the degradationof the cellulosic insulation.

3. The causes of paper to degrade from original state could be due to:• Mechanical stresses i.e internal mechanical vibration & designweaknesses reduces the paper insulation mechanical tension

• Electrical stresses i.e high loading, overheating, arching & partialdischarges causes paper insulation to loose its polymerisation integrity

• Environmental i.e high humidity & moisture content in air around the

transformer contributes to cellulose paper insulation deterioration• Type & quality of paper • Type & quality of oil• Operating condition i.e high loading or operation at maximum loading

affects the paper insulation mechanical and chemical strength.


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| Slide 6

>>Introduction

Oil Analysis

MoistureContent

AcidNumber

Dielectric

Strength

PowerFactor

DissolvedGas

Analysis

Furans


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| Slide 7

>>Introduction

Furan derivatives are a measure of the degradation

of cellulose paper. When the paper ages, its degreeof polymerization reduces, so its mechanical strengthdecreases.

The degree of polymerization can only be determineddirectly by taking a sample of paper, a very complexoperation and almost never performed in practice.

However, the degree of polymerization of the papercan be directly related to the concentration of furanderivatives in the oil.


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| Slide 8

>>Introduction

Furan derivate are formed as a direct result of the

breakdown of the polymeric structure of cellulosepaper.

The content of furan derivatives is relatively easy to

measure in the oil, using HPLC and is thus a way ofmeasuring the aging of the paper.


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| Slide 9


>>Types & Properties


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| Slide 10

Furan is a heterocyclic aromatic system consisting of

four carbons and one oxygen in five membered ringwith each of the carbons having a hydrogenattached, hence the molecular formula is C4H4O.

Full Structure Formula Ball-Stick Model Skeletal Formula

>>Types and Properties


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| Slide 11


The five most prevalent derivatives of furan that arise

from the degradation of the cellulose that are solublein the oil to an appreciable degree are the following:

2-Furaldehyde or 2FAL

2-Acetylfuran or 2ACF 5-Methyl-2-Furaldehyde or 5M2F 2-Furfurol or 2FOL 5-Hydroxymethyl-2-Furaldehyde or 5HM2F


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>>Procedure


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Proper Transformer Sampling (ASTM D923)

The ability of insulating oil analysis to provide anearly sign of a problem condition is dependent on thequality of the oil sample that is sent to the lab.

>>Procedure (Sampling)


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| Slide 15


Fluids with specific gravity greater then 1.0 should besampled from the top because free water will float.

For fluids with a specific gravity less than 1.0, such asmineral-based transformer oils, synthetic fluids andsilicone oils, the sample should be taken from thebottom since water will tend to drop to the bottom in

these fluids.



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The ideal situation for collecting a sample from anelectrical apparatus is 95°F (35°C) or higher, zeropercent humidity and no wind.

Cold conditions, or conditions when relative humidity isin excess of 70 percent, should be avoided, as this willincrease moisture in the sample.

Collecting a sample during windy conditions is also notrecommended because dust and debris enter the cleansample easily and disrupt accurate particle counts.


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High-Performance Liquid Chromatography (HPLC) is

a reliable method to perform furan analysis ontransformer oil. The standards are IEC 61198 and ASTM D5837.

Using the High Performance Liquid Chromatography(HPLC) test method, it is prerequisite that the sampleis soluble in a solvent as the measured substancescannot be transferred into the gaseous phase without

decomposition (by contrast to a gaschromatography).

>>Procedure (Analysis)


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| Slide 21

>>Procedure


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IEC 61198: Method for the determination of 2-furfuraland related compounds in mineral insulating oils.

ASTM D5837: Standard test method for furanic

compounds in electrical insulating liquids by High-Performance Liquid Chromatography (HPLC).

10g of oil are solved in 10 ml of pentane for the

measurement. This mixture is drawn through a silicagel column by negative pressure where the polarcellulose elements (furan derivates) accumulate.



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| Slide 25

After that 20 ml of pentane are flushed through the

column to remove all remaining oil components. Afterdrying of the silica gel column in a vacuum, theadsorbed furan derivates are extracted by 10ml ofacentonitrile into a volumentric flask.

After flushing of the chromatograph column theextracted mixture is injected into the sample loop out ofthe volumetric flask and the measurement is started.

The sample is pumped through a column. Dependingon the kind of the furan derivates there is an interactionbetween the derivates and the stationary phase of thecolumn.



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| Slide 26

If there is a strong interaction, the substance remains

relatively long in the column (long retention time). Ifthere is a weak interaction, the respective substancepasses the column quicker (short retention time).

A UV/VIS detector at the end of the column can at thesame time measure the intensity and the kind of thefuran derivates.



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| Slide 27

Calibration solutions are made up for each of the

components to be analyzed and there are used tostandardize the instrument responses.

From the data on the standard solutions, the

extraction efficiencies for each component can becalculated and corrections can be made accordingly.

The results are usually reported in terms of parts per

billion (ppb).

0 – 100 ppb = Acceptable; 101- 1000 ppb = Marginal;Greater than 1000ppb = Unacceptable

>>Procedure


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| Slide 28


>>Case Studies


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Mechanical properties of insulating papercan be established by direct measurement of

its tensile strength or degree ofpolymerization (DP).

DP are used to evaluate the end of reliablelife of paper insulation.

Suggested that DP values of 150-250represent the lower for end-of-life criteria forpaper insulation.

Below 150 the paper is without mechanicalstrength.

Direct measurement of these properties isnot practical for in service transformer.

| Slide 29

>>Direct Evaluation


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Analysis of this paper insulation for its DP value requires

removal of few strips of paper from suspect sites.

This procedure can be carried out during transformer repairs.

This result of this test will be a deciding factor in rebuilding orscrapping a transformer.

Obtain a paper sample usually is not practical and oftendangerous to the transformer from a de-energized.

In service transformer an alternative method has been found.

When a cellulose molecule de-polymerises (breaks into smallerlengths or ring structure), a chemical compound known as afuran is formed.

| Slide 30

>>Analysis of Paper Insulation


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Measuring the quantity and types of furan present in a transformeroil sample, the paper insulation overall DP can be inferred with ahigh degree of confidence.

The types and concentration of furans in an oil sample can also

indicate abnormal stress in a transformer, whether intense, shortduration overheating or prolonged, general overheating.

| Slide 31

>>Furan Analysis


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| Slide 32

Furan Content (ppm) DP Value Significance

0-0.1 1200-700 Healthy transformer

0.1-1.0 700-450 Moderate deterioration

1-10 450-250 Extensive deterioration

>10


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DP RANGE REMARK

900 No detectable paper degradation


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INSULATION FAILURE

The Progression Towards Insulation Failure

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TRANSFORMER DETAILS

Primary Voltage: 11 kV Secondary Voltage: 500VVA Rating: 500 KVA Vector Group: Dyn11

Impedence: 4.1% Tap Changer: Off Load

Make: CAWSE & MALCOLM Conservator: No

Breather Size: CHG2 Oil Volume Litres: 600


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| Slide 36

Spreadsheet of Transformer oil analysis and Maintenance History


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| Slide 37

Paper insulation at End of Life Criteria


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| Slide 38

Substation: POWER STATION NO.2

Transformer No: TE 43 Serial No: 5292 Sample Point: MAIN TANK

Sample Date: 14/01/2006 Analyses Date: 24/01/2006 Primary Voltage: 6.6 kV

Secondary Voltage: 550 V VA Rating: 1500 KVA Vector Group: Dyn11

Dyn11Impedance: 5.41%

Tap Changer: On Load Breather Size: None

Make: JOHNSON &PHILLIPS

Year Manufactured: 1965 Conservator: Yes

Oil Volume Liters: 1967 Report Number: MONDI-105651

TRANSFORMER INSULATING PAPER CONDITION

Furan ppm (mg/L) 9.90 >10 End of life criteria

Predicted Degree of polymersation 218 < 250 End of life criteria

Water in paper: % Dry Weight 3.08 2.0 (max)

Water in paper: Total Litres 7.87


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| Slide 39

Extensive sol id (paper) insulation deterioration


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>>Conclusion• The use of furanic compounds can greatly aid in the

assessment of the condition of the solid paper insulation which

is useful in analysis of incipient fault condition and causes of failures.

• Some of the furanic compounds have sufficient stability in

transformer that they may provide useful information about thelong term aging of the cellulosic insulation.

• Furan analysis enables test to be carried out without affectingthe operation of the transformer

dga furan analysis

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