CONDITION MONITORING OF TRANSFORMER

Guided By:-

Prof. Ankit ShahpatelElectrical Engineering Department

G.C.E.T-V.V.NAGAR

Prepared by:-Mehul Makwana

ME (Power system )Enroll.No 130110737020

G.C.E.T-V.V.NAGAR

Co-Guided By:-

Prof. Sameer B PatelElectrical Engineering Department

G.C.E.T-V.V.NAGAR

CONTENTS

• Introduction

• Proposed Methods

• Dissolved Gas Analysis

• Case study on DGA

• Fuzzy Inference System

• References

INTRODUCTION

Transformer is static electrical device

• From the day of This equipment in service, Different stresses like electrical , mechanical, chemical and environmental factor effect the condition of the transformer .

• At the initial stage , Degradation of insulation quality occurs slowly. But this deterioration multiplies in due course of time and leads to final failure of the transformer.

• So, to overcome this situation, continuous monitoring of the condition and preventive measures is required for correct maintenance of the transformer

• The faults like partial discharge , electrical arcs , or hot spots generally deteriorate the condition of transformer in quick progression.

• Hence Early detection of faults is very important for saving transformer from any catastrophic failure.

PROPOSED METHODS

• 1. Dissolve gas analysis• 2.Fuzzy Inference System

Dissolve Gas Analysis• Analysis Dissolved gases-in-oil analysis (DGA) is a common practice in

transformer fault diagnosis. Electrical insulation such as mineral oils and cellulosic materials degrade under excessive thermal and electrical stresses, forming by product gases which can serve as indicators of the type of stress and its severity. Dissolved gas-in-oil concentrations, relative proportion of gases, and gas generation rates (gassing rates) are used to estimate the condition of a transformer. • Commonly used gases include hydrogen (H2), methane (CH4), acetylene (C2H2)

ethylene (C2H4), ethane (C2H6), carbon monoxide (CO), and carbon dioxide (CO2). These gases are extracted from the oil under high vacuum and analyzed by Gas Chromatograph to get each gas concentration separately.

CONT..

• DGA process

Gas Chromatogra

phy

Extraction of all the

gases from Xmer oil

Oil Sampling

Interpretation of gas data

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1. OIL SAMPLING

2. GAS CHROMATOGRAPHY APPARATUS

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METHODS OF INTERPRETATION(IEC, IEEE)

• The standards IEC [4] and IEEE [5] provide guidelines for interpretation of DGA. In these standards one can for example find graphical interpretations of gas ratios and numerical tables for typical gas concentrations within oil immersed transformer in operation.

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PRINCIPAL CAUSES OF GAS FORMATION IN TRANSFORMER

• Fault gases are caused by corona (partial discharge), thermal heating (pyrolysis) and arcing.

PARTIAL DISCHARGE is a fault of low level energy which usually occurs in gas-filled voids surrounded by oil impregnated material.

• The main cause of decomposition in partial discharges is ionic bombardment of the oil molecules.

• The major gas produced is Hydrogen. The minor gas produced is Methane.

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CONT..

THERMAL FAULTS• A small amount of decomposition occurs at normal operating temperatures. • As the fault temperature rises, the formation of the degradation gases change from

Methane (CH4) to Ethane (C2H6) to Ethylene (C2H4).• A thermal fault at low temperature (<300deg/C) produces mainly Methane and

Ethane and some Ethylene.• A thermal fault at higher temperatures (>300deg/C) produces Ethylene. • The higher the temperature becomes the greater the production of Ethylene.• ARCING is a fault caused by high energy discharge.

Cont..• The CO And CO2 gases indicate the condition of cellulose and paper

insulation.• If The ratio CO/CO2 > 0.1 It indicate the Over heating of the cellulose

& insulation over heating.

IEC ratio codes & Fault classification

Gas Ratios

 

Range of gas ratio

code

Range of code / IEC code

   

<0.1 00.1–1.0 11.0–3.0 1

>3.0 2  

<0.1 10.1–1.0 01.0–3.0 2

>3.0 2  <0.1 0

0.1–1.0 01.0–3.0 1

>3.0 2

  FAULT TYPE

0 0 2 Partial discharge of low energy0 1 1 Thermal Fault of low temperature 0 1 2 Thermal Fault of low temperature < 1 0 0 Flashover, Intermittent sparking1 1 1 Thermal Fault of low temperature 1 1 2 Thermal Fault of high temperatures > 1 2 0 Core and tank circulating currents.1 2 1 Winding Circulating currents.1 2 2 Core and tank circulating currents.2 0 0 Partial discharge of high energy density, Corona2 0 1 Discharge of high energy, Arcing.2 0 2 Discharges of low energy, Continuous sparking2 1 0 Partial discharge of high energy density, Corona2 1 1 Discharge of high energy, Arcing.2 1 2 Discharges of low energy, Continuous sparking2 2 0  

Severe arcing, Overheating of oil. > 2 2 12 2 2

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MATLAB Programming

• From The Analysis of Key gases concentration in the transformer oil and its ratio according to rogers method & IEC code I have prepped MATLAB program for the identify , which type of fault in the transformer May occurs in future.• The MATLAB programming method is simple for users as its not

required much knowledge and data as other method like ANN , Fuzzy Logic , Expert system . • By the Entering the Value of concentration of gages in oil in Program

we get the resultant fault according to IEC standard .

Flowchart

CASE STUDY ON DGA• Transformer detail RATING : 15 MVA 66/11.55KV MAKE : ATLANTAS ELECT PVT LTD Sample take : Bottom point

DGA indicates Hydrogen & Hydrocarbons So need to Investigate the fault & Resample after investigation.

Also the CO/CO > 0.1 Indicate the Insulation overheating.

H2 O2 N2 CH4 CO CO2 C2H4 C2H6 C2H2 TDCG0

2000

4000

6000

8000

10000

12000

14000

2

3635

12513

4 17 159 29 4 0 56

DGA

Gases concentration

VALU

E IN

PPM

BEFOR INVESTIGATION

CONT..• Enter the value in MATLAB Program:

Result: Thermal fault of low temperature

H2 N2 CH4 C2H2 C2H4 C2H6 CO2 CO2 123513 4 0 29 4 159 17

CONT..

CONT..

LV-U phase bus bar Paper insulation burned

CONT..

LV-U phase bus bar bolt affected

Paper and Bolt remove for investigation

Rectification and bolting after cleaning

CONT..

• TEST SAMPLE AFTER INVESTIGATION AND MAINTAINING

H2 O2 N2 CH4 CO CO2 C2H4 C2H6 C2H2 TDCG0

2000

4000

6000

8000

10000

12000

0

3185

10357

0 6 150 0 0 0 6

DGA

Gases concentration

VALU

E IN

PPM

AFTER INVESTIGATION

Paper covering and joint again

Fuzzy Inference system• There are lots of indeterminate factors in process of transformer fault

diagnosis whose influence to the transformer operation status is usually fuzzy and uncertain. • Ratio codes are quantized to define the crisp boundaries of 0,1 and 2.

In practice these boundaries are non crisp (Fuzzy) especially under multiple faults condition. • These codes could lead to errors in diagnosis moving across the crisp

boundaries from one fault to another. To overcome these limitations, Fuzzy System for diagnosis of multiple faults is developed.

Fuzzy set description

• An ordinary set can be characterized as a binary function. Elements in the set can be assigned to1 and remaining elements of the universe can be assigned to 0. The function is generalized so that value assigned to the elements of the universal set located within a specified range which indicates membership grades of these elements within the sets, such function is called membership function and the corresponding set is a fuzzy set.

Fuzzy Control Algorithm

C2H2

C2H4

CH4

C2H6

H2

C2H4/C2H6

CH4/H2

C2H2/C2H4

FUZZY CONTROL

LER

OUTPUT

Proposed fuzzy control algorithm

• The proposed FIS editor prepared using MATLAB Fuzzy Logic Toolbox is shown in Fig.

FIS Editor

Cont..• This fuzzy system consists of 3 ratios C2H2/C2H4 ,CH4/H2 and C2H4/C2H6 as

inputs. Each ratio is fuzzyfied as Very Low, Low, Medium, High and Very High according to membership intervals as defined in Following table ,

Ratio CH4/H2 C2H2/C2H4 C2H4/C2H6

Very Low X<0.09 X<0.09 X<0.9

Low 0.09<=X<=0.11 0.09<=X<=0.11 0.9<=X<=0.11

Medium 0.11<=X<=0.9 0.11<=X<=2.9 0.11<=X<=2.9

High 0.9<=X<=1.1 2.9<=X<=3.1 2.9<=X<=3.1

Very High X>1.1 X>3.1 X>3.1

Cont..• The membership boundaries of Low and High fuzzy are fuzzyfied by

using triangular function.• The membership boundaries of other fuzzy ratios are fuzzyfied by

using trapezoidal function.

Fuzzy Sets for Gases Ratios

Fuzzy set for C2H4/C2H6

CONT..

Fuzzy set for CH4/H2

Rules Editing window :

Result Window

REFERENCES[1] Er.S.Sehgal and Er.D.singh,“Dissolve gas analysis” , IJERT Vol. 1 Issue 6, August - 2012 .[2]R.pandey,MT.Deshpande,“Dissolved Gas Analysis of Mineral Oil Used in Transformer” IJAIEM Volume 1, Issue 2, October2012.[3]SY.Jasmin and J.Shreevastava,“Dissolve gas Analysis of Power transformer”, IJEEER Vol. 3, Issue 5, Dec 2013, 1-10.[4]IEC Standards 60599, “Mineral oil-impregnated electrical equipment in service” - Guide to the interpretation of dissolved and free gases analysis, second edition, Mars 1999.[5]IEEE Standards C57.104-1991. IEEE Guide for the Interpretation of gases generated in Oil-Immersed Transformers, 1991.

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CONT..

[6]Deepika Bhalla, RK Bansal, and Hari Om Gupta , “Application of Artificial Intelligence Technique for DGA of Transformers-A Review ,World Academy of Science, Engineering and Technology Vol;4 2010-02-27.[7] Ali A. Albakry, “Modified Fault Diagnosis Method For Power Transformers Using Fuzzy Logic Technique”,Journal of Babylon university / pure and applied science.