FAULT FINDING PROCESS IN TRANSFORMER USING DGA ANALYSIS WITH THE HELP OF MATLAB PROGRAMMING

By Alok Kumar (29/06) Nilav Kumar (175/06) Md. Faiyaz Shafi (153/06) Mohd. Imran Khan (157/06) Manjeet Kumar Rajak (144/06)

Objectivey Study about the various types of transformer

faults and fault gases generated in their case. y Study about Dissolved Gas Analysis and different techniques used for DGA. y MATLAB program was developed for the simplification of Duvals triangle analysis. y Implementation of the MATLAB program for a few real time case studies (TATA STEEL)

Introductiony Insulating materials within transformers break

down to liberate gases within the unit. The distribution of these gases can be related to the type of electrical fault. y Insulation deterioration factorsy Aging factors y Water contamination y Particle contamination y Paper aging decomposition

Different types of faults and fault gases

Different gas generated in cases of different faults.

Dissolved Gas Analysisy Dissolved gas analysis ( DGA ) is widely used to detect

incipient faults in transformers. y Types of fault that can be detected using DGA

Different methods used for DGA

Key ratio methody The following ratios are used

CH4/H2 (PD assessment), C2H2/C2H4 (Arcing), C2H4/C2H6 (Oil overheating), C2H2/C2H6 (Electrical discharge), CO2/CO (Cellulose overhaeating) C2H2/H2 (Oil contamination from divertor switch LTC), N2/O2 (Consumption of oxygen), C4H8/( CXHY + H2) (Oil overheating at 150 -300 degree C)

y On the axis of abscissas the maximum value of gas quantity is

taken for 1 on the axis of ordinates to plot a ratio in the following sequence: H2, CH4, C2H6, C2H4, C2H2. Thereby a pattern of typical fault could be displayed.

Rogers Ratioy Rogers Ratio Method compares quantities of different

key gases by dividing one into the other. y By looking at the Gas Generation Chart one can see that, at certain temperatures, one gas will be generated more than another gas. y Rogers used these relationships and determined that if a certain ratio existed, then a specific temperature had been reached. y It uses following three ratios (CH4/H2 ), (C2H4/ C2H6), (C2H2/C2H4)

Duvals Triangle Methody The Duval Triangle was first developed in 1974 . It uses three

hydrocarbon gases only (CH4, C2H4 and C2H2). y These three gases correspond to the increasing levels of energy necessary to generate gases in transformers in service. y In addition to the 6 zones of individual faults mentioned in Table 2 (PD, D1, D2, T1, T2 or T3), an intermediate zone DT has been attributed to mixtures of electrical and thermal faults in the transformer.

Duvals Triangle

Development of Duvals triangle by MATLAB PROGRAM y Conversion of triangular coordinate to rectilinear coordinate. y Determination of the coordinates of different fault zones. y Logic to check that fault coordinate lies in which zone.

y RX = Y + X/2 y RY = X sin (pi/3)

y The Duvals triangle has been divided into different fault

zones and representing their respective triangular as well as rectangular coordinates with the help of formula deduced in the previous section (stage 1).

DIFFERENT FAULTS D1- Discharge of low energy (ZONE 1)

NO. 1 2 3 4 1 3 5 6 7 5 6 7 8 9 10 11 13 14 9.1 10 11 12 13 14 15 16 15 16 9 9.1

X 0 87 64 0 0 64 0 47 31 0 47 31 96 46 35 0 98 98 50 35 0 0 98 98 80 76 80 76 46 50

Y 23 0 23 0 23 23 71 40 40 71 40 40 0 50 50 85 0 2 50 50 85 100 0 2 20 20 20 20 50 50

Z 77 13 13 100 77 13 29 13 29 29 13 29 4 4 15 15 2 0 0 15 15 0 2 0 0 4 0 4 4 0

RX 23 0 23 0 23 23 71 40 40 71 40 40 0 50 50 85 0 2 50 50 85 100 0 2 20 20 20 20 50 50

RY 0 75.32111 55.40863 0 0 55.40863 0 40.69071 26.83856 0 40.69071 26.83856 83.11294 39.82495 30.30159 0 84.84446 84.84446 43.28799 30.30159 0 0 84.84446 84.84446 69.26079 65.79775 69.26079 65.79775 39.82495 43.28799

D2 - Discharge of high energy (ZONE 2)

DT (ZONE 3)

PD - Partial discharge (ZONE 7)

T3 thermal faults >700 (ZONE 4)

T1 thermal faults 300 >duval enter the value of CH4 5183 enter the value of C2H4 9730 enter the value of C2H2 1107 fault = T3

Output of MATLAB program

y There is thermal fault of high temperature >700C. This is confirmed by both the

methods used for DGA analysis. y This is due to Local overheating of the core due to concentration of flux. Increasing hot spot temperatures; varying from small hot spots in the core, shorting links in the core, overheating of copper due to eddy bad contacts/joints (pyrolytic carbon formation) up to core and tank circulating currents.

DGA Analysis Based on Rogers ratioRange of ratios C2H2/C2H4 R2 3.0 0 1 1 2 Code CH4/H2 R1 1 0 2 2 C2H4/C2H6 R5 0 0 1 2

Fault Types Normal (No fault) Partial discharge of low energy density Partial discharge of high energy density Discharge of low Energy

0 0

0 1

0 0

1 1 to 2

1 0

0 1to 2

Discharge of high Energy

1

0

2

Thermal fault of low temperature 700C

0

0

1

Typical phenomena Normal aging. Discharge in gas filled cavities resulting from incomplete impregnation or super saturation or cavitation or high humidity. As above, but leading to tracking or perforation of solid insulation. Continuous sparking in oil between bad connections of different potential or to floating potential. Breakdown of oil between solid insulation. Discharges with power follow-through. Arcing-breakdown of oil between windings or coils or between coils to ground. Selector breaking current. General insulation conductor overheating. Local overheating of the core due to concentration of flux. Increasing hot spot temperatures; varying from small hotspots in the core, shorting links in the core, overheating of copper due to eddy bad contacts/joints (pyrolytic carbon formation) up to core and tank circulating currents.

0

2

0

0 0

2 2

1 2

Conclusion and Future Scopey This project report dealt with the modern preventive

maintenance technique of Dissolved Gas Analysis. The purpose of this project is greatly solved with the MATLAB program developed, which is used for some of the real time case study data.y Direct online monitoring can be achieved by installing a Gas

analyser and interfacing it directly with the software to sound an alarm in the case of a fault.

Thank You