Evaluation of Possible Faults by the Rogers and Doernenburg Ratios in the Transformer Oil.

Evaluation of Possible Faults by the Rogers and Doernenburg Ratios in the Transformer Oil.

it is righty said that the concentration gas ratio is more trustable way from which we can easily understand and predict the fault inside the transformer. Rogers and Doernenburg were developed these ratios in European.

The following ratios are used:

Ratio 1 (R1): CH4/H2

Ratio 2 (R2) C2H2/C2H4

Ratio 3 (R3) C2H2/CH4

Ratio 4 (R4) C2H6/C2H2

Ratio 5 (R5) C2H4/C2H6

Doernenburg Ratio Method, Step 1

A sample of gas is collect from the head space which was above the level of oil in the transformer.

Doernenburg Ratio Method, Step 2

Be sure your method of calculation is true. One of the concentration of gases like hydrogen, methane, C2H2 and C2H4 must be as well as two times of the L1 values (below) and concentration of other three gases increased to the value of limit L1and it show that the transformer is faulty. As minimum as concentration of a single one gas must be increase the L1 values that’s given below.

Dissolved Gases	L1 Value ppm
Hydrogen	100
Methane	120
Carbon Monooxide	350
Acetylene	35
Ethylene	50
Ethane`	65

Hydrogen 100 Methane 120 Carbon Monoxide 350 Acetylene 35 Ethylene 50 Ethane 65

Doernenburg Ratio Method, Step 3

Suppose that the analysis ratio is true for this transformer and also check the ratio in order of R1, R2, R3, R4.

Doernenburg Ratio Method, Step 4

Now look all the calculating ratios which is measured for a particular task exist in the given table. If the ratios is present in the table than our suggested diagnosis is true.

Doernenburg Ratio for Gases key

Indicated fault Diagnoses	Ratio 1	Ratio 2	Ratio 3	Ratio 4
Thermal Decomposation	.1-1.0	.75- 1	.1 - .3	.2 - .4
Corona	.01-.1	Not significient	.1- .3	.2 - .4
Arcing	.1 – 1	.75- 1`	.1- .3	.2-.4

Doernenburg ratios, Rogers ratios, and Duval’s Triangle Mode are some commonly used techniques include application.
Doernenberg ratios and Rogers ratios are recognized in the ANSI/IEEE
C57.104. CH4/
H2, C2H2/C2H4, C2H2/CH4, C2H6/C2H2 and C2H4/C2H6. (Hamrick, 2009-2010)

Gases are also dissolved in mineral oils with different rates .We can easily find the fault by absorbs the ranges of ratios. The range of different gases is given in the table.

Rogers Ratios Method:

Rogers Ratio method have same process to measure the ratios as well as the process of Doernenburg method but three is only difference is that only three ratios are used in it. 

 

Duval’s Triangle Model is known in IEC Guidelines. The Duval Triangle Model (IEC 60599) is published in 1989 by increment in 2002.Calculate the total amount of three key gas ethylene (C2H4), ethylene (C2H4), ethylene (C2H4) and then divide total of all gases to calculate the percentage of each one gas and find the problems in transformer using the key gasses After that plot a triangle from these values which was absorbed.
In the triangle  the temperature  effect with ratio are shown like thermal fault <  300 ºC, thermal fault 300-700 ºC, thermal fault> 700 ºC; low-energy discharge; high
energy discharge; and partial discharge.
Sometimes the ratio to key gases CO2 and CO act as a alarm in the decomposition of cellulose .It is often seen that the ratio of formation of key gas CO2 is usually 7 to 20 time greater than CO. If the ratio of both these gases is greater than 7 then it consider to be at normal level and if the ratio of carbon di oxide and carbon mono oxide is 5or less than 5 then it is the indication of optional problem. Sometimes additional furan test is required to perform when if the degradation of cellulose is problem carbon mono oxide, hydrogen, methane and C2H6 are also increase. The transformer consider faulty for more inception if the ratio of carbon mono oxide and carbon di oxide ratio is 3 or less than 3 with the increased the furans. Due to overheating, chemicals and in the addition of Carbon di oxide, carbon mono oxide the cellulose decompose and released in to the oil. The mixture which formed during this process is known as Furans or furanic compound.  
In the fault free Transformer the amount of furan is negligible in the oil (<100ppb). The amount of furans increase when the quantity of cellulose decrease. When the furan levels between 500 to 1000 ppb then it shows the cellulose growing older and showing the effects of increasing age. And when the furan levels greater than 1500 ppb then it show the potential harm of insulation.