Failure of 150 KV Power Transformer in Indication of Dissolved Gas Analysis Test in Total Dissolved Combustile Gas (TDCG) Method

A transformer is an electrical device to change the voltage from one level to a certain level with the same frequency that is generated from the generator. This transformer is used in a power plant to increase the voltage from the generator to be supplied to extra high voltage substations. By knowing the type and amount of gas in the transformer oil, it can be seen that the failure occurred. Preventive steps can be taken before the transformer is more severely damaged or a breakdown which will result in disrupted and detrimental electrical energy supply. The method used in this research is data collection methods used are observation, interviews and participation conducted at PT. Krakatau, Serang Banten. The method used to determine the failure of the transformer is the Dissolved Gas Analysis (DGA) method. The DGA test uses several methods to interpret the data, these methods are Total Dissolved Combustile Gas (TDCG), Key Gasses, Doernenburg Ratio, Roger's Ratio, IEC Ratio and Duval's Triangel. The method used in this research is direct observation of the process of taking transformer oil samples and testing transformer oil samples with the Transport-X tool. The result of this research is that the transformer condition is still in normal condition, because the appearance of CO 2 gas has almost crossed the condition limit, so other supporting methods are needed to find the cause of the gas. Key gasses indicate the presence of overheating of paper insulation, IEC Ratio diagnoses transformer failure caused by heat failure at temperatures of 300


INTRODUCTION
Considering the very important role of the transformer, the failure of transformer operation is highly undesirable because it will have an adverse impact on production in the industry that supply needs the electrical.
Therefore, the transformer must always be maintained in an optimal condition to prevent damage or breakdown of the transformer isolation so that it can cause the transformer to suddenly stop operating.
If there is interference with the transformer due to thermal or electrical disturbances, gases will appear in the transformer oil.By knowing the type and amount of gas in the transformer oil, it can be seen the disturbance that occurs.So that preventive steps can be taken before the transformer is more seriously damaged.This method is known as DGA (Dissolved Gas Analysis).A transformer is an electrical device that can transfer and convert electrical energy from one or more electrical circuits to another, through a magnetic coupling and based on the principle of electromagnetic induction [1].A transformer is a static electromagnetic electric device that functions to move and convert electrical power from one electrical circuit to another, with the same frequency and a certain transformation ratio through a magnetic coupling and works based on the principle of electromagnetic induction, where the ratio of the voltage between the primary side and the secondary side is directly proportional to the number of turns and inversely proportional to the current [2].So, a transformer is an electrical device that functions to transfer and convert electrical energy from one circuit to another using the principle of electromagnetic induction.Transformers are widely used, both in the field of electric power and electronics.The use of a transformer in the power system allows selecting the appropriate and economical voltage for each need, for example the need for high voltage in long-distance electrical power delivery [3].
Below is the basic construction of a transformer obtained from the Transformer Theory book written by [4], as in Picture 1 below.

Figure 1. The basic construction of the transformer
Information: 1.The core / terrace / kren.Transformer oil is a liquid insulating material, this oil is widely used as a dielectric in transformers [9].The main function of transformer oil is as an insulating medium between parts that contain a potential difference so that there is no electric jump (flash-over) or spark (spark-over), and other functions as a cooling medium on transformers, power cables, or as a medium.
Transformer oil must have the property of dissolving gases, especially flammable gases.This is intended to prevent especially gases.The dissolved gas in oil of the transformer, it can be used to detect and estimate condition of the transformer that is currently operating [14].

Gas Cromatograph
The technique of separating certain substances from a compound compound based on their level of evaporation (volatility).The way it works is based on the absorption properties of the cromatographic gas column system to the sample.The injected sample will be streamed by the carrier gas.The gases which have different absorption properties will be separated.The separation of these gases will be detected by the detector which is converted into the recording system.The type and amount of gas can be determined by comparing it with the amount of standard gas whose composition is previously known as in figure 2. Photoacoustic Spectroscopy basically has a unique and distinctive electromagnetic radiation absorption capability.This ability is usually applied to the infrared spectroscopic method to produce photo acoustic effects.
The absorption of electromagnetic radiation by gases will increase the gas, as in figure 3 below [15].4 below.
This method uses a ratio that utilizes hydrocarbon gas.However, in this method only three compounds were compared.

2. Primary winding connected to a power source. 3 .
The secondary winding is connected to the load.If the primary coil is connected to the voltage (source), it will flow an alternating current of I1 on the coil.Because the coil has a current core, I1 causes a magnetic flux that Volume 6, Number 1, May 2021 ISSN 2528-2611, e-ISSN 2528-2700 also changes in essence.As a result of changing magnetic flux, the primary coil arises ep-induced emf [5].The amount of induced emf in the primary coil is: ep= Where: ep : GGL induction on the primary coil Np : Number of turns of the primary coil dФ : Changes in the lines of magnetic force in weber units ( 1 weber = 10 8 Maxwell) dt : Time changes in seconds.The magnetic flux that induces epinduced EMF is also experienced by the secondary coil because it is a mutual flux.Thus the flux induces ice-induced EMF on the secondary coil.In the book the electrical engineering handbook, transformers are classified into two main categories, namely dry type transformers and liquid-filled transformers.First, Dry Transformer is cooled by natural air circulation or forced circulation or natural inert gas through or around the transformer enclosure.Dry Transformers are further divided into vented, sealed, or encapsulated types depending on the transformer construction.Dry Transformers are widely used in industrial power distribution for voltages up to 5000 kVA and 34.5 kV.Second, the Liquid-filled Transformer is cooled by natural or forced circulation of coolant through the transformer windings.This fluid serves as a dielectric to provide superior stress resistance characteristics.The most common liquid used in transformers is mineral oil or what is known as Transformer Oil which has a continuous operating temperature of 105 o C, a flash point of 150 o C, and a fire point of 180 o C [6].A good transformer oil has a breakdown voltage strength of 86.6kV/cm (220kV/in) which is much higher than the penetration power of 9.84 kV/cm (25kV/in) at atmospheric pressure.Silicone liquid is used as an alternative to Mineral Oil.The breakdown strength of silicon fluid exceeds 118 kV/Cm (300kV/in) and has a flash point of 300 o C and a fire point of 360 o C [7].The liquid-filled silicon transformer is non-flammable, the high dielectric strength and the superior thermal conductivity of the coolant make it ideal for high-voltage power transformers used in modern power generation and distribution generators [8].
Mineral insulating oil is formed from several hydrocarbon molecules containing chemical groups CH, CH2, and CH linked by carbon molecular bonds.The breaking of some CH and CC bonds can occur as a result of electrical and thermal disturbances, with Volume 6, Number 1, May 2021 ISSN 2528-2611, e-ISSN 2528-2700 the form of small, unstable fractions, in the form of radicals or ions such as H*, CH3*, CH2*, CH*, or C* (among other, more advanced forms.complex) which recombine rapidly through complex reactions to form gas molecules such as hydrogen HH methane CH, 3-H ethane CH3-CH3 ethylene CH2 = CH2 or acetylene CH = CH, these gases are known as fault gases.These gases accumulate as free gas if they form in large quantities and in a fast time [11].When the oil decomposes due to heat, cellulose insulation produces CO and CO2 and some H2 and CH4 in the oil.The degree to which the compound is formed depends on the temperature and volume of the material at that temperature, with two processes, namely [12]: (1) The over heating process, when cellulose/paper is heated by overheating (at least 140 o C) in a closed system according to conditions transformer, then the decomposition of cellulose into carbon monoxide (CO) and carbon dioxide (CO2) gas, and (2) the pyrolysis process, when cellulose is heated to decompose by pyrolysis and temperatures above 250 o C in a closed system, more carbon will be formed.monoxide (CO) rather than carbon dioxide (CO2) with an amount roughly four times greater than CO2.Transformer oil is a complex mixture of hydrocarbon molecules, in linear or cyclic form, which contains bonded groups of CH3, CH2 and CH molecules.The breaking of several bonds between the elements CH and CC as a result of thermal or electrical failure will produce ion fragments such as H, CH3, CH2, CH or C, which will later recombine and produce gas molecules such as hydrogen (HH), methane (CH3-H), ethane (CH3-CH3),

Figure 5 Figure 5 .
Figure 5 below.Table 4. IEC Ratio Method Definition Code Range of Gas Ratio

Table 1 below . Table 1 .
Types of Faults based on the

Table 2 .
Code definition of the Roger ratio

Table 3 .
Type of Failure based on Code

Table 5 .
DGA test results (TDCG <720).Condition 1 indicates that the transformer is operating normally, but it is still necessary to monitor the condition of the gases.2.Analysis Key Gas MethodCarbon monoxide (CO) gas is the Key Gases to indicate excessive heat in paper insulation (Overheated Celullose).