Transformer Oil Testing丨Moisture Test丨Dielectric Test丨Reconditioning of Transformer Oil丨Electronicsinfos

Testing OF Transformer Oil 

Transformer Oil Testing丨Moisture Test丨Dielectric Test丨Reconditioning of Transformer Oil丨Electronicsinfos

we used mineral oil in the transformer that is provide cooling and insulation. we test the transformer oil at different intervals to check its insulation strength and make the transformer reliable and efficient. during the testing of the transformer, we check the humidity or moisture in the oil and check the dielectric strength. if the moisture level is 1:100000 the dielectric strength becomes 22000 volts the result is the insulation is reduced concerning the standard insulation level. if the transformer insulation is reduced the chance of a short circuit and flashover is easily possible.

There are two Types of Tests in the transformer to check the insulation that is described below

  1.  Moisture Test
  2.  Dielectric Test

Moisture Test

A moisture test is a type of test in which we find the moisture level of the transformer oil is called moisture test. There are different methods to check the moisture level in the transformer oil that is described below

Red-Hot Piece of Steel Method

This is the Method in which we take a sample of base oil from the transformer. we use a hot piece of steel and put it into the sample oil if the oil contains moisture the hissing sound is produced in the oil.

Copper Sulphate Method

This is the most reliable method to check moisture. In this method, we used copper sulphate crystals .when we heat copper sulphate crystals the colour changed to white. we put this crystal into sample oil, if the colour of the crystal is changed to blue its means the oil contains moisture.

Spark-Gap Test

Spark-gap is also another reliable method to check the moisture in the oil. in this method, we use two balls of copper in the oil. the distance between the balls is 0.15 inches. we hang these balls in the oil and provide a potential difference of 25000 volts. if an oil contains moisture the arc is produced in the oil across balls otherwise no arc is produced in the oil.

Dielectric Test

A dielectric test is used To test the Dielectric Strength of Transformer Oil. This test was conducted by a standard portable oil testing set. The size of This box is 60*100 mm2.there are two electrodes. the distance between both electrodes is 4mm. In this method, we fill a sample oil in the box and provide a potential difference of 40kv to 1 minute. if oil tolerates this spark of 1 minute without producing an arc it means the dielectric strength is good. the standard voltage is 45kv to test the dielectric. 

Drying of Silica Gel and There Moistening Test

Most of the transformers are used outdoors so there is always a possibility of winding insulation or oil moisture. the dielectric strength is reduced due to the moisture in the oil so there is a possibility of flashover in the transformer. to minimize the moisture effect we used a silica gel in the transformer. the dry silica gel colour is blue when it absorbs the maximum moisture its colour change to pink.to recover the silica gel property we heat a silica gel at the temperature of 300F. the period is 6-8 hours for recovery.

Reconditioning of Transformer Oil

There are two methods of reconditioning oil that is described below.

  1.  Filter Press Method
  2. Activated Alumina & Fuller Earth

Filter Press Method

This is the most reliable method to recondition the transformer oil .in this process we pass out the oil in the oil filter press. To save time we pass out the oil from the centrifuge. The centrifuge process filters heavy materials like carbon etc. filter consists of a helical gear pump, cast iron, paper sheets, oil strainer and pressure gauge. the working pressure of the filter press is 20 to  40 inches. during the oil reconditioning, we pass out the oil into the filter and pour it into another tank. we must follow the pressure gauge to check the pressure if pressure increases its means the filter is not in good condition.                                                   

Activated Alumina & Fuller Earth

The Oil reconditioning process is also done with activated alumina and filler earth. there are two different methods the first method is better because this method removed the moisture. To Recondition the oil with the method of activated alumina we put the alumina and silica gel into a special breather. after that, we rotate the oil at a specific pressure. the alumina required in the oil is following the method 

Q= 0.412 * N * O

Q = activated alumina quantity in pounds
N= Nutrilization Number of oil
O=Oil quantity in a gallon 
For Example, A Oil tank consists of 200 gallons of oil. the neutralization number of the oil is 0.7. the required quantity of activated alumni is 

Q = 0.412 *0.7*200
Q = 57.68 lb

We did recondition with the Fuller Earth .filler is a specific type of mud that is used to wash clothes in industries.

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