Transformer moisture measurement
Water In the transformer cause to produced odd substance, also decrease the insulation of break down. When a large amount of water content of paper as a result bubbling produced and also increased the chance of dielectric breakdown. There are three main source from which the water comes in the transformer: residual moisture in the thick structure element login from the atmosphere and cellulose, oil increase the speed of decomposition the amount of moisture in the transformer is less than 1 %, but the target value is 0.5 % when the new transformer is formed and ready to use.
Thick insulation component, plastic1 are the component in which the amount of moisture is 2 to 4 %. At the time of repair or service, these moisture seeps into the transformer oil when increasing the content of water in the rarer insulation structure. The water present in the major sources of transformer pollution. Three processes are directly related them firstly amount of water observed in the insulation from the air at the time of installation and repair work ,the second one is its natural that moisture flow from high concentrations to low concentration ,the same thing is to happen in the transformer the concentrations of water in the atmosphere is higher then the concentrations of the transformer oil in the tank, and the third one is that a large amount of viscous wet air flow inside the transformer that caused the difference of pressure in the atmosphere and the pressure in the tank
A minimum amount molecules flow inside them but the major sources of water penetration inside are air flow through the poor sealing like through the bushes sealing points and loop which moderate the temperature inside etc., all this is happening due to the pressure difference. If the transformer has improper sealing or the instantly only decrease of pressure then a large amount of water like rain water penetrate in the transformer in very minimum time.
Methods and instrumentation for moisture measurement
In the transformer industry, the term “moisture” is used to differentiate the how much amount of water is dissolved in the transformer oil or the amount the water absorbed in the paper.
Sometime the term water or water content is used commonly but these are synonyms of each other and use to explain the same theory. In the transformer, the water is presented in the different parts of the insulation system. Water is the water it makes its own way and so it is present in solid insulation or dissolved in the oil, sometime it is found at core or bottom of the transformer as the form of liquid water.
There are a number of methods and instruments are used in the market for the measuring the moisture. When we want to calculate the water content in oil or polymer relative humidity or relative saturation sensors is frequently used. When we calculate the relative saturation of oil can easily get the absolute moisture which is expressed in (ppm).
Water content of paper insulation
A new concept of measuring transformer moisture was introduced which is based on the water in paper activity method. The different aspect of water in paper activity used to measure the amount of moisture in the both new one or old transformer insulation system. Another term “active water content of the paper (WCP)” was also determined. This concept of WCP shows the relation water in paper and oil in the insulation of transformer. The figure shows the same parameter of water in paper activity to the active water content of paper.
There is another way to determine the WCP of paper insulation in a paper-oil insulation. System and equilibrium chart of moisture is used.
Another chat of moisture equilibrium is published in 2 and earn very fame which is shown in the
figure.
In this show the difference between the water content of oil (WCO) which is expressed in oil, the percentage moisture of paper and the temperature.
Assessment of moisture in an operating transformer
it is usually said that operating transformer is not in moisture equilibrium. So the both of these charts of moisture equilibrium which is shown in the figure cannot me utilize directly for moisture. Due to this another method of accessing the moisture in the transformer is developed which is based on the Monash water in paper (WIP) algorithm. This method consists of three steps.
Assessment of true oil relative saturation in the transformer
Assessment of the water-in paper activity (AWP) for the transformer oil
Assessment of the active water content of the paper (WCPA) as a
function of AWP and temperature. (Roizman, 2002)
On the basis of WIP algorithm, a software application is developed as the name of Transformer Moisture Monitor (TMM). The TMM uses neuron-fuzzy computing to determine moister sensor output. The TMM get data form via sale HMP228 Humidity and temperature transmitter.
The HMP228 transmitter gives on line measurement of the transformers moister and temperature.
Transistor gives information time to time and indicates earlier when the transformer has some issue.
Vaisala;s microprocessor based HMP228 Transmitter has the high speed of execution, reliable easy to use and maximum accuracy. The earlier model of HMP228 Transmitter can measure only average water solubility in the transformer mineral oil. The water ionization in the oil depends on the temperature it will increase as the temperature increase. Transmitter measured the water activity and cultural ppm output. One of the benefits of the water activity is that indicate the directly rather than the oil is too moist. The activity of water measurement depends upon the aging or temperature of the oil.
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