What is the difference between OTI and WTI?

The WTI means winding temperature Indicator and OTI means Oil Temperature Indicator which indicates the winding temperature & oil temperature of the transformer and operates the alarm, trip, and cooler control contacts. This instrument operates on the principle of thermal imaging and it is not an actual measurement.

Which temperature is high in transformer oil or winding?

Liquid-filled transformers come in standard rises of 55C and 65C. These values are based on a maximum ambient temperature of 40C. That means, for example, that an 80C rise dry transformer will operate at an average winding temperature of 120C when at full-rated load, in a 40C ambient environment.

What is temperature rise?

Temperature rise is the difference between the average temperature of the transformer windings and the ambient temperature.

How does a winding temperature indicator work?

The Winding Temperature Indicator, WTI is provided with a maximum temperature indicator. The heating resistance is fed by a current transformer associated to the loaded winding of the transformer. The increase in the temperature of the resistance is proportionate to that of the winding.

How does WTI CT work?

The basic operating principle of WTI is same as OTI. But only difference is that the sensing bulb pocket on transformer top cover is heated by a heater coil surrounded it. Hence the current through the heater coil is directly proportional to the current flowing through transformer winding.

What is temperature rise test in transformer?

A temperature rise test of a transformer is an important test which should be included in any type test of an oil transformer. In this test, we check whether the temperature rising limit of the transformer winding and transformer oil is as specified by the manufacturer.

How does the oil temperature indicator of a transformer work?

This device measures top oil temperature with the help of sensing bulb immersed in the pocket by using liquid expansion in the bulb through a capillary line to operating mechanism. A link and lever mechanism amplifies this movement to the disc carrying pointer and mercury switches.

Which of the following shows the maximum rise in the temperature?

So, –4°C to 8°C shows the maximum rise in the temperature.

What is class B temperature rise?

Class B: Maximum Temperature Rise: 80°C.

What is temperature rise test?

Temperature rise tests are used to make sure that a product does not get overheated during operation. STRI performs temperature rise tests with currents up to 8000 A AC and 8400 A DC. Temperature measurement of overhead line joints with IR-camera.

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