What is Oti in transformer?
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.
How does OTI 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.
How does a transformer winding temperature gauge 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 do you check the temperature of a transformer?
Ambient temperature is measured by means of a thermometer placed around the transformer at three or four points situated at a distance of 1 to 2 meter from and half-way up the cooling surface of the transformer.
Why CT s2 is earthed?
If the secondary is not connected to a load, then it tries to maintain the counter magnetic field, and voltage levels may skyrocket. Levels can get so high, the air around the CT may start to break down and lose its insulating properties. This is why you should always make sure the secondary side of the CT is shorted.
Why bushing is used in transformer?
The bushings used for the low voltage winding(s) of a transformer are often solid type with a porcelain or epoxy insulator. Their purpose is to control the voltage field around the center conductor so that the voltage distributes more uniformly across the surrounding insulation system in the bushing.
What is the temperature of transformer?
The average ambient temperature for a transformer over a 24 hour period should not exceed 30 degrees Celsius. For instance, if the transformer ambient temperature was 40 deg. C for 12 hours, then the transformer must not exceed 20 deg. C for the remaining 12 hours to average a 30 deg.
What is the winding temperature of transformer?
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 temp rise in transformer?
What Is Temperature Rise of a Transformer? All devices that use electricity give off waste heat as a byproduct of their operation. Transformer temperature rise is defined as the average temperature rise of the windings above the ambient (surrounding) temperature, when the transformer is loaded at its nameplate rating.
Which test can be performed for temperature rise in transformer?
Heat run test is one of the type tests on power transformer. This test is also called temperature rise test. This test reproduces conditions of continuous rated load and the temperature rise occurring during the load.
Why is CT secondary closed?
As CT is oil filled, because of overheating, the oil of CT will get boil and start to vaporize. Because of vaporization of CT oil, the CT housing will get pressurized and blast. This blasting will lead to fire and smoke.
Why do you ground CTs?
To prevent secondary circuits from reaching dangerous potential, the circuits shall be grounded. Grounding shall be made at only one point on a voltage transformer secondary circuit or galvanically interconnected circuits.
What is the working principle of vapor pressure thermometer?
Working principle “Vapour pressure of a liquid depends upon the temperature. If this liquid is partially filled in an enclosed chamber, it will create a definite vapour pressure, by which, temperature can be measured”. Working of Vapour pressure thermometer is similar to liquid filled thermometer.
What is a liquid pressure thermometer?
9. Liquid Pressure Thermometer: Usually Mercury is used as liquid Principle of working: expansion of liquid due to an increase in the pressure in a given volume Range :-30°C to 550°C 10.
How many types of pressure thermometers are there?
There are two types of pressure thermometers: Liquid pressure thermometer. Vapour pressure thermometer. Operating Range: up to 300°C. Method used: Expansion of Liquids. If temperature increases, liquid expands in volume. This change in volume of liquid is directly proportional to change in temperature.
What happens to vapour pressure when temperature decreases?
Conversely, a drop in temperature causes part of the gaseous vapour to condense and the vapour pressure to decrease. The indicated temperature decreases. Since the vapour pressure curves are not linear, the scale for vapour pressure thermometers is not evenly subdivided.