Firstly kernel and pulley assembling are made after that power distribution units are sent to desiccators. Completed active parts of distribution units are dried in special ovens with vacuum for a while. Later, the transformer active part is added into the transformer tank, and filled with special transformer oil under the vacuum. Then, the transformer becomes ready for test....
HV windings; consist of high heat-resistant enameled coil wire, and high dielectric pressboard with its insulation. Windings are made in such way that eliminates radial forces, if short circuit occurs in transformers.
LV windings; usually made with rectangular copper, aluminum, copper foil or aluminum foil. Windings are made in the form of resistance against axial forces in the case of short circuit in transformers....
The walls of the transformer tanks: according to project criteria, they are manufactured generally from corrugated steel for distribution transformer. The corrugated steel thickness is 1, 25 mm or 1, 50 mm. Generally Cap and transformer tank are manufactured of hot rolled steel pallet. The tank oil drain valve and two cross skids carrying the wheels are located in lower epoxy based two-component paint part and the wheels are 90 rotatable in order to push the transformer at both directions. After completion of welding the first leakage test is performed on the tank.
Transformer Cover: Steel bolt, cap nut and spring washer, cover gasket are installed upper side of tank. On top of the cover there are HV and LV bushings, conservator, thermometer pocket and filling pipe etc. The off-load tap changer is assembled over the cover. In hermetic transformer in spite of there is not Buchholz relay, there is a hermetic protective relay.
Hermetically sealed relay
It is preferred to be used in hermetic designs. It indicates gas discharging, oil temperature and internal pressure of the tank and used in transformers bigger than 500 kVA. There are 2 switches each for gas discharging, tank pressure and the oil temperature.
Magnetic oil level indicator
The magnetic oil indicator is designed to measure the level of the transformer oil in the conservator tank and give an analogical indication of the oil level inside the conservator on which are usually mounted; when required, they give an electric alarm signal if the oil reaches the minimum and/or the maximum admitted level.
Alcohol Thermometer is designed to display oil temperature and is without contact.
The dehydrating breather
Dehydrating Breathers are used to prevent the normal moisture in the air from coming in contact with the oil in electrical equipment as the load or temperature changes. This reduces the degeneration of the oil and helps maintain its insulation capability. The size of dehydrating breather is determined by the quantity of oil in the transformer.
Pressure relİef valve
It is preferred to be used in hermetic designs. Pressure Relief Valve is a safety element of the transformer employs to prevent heavy damages of the tank in the case of sudden rise of the internal pressure. These Valve have been designed in order to remove the excess pressure in a very short time as soon as the pressure in the tank rises above predetermined safe limit the valve operates and allow the pressure to drip instantaneously, it avoids damage to transformer body. It can also be used with switches.
Buchholz Relay is fitted in the connection pipe between the transformer tank and the conservator tank and is designed to detect faults arising internally, such as interturn short circuits in coils and windings and against oil loss in order to minimize the propagation of any damage which might occur within oil-filled transformers, capacitors and reactors supplied with oil conservator. When a fault occurs in the transformer, the small bubbles of gas, which pass upwards to the conservator, are trapped in the relay housing, thus causing its oil level to fall. As a result, the upper float rotates on its hub and operates the alarm switch, thus operating an external alarm device. There are 2 contacts rated at 5 A, 250 VAC or 0.2 A 250 VDC
Contact oil temperature thermometer
Oil Temperature Thermometer is designed to measure temperature and display the measured maximum value of oC 120 and can easily be reset via a push-button located underneath. It has 2 adjustable control switches with values of 5 A 250 VAC or 0.2 A, 250 VDC....
▪ Measurement of windings resistance
▪ Measurement of no-load losses
▪ Measurement of no-load currant
▪ Measurement of load losses
▪ Measurement of impedance voltage
▪ Induced over-voltage test
▪ Applied voltage test
These tests can only be done for a fee when there is a demand from costumer.
▪ Tests for temperature rise of oil and winding
▪ Lightning impulse test
▪ Measurement of fractional discharge
▪ Measurement of harmonics
▪ Measurement of level of noise