Transformer Testing Methods

All transformers are subjected to the following Routine tests: Insulation resistance Test. Winding resistance Test. Turns Ration / Voltage ratio Test.

What is the special test on transformer?

Special Tests of transformer include Dielectric tests. Measurement of the harmonics of the no-load current. Measurement of the power taken by the fans and oil pumps. Tests on bought-out components/accessories such as Buchholz relay, temperature indicators, pressure relief devices, oil preservation system, etc.

How do you test a 3 phase transformer?

Test Procedure: Keep the tap changer in the lowest position and open all HV and LV terminals Then apply three phase 415 V supply on the line terminals for three-phase transformers and single phase 230 V supply on single phase transformers. Measure the supply voltage and current in each phase.

What are the 3 types of transformers?

Depending on the Power rating and specification, Power transformers can further be classified into three categories: Small power transformer, Medium Power transformers, and the Large power transformers.

What is Megger test of transformer?

Insulation Resistance Test or Megger Test of Transformer: Insulation resistance is the ratio of applied voltage to the resulting current at a specified time after the voltage is applied. Direct voltage are used for measuring insulation resistance values. Insulation resistance test of transformer is essential type test.

Why kVA rating is used in transformer?

The first reason is the power loss in the transformer. Thus, the total losses in a transformer depend upon volt-ampere (VA) only and not on the power factor of the load. That is why the transformer rating is given in kVA and not in kW.

What is a type test?

Type test means a test on one or more sample components of the same type and manufacturer to qualify other components of that same type and manufacturer. A type test is not necessarily a test of the as-built components.

What is IEC standard for transformer?

IEC 61558 is a series of standards maintained by the IEC Technical Committee (TC) 96 – “Transformers, Reactors, Power Supply Units and Combinations Thereof”.

What is BDV test of transformer oil?

BDV test means the Breakdown Voltage Test. This test is performed for verifying the dielectric strength of the oil of the transformer. Dielectric Strength is the maximum capacity to resist the voltage of insulating oil. This test demonstrates the dielectric Strength of Transformer Oil.

What is OC and SC test?

The open-circuit test and the short-circuit test being performed on a transformer to determine the circuit parameters, efficiency and the voltage regulation without actual loaded of the transformer.

How many types of transformer testing are there?

Overall there are eight types of transformer testing; however, these are four of the most common. All of these tests are critical for maintaining the integrity of the transformer and without them, the operation can be severely hindered.

How many ohms should a transformer read?

You should get a reading of 0 ohms. Now, touch the red probe to one of the input terminals and take a reading. You should get a reading of either 120 volts or 240 volts, depending on how your transformer is wired. If you don't get a reading, there may be a problem with how your transformer is wired.

What is CT ratio in transformer?

The CT ratio is the ratio of primary current input to secondary current output at full load. For example, a CT with a ratio of 300:5 is rated for 300 primary amps at full load and will produce 5 amps of secondary current when 300 amps flow through the primary.

What are 2 types of transformers?

Commonly used transformer type, depending upon voltage they are classified as:

• Step-up Transformer: They are used between the power generator and the power grid.
• Step down Transformer: These transformers are used to convert high voltage primary supply to low voltage secondary output.

Which oil is used in transformer?

Transformer oil is most often based on mineral oil, but alternative formulations with different engineering or environmental properties are growing in popularity.

What is IR value of transformer?

Voltage	Test Voltage (DC) LV side	Min IR Value
Up to 6.6KV	500V	200MΩ
6.6KV to 11KV	500V	400MΩ
11KV to 33KV	1000V	500MΩ
33KV to 66KV	1000V	600MΩ

What is megger value?

It gives an idea of an insulator's condition. It is measured using an instrument named Megger test capable of impressing D.C. voltage between its two probes, automatically calculating and then displaying the IR value. Megger test being so popular that “Insulation Resistance” and “Megger Test” are synonymously used.

How do you test 11KV transformer?

Induced Over voltage Withstand test (DVDF test) For a 11KV/433V transformer,866 Volts are applied at the 433V winding with the help of a Generator for 1 minute. This induces 22KV on 11KV side. The frequency of the 866V supply is also increased to 100HZ.

What is kVA to kW?

P (power) = I (current) × V (voltage) That means that in DC circuits, 1 kVA is equal to 1 kW. That means that 1 kVA is equal to 1,000 watts. In alternating current (AC) circuits, where kVA to kW conversion is mostly used, the kVA to kW conversion depends on the power factor (PF).

What is difference between KV and kVA?

KV is the voltage. KVA is the product of the voltage and the current. kVA= KV* Amp. KVA is known as the apparent power.