How is your Prolec GE Transformer Tested?

October 2017, by Elisa Zambrano Gómez, Product Technology Leader

Prolec GE implements strict design and manufacturing standards for our products to be highly reliable and to have a life span of more than 20 years. Additionally, each of our distribution transformers undergo a series of tests that must have a satisfactory result before they can leave our facilities, complying with all the applicable standards.

After assembling the core and coil, the first tests take place. Turn ratio is measured on the rated voltage connection and on all tap positions listed on the nameplate. This test checks if the turn ratio between the high and low voltage is correct and meets the standard. The polarity and phase relation tests on the rated voltage connection are completed to make sure the windings comply with the additive or subtractive configuration requested by our customer.

When concluding the assembly, the transformer undergoes a leak test to verify that there are no leaks in the tank. This test verifies that the tank is able to withstand overpressures that may be present during regular transformer operations. The tank must not show any visible permanent damage once the pressure is relieved.

After this, the preliminary electrical tests are carried out, these tests include resistance measurements of all windings on the rated voltage tap, winding insulation resistance, and insulation power factor, and capacitance. These tests verify the quality and integrity of the insulation system. A high-quality processing and handling of the insulation materials lead to low humidity concentrations, and therefore a longer life span for the equipment.

With the parametric tests, the basic transformer parameters are measured. One of them is the no load test where the no load losses are measured, as well as the excitation current at 100% of the rated voltage, measurements are 110% are also optional. Then, besides the rated voltage, we simulate the rated current at rated frequency in our laboratories and measure the load losses as well as the impedance voltage. With this information, the overall efficiency can be calculated.

Finally, we perform the dielectric tests, including routine impulse, induced voltage and applied voltage. These tests verify the dielectric strength of the insulating system including insulation between windings, within winding layers, and between the windings and the tank.

There are additional tests that are only executed for prototypes, according to the country’s corresponding standards. These tests are usually destructive so they are just enforced in one or a few distribution transformers such as the short circuit capability test, temperature rise and lighting impulse over 100%.

At Prolec GE, we also offer complementary tests that clients may pre-order, such as partial discharge test, audible sound level, dissolved gas oil analysis and zero phase sequence impedance voltage.

Before the distribution transformers are shipped to the customer, each one of them must be subject and comply with all the tests required by the applicable standards, in addition to our internal manufacturing and quality protocols. Therefore, when you buy a transformer form Prolec GE you can be sure you are getting a high-quality product.