A back to back method for the temperature rise test of prefabricated substations: A case study

In this work a back to back method is presented which allows to develop heating tests of prefabricated secondary substations with a limited number of supplying equipment (an induction regulator and a capacitor bank). The proposed method makes use of the transformer tap changers to create a voltage difference on the medium voltage side. In this way, only an adjunctive low voltage supply is needed. With the proposed test system, the heating tests are developed on a 1000 kVA prefabricated substation. Thanks to the experimental tests, the class of enclosure of the substation and the operating temperature and resistance of the power transformers are determined, according to the recommendations of the standards EN 62271-202 and EN 60076-2. Beside the traditional tests prescribed by the standards, a thermographic analysis of the substation under test is also performed. The simplicity of this analysis suggests its usefulness as pre-compliance test, which can be also performed in manufacturer laboratories.