Thermal design of MV/LV substations

Thermal design

Among the type tests listed in the IEC 62271-202 standard, the temperature-rise test is no doubt one of the major tests used to validate the performance of prefabricated MV/LV substation architectures.

Thermal design of substations has often involved the use of one of two approaches:

• Practical, i.e. by iteration: trials,
• Measurement, corrections calculations based on analytical formulas for buildings in which many heat-transfer coefficients are fixed arbitrarily and are liable to produce significant variations in the results

Thermal modeling of all of these systems can make it possible to optimize the substation and, with the model, meet the requirements of a large number of configurations by varying the different parameters of the model.

Type tests

For type tests, the manufacturer is required to test the most severe configuration or even demonstrate the level of severity to the certification authority. It can then be claimed that the test covers an entire range. Customers often ask for existing substation offers to be adapted to meet their local requirements.

Such power, architecture or design changes often have an impact on the thermal performance of the substation.

The new configuration is seldom requalified by testing. In general, the thermal performance of the new design is simply extrapolated from the basic configuration already tested, using empirical formulas.