Full Description

This part of IEC 62271 specifies the service conditions, rated characteristics, general structural requirements and test methods of enclosed high-voltage prefabricated substations. These prefabricated substations are cable-connected to AC high-voltage networks with an operating voltage up to and including 52 kV and power frequencies up to and including 60 Hz. They can be manually operated from inside (walk-in type) or from outside (non-walk-in type). They are designed for outdoor installation at locations with public accessibility and where protection of personnel is provided.

These prefabricated substations can be situated at ground level or partially or completely below ground level. The last are also called "underground prefabricated substations".

In general, two types of prefabricated substations are considered in this document:
- high-voltage switchgear prefabricated substations;
- high-voltage/low-voltage transformer prefabricated substations (step-up and step-down).
A high-voltage switchgear prefabricated substation comprises an enclosure containing in general the following electrical components:
- high-voltage switchgear and controlgear;
- auxiliary equipment and circuits.
A high-voltage/low-voltage transformer prefabricated substation comprises an enclosure containing in general the following electrical components:
- power transformer(s);
- high-voltage and low-voltage switchgear and controlgear;
- high-voltage and low-voltage interconnections;
- auxiliary equipment and circuits.

However, relevant provisions of this document are applicable to designs where not all these electrical components exist (for example, a prefabricated substation consisting of power transformer and low-voltage switchgear and controlgear).

The listed electrical components of a high-voltage/low-voltage transformer prefabricated substation can be incorporated in the prefabricated substation either as separate components or as an assembly type CEADS according to IEC 62271-212.

This document covers only designs using natural ventilation. However, relevant provisions of this document are applicable to designs using other means of ventilation except the rated power of the prefabricated substation and associated class of enclosure (see 5.101), the continuous current tests (see 7.5) and all temperature rise related requirements, which would need an agreement between manufacturer and user.

NOTE 1 IEC 61936-1 [1]1 provides general rules for the design and erection of high-voltage power installations. As well, it specifies additional requirements for the external connections, erection and operation at the place of installation of high-voltage prefabricated substations compliant with IEC 62271-202, which are regarded as a component of such installation. Non-prefabricated high-voltage substations, are generally covered by IEC 61936-1 [1].

NOTE 2 High-voltage switchgear prefabricated substations can include instrument transformers, according to IEC 61869 (all parts). These substations are not high-voltage/low-voltage transformer prefabricated substations.