CLC/TR 50422:2003

Guide for the application of the European Standard EN 50160 CLC/TR 50422:2003

Publication date:   Apr 21, 2010

Scope

It is important to note that the scope of the standard is confined to the electricity supplied at the supply terminals, and does not deal with the supply system or the customer´s installation or equipment. The diagram below in Figure 1 illustrates the point which is defined in EN 50160 as “the supply terminals” and also the relationship between the impulse withstand requirements of the supply terminals, the customer’s installation and the customer’s electrical equipment. The appropriate categories of impulse voltage withstand for each zone are also highlighted. It should be stressed that the supply terminals, referred to in both the standard and this application guide, and the origin of the installation, referred to in both IEC 60664-1, Insulation coordination for equipment within low-voltage systems [5], and IEC 60364-4-44, Electrical Installations of buildings – Part 4 Protection for Safety Chapter 44 Protection against overvoltages (HD 384-4-443) [6], are one and the same point.
As the standard is intended to deal only with the characteristics of the voltage at specified points on the public distribution networks, it does not deal directly with the characteristics of networks themselves, such as short circuit power. Clearly, however, the network characteristics will have an effect upon the magnitude of several of the phenomena described by the standard.
The standard is applicable only under normal operating conditions of the supply system. This includes also the correct operation of protection devices in the case of a fault in the network (blowing of a fuse, operation of a circuit-breaker etc.); the operation of loads agreed between customer and distribution network operator (DNO – see clause 2.3 below) and changes in network configuration.
When energy is supplied to the public networks from small private generators, it is important to keep the level of disturbances within acceptable limits. In this context private generation is in the same position as any customer’s installation and therefore has to comply with the related emission standards and agreed limits for the voltage supplied. As such the voltage supplied from the generator must comply with the requirements of EN 50160.