IEC 60071-1 pdf download

IEC 60071-1 pdf download.Insulation co-ordination – Part 1: Definitions, principles and rules
1 Scope
This part of IEC 60071 applies to three-phase a.c. systems having a highest voltage for equipment above 1 kV. It specifies the procedure for the selection of the rated withstand voltages for the phase-to-earth, phase-to-phase and longitudinal insulation of the equipment and the installations of these systems. It also gives the lists of the standard withstand voltages from which the rated withstand voltages should be selected. This standard recommends that the selected withstand voltages should be associated with the highest voltage for equipment. This association is for insulation co-ordination purposes only. The requirements for human safety are not covered by this standard. Although the principles of this standard also apply to transmission line insulation, the values of their withstand voltages may be different from the standard rated withstand voltages. The apparatus committees are responsible for specifying the rated withstand voltages and the test procedures suitable for the relevant equipment taking into consideration the recommendations of this standard. NOTE In IEC 60071 -2, Application Guide, all rules for insulation co-ordination given in this standard are justified in detail, in particular the association of the standard rated withstand voltages with the highest voltage for equipment. When more than one set of standard rated withstand voltages is associated with the same highest voltage for equipment, guidance is provided for the selection of the most suitable set.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. 3.1 insulation co-ordination selection of the dielectric strength of equipment in relation to the operating voltages and overvoltages which can appear on the system for which the equipment is intended and taking into account the service environment and the characteristics of the available preventing and protective devices [IEC 604-03-08:1 987, modified] NOTE By “dielectric strength” of the equipment, is meant here its rated or its standard insulation level as defined in 3.35 and 3.36 respectively. 3.2 external insulation distances in atmospheric air, and the surfaces in contact with atmospheric air of solid insulation of the equipment which are subject to dielectric stresses and to the effects of atmospheric and other environmental conditions from the site, such as pollution, humidity, vermin, etc. [IEC 604-03-02:1 987, modified] NOTE External insulation is either weather protected or non-weather protected, designed to operate inside or outside closed shelters respectively. 3.3 internal insulation internal distances of the solid, liquid, or gaseous insulation of equipment which are protected from the effects of atmospheric and other external conditions [IEC 604-03-03:1 987] 3.4 self-restoring insulation insulation which, after a short time, completely recovers its insulating properties after a disruptive discharge during test [IEC 604-03-04:1 987, modified] NOTE Insulation of this kind is generally, but not necessary, external insulation 3.5 non self-restoring insulation insulation which loses its insulating properties, or does not recover them completely, after a disruptive discharge during test [IEC 604-03-05:1 987, modified] NOTE The definitions of 3.4 and 3.5 apply only when the discharge is caused by the application of a test voltage during a dielectric test. However, discharges occurring in service may cause a self-restoring insulation to lose partially or completely its original insulating properties. 3.6 insulation configuration terminal any of the terminals between any two of which a voltage that stresses the insulation can be applied. The types of terminal are: (a) phase terminal, between which and the neutral is applied in service the phase-to-neutral voltage of the system; (b) neutral terminal, representing, or connected to, the neutral point of the system (neutral terminal of transformers, etc.); (c) earth terminal, always solidly connected to earth in service (tank of transformers, base of disconnectors, structures of towers, ground plane, etc.).