IEC 60071-2011 pdf free download – Insulation co-ordination – Part 1: Definitions, principles and rules.
This part of lEC 60071 applies to three-phase a.c. systems having a highest voltage forequipment above 1 kv. lt specifies the procedure for the selection of the rated withstandvoltages for the phase-to-earth，phase-to-phase and longitudinal insulation of the equipmentand the installations of these systems. it also gives the lists of the standard withstandvoltages from which the rated withstand voltages should be selected.
This standard recommends that the selected withstand voltages should be associated with thehighest 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 valuesof their withstand voltages may be different from the standard rated withstand voltages.
The apparatus committees are responsible for specifying the rated withstand voltages and thetest procedures suitable for the relevantequipment taking into consideration therecommendations of this standard.
NOTE In IEC 60071-2,Application Guide, all rules for insulation co-ordination given in this standard are justifiedin detail，in particular the association of the standard rated withstand voltages with the highest voltage forequipment. When more than one set of standard rated withstand voltages is associated with the same highestvoltage for equipment,guidance is provided for the selection of the most suitable set.
Normative references
The following referenced documents are indispensable for the application of this document.For dated references, only the edition cited applies.For undated references, the latest editionof the referenced document (including any amendments) applies.
lEC 60038:2002,IEC standard voltages
IEC 60060-1:1989，High-voltage test techniques – Part 1: General definitions and testrequirements
IEC 60071-2,Insulation co-ordination – Part 2: Application guide
IEC 60099-4，Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c.systems
IEC 60507,Artificial pollution tests on high-voltage insulators to be used on a.c. systems
IEC 60633，Terminology for high-voltage direct current (HvDC) transmission
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 andovervoltages which can appear on the system for which the equipment is intended and takinginto account the service environment and the characteristics of the available preventing andprotective devices
[IEC604-03-08:1987, modified]
NOTE By “dielectric strength” of the equipment, is meant here its rated or its standard insulation level as definedin 3.35 and 3.36 respectively.
3.2
external insulation
distances in atmospheric air，and the surfaces in contact with atmospheric air of solidinsulation of the equipment which are subject to dielectric stresses and to the effects ofatmospheric and other environmental conditions from the site，such as pollution， humidity,vermin, etc.
[IEC 604-03-02:1987,modified]
NOTE External insulation is either weather protected or non-weather protected,designed to operate inside oroutside closed shelters respectively-
3.3
internal insulation
internal distances of the solid， liquid, or gaseous insulation of equipment which are protectedfrom the effects of atmospheric and other external conditions
[IEC 604-03-03:1987]
3.4
self-restoring insulation
insulation which，after a short time，completely recovers its insulating properties after adisruptive discharge during test
[IEC 604-03-04:1987, 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 adisruptive discharge during test
[IEC 604-03-05:1987,modified]
NOTEThe definitions of 3.4 and 3.5 apply only when the discharge is caused by the application of a test voltageduring a dielectric test.However,discharges occurring in service may cause a self-restoring insulation to losepartially or completely its original insulating properties.IEC 60071 pdf download.