1.1 Scope
This standard applies to three-pole units for public and industrial distribution systems which are functional assemblies of switches including switch-disconnectors and current-limiting fuses designed so as to be capable of
——breaking, at the rated recovery voltage, any current up to and including the rated short-circuit breaking current,
——making, at the rated voltage, circuits to which the rated short-circuit breaking current applies.
It does not apply to fuse-circuit-breakers, fuse-contactors, combinations for motor-circuits or to combinations incorporating single capacitor bank switches.
In this standard, the word "combination" is used for combination in which the components constitute a functional assembly. Each association of a given type of switch and a given type of fuse defines one type of combination.
In practice, different types of fuses may be combined with one type of switch, which gives several combinations with different characteristics, in particular concerning the rated currents. Moreover, for maintenance purposes, the user should know the types of fuses that can be associated to a given switch without impairing compliance to this standard, and the corresponding characteristics of the so-made combination.
A switch-fuse combination is then defined by its type designation and a list of selected fuses is defined by the manufacturer, the so-called "reference list of fuses". Compliance with this standard of a given combination means that every combination using one of the selected fuses is proven to be in compliance with this standard. The fuses are incorporated in order to extend the short-circuit breaking rating of the combination beyond that of the switch alone. They are fitted with strikers in order both to open automatically all three poles of the switch on the operation of a fuse and to achieve a correct operation at values of fault current above the minimum melting current but below the minimum breaking current of the fuses. In addition to the fuse strikers, the combination may be fitted with either an over-current release or a shunt release.
Note 1: In this standard the term "fuse" is used to designate either the fuse or the fuse-link where the general meaning of the text does not result in ambiguity.
Note 2: In this standard, "switch-fuse combination" and "combination" are used to designate "high-voltage alternating current switch-fuse combinations" where the meaning of the text does not result in ambiguity.
This standard applies to indoor or outdoor combinations designed with nominal voltages above 3kV up to and including 35kV for use on three-phase alternating current systems of 50Hz.
Fuses are covered by GB 15166.2.
Switches, including their specific mechanism, should be in accordance with GB 3804 except for the short-time current and short-circuit making requirements where the current-limiting effects of the fuses are taken into account.
Earthing switches forming an integral part of a combination are covered by GB 1985.
Contents
Foreword I
1 General
2 Normal and Special Service Conditions
3 Terms and Definitions
4 Ratings
5 Design and Construction
6 Type Tests
7 Routine Tests
8 Guide for the Selection of Switch-fuse Combinations
9 Information to Be Given with Enquiries, Tenders and Orders
10 Rules for Transport, Storage, Installation, Operation and Maintenance
11 Safety
Annex A (Informative) Example of the Coordination of Fuses, Switch and Transformer
Annex B (Normative) Procedure for Determining Transfer Current
