Selection of conductors and insulators, verification of load-bearing structures under the conditions of the dynamic action of short-circuit currents

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 1 General Rules

The choice of electrical apparatus and conductors according to the conditions of a short circuit. Selection of conductors and insulators, verification of load-bearing structures under the conditions of the dynamic action of short-circuit currents

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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1.4.14. The forces acting on rigid busbars and transmitted by them to insulators and supporting rigid structures should be calculated from the highest instantaneous value of the three-phase short circuit current iу, taking into account the shift between the currents in the phases and without taking into account the mechanical vibrations of the busbar structure. In some cases (for example, at limiting design mechanical stresses), mechanical vibrations of tires and tire structures can be taken into account.

Force impulses acting on flexible conductors and insulators, terminals and structures supporting them are calculated from the rms (during the passage time) current of a two-phase fault between adjacent phases. With split conductors and flexible conductors, the interaction of short-circuit currents in conductors of the same phase is determined by the effective value of the three-phase short circuit current.

Flexible conductors must be checked for lashing.

1.4.15. The mechanical forces found by calculation in accordance with 1.4.14, which are transmitted during a short circuit by rigid tires to the support and bushing insulators, should, in the case of using single insulators, not exceed 60% of the corresponding guaranteed values of the least destructive force; with paired support insulators - no more than 100% of the destructive force of one insulator.

When using tires of composite profiles (multi-strip, from two channels, etc.), mechanical stresses are found as an arithmetic sum of stresses from the interaction of phases and the interaction of the elements of each bus with each other.

The highest mechanical stresses in the material of rigid tires should not exceed 0,7 tensile strength according to GOST.

See other articles Section Rules for the installation of electrical installations (PUE).

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