Computing method and verifying device and method for current carrying capacity of flexible mineral insulated cable

Abstract

The invention discloses a computing method and a verifying device and method for the current carrying capacity of a flexible mineral insulated cable. According to a steady-state thermal circuit model, a measuring device and method for the thermal resistivity of mica tape materials and warping tape are designed and built; according to the insulation thermal resistance of multilayer lapping, the influence of air gaps on the thermal resistance is analyzed, a mica tape / air gap series thermal resistance model is built, the thermal resistance is normalized, the concept and the computing method for the filling coefficients and the lapping equivalent radius are provided, and the computing method for the multilayer-lapping insulation thermal resistance is built; the influence of air gaps between corrugated copper sheaths and a cabling lapping layer on the inner protecting thermal resistance is analyzed, the computing method for the front equivalent radius and the back equivalent radius of the corrugated copper sheaths is provided, and the computing method for the composite inner protecting thermal resistance formed by cabling lapping and the air gaps is built; the experiment device for verifying the current carrying capacity is designed and built. The computing method and the verifying device and method have the advantages of being simple in structure, accurate in testing and convenient to operate.

Description

technical field [0001] The invention relates to the technical field of design and manufacture of low-voltage fire-resistant cables, and more specifically, to a calculation method, verification device and method for the ampacity of flexible mineral insulated cables. Background technique [0002] In recent years, a series of fire accidents in the field of civil buildings have brought serious loss of life and property to the country and the people, and have also aroused the whole society's attention to building fire prevention. Electrical fires account for a large proportion of fire accidents, and wires and cables are an important source of fires that cause electrical fires. [0003] From the perspective of fire prevention, three levels of requirements are put forward for wires and cables: (1) The cable does not prolong combustion in case of fire, and the flame can self-extinguish; (2) Release less dense smoke when burning, and try not to release toxic halogen gas; (3) It can ...

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Problems solved by technology

[0005] However, there is still a lack of research on the calculation method of the current carrying capacity of flexible mineral insulated cables, which seriously affects customer selection and product promotion and application. There are three main reasons for this problem: (1) flexible mineral insulated cables use multi-layer The insulation structure of the wrapping cannot be calculated by applying the calculation formula of the extruded insulation to calculate the insulation thermal resistance; (2) the current research on the synthetic mica tape for wrapping is mainly focused on the high temperature insulation performance, and there is a lack of research and related data on heat conduction; ( 3) A large part of flexible mineral insulated cables use bare copper sheaths, which makes it difficult to calculate the external air thermal resistance

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