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The utility model discloses a lightning protection mechanism of a power distribution cabinet for power transmission, and belongs to the technical field of power transmission equipment. The device mainly comprises a synchronous driving unit, the synchronous driving unit is installed at the top of the power distribution cabinet and drives a retracting and releasing unit to rotate at the top of the power distribution cabinet, the retracting and releasing unit comprises a worm, a worm gear and a rotating rod, the worm is in meshed connection with the side wall of the worm gear, and the rotating rod is in key connection with the interior of the worm gear. One end of each rotating rod is rotationally connected to the inner side wall of the power distribution cabinet through a bearing seat, the other end of each rotating rod is fixedly provided with a lightning protection unit, and the synchronous driving unit is matched with the retracting and releasing unit, so that flexible retracting and releasing of the lightning protection units are achieved. In no thunder and lightning weather, the lightning protection unit can be recycled into the power distribution cabinet, external environment erosion is reduced, and the service life of the lightning rod, the insulating base and other components is prolonged.

The present application relates to a kind of synergistic flame-retardant low melting point polyester chip for polyester sheath-core and its preparation method, the melting point of product is reduced by introducing part of asymmetric isomer of terephthalic acid in esterification process, while introducing part of symmetric structure alcohol with small difference with ethylene glycol, the chain regularity is less damaged, a small amount of introduction will not significantly damage the crystallization ability of product while reducing the melting point. After esterification, by means of blending and co-melting and alcoholysis repolymerization, flexible chain segment (‑O‑(CH2)4‑O‑) with fast crystallization speed is introduced to improve the crystallization performance of product, and finally the modified synergistic flame retardant is added. Nitrogen, phosphorus and silicon elements are introduced into the product chain segment during polycondensation reaction, and a triple protection system covering condensed phase, gas phase and interface is formed through the multidimensional complementary action of the three elements during combustion. Through the above steps, polyester chip for polyester sheath-core with high flame retardancy, low melting point and high crystallinity is finally synthesized.

This invention belongs to the field of chemical synthesis technology, specifically relating to a method for preparing 2-methyl-1H-phenylenehydride. The method includes the following steps: using acetic acid and 1,8-diaminonaphthalene in a molar ratio of 2.5~5.5:1 as reactants, and water as the reaction medium, at 100℃~185℃, one amino group of 1,8-diaminonaphthalene undergoes a condensation reaction with the carboxyl group of acetic acid, removing one water molecule to obtain a product intermediate containing an amide bond. The other amino group on the intermediate undergoes an intramolecular cyclization reaction with the carbonyl group in the amide bond, removing one water molecule to obtain a crude product. The crude product is then purified to obtain the 2-methyl-1H-phenylenehydride. The 2-methyl-1H-phenylenehydride prepared using the method of this invention can achieve a purity of up to 98%.