Abstract: A method for detecting abnormal direct current voltage measurement in a modular multilevel converter high voltage direct current transmission system is provided. In the method, a valve group voltage at a detection pole is obtained, voltages at voltage measurement points at the detection pole are collected, and comparison and determination are performed based on the actual arrangement of the voltage measurement points, and then whether an abnormal measurement occurs at each of the voltage measurement points is determined.

Abstract: A preparation method of an expansive polymer grouting material for treating high-pressure large-flow-rate karst water inrush includes: 1) adding a crosslinking agent to acrylic acid; then adding a polymer water-absorbent resin comonomer and performing a polymerization reaction to obtain a precursor; 2) adding an initiator to the precursor obtained in step 1), heating the mixture, performing a reaction to obtain a hydrogel, and grinding the hydrogel to obtain a primary polymer water-absorbent resin; 3) spraying a surface crosslinking agent onto a surface of the primary polymer water-absorbent resin obtained in step 2), and drying the product; and 4) preparing a suspension from an inorganic water conducting agent, spraying the suspension onto the product obtained in step 3), and performing drying to obtain the expansive polymer grouting material.

Abstract: A preparation method of an expansive polymer grouting material for treating high-pressure large-flow-rate karst water inrush includes: 1) adding a crosslinking agent to acrylic acid; then adding a polymer water-absorbent resin comonomer and performing a polymerization reaction to obtain a precursor; 2) adding an initiator to the precursor obtained in step 1), heating the mixture, performing a reaction to obtain a hydrogel, and grinding the hydrogel to obtain a primary polymer water-absorbent resin; 3) spraying a surface crosslinking agent onto a surface of the primary polymer water-absorbent resin obtained in step 2), and drying the product; and 4) preparing a suspension from an inorganic water conducting agent, spraying the suspension onto the product obtained in step 3), and performing drying to obtain the expansive polymer grouting material.

Abstract: A karst channel type water inrush efficient-blocking ultra-high expansion grouting material, preparation, methods and application thereof, the grouting material includes macromolecule polymer particles A and a cross-linking solidifying fluid B, wherein the macromolecule polymer particles A are an inlaid type core-shell structure, primary macromolecule water-absorbent resin serves as an inner core, part of a gelling catalyzer is attached to an the inner core surface forming a shell, and the gelling catalyzer permeates the inner core forming an inlaid structure; before use, the macromolecule polymer particle A and the cross-linking solidifying fluid B are stirred; and then obtained mixed liquid is used as the grouting material to be injected into a fracture of a rock mass fracture zone.