Abstract: Disclosed are a device and method for detecting defects of a high-voltage cable cross-bonded grounding system. The method comprises: selecting a protective grounding box of a cross-bonded grounding system, respectively connecting a signal excitation coupler to A-phase, B-phase and C-phase coaxial cables of the protective grounding box, selecting a stable signal with a frequency different from a power frequency or a field interference frequency, and testing effective current values and phases responded by the A-phase, B-phase and C-phase coaxial cables when the stable signal with the frequency F1 is injected into the A-phase, B-phase and C-phase coaxial cables of the protective grounding box in a coupled manner; and obtaining resistances and inductances of branch circuits of the cable cross-bonded grounding system by calculation according to measurement data, and determining if the cable cross-bonded grounding system has a connection defect.

Abstract: A flat drill bit includes a stem body, a cut flute part provided axially from an end of the stem body and being generally flat-shaped, and a threaded guiding part provided axially from an end of the cut flute part. The cut flute part includes two longitudinal wings which are configured to be rotationally symmetrical to each other about a longitudinal central axis (O) of the flat drill bit. Each longitudinal wing is formed with a cutting edge at the end of the cut flute part from which the threaded guiding part extends. A rotating trajectory profile caused by the cutting edge when the flat drill bit rotates is inclined towards the stem body and is at an angle (a) relative to the longitudinal central axis (O), and the angle (a) is in a range between 84° and 86°.

Abstract: A combined platform for testing fireproof materials for cables includes a main frame for providing operating space; an air circulation system including a fresh air supply unit for supplying fresh air into the operating space and an exhaust gas treatment unit for treating the gas in the operating space under set conditions; an open flame system for providing an open flame for testing cables; a water circulation system for supplying water at least to the exhaust gas treatment unit and the operating space; and a control system for collecting at least the temperature and gas concentration in the operating space, and performing process control based on the collected results. The actual working conditions of scenarios such as fire-resistant cable tunnels and fire-resistant cable trenches can be simulated, and multiple tests such as combustion performance test and physical and chemical performance test can be carried out under various working conditions.

Abstract: A flat drill bit includes a stem body, a cut flute part provided axially from an end of the stem body and being generally flat-shaped, and a threaded guiding part provided axially from an end of the cut flute part. The cut flute part includes two longitudinal wings which are configured to be rotationally symmetrical to each other about a longitudinal central axis (O) of the flat drill bit. Each longitudinal wing is formed with a cutting edge at the end of the cut flute part from which the threaded guiding part extends. A rotating trajectory profile caused by the cutting edge when the flat drill bit rotates is inclined towards the stem body and is at an angle (a) relative to the longitudinal central axis (O), and the angle (a) is in a range between 84° and 86°.