Abstract: A line current iM(k0) of an M side of a first direct-current transmission line is collected at a moment k0. A line current iM(k0?ts) thereof is collected at k0?ts. At a moment k0, a differential value diM(k0) of a current of the side of the first direct-current transmission line is calculated according to the line current iM(k0) and the line current iM(k0?ts). It is determined whether the differential value diM(k0) of the current meets a protection enabling criteria. If so, direct-current protection for the M side of the first direct-current transmission line is enabled. A line current iM(j) of the M side of the first direct-current transmission line is collected at a moment j. A line current iM(j?ts) thereof is collected at a moment j?ts. A differential value diM(j) of the current of the M side of the first direct-current transmission line at the moment j is calculated according to the line current iM(j) and the line current iM(j?ts).

Abstract: A line double-end steady-state quantity distance measuring method and system based on an amplitude-comparison principle. According to the method and system, voltage values and current values of both sides of a line before and after a fault are collected (102), a voltage variable quantity and a current variable quantity of both sides of the line are calculated (103), and after a voltage phasor value and a current phasor value are determined according to the voltage variable quantity and the current variable quantity (104), the position of a short-circuit point is determined by performing iterative calculation on the voltage of the short-circuit point. The method is simple in principle, and can accurately recognize a fault point, achieving precise distance measurement of lines.

Abstract: Disclosed are a direct-current transmission line protection method and system based on pure current characteristics.

Abstract: Disclosed are a relay protection system risk assessment and fault positioning method and apparatus, and a device and a medium.

Abstract: A perforating device includes a release sub, a rotating segment, a first centralizer, a braking segment, a casing collar locator, a traction mechanism, a second centralizer, a flex joint, a power supply segment, a shock absorber, a perforator, and a tail segment, which are in threaded connection sequentially to each other. The first joint assembly includes a first joint, a guide key, a connecting sleeve including a locking groove, a second joint, and an outer pipe; the first joint of the first joint assembly is in threaded connection to the cable bridle, and the second joint is in threaded connection to the outer pipe. The connecting sleeve is disposed inside the outer pipe and is connected to the first joint through the guide key. The second joint assembly includes a plurality of locking claws, a third joint, and a head.

Abstract: The invention relates to a self-adaptive positive-sequence current quick-break protection method for a petal-shaped power distribution network trunk line. The method comprises the following steps: step 1, calculating a positive-sequence voltage phasor and a positive-sequence current amplitude at a protection installation position when a fault occurs, acquiring and storing a positive sequence impedance value of a protected line; judging a fault type, and judging a fault direction; step 2, when a fault direction element judges that a fault occurs in the forward direction, selecting a self-adaptive current quick-break protection setting formula according to the fault type, and when positive sequence current measured by protection is larger than a protection setting value, judging that the protected line has a short-circuit fault, and making a circuit breaker trip quickly.

Abstract: A perforating device includes a release sub, a rotating segment, a first centralizer, a braking segment, a casing collar locator, a traction mechanism, a second centralizer, a flex joint, a power supply segment, a shock absorber, a perforator, and a tail segment, which are in threaded connection sequentially to each other. The first joint assembly includes a first joint, a guide key, a connecting sleeve including a locking groove, a second joint, and an outer pipe; the first joint of the first joint assembly is in threaded connection to the cable bridle, and the second joint is in threaded connection to the outer pipe. The connecting sleeve is disposed inside the outer pipe and is connected to the first joint through the guide key. The second joint assembly includes a plurality of locking claws, a third joint, and a head.