45results about How to "High protection sensitivity" patented technology

The invention provides a low-resistance grounding system ground protection method based on a zero sequence current projection coefficient and belongs to the field of power distribution network relay protection. For a low-resistance grounding mode power distribution network, projection coefficients of fault line zero sequence current and sound line zero sequence current on neutral-point zero sequence current have great difference no matter how much transition resistance is when a single-phase earth fault happens; thus, the fault characteristics can be utilized to form grounding protection. Theinvention further discloses a calculating method of the zero sequence projection coefficients and a fixed value setting principle of all parameters. The low-resistance grounding system ground protection method disclosed by the invention can ensure that low-resistance grounding and metallic grounding fault protection has good selectivity and reliability; meanwhile, the problem of high-resistance grounding fault protection reliability of a low-resistance grounding system is solved; the low-resistance grounding system ground protection method has a wide actual application prospect.

The disclosed protection method for internal fault of large power transformer comprises: the protector samples the secondary current of current transformers on power transformer sides to obtain current instantaneous value and calculate complex number form of electric values by Fourier algorithm, corrects phase of connection form, and balances amplitude of transformation ratio; then, it calculates the complex number form of negative sequence current according to three-phase ac complex form, and computes negative sequence differential current and break current as the negative sequence differential protection principle to decide asymmetric inside and outside fault and drop out all breakers. This invention also contains exactly the negative sequence differential rate breaking feature and protection criterion, the adjusting means for protection values, the positive sequence current breaking criterion, and the block function for error action protection.

The invention discloses a positive sequence impedance differential protection method with braking characteristic for a power distribution network containing inverter-based distributed generation (IBDG). The method comprises the following steps of acquiring a three-phase current and a three-phase voltage at a protection position to acquire positive sequence impedance; carrying out information exchange between protection at two sides through an optical fiber Ethernet or a wireless communication network; carrying out calculation of action impedance and braking impedance by a local-side protection device after acquiring positive sequence impedance information and positive sequence current amplitude information which are measured by opposite-side protection; and judging whether a protected region is a fault section or not according to an action criteria with the baking characteristic. The method is applicable to circuit protection between a bus of a substation outlet of an active power distribution network and a distributed power supplies and between the distributed power supplies, the influence of fault characteristic of IBDG and through load current on protection performance can be dealt with, and the influence of a branch load on the judgment of a fault direction during an external fault can be prevented duo to the adoption of the action criteria; and moreover, data synchronism between two ends is not needed, the requirement on communication is relatively low, and the method has relatively high transition resistance resistant capability.

The invention discloses an internal grounding fault protection method of AC and DC filter capacitors. The steps are: real-time sampling of filter head-end current, tail-end current and unbalanced current; adopting the differential protection principle of head-end current and tail-end current ( P1); using the unbalanced protection principle (P2) of unbalanced current; performing logical AND operation on the action results of the two protection principles (P1 and P2), and obtaining the protection method of this patent. This method uses the principle of combining filter differential protection and filter unbalance protection to detect the ground fault inside the filter capacitor, avoiding the filter failure caused by reducing the differential protection setting or reducing the unbalance protection setting to increase the protection sensitivity. Protect the risk of misoperation and ensure the safe operation of DC equipment.

The invention discloses a relay protection method and device for quickly cutting off the fault of empty charging in the dead zone of a transformer, including the following control process: the circuit breakers on each side of the transformer are in the opening position, and the current on one side changes from no flow to flow and When the circuit breaker on this side is turned from the minute position to the close position, the transformer is in the state of empty charging from this side; the transformer is empty charging, and the dead zone protection is opened for T seconds; the circuit breaker on a non-empty charging side of the transformer is in the opening position; The maximum phase current of the three-phase current on the charging side is greater than the current setting value, or the zero-sequence current is greater than the zero-sequence setting value, or the negative-sequence current is greater than the negative-sequence setting value; when the above conditions are met, the transformer differential protection will be activated after a delay of t1 The tripping action exits the circuit, trips the circuit breakers on each side of the transformer, and quickly removes the fault in the dead zone. The invention avoids the influence of inrush current when the transformer is empty-charging, has nothing to do with the setting value of the backup protection of the transformer, the type of the transformer and the type of the fault, and greatly shortens the removal time of the fault in the dead zone.

The invention discloses an ocean nuclear power platform power grid grounding fault line selection protection method and an ocean nuclear power platform power grid grounding fault line selection protection system, belonging to the field of ocean nuclear power platform power grid protection. The ocean nuclear power platform power grid grounding fault line selection protection method comprises the following steps of: when a single-phase earth fault occurs in the system, if a fault current amplitude is higher than a given threshold, keeping a neutral point in a high-resistance grounding mode, selecting an optimal wavelet basis and a decomposition scale based on a maximum energy joint entropy ratio, and performing earth fault line selection by utilizing a wavelet transformation method based ona modulus maximum value; when a high-transition resistance grounding fault occurs in the system, switching the neutral point to a small-resistance grounding mode, and constructing a branch zero-sequence current and fault phase voltage break variable phase comparison line selection protection method based on features of the high-resistance grounding fault to perform grounding fault line selection.The ocean nuclear power platform power grid grounding fault line selection protection method can be effectively matched with the operation mode and the grounding fault features of an ocean nuclear power platform power system, is high in line selection accuracy rate, is suitable for various grounding fault modes possibly happening to the platform system, and effectively improves the safety defensecapacity of the ocean nuclear power platform.

The invention discloses transmission line self-adaptive single-end transient protection based on transition resistance and fault angle reductions. When the transmission line is in short circuit, a large amount of high-frequency signals produced by a fault are transmitted to two ends of the transmission line; and owing to affect of earth distributed capacitance of a bus, the high-frequency signals are obviously reduced via the bus, high-frequency component close to the fault side of the bus is invariably higher than that of the fault side of the bus, and the transition resistances and fault angles have a great affect on the high-frequency component produced by the fault. Relative reduction formulas and parameters are selected according to the type of the fault, the transient amount reduction is performed corresponding to the transition resistances and the fault angles, and protective criterion is constructed according to the reduction transient amount. According to the principle, fault feature amount with both directional elements and number comparing functions are constructed on the basis of the transient amount difference of reduction of two sides of the bus to determine a zone the fault occurs in. By the aid of the scheme, the affect to the single-end transient protection by the transition resistances and fault angle is eliminated to a maximum extent. Fault feature differences between the forward direction and reverse direction and inner zone and external zone are obvious, reliability and flexibility are high, the overall length of a line can be protected, protecting areas are twice that of traditional protecting areas, and requirements for the distributed capacitance of the bus are low.

A small current neutral grounding fault location method based on the direction of transient state reactive power is characterized in that change of voltage or current serves as a failure starting condition, and after the starting, the zero sequence voltage is taken as the participating voltage if a detection point can be used for detecting the zero sequence voltage and if not, the following steps are performed: 1, confirming the fault phase as per characteristics of three transient state line voltages, and 2, confirming the transient state line voltage including the fault message as per the type of the fault phase, taking the transient state line voltage as the participating voltage, confirming the characteristic frequency range, and further building a digital filter to filter the participating voltage and the zero sequence current signal, so as to obtain the component within the characteristic frequency range; and then confirming the direction of the reactive power of all the detection points through utilizing the components of participating voltage and the zero sequence current within the characteristic frequency range, so as to further confirm the fault section. According to the invention, the transient voltage and current signals as well as zero sequence voltage and line voltage are utilized at the same time, the positioning reliability is higher, the adaptability is stronger, quick direction protection for ground fault of all the voltage classes is applicable at the same time, and the protection speed and reliability are taken into consideration.

A single-phase grounding protective method of the fault current component phase ratio type generator's stator, belongs to electric technique field. The method is as follows: adopt half in quadrature wavelet as start tool; collect the zero sequence voltage component at generator terminal and neutral point side as reference electric quantity, the voltage transformer's wiring form adopt standard wiring; the modulus maximum's judging through the wavelet analyzing by which the zero sequence voltage including fundamental wave zero sequence voltage and thrice harmonic zero sequence voltage, is taken as start criterion; according to whether the phase angle ratio of the thrice harmonic voltage increment at the terminal and neutral point side meet the request, judge the whither the generator takes place single phase grounding fault at the interior of stator.