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

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.

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.

The invention discloses a high-speed railway supply arm shunt tripping protection method based on impedance characteristics. The method is realized through impedance protection elements distributed in a substation, an AT station and a subarea station in a scattered mode and through a communication network, wherein the quadrangular operation characteristics are adopted for the impedance protection elements. Each impedance protection element can transmit shunt tripping instructions to other impedance protection elements or receive the shunt tripping instructions from other impedance protection elements on the same supply arm through the communication network to rapidly isolate a fault supply arm. The impedance protection elements of the substation and the impedance protection elements of the AT station jointly protect all power supply sections between the substation and the AT station. The impedance protection elements of the AT station and the impedance protection elements of the subarea station jointly protect all power supply sections between the AT station and the subarea station. When a fault of any impedance protection element is detected, a breaker of the fault supply arm in the station is tripped off, a shunt tripping instruction is transmitted to the other impedance protection elements on the same supply arm, the other impedance protection elements receive the shunt tripping instruction and then trip off the corresponding breakers, and consequently the fault supply arm is rapidly isolated, and power supply of the other supply arm which is connected with the fault supply arm in parallel can not be influenced.

The invention relates to a high-resistance grounding protection method for high voltage circuit, which belongs to relay protection field. The method is: the wavelet function is used as analysis tool; the mother line triphase voltage, circuit triphase current and zero series voltage and current are used as reference quantity of electricity, the connection way between the voltage mutual inductor and the current mutual inductor uses standard connection; the mold maximal value of triphase current and zero series current after wavelet analysis is used as starting device by means of 'or'; the mold maximal value of the line current or zero series current after wavelet analysis is used as starting element; the mold maximal value of the triphase other line voltage is used as the rule of interference resisting; finds out the grounding failure phase according to if the mold maximal value character is consistent or not; the zero series current and the voltage polarity are used as direction judgment accordance. The invention can judge if there has single-phase high-resistance grounding failure in the electric line, it has direction performance, and uses the mother line voltage as interference resisting accordance, it has a high protection sensitivity and reliability.

The invention relates to a turn-to-turn fault protection method of a high voltage shunt reactor. The method comprises the following steps: judging the start of protection; judging the operation of protection after the start of protection; judging whether the current at the head end of reactor is greater than the threshold value of a high fixed value when the judging condition of protection operation is satisfied; if the current is greater than the threshold value, performing instantaneous operation of turn-to-turn fault protection; otherwise, delaying operation of turn-to-turn fault protection. The invention identifies the serious fault and the weak fault in the region by the magnitude of the head-end current, ensures the quick operation of the turn-to-turn protection when the serious fault occurs in the region, improves the protection sensitivity of the reactor when the turn-to-turn short circuit and the single-phase ground fault occur, and further improves the reliability of the protection device.

The method comprises: processing fiber differential signals from master machine and slave machine side; the slave machine sends out the message format, and the transmitted data is the unprocessed real time sampling point data, the bus voltage of slave machine side and the bus negative sequence voltage; the master machine sends the failure information of slave machine differential protection, and the slave machine side simultaneously reports the protection signals used for realizing the voltage-locking at both side of differential protection; Ia,Ib,Ic are the data of three phase current sampling point of slave machine side; the master machine receives the sampling data of three phase current sent from the slave machine, and compares the data with its own three phase current in order to calculate the differential current; the differential protection uses the split-phase type ratio differential protection, and based on the feature of line failure, uses the both side voltage locking differential protection.

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 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 invention discloses a current differential protection method, device and system for grid-connection tie lines of a large-scale inverter type power supply based on a negative sequence component. The current differential protection method comprises the steps of S1, collecting current flowing through protection 1 and protection 2 at two ends of a tie line PQ, and calculating the corresponding current phasor; S2, respectively calculating a positive sequence component, a negative sequence component and a zero sequence component of the current phasor at two ends of the tie line; S3, respectivelycalculating synthesis current of the system side and the inverter type power supply side so as to give prominence to the negative sequence current difference of the two ends of the tie line; S4, calculating a differential ratio coefficient; S5, respectively calculating differential current Idiff.phi of phase lines in three phases; S6, setting a protection action threshold Krel and a segregated phase current differential protection set value Iset, and determining that there is a fault in the tie line area when one of the following conditions is met: the differential ratio coefficient Cdiff isless than or equal to the protection action threshold Kref, or the differential current Idiff.phi is greater than the segregated phase current differential protection set value Iset; and S7, if it isjudged that there is a fault in the tie line area, sending a trip signal by the protection so as to isolate the tie line fault area from the system. The current differential protection method can reliably differentiate faults inside or outside the area from the normal operation condition, and overcomes a problem of low sensitivity of the traditional current differential protection.

The invention discloses a relay protection method and device for quickly removing dead zone faults of an air-charging transformer. The method comprises control processes of enabling circuit breakers at all sides of a transformer to be located at an opening position, enabling a current at one side to be changed from no current to current, enabling the circuit breaker at the side to be changed froman opening position to a closing position, and enabling the transformer to be in an air-charging state from the side; performing empty charging of the transformer, and opening dead zone protection forT seconds; enabling a certain non-air-charging side circuit breaker of the transformer to be located at the opening position; wherein the maximum phase current in the non-empty charging side three-phase current is greater than a current setting value, or a zero-sequence current is greater than a zero-sequence setting value, or a negative-sequence current is greater than a negative-sequence setting value; when the conditions are met, a transformer differential protection tripping action outlet loop is started after t1 is delayed, circuit breakers on all sides of the transformer are tripped off, and dead zone faults are rapidly removed. The method is advantaged in that influence of inrush current during empty charging of the transformer is avoided, the method is irrelevant to the transformer backup protection setting value, a transformer type and a fault type, and the dead zone fault removal time is greatly shortened.

The invention discloses a zero-sequence current protection method and system for a heavy-current grounding system. The method and system, by using a main criterion, control the operation of a zero-sequence current protection device, and use a state where neutral grounding zero-sequence current is greater than a setting value as the starting condition of the main criterion, or a state where the neutral grounding zero-sequence current is greater than a first setting value, and the variation of the neutral grounding zero-sequence current variation is greater than a second setting value as the starting condition of the main criterion. The neutral grounding zero-sequence current is taken as the starting component of the main criterion, and zero-sequence current protection has high reliability.

The invention specifically discloses a power terminal error data identification method based on an evidence theory. The method comprises the following steps: S1, acquiring multi-source data of a power terminal system; S2, fusing and comparing to judge whether the multi-source data in the power terminal system is consistent or not, if so, judging that the power terminal system does not have error data and opens a protection tripping outlet, and if not, judging that the power terminal system has error data and entering the step S3; S3, based on the multi-source data, generating evidence by using a protection algorithm; S4, judging whether error data exist in the power terminal system or not based on the generated evidence, if so, closing a protection tripping outlet and entering the step S5, otherwise, opening the protection tripping outlet; and S5, alarming error data in the power terminal system. According to the invention, error data in the power terminal system can be effectively distinguished under the condition that normal work is not influenced, possible incorrect protection actions are avoided, CPU resources are saved, and the protection sensitivity is high.

The present invention discloses a household appliance and a surge protection circuit and method for the household appliance. The surge protection circuit includes: a zero-crossing detection unit for obtaining a zero-crossing interval of AC mains by performing a zero-crossing detection on a pulsating direct current; a bidirectional surge detecting unit, including first to third detecting branches,for detecting a forward surge trigger voltage, a current surge voltage, and a negative surge trigger voltage of the AC mains respectively; and a control unit for triggering a surge protection when thecurrent surge voltage is judged to be greater than a preset reference voltage by the zero-crossing interval of the AC mains, and judging whether to trigger the surge protection according to a relationship between a current surge voltage and the forward surge trigger voltage and the negative surge trigger voltage when the AC mains are not in the zero-crossing interval. According to the household appliance and the surge protection circuit and the method for the household appliance, the circuit adopts an unidirectional surge protection in the zero-crossing intervals and a bidirectional surge protection in a non-zero-crossing interval, so that a bidirectional protection can be realized, a protection sensitivity is improved, and a surge false protection during zero-crossing can be avoided.