110results about How to "Avoid false protection" patented technology

A judgment method of line breakage of a special TV for inter-turn protection of a generator comprises the following steps: a generator terminal is provided with a general voltage transformer TV1 and aspecial voltage transformer TV2 for inter-turn protection; a protection device is used for sampling secondary side voltages of the voltage transformers, thus respectively obtaining negative sequencevoltage 3U2 of the TV1, negative sequence voltage 3U2' and foundational wave zero sequence voltage 3U0' of the TV2 based on holocycle Fourier filtering and calculation; and fixed values U2.set1, U2.set2 and U0.set2 are preset inside the protection device, wherein, 3U2 is smaller than U2.set1(1), 3U2' is greater than U2.set2 (2) and 3U0' is greater than U0.set2 (3). When meeting inequations (1)-(3)simultaneously, a line breakage alarm signal of the TV2 is generated after short delay t1, and the inter-turn protection is locked; and if the TV2 has no line breakage later, that is, that is, the inequations (1)-(3) can not be met simultaneously, line breakage alarm of the TV2 is canceled after long delay t2, and longitudinal fundamental wave zero voltage inter-turn protection is re-started.

The invention discloses an element and a method for discriminating a fault electrode of an ultra-high-speed DC transmission line based on a single-end transient signal. The fault electrode discriminating element comprises a fault component computing element, a backward traveling wave energy computing unit and a comparing and order-issuing unit. The method comprises the following steps of: discriminating a fault electrode and a normal electrode of a DC transmission line by using a backward traveling wave energy value and a threshold value subjected to comparative calculation; if the backward traveling energy value is more than the threshold value, judging that the operation electrode of the DC transmission line is the fault electrode; or else, judging the operation electrode of the DC transmission line is the normal electrode and sending out corresponding commands. The test result shows that the fault electrode discriminating element of the DC transmission line can be used for accurately discriminating the fault electrodes and the normal electrodes in different DC transmission projects and in different operation conditions of the DC transmission project only by using single-end voltage and current signals of a line and is not subjected to the influences of fault positions and transition resistors; the protecting and setting workload for different DC transmission projects is low and the workloads of protection workers and on-site operating staff are reduced.

The invention discloses a method for judging the breakage of a voltage transformer circuit; the secondary side three-phase voltage and the open triangular zero sequence voltage of a generator terminal voltage transformer TV are measured, and the tertiary harmonic voltage UA3, UB3 and UC3, and the tertiary harmonic component 3U03 of the open triangular zero sequence voltage are calculated; the value of the secondary phase voltage side is return counted to be U'03 according to the voltage transformation ratio of the voltage transformer TV on the 3U03: Umax=max{UA3, UB3, UC3, U'03}, Umin=min{UA3, UB3, UC3, U'03}; and when the Umax >=K.Uset0 and Umax>=K.Umin are met simultaneously, the breakage of the TV circuit is judged, wherein K is the fixed slope value, Uset0 is the inflection point fixed voltage value, and the two are constants. The method can accurately judge if the TV circuit is broken, and because the voltage measured of the TV is only used, the voltage of other TVs or the current of a TA do not need to be measured, and the criterion is simple and is easy to realize.

The invention discloses a method for processing boundary information deficiency of a centralization protector of a digitalized converting station, which comprises the following steps that: the centralization protector collects current and voltage values of the whole converting station and the states of circuit breakers, and acquires voltage and current sampling value information of the whole converting station in real time; when faults happen, if the current sampling value information of one line is deficient, a current sampling value of the information deficient line is synthesized on the premise that a bus is supposed to have no faults, and then a bus voltage and a line current sampling value are used, wherein the information deficient line adopts a resultant current, and the faults are removed through conventional line protection; and if the faults are detected on a first section of the conventional protection of the information deficient line, the circuit breaker of the line is tripped off without delay, and then the conventional bus differential protection is used for detecting whether the bus has the faults or not so as to determine whether to trip off all the circuit breakers connected with the bus. The method can quickly position the faults and remove the faults of boundary regions, greatly simplifies the cooperating setting of protection, and improves the reliability of the protection.

The invention discloses a short-circuit protection circuit for an APF high-power IGBT. The short-circuit protection circuit comprises the working control circuit of the IGBT and the short-circuit protection circuit of the IGBT, the working control circuit of the IGBT is used for controlling the IGBT to work or not, and the short-circuit protection circuit of the IGBT is used for monitoring the short circuit currents of the IGBT and preventing the short circuit of the IGBT from causing overvoltages to damage the IGBT through a slowly lowered grid voltage circuit. The short-circuit protection circuit of the IGBT comprises the working control circuit of the short-circuit control circuit, the detecting circuit of the short-circuit protection circuit, the slowly lowered grid voltage circuit and a latch protecting resetting circuit, wherein the working control circuit is used for controlling the short-circuit protection circuit to work or not, the detecting circuit is used for detecting the voltage of the IGBT, the slowly lowered grid voltage circuit is used for slowly lowering grid voltages, and the latch protecting resetting circuit is used for protecting and locking a PWM, and completely turning off the IGBT. The short-circuit protection circuit for the APF high-power IGBT has the advantages of improving the reliability of the working circuit, and reducing the overvoltages in a turning off process by adopting the soft turn-off mode of slowly lowering IGBT grid voltages when a short circuit occurs.

The invention discloses a parallel MOS transistor current sharing and short circuit protection circuit, and relates to the technical fields of electronic circuits and power electronics. The parallel MOS transistor current sharing and short circuit protection circuit comprises a switching value monitoring circuit, an analog quantity monitoring circuit, a fast monitoring circuit, an MOS transistor parallel current sharing circuit, a driving circuit and a main control circuit, wherein one end of the switching value monitoring circuit is connected with the main control circuit; the other end of the switching value monitoring circuit is connected with the main control circuit and one end of the analog quantity monitoring circuit; the other end of the analog quantity monitoring circuit is connected with the fast monitoring circuit; the fast monitoring circuit is connected with the main control circuit and one end of the MOS transistor parallel current sharing circuit; and the MOS transistor parallel current sharing circuit is connected with the driving circuit and external bus voltage. The parallel MOS transistor current sharing and short circuit protection circuit realizes that each MOS transistor is equal in flowing current and switching speed, and can detect the current operating state of each MOS transistor quickly and effectively; and the parallel MOS transistor current sharing and short circuit protection circuit is simple and reliable in circuit construction and small in PCB occupation area.

The invention discloses a current increment protection method capable of reflecting a mean current change rate. The method comprises the following steps of: sampling feeder line current by an isolation amplification unit to obtain an instantaneous current value by using a metro DC feeder line protection device; filtering a high frequency component by using a digital filtering algorithm, and calculating an actual current value; when current increment in a sampled data window exceeds a set starting value, starting protection, and stating performing timing by using an exit timer; calculating a current change rate in a time period from 20ms before the protection is started to 20ms after the protection is started, and if the current change rate exceeds a set value, and is kept for longer than 20ms, arranging an increment protection enable flag; and when the time of the exit timer exceeds a set increment protection time value, and the current increment is not lower than a set increment protection returning value, and is provided with the increment protection enable flag, protecting an exit to be tripped. By the method, the mean current change rate in the time period is reflected, and is stable, reliable and not fluctuated along with the fluctuation of current change rates.

The invention discloses an acceleration method for zero sequence inverse time limit overcurrent protection of adjacent lines in one-tower two-circuit lines. The method includes calculating a critical failure position of false action of adjacent line protection according to an obtained zero sequence impedance value; calculating zero sequence inverse time limit protection zero sequence current flowing through the two ends of a failure line when a failure occurs at the critical failure position and calculating the action time of failure line two end protection; calculating the action time of protection of adjacent lines on two sides of the two-circuit lines by adding a time delay to the action time of failure line two end protection; solving a time setting coefficient of protection of adjacent lines on two sides of the two-circuit lines after a setting process. The invention also discloses a zero sequence current change based acceleration scheme for zero sequence inverse time limit overcurrent protection of the adjacent lines. The invention has beneficial effects that prior performance of inverse time limit protection is not affected; and normal action of zero sequence inverse time limit protection is enabled when a prior acceleration scheme cannot work due to different reasons, so that failure elimination reliability is ensured.

The invention discloses a method for collecting high reliability analog quantity of relay protection device. An independent ADC chip is used to monitor an analog power supply of the data ADC chip, andthe CPU periodically reads the voltage value of the analog power supply. When the voltage value exceeds the normal operating range allowed by the data ADC chip, the abnormal alarm of the analog powersupply is generated. When the analog power supply is abnormal, the protection logic locks the trip output, and the merging unit locks the SV message output. When the analog supply voltage returns tonormal operation, the protection logic and merge unit exit the latched state. The analog power supply voltage is confirmed after multiple sampling to prevent the misjudgment caused by instantaneous interference. The invention effectively prevents the wrong data output caused by the abnormal analog power supply of the ADC chip, improves the reliability of the analog quantity collection, and prevents the malfunction of the relay protection device by blocking the local protection trip output and the SV message output.

The invention discloses an analysis experimental device and an analysis experimental method for protection malfunction caused by direct current (DC) grounding. The analysis experimental device stimulates the circuit sate of a DC system in actual operation, provides experimental parameters such as insulation resistance, bridge resistance, grounding capacitance, cable capacitance and the like, and can be used for experimenting on faults of positive grounding, negative grounding and control loop grounding; concrete experimental contents and a concrete experimental method are provided; and a principle of protection malfunction caused by one-point grounding and related parameters thereof are fully realized for research and development, production, inspection, operation and maintenance and other links so as to take protection measures to prevent the generation of protection malfunction accidents caused by one-point grounding, thereby effectively improving the safe operation level of an electric system. The experimental method can be widely applied in relay protection research and production manufacturers, DC grounding detection equipment research and production manufacturers and operation accident analysis on the electric system.

The invention relates to a voltage surge detection circuit, which comprises a rectification circuit, a surge detection circuit and a zero-cross detection circuit, wherein an input end of the surge detection circuit and an input end of the zero-cross detection circuit are respectively connected with the rectification circuit, an output end of the surge detection circuit is connected with an output end of the zero-cross detection circuit, and alternating current mains supply is converted into direct current mains supply by the rectification circuit. A mains supply alternating current voltage signal is detected by the surge detection circuit disclosed by the invention, and if the mains supply alternating current voltage signal has the surge phenomenon, the circuit takes effect, and the output surge signal is a high-level signal. The signal triggers subsequent surge protection circuits to work, and related power components are protected against damage. If the mains supply alternating current signal does not have the surge phenomenon, the output surge signal is a low-level signal. The surge phenomenon in a circuit can be accurately detected by the voltage surge detection circuit, so that a semiconductor power component in a circuit system can be effectively protected.

A device for detecting multipoint earthing of a voltage transformer for an electric system comprises a CPU main controller, an analog-digital conversion circuit and a switch control circuit. A voltage transformer secondary neutral line N600 penetrating into an opening current transformeris connected with a ground point, and output passes through a first filter amplifying circuit to the analog-to-digital conversion circuit. A ground point penetrates through a current transformer to be connected with one end of a sampling resistor Rv, output passes through a second filter amplifying circuit to reach the analog-to-digital conversion circuit, the other end of the sampling resistor Rv is connected with a plurality of branch circuits, and switches and resistors are in series connection with the branch circuits which are correspondingly and externally connected with an A-phase bonding post of the voltage transformer for electricity use. The two ends of the sampling resistor Rv further outputs a 0-5V voltage signal to the analog-to-digital conversion circuit through an isolation amplifying circuit. The invention further relates to a method for detecting multipoint earthing faults of the voltage transformer for the electric system. According to the device for detecting multipoint earthing of the voltage transformer for the electric system and the method for detecting multipoint earthing faults of the voltage transformer for the electric system, whether the multipoint earthing faults of many voltage transformers exist can be accurately detected in time, and the multipoint earthing faults can be specifically located.

The invention relates to a distance protection system suitable for a half-wavelength power transmission line and a control method thereof. The distance protection system comprises a comprehensive distance protection unit, and at least two segmentation protection units which are arranged between the beginning end and the tail end of a power transmission line and at a certain distance from the two ends. A certain distance is reserved between any two adjacent segmentation protection units. Each segmentation protection unit is used for receiving electric quantity information of a corresponding segmentation point on the power transmission line and calculating impedance information of the corresponding segmentation point. The outputs of all the segmentation protection units are connected with the comprehensive distance protection unit. According to related information sent by the segmentation protection units, analysis and determination are carried out, and corresponding signals are output, so as to protect the power transmission line. The use of the system for relay protection can solve problems of protection action resistance due to the extremely large measurement impedance in the middle of the line, and protection malfunction due to the measurement impedance being close to a fault of a beginning end in case of an outer fault at a far end of the line.

The invention relates to a large difference protection method based on second harmonic excitation surge current of a converter transformer. When a single-phase earth fault is generated in a valve side area of the converter transformer, second harmonic content in differential current in large difference protection, differential current in differential protection of a Yn/Y converter transformer and differential current in differential protection of a Yn/D converter transformer is adopted for comprehensive recognition to recognize excitation surge current, so that the resulting protection maloperation is effectively avoided. The method is simple and reliable to realize and lower in realization threshold, can be realized on the original protection device platform, and has a very high popularization value.

The invention discloses a short-circuit accident protective method of converting valve group, which comprises the following judging expression formulas: |IVY|-IDP>Ivss+k*|IVY|, |IVD|-IDP>Ivss+k*|IVD|(2); |IVY|-IDNC>Ivss+k*|IVY|, |IVD|-IDNC>Ivss+k*|IVD|(3), wherein IVY and IVD is equivalent DC current; Ivss and k are constant; IDP is DC current for electrode bus valve side; IDNC is DC current for neutral bus valve side; if the conversing valve group occurs short circuit, (2) or (3) satisfies. The invention guarantees the reliability and safety for valve group, which avoids error movement in the measuring course.

The invention discloses a high-voltage direct current transmission line self-adaptive travelling wave protection method. The method includes the following steps that a relay protection device is powered on; a value is assigned to a travelling wave protection starting constant value delta initial; the voltage u and the current i of a pole line and the current iop of an antipole line are measured; the pole voltage change ratio du/dt, the pole voltage change amount Du, the pole current change amount Di and the antipole current change amount Diop are calculated; whether a starting criterion du/dt > delta initial is met or not is judged; the voltage ratio and relevant parameters are calculated; a voltage change ratio protection constant value delta r-set and a voltage change amount protection constant value delta v-set are calculated according to the voltage ratio; whether du/dtmax > delta r-set and Dumax > delta v-set are met or not is judged; whether on the rectification side, Dimax > Diop_max and Dimax > 0.1 or on the inversion side, Dimin < Diop_min and Dimin < -0.1 is met or not is judged; if yes, starting is protection. The method is high in sensitivity and antijamming capability, engineering realization is easy to achieve, faulty lines of direct current transmission lines can be rapidly determined, and the misjudgment phenomenon is not prone to occur.

The invention relates to an alternating-current component transmission modeling and parsing method along line in operation of a high-voltage direct current in different ways. The method comprises: firstly, an impedance admittance parameter of a line with a unit length is calculated according to a direct-current line pole parameter in a direct-current project; secondly, a uniformly distributed parameter circuit of a single-loop long-distance line is processed to be equivalent to a single loop type equivalent circuit and a correlated parameter is solved; thirdly, an equivalent circuit of a positive-negative dual-loop direct-current power transmission line with the unit length in the direct-current project is decoupled by using a phase-mode transformation matrix; fourthly, a central parameter impedance value and a ground admittance value in the positive-negative dual-loop with the unit length are converted into a distributed parameter impedance value and a ground admittance value; and fifthly, with combination of the direct-current line length in the high-voltage direct-current power transmission project as well as boundary conditions in different operation ways, an operation equivalent circuit diagram of a high-voltage direct-current power transmission system is transformed to obtain alternating-current component along-line transmission and parsing models of the high-voltage direct-current power transmission system in different operation ways.

The invention relates to a DC voltage detection and control method for a metro regenerative energy feedback device, the method includes detecting and protecting DC side voltage and dynamically adjusting a DC starting voltage threshold value and determining a DC voltage reference value. Aiming at the disturbance problem in DC traction network, a voltage detection and protection method is proposed.The disturbance time superposed on the direct current network system in the subway power supply system is generally of the microsecond level. When the disturbance occurs, the interference superposed on the direct current network can be effectively filtered out after the invention is adopted, so as to prevent the equipment from being mistakenly protected. When a real overvoltage or undervoltage fault occurs in the DC network, the protection time is less than 1ms, which can meet the response time requirements of the system. Aiming at the problem of slow response or circulating current caused byAC voltage fluctuation, a control method of DC voltage start-up threshold and adaptive control is proposed. The method is simple to implement, thus effectively avoiding the problem of circulation or slow response caused by the fluctuation of AC voltage.

A transformer non-electrical quantity protection device comprises a transformer non-electrical quantity protection body device, wherein the transformer non-electrical quantity protection body device is provided with a first trip contact, a second trip contact and a third trip contact; the first trip contact, the second trip contact and the third trip contact are connected to a first non-electrical quantity protection device, a second non-electrical quantity protection device and a third non-electrical quantity protection device, respectively; the first non-electrical quantity protection device is connected to a first two-out-of-three redundance module and a second two-out-of-three redundance module; the second non-electrical quantity protection device is connected to the first two-out-of-three redundance module and the second two-out-of-three redundance module; the third non-electrical quantity protection device is connected to the first two-out-of-three redundance module and the second two-out-of-three redundance module; and the first two-out-of-three redundance module and the second two-out-of-three redundance module are connected to a first trip circuit and a second trip circuit, respectively. The transformer non-electrical quantity protection device is capable of preventing either protection false tripping caused by a single-contact fault or failure to operate for operation in case of a fault of a single module.

The invention discloses a method and a device for controlling MFT (Main Fuel Trip). The device comprises an OR gate, wherein a combustion flame loss signal and a power supply loss signal are used as input signals of the OR gate, and an output end of the OR gate is connected with all-flame loss MFT of a boiler. According to the method and the device, disclosed by the invention, main protection control logic of the all-flame loss MFT can be more reliable, a mis-operation action caused by an abnormal situation of a power supply can be avoided, and thus the normal production operation of a power station can be ensured.

The invention discloses an air conditioner fluorine lack protection method and an air conditioner. The air conditioner fluorine lack protection method comprises the following steps that when the air conditioner operates and refrigerates, the temperature change of an inner disc is monitored in real time, and whether the air conditioner is judged in a normal refrigeration state or not; when the airconditioner is judged to be in the normal refrigeration state, the difference value between the return air temperature and the inner plate temperature is detected, and the difference value is comparedwith a preset first range and a preset second range; when the air conditioner is judged in an abnormal refrigeration state, the fluorine-lack signal is reported, and the fluorine-lack protection operation is started; when the difference value between the return air temperature and the inner plate temperature is in the preset first range, so that the air conditioner is overloaded; and when the difference value between the return air temperature and the inner plate temperature is in the preset second range, the fluorine-deficient signal is reported, and the fluorine-lack protection operation isstarted. According to the method, the misoperation can be effectively prevented, the protection is more accurate, the method is simple, a new hardware facility does not need to be added, only the program needs to be changed on the basis of the existing hardware, the cost is more optimized, and the applicability is stronger.