A method and device for identifying inter-turn faults of high-voltage shunt reactors

Abstract

The present invention relates to a method and device for identifying inter-turn faults of high-voltage shunt reactors. When the inter-turn fault protection start-up conditions and the zone fault judgment conditions are met, the phase measurement impedance of the reactor meets the low impedance judgment criteria, and the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient or the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated, it is determined to be an inter-turn fault of the reactor. If it is determined to be an inter-turn fault of the reactor, the inter-turn fault protection is activated. Since the harmonic content in the zero-sequence current is high when the core is saturated, and the harmonic content in the zero-sequence current is low when the zone fault occurs, the core saturation fault and the reactor inter-turn fault can be identified by the comprehensive harmonic content and waveform characteristics of the self-generated zero-sequence current at the first end, to prevent the inter-turn protection from malfunctioning due to the core saturation of the reactor when the circuit breaker is opened and closed, so as to improve the reliability of the protection device.

Description

Technical Field

[0001] The present invention relates to the technical field of power system fault protection, and in particular to a method and device for identifying inter-turn faults of high-voltage shunt reactors. Background Art

[0002] Offshore wind power is usually transmitted to the load center through a 220kV booster station. Since submarine cables are used for transmission and the transmission distance is long, in order to limit the distributed capacitance current of the transmission line, it is necessary to install shunt reactors on the transmission line. 500kV and above shunt reactors usually adopt a split-phase structure, but 220kV shunt reactors mostly adopt a three-phase structure. The main fault forms of the reactor are turn-to-turn short circuit, single-phase grounding, and phase-to-phase grounding. Turn-to-turn short circuit of the reactor is a relatively common internal fault form. When the number of short-circuited turns is small, the three-phase current imbalance caused by the short-circuit of one phase turn may be very small and difficult to be detected by the relay protection device; and no matter how large the short-circuit turns are, the longitudinal differential protection can never reflect the turn-to-turn short circuit fault. For this reason, other highly sensitive, reliable and safe turn-to-turn short circuit protection must be considered for high-voltage shunt reactors.

[0003] As a mature means of regulating reactive power, improving system compensation and suppressing system overvoltage, high-voltage shunt reactors are widely installed in the busbars and lines of ultra-high and extra-high voltage transmission systems. High-voltage shunt reactors are large-capacity shunt inductors with iron cores, which are similar to the primary side of transformers in structure. In recent years, there have been many cases of false operation of the inter-turn protection of reactors when the circuit breaker is opened and closed on offshore wind power transmission lines. The reason is that the iron core of the reactor is saturated when the circuit breaker is closed, and the characteristics are the same as those of the inter-turn fault of the reactor. In addition, since there is no dedicated line PT for 220kV lines, the inter-turn protection voltage can only be obtained from the bus PT. When the circuit breaker is opened, the cable line oscillates at a low frequency, the reactor is saturated and the current increases. The original inter-turn protection scheme can no longer adapt to the application scenarios of offshore wind power transmission lines. It is urgent to improve the inter-turn protection scheme of the reactor to ensure the safe and stable operation of the power grid.

[0004] In the prior art, turn-to-turn protection is usually composed of a zero-sequence power direction element, a zero-sequence impedance element and a starting element, which can not only improve the sensitivity of the reactor turn-to-turn protection action, but also ensure that it will not malfunction under external short circuits (such as series compensation lines, LC resonance, oscillation and other factors) and any abnormal operating conditions (such as non-full phase, short circuit or disconnection of the CT secondary circuit, etc.).

[0005] When there is an internal inter-turn short circuit fault in the reactor, the phase of the zero-sequence current leads the zero-sequence voltage by nearly 90 degrees; when there is an internal single-phase ground short circuit fault in the reactor, the phase of the zero-sequence current leads the zero-sequence voltage; when there is an external single-phase ground short circuit fault in the reactor, the phase of the zero-sequence current lags behind the zero-sequence voltage. Therefore, the phase relationship between the zero-sequence current and the zero-sequence voltage on the line side of the reactor can be used to distinguish the inter-turn short circuit, internal ground short circuit and external ground short circuit of the reactor when there is an internal inter-turn short circuit fault, internal single-phase ground fault and external single-phase ground fault in the reactor.

[0006] The action equation of the adaptive compensation type zero-sequence power directional element is as follows:

[0007]

[0008] In the above formula, I0 and U0 are the self-generated zero-sequence current and voltage of CT and PT on the line side of the reactor, respectively. b is the zero-sequence reactance of the reactor (including the zero-sequence reactance of the reactor including the small reactor). k is a floating parameter, which can usually be 0 to 0.8 and varies with the magnitude of the zero-sequence voltage and zero-sequence current.

[0009] Zero-sequence impedance element Since the primary zero-sequence impedance of the reactor is generally around several thousand ohms, while the primary zero-sequence impedance of the system is generally around tens of ohms, the protection device can use the zero-sequence impedance of the reactor port to determine whether a turn-to-turn fault has occurred. When a turn-to-turn short circuit and an internal single-phase grounding fault occur in the reactor, the zero-sequence impedance measured at the reactor port is the zero-sequence impedance of the system. When an external single-phase grounding fault occurs in the reactor, the zero-sequence impedance measured at the reactor port is the zero-sequence impedance of the reactor. The large difference in the measured values ​​of the two can be used to distinguish between the turn-to-turn short circuit, internal ground short circuit and external ground short circuit of the reactor.

[0010] The criterion for starting the turn-to-turn short-circuit protection is:

[0011] I0>k△I t +I th

[0012] Where: △I t is a floating threshold, which increases automatically and gradually as the phase current change output increases, and k is a constant. △I is the half-cycle integral value of the phase current, I th The fixed threshold is 0.1I e , I e is the secondary rated load current of the reactor.

[0013] When the device determines that the PT is abnormal or the PT is under maintenance, the zero-sequence power direction element and the zero-sequence impedance element do not meet the conditions, that is, the inter-turn short-circuit protection exits operation; when the device determines that the reactor CT is abnormal, the zero-sequence power direction element and the zero-sequence impedance element do not meet the conditions, that is, the inter-turn short-circuit protection exits operation.

[0014] Since the zero-sequence impedance of the system is very small compared to the zero-sequence impedance of the reactor, when a turn-to-turn short circuit occurs, its zero-sequence source is inside the reactor, and the voltage drop (zero-sequence voltage) of the zero-sequence current on the system zero-sequence impedance is very small. In order to improve the sensitivity of the turn-to-turn short circuit protection, it is necessary to compensate for the zero-sequence voltage. The electrical characteristics of the saturation of the high-voltage shunt reactor are similar to those of the turn-to-turn short circuit fault, which is manifested as a rapid increase in the winding current, large harmonic content, and reduced calculated inductance of the winding. Because its attenuation time is often long, the existing turn-to-turn protection is not reliable enough when the high-resistance is saturated, and it is easy to malfunction and cause the line or the entire bus to be cut off, and the consequences cannot be ignored. The existing high-resistance turn-to-turn protection does not identify the saturation of the reactor core, which is easy to cause the turn-to-turn fault protection to malfunction. Summary of the invention

[0015] Based on the above situation of the prior art, the purpose of the present invention is to propose a method and device for identifying inter-turn faults of high-voltage shunt reactors, so as to solve the problem of saturation of the reactor core when the circuit breaker of the offshore wind power transmission line is opened and closed, and the saturation characteristics are the same as the inter-turn fault of the reactor, causing false protection.

[0016] To achieve the above object, according to one aspect of the present invention, a method for identifying turn-to-turn faults in a high-voltage shunt reactor is provided, comprising the steps of:

[0017] Monitor the start-up conditions of turn-to-turn fault protection, the conditions for determining faults within the zone, the phase measurement impedance of the reactor, and the self-generated zero-sequence current signal at the first end of the reactor;

[0018] If the inter-turn fault protection starting conditions and the intra-zone fault judgment conditions are met, the phase measurement impedance of the reactor meets the low impedance judgment criterion, and the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient or the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated, it is determined to be an inter-turn fault of the reactor, and the inter-turn fault protection is activated.

[0019] Furthermore, the inter-turn fault protection start-up conditions include:

[0020] When the self-generated zero-sequence current at the first end of the reactor is greater than the zero-sequence starting current setting and there is zero-sequence current at the tail end, the inter-turn fault protection is activated.

[0021] Furthermore, the in-zone fault determination condition is satisfied, including using the following determination equation for determination:

[0022]

[0023] in, is the phasor of the zero-sequence voltage produced by the voltage transformer, is the phase quantity of the zero-sequence current produced by the current transformer at the first end of the reactor, X L0 is the secondary zero-sequence reactance value of the reactor; X S0 is the system zero-sequence reactance value, X S0 =(0.01~0.2)X L0 ; When the above equation is satisfied, it is judged as an in-zone fault.

[0024] Furthermore, the phase measured impedance of the reactor satisfies the low impedance criterion, including using the following judgment equation for judgment:

[0025] When Z φ <m2Z e When , it is judged as low impedance;

[0026] in, is the phase measurement impedance of the reactor, Z e is the secondary phase reactance of the reactor; m2 is a constant, which is related to the minimum value of the three-phase current at the head end.

[0027] Furthermore, the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient, including using the following judgment equation for judgment:

[0028]

[0029] Among them, I φ_syn k is the comprehensive harmonic current in the zero-sequence current generated by the reactor at the first end, xb is the comprehensive harmonic braking coefficient, I1 is the fundamental current in the zero-sequence current generated by the reactor at the first end, i n is the sampling value of each point in one cycle, and N is the number of sampling points in one cycle.

[0030] Furthermore, the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated, which is determined by the following steps:

[0031] Differentiate the zero-sequence current waveform generated by the reactor at the first end;

[0032] The zero-sequence current waveform generated at the first end of the reactor before and after differentiation is saturated.

[0033] Furthermore, the saturation determination of the zero-sequence current waveform generated by the reactor head end before and after differentiation includes:

[0034] The number of sampling points that meet the high-setting judgment condition is N1, and the number of sampling points that meet the low-setting judgment condition is N2 in one cycle of the self-generated zero-sequence current at the first end of the pre-differential reactor is counted respectively;

[0035] When N1≥the first preset number of points, and N2≥the second preset number of points, it is determined that the zero-sequence current waveform generated by the reactor head end is unsaturated;

[0036] The high set value determination condition and the low set value determination condition include the following formulas:

[0037]

[0038] Among them, i K is the current sampling value of the neutral point zero-sequence current, i K.MAX It is the maximum peak value of the sampling value within the previous cycle of the differential of the self-generated zero-sequence current at the first end of the reactor; k1 is a high-value constant, k2 is a low-value constant, k1>k2.

[0039] Furthermore, the saturation determination of the zero-sequence current waveform generated by the reactor head end before and after differentiation includes:

[0040] The number of sampling points satisfying the high-setting judgment condition is N1, and the number of sampling points satisfying the low-setting judgment condition is N2 in one cycle of the zero-sequence current generated at the first end of the reactor after differentiation;

[0041] When N1≥the first preset number of points, and N2≥the second preset number of points, it is determined that the zero-sequence current waveform generated by the reactor head end is unsaturated;

[0042] The high set value determination condition and the low set value determination condition include the following formulas:

[0043]

[0044] Among them, △i K is the current sampling value after differentiation, i K.MAX It is the maximum peak value of the sampling value within the previous cycle of the differential of the self-generated zero-sequence current at the first end of the reactor; k1 is a high-value constant, k2 is a low-value constant, k1>k2.

[0045] Furthermore, after determining that there is an inter-turn fault in the reactor, a predetermined delay time is delayed and the inter-turn fault protection is activated.

[0046] According to another aspect of the present invention, a high-voltage shunt reactor turn-to-turn fault identification device is provided, comprising a turn-to-turn fault protection start-up module, an intra-zone fault judgment module, a low impedance judgment module, a comprehensive harmonic content judgment module of the self-generated zero-sequence current at the first end of the reactor, a waveform judgment module of the self-generated zero-sequence current at the first end of the reactor, and a turn-to-turn fault protection action module; wherein,

[0047] The turn-to-turn fault protection startup module determines whether the turn-to-turn fault protection is started;

[0048] The in-area fault judgment module judges whether it is an in-area fault;

[0049] The low impedance judgment module judges whether the phase measurement impedance of the reactor meets the low impedance judgment criterion;

[0050] The module for judging the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is used to judge whether the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient;

[0051] The waveform judgment module of the self-generated zero-sequence current at the first end of the reactor is used to judge whether the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated;

[0052] The inter-turn fault protection action module controls the inter-turn fault protection action when determining that there is an inter-turn fault of the reactor.

[0053] In summary, the present invention provides a method and device for identifying inter-turn faults of high-voltage shunt reactors. When the inter-turn fault protection start-up conditions and the intra-zone fault judgment conditions are met, the phase measurement impedance of the reactor meets the low impedance criterion, and the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient or the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated, it is determined to be an inter-turn fault of the reactor. If it is determined to be an inter-turn fault of the reactor, the inter-turn fault protection is activated. Since the harmonic content in the zero-sequence current is high when the core is saturated, and the harmonic content in the zero-sequence current is low when the fault is intra-zone, the core saturation fault and the reactor inter-turn fault can be identified by the comprehensive harmonic content and waveform characteristics of the self-generated zero-sequence current at the first end, to prevent the inter-turn protection from malfunctioning due to the core saturation of the reactor when the circuit breaker is opened and closed, so as to improve the reliability of the protection device. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is the main wiring diagram of the high-voltage shunt reactor turn-to-turn fault protection circuit;

[0055] Figure 2 It is a structural block diagram of the high-voltage shunt reactor turn-to-turn fault identification device of the present invention and a schematic diagram of the protection logic relationship. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0057] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings. According to one embodiment of the present invention, a method for identifying turn-to-turn faults of a high-voltage shunt reactor is provided. Figure 1 The main wiring diagram of a high-voltage shunt reactor turn-to-turn fault protection circuit is shown in FIG. Figure 1 As shown, the reactor is located on the line side, and the line has no dedicated voltage transformer. The reactor turn-to-turn fault identification is connected to the head-end current transformer CT1 and the tail-end current transformer CT2. The head-end current transformer CT1 is used to detect the current at the head end of the reactor, and the tail-end current transformer CT2 is used to detect the current at the tail end of the reactor. The voltage is the bus voltage. When the line 1G knife switch is closed, the reactor turn-to-turn fault identification is connected to I bus, and when the line 2G knife switch is closed, the reactor turn-to-turn fault identification is connected to II bus. The two sections of bus voltage are connected to the reactor turn-to-turn fault identification after the voltage transformers PT1-1 and PT1-2 are switched after the line 1G and 2G knife switches are switched. That is, when the line 1G knife switch is closed, the I bus voltage transformer PT1-1 is used, and when the line 2G knife switch is closed, the II bus voltage transformer PT1-2 is used to ensure that the bus voltage used by the reactor is consistent with the bus connected to the line. Before the reactor is put into operation, the 3G switch is closed, and the corresponding line is shut down or put into operation by opening and closing the circuit breaker DL. QH is a voltage switching device, which selects the corresponding bus voltage according to the line 1G and 2G switches. When the line 1G switch is closed, the I bus voltage transformer PT1-1 is used, and when the line 2G switch is closed, the II bus voltage transformer PT1-2 is used.

[0058] The high-voltage shunt reactor turn-to-turn fault identification method comprises the following steps:

[0059] Monitor the start-up conditions of inter-turn fault protection, the conditions for determining faults within the zone, the phase measurement impedance of the reactor, and the self-generated zero-sequence current signal at the first end of the reactor.

[0060] If the inter-turn fault protection start-up conditions and the zone fault judgment conditions are met, the phase measurement impedance of the reactor meets the low impedance judgment criteria, and the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient or the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated, it is determined to be an inter-turn fault of the reactor, and the inter-turn fault protection is activated. The specific judgment method of each of the above judgment conditions is described in detail below.

[0061] Turn-to-turn fault protection starts. In this embodiment, the turn-to-turn protection of the high-voltage shunt reactor is started by the self-generated zero-sequence current at the head end. The conditions for starting the turn-to-turn fault protection include: when the self-generated zero-sequence current at the head end of the reactor is greater than the zero-sequence starting current setting, and there is a zero-sequence current at the tail end, the turn-to-turn fault protection starts, which can be expressed by the following discriminant equation:

[0062]

[0063] In the above formula, 3I01 is the amplitude of the self-generated zero-sequence current at the first end of the reactor, 3I 0.set It is the zero sequence starting current setting; 3I 02 is the amplitude of the self-generated zero-sequence current at the tail end of the reactor, I e is the secondary rated current of the reactor.

[0064] After the protection is started, when a fault occurs, the zero-sequence voltage absolute value comparison criterion is first used to distinguish between internal and external faults to determine whether it is an internal fault. The following judgment equation can be used for judgment:

[0065]

[0066] in, is the phasor of the zero-sequence voltage produced by the voltage transformer, is the phase quantity of the zero-sequence current produced by the current transformer at the first end of the reactor, X L0 is the secondary zero-sequence reactance value of the reactor; X S0 is the system zero-sequence reactance value, X S0 Unable to measure, set it to (0.01~0.2)X L0 ; When the above equation is satisfied, it is judged as an in-zone fault.

[0067] To determine whether the phase measurement impedance of the reactor meets the low impedance criterion, the phase measurement impedance of the three-phase reactor can be calculated using the following formula:

[0068]

[0069] In the above formula, Represent phases A, B and C respectively, is the phase measurement impedance of the reactor, is the phasor of the reactor phase voltage, is the phase quantity of the phase current at the first end of the reactor, I e is the secondary rated current of the reactor, and m1 is a constant, which can be 0.1 to 0.3, for example. Then, the following judgment equation is used to judge whether the phase measurement impedance of the reactor meets the low impedance criterion:

[0070] When Z φ <m2Z e When , it is judged as low impedance;

[0071] Among them, Z e is the secondary phase reactance of the reactor; m2 is a constant, which is related to the minimum value of the three-phase current at the head end. When the minimum value of the three-phase current at the head end is less than 0.5I e When the minimum value of the three-phase current at the head end is greater than 0.5I e When m2 is 0.8~0.95.

[0072] The following methods can be used to determine whether the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient, and whether the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated.

[0073] Calculate the comprehensive harmonic content in the self-generated zero-sequence current at the first end of the reactor. When the comprehensive harmonic content is less than the comprehensive harmonic braking coefficient, it is judged that the comprehensive harmonic content in the zero-sequence current is low. The following judgment equation can be used:

[0074]

[0075] Among them, I φ_syn k is the comprehensive harmonic current in the zero-sequence current generated by the reactor at the first end, xb is the comprehensive harmonic braking coefficient, k xb For example, it can be set to 0.12~0.2, I1 is the fundamental current in the zero-sequence current generated by the first end of the reactor, i n is the sampling value of each point in one cycle, N is the number of sampling points in one cycle, usually N is 24 points.

[0076] To determine whether the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated, the following steps can be used:

[0077] Differentiate the zero-sequence current waveform generated at the first end of the reactor, and the differential equation is:

[0078] △i K =i K -i K-1

[0079] In the above formula, i K is the current sampling value of the neutral point zero-sequence current, i K-1 is the sampling value of the previous point, △i K is the current sampling value after differentiation.

[0080] The zero-sequence current waveform generated by the reactor at the first end before and after differentiation is saturated. The saturation judgment includes a high-set value judgment condition based on the high-set value constant k1 and a low-set value judgment condition based on the low-set value constant k2:

[0081] The number of sampling points satisfying the high-setting judgment condition is N1, and the number of sampling points satisfying the low-setting judgment condition is N2;

[0082] When N1≥the first preset number of points, and N2≥the second preset number of points, it is determined that the zero-sequence current waveform generated at the first end of the reactor is not saturated, and the first preset number of points and the second preset number of points can be set to 13 and 19 respectively; because when the normal fault waveform is symmetrical, the number of sampling points can usually meet the requirements of 13 and 19, while the current waveform is asymmetrical when the out-of-zone fault is saturated, and does not meet the requirements of 13 and 19 for the sampling points, by determining the sampling point threshold, malfunction of protection when the out-of-zone fault is saturated can be prevented.

[0083] The high set value determination condition and the low set value determination condition include the following formulas:

[0084]

[0085] Among them, i K is the current sampling value of the neutral point zero-sequence current, i K.MAX It is the maximum peak value of the sampling value within the previous cycle of the differential of the self-generated zero-sequence current at the first end of the reactor; k1 is a high-value constant, k2 is a low-value constant, k1>k2, the value range of k1 is, for example, 0.4~0.5, and the value range of k2 is, for example, 0.15~0.20.

[0086] Alternatively, the number of sampling points satisfying the high-setting judgment condition is N1, and the number of sampling points satisfying the low-setting judgment condition is N2 within one cycle, for example, 24 points, of the zero-sequence current generated at the first end of the reactor after differentiation;

[0087] When N1≥the first preset number of points, and N2≥the second preset number of points, it is determined that the zero-sequence current waveform generated by the reactor head end is not saturated, and the first preset number of points and the second preset number of points can be set to 13 and 19 respectively;

[0088] The high set value determination condition and the low set value determination condition include the following formulas:

[0089]

[0090] Among them, △i K is the current sampling value after differentiation, i K.MAX It is the maximum peak value of the sampling value within the previous cycle of the differential of the self-generated zero-sequence current at the first end of the reactor; k1 is a high-value constant, k2 is a low-value constant, k1>k2, the value range of k1 is, for example, 0.4~0.5, and the value range of k2 is, for example, 0.15~0.20.

[0091] If the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient, or the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated, it is determined to be a reactor turn-to-turn fault. After being determined to be a reactor turn-to-turn fault, after a predetermined delay time, such as 20-30ms, the turn-to-turn fault protection is activated. The reactor turn-to-turn fault and the core saturation fault are distinguished according to the waveform characteristics of the self-generated zero-sequence current at the first end. If it is determined to be a reactor turn-to-turn fault, the reactor turn-to-turn fault protection is delayed, otherwise it will be identified as a core saturation fault, and the locking operation is performed. The waveform feature identification of zero-sequence current adopts the comprehensive judgment of the comprehensive harmonic content and waveform symmetry in the zero-sequence current. When the core is saturated, the harmonic content in the zero-sequence current is high and the waveform is asymmetric. When there is an intra-zone fault, the harmonic content in the zero-sequence current is low and the waveform is symmetrical. When any one of them is met, it can be considered that an inter-turn fault has occurred. Therefore, the waveform characteristics of the zero-sequence current generated at the head end can be used to identify the inter-turn fault and core saturation fault of the reactor, thereby preventing the inter-turn protection from malfunctioning due to the saturation of the reactor core when the circuit breaker is opened and closed, thereby improving the reliability of the reactor inter-turn fault protection device.

[0092] According to another embodiment of the present invention, a high-voltage shunt reactor turn-to-turn fault identification device is provided. The block diagram of the device is as follows: Figure 2 As shown, the device includes an inter-turn fault protection starting module, an intra-zone fault judgment module, a low impedance judgment module, a comprehensive harmonic content judgment module of the self-generated zero-sequence current at the first end of the reactor, a waveform judgment module of the self-generated zero-sequence current at the first end of the reactor, a delay module, and an inter-turn fault protection action module.

[0093] An inter-turn fault protection start-up module controls the start-up of the inter-turn fault protection;

[0094] The in-area fault judgment module determines whether it is an in-area fault when a fault occurs;

[0095] A low impedance judgment module is used to judge whether the phase measurement impedance of the reactor meets the low impedance judgment criterion;

[0096] A module for judging the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is used to judge whether the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient;

[0097] A waveform judgment module of the self-generated zero-sequence current at the first end of the reactor is used to judge whether the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated;

[0098] Delay module, when it is determined to be a reactor turn-to-turn fault, delay is performed;

[0099] The turn-to-turn fault protection action module controls the turn-to-turn fault protection action after a delay when it is determined that there is a turn-to-turn fault in the reactor.

[0100] The judgment and action operations performed in the above modules correspond to the steps in the identification method provided in the first embodiment of the present invention, and will not be described one by one here. According to the relationship of the protection logic of the method, Figure 2 The figure also shows the logical relationship diagram of each module, such as Figure 2 As shown, when the inter-turn fault protection starting module starts the inter-turn fault protection, and at the same time the intra-zone fault judgment module judges that an intra-zone fault occurs, and the low impedance judgment module judges that the phase measurement impedance of the reactor meets the low impedance judgment criterion, when any one of the judgment conditions of the comprehensive harmonic content judgment module of the self-generated zero-sequence current at the first end of the reactor and the waveform judgment module of the self-generated zero-sequence current at the first end of the reactor is met, it is determined that a reactor inter-turn fault has occurred, and after the delay of the delay module, the inter-turn fault protection action module controls the inter-turn fault protection action.

[0101] In summary, the present invention relates to a method and device for identifying inter-turn faults of high-voltage shunt reactors. When the inter-turn fault protection start-up conditions and the intra-zone fault judgment conditions are met, the phase measurement impedance of the reactor meets the low impedance criterion, and the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient or the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated, it is determined to be an inter-turn fault of the reactor. If it is determined to be an inter-turn fault of the reactor, the inter-turn fault protection is activated. Since the harmonic content in the zero-sequence current is high when the core is saturated, and the harmonic content in the zero-sequence current is low when the intra-zone fault occurs, the core saturation fault and the reactor inter-turn fault can be identified by the comprehensive harmonic content and waveform characteristics of the self-generated zero-sequence current at the first end, to prevent the inter-turn protection from malfunctioning due to the core saturation of the reactor when the circuit breaker is opened and closed, so as to improve the reliability of the protection device.

[0102] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A method for identifying turn-to-turn faults in high-voltage shunt reactors, characterized in that: Includes steps: Monitor the start-up conditions of turn-to-turn fault protection, the conditions for determining faults within the zone, the phase measurement impedance of the reactor, and the self-generated zero-sequence current signal at the first end of the reactor; If the inter-turn fault protection start-up conditions and the zone fault judgment conditions are met, the phase measurement impedance of the reactor meets the low impedance judgment criteria, and the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient or the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated, it is determined to be an inter-turn fault of the reactor, and the inter-turn fault protection is activated; The comprehensive harmonic content of the zero-sequence current generated by the first end of the reactor is less than the comprehensive harmonic braking coefficient, including using the following judgment equation for judgment: Among them, I φ_syn k is the comprehensive harmonic current in the zero-sequence current generated by the reactor at the first end, xb is the comprehensive harmonic braking coefficient, I1 is the fundamental current in the zero-sequence current generated by the reactor at the first end, i n is the sampling value of each point in one cycle, N is the number of sampling points in one cycle, Indicates the phase current at the first end of the reactor.

2. The method according to claim 1, characterized in that The inter-turn fault protection starting conditions include: When the self-generated zero-sequence current at the first end of the reactor is greater than the zero-sequence starting current setting and there is zero-sequence current at the tail end, the inter-turn fault protection is activated.

3. The method according to claim 2, characterized in that The fault determination conditions within the zone are met, including using the following determination equation for determination: in, is the phasor of the zero-sequence voltage produced by the voltage transformer, is the phase quantity of the zero-sequence current produced by the current transformer at the first end of the reactor, X L0 is the secondary zero-sequence reactance value of the reactor; X S0 is the system zero-sequence reactance value, X S0 =(0.01~0.2)X L0 ; When the above equation is satisfied, it is judged as an in-zone fault.

4. The method according to claim 3, characterized in that The phase measured impedance of the reactor meets the low impedance criterion, including using the following judgment equation for judgment: When Z φ <m2Z e When , it is judged as low impedance; in, is the phase measurement impedance of the reactor, Z e is the secondary phase reactance of the reactor; m2 is a constant, which is related to the minimum value of the three-phase current at the head end.

5. The method according to claim 4, characterized in that The waveform of the zero-sequence current generated by the first end of the reactor is unsaturated, and the determination is made through the following steps: Differentiate the zero-sequence current waveform generated by the reactor at the first end; The zero-sequence current waveform generated at the first end of the reactor before and after differentiation is saturated.

6. The method according to claim 5, characterized in that The saturation determination of the zero-sequence current waveform generated by the reactor head end before and after differentiation includes: The number of sampling points that meet the high-setting judgment condition is N1, and the number of sampling points that meet the low-setting judgment condition is N2 in one cycle of the self-generated zero-sequence current at the first end of the pre-differential reactor is counted respectively; When N1≥the first preset number of points, and N2≥the second preset number of points, it is determined that the zero-sequence current waveform generated by the reactor head end is unsaturated; The high set value determination condition and the low set value determination condition include the following formulas: Among them, i K is the current sampling value of the neutral point zero-sequence current, i K.MAX It is the maximum peak value of the sampling value within the previous cycle of the differential of the self-generated zero-sequence current at the first end of the reactor; k1 is a high-value constant, k2 is a low-value constant, k1>k2.

7. The method according to claim 5, characterized in that The saturation determination of the zero-sequence current waveform generated by the reactor head end before and after differentiation includes: The number of sampling points satisfying the high-setting judgment condition is N1, and the number of sampling points satisfying the low-setting judgment condition is N2 in one cycle of the zero-sequence current generated at the first end of the reactor after differentiation; When N1≥the first preset number of points, and N2≥the second preset number of points, it is determined that the zero-sequence current waveform generated by the reactor head end is unsaturated; The high set value determination condition and the low set value determination condition include the following formulas: Among them, Δi K is the current sampling value after differentiation, Δi K.MAX It is the maximum peak value of the sampling value within one cycle after the differentiation of the self-generated zero-sequence current at the first end of the reactor; k1 is a high-value constant, k2 is a low-value constant, k1>k2.

8. The method according to claim 6 or 7, characterized in that: After the determination is made that there is an inter-turn fault in the reactor, a predetermined delay time is delayed and the inter-turn fault protection is activated.

9. A high-voltage shunt reactor turn-to-turn fault identification device, characterized in that: It includes turn-to-turn fault protection start-up module, zone fault judgment module, low impedance judgment module, comprehensive harmonic content judgment module of self-generated zero-sequence current at the first end of the reactor, waveform judgment module of self-generated zero-sequence current at the first end of the reactor, and turn-to-turn fault protection action module; among them, The turn-to-turn fault protection startup module determines whether the turn-to-turn fault protection is started; The in-area fault judgment module judges whether it is an in-area fault; The low impedance judgment module judges whether the phase measurement impedance of the reactor meets the low impedance judgment criterion; The module for judging the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor judges whether the comprehensive harmonic content of the self-generated zero-sequence current at the first end of the reactor is less than the comprehensive harmonic braking coefficient, including judging by using the following judgment equation: Among them, I φ_syn k is the comprehensive harmonic current in the zero-sequence current generated by the reactor at the first end, xb is the comprehensive harmonic braking coefficient, I1 is the fundamental current in the zero-sequence current generated by the reactor at the first end, i n is the sampling value of each point in one cycle, N is the number of sampling points in one cycle, Indicates the phase current at the first end of the reactor; The waveform judgment module of the self-generated zero-sequence current at the first end of the reactor is used to judge whether the waveform of the self-generated zero-sequence current at the first end of the reactor is unsaturated; The inter-turn fault protection action module controls the inter-turn fault protection action when determining that there is an inter-turn fault of the reactor.

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