A method and device for determining a fault line of a high-resistance grounding fault in a distribution network

Abstract

The present invention provides a method and device for determining a fault line of a high-resistance grounding fault in a distribution network, the method comprising: injecting a compensation current into the distribution network through a controllable voltage source; reducing the output voltage amplitude of the controllable voltage source, thereby reducing the compensation current and obtaining the zero-sequence current value of each distribution line after the reduction; determining the fault line according to the zero-sequence current value of each distribution line after the reduction. The present invention adjusts the fault capacitive current compensation amount, injects the compensation current, and then gradually reduces the compensation current, thereby utilizing the current characteristics of the fault line to achieve accurate line selection of the high-resistance grounding fault line. By adopting the fault line selection method of the present invention, the action / alarm threshold of the line selection device can be appropriately increased to avoid erroneous action / alarm of the device, improve the fault characteristic amount during high-resistance grounding, achieve accurate selection of the fault line, and thus quickly remove the fault.

Description

Technical Field

[0001] The present invention relates to the field of distribution network measurement, and in particular to a method and device for determining a fault line of a high-resistance grounding fault in a distribution network. Background Art

[0002] Fault line selection of distribution lines has always been a technical difficulty in distribution systems, especially high-resistance grounding faults. At present, the best application of fault line selection technology for distribution lines is the fault line selection technology of transient recording method, which mainly relies on the phase relationship of transient current waveform at the moment of fault occurrence to distinguish fault lines from non-fault lines and realize fault line selection technology. However, due to the small change of zero-sequence current component in high-resistance grounding faults, and the transient current waveform is easily affected by many factors such as line parameters, system architecture, and on-site environment, the on-site application effect is generally not ideal, the reliability is relatively low, and there are many shortcomings in the existing fault line selection. Summary of the invention

[0003] In order to solve the problems that the zero-sequence current component changes very little during a high-resistance grounding fault, and the transient current waveform is easily affected by multiple factors such as line parameters, system architecture, and field environment, so the field application effect is generally not ideal and the reliability is relatively low, the present invention provides the following technical solutions:

[0004] A first aspect of the present invention provides a method for determining a fault line of a high-resistance grounding fault in a distribution network, wherein the distribution network includes a plurality of distribution lines, including:

[0005] If a high-resistance grounding fault occurs in the distribution network, a compensation current is injected into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line;

[0006] Performing a reduction operation on the output voltage amplitude of the controllable voltage source, thereby reducing the compensation current, and obtaining the zero-sequence current value of each distribution line after the reduction;

[0007] The fault line is determined according to the zero-sequence current values ​​of the distribution lines after reduction.

[0008] In an optional embodiment, before injecting the compensation current into the distribution network through the controllable voltage source, the fault line determination method further includes:

[0009] The compensation current is generated according to the system damping rate during normal operation of the power distribution network.

[0010] In an optional embodiment, the output voltage amplitude of the controllable voltage source is reduced, including:

[0011] The output voltage phase of the controllable voltage source is kept unchanged, and the output voltage amplitude is reduced to a set value.

[0012] In an optional embodiment, the output voltage amplitude of the controllable voltage source is reduced, including:

[0013] After reducing the output voltage amplitude of the controllable voltage source by a set difference, determining whether the difference between the zero-sequence current values ​​of any two distribution lines is greater than a set threshold, and if not, repeating the step of reducing the output voltage amplitude of the controllable voltage source by the set difference until at least one of the zero-sequence current differences of each distribution line is greater than the set threshold;

[0014] The method of determining the fault line according to the zero-sequence current value of each distribution line after the reduction includes:

[0015] The distribution line with the larger zero-sequence current value among the two lines whose difference is greater than the set threshold is determined as the fault line.

[0016] In an optional embodiment, before injecting the compensation current into the distribution network through the controllable voltage source, the fault line determination method further includes:

[0017] Injecting an inductive current into the distribution network through a controllable voltage source to reduce the fault line current to a set current value, wherein the set current value is greater than zero;

[0018] After the set time, the inductive current is reduced, and if the distribution network is still in a high-resistance grounding fault, a step of injecting a compensating current is determined.

[0019] A second aspect of the present invention provides a device for determining a fault line of a high-resistance grounding fault in a distribution network, wherein the distribution network includes a plurality of distribution lines, including:

[0020] A compensation current injection module, if a high-resistance grounding fault occurs in the distribution network, injects a compensation current into the distribution network through a controllable voltage source, so that each distribution line forms a zero-sequence current line;

[0021] A reduction module is used to reduce the output voltage amplitude of the controllable voltage source, thereby reducing the compensation current to obtain the zero-sequence current value of each distribution line after the reduction;

[0022] The fault line determination module determines the fault line according to the zero-sequence current values ​​of the distribution lines after the reduction.

[0023] In an optional embodiment, the fault line determination device further includes:

[0024] The compensation current generating module generates the compensation current according to the system damping rate when the distribution network operates normally.

[0025] In an optional embodiment, the reduction module is specifically used to keep the output voltage phase of the controllable voltage source unchanged and reduce the output voltage amplitude to a set value.

[0026] In an optional embodiment, the reduction module is specifically used to determine whether the difference between the zero-sequence current values ​​of any two distribution lines is greater than a set threshold after reducing the output voltage amplitude of the controllable voltage source by a set difference, and if not, repeat the step of reducing the output voltage amplitude of the controllable voltage source by the set difference until at least one of the zero-sequence current differences of each distribution line is greater than the set threshold;

[0027] The fault line determination module is specifically configured to determine the distribution line with the larger zero-sequence current value among the two lines whose difference is greater than the set threshold as the fault line.

[0028] In an optional embodiment, the fault line determination device further includes:

[0029] An inductive current injection module, which injects an inductive current into the distribution network through a controllable voltage source to reduce the fault line current to a set current value, wherein the set current value is greater than zero;

[0030] The compensation current injection determination module reduces the inductive current after a set time, and if the distribution network is still in a high-resistance grounding fault, determines the step of injecting the compensation current.

[0031] It can be seen from the above technical scheme that the present invention provides a method and device for determining the fault line of a high-resistance grounding fault in a distribution network. When a high-resistance grounding fault occurs in the distribution network, a compensation current is injected into the distribution network, and then the compensation current is gradually reduced. By adjusting the fault capacitive current compensation amount, the current characteristics of the fault line are used to achieve accurate line selection of the high-resistance grounding fault line. By adopting the fault line selection method of the present invention, the action / alarm threshold of the line selection device can be appropriately increased to avoid false action / alarm, improve the fault feature amount during high-resistance grounding, and achieve accurate selection of the fault line, so that the fault can be quickly removed. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 It is one of the flow charts of the method for determining the fault line of a high-resistance grounding fault in a distribution network according to an embodiment of the present invention.

[0034] Figure 2 Schematic diagram of fault current control principle in an embodiment of the present invention.

[0035] Figure 3 It is a schematic diagram of a simplified analysis circuit for controlling fault current by a controllable voltage source in an embodiment of the present invention.

[0036] Figure 4 It is a schematic diagram of controlling the fault current and the zero-sequence current of the fault line by a controllable voltage source in an embodiment of the present invention.

[0037] Figure 5 Schematic diagram of a power distribution network in an embodiment of the present invention.

[0038] Figure 6 It is one of the flow charts of the method for determining the fault line of a high-resistance grounding fault in a distribution network according to an embodiment of the present invention.

[0039] Figure 7 It is a schematic diagram of the EMTP-ATP simulation model in an embodiment of the present invention.

[0040] Figure 8 The method for determining a fault line of a high-resistance grounding fault in a distribution network according to an embodiment of the present invention further includes a flowchart of steps.

[0041] Fig. 9 This is one of the module schematic diagrams of the device for determining a fault line of a high-resistance grounding fault in a distribution network according to an embodiment of the present invention.

[0042] Fig.10 This is the second module schematic diagram of the device for determining a fault line of a high-resistance grounding fault in a distribution network according to an embodiment of the present invention.

[0043] Fig.11 This is the third module schematic diagram of the device for determining a fault line of a high-resistance grounding fault in a distribution network according to an embodiment of the present invention.

[0044] Fig.12 It is a schematic diagram of the structure of an electronic device in an embodiment of the present application. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] The inventors of the present invention have discovered that in order to ensure that the grounding arc in the distribution network can be automatically extinguished, a capacitive current compensation device needs to be configured. The power electronic full current compensation device can achieve zero-sequence current compensation by adjusting the compensating inductive current after a fault occurs. For high-resistance grounding faults, the compensation amount can also be appropriately increased to achieve accurate line selection for high-resistance grounding faults.

[0047] Based on this, a first aspect of the present invention provides a method for determining a fault line of a high-resistance grounding fault in a distribution network, wherein the distribution network includes a plurality of distribution lines, such as Figure 1 As shown, including:

[0048] S1a: If a high-resistance grounding fault occurs in the distribution network, a compensation current is injected into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line;

[0049] S2a: reducing the output voltage amplitude of the controllable voltage source, thereby reducing the compensation current, and obtaining the zero-sequence current value of each distribution line after reduction;

[0050] S3a: Determine the fault line according to the zero-sequence current values ​​of each distribution line after the reduction.

[0051] The present invention provides a method for determining a fault line of a high-resistance grounding fault in a distribution network. The method adjusts the fault capacitive current compensation amount, injects the compensation current, and then gradually reduces the compensation current, thereby utilizing the current characteristics of the fault line to achieve accurate line selection of the high-resistance grounding fault line. By using the fault line selection method of the present invention, the action / alarm threshold of the line selection device can be appropriately increased to avoid erroneous action / alarm of the device, improve the fault feature amount during high-resistance grounding, achieve accurate selection of the fault line, and thus quickly remove the fault.

[0052] It can be understood that the high-resistance grounding fault of the present invention, in theory, high resistance should be understood as 1000 ohms and above. Under actual working conditions, high-resistance faults ranging from several thousand ohms to more than 10,000 ohms are real. Although the proportion of high-resistance faults in grounding faults is small, their harm is relatively large.

[0053] With respect to step S1a, this embodiment can be implemented by a full current compensation device. The schematic diagram of the principle of the full current compensation device is shown in FIG. Figure 2 As shown, the active inverter device is connected between the neutral point and the ground, which can be equivalent to a controllable current source, and the output current is I. It can be understood that this embodiment can also be equivalent to a controllable current source in other ways or directly set a controllable current source, which is not limited here. The three-phase power supply voltage is E A 、E B 、E CIndicates, U0 represents the neutral point voltage, r0 and C0 represent the resistance and capacitance of each phase to ground respectively. Assuming that the single-phase grounding fault occurs in phase C, the voltage at the fault phase power supply is U C , the voltage at the fault point is U f , the fault phase current is I C , the line impedance is Z, the voltage drop from the fault phase power supply to the fault point is ΔU, and the ground fault transition resistance is R f .

[0054] like Figure 2 As shown, when a grounding fault in the distribution network is detected, the required injection current (which can be understood as the aforementioned compensation current) is generated by calculating the system damping rate during normal operation of the distribution network, and the fault grounding current is adjusted by injecting current through the PWM active inverter. The injection current is closed-loop controlled to compensate for the reactive component, active component and harmonic component in the fault current, reduce the fault current to near zero, and achieve 100% arc extinguishing of the instantaneous grounding fault.

[0055] It can be understood that the controllable voltage source is placed in the active inverter, and the imported current of the active inverter can be adjusted by adjusting the output voltage of the controllable voltage source, that is, adjusting the injected current.

[0056] In this aspect, for the full current compensation device of the active inverter, the system containing the controllable voltage source can be simplified to obtain a simplified circuit, such as Figure 3 As shown, the current system has a total of n routes, among which the system's single-phase distributed impedance to ground is Z1, Z2, ... Zn, Z f It is the grounding impedance when a single-phase grounding fault occurs in phase A of a certain line. Point N is the neutral point of the system, and the voltage on it is recorded as (UN). U0 is the controllable voltage source, Z0 is the internal resistance of the controllable voltage source, and Ua, Ub, and Uc are three-phase voltage sources.

[0057] according to Figure 3 Schematic diagram and Figure 4 The schematic diagram of the controllable voltage source controlling the fault current and the zero-sequence current of the fault line can be used to calculate the zero-sequence current of the fault line and the non-fault line, as shown below:

[0058] After compensation, the current output by the controllable voltage source is:

[0059] I os =I a +I b +I c =3U N / Z d +I g (1)

[0060] Fault current I g =(U N +Ua ) / Z f In the formula, U N +U a That is the fault relative voltage to ground. The zero sequence current of the fault line m is:

[0061] I 0m =I am +I bm +I cm =3U N / Z m +(U N +U a ) / Z f

[0062] The zero sequence current of non-fault line j is:

[0063] I 0j =I aj +I bj +I cj =3U N / Z j

[0064] In the present invention, for step S2a, after the controllable voltage source controls the fault current to zero, the output voltage amplitude of the controllable voltage source is gradually reduced to keep the output voltage phase unchanged, then the neutral point voltage U N The amplitude will decrease accordingly. For the fault line, the voltage at the fault point U N +U a Increase, the fault point current increases accordingly, and the zero-sequence current increases. For non-fault lines, the line zero-sequence current decreases. In the extreme, when the output voltage amplitude of the controllable voltage source is zero, the non-fault line zero-sequence current decreases to zero, and the zero-sequence current of the fault line changes to I g =U a / Z f In this process, when the output voltage amplitude of the controllable voltage source continues to decrease, the current at the fault point will be much larger than the current formed by the system's distributed impedance to the ground, and the zero-sequence current of the fault line and the fault current are approximately equal. By reducing the output voltage amplitude of the controllable voltage source, the zero-sequence current of each line and the current at the fault point will change as follows:

[0065] ①The zero-sequence current of the non-fault line gradually decreases;

[0066] ②The zero-sequence current of the fault line gradually increases;

[0067] ③The zero-sequence current and fault current of the fault line tend to be equal.

[0068] It can be understood that in the present aspect, when the fault current is small, such as in high-resistance grounding, the method of temporarily increasing the zero-sequence current injection amount can improve the recognition of the fault characteristic quantity, thereby realizing accurate identification of the fault line.

[0069] In an optional embodiment, before injecting the compensation current into the distribution network through the controllable voltage source, the fault line determination method further includes:

[0070] The compensation current is generated according to the system damping rate during normal operation of the power distribution network.

[0071] In this embodiment, specifically, in the arc suppression coil compensation grounding power grid, the current distribution network usually increases the system damping rate by connecting a damping resistor in series at the neutral point to prevent the occurrence of resonant overvoltage, such as Figure 5 As shown, R0 is the neutral point series resistance, Rs, Rt, Rw are the line leakage resistance, Cs, Ct, Cw are the line-to-ground capacitance, according to the definition of damping rate: the ratio of three-phase to ground conductance to capacitive susceptance, and conductance and susceptance determine the active and reactive components in the system, so it can be known that the damping rate is:

[0072]

[0073] Among them, G0 is the neutral point conductance, which is the reciprocal of the series resistance, that is: G0=1 / R0; 2Gs, Gt, Gw are the line leakage conductance, which are the reciprocal of the leakage resistance, that is: Gs=1 / Rs; Gt=1 / Rr; Gw=1 / Rw; Bs, Bt, Bw are the line-to-ground susceptance, which are not equal in practice, and their relationship with the capacitance is: Bs=ωCs; Bt=ωCt; Bw=ωCw.

[0074] It can be understood that in the present invention, the set value, the set difference and the set threshold can all be reasonably configured according to the inventive concept of this aspect. For example, the set value is 110V, the set difference is 5V, and the set threshold is 8. The present invention does not limit this.

[0075] In this aspect, generating the compensation current according to the system damping rate during normal operation of the distribution network specifically includes:

[0076] In an optional embodiment, the output voltage amplitude of the controllable voltage source is reduced, including:

[0077] The output voltage phase of the controllable voltage source is kept unchanged, and the output voltage amplitude is reduced to a set value.

[0078] In this embodiment, the output voltage amplitude can be reduced once, directly reducing the output voltage amplitude to a suitable set value, which can make the zero-sequence current of the faulty line and the zero-sequence current of the non-faulty line differ greatly, so that the faulty line can be identified intuitively.

[0079] In an optional embodiment, this embodiment provides Figure 1 The specific steps of steps S1a to S3a are as follows: Figure 6 As shown, a method for determining a fault line of a high-resistance grounding fault in a distribution network in this aspect includes:

[0080] S1b: If a high-resistance grounding fault occurs in the distribution network, a compensation current is injected into the distribution network through a controllable voltage source, so that each distribution line forms a zero-sequence current line;

[0081] S2b: after reducing the output voltage amplitude of the controllable voltage source by a set difference, determining whether the difference between the zero-sequence current values ​​of any two distribution lines is greater than a set threshold, if not, repeating the step of reducing the output voltage amplitude of the controllable voltage source by the set difference until at least one of the zero-sequence current differences of each distribution line is greater than the set threshold;

[0082] S3b: Determine the distribution line with the larger zero-sequence current value among the two lines whose difference is greater than the set threshold as the fault line.

[0083] In this embodiment, the voltage amplitude is gradually reduced based on an iterative operation, which can form a certain buffer for the distribution network and avoid the problem of instability of the distribution network caused by excessive reduction. In addition, by gradually reducing the voltage amplitude, when at least one of the zero-sequence current differences is greater than the set threshold, that is, when at least one of the differences in the zero-sequence currents of any two distribution lines is greater than the set threshold, it can be seen that the zero-sequence current of the fault line is significantly different from the zero-sequence current of the non-fault line, thereby eliminating misjudgment caused by interference.

[0084] The simulation verification analysis performed on the above method of the present invention is described in detail below.

[0085] like Figure 7 As shown, using Figure 7 The EMTP-ATP simulation model shown in the figure analyzes the characteristic quantities of each fault. Table 1 shows the changes in the characteristic quantities of the fault line and the non-fault line before and after the full current compensation device is operated.

[0086] Table 1 Changes in fault characteristic quantities before and after the full current compensation device is activated

[0087]

[0088] After the full current device compensates the current at the fault point, the compensation current is mainly injected into the fault point through the fault line. The zero-sequence current of the fault line outlet CT changes from capacitive to inductive, with a large change, while the zero-sequence current of the non-fault line outlet CT changes slightly, with a small change.

[0089] When the line is grounded with high resistance, the capacitive current at the fault point is small, and the inductive injection current of the fully compensated injection device is also relatively low. Taking 500Ω high resistance grounding as an example, as shown in Table 1, the change in zero-sequence current of the fault line outlet CT and the upstream detection unit of the fault point before and after compensation is only about 3.45A. Although it is much higher than the zero-sequence current of the downstream detection unit of the fault point and the non-fault line, it is easy to make a misjudgment in the presence of certain interference. The method of further increasing the injected inductive current in a short time can increase the change in zero-sequence current of the fault line outlet CT and the upstream detection unit of the fault point, making the fault feature more obvious and improving the accuracy of fault line selection and positioning. The results of each feature after increasing the injected inductive current are shown in Table 2.

[0090] Table 2 Changes in fault characteristic quantities after increasing injection current

[0091]

[0092] It can be seen that after increasing the injection amount, the zero-sequence current change of the CT detection unit of the fault line before and after compensation increases to about 10.6A, and the zero-sequence current change of the non-fault line detection unit does not exceed 0.12A, and the fault identification degree is greatly improved.

[0093] Through the above simulation analysis, it can be known that the present invention adjusts the fault capacitive current compensation amount, injects the compensation current, and then gradually reduces the compensation current, thereby utilizing the current characteristics of the fault line to achieve accurate line selection of the high-resistance grounding fault line. By adopting the fault line selection method of the present invention, the action / alarm threshold of the line selection device can be appropriately increased to avoid false operation / alarm of the device, improve the fault characteristic amount during high-resistance grounding, and achieve accurate selection of the fault line, so that the fault can be quickly removed.

[0094] In an optional embodiment, before injecting the compensation current into the distribution network through the controllable voltage source, the fault line determination method is as follows: Figure 8 As shown, it also includes:

[0095] S01: injecting an inductive current into the distribution network through a controllable voltage source to reduce the fault line current to a set current value, wherein the set current value is greater than zero;

[0096] S02: After a set time, the inductive current is reduced, and if the distribution network is still in a high-resistance grounding fault, a step of injecting a compensating current is determined.

[0097] It can be understood that the injection of inductive current into the fault point can be achieved by injecting compensation current into the entire network, so that the entire three-phase circuit is a zero-sequence current loop. At this time, the current property of the fault point changes from capacitive to inductive, that is, the injection of inductive current into the fault point is completed. In addition, the purpose of injecting compensation current is to make the entire three-phase circuit a zero-sequence current loop, so the compensation current is also called zero-sequence current.

[0098] For example, when a ground fault occurs in the system, the full-current device injects an inductive current into the fault point to reduce the current at the fault point to within a set current value (for example, 1A). After waiting for a period of time (for example, 10s), the injected inductive current is gradually reduced to determine whether the fault still exists. If it still exists, the fault is determined to be a permanent ground fault. Then, the zero-sequence current change can be used to determine whether the fault can be accurately located or the line can be selected. If the change is small, the injected inductive current is further increased (the voltage amplitude of the controllable voltage source is reduced, and the inductive current of the fault point increases and changes greatly after the injected compensation current is reduced. After the injected compensation current is reduced, the inductive current of the non-fault point decreases and changes less) until the fault can be accurately located. Finally, the fault is removed according to the system operation mode and the configuration of the automation device, or the inductive current is continuously injected to wait for manual removal of the fault.

[0099] It can be seen from the above technical scheme that by adopting the fault line selection method of the present invention, the action / alarm threshold of the line selection device can be appropriately increased to avoid false action / alarm of the device; the device utilizes the zero-sequence current change characteristics of the fault line and the non-fault line, and by appropriately increasing the zero-sequence current compensation amount (reducing the voltage amplitude of the controllable voltage source, the inductive current of the fault point increases and changes greatly after the injected compensation current decreases, and the inductive current of the non-fault point decreases and changes less after the injected compensation current decreases, then when the zero-sequence current compensation amount is appropriately increased, the inductive current of the fault point changes more, so the fault characteristics are more obvious), the fault characteristic amount during high-resistance grounding is improved, the fault line is accurately selected, and the fault can be quickly removed.

[0100] A second aspect of the present invention provides a device for determining a fault line of a high-resistance grounding fault in a distribution network, wherein the distribution network includes a plurality of distribution lines, such as Fig. 9 As shown, including:

[0101] A compensation current injection module 1, when a high-resistance grounding fault occurs in the distribution network, injects a compensation current into the distribution network through a controllable voltage source, so that each distribution line forms a zero-sequence current line;

[0102] A reduction module 2 performs a reduction operation on the output voltage amplitude of the controllable voltage source, thereby reducing the compensation current, and obtaining a zero-sequence current value of each distribution line after the reduction;

[0103] The fault line determination module 3 determines the fault line according to the zero-sequence current values ​​of the distribution lines after the reduction.

[0104] The present invention provides a fault line determination device for a high-resistance grounding fault in a distribution network. The device adjusts the fault capacitive current compensation amount, injects the compensation current, and then gradually reduces the compensation current, thereby utilizing the current characteristics of the fault line to achieve accurate line selection of the high-resistance grounding fault line. By adopting the fault line selection method of the present invention, the action / alarm threshold of the line selection device can be appropriately increased to avoid false action / alarm of the device, improve the fault feature amount during high-resistance grounding, achieve accurate selection of the fault line, and thus quickly remove the fault.

[0105] It can be understood that the high-resistance grounding fault of the present invention, in theory, high resistance should be understood as 1000 ohms and above. Under actual working conditions, high-resistance faults ranging from several thousand ohms to more than 10,000 ohms are real. Although the proportion of high-resistance faults in grounding faults is small, their harm is relatively large.

[0106] Through the above Figures 2 to 5 As can be seen from the description, in the present invention, after the controllable voltage source controls the fault current to zero, the output voltage amplitude of the controllable voltage source is gradually reduced to keep the output voltage phase unchanged, then the neutral point voltage U N The amplitude will decrease accordingly. For the fault line, the voltage at the fault point U N +U a Increase, the fault point current increases accordingly, and the zero-sequence current increases. For non-fault lines, the line zero-sequence current decreases. In the extreme, when the output voltage amplitude of the controllable voltage source is zero, the non-fault line zero-sequence current decreases to zero, and the zero-sequence current of the fault line changes to I g =U a / Z f In this process, when the output voltage amplitude of the controllable voltage source continues to decrease, the current at the fault point will be much larger than the current formed by the system's distributed impedance to the ground, and the zero-sequence current of the fault line and the fault current will be approximately equal. By reducing the output voltage amplitude of the controllable voltage source, the zero-sequence current of each line and the current at the fault point will change as follows: the zero-sequence current of the non-fault line gradually decreases; the zero-sequence current of the fault line gradually increases; the zero-sequence current of the fault line and the fault current tend to be equal.

[0107] It can be understood that in the present aspect, when the fault current is small, such as in high-resistance grounding, the method of temporarily increasing the zero-sequence current injection amount can improve the recognition of the fault characteristic quantity, thereby realizing accurate identification of the fault line.

[0108] In an optional embodiment, if Fig.10 As shown, the fault line determination device also includes:

[0109] The compensation current generating module 011 generates the compensation current according to the system damping rate when the distribution network operates normally.

[0110] In this embodiment, specifically, in the arc suppression coil compensation grounding power grid, the distribution network usually increases the system damping rate by connecting a damping resistor in series at the neutral point to prevent the occurrence of resonant overvoltage, such as Figure 5 As shown, R0 is the neutral point series resistance, Rs, Rt, Rw are the line leakage resistance, Cs, Ct, Cw are the line-to-ground capacitance, according to the definition of damping rate: the ratio of three-phase to ground conductance to capacitive susceptance, and conductance and susceptance determine the active and reactive components in the system, so it can be known that the damping rate is:

[0111]

[0112] Among them, G0 is the neutral point conductance, which is the reciprocal of the series resistance, that is: G0=1 / R0; 2Gs, Gt, Gw are the line leakage conductance, which are the reciprocal of the leakage resistance, that is: Gs=1 / Rs; Gt=1 / Rr; Gw=1 / Rw; Bs, Bt, Bw are the line-to-ground susceptance, which are not equal in practice, and their relationship with the capacitance is: Bs=ωCs; Bt=ωCt; Bw=ωCw.

[0113] In an optional embodiment, the reduction module is specifically used to keep the output voltage phase of the controllable voltage source unchanged and reduce the output voltage amplitude to a set value.

[0114] In this embodiment, the output voltage amplitude can be reduced once, directly reducing the output voltage amplitude to a suitable set value, which can make the zero-sequence current of the faulty line and the zero-sequence current of the non-faulty line differ greatly, so that the faulty line can be identified intuitively.

[0115] In an optional embodiment, the reduction module is specifically used to determine whether the difference between the zero-sequence current values ​​of any two distribution lines is greater than a set threshold after reducing the output voltage amplitude of the controllable voltage source by a set difference, and if not, repeat the step of reducing the output voltage amplitude of the controllable voltage source by the set difference until at least one of the zero-sequence current differences of each distribution line is greater than the set threshold;

[0116] The fault line determination module is specifically configured to determine the distribution line with the larger zero-sequence current value among the two lines whose difference is greater than the set threshold as the fault line.

[0117] In this embodiment, the voltage amplitude is gradually reduced based on the iterative operation, which can form a certain buffer for the distribution network and avoid the problem of instability of the distribution network caused by excessive reduction. In addition, by gradually reducing the voltage amplitude, when at least one of the zero-sequence current differences is greater than the set threshold, it can be seen that the zero-sequence current of the fault line is significantly different from the zero-sequence current of the non-fault line, thereby eliminating misjudgment caused by interference.

[0118] In an optional embodiment, the fault line determination device, such as Fig.11 As shown, it also includes:

[0119] An inductive current injection module 012 injects an inductive current into the distribution network through a controllable voltage source to reduce the fault line current to a set current value, wherein the set current value is greater than zero;

[0120] The compensation current injection determination module 013 reduces the inductive current after a set time, and if the distribution network is still in a high-resistance grounding fault, determines the step of injecting a compensation current.

[0121] It can be understood that the determining means of this aspect can be Figure 2 The control device of the active inverter outputs a voltage control signal of the active inverter to implement the above steps, which will not be described in detail here.

[0122] From a hardware perspective, the present application provides an embodiment of an electronic device for implementing all or part of the above method, wherein the electronic device specifically includes the following contents:

[0123] Fig.12 FIG. 9 is a schematic block diagram of the system structure of the electronic device 9600 according to an embodiment of the present application. Fig.12 As shown, the electronic device 9600 may include a central processor 9100 and a memory 9140; the memory 9140 is coupled to the central processor 9100. It is worth noting that Fig.12 is exemplary; other types of structures may also be used to supplement or replace this structure to implement telecommunication functions or other functions.

[0124] In one embodiment, the fault line determination device may be integrated into a central processing unit, wherein the central processing unit may be configured to perform the following control:

[0125] S1a: If a high-resistance grounding fault occurs in the distribution network, a compensation current is injected into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line;

[0126] S2a: reducing the output voltage amplitude of the controllable voltage source, thereby reducing the compensation current, and obtaining the zero-sequence current value of each distribution line after reduction;

[0127] S3a: Determine the fault line according to the zero-sequence current values ​​of each distribution line after the reduction.

[0128] This aspect adjusts the fault capacitive current compensation amount, injects the compensation current, and then gradually reduces the compensation current, thereby utilizing the current characteristics of the fault line to achieve accurate line selection of the high-resistance grounding fault line. By adopting the fault line selection method of the present invention, the action / alarm threshold of the line selection device can be appropriately increased to avoid false action / alarm of the device, improve the fault feature amount during high-resistance grounding, and achieve accurate selection of the fault line, so that the fault can be quickly removed.

[0129] In another embodiment, the faulty line determination device may be configured separately from the central processor 9100. For example, the faulty line determination device may be a chip connected to the central processor 9100, and the above interaction may be achieved through the control of the central processor.

[0130] like Fig.12 As shown, the electronic device 9600 may also include: a communication module 9110, an input unit 9120, an audio processor 9130, a display 9160, and a power supply 9170. It is worth noting that the electronic device 9600 does not necessarily have to include Fig.12 In addition, the electronic device 9600 may also include Fig.12 For components not shown, reference may be made to the prior art.

[0131] like Fig.12 As shown, the central processing unit 9100 is sometimes also referred to as a controller or an operation control, and may include a microprocessor or other processor device and / or logic device, which receives input and controls the operation of various components of the electronic device 9600.

[0132] The memory 9140 may be, for example, one or more of a cache, a flash memory, a hard drive, a removable medium, a volatile memory, a non-volatile memory or other suitable devices. The above-mentioned information related to the failure may be stored, and a program for executing the relevant information may also be stored. The CPU 9100 may execute the program stored in the memory 9140 to implement information storage or processing, etc.

[0133] The input unit 9120 provides input to the central processing unit 9100. The input unit 9120 is, for example, a key or a touch input device. The power supply 9170 is used to provide power to the electronic device 9600. The display 9160 is used to display display objects such as images and texts. The display may be, for example, an LCD display, but is not limited thereto.

[0134] The memory 9140 may be a solid-state memory, such as a read-only memory (ROM), a random access memory (RAM), a SIM card, etc. It may also be a memory that saves information even when the power is off, can be selectively erased, and is provided with more data, examples of which are sometimes referred to as EPROMs, etc. The memory 9140 may also be some other type of device. The memory 9140 includes a buffer memory 9141 (sometimes referred to as a buffer). The memory 9140 may include an application / function storage unit 9142, which is used to store application programs and function programs or processes for executing the operation of the electronic device 9600 through the central processor 9100.

[0135] The memory 9140 may also include a data storage unit 9143 for storing data, such as contacts, digital data, pictures, sounds, and / or any other data used by the electronic device. The driver storage unit 9144 of the memory 9140 may include various drivers for communication functions of the electronic device and / or for executing other functions of the electronic device (such as messaging applications, address book applications, etc.).

[0136] The communication module 9110 is a transmitter / receiver 9110 that sends and receives signals via an antenna 9111. The communication module (transmitter / receiver) 9110 is coupled to the central processor 9100 to provide input signals and receive output signals, which may be the same as the case of a conventional mobile communication terminal.

[0137] Based on different communication technologies, multiple communication modules 9110 may be provided in the same electronic device, such as a cellular network module, a Bluetooth module and / or a wireless LAN module, etc. The communication module (transmitter / receiver) 9110 is also coupled to a speaker 9131 and a microphone 9132 via an audio processor 9130 to provide an audio output via the speaker 9131 and receive an audio input from the microphone 9132, thereby realizing a common telecommunication function. The audio processor 9130 may include any suitable buffer, decoder, amplifier, etc. In addition, the audio processor 9130 is also coupled to the central processor 9100, so that recording can be performed on the local machine through the microphone 9132, and the sound stored on the local machine can be played through the speaker 9131.

[0138] The embodiment of the present application also provides a computer-readable storage medium capable of implementing all the steps in the method for determining a faulty line in the above embodiment. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, all the steps in the above embodiment in which the execution subject is the device for determining a faulty line are implemented. For example, when the processor executes the computer program, the following steps are implemented:

[0139] S1a: If a high-resistance grounding fault occurs in the distribution network, a compensation current is injected into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line;

[0140] S2a: reducing the output voltage amplitude of the controllable voltage source, thereby reducing the compensation current, and obtaining the zero-sequence current value of each distribution line after reduction;

[0141] S3a: Determine the fault line according to the zero-sequence current values ​​of each distribution line after the reduction.

[0142] This aspect adjusts the fault capacitive current compensation amount, injects the compensation current, and then gradually reduces the compensation current, thereby utilizing the current characteristics of the fault line to achieve accurate line selection of the high-resistance grounding fault line. By adopting the fault line selection method of the present invention, the action / alarm threshold of the line selection device can be appropriately increased to avoid false action / alarm of the device, improve the fault feature amount during high-resistance grounding, and achieve accurate selection of the fault line, so that the fault can be quickly removed.

[0143] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, devices, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0144] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (apparatus), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0145] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0146] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0147] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for determining a fault line of a high-resistance grounding fault in a distribution network, wherein the distribution network comprises a plurality of distribution lines, characterized in that: include: If a high-resistance grounding fault occurs in the distribution network, a compensation current is injected into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line; Performing a reduction operation on the output voltage amplitude of the controllable voltage source to reduce the compensation current and obtain the zero-sequence current value of each distribution line after the reduction; Determining a faulty line from the plurality of distribution lines according to the zero-sequence current values ​​of the distribution lines after reduction; Wherein, before injecting the compensation current into the distribution network through the controllable voltage source, the method further includes: Injecting an inductive current into the distribution network through a controllable voltage source to reduce the fault line current to a set current value, wherein the set current value is greater than zero; After the set time, the inductive current is reduced, and if the distribution network is still in a high-resistance grounding fault, a step of injecting a compensating current is determined; specifically, fault removal is performed or the inductive current is continuously injected according to the system operation mode and the configuration of the automation device; The step of reducing the output voltage amplitude of the controllable voltage source includes: After reducing the output voltage amplitude of the controllable voltage source by a set difference, determining whether the difference between the zero-sequence current values ​​of any two distribution lines is greater than a set threshold, and if not, repeating the step of reducing the output voltage amplitude of the controllable voltage source by the set difference until at least one of the differences between the zero-sequence current values ​​of any two distribution lines is greater than the set threshold; The step of determining a faulty line from the plurality of distribution lines according to the reduced zero-sequence current values ​​of the distribution lines comprises: The distribution line with the larger zero-sequence current value among the two distribution lines whose difference is greater than the set threshold is determined as the fault line.

2. The method for determining the fault line of a high-resistance grounding fault in a distribution network according to claim 1, characterized in that: Before injecting the compensation current into the power distribution network through the controllable voltage source, the method further includes: The compensation current is generated according to the system damping rate during normal operation of the power distribution network.

3. The method for determining the fault line of a high-resistance grounding fault in a distribution network according to claim 1, characterized in that: The output voltage amplitude of the controllable voltage source is reduced, comprising: The output voltage phase of the controllable voltage source is kept unchanged, and the output voltage amplitude is reduced to a set value.

4. A device for determining a fault line of a high-resistance grounding fault in a distribution network, wherein the distribution network comprises a plurality of distribution lines, characterized in that: include: A compensation current injection module, used for injecting a compensation current into the distribution network through a controllable voltage source if a high-resistance grounding fault occurs in the distribution network, so that each of the distribution lines forms a zero-sequence current line; A reduction module, used for reducing the output voltage amplitude of the controllable voltage source, thereby reducing the compensation current, and obtaining the zero-sequence current value of each distribution line after the reduction; A fault line determination module, used to determine the fault line according to the zero-sequence current value of each distribution line after the reduction; An inductive current injection module, used for injecting an inductive current into the distribution network through a controllable voltage source to reduce the fault line current to a set current value, wherein the set current value is greater than zero; A compensation current injection determination module is used to reduce the inductive current after a set time, and if the distribution network is still in a high-resistance grounding fault, determine the step of injecting the compensation current; specifically, perform fault removal or continue to inject the inductive current according to the system operation mode and the configuration of the automation device; The reduction module is specifically used to determine whether the difference between the zero-sequence current values ​​of any two distribution lines is greater than a set threshold value after reducing the output voltage amplitude of the controllable voltage source by a set difference value, and if not, repeat the step of reducing the output voltage amplitude of the controllable voltage source by the set difference value until at least one of the differences between the zero-sequence current values ​​of any two distribution lines is greater than the set threshold value; The fault line determination module is specifically configured to determine, as the fault line, the distribution line with the larger zero-sequence current value among the two distribution lines whose difference is greater than the set threshold.

5. The fault line determination device for a high-resistance grounding fault in a distribution network according to claim 4, characterized in that: The fault line determination device further comprises: The compensation current generating module is used to generate the compensation current according to the system damping rate when the distribution network operates normally.

6. The fault line determination device for a high-resistance grounding fault in a distribution network according to claim 4, characterized in that: The reduction module is specifically used to keep the output voltage phase of the controllable voltage source unchanged and reduce the output voltage amplitude to a set value.

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