A method and device for locating a high-resistance grounding fault in a distribution network

Abstract

The present invention provides a fault locating method and device for 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; after injecting the compensation current into the distribution network through the controllable voltage source so that each of the distribution lines forms a zero-sequence current line, acquiring the detection current of each current detection point on each distribution line again; locating the fault point of the high-resistance grounding fault according to the detection current of each current detection point acquired twice. The present invention acquires the current before and after the compensation current is injected into each current detection point, and then locates the high-resistance grounding fault point based on the current changes before and after. By injecting the compensation current into both the fault line and the non-fault line, by detecting the current changes of each current detection point, the characteristics of the zero-sequence current change characteristics upstream and downstream of the fault point are utilized to accurately locate the fault point, thereby quickly removing the fault.

Description

Technical Field

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

[0002] Fault line selection for distribution lines has always been a technical difficulty in distribution systems. Currently, the best application of fault location technology for distribution lines is the fault location technology of transient wave recording method, which mainly relies on the phase relationship of transient current waveform at the moment of fault occurrence to distinguish the upstream and downstream of the fault point to achieve fault location technology. However, since the transient current waveform is 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 locating a high-resistance grounding fault in a distribution network, wherein the distribution network includes a plurality of distribution lines, each of which includes a plurality of current detection points, including:

[0005] If a high-resistance grounding fault occurs in the distribution network, the detection current of each current detection point on each distribution line is obtained;

[0006] After injecting a compensation current into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line, the detection current of each current detection point on each distribution line is obtained again;

[0007] The fault point of the high-resistance grounding fault is located according to the detection currents of each current detection point obtained twice.

[0008] In an optional embodiment, before injecting the compensation current into the distribution network through the controllable voltage source, the fault location 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, locating the fault point of the high-resistance grounding fault according to the detection currents of each current detection point obtained twice includes:

[0011] Calculate the current difference between the detection currents obtained twice at each current detection point;

[0012] Finding a current detection point where the current difference is greater than a set threshold, and finding the next current detection point adjacent to the current detection point where the current difference is greater than the set threshold along the current direction on the power distribution line;

[0013] If the current difference corresponding to the next current detection point is smaller than the set threshold, the fault point for locating the high-resistance grounding fault is between the current detection point where the current difference is larger than the set threshold and the next current detection point.

[0014] In an optional embodiment, it also includes:

[0015] The set threshold is determined according to the resistance value of each grounding resistor in the distribution network.

[0016] In an optional embodiment, before injecting the compensation current into the distribution network through the controllable voltage source, the fault location 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 fault location device for a high-resistance grounding fault in a distribution network, wherein the distribution network includes a plurality of distribution lines, each distribution line includes a plurality of current detection points, and the fault location device includes:

[0020] A first detection current acquisition module, which acquires the detection current of each current detection point on each distribution line if a high-resistance grounding fault occurs in the distribution network;

[0021] A second detection current acquisition module, after injecting a compensation current into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line, again acquires the detection current of each current detection point on each distribution line;

[0022] The fault location module locates the fault point of the high-resistance grounding fault according to the detection currents of each current detection point obtained twice.

[0023] In an optional embodiment, the fault locating 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 fault location module includes:

[0026] A current difference calculation unit is used to calculate the current difference between the detection currents obtained twice at each current detection point;

[0027] A search unit, searching for a current detection point where the current difference is greater than a set threshold, and searching for a next current detection point adjacent to the current detection point where the current difference is greater than the set threshold along the current direction on the power distribution line;

[0028] The positioning unit locates the fault point of the high-resistance grounding fault between the current detection point where the current difference is greater than the set threshold and the next current detection point if the current difference corresponding to the next current detection point is less than the set threshold.

[0029] In an optional embodiment, it also includes:

[0030] A threshold determination module is set to determine the set threshold according to the resistance value of each grounding resistor in the distribution network.

[0031] In an optional embodiment, the fault locating device further includes:

[0032] 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;

[0033] 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.

[0034] It can be seen from the above technical scheme that the present invention provides a fault locating method and device for a high-resistance grounding fault in a distribution network. When a high-resistance grounding fault occurs in the distribution network, the current before and after the compensation current is injected into each current detection point is obtained, and then the high-resistance grounding fault point is located based on the current changes before and after. With this fault identification and locating method, since after the compensation current is injected, the zero-sequence current upstream of the fault point changes from capacitive to inductive, and the change amount is large, the action / alarm threshold of the automation device and the fault indicator can be appropriately increased to avoid false action / alarm of the device; the present invention uses the compensation current injected into both the fault line and the non-fault line, detects the current changes at each current detection point, and uses the characteristics of the zero-sequence current change characteristics upstream and downstream of the fault point to accurately locate the fault point, thereby quickly eliminating the fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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.

[0036] Figure 1 It is a flow chart of a method for locating a high-resistance grounding fault in a distribution network according to an embodiment of the present invention.

[0037] Figure 2 Schematic diagram of fault current control principle in an embodiment of the present invention.

[0038] 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.

[0039] 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.

[0040] Figure 5 Schematic diagram of a power distribution network in an embodiment of the present invention.

[0041] Figure 6 In the embodiment of the present invention Figure 1 Schematic diagram of the specific process of step S3.

[0042] Figure 7 It is a schematic diagram of the EMTP-ATP simulation model in an embodiment of the present invention.

[0043] Figure 8 The method for locating a high-resistance grounding fault in a distribution network according to an embodiment of the present invention further includes a flowchart of steps.

[0044] Fig. 9 This is one of the module schematic diagrams of the fault locating device for high-resistance grounding fault in the distribution network according to the embodiment of the present invention.

[0045] Fig.10 This is the second module schematic diagram of the fault locating device for high-resistance grounding fault in the distribution network according to the embodiment of the present invention.

[0046] Fig.11 This is the third module schematic diagram of the fault locating device for high-resistance grounding fault in the distribution network according to the embodiment of the present invention.

[0047] Fig.12 It is a schematic diagram of the structure of an electronic device in an embodiment of the present application. DETAILED DESCRIPTION

[0048] 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.

[0049] 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.

[0050] Based on this, a first aspect of the present invention provides a method for locating a high-resistance ground fault in a distribution network, wherein the distribution network includes a plurality of distribution lines, such as Figure 1 As shown, including:

[0051] S1: If a high-resistance grounding fault occurs in the distribution network, the detection current of each current detection point on each distribution line is obtained;

[0052] S2: After injecting a compensation current into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line, the detection current of each current detection point on each distribution line is obtained again;

[0053] S3: Locating the fault point of the high-resistance grounding fault according to the detection currents of each current detection point obtained twice.

[0054] The present invention provides a fault location method for a high-resistance grounding fault in a distribution network. The method obtains the current before and after the compensation current is injected into each current detection point, and then locates the high-resistance grounding fault point based on the current changes before and after. With this fault identification and location method, since after the compensation current is injected, the zero-sequence current upstream of the fault point changes from capacitive to inductive, and the change amount is large, the action / alarm threshold of the automation device and the fault indicator can be appropriately increased to avoid false action / alarm of the device. The present invention injects compensation current into both the fault line and the non-fault line, detects the current changes at each current detection point, and utilizes the characteristics of the zero-sequence current change characteristics upstream and downstream of the fault point to accurately locate the fault point, thereby quickly removing the fault.

[0055] 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.

[0056] In step S2, the compensation current source can be injected through a controllable voltage source. Specifically, in some embodiments, the full current compensation device can be equivalent to a controllable voltage source to achieve compensation current injection. Figure 2 As shown, the active inverter device is connected between the neutral point and the ground, which is equivalent to a controllable current source with an output current of I. The three-phase power supply voltage is E A 、E B 、E C Indicates, 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 .

[0057] like Figure 2 As shown, in step S1, when a grounding fault in the distribution network is detected, the required injection 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.

[0058] It can be understood that the controllable voltage source is placed in the active inverter, and the input current of the active inverter can be adjusted by adjusting the output voltage of the controllable voltage source.

[0059] 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, where 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.

[0060] 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:

[0061] After compensation, the current output by the controllable voltage source is:

[0062] I os =I a +I b +I c =3U N / Z d +I g (1)

[0063] Fault current I g =(U N +U a ) / 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:

[0064] I 0m =I am +I bm +I cm =3UN / Z m +(U N +U a ) / Z f

[0065] The zero sequence current of non-fault line j is:

[0066] I 0j =I aj +I bj +I cj =3U N / Z j

[0067] Fault location methods such as Figure 4 As shown, by installing zero-sequence current monitoring devices distributed on the distribution lines, after the full current compensation device compensates the capacitive current, the difference in zero-sequence current in each section of the line is detected, and the fault location of the single-phase grounding fault point can be performed. It can be understood that in the case of small fault currents such as high-resistance grounding, the method of temporarily increasing the zero-sequence current injection amount can improve the recognition of the fault feature quantity, thereby realizing accurate identification of the fault line.

[0068] In step S1, according to Figure 4 , before and after the ground fault point, CT1 and CT2, after the fault occurs, before the full current compensation device is activated, since all line-to-ground capacitances inject capacitive current into the fault point, the closer the fault line detection point is to the fault point, the higher the zero-sequence current. In step S2, after the full compensation device is activated, due to the injection of inductive current, the zero-sequence current at the detection point (CT1) upstream of the fault point changes from capacitive to inductive, with a large change, while the zero-sequence current at the downstream detection point (CT2, CT3) and the non-fault line detection point changes very little.

[0069] In an optional embodiment, before injecting the compensation current into the distribution network through the controllable voltage source, the fault location 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 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] In this aspect, generating the compensation current according to the system damping rate during normal operation of the distribution network specifically includes:

[0075] In an optional embodiment, if Figure 6 As shown, step S3 specifically includes:

[0076] S31: Calculate the current difference between the detection currents obtained twice at each current detection point;

[0077] S32: searching for a current detection point where the current difference is greater than a set threshold, and searching for the next current detection point adjacent to the current detection point where the current difference is greater than the set threshold along the current direction on the power distribution line;

[0078] S33: If the current difference corresponding to the next current detection point is smaller than the set threshold, the fault point of the high-resistance grounding fault is located between the current detection point where the current difference is larger than the set threshold and the next current detection point.

[0079] In this embodiment, in step S31 and S32 of step S3, according to Figure 4, before and after the ground fault point, CT1 and CT2, after the fault occurs, before the full current compensation device is activated, since all line-to-ground capacitances inject capacitive current into the fault point, the closer the fault line detection point is to the fault point, the higher the zero-sequence current. After the full compensation device is activated, due to the injection of inductive current, the zero-sequence current of the upstream detection point (CT1) of the fault point changes from capacitive to inductive, and the change is large, while the zero-sequence current of the downstream detection point (CT2, CT3) and the non-fault line detection point changes very little. Therefore, through the above steps, the zero-sequence current of the upstream detection point of the fault changes greatly, while the zero-sequence current of the downstream detection point changes less, and the zero-sequence voltage of the non-fault line detection point changes less. Then, it can be judged by setting a reasonable set threshold. When the difference between the front and rear is greater than the set threshold, this detection point can be identified as the upstream detection point of the fault point, and then the downstream detection point is further characterized. The change of the downstream detection point should be small, and then the fault point of the high-resistance fault is determined.

[0080] The simulation verification analysis performed on the above method of the present invention is described in detail below.

[0081] 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, where the fault point is set between detection point 2 and detection point 3.

[0082] Table 1 Changes in fault characteristic quantities before and after the full current compensation device is activated

[0083]

[0084] 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.

[0085] For the convenience of observation, four detection points are set on each line, and the fault characteristics are analyzed by detecting the zero-sequence current at the location. The fault point is set between detection points 2 and 3. It can be seen that after the fault occurs, before the full current compensation device is activated, all line-to-ground capacitances inject capacitive current into the fault point. Therefore, the closer the fault line detection point is to the fault point, the higher the zero-sequence current. After the full compensation device is activated, due to the injection of inductive current, the zero-sequence current upstream of the fault point changes from capacitive to inductive, and the change is large. The change of zero-sequence current at the downstream detection point and the non-fault line detection point is very small. It can be seen from Table 1 that when the fault resistance is 5Ω, the change of zero-sequence current at fault line detection points 1 and 2 is about 17.6A, and the change of zero-sequence current at fault line detection points 3 and 4 and non-fault line detection points 1 and 2 does not exceed 0.05A. Therefore, the difference in zero-sequence current change between the upstream detection point of the fault point and the downstream and non-fault line detection points can be used to effectively identify the location of the fault point and realize fault location.

[0086] When high-resistance grounding occurs in the line, 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, the change in zero-sequence current of the fault line outgoing CT and the upstream detection unit of the fault point before and after compensation is about 3.45A, which is much higher than the zero-sequence current of the downstream detection unit of the fault point and the non-fault line.

[0087] In an optional embodiment, before injecting the compensation current into the distribution network through the controllable voltage source, the fault location method, such as Figure 8 As shown, it also includes:

[0088] 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;

[0089] 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.

[0090] For example, when a ground fault occurs in the system, the full-current device injects 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 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. The fault is located according to the change in zero-sequence current. Finally, the fault is removed or the inductive current is continuously injected to wait for manual removal of the fault based on the system operation mode and the configuration of the automation device.

[0091] 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, improves the fault characteristic amount during high-resistance grounding, thereby realizing accurate selection of the fault line, thereby quickly eliminating the fault.

[0092] A second aspect of the present invention provides a fault location device for 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:

[0093] A first detection current acquisition module 1 is used to acquire the detection current of each current detection point on each distribution line if a high-resistance grounding fault occurs in the distribution network;

[0094] A second detection current acquisition module 2, which injects a compensation current into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line, and then acquires the detection current of each current detection point on each distribution line again;

[0095] The fault location module 3 locates the fault point of the high-resistance grounding fault according to the detection currents of each current detection point obtained twice.

[0096] The present invention provides a fault locating device for a high-resistance grounding fault in a distribution network. The device obtains the current before and after the compensation current is injected into each current detection point, and then locates the high-resistance grounding fault point based on the current changes before and after. With this fault identification and locating method, since after the compensation current is injected, the zero-sequence current upstream of the fault point changes from capacitive to inductive, and the change amount is large, the action / alarm threshold of the automation device and the fault indicator can be appropriately increased to avoid false action / alarm of the device. The present invention injects compensation current into both the fault line and the non-fault line, detects the current changes at each current detection point, and utilizes the characteristics of the zero-sequence current change characteristics upstream and downstream of the fault point to accurately locate the fault point, thereby quickly removing the fault.

[0097] 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.

[0098] 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 UN +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.

[0099] 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.

[0100] In an optional embodiment, if Fig.10 As shown, the fault locating device also includes:

[0101] The compensation current generating module 011 generates the compensation current according to the system damping rate when the distribution network operates normally.

[0102] 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:

[0103]

[0104] 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.

[0105] In an optional embodiment, the second detection current acquisition 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.

[0106] 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.

[0107] In an optional embodiment, the fault location module includes:

[0108] A current difference calculation unit is used to calculate the current difference between the detection currents obtained twice at each current detection point;

[0109] A search unit, searching for a current detection point where the current difference is greater than a set threshold, and searching for a next current detection point adjacent to the current detection point where the current difference is greater than the set threshold along the current direction on the power distribution line;

[0110] The positioning unit locates the fault point of the high-resistance grounding fault between the current detection point where the current difference is greater than the set threshold and the next current detection point if the current difference corresponding to the next current detection point is less than the set threshold.

[0111] In this embodiment, according to Figure 4 , before and after the ground fault point, CT1 and CT2, after the fault occurs, before the full current compensation device is activated, since all line-to-ground capacitances inject capacitive current into the fault point, the closer the fault line detection point is to the fault point, the higher the zero-sequence current. After the full compensation device is activated, due to the injection of inductive current, the zero-sequence current of the upstream detection point (CT1) of the fault point changes from capacitive to inductive, and the change is large, while the zero-sequence current of the downstream detection point (CT2, CT3) and the non-fault line detection point changes very little. Therefore, through the above steps, the zero-sequence current of the upstream detection point of the fault changes greatly, while the zero-sequence current of the downstream detection point changes less, and the zero-sequence voltage of the non-fault line detection point changes less. Then, it can be judged by setting a reasonable set threshold. When the difference between the front and rear is greater than the set threshold, this detection point can be identified as the upstream detection point of the fault point, and then the downstream detection point is further characterized. The change of the downstream detection point should be small, and then the fault point of the high-resistance fault is determined.

[0112] In an optional embodiment, the fault location device, such as Fig.11 As shown, it also includes:

[0113] 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;

[0114] 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.

[0115] 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.

[0116] 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:

[0117] 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.

[0118] In one embodiment, the fault location device may be integrated into a central processing unit, wherein the central processing unit may be configured to perform the following control:

[0119] S1: If a high-resistance grounding fault occurs in the distribution network, the detection current of each current detection point on each distribution line is obtained;

[0120] S2: After injecting a compensation current into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line, the detection current of each current detection point on each distribution line is obtained again;

[0121] S3: Locating the fault point of the high-resistance grounding fault according to the detection currents of each current detection point obtained twice.

[0122] This aspect obtains the current before and after the compensation current is injected into each current detection point, and then locates the high-resistance grounding fault point based on the current changes before and after. This fault identification and positioning method is used. After the compensation current is injected, the zero-sequence current upstream of the fault point changes from capacitive to inductive, and the change is large. Therefore, the action / alarm threshold of the automation device and the fault indicator can be appropriately increased to avoid false action / alarm of the device. The present invention injects compensation current into both the fault line and the non-fault line, detects the current changes at each current detection point, and utilizes the characteristics of the zero-sequence current change characteristics upstream and downstream of the fault point to accurately locate the fault point, thereby quickly eliminating the fault.

[0123] In another embodiment, the fault location device may be configured separately from the central processing unit 9100. For example, the fault location device may be a chip connected to the central processing unit 9100, and the above interaction may be achieved through the control of the central processing unit.

[0124] 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.

[0125] 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. The central processing unit 9100 receives input and controls the operation of various components of the electronic device 9600.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.).

[0130] 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.

[0131] 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.

[0132] The embodiments of the present application also provide a computer-readable storage medium capable of implementing all the steps in the fault location method in the above embodiments. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, all the steps in the above embodiments in which the execution subject is the fault location device are implemented. For example, when the processor executes the computer program, the following steps are implemented:

[0133] S1: If a high-resistance grounding fault occurs in the distribution network, the detection current of each current detection point on each distribution line is obtained;

[0134] S2: After injecting a compensation current into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line, the detection current of each current detection point on each distribution line is obtained again;

[0135] S3: Locating the fault point of the high-resistance grounding fault according to the detection currents of each current detection point obtained twice.

[0136] This aspect obtains the current before and after the compensation current is injected into each current detection point, and then locates the high-resistance grounding fault point based on the current changes before and after. This fault identification and positioning method is used. After the compensation current is injected, the zero-sequence current upstream of the fault point changes from capacitive to inductive, and the change is large. Therefore, the action / alarm threshold of the automation device and the fault indicator can be appropriately increased to avoid false action / alarm of the device. The present invention injects compensation current into both the fault line and the non-fault line, detects the current changes at each current detection point, and utilizes the characteristics of the zero-sequence current change characteristics upstream and downstream of the fault point to accurately locate the fault point, thereby quickly eliminating the fault.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0141] 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 locating a high-resistance grounding fault in a distribution network, characterized in that: The distribution network includes a plurality of distribution lines, each distribution line includes a plurality of current detection points, and the fault location method includes: If a high-resistance grounding fault occurs in the distribution network, the detection current of each current detection point on each distribution line is obtained; After injecting a compensation current into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line, the detection current of each current detection point on each distribution line is obtained again; Locating the fault point of the high-resistance grounding fault according to the detection currents of each current detection point obtained twice; Wherein, locating the fault point of the high-resistance grounding fault according to the detection currents of each current detection point obtained twice includes: Calculate the current difference between the detection currents obtained twice at each current detection point; Finding a current detection point where the current difference is greater than a set threshold, and finding the next current detection point adjacent to the current detection point where the current difference is greater than the set threshold along the current direction on the power distribution line; If the current difference corresponding to the next current detection point is smaller than the set threshold, the fault point for locating the high-resistance grounding fault is between the current detection point where the current difference is larger than the set threshold and the next current detection point.

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

3. The fault location method for a high-resistance grounding fault in a distribution network according to claim 1, characterized in that: Also includes: The set threshold is determined according to the resistance value of each grounding resistor in the distribution network.

4. The method for locating 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: 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.

5. A fault location device for high-resistance grounding faults in a distribution network, wherein the distribution network comprises a plurality of distribution lines, each of which comprises a plurality of current detection points, characterized in that: The fault locating device comprises: A first detection current acquisition module is used to obtain the detection current of each current detection point on each distribution line if a high-resistance grounding fault occurs in the distribution network; A second detection current acquisition module is used to inject a compensation current into the distribution network through a controllable voltage source so that each distribution line forms a zero-sequence current line, and then obtain the detection current of each current detection point on each distribution line again; A fault locating module, used for locating the fault point of the high-resistance grounding fault according to the detection currents of each current detection point obtained twice; Wherein, the fault location module includes: A current difference calculation unit, used for calculating the current difference of the detection current obtained twice at each current detection point; A search unit, used to search for a current detection point where the current difference is greater than a set threshold, and search for a next current detection point adjacent to the current detection point where the current difference is greater than the set threshold along the current direction on the power distribution line; A positioning unit is used to locate the fault point of the high-resistance grounding fault between the current detection point where the current difference is greater than the set threshold and the next current detection point if the current difference corresponding to the next current detection point is less than the set threshold.

6. The fault location device for high-resistance grounding fault in distribution network according to claim 5, characterized in that: The fault locating 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.

7. The fault location device for high-resistance grounding fault in distribution network according to claim 5, characterized in that: Also includes: A threshold determination module is set, which is used to determine the set threshold according to the resistance value of each grounding resistor in the distribution network.

8. The fault location device for high-resistance grounding fault in distribution network according to claim 5, characterized in that: The fault locating device further comprises: 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; The compensation current injection determination module is used to reduce the inductive current after a set time period, and if the distribution network is still in a high-resistance grounding fault, determine the step of injecting the compensation current.

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