Converter station filter capacitor tower bird damage fault discrimination method

Abstract

The invention belongs to the technical field of electric power facility protection, and particularly relates to a converter station filter capacitor tower bird damage fault discrimination method, which comprises the following steps: acquiring unbalance currents Iua, Iub and Iuc of a, b and c phases of a to-be-discriminated filter capacitor tower, increasing an internal fault threshold value Iinterval, and if any one of the unbalance currents Iua, Iub and Iuc of the phases exceeds the internal fault current threshold value Iinterval, judging whether the to-be-discriminated filter capacitor tower is a bird damage fault or not. The filter capacitor of the converter station has a fault; a new impedance protection method is introduced to judge whether a bird trouble fault occurs or not, and if the impedance deviation rate of any phase exceeds an impedance deviation rate threshold epsilon n and the impedance deviation rate # imgabs0 # of each phase does not exceed the threshold, it is indicated that the bird trouble fault or an internal fault occurs; if any one of the unbalanced currents Iua, Iub and Iuc exceeds an external fault current threshold value Iexternal, it is indicated that a bird trouble fault occurs, and troubleshooting personnel can determine the fault type at the first time and carry out maintenance for different fault types, so that the maintenance efficiency is improved, and maintenance delay is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of protection of filter capacitor towers in converter stations, and in particular relates to a method for distinguishing bird damage faults of filter capacitor towers in converter stations. Background Art

[0002] As a key node in the power transmission system, the stable operation of the high-voltage DC converter station is crucial to the safety of the entire power grid. As an important component of the converter station, the AC filter capacitor undertakes the important tasks of eliminating harmonic interference and realizing reactive power compensation, and plays an irreplaceable role in ensuring the normal operation of the converter station.

[0003] However, with the significant improvement of the ecological environment in Northwest my country, bird activities have become increasingly frequent, which has brought new challenges to the safe operation of converter stations. Birds' docking, nesting and bird droppings on AC filter capacitor towers not only increase the maintenance cost of equipment, but also seriously threaten the safe and stable operation and power transmission efficiency of high-voltage DC transmission systems.

[0004] The traditional electrical quantity-based filter capacitor tower protection method mainly detects the occurrence of faults by identifying abnormal changes in electrical signals such as current and voltage caused by component failures. However, when faced with the special fault type of bird damage, it is impossible to accurately distinguish between bird damage and component failures, resulting in delays in fault investigation and maintenance work. Summary of the invention

[0005] In view of this, the present invention provides a method for distinguishing bird damage faults in a converter station filter capacitor tower to solve the technical problem in the prior art that fault investigation and maintenance work are delayed due to the inability to accurately distinguish between bird damage faults and component faults.

[0006] To achieve the above objectives, this application adopts the following scheme:

[0007] A method for distinguishing bird damage to a converter station filter capacitor tower comprises the following steps:

[0008] S10. Obtain the three-phase voltage V of the filter capacitor tower to be identified, a, b, c a 、V b 、V c , Neutral point voltage V n , a, b, c three-phase current I a ,I b ,I c And the unbalanced current I of phases a, b, and c ua ,I ub ,I uc ;

[0009] S20. Calculate the internal fault current threshold I of the filter capacitor tower to be identifiedinternal ;

[0010] S30. Calculate the external fault current threshold I of the filter capacitor tower to be identified external , the external fault current threshold I external Greater than the internal fault current threshold I internal ;

[0011] S40. According to the three-phase voltages a, b, and c a 、V b 、V c And the three-phase currents a, b, c I a ,I b ,I c Calculate the measured impedance of each phase of phase a, b, and c And obtain the standard impedance Z of each phase a, b, and c ideal ;

[0012] S50. According to the measured impedance of each phase of a, b, c The standard impedance Z of each phase of the corresponding a, b, and c phases ideal Calculate the corresponding impedance deviation rate of each phase And obtain the impedance deviation rate threshold ε n ;

[0013] S60. The unbalanced current I of each phase ua ,I ub ,I uc With the internal fault current threshold I internal By comparison, if the unbalanced current I ua ,I ub ,I uc The internal fault current threshold I internal , it means that no fault has occurred. If the unbalanced current I ua ,I ub ,I uc The unbalanced current of any phase exceeds the internal fault current threshold I internal , then execute step S70;

[0014] S70. The impedance deviation rate of each phase The impedance deviation rate threshold ε n For comparison, if the impedance deviation rate of each phase The impedance deviation rate of any phase exceeds the impedance deviation rate threshold ε n , it means that the fault is an external direct discharge fault. If the impedance deviation rate of each phase is None of them exceeds the impedance deviation rate threshold ε n, it indicates that the fault is a bird damage fault or an internal fault, and step S80 is executed;

[0015] S80. Compare the unbalanced current of each phase with the external fault current threshold I external By comparison, if the unbalanced current of each phase does not exceed the external fault current threshold I external , it indicates that an internal fault has occurred. If the unbalanced current of each phase exceeds the external fault current threshold I external , it means that the fault is a bird damage fault.

[0016] Preferably, the internal fault current threshold I internal It is obtained by the following formula:

[0017] I internal =K Ⅰ I f1

[0018] Where: I internal : Internal fault current threshold / A, K Ⅰ : Small fixed value reliability coefficient, I f1 : Inherent unbalanced current during normal operation / A.

[0019] Preferably, the external fault current threshold I external It is obtained by the following formula:

[0020] I external =K Ⅱ I f2

[0021] Where: I external : External fault current threshold / A, K Ⅱ : Large fixed value reliability coefficient, I f2 : Unbalanced current during external high resistance fault / A.

[0022] Preferably, the measured impedance of the three phases a, b and c is It is obtained by the following formula:

[0023]

[0024] Where: a, b, c three-phase, Phase measurement impedance / Ω, Phase voltage / V, V n : Neutral point voltage / V, Phase current / A.

[0025] Preferably, the impedance deviation rate of each phase It is obtained by the following formula:

[0026]

[0027] Where: a, b, c three-phase, Phase impedance deviation rate, Phase measurement impedance / Ω, Z ideal : Standard impedance of each phase / Ω.

[0028] Preferably, the impedance deviation rate threshold ε n Determined based on the maximum impedance deviation rate that can be caused by external bird damage.

[0029] Preferably, the standard impedance Z ideal It is obtained by the following formula:

[0030]

[0031] Where: a, b, c three-phase, Z ideal :Each phase measured impedance / Ω, Normal operation without faults Phase voltage / V, V n ': Neutral point voltage during normal operation without faults / V, Normal operation without faults Phase current / A.

[0032] The technical solution adopted in this application can achieve the following beneficial effects:

[0033] The present invention provides a method for distinguishing bird damage to a converter station filter capacitor tower, and obtains the a, b, c three-phase voltage V of the filter capacitor tower to be distinguished. a 、V b 、V c , Neutral point voltage V n , a, b, c three-phase current I a ,I b ,I c And the unbalanced current I of phases a, b, and c ua ,I ub ,I uc , the internal fault threshold I internal , can reflect any minor faults in the filter capacitor tower, thereby determining whether a fault has occurred. If the unbalanced current I ua ,I ub ,I uc The unbalanced current in any phase exceeds the internal fault current threshold I internal, the capacitance value of the H bridge arm of each phase capacitor changes, the capacitance values ​​of the four bridge arms are no longer equal, the H bridge is no longer balanced, and an unbalanced current appears in the middle of the H bridge, indicating that the converter station filter capacitor has a fault; by introducing a new impedance protection method to judge whether the fault is a bird damage fault, calculate the impedance deviation rate of each phase The impedance deviation rate threshold ε is determined based on the maximum impedance deviation rate that can be caused by external bird damage. n ; If the impedance deviation rate of each phase None of them exceeds the impedance deviation rate threshold ε n , indicating that a bird damage fault or an internal fault has occurred. If the unbalanced current I ua ,I ub ,I uc The unbalanced current in any phase exceeds the external fault current threshold I external , it means that a bird damage fault has occurred. An internal fault is just a breakdown of individual components inside a single capacitor unit, causing a small unbalanced current. A bird damage fault will cause multiple capacitor units to short-circuit, causing a larger unbalanced current than an internal fault. The present invention can accurately distinguish between bird damage faults and component faults, and troubleshooters can determine the type of fault that has occurred at the first time. Maintenance personnel can perform maintenance according to different fault types, thereby improving maintenance efficiency and avoiding losses caused by maintenance delays. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Flow chart of the identification method of the present invention.

[0035] Figure 2 This is the structural diagram of the filter capacitor tower model.

[0036] Figure 3 It is the three-phase current and three-phase unbalanced current when bird damage occurs.

[0037] Figure 4 It indicates the exceeding of limit conditions of three protection signals when bird damage occurs. DETAILED DESCRIPTION

[0038] In order to facilitate the understanding of the present application, the present application will be described more comprehensively below in conjunction with the accompanying drawings. And the preferred implementation of the present application is given. However, the present application can be implemented in many different forms and is not limited to the implementation described herein. On the contrary, the purpose of providing these implementations is to make the disclosure of the present application more thoroughly and comprehensively understood.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0040] This embodiment provides a method for determining bird damage to a converter station filter capacitor tower, comprising the following steps:

[0041] S10. Obtain the three-phase voltage V of the filter capacitor tower to be identified, a, b, c a 、V b 、V c , Neutral point voltage V n , a, b, c three-phase current I a ,I b ,I c And the unbalanced current I of phases a, b, and c ua ,I ub ,I uc ;

[0042] S20. Calculate the internal fault current threshold I of the filter capacitor tower to be identified internal ;

[0043] S30. Calculate the external fault current threshold I of the filter capacitor tower to be identified external , the external fault current threshold I external Greater than the internal fault current threshold I internal ;

[0044] S40. According to the three-phase voltages a, b, and c a 、V b 、V c And the three-phase currents a, b, c I a ,I b ,I c Calculate the measured impedance of each phase of phase a, b, and c And obtain the standard impedance Z of each phase a, b, and c ideal ;

[0045] S50. According to the measured impedance of each phase of a, b, c The standard impedance Z of each phase of the corresponding a, b, and c phases ideal Calculate the corresponding impedance deviation rate of each phase And calculate the impedance deviation rate threshold ε n ;

[0046] S60. The unbalanced current I of each phaseua ,I ub ,I uc With the internal fault current threshold I internal By comparison, if the unbalanced current I ua ,I ub ,I uc The internal fault current threshold I internal , it means that no fault has occurred. If the unbalanced current I ua ,I ub ,I uc The unbalanced current of any phase exceeds the internal fault current threshold I internal , then execute step S70;

[0047] S70. The impedance deviation rate of each phase The impedance deviation rate threshold ε n For comparison, if the impedance deviation rate of each phase The impedance deviation rate of any phase exceeds the impedance deviation rate threshold ε n , it means that the fault is an external direct discharge fault. If the impedance deviation rate of each phase is None of them exceeds the impedance deviation rate threshold ε n , it indicates that the fault is a bird damage fault or an internal fault, and step S80 is executed;

[0048] S80. Compare the unbalanced current of each phase with the external fault current threshold I external By comparison, if the unbalanced current of each phase does not exceed the external fault current threshold I external , it indicates that an internal fault has occurred. If the unbalanced current of each phase exceeds the external fault current threshold I external , it means that the fault is a bird damage fault.

[0049] In the method for distinguishing bird damage to the filter capacitor tower of the converter station provided in this embodiment, first, according to the electrical quantity measurement points of the filter capacitor tower in the actual project, the three-phase voltage V a, b, and c of the filter capacitor tower to be distinguished is obtained. a 、V b 、V c , Neutral point voltage V n , a, b, c three-phase current I a ,I b ,I c And the unbalanced current I of phases a, b, and c ua ,I ub ,I uc Then, on the one hand, the traditional unbalanced protection method is improved. First, a new current threshold is added, and the traditional current threshold is changed to the internal fault threshold Iinternal , its set value is relatively small, and is set according to the inherent unbalanced current during normal operation. internal The judgment can reflect any minor fault of the capacitor tower, so as to judge whether the converter station filter capacitor tower has a fault; then, add the external fault current threshold I external , whose fixed value is relatively large, according to the external fault current threshold I external The judgment can distinguish the internal fault and external fault of the capacitor tower. It is set according to the minimum current when the external fault occurs, which is generally an external high-resistance fault; the unbalanced current I ua ,I ub ,I uc With the internal fault current threshold I internal By comparison, if the phase unbalanced current I ua ,I ub ,I uc The internal fault current threshold I internal , it means that there is no fault in the converter station filter capacitor tower. If the unbalanced current I ua ,I ub ,I uc The unbalanced current in any phase exceeds the internal fault current threshold I internal , it means that the filter capacitor of the converter station has a fault. In the case of normal operation without faults, the capacitance values ​​of the four bridge arms on the capacitor H bridge of each phase are equal and in a balanced state, so there is no unbalanced current in the middle of the H bridge. When a fault occurs, the capacitance value on the bridge arm changes, and the capacitance values ​​on the four bridge arms are no longer equal. The H bridge is no longer balanced, and an unbalanced current appears in the middle of the H bridge. By setting a fixed value, when the unbalanced current exceeds the fixed value, it can be considered that the capacitor has a fault. It is necessary to continue to determine whether the fault is a bird damage fault through the following methods;

[0050] On the other hand, a new impedance protection method is introduced to calculate the impedance of each phase. And the standard impedance Z of each phase ideal , according to the impedance of each phase And the standard impedance Z of each phase ideal Calculate the corresponding impedance deviation rate of each phase The impedance deviation rate threshold ε is determined based on the maximum impedance deviation rate that can be caused by external bird damage. n ; If the impedance deviation rate of any phase exceeds the impedance deviation rate threshold ε n, indicating that an external direct discharge fault occurred, because: an external direct discharge fault will cause multiple capacitor units to short-circuit at the same time, and it is a low-resistance fault. An internal fault only exists in a single capacitor unit and will not cause a large impedance change. A bird damage fault will cause multiple capacitor units to short-circuit like an external direct discharge fault, but a bird damage fault is a high-resistance fault, and the impedance change caused is larger than that of an internal fault, but smaller than that of an external direct discharge fault. This makes the impedance change caused by an external direct discharge fault larger than that of both an internal fault and a bird damage fault; if the impedance deviation rate of each phase None of them exceeds the impedance deviation rate threshold ε n , indicating that a bird damage fault or an internal fault has occurred, and the following methods need to be used to determine whether it is a bird damage fault;

[0051] The unbalanced current I ua ,I ub ,I uc With the external fault current threshold I external By comparison, if the phase unbalanced current I ua ,I ub ,I uc The external fault current threshold I external , it means that the converter station filter capacitor tower has an internal fault. If the unbalanced current I ua ,I ub ,I uc The unbalanced current in any phase exceeds the external fault current threshold I external , it means that a bird damage fault has occurred, because: internal fault is just a breakdown of individual components in a single capacitor unit, causing a small unbalanced current, while bird damage can cause multiple capacitor units to short-circuit, causing a larger unbalanced current than an internal fault. internal It is obtained by the following formula:

[0052] I internal =K Ⅰ I f1

[0053] Where: I internal : Internal fault current threshold / A, K Ⅰ : Small fixed value reliability coefficient, I f1 : Inherent unbalanced current during normal operation / A.

[0054] The external fault current threshold I external It is obtained by the following formula:

[0055] I external =K Ⅱ I f2

[0056] Where: I external : External fault current threshold / A, K Ⅱ : Large fixed value reliability coefficient, I f2 : Unbalanced current during external high resistance fault / A.

[0057] The measured impedance of the three phases a, b, and c It is obtained by the following formula:

[0058]

[0059] Where: a, b, c three-phase, Phase measurement impedance / Ω, Phase voltage / V, V n : Neutral point voltage / V, Phase current / A.

[0060] The impedance deviation rate of each phase It is obtained by the following formula:

[0061]

[0062] Where: a, b, c three-phase, Phase impedance deviation rate, Phase measurement impedance / Ω, Z ideal : Standard impedance of each phase / Ω.

[0063]

[0064] Where: a, b, c three-phase, Z ideal :Each phase measured impedance / Ω, Normal operation without faults Phase voltage / V, V n ': Neutral point voltage during normal operation without faults / V, Normal operation without faults Phase current / A.

[0065] In this embodiment, the impedance deviation rate threshold ε n Determined based on the maximum impedance deviation rate that can be caused by external bird damage.

[0066] The following specific experimental examples are used to further illustrate the technical solutions and technical effects of the present invention. It should be noted that the following experimental examples are only for further explaining the present invention and do not limit the technical solutions of the present invention.

[0067] Please see Figure 2 This embodiment provides a method for distinguishing bird damage faults in a converter station filter capacitor tower, and provides a simulation model of a filter capacitor tower. In the entire model, a three-phase AC power supply is used as the power supply, the power supply is grounded through a 1Ω resistor, and the outgoing line end is connected to the capacitor through a 1Ω resistor and a 1H inductor in parallel, and the voltage level of the power supply is 230kV; the capacitance value of a single capacitor element is 13.33uF, and the capacity of a capacitor group is 23.994uF; the resistance value in the tuner is 1200Ω, and the inductance value is 0.0106H.

[0068] S10. In this embodiment, the fault occurs in the first capacitor bank outside phase A. Figure 2 At Ca1, the fault resistance is 300Ω. According to the electrical quantity measurement points of the filter capacitor tower in the actual project, the three-phase voltages V of the filter capacitor tower a, b, and c are obtained. a 、V b 、V c , Neutral point voltage V n , a, b, c three-phase current I a ,I b ,I c And the unbalanced current I of phases a, b, and c ua ,I ub ,I uc . Figure 3 The three-phase currents I of a, b, and c are listed in a ,I b ,I c and the unbalanced current I of phases a, b, and c ua ,I ub ,I uc .

[0069] S20. The present invention can improve the traditional unbalance protection, specifically by changing the traditional current threshold to the internal fault threshold I internal , the internal fault threshold I internal The setting value is small and is set according to the inherent unbalanced current during normal operation, which can reflect any minor faults of the capacitor tower. The setting formula is:

[0070] I internal =K Ⅰ I f1

[0071] Where: I internal : Internal fault current threshold / A, K Ⅰ: Small fixed value reliability coefficient, I f1 : Inherent unbalanced current during normal operation / A.

[0072] According to the data in this embodiment, the internal fault current threshold I internal It is 0.07252kA.

[0073] S30. The present invention also adds a new current threshold, which is the external fault threshold I external , the external fault threshold I external The setting value is relatively large, and is mainly used to distinguish between internal and external faults of capacitor towers. It is set according to the minimum current when an external fault occurs, which is generally an external high-resistance fault. The setting formula is:

[0074] I external =K Ⅱ I f2

[0075] Where: I external : External fault current threshold / A, K Ⅱ : Large fixed value reliability coefficient, I f2 : Unbalanced current during external high resistance fault / A.

[0076] According to the data of this embodiment, the external fault current threshold I external It is 0.58kA.

[0077] S40. In addition to improving the existing unbalanced protection method, the present invention introduces a new impedance protection method, according to the measured a, b, c three-phase voltage V a 、V b 、V c , a, b, c three-phase current I a ,I b ,I c The measured impedance of phases a, b, and c is calculated using the following formula:

[0078]

[0079] Where: a, b, c three-phase, Phase measurement impedance / Ω, Phase voltage / V, V n : Neutral point voltage / V, Phase current / A;

[0080] And calculate the standard impedance Z of each phase ideal , the calculation formula is:

[0081]

[0082] Where: a, b, c three-phase, Z ideal :Each phase measured impedance / Ω, Normal operation without faults Phase voltage / V, V n ': Neutral point voltage during normal operation without faults / V, Normal operation without faults Phase current / A.

[0083] S50. Based on the calculated impedance of each phase Standard impedance of each phase Z ideal Calculate the corresponding impedance deviation rate of each phase The calculation formula is as follows:

[0084]

[0085] Where: a, b, c three-phase, Phase impedance deviation rate, Phase measurement impedance / Ω, Z ideal : Standard impedance of each phase / Ω.

[0086] The impedance deviation rate threshold ε n The impedance deviation rate threshold ε is determined according to the maximum impedance deviation rate that can be caused by bird damage to the outside. n is 2%.

[0087] like Figure 1 The process protection steps shown are as follows:

[0088] S60. First compare the unbalanced current I of each phase ua ,I ub ,I uc and the internal fault current threshold I internal , if the unbalanced current I ua ,I ub ,I uc If the unbalanced current I ua ,I ub ,I uc The unbalanced current of any phase exceeds the internal fault current threshold I internal , then proceed to step S70. In this embodiment, according to the simulation data, it can be known that the unbalanced current I of phase aua It is 1.2 kA, which exceeds the internal fault current threshold, so step S70 is performed.

[0089] S70. The impedance deviation rate of each phase The impedance deviation rate threshold ε n For comparison, if the impedance deviation rate of each phase The impedance deviation rate of any phase exceeds the impedance deviation rate threshold ε n , it indicates that the fault is an external direct discharge fault. None of them exceeds the impedance deviation rate threshold ε n , it indicates that the fault is a bird damage fault or an internal fault, and step S80 is executed. In this embodiment, the impedance deviation rate ε of phase a is calculated based on the prevention data. a The impedance deviation rate of other phases is 0%, and the impedance deviation rate does not exceed the impedance deviation rate threshold ε n , it may be a bird damage failure or an internal failure, and continue to step S80.

[0090] S80, comparing the unbalanced current of each phase with the external fault current threshold I external By comparison, if the unbalanced current of each phase does not exceed the external fault current threshold I external , it indicates that an internal fault has occurred. If the unbalanced current of each phase exceeds the external fault current threshold I external , it means that the fault is bird damage fault. Internal fault is just a breakdown of individual components in a single capacitor unit, causing a small unbalanced current. Bird damage will cause multiple capacitor units to short-circuit, causing a larger unbalanced current than internal fault. In this embodiment, according to the simulation data, it can be known that the unbalanced current I ua It is 1.2kA, which exceeds the external fault current threshold of 0.58kA.

[0091] According to the exceeding of three protection thresholds, such as Figure 4 As shown, the unbalanced current I ua Exceeding two current thresholds I internal and I external , impedance deviation rate of phase a ε a Does not exceed the threshold ε n Therefore, it can be determined that the fault is a bird damage fault. The troubleshooting personnel can determine the type of fault that has occurred in the first time and perform repairs according to different fault types, thereby improving maintenance efficiency and avoiding maintenance delays.

[0092] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A method for distinguishing bird damage to a converter station filter capacitor tower, characterized in that: The following steps are involved: S10. Obtain the three-phase voltage V of the filter capacitor tower to be identified, a, b, c a 、V b 、V c , Neutral point voltage V n , a, b, c three-phase current I a ,I b ,I c And the unbalanced current I of phases a, b, and c ua ,I ub ,I uc ; S20. Calculate the internal fault current threshold I of the filter capacitor tower to be identified internal ; S30. Calculate the external fault current threshold I of the filter capacitor tower to be identified external , the external fault current threshold I external is greater than the internal fault current threshold I internal ; S40. According to the three-phase voltages a, b, and c a 、V b 、V c And the three-phase currents a, b, c I a ,I b ,I c Calculate the measured impedance of each phase of phase a, b, and c And obtain the standard impedance Z of each phase a, b, and c ideal ; S50. According to the measured impedance of each phase of a, b, c The standard impedance Z of each phase of the corresponding a, b, and c phases ideal Calculate the corresponding impedance deviation rate of each phase And obtain the impedance deviation rate threshold ε n ; S60. The unbalanced current I of each phase ua ,I ub ,I uc With the internal fault current threshold I internal By comparison, if the unbalanced current I ua ,I ub ,I uc The internal fault current threshold I internal , it means that no fault has occurred. If the unbalanced current I ua ,I ub ,I uc The unbalanced current of any phase exceeds the internal fault current threshold I internal , then execute step S70; S70. The impedance deviation rate of each phase The impedance deviation rate threshold ε n For comparison, if the impedance deviation rate of each phase The impedance deviation rate of any phase exceeds the impedance deviation rate threshold ε n , it means that the fault is an external direct discharge fault. If the impedance deviation rate of each phase is None of them exceeds the impedance deviation rate threshold ε n , it indicates that the fault is a bird damage fault or an internal fault, and step S80 is executed; S80. Compare the unbalanced current of each phase with the external fault current threshold I external If the unbalanced current of each phase does not exceed the external fault current threshold I external , it indicates that an internal fault has occurred. If the unbalanced current of each phase exceeds the external fault current threshold I external , it means that the fault is a bird damage fault.

2. The method for distinguishing bird damage to the converter station filter capacitor tower according to claim 1 is characterized in that: The internal fault current threshold I internal It is obtained by the following formula: I internal =K Ⅰ ·I f1 Where: I internal : Internal fault current threshold / A, K Ⅰ : Small fixed value reliability coefficient, I f1 : Inherent unbalanced current during normal operation / A.

3. The method for distinguishing bird damage to a converter station filter capacitor tower according to claim 1, characterized in that: The external fault current threshold I external It is obtained by the following formula: I external =K Ⅱ ·I f2 Where: I external : External fault current threshold / A, K Ⅱ : Large fixed value reliability coefficient, I f2 : Unbalanced current during external high resistance fault / A.

4. The method for distinguishing bird damage to a converter station filter capacitor tower according to claim 1, characterized in that: The measured impedance of the three phases a, b, and c It is obtained by the following formula: Where: Three-phase, Phase measurement impedance / Ω, Phase voltage / V, V n : Neutral point voltage / V, Phase current / A.

5. The method for distinguishing bird damage to the converter station filter capacitor tower according to claim 4 is characterized in that: The impedance deviation rate of each phase It is obtained by the following formula: Where: Three-phase, Phase impedance deviation rate, Phase measurement impedance / Ω, Z ideal : Standard impedance of each phase / Ω.

6. The method for distinguishing bird damage to a converter station filter capacitor tower according to claim 5, characterized in that: The impedance deviation rate threshold ε n Determined based on the maximum impedance deviation rate that can be caused by external bird damage.

7. The method for distinguishing bird damage to a converter station filter capacitor tower according to claim 1, characterized in that: The standard impedance Z ideal It is obtained by the following formula: Where: Three-phase, Z ideal :Each phase measured impedance / Ω, Normal operation without faults Phase voltage / V, V n ': Neutral point voltage during normal operation without faults / V, Normal operation without faults Phase current / A.

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