Large-scale hydro-generator terminal circuit breaker failure fault discrimination method based on Pearson similarity

Abstract

The invention provides a Pearson similarity-based large-scale hydro-generator end circuit breaker failure fault discrimination method, and the method comprises the steps: tripping an end circuit breaker according to the related protection requirements when a hydro-generator has an internal fault or an abnormal operation condition, and starting GCB failure protection at the same time, if a memory current effective value is higher than a given threshold value, starting the GCB failure protection; if yes, it is judged that a certain load exists in the system, and whether a GCB failure fault exists or not is judged through the Pearson correlation coefficients of fundamental voltage waveforms on the two sides of the GCB; if the memory current effective value is lower than a given threshold value, it is judged that the system is in a light load condition, and whether GCB failure faults exist or not is judged through Pearson correlation coefficients of third harmonic voltage waveforms on the two sides of the GCB. According to the method, reference can be provided for GCB failure protection of the large hydro-generator, the conditions of various GCB failure faults can be correctly reflected, the faults are removed within the minimum range, and the situation that the accident range is expanded due to remote backup protection actions is avoided.

Description

Technical Field

[0001] The invention belongs to the field of large-scale hydro-generator protection, and more specifically, relates to a GCB failure fault identification method for a large-scale hydro-generator. Background Art

[0002] Promoting the green and low-carbon transformation of the energy and power industry has become an important trend in global development. Building a new power system that can achieve a high proportion of new energy supply and consumption is an important part of my country's construction of a new energy system and a key measure to help achieve the "dual carbon" goal. At present, the large-scale application of energy storage still faces many constraints. Giving full play to the complementary characteristics of various power sources to achieve multi-energy complementarity is an important way to promote the consumption of new energy at this stage. Hydropower stations can provide large-scale clean energy, reduce dependence on fossil fuels, and reduce carbon emissions and air pollution.

[0003] Large hydroelectric generators are equipped with machine-side circuit breakers installed at the generator end. By closing them, the switching of the generator can be easily controlled without affecting the operation of other equipment, making the operation mode of the generator more flexible. The failure of the GCB in normal operation to trip and close due to its own mechanical or electrical defects is called GCB failure. When the generator is in an internal fault or abnormal working condition, it is necessary to trip the GCB to achieve isolation from the system. For large generators, when differential protection, stator grounding protection, overload protection and other protection actions are performed, it is necessary to trip the GCB and disconnect the system. However, in long-term operation, the power supply of the tripping coil may be lost or disconnected due to vibration, and the tripping coil cannot send a tripping command to the GCB, resulting in the three-phase refusal of the GCB; in addition, the switching of the GCB is controlled by a mechanical connecting rod. At present, there have been GCB non-full-phase accidents caused by connecting rod breakage. When the GCB fails, it is necessary to act on other circuit breakers associated with the GCB through the GCB failure protection to ensure that the generator and the system can be effectively isolated under fault conditions to avoid damage to the generator.

[0004] The existing GCB failure protection adopts the form of current judgment, and the grid line circuit breaker failure protection adopts negative sequence current and zero sequence current judgment. Since the zero sequence current at the end of the large hydro-turbine generator cannot flow, the GCB failure protection adopts phase current and negative sequence current judgment. However, in the case of GCB single-phase refusal to operate, since the equivalent zero sequence impedance of the main transformer delta winding is infinite, the phase current and negative sequence current are both zero at this time, and the protection cannot respond to this situation, which will cause a phase to still be connected to the system during the fault maintenance process, posing a great threat to the personal safety of the maintenance personnel, and is a major safety hazard. In the event of a negative sequence overload fault, if the negative sequence current does not reach the action value of the negative sequence judgment criterion of the GCB failure protection, if the three-phase GCB refuses to operate at this time, the fault cannot be removed, and the large hydro-turbine generator will be in a negative sequence overload state for a long time, which will damage the rotor core. In addition, due to the particularity of electrical quantities and the diversity of machine cutting methods under the GCB failure fault of large hydro-turbine generators, the existing GCB failure protection has the risk of refusal to operate under various fault conditions, so the problem of reasonably configured GCB failure protection needs to be solved urgently.

[0005] In summary, for large hydro-turbine generators, the existing GCB failure protection based on phase current and negative sequence current criteria cannot correctly reflect the GCB failure refusal to operate, and does not meet the operation requirements of large hydro-turbine generators. It is necessary to propose a new principle that can reflect various GCB refusal to operate failure fault types. Summary of the invention

[0006] In view of the above defects or improvement needs of the prior art, the present invention provides a method for distinguishing failure of a large hydro-turbine generator terminal circuit breaker based on Pearson similarity. Its purpose is to provide a reasonable and effective criterion for the correct response of the GCB failure protection of a large hydro-turbine generator unit to the refusal to operate, identify different GCB failure faults, and trip as soon as possible by acting on other circuit breakers associated with it and connected to the power supply locally, so as to avoid the remote backup protection of the adjacent substation from cutting off the remote circuit breaker and expanding the scope of the accident.

[0007] In order to realize the above technical features, the object of the present invention is achieved as follows: a method for distinguishing failure of a large hydro-generator end circuit breaker based on Pearson similarity comprises the following steps: S1. Monitor the action of the corresponding protection for internal faults and abnormal conditions of the generator, and determine whether the GCB failure protection is activated; if so, execute step S2; if not, continue to detect; S2. After the GCB failure protection is activated, determine whether the system has a certain load by using the current memory criterion; if so, execute step S3; if not, execute step S4; S3. Construct the Pearson correlation coefficient criterion of the fundamental voltage waveform, detect and sample the fundamental voltage waveforms on both sides of the GCB, calculate the Pearson correlation coefficient of the fundamental voltage waveforms on both sides of the GCB, and determine whether the Pearson correlation coefficient criterion of the fundamental voltage waveforms on both sides of the GCB is satisfied; if so, execute step S5; if not, continue to detect; S4. Construct the Pearson correlation coefficient criterion of the third harmonic voltage waveform, detect and sample the third harmonic voltage waveform on both sides of the GCB, calculate the Pearson correlation coefficient of the third harmonic voltage waveform on both sides of the GCB, and determine whether the Pearson correlation coefficient criterion of the third harmonic voltage waveform on both sides of the GCB is satisfied; if so, execute step S5; if not, continue to detect; S5. A large hydro-turbine generator has a GCB failure. After a delay of time period I, the GCB failure protection output is triggered, and the local circuit breaker is re-tripped. After a delay of time period II, the GCB failure protection output is triggered, and the side switch, middle switch, demagnetization, shutdown, trip to the low-voltage side of the transformer, and lock the electrical brake.

[0008] Preferably, the protections mainly involved in monitoring the action of corresponding protections for internal faults and abnormal operating conditions of the generator in step S1 include: differential protection, phase-split differential protection, generator turn-to-turn protection, generator phase-to-phase backup protection, stator grounding protection and negative-sequence overload protection, and the exit mode includes the protection type of starting GCB failure protection; when the above protection is activated due to internal faults and abnormal operating conditions of the generator, the machine-end circuit breaker trips and the GCB failure protection is started.

[0009] Preferably, the memory flow criterion for determining the system load size described in step S2 is specifically: ; Where, memory current | I memory | is the amplitude of the current phasor at the machine end before the fault; I memory.set The memory current criterion protection setting value needs to be set according to the actual load current size on site; determine whether the memory current meets the memory current criterion. If so, it means that the system has a certain load; if not, it means that the system is in a light load condition.

[0010] Preferably, the criterion for constructing the fundamental voltage waveform Pearson correlation coefficient in step S3 is specifically: ; ; In the formula, P ( U φf1 , U φx1 )forU φf1 and U φx1 Pearson correlation coefficient between them; U φf1 is the fundamental voltage on the GCB generator side, where φ =A,B,C; U φx1 is the fundamental voltage on the GCB system side; ∆ e The protection margin based on the Pearson correlation coefficient of the fundamental voltage waveform needs to be determined based on the Pearson correlation coefficient of the fundamental voltage waveform on both sides of the GCB actually operating on site.

[0011] Preferably, the Pearson correlation coefficient criterion for constructing the third harmonic voltage waveform in step S4 is specifically: ; ; In the formula, P ( U φf3 , U φx3 )for U φf3 and U φx3 Pearson correlation coefficient between them; U φf3 is the third harmonic voltage on the GCB generator side, where φ =A,B,C; U φx3 is the third harmonic voltage on the GCB system side; ∆ e The protection margin based on the Pearson correlation coefficient of the third harmonic voltage waveform needs to be determined based on the Pearson correlation coefficient of the third harmonic voltage waveform on both sides of the GCB actually operating on site.

[0012] The present invention has the following beneficial effects: The present invention starts from the protection selective action requirements of large hydro-turbine generators, combines the GCB failure fault voltage characteristics of large hydro-turbine generators, and proposes a large hydro-turbine generator end circuit breaker failure fault discrimination method based on Pearson similarity. After the GCB failure protection is started, the load size of the system is judged by the current memory current criterion. When the system has a certain load, the fundamental voltage waveform Pearson correlation coefficient criterion is constructed. There is a certain phasor difference between the fundamental voltages on both sides of the GCB of the correct action phase, and the phasor difference between the fundamental voltages on both sides of the GCB of the refusal phase is zero. The fundamental voltage waveform Pearson correlation coefficient criterion can correctly judge whether the GCB has a failure fault and identify the fault phase. When the system is in a light load state, the fundamental voltage waveform Pearson correlation coefficient criterion can reflect the GCB failure fault, but it is easy to malfunction, so it needs to be locked under light load conditions. When the system is lightly loaded, the third harmonic voltage waveform Pearson correlation coefficient criterion is constructed. By calculating the Pearson correlation coefficient of the third harmonic voltage waveform on both sides of the GCB, and then judging whether its Pearson correlation coefficient meets the Pearson correlation coefficient criterion of the third harmonic voltage waveform, it is possible to correctly judge whether the GCB has a failure fault and identify the fault phase. If so, there is a GCB failure fault, and the corresponding phase where the third harmonic voltage waveform Pearson satisfies the Pearson correlation coefficient criterion of the third harmonic voltage waveform has a GCB failure fault; if not, there is no GCB failure fault. The large-scale hydro-turbine generator end circuit breaker failure fault identification method based on Pearson similarity can correctly reflect different GCB refusal situations, provide an effective reference for the GCB failure protection improvement method of large-scale hydro-turbine generator units, ensure the safe operation of large-scale hydro-turbine generator units, and provide a technical reference for the GCB failure protection improvement method of other generators. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0014] Figure 1 The present invention provides a flow chart of a method for distinguishing a failure of a large hydro-turbine generator end circuit breaker based on Pearson similarity.

[0015] Figure 2 The present invention provides a logic diagram of a method for distinguishing a failure of a large hydro-turbine generator end circuit breaker based on Pearson similarity.

[0016] Figure 3 It is a fault simulation model of a large hydro-generator end circuit breaker failure used in the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0018] The embodiment of the present invention provides a method for distinguishing failure of a large hydro-turbine generator terminal circuit breaker based on Pearson similarity, and the process is as follows: Figure 1 As shown in the figure, the protection judgment logic action diagram is as follows Figure 2 As shown, the following steps are included: S1. Monitor the action of the corresponding protection for internal faults and abnormal conditions of the generator, and determine whether the GCB failure protection is activated; if so, execute step S2; if not, continue to detect.

[0019] Specifically, when the generator has an internal fault and abnormal operating conditions, the corresponding protection output is activated, the machine-side circuit breaker GCB is tripped and the GCB failure fault is activated. The output mode includes tripping the machine-side circuit breaker GCB and activating the GCB failure protection. The main protections involved include: differential protection, split-phase differential protection, generator turn-to-turn protection (differential), generator phase-to-phase backup protection, stator grounding protection, negative sequence overload protection, etc. When the above protection is activated due to internal faults and abnormal operating conditions of the generator, the machine-side circuit breaker is tripped and the GCB failure protection is activated. Otherwise, the GCB failure protection is not activated.

[0020] S2. After the GCB failure protection is activated, the system is judged whether there is a certain load by using the current criterion of the memorized current. If yes, step S3 is executed; if not, step S4 is executed.

[0021] Specifically, when the generator has an internal fault or abnormal operating condition and the GCB failure protection is activated, the memory current is defined as the current of the generator before the fault. If the memory current is large, it means that the system has a certain load before the GCB is removed. At this time, the fundamental voltage waveform Pearson correlation coefficient criterion should be used; if the memory current is small, it means that the system is in a light load state before the GCB is removed. At this time, the third harmonic voltage waveform Pearson correlation coefficient criterion should be used and the fundamental voltage waveform Pearson correlation coefficient criterion should be locked. The constructed memory current criterion is ; In the formula, | I memory | is the effective value of the memory current phasor; I memory.set In order to memorize the current criterion setting value, it is necessary to adjust it according to the actual load current size on site.

[0022] S3. Construct the Pearson correlation coefficient criterion of the fundamental voltage waveform, detect and sample the fundamental voltage waveforms on both sides of the GCB, calculate the Pearson correlation coefficient of the fundamental voltage waveforms on both sides of the GCB, and determine whether the Pearson correlation coefficient criterion of the fundamental voltage waveforms on both sides of the GCB is satisfied. If yes, execute step S5; if no, continue to detect.

[0023] Specifically, when a GCB failure occurs, as long as the system carries a certain load, the Pearson correlation coefficient value of the fundamental voltage waveform on both sides of the GCB can effectively reflect the GCB failure. For the correct action phase, there is a certain fundamental voltage difference on both sides of the GCB, which causes the fundamental voltage waveforms on both sides of the GCB to be dissimilar. At this time, the Pearson correlation coefficient value of the fundamental voltage waveforms on both sides of the GCB of the correct action phase is not close to 1; while for the refusal phase, the fundamental voltage difference on both sides of the GCB is always 0, so the fundamental voltage waveforms on both sides of the GCB are the same. At this time, the Pearson correlation coefficient value of the fundamental voltage waveforms on both sides of the refusal phase is infinitely close to or even equal to 1. Based on this, the Pearson correlation coefficient criterion based on the fundamental voltage waveforms on both sides of the GCB can be constructed as follows: ; ; In the formula, P ( U φf1 , U φx1 )for U φf1 and U φx1 Pearson correlation coefficient between them; U φf1 is the fundamental voltage on the GCB generator side, where φ =A,B,C; U φx1 is the fundamental voltage on the GCB system side; ∆ e The protection margin based on the Pearson correlation coefficient of the fundamental voltage waveform needs to be determined based on the Pearson correlation coefficient of the fundamental voltage waveform on both sides of the GCB actually operating on site.

[0024] When the GCB failure protection is activated, if the Pearson correlation coefficient value of the fundamental voltage waveform on both sides of a phase GCB meets the Pearson correlation coefficient criterion of the fundamental voltage waveform, it means that the phase has a GCB failure. This protection criterion can effectively identify various possible failures of the GCB and can give a specific failure phase, but it is easy to malfunction when the generator is lightly loaded, and the specific failure phase cannot be correctly identified, so the criterion needs to be locked under light load conditions.

[0025] S4. Construct the Pearson correlation coefficient criterion of the third harmonic voltage waveform, detect and sample the third harmonic voltage waveform on both sides of the GCB, calculate the Pearson correlation coefficient of the third harmonic voltage waveform on both sides of the GCB, and determine whether the Pearson correlation coefficient criterion of the third harmonic voltage waveform on both sides of the GCB is satisfied. If yes, execute step S5; if not, continue to detect.

[0026] Specifically, due to the structural characteristics of the generator rotor winding, there is always a certain third harmonic magnetic potential and magnetic density. On the other hand, the different structures of the rotor large teeth and small teeth make the equivalent air gap lines of the two different, which will also produce third harmonic magnetic density. In this way, there is a third harmonic component in the generator phase voltage. Since the third harmonic voltage has a zero-sequence property, there is usually no third harmonic component in the system side voltage. Therefore, as long as the three-phase GCB is normally opened, there will be a third harmonic voltage phasor difference on both sides of the GCB. Even if there is a third harmonic voltage on the system side, as long as the harmonic voltage is out of phase with the third harmonic voltage on the generator side, there will still be a third harmonic voltage. The phase difference of the subharmonic voltage causes the third harmonic voltage waveforms on both sides of the GCB to be dissimilar. Therefore, as long as the three-phase GCB is tripped normally, there will be differences in the third harmonic voltage waveforms on both sides of the GCB, and the Pearson correlation coefficient will not be close to 1. When a GCB failure occurs, since the low-voltage side of the main transformer is connected in a triangle, there are third harmonic voltages on both sides of the GCB of each phase. At this time, the third harmonic voltage difference is close to 0, so the fundamental voltage waveforms on both sides of the GCB are the same. Therefore, the Pearson correlation coefficient value of the third harmonic voltage waveform on both sides of the GCB of the rejected phase is infinitely close to or even equal to 1. Based on this, the Pearson correlation coefficient criterion for the third harmonic voltage waveform is constructed as follows: ; ; In the formula, P ( U φf3 , U φx3 )for U φf3 and U φx3 Pearson correlation coefficient between them; U φf3 is the third harmonic voltage on the GCB generator side, where φ =A,B,C; U φx3 is the third harmonic voltage on the GCB system side; ∆ e The protection margin based on the Pearson correlation coefficient of the third harmonic voltage waveform needs to be determined based on the Pearson correlation coefficient of the third harmonic voltage waveform on both sides of the GCB actually operating on site.

[0027] When the GCB failure protection is activated, if the Pearson correlation coefficient value of the third harmonic voltage waveform on both sides of the GCB of a phase meets the Pearson correlation coefficient criterion of the third harmonic voltage waveform, it means that the GCB failure fault occurs in this phase. This protection criterion can effectively identify various possible failure faults of GCB and can give the specific failure fault phase, but it is easy to malfunction when the generator is fully loaded, and the specific failure fault phase cannot be correctly identified, so the criterion needs to be locked under full load.

[0028] S5. After the delay of period I, the GCB protection output fails and the local circuit breaker is re-tripped; after the delay of period II, the GCB protection output fails and the GIS (side switch, middle switch) is tripped, the magnetism is demagnetized, the machine is shut down, the low-voltage side of the plant transformer is tripped, and the electrical brake is locked.

[0029] Specifically, when the criteria in S3 and S4 are activated, it indicates that a GCB failure has occurred in the system. According to the circuit breaker failure protection guideline for large hydro-turbine generator units, it is necessary to trip other circuit breakers that are locally associated with it and connected to the power supply as soon as possible to cut off the fault within the smallest scope, so as to avoid the remote backup protection of the adjacent substation from cutting off the remote circuit breaker and expanding the scope of the accident.

[0030] The embodiment of the present invention builds a generator-transformer-load simulation model based on a large hydro-turbine generator in the PSCAD / EMTDC software platform. The large hydro-turbine generator adopts an 8-branch winding structure, each winding adopts a distributed equivalent circuit, each branch winding has 8 pole-phase groups, each pole-phase group has 4 turns of coils, the rated capacity of the generator is 944.5MVA, the rated voltage is 22kV, and the rated current is 24787A; the three-phase GCB is split-phase opening and closing; the transformer T adopts a wiring method with a ratio of 22 / 550kV; the load S is equivalent to an infinite system; the current transformer CT ratio is 30000 / 1A, and the voltage transformer PTI and PT2 ratios are both 22 / 0.1kV; the GCB failure protection I stage action time limit is 0.1s, and the II stage action time limit is 0.3s; the protection margin ∆ e are all set to 0.001, and the simulation model is as follows Figure 3 shown.

[0031] Based on PSCAD / EMTDC software, a quasi-distributed parameter model of the generator is established for simulation verification. Assuming that the generator has a single-phase metallic ground fault in the stator under full load, and the GCB failure protection is activated, the fault phase is set to phase A, and the Pearson correlation coefficient of the fundamental voltage waveform on both sides of each phase GCB is calculated under the conditions of normal GCB operation, single-phase refusal, two-phase refusal, and three-phase refusal, as shown in Table 1.

[0032] Table 1 Pearson correlation coefficient values ​​of each phase under various GCB tripping conditions under single-phase stator grounding fault conditions

[0033] Assuming that the system is under light load, the generator has a single-phase metallic grounding fault in the stator, and the GCB failure protection is activated. The fault phase is set to phase A. The Pearson correlation coefficients of the fundamental voltage waveforms on both sides of the GCB of each phase are calculated under the conditions of normal GCB operation, single-phase refusal to operate, two-phase refusal to operate, and three-phase refusal to operate, as shown in Table 2; the Pearson correlation coefficients of the third harmonic voltage waveforms on both sides of the GCB of each phase are calculated, as shown in Table 3.

[0034] Table 2 Pearson correlation coefficient values ​​of each phase under various GCB tripping conditions under stator single-phase grounding fault conditions

[0035] Table 3 Pearson correlation coefficient values ​​of each phase under various GCB tripping conditions under single-phase stator grounding fault conditions

[0036] The simulation results in Table 1-3 show that: when the system has a certain load, the fundamental voltage waveform Pearson correlation coefficient criterion can correctly reflect the GCB failure fault and give the fault phase; when the system is lightly loaded, the fundamental voltage waveform Pearson correlation coefficient criterion can reflect the GCB failure fault, but it is easy to malfunction, so it needs to be locked under light load conditions; when the system is lightly loaded, the third harmonic voltage waveform Pearson correlation coefficient criterion can correctly reflect the GCB failure fault and give the fault phase. The large hydro-turbine generator end circuit breaker failure fault identification method based on Pearson similarity can effectively reflect the GCB failure fault and provide a reference for the GCB failure protection criterion configuration method of large hydro-turbine generators.

Claims

1. A method for distinguishing failure of a large hydro-generator end circuit breaker based on Pearson similarity, characterized in that: The following steps are involved: S1. Monitor the action of the corresponding protection for internal faults and abnormal conditions of the generator, and determine whether the GCB failure protection is activated; if so, execute step S2; if not, continue to detect; S2. After the GCB failure protection is activated, determine whether the system has a certain load by using the current memory criterion; if so, execute step S3; if not, execute step S4; S3. Construct the Pearson correlation coefficient criterion of the fundamental voltage waveform, detect and sample the fundamental voltage waveforms on both sides of the GCB, calculate the Pearson correlation coefficient of the fundamental voltage waveforms on both sides of the GCB, and determine whether the Pearson correlation coefficient criterion of the fundamental voltage waveforms on both sides of the GCB is satisfied; if so, execute step S5; if not, continue to detect; S4. Construct the Pearson correlation coefficient criterion of the third harmonic voltage waveform, detect and sample the third harmonic voltage waveform on both sides of the GCB, calculate the Pearson correlation coefficient of the third harmonic voltage waveform on both sides of the GCB, and determine whether the Pearson correlation coefficient criterion of the third harmonic voltage waveform on both sides of the GCB is satisfied; if so, execute step S5; if not, continue to detect; S5. A large hydro-turbine generator has a GCB failure. After a delay of time period I, the GCB failure protection output is triggered, and the local circuit breaker is re-tripped. After a delay of time period II, the GCB failure protection output is triggered, and the side switch, middle switch, demagnetization, shutdown, trip to the low-voltage side of the transformer, and lock the electrical brake.

2. According to the method for distinguishing failure of a large hydro-turbine generator end circuit breaker based on Pearson similarity in claim 1, it is characterized in that: The protections mainly involved in monitoring the action of the corresponding protections for the internal faults and abnormal operating conditions of the generator in step S1 include: differential protection, phase-split differential protection, generator turn-to-turn protection, generator phase-to-phase backup protection, stator grounding protection and negative-sequence overload protection. The exit mode includes the protection type of starting the GCB failure protection. When the above protections are activated due to the internal faults and abnormal operating conditions of the generator, the machine-end circuit breaker trips and the GCB failure protection is started.

3. According to the method for distinguishing failure of a large hydro-turbine generator end circuit breaker based on Pearson similarity in claim 1, it is characterized in that: The memory flow criterion for determining the system load size described in step S2 is specifically: ； Where, memory current | I memory | is the amplitude of the current phasor at the machine end before the fault; I memory.set The memory current criterion protection setting value needs to be set according to the actual load current size on site; determine whether the memory current meets the memory current criterion. If so, it means that the system has a certain load; if not, it means that the system is in a light load condition.

4. According to the method for distinguishing failure of a large hydro-generator end circuit breaker based on Pearson similarity in claim 1, it is characterized in that: The criterion for constructing the Pearson correlation coefficient of the fundamental voltage waveform in step S3 is specifically: ； ； In the formula, P ( U φf1 , U φx1 )for U φf1 and U φx1 Pearson correlation coefficient between them; U φf1 is the fundamental voltage on the GCB generator side, where φ =A,B,C; U φx1 is the fundamental voltage on the GCB system side; ∆ e The protection margin based on the Pearson correlation coefficient of the fundamental voltage waveform needs to be determined based on the Pearson correlation coefficient of the fundamental voltage waveform on both sides of the GCB actually operating on site.

5. According to the method for distinguishing failure of a large hydro-generator end circuit breaker based on Pearson similarity as claimed in claim 1, it is characterized in that: The Pearson correlation coefficient criterion for constructing the third harmonic voltage waveform in step S4 is specifically: ； ； In the formula, P ( U φf3 , U φx3 )for U φf3 and U φx3 Pearson correlation coefficient between them; U φf3 is the third harmonic voltage on the GCB generator side, where φ =A,B,C; U φx3 is the third harmonic voltage on the GCB system side; ∆ e The protection margin based on the Pearson correlation coefficient of the third harmonic voltage waveform needs to be determined based on the Pearson correlation coefficient of the third harmonic voltage waveform on both sides of the GCB actually operating on site.

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