CT polarity verification method of auxiliary power supply system

Abstract

The invention provides a CT polarity verification method of an auxiliary power supply system. Under the condition that the circulating current is formed, the same current flows through the pair of auxiliary transformers and the bus tie switch, so that the CT polar relation between the branches where the two auxiliary transformers forming the circulating current are located and the branch where the bus tie switch is located is detected, and if the circulating current is formed successively, the current is detected to be the same as that of the bus tie switch. If yes, the CT polar relation between the branch where each auxiliary transformer is located and the branch where the bus tie switch is located is detected, and then the CT polar relation between the branches where the auxiliary transformers are located can be obtained with the bus tie switch as the reference; the circulation is formed under the condition that the auxiliary power supply system is in a normal operation state, and the formed circulation does not stop any auxiliary transformer, so that all the auxiliary transformers are not stopped in the detection process of the CT polar relation, and the detection accuracy of the CT polar relation is improved under the condition that all the auxiliary transformers are not stopped. The verification of the CT polarity of the branch where each auxiliary transformer is located is realized.

Description

Technical Field

[0001] The invention relates to the technical field of power equipment maintenance and power meter testing, and in particular to a CT polarity verification method for an auxiliary power supply system. Background Art

[0002] Bus differential protection is the main protection for busbar protection. Due to its importance, the bus differential protection will not be put into operation until the polarity of the CT (current transformer) of each branch connected to the bus differential protection is verified to be correct. Usually, the primary side current or actual load verification method is used to realize the CT polarity verification of each branch.

[0003] If the above verification method is used to verify the CT polarity of the branches where each auxiliary transformer in the auxiliary power supply system of the operating nuclear power unit is located, each auxiliary transformer needs to be shut down. However, since each auxiliary transformer in the auxiliary power supply system bears the responsibility of the unit's backup power supply, if the auxiliary transformer is shut down, it may cause a short power outage in the operating nuclear power unit, and may even cause the operating nuclear power unit to be paralyzed, thereby causing a major safety accident.

[0004] Therefore, how to verify the CT polarity of the branch where each auxiliary transformer is located without stopping all the auxiliary transformers is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of this, the present invention provides a CT polarity verification method for an auxiliary power supply system, so as to verify the CT polarity of the branch where each auxiliary transformer is located without stopping all the auxiliary transformers.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] The present application provides a CT polarity verification method for an auxiliary power supply system, wherein the auxiliary power supply system includes at least two pairs of auxiliary transformers, two input busbars, and bus tie switches whose two ends are respectively connected to the two input busbars; the CT polarity verification method includes:

[0008] When the auxiliary power supply system is in normal operation, a circulating current is formed successively on the circuits where the bus tie switch and each pair of the auxiliary transformers are located; the two high-voltage sides of each pair of the auxiliary transformers are respectively connected to the two input busbars;

[0009] After each circulation current is formed, detecting the CT polarity relationship between the branches where the two auxiliary transformers forming the circulation current are located and the branch where the bus tie switch is located;

[0010] Taking the bus tie switch as a reference, the CT polarity relationship between the branches where the auxiliary transformers are located is determined according to the CT polarity relationship between the branches where the auxiliary transformers are located and the branch where the bus tie switch is located.

[0011] Optionally, forming a circulating current in the loops of the bus tie switch and each pair of the auxiliary transformers in sequence includes:

[0012] Closing the bus tie switch;

[0013] gradually connecting the two low-voltage sides of each pair of auxiliary transformers;

[0014] After the two low-voltage sides of a pair of the auxiliary transformers are connected each time, a voltage difference is generated between the pair of the auxiliary transformers whose two low-voltage sides are connected.

[0015] Optionally, generating a voltage difference between a pair of auxiliary transformers connected at two low-voltage sides includes:

[0016] The gear positions of the on-load tap changers of the pair of auxiliary transformers are adjusted so that there is a gear position difference between the gear positions of the on-load tap changers of the pair of auxiliary transformers.

[0017] Optionally, the current value of the circulating current formed each time is greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system.

[0018] Optionally, the auxiliary power supply system includes at least one construction transformer and two power lines, the high-voltage sides of all the construction transformers are connected to the same input bus, and the two input busbars are respectively connected to two power lines; after detecting the CT polarity relationship between the branches where each auxiliary transformer is located and the branches where the bus tie switch is located, it also includes:

[0019] When the auxiliary power supply system is in normal operation, closing the bus tie switch;

[0020] Detect the CT polarity relationship between the branch where each of the construction transformers is located, the branch where the power line corresponding to the first target input bus is located, and the branch where the bus tie switch is located; the first target input bus is the input bus to which the construction transformer is not connected;

[0021] Taking the bus tie switch as a reference, determine the CT polarity relationship between the branches where each construction transformer is located, the branches where the power lines corresponding to the first target input bus are located, and the branches where the bus tie switch is located, according to the CT polarity relationship between the branches where each construction transformer is located, the branches where the power lines corresponding to the first target input bus are located, and the branches where the auxiliary transformers are located.

[0022] Optionally, before detecting the CT polarity relationship between the branch where each of the construction transformers is located, the branch where the power-taking line corresponding to the first target input bus is located, and the branch where the bus tie switch is located, the method further includes:

[0023] Disconnect the connection between the second target input bus and its corresponding power supply line; the second target input bus is the input bus connected to the construction transformer.

[0024] Optionally, after determining the CT polarity relationship between the branch where each of the construction transformers is located, the branch where the power line corresponding to the first target input bus is located, and the branch where each of the auxiliary transformers is located, it also includes:

[0025] When the auxiliary power supply system is in normal operation, the CT polarity relationship between the branch where the target construction transformer is located and the branch where the power-taking line corresponding to the second target input bus is located is detected; the second target input bus is the input bus connected to the construction transformer, and the target construction transformer includes at least one construction transformer;

[0026] Taking the target construction transformer as a reference, determine the CT polarity relationship between the branch where the power line corresponding to the first target input bus is located and the branch where the power line corresponding to the second target input bus is located, based on the CT polarity relationship between the branch where the power line of the first target input bus is located, the branch where the power line of the second target input bus is located, and the branch where the target construction transformer is located.

[0027] Optionally, before closing the bus tie switch, or before detecting the CT polarity relationship between the branch where each of the construction transformers is located, the branch where the power line corresponding to the first target input bus is located, and the branch where the bus tie switch is located, the method further includes:

[0028] Adjust the load of at least one of the construction transformers so that the current of the second target input bus is greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system; the second target input bus is the input bus connected to the construction transformer.

[0029] Optionally, before forming a circulating current in the loops of the bus tie switch and each pair of the auxiliary transformers one by one, the method further includes:

[0030] determining whether any pair of the auxiliary transformers can operate under load while forming a circulating current;

[0031] If the pair of auxiliary transformers can operate under load while forming a circulating current, the steps of successively forming a circulating current on the bus tie switch and the loop where each pair of auxiliary transformers are located are performed.

[0032] Optionally, judging whether any pair of the auxiliary transformers can operate under load while forming a circulating current includes:

[0033] determining a required capacity of the auxiliary transformer in the pair of auxiliary transformers when a circulating current is formed in the pair of auxiliary transformers;

[0034] determining a maximum required capacity of the auxiliary transformer in the pair of the auxiliary transformers when the pair of the auxiliary transformers operates under load;

[0035] Determining whether the sum of the required capacity and the maximum required capacity is greater than the rated capacity of the auxiliary transformer;

[0036] If the sum of the required capacity and the maximum required capacity is less than or equal to the rated capacity, it is determined that the pair of auxiliary transformers can operate under load while forming a circulating current.

[0037] It can be seen from the above technical scheme that the present invention provides a CT polarity verification method for an auxiliary power supply system. Since a circulating current is formed on a loop where a pair of auxiliary transformers and a bus tie switch are located, the same current flows through the pair of auxiliary transformers and the bus tie switch, so the CT polarity relationship between the branches where the two auxiliary transformers where the circulating current is formed and the branches where the bus tie switch is located can be detected, so if a circulating current is formed on the loop where each pair of auxiliary transformers and the bus tie switch are located one by one, the CT polarity relationship between the branches where each auxiliary transformer is located and the branches where the bus tie switch is located can be detected, and then the bus tie switch is used as a reference to obtain the CT polarity relationship between the branches where each auxiliary transformer is located; and since the circulating current is formed when the auxiliary power supply system is in a normal operating state, that is, all auxiliary transformers are not shut down before the circulating current is formed, and the formation of the circulating current will not cause any auxiliary transformer to shut down, so in the process of obtaining the CT polarity relationship between the branches where each auxiliary transformer is located, all auxiliary transformers are not shut down, so the CT polarity verification method can realize the verification of the CT polarity of the branches where each auxiliary transformer is located when all auxiliary transformers are not shut down. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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 only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0039] Figure 1 A schematic diagram of the structure of an implementation scheme of an auxiliary power supply system provided in an embodiment of the present application;

[0040] Figure 2 A flowchart of an implementation method of a CT polarity verification method for an auxiliary power system provided in an embodiment of the present application;

[0041] Figure 3 A flowchart of an implementation of step S120 provided in an embodiment of the present application;

[0042] Figure 4 A schematic diagram of the structure of another implementation of the auxiliary power supply system provided in an embodiment of the present application;

[0043] Figure 5 is a structural schematic diagram of an equivalent circuit of a pair of auxiliary transformers when a voltage difference is generated between the pair of auxiliary transformers;

[0044] Figure 6-Figure 12Schematic diagrams of the flow charts of seven other implementations of the CT polarity verification method of the auxiliary power system provided in the embodiments of the present application;

[0045] Figure 13-Figure 15 The following are structural schematic diagrams of three further implementation modes of the auxiliary power supply system provided in the embodiments of the present application. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0047] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0048] In order to verify the CT polarity of the branches where each auxiliary transformer is located without stopping all the auxiliary transformers, another embodiment of the present application provides a CT polarity verification method for an auxiliary power supply system.

[0049] like Figure 1 As shown, the auxiliary power supply system includes: a bus tie switch Sm, two input busbars 10, at least two pairs of auxiliary transformers 20 and at least five first current transformers CT 30.

[0050] Both ends of the bus tie switch Sm are connected to the two input busbars 10 , respectively. The two high-voltage sides of each pair of auxiliary transformers 20 are connected to the two input busbars 10 , respectively.

[0051] The two high-voltage sides of each pair of auxiliary transformers 20 specifically refer to the high-voltage sides of the two auxiliary transformers 20 in each pair of auxiliary transformers 20 .

[0052] Assuming that the auxiliary power supply system includes three pairs of auxiliary transformers, the two high-voltage sides of each pair of auxiliary transformers are respectively connected to the two input busbars, which means that: the two high-voltage sides of the first pair of auxiliary transformers are respectively connected to the two input busbars, the two high-voltage sides of the second pair of auxiliary transformers are respectively connected to the two input busbars, and the two high-voltage sides of the third pair of auxiliary transformers are respectively connected to the two input busbars.

[0053] The high voltage side of each auxiliary transformer 20 is connected in series with the primary side of a first CT 30; assuming that the auxiliary power supply system includes three pairs of auxiliary transformers, the high voltage side of each auxiliary transformer is connected in series with the primary side of a first CT as follows: the high voltage side of the first auxiliary transformer is connected to the primary side of the first CT No. A, the high voltage side of the second auxiliary transformer is connected to the primary side of the first CT No. B, the high voltage side of the third auxiliary transformer is connected to the primary side of the first CT No. C, the high voltage side of the fourth auxiliary transformer is connected to the primary side of the first CT No. D, the high voltage side of the fifth auxiliary transformer is connected to the primary side of the first CT No. E, and the high voltage side of the sixth auxiliary transformer is connected to the primary side of the first CT No. F.

[0054] The bus tie switch Sm is connected in series with the primary side of a first CT 30; the secondary side of each first CT 30 is connected to the first bus differential protection device 01 in the power generation system corresponding to the auxiliary power system.

[0055] The low-voltage sides of the auxiliary transformers 20 serve as output ends of the auxiliary power supply system. Normally, the low-voltage sides of the auxiliary transformers 20 are connected to the output bus bars 40, respectively. The output bus bars 40 serve as output ends of the auxiliary power supply system and are connected to the power supply ends of the devices that require backup power.

[0056] It should be noted that in order to simplify the view, Figure 1 In the figure, only a pair of auxiliary transformers is taken as an example to show the connection relationship of the low-voltage side of the auxiliary transformer, while the connection relationship of the low-voltage side of other auxiliary transformers is not shown.

[0057] In a specific example, if the auxiliary power system is installed in a nuclear power plant, then Figure 1 ( Figure 1 As shown in the example of two auxiliary transformers with electric boilers connected to the low-voltage sides, the device requiring a backup power supply can be the electric boiler 02 in the nuclear power plant. As for the use of the electric boiler 02 in the nuclear power plant, it is already very mature in the prior art and will not be described here.

[0058] The above is only one implementation method of a device that requires a backup power supply. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances, all of which are within the scope of protection of this application.

[0059] The specific process of the CT polarity verification method is as follows Figure 2 As shown, the specific steps include:

[0060] S110: Determine whether the auxiliary power supply system is in normal operation.

[0061] If the auxiliary power system is in a normal operating state, step S120 is executed; if the auxiliary power system is not in a normal operating state, the CT polarity verification method is stopped.

[0062] Among them, the auxiliary power supply system is in normal operation, indicating that: all auxiliary transformers are in operation, the busbar switch is not closed, and the two low-voltage sides of each pair of auxiliary transformers are not connected.

[0063] In a specific example, all auxiliary transformers are in operation, including: a part of the auxiliary transformers are running at no load, and another part of the auxiliary transformers are running at load.

[0064] It can be understood that if there is no load connected to the low-voltage side of an auxiliary transformer, the auxiliary transformer operates at no-load, that is, the auxiliary transformer still serves as a backup power supply; if there is a load connected to the low-voltage side of an auxiliary transformer, the auxiliary transformer operates with load, that is, the auxiliary transformer replaces the main power supply to provide electrical energy.

[0065] In another specific example, all auxiliary transformers are in operation, including: all auxiliary transformers are running at no load.

[0066] It should be noted that no-load operation has been described in detail above and will not be repeated here.

[0067] The above two examples show two implementation methods in which all auxiliary transformers are in operation. No specific limitation is made here and it can be determined according to the specific situation, which is within the protection scope of this application.

[0068] S120, forming a circulating current in the circuits where the busbar switch and each pair of auxiliary transformers are located one by one.

[0069] It should be noted that the meaning of each pair of auxiliary transformers has been explained above and will not be repeated here.

[0070] Assuming that the auxiliary power supply system includes three pairs of auxiliary transformers, the meaning of successively forming a circulating current in the circuit between the bus tie switch and each pair of auxiliary transformers is specifically as follows: the circulating current is formed in the circuit between the bus tie switch and the first pair of auxiliary transformers for the first time, the circulating current is formed in the circuit between the bus tie switch and the second pair of auxiliary transformers for the second time, and the circulating current is formed in the circuit between the bus tie switch and the third pair of auxiliary transformers for the third time.

[0071] In a specific example, the current value of the circulating current formed each time is greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system.

[0072] Among them, the minimum sampling current accuracy of the bus differential protection device is: the minimum current that the bus differential protection device can sample; in practical applications, the minimum sampling current accuracy of the bus differential protection device is set according to actual conditions and is not specifically limited here; usually, it can be 15A.

[0073] The above example only shows one implementation method of the current value of the circulating current formed each time. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to the specific situation and is within the protection scope of this application.

[0074] S130. After each circulating current is formed, detect the CT polarity relationship between the branches where the two auxiliary transformers forming the circulating current are located and the branch where the bus tie switch is located.

[0075] Assuming that a circulating current is formed on the circuit where the bus tie switch and the first pair of auxiliary transformers are located for the first time, a circulating current is formed on the circuit where the bus tie switch and the second pair of auxiliary transformers are located for the second time, and a circulating current is formed on the circuit where the bus tie switch and the third pair of auxiliary transformers are located for the third time, then after each circulating current is formed, the meaning of detecting the CT polarity relationship between the branches where the two auxiliary transformers forming the circulating current are located and the branches where the bus tie switch is located is specifically as follows: after the circulating current is formed for the first time, the CT polarities of the branches where the two auxiliary transformers in the first pair of auxiliary transformers are located and the branches where the bus tie switch is located are detected; after the circulating current is formed for the second time, the CT polarities of the branches where the two auxiliary transformers in the second pair of auxiliary transformers are located and the branches where the bus tie switch is located are detected; after the circulating current is formed for the third time, the CT polarities of the branches where the two auxiliary transformers in the third pair of auxiliary transformers are located and the branches where the bus tie switch is located are detected.

[0076] Among them, the CT polarity relationship between the branch where the auxiliary transformer is located and the branch where the bus tie switch is located can be understood as: the relationship between the polarity of the CT of the branch where the auxiliary transformer is located and the polarity of the CT of the branch where the bus tie switch is located; it specifically includes: the polarity of the CT of the branch where the auxiliary transformer is located is the same as the polarity of the CT of the branch where the bus tie switch is located, or, the polarity of the CT of the branch where the auxiliary transformer is located is different from the polarity of the CT of the branch where the bus tie switch is located.

[0077] For example, assuming that the polarity of the CT of the branch where the auxiliary transformer is located is a subtractive polarity, and the polarity of the CT of the branch where the bus tie switch is located is also a subtractive polarity, then the polarity relationship between the CT of the branch where the auxiliary transformer is located and the branch where the bus tie switch is located is: the polarity of the CT of the branch where the auxiliary transformer is located is the same as the polarity of the CT of the branch where the bus tie switch is located.

[0078] In addition, the CT of the branch where the auxiliary transformer is located refers to: the CT whose primary side is connected in series on the branch where the auxiliary transformer is located. Usually, the primary side of the CT is connected in series with the high-voltage side of the auxiliary transformer; the CT of the branch where the bus tie switch is located refers to: the CT whose primary side is connected in series on the branch where the bus tie switch is located.

[0079] In addition, the branch where the auxiliary transformer is located means: the branch where the auxiliary transformer is located; the branch where the main coupling switch is located means: the branch where the main coupling switch is located.

[0080] S140. With the bus tie switch as a reference, determine the CT polarity relationship between the branches where the auxiliary transformers are located according to the CT polarity relationship between the branches where the auxiliary transformers are located and the branch where the bus tie switch is located.

[0081] Among them, the CT polarity relationship between the branches where the auxiliary transformers are located can be understood as: the relationship between the polarities of the CTs of the branches where the auxiliary transformers are located; which specifically includes: the polarities of the CTs of the branches where the auxiliary transformers are located are exactly the same, or the polarities of the CTs of the branches where the auxiliary transformers are located are not exactly the same.

[0082] For example, assuming that the auxiliary transformer includes three pairs of auxiliary transformers, and the polarities of the CTs of the six auxiliary transformers in the three pairs of auxiliary transformers are the same as the polarity of the CT of the branch where the bus tie switch is located, the polarities of the CTs of the six auxiliary transformers are the same.

[0083] Since a circulating current is formed on the circuit where a pair of auxiliary transformers and the bus tie switch are located, the same current flows through the pair of auxiliary transformers and the bus tie switch, so the CT polarity relationship between the branches where the two auxiliary transformers forming the circulating current are located and the branch where the bus tie switch is located can be detected. Therefore, if the circulating current is formed on the circuit where each pair of auxiliary transformers and the bus tie switch are located one by one, the CT polarity relationship between the branches where each auxiliary transformer is located and the branch where the bus tie switch is located can be detected, and then the CT polarity relationship between the branches where each auxiliary transformer is located can be obtained with the bus tie switch as a reference; and since the circulating current is formed when the auxiliary power supply system is in normal operation, that is, all auxiliary transformers are not shut down before the circulating current is formed, and the formation of the circulating current will not shut down any auxiliary transformer, so in the process of obtaining the CT polarity relationship between the branches where each auxiliary transformer is located, all auxiliary transformers are not shut down, so the CT polarity verification method can realize the verification of the CT polarity of the branches where each auxiliary transformer is located when all auxiliary transformers are not shut down.

[0084] In addition, since a circulating current is formed in the circuit where each pair of auxiliary transformers and the busbar switch are located during the verification of the CT polarity of the branches where the two auxiliary transformers in each pair of auxiliary transformers are located, the possibility of no-load in each pair of auxiliary transformers during the verification process is reduced, thereby reducing the possibility of damage to the auxiliary transformers, thereby improving the safety of the CT polarity verification method.

[0085] Another embodiment of the present application provides a specific implementation of step S120. The specific process of this implementation is as follows: Figure 3 As shown, the specific steps include:

[0086] S210, close the main tie switch.

[0087] It can be seen from the connection relationship of the bus tie switch that when the bus tie switch is closed, the two input busbars are connected, so the high-voltage sides of each auxiliary transformer are connected.

[0088] S220, successively connect the two low-voltage sides of each pair of auxiliary transformers.

[0089] Assuming that the auxiliary power supply system includes three pairs of auxiliary transformers, the meaning of successively connecting the two low-voltage sides of each pair of auxiliary transformers is specifically: connecting the two low-voltage sides of the first pair of auxiliary transformers for the first time, connecting the two low-voltage sides of the second pair of auxiliary transformers for the second time, and connecting the two low-voltage sides of the third pair of auxiliary transformers for the third time.

[0090] In a specific example, a connecting switch is provided between two output busbars connected to the two low-voltage sides of each pair of auxiliary transformers. The purpose of connecting the two low-voltage sides of each pair of auxiliary transformers can be achieved by successively controlling each connecting switch to close.

[0091] The above example only shows one implementation of step S220. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances, all of which are within the scope of protection of this application.

[0092] S230. After the two low-voltage sides of a pair of auxiliary transformers are connected each time, a voltage difference is generated between the pair of auxiliary transformers whose two low-voltage sides are connected.

[0093] In a specific example, the voltage difference generated each time is equal to the preset voltage.

[0094] Among them, the preset voltage is a voltage value that makes the current in the circuit where a pair of auxiliary transformers and the bus tie switch that generate the pressure difference greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system. In other words, if the pressure difference generated between a pair of auxiliary transformers is equal to the preset voltage, the current in the circuit where the pair of auxiliary transformers and the bus tie switch are located is greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system.

[0095] It should be noted that the minimum sampling current accuracy of the bus differential protection device has been described in detail above and will not be repeated here.

[0096] The above is only one implementation method of the generated pressure difference. In practical applications, including but not limited to this, no specific limitation is made here. It can be determined according to the specific situation and is within the protection scope of this application.

[0097] In a specific example, generating a voltage difference between a pair of auxiliary transformers connected at two low voltage sides includes: adjusting the gears of the on-load tap changers of the pair of auxiliary transformers so that there is a gear difference between the gears of the on-load tap changers of the pair of auxiliary transformers.

[0098] If the generated voltage differences are all equal to the preset voltage, then the gear difference between the gears of the on-load tap changers of the pair of auxiliary transformers is equal to the preset value.

[0099] Among them, the preset value is a voltage value that makes the current in the circuit where a pair of auxiliary transformers and bus tie switches with a gear difference in the gear of the on-load tap changer are located greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system. In other words, if the gear difference between the gears of the on-load tap changers of a pair of auxiliary transformers is equal to the preset value, then the current in the circuit where the pair of auxiliary transformers and bus tie switches are located is greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system.

[0100] It should be noted that the minimum sampling current accuracy of the bus differential protection device has been described in detail above and will not be repeated here.

[0101] The following takes a pair of auxiliary transformers as an example to explain in detail the process of determining the preset value, as described below:

[0102] Assume that the parameters of the auxiliary transformer are as shown in the following table:

[0103]

[0104] When a voltage difference is generated between the pair of auxiliary transformers, the equivalent circuit of the pair of auxiliary transformers is as follows: Figure 5 shown.

[0105] The short-circuit impedance of the two auxiliary transformers in the pair of auxiliary transformers ; The pressure difference generated The commutation formed ; Among them, In is the high voltage side and N is the gear difference of the on-load tap changer of the pair of auxiliary transformers.

[0106] Substituting the parameters in the above table into the above three formulas, we can obtain the relationship between the formed commutation Ir and the gear difference N of the on-load tap changers of the pair of auxiliary transformers: Ir=7.78N, that is, the commutation formed is 7.78A for every one-gear difference in the on-load tap changers of the pair of auxiliary transformers.

[0107] Since the above formula ignores other impedances in the loop, such as on-load tap changer impedance and main loop impedance, the actual value of Ir is slightly smaller than 7.78N; assuming that the minimum sampling current accuracy of the bus differential protection device is 15A, in actual applications, in order to ensure reliability, N is selected to be equal to 3, that is, the preset value is equal to 3, that is, the resulting commutation is 23A, which is greater than the minimum sampling current accuracy of the bus differential protection device.

[0108] The above is only one implementation method of generating a voltage difference between a pair of auxiliary transformers. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances, all of which are within the scope of protection of this application.

[0109] The above is only one implementation of step S120. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances, all of which are within the scope of protection of this application.

[0110] Another embodiment of the present application provides another implementation of the CT polarity verification method for an auxiliary power supply system, which is applicable to the situation where the auxiliary power supply system includes at least one construction transformer and two power supply lines, and the high-voltage sides of all construction transformers are connected to the same input bus, and the two input busbars are respectively connected to two power supply lines.

[0111] Among them, the input busbar not connected to the construction transformer is the first target input busbar, and the input busbar connected to the construction transformer is the second target input busbar.

[0112] Assuming that the auxiliary power supply system includes a construction transformer and two power lines, and the first input bus is connected to the first power line, the second input bus is connected to the second power line, and the construction transformer is connected to the second input bus, then the second input bus is the second target input bus, and the first input bus is the first target input bus.

[0113] The specific process of this implementation is as follows Figure 6 (To simplify the schematic, Figure 6(Steps S110 to S140 are omitted), in the above embodiment, after detecting the CT polarity relationship between the branches where each auxiliary transformer is located and the branches where the bus tie switch is located, that is, after step S130, this embodiment further includes the following steps:

[0114] S310: Determine whether the auxiliary power supply system is in normal operation.

[0115] If the auxiliary power supply system is in a normal operating state, steps S320, S330, and S340 are executed in sequence; if the auxiliary power supply system is not in a normal operating state, the CT polarity verification method is stopped.

[0116] In this embodiment, since the auxiliary power supply system also includes at least one construction transformer and two power supply lines, the auxiliary power supply system is in normal operation. In addition to the meaning in the above embodiments, it also indicates that all construction transformers draw power in turn through the second target input bus and the power supply lines corresponding to the second target input bus.

[0117] It should be noted that the meaning of the auxiliary power system being in normal operating state has been described in detail above and will not be repeated here.

[0118] S320, close the main tie switch.

[0119] It can be seen from the connection relationship of the bus tie switch that when the bus tie switch is closed, the two input busbars are connected.

[0120] S330, detecting the CT polarity relationship between the branch where each construction transformer is located, the branch where the power-taking line corresponding to the first target input bus is located, and the branch where the bus tie switch is located.

[0121] Assuming that the second input bus is the second target input bus, the first input bus is the first target input bus, and the first input bus is connected to the first power line, and the second input bus is connected to the second power line, then the power line corresponding to the first target input bus is the first power line, and the power line corresponding to the second target input bus is the second power line.

[0122] In addition, the CT polarity relationship between the branch where the construction transformer is located and the branch where the bus tie switch is located can be understood as: the relationship between the polarity of the CT of the branch where the construction transformer is located and the polarity of the CT of the branch where the bus tie switch is located; it specifically includes: the polarity of the CT of the branch where the construction transformer is located is the same as the polarity of the CT of the branch where the bus tie switch is located, or, the polarity of the CT of the branch where the construction transformer is located is different from the polarity of the CT of the branch where the bus tie switch is located.

[0123] For example, assuming that the auxiliary power supply system includes a construction transformer, if the CT polarity of the branch where the construction transformer is located is a subtractive polarity, and the CT polarity of the branch where the bus tie switch is located is also a subtractive polarity, then the CT polarity relationship between the branch where the construction transformer is located and the branch where the bus tie switch is located is: the CT polarity of the branch where the construction transformer is located is the same as the CT polarity of the branch where the bus tie switch is located.

[0124] In addition, the CT polarity relationship between the branch where the power line corresponding to the first target input bus is located and the branch where the bus tie switch is located can be understood as: the relationship between the polarity of the CT of the branch where the power line corresponding to the first target input bus is located and the polarity of the CT of the branch where the bus tie switch is located; it specifically includes: the polarity of the CT of the branch where the power line corresponding to the first target input bus is located is the same as the polarity of the CT of the branch where the bus tie switch is located, or, the polarity of the CT of the branch where the power line corresponding to the first target input bus is located is different from the polarity of the CT of the branch where the bus tie switch is located.

[0125] For example, if the polarity of the CT of the branch where the power line corresponding to the first target input bus is located is a subtractive polarity, and the polarity of the CT of the branch where the bus tie switch is located is also a subtractive polarity, then the relationship between the CT polarity of the branch where the power line corresponding to the first target input bus is located and the branch where the bus tie switch is located is: the polarity of the CT of the branch where the power line corresponding to the first target input bus is located is the same as the polarity of the CT of the branch where the bus tie switch is located.

[0126] In addition, the CT of the branch where the construction transformer is located refers to: the CT whose primary side is connected in series on the branch where the construction transformer is located. Usually, the primary side of the CT is connected in series with the high-voltage side of the construction transformer; the CT of the branch where the power-taking line corresponding to the first target input bus is located refers to: the CT whose primary side is connected in series on the branch where the power-taking line corresponding to the first target input bus is located.

[0127] In addition, the branch where the construction transformer is located means: the branch where the construction transformer is located; the branch where the power line is located means: the branch where the power line is located.

[0128] S340. Taking the bus tie switch as a reference, determine the CT polarity relationship between the branches where each construction transformer is located, the branches where the power lines corresponding to the first target input bus are located, and the branches where each auxiliary transformer is located, according to the CT polarity relationship between the branches where each construction transformer is located, the branches where the power lines corresponding to the first target input bus are located, and the branches where the bus tie switch is located, as well as the CT polarity relationship between the branches where each auxiliary transformer is located and the branch where the bus tie switch is located.

[0129] Among them, the CT polarity relationship between the branches where each construction transformer is located, the branches where the power lines corresponding to the first target input bus are located, and the branches where each auxiliary transformer is located can be understood as: the relationship between the polarity of the CT of the branch where each construction transformer is located, the polarity of the CT of the branch where the power lines corresponding to the first target input bus are located, and the polarity of the CT of the branch where each auxiliary transformer is located; it specifically includes: the polarity of the CT of the branch where each construction transformer is located, the polarity of the CT of the branch where the power lines corresponding to the first target input bus are located, and the polarity of the CT of the branch where each auxiliary transformer is located are exactly the same, or, the polarity of the CT of the branch where each construction transformer is located, the polarity of the CT of the branch where the power lines corresponding to the first target input bus are located, and the polarity of the CT of the branch where each auxiliary transformer is located are not exactly the same.

[0130] For example, assuming that the auxiliary transformer includes three pairs of auxiliary transformers and one construction transformer, and the polarities of the CTs of the six auxiliary transformers in the three pairs of auxiliary transformers are the same as the polarity of the CT of the branch where the bus tie switch is located, and the polarity of the CT of the branch where the construction transformer is located and the polarity of the CT of the branch where the power taking line corresponding to the first target input bus is located are the same as the polarity of the CT of the branch where the bus tie switch is located, then the polarities of the CTs of the six auxiliary transformers, the polarity of the CT of the branch where the construction transformer is located, and the polarity of the CT of the branch where the power taking line corresponding to the first target input bus is located are exactly the same.

[0131] From the above, it can be seen that when the auxiliary power supply system is in normal operation, all construction transformers draw power in turn through the second target input bus and the power supply line corresponding to the second target input bus. Therefore, when the bus tie switch is closed, the two input busbars are connected. Under the influence of system power flow changes, all construction transformers change from originally drawing power in turn through the second target input bus and the power supply line corresponding to the second target input bus to drawing power in turn through the second target input bus, the bus tie switch, the first target input bus, and the power supply line corresponding to the first target input bus. In other words, under the influence of system power flow changes, the current changes from flowing through the power supply line corresponding to the second target input bus, the second target input bus, and all construction transformers to flowing through the power supply line corresponding to the first target input bus, the first target input bus, the bus tie switch, the second target input bus, and all construction transformers. It is thus possible to detect the branches where each construction transformer is located and the branches where the power supply line corresponding to the first target input bus is located, which are respectively connected to the branches of the bus tie switch. The CT polarity relationship of the branches; therefore, taking the main coupling switch as a reference, and combining the CT polarity relationship of the branches where each auxiliary transformer is located with the branches where the main coupling switch is located, the CT polarity relationship between the branches where each construction transformer is located, the branches where the power lines corresponding to the first target input bus are located, and the branches where each auxiliary transformer is located can be obtained; and because the main coupling switch is closed when the auxiliary power supply system is in normal operation, that is, all auxiliary transformers are not shut down before the main coupling switch is closed, so in the process of obtaining the CT polarity relationship between the branches where each construction transformer is located, the branches where the power lines corresponding to the first target input bus are located, and the branches where each auxiliary transformer is located, all auxiliary transformers are not shut down, so that the CT polarity verification method can further verify the CT polarity relationship between the branches where each construction transformer is located, the branches where the power lines corresponding to the first target input bus are located, and the branches where each auxiliary transformer is located when all auxiliary transformers are not shut down.

[0132] This embodiment provides another implementation method of the CT polarity verification method of the auxiliary power supply system, which is also applicable to the situation where the auxiliary power supply system includes at least one construction transformer and two power supply lines, and the high-voltage sides of all construction transformers are connected to the same input bus, and the two input busbars are respectively connected to the two power supply lines.

[0133] It should be noted that the detailed introduction of the applicable situations has been explained above and will not be repeated here.

[0134] The specific process of this implementation is as follows Figure 7 (To simplify the schematic, Figure 7Steps S110 to S140 are omitted), and this implementation mode further includes the following steps before step S330 in the previous implementation mode provided in this embodiment:

[0135] S410, disconnecting the second target input bus and the corresponding power supply line.

[0136] It should be noted that the meaning of the second target input bus has been described in detail above and will not be repeated here.

[0137] In this embodiment, since the connection between the second target input bus and the power supply line corresponding to it is disconnected before step S330, all construction transformers are not affected by the system power flow changes. The original power supply is obtained through the second target input bus and the power supply line corresponding to the second target input bus in sequence, and the power supply is changed to be obtained through the second target input bus, the bus tie switch, the first target input bus, and the power supply line corresponding to the first target input bus in sequence. Therefore, this embodiment can also further verify the CT polarity relationship between the branches where each construction transformer is located, the branches where the power supply line corresponding to the first target input bus is located, and the branches where each auxiliary transformer is located. As for the specific derivation process, it is the same as the previous embodiment and will not be repeated here.

[0138] This embodiment provides another implementation method of the CT polarity verification method of the auxiliary power supply system, which is also applicable to the situation where the auxiliary power supply system includes at least one construction transformer and two power supply lines, and the high-voltage sides of all construction transformers are connected to the same input bus, and the two input busbars are respectively connected to two power supply lines.

[0139] It should be noted that the detailed introduction of the applicable situations has been explained above and will not be repeated here.

[0140] The specific process of this implementation can be found in Figure 8 (To simplify the schematic, Figure 7 Steps S110 to S140 are omitted. Figure 8 Only step S420 before step S320 is used as an example for demonstration). This implementation mode further includes the following steps before step S320 or S330 in the previous implementation mode provided in this embodiment:

[0141] S420. Adjust the load of at least one construction transformer so that the current of the second input bus is greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system.

[0142] It should be noted that the meaning of the second target input bus and the meaning of the minimum sampling current accuracy of the bus differential protection device have been described in detail above and will not be repeated here.

[0143] The above are only three implementation methods of the CT polarity verification method of the auxiliary power system. In practical applications, including but not limited to these, no specific limitations are made here and they are all within the protection scope of this application.

[0144] Another embodiment of the present application provides yet another implementation of the CT polarity verification method for an auxiliary power supply system, which is also applicable to the situation where the auxiliary power supply system includes at least one construction transformer and two power supply lines, and the high-voltage sides of all construction transformers are connected to the same input bus, and the two input busbars are respectively connected to two power supply lines.

[0145] It should be noted that the detailed introduction of the applicable situations has been explained above and will not be repeated here.

[0146] The specific process of this implementation is as follows Fig. 9 (To simplify the schematic, Fig. 9 Steps S110 to S140, steps S310 to S330 are omitted, and steps S410 and S420 are omitted), this embodiment further includes the following steps after step S340 in the above two embodiments:

[0147] S510: Determine whether the auxiliary power supply system is in normal operation.

[0148] If the auxiliary power supply system is in a normal operating state, steps S520 and S530 are executed in sequence; if the auxiliary power supply system is not in a normal operating state, the CT polarity verification method is stopped.

[0149] It should be noted that the meaning of the auxiliary power system being in normal operating state has been described in detail above and will not be repeated here.

[0150] S520, detecting the CT polarity relationship between the branch where the target construction transformer is located and the branch where the power-taking line corresponding to the second target input bus is located.

[0151] It should be noted that the meaning of the second target input bus has been described in detail above and will not be repeated here.

[0152] Among them, the target construction transformer includes at least one construction transformer.

[0153] In addition, the CT polarity relationship between the branch where the target construction transformer is located and the branch where the power line corresponding to the second target input bus is located can be understood as: the relationship between the polarity of the CT of the branch where the target construction transformer is located and the polarity of the CT of the branch where the power line corresponding to the second target input bus is located; which specifically includes: the polarity of the CT of the branch where the target construction transformer is located is the same as the polarity of the CT of the branch where the power line corresponding to the second target input bus is located, or, the polarity of the CT of the branch where the target construction transformer is located is different from the polarity of the CT of the branch where the power line corresponding to the second target input bus is located.

[0154] For example, assuming that the polarity of the CT of the branch where the target construction transformer is located is a subtractive polarity, and the polarity of the CT of the branch where the power line corresponding to the second target input bus is located is also a subtractive polarity, then the CT polarity relationship between the branch where the target construction transformer is located and the branch where the power line corresponding to the second target input bus is located is: the polarity of the CT of the branch where the target construction transformer is located is the same as the polarity of the CT of the branch where the power line corresponding to the second target input bus is located.

[0155] It should be noted that the CT of the branch where the power line corresponding to the second target input bus is located refers to: the CT on the primary side connected in series on the branch where the power line corresponding to the second target input bus is located; as for the polarity of the CT of the branch where the construction transformer is located, it has been described in detail above and will not be repeated here.

[0156] S530. Taking the target construction transformer as a reference, determine the CT polarity relationship between the branch where the power line corresponding to the first target input bus is located and the branch where the power line corresponding to the second target input bus is located according to the CT polarity relationship between the branch where the power line of the first target input bus is located, the branch where the power line of the second target input bus is located and the branch where the target construction transformer is located.

[0157] Among them, the CT polarity relationship between the branch where the power line corresponding to the first target input bus is located and the branch where the power line corresponding to the second target input bus is located can be understood as: the relationship between the polarity of the CT of the branch where the power line corresponding to the first target input bus is located and the polarity of the CT of the branch where the power line corresponding to the second target input bus is located; it specifically includes: the polarity of the CT of the branch where the power line corresponding to the first target input bus is located is the same as the polarity of the CT of the branch where the power line corresponding to the second target input bus is located, or, the polarity of the CT of the branch where the power line corresponding to the first target input bus is located is different from the polarity of the CT of the branch where the power line corresponding to the second target input bus is located.

[0158] For example, assuming that the polarity of the CT of the branch where the target construction transformer is located is the same as the polarity of the CT of the branch where the power line corresponding to the first target input bus is located, and the polarity of the CT of the branch where the target construction transformer is located is the same as the polarity of the CT of the branch where the power line corresponding to the second target input bus is located, then the polarity of the CT of the branch where the power line corresponding to the first target input bus is located is the same as the polarity of the CT of the branch where the power line corresponding to the second target input bus is located.

[0159] In this embodiment, when the auxiliary power supply system is in normal operation, all construction transformers draw power in turn through the second target input bus and the power supply line corresponding to the second target input bus. Therefore, when the bus tie switch is closed, current flows through the power supply line corresponding to the second target input bus, the second target input bus, and all construction transformers. Therefore, the CT polarity relationship between the branch where the target construction transformer is located and the branch where the power supply line corresponding to the second target input bus is located can be detected; thus, taking the target construction transformer as a reference, and combining the CT polarity relationship between the branch where the power supply line of the first target input bus is located and the branch where the target construction transformer is located, the CT polarity relationship between the branch where the power supply line corresponding to the first target input bus is located and the branch where the target construction transformer is located can be obtained. The CT polarity relationship between the branches where the power lines corresponding to the second target input bus are located; and because the CT polarity detection is performed when the auxiliary power supply system is in normal operation, that is, all auxiliary transformers are not shut down before the CT polarity detection, so in the process of obtaining the CT polarity relationship between the branches where the power lines corresponding to the first target input bus are located and the branches where the power lines corresponding to the second target input bus are located, all auxiliary transformers are not shut down. Therefore, the CT polarity verification method can further verify the CT polarity relationship between the branches where the power lines corresponding to the first target input bus are located and the branches where the power lines corresponding to the second target input bus are located when all auxiliary transformers are not shut down.

[0160] This embodiment also provides another implementation method of the CT polarity verification method of the auxiliary power supply system, which is also applicable to the situation where the auxiliary power supply system includes at least one construction transformer and two power supply lines, and the high-voltage sides of all construction transformers are connected to the same input bus, and the two input busbars are respectively connected to the two power supply lines.

[0161] It should be noted that the detailed introduction of the applicable situations has been explained above and will not be repeated here.

[0162] The specific process of this implementation is as follows Fig.10 (To simplify the schematic, Fig.10Steps S110 to S140, steps S310 to S330 are omitted, and steps S410 and S420 are omitted). This implementation mode further includes the following steps before step S520 in the above three implementation modes provided in this embodiment:

[0163] S610. Adjust the load of at least one construction transformer so that the current of the second target input bus is greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system.

[0164] It should be noted that the meaning of the second target input bus and the meaning of the minimum sampling current accuracy of the bus differential protection device have been described in detail above and will not be repeated here.

[0165] The above are only two implementation methods of the CT polarity verification method for the auxiliary power system, which are not specifically limited here and can be determined according to specific circumstances, all of which are within the protection scope of this application.

[0166] Another embodiment of the present application provides another implementation method of the CT polarity verification method of the auxiliary power system. The specific process can be found in Fig.11 ( Fig.11 Only in Figure 1 This embodiment further includes the following steps before step S120 in the above embodiment:

[0167] S710: Determine whether any pair of auxiliary transformers can operate under load while forming a circulating current.

[0168] If the pair of auxiliary transformers can operate with load while forming a circulating current, step S120 is executed; if the pair of auxiliary transformers cannot operate with load while forming a circulating current, the CT polarity verification method is stopped.

[0169] The pair of auxiliary transformers forms a circulating current, which specifically refers to forming a commutation in the loop where the pair of auxiliary transformers and the bus tie switch are located.

[0170] In addition, the pair of auxiliary transformers operating under load includes: two auxiliary transformers in the pair of auxiliary transformers operating under load at the same time, and any one auxiliary transformer in the pair of auxiliary transformers operating under load alone.

[0171] It can be seen from this that if any pair of auxiliary transformers is not damaged in the following two situations, it is considered that the pair of auxiliary transformers can operate under load while forming a circulating current; one of the situations is: while forming a circulating current in any pair of auxiliary transformers, the two auxiliary transformers in the pair of auxiliary transformers are operated under load at the same time, and the other situation is: while forming a circulating current in any pair of auxiliary transformers, any auxiliary transformer in the pair of auxiliary transformers is operated alone under load.

[0172] In practical applications, the actual parameters of each auxiliary transformer in the auxiliary power supply system are the same. Therefore, performing the above judgment on any pair of auxiliary transformers is equivalent to performing the above judgment on each pair of auxiliary transformers. In other words, as long as any pair of auxiliary transformers can operate with load while forming a circulating current, each pair of auxiliary transformers can operate with load while forming a circulating current.

[0173] In this embodiment, before the circulating current is formed, it is judged whether any pair of auxiliary transformers can operate under load while the circulating current is formed, so that the auxiliary transformers can replace the main power supply to supply power at any time when the circulating current is formed, thereby improving the safety performance of the power generation system corresponding to the auxiliary power supply system.

[0174] Another embodiment of the present application provides a specific implementation of step S710, and the specific process is as follows: Fig.12 As shown, the specific steps include:

[0175] S810: Determine the required capacity of the auxiliary transformer in the pair of auxiliary transformers when the pair of auxiliary transformers forms a circulating current.

[0176] Still taking the auxiliary transformer with parameters shown in the above table as an example, the process of determining the required capacity of the auxiliary transformer in the pair of auxiliary transformers when the pair of auxiliary transformers forms a circulating current is described in detail, as follows:

[0177] When the pair of auxiliary transformers forms a circulating current, the power of the auxiliary transformer in the pair of auxiliary transformers is basically reactive power. Therefore, the required capacity of the auxiliary transformer in the pair of auxiliary transformers is .

[0178] S820: Determine the maximum required capacity of the auxiliary transformer in the pair of auxiliary transformers when the pair of auxiliary transformers are operating under load.

[0179] Assuming that when the two auxiliary transformers in the pair of auxiliary transformers are operated under load at the same time, the required capacity of each auxiliary transformer is P1, and when any one of the auxiliary transformers in the pair of auxiliary transformers is operated under load alone, the required capacities of the two auxiliary transformers are 0 and P2 respectively, if P2 is greater than P1, then the maximum required capacity of the auxiliary transformer in the pair of auxiliary transformers when the pair of auxiliary transformers is operated under load is P2, and if P2 is less than P1, then the maximum required capacity of the auxiliary transformer in the pair of auxiliary transformers when the pair of auxiliary transformers is operated under load is P1.

[0180] Still taking the auxiliary transformer with parameters shown in the above table as an example, the process of determining the maximum required capacity of the auxiliary transformer in the pair of auxiliary transformers when the pair of auxiliary transformers is running under load is described in detail:

[0181] Assuming that when an auxiliary transformer is operated alone with load, the steady-state current on the low-voltage side of the auxiliary transformer is 800A, the maximum value of the transient current on the low-voltage side of the auxiliary transformer does not exceed 1200A, the steady-state current on the high-voltage side of the auxiliary transformer is 580A, and the transient current on the high-voltage side of the auxiliary transformer is 850A. Therefore, when the pair of auxiliary transformers are operated with load, the steady-state current and transient current on the low-voltage side of the auxiliary transformer operating with load are shown in the following table:

[0182]

[0183] When the two auxiliary transformers in the pair of auxiliary transformers are running at the same time, the power factor of each auxiliary transformer is approximately equal to 1, that is, the power of each auxiliary transformer is active power. Therefore, the required capacity of the pair of auxiliary transformers is .

[0184] If we ignore the different short-circuit voltages of the two auxiliary transformers in the pair due to gear adjustment, we can consider that the two auxiliary transformers equally share the capacity of 38.84MVA, that is, the required capacity of each auxiliary transformer in the pair of auxiliary transformers is S21=S2÷2=19.42MVA.

[0185] When any of the auxiliary transformers in the pair of auxiliary transformers is operated alone with load, the power factor of the auxiliary transformer in the pair of auxiliary transformers is approximately equal to 1, that is, the power of the auxiliary transformer in the pair of auxiliary transformers is active power. Therefore, the required capacity of the auxiliary transformer in the pair of auxiliary transformers is .

[0186] Since when any auxiliary transformer in the pair of auxiliary transformers operates alone with load, the power of the auxiliary transformer in the pair of auxiliary transformers that is not operating with load is approximately zero, the maximum required capacity of the auxiliary transformer in the pair of auxiliary transformers is 24.50MVA at this time.

[0187] In summary, the maximum required capacity of the auxiliary transformer in the pair of auxiliary transformers when the pair of auxiliary transformers is operated under load is 24.50 MVA.

[0188] S830. Determine whether the sum of the required capacity and the maximum required capacity is greater than the rated capacity of the auxiliary transformer.

[0189] If the sum of the two required capacities determined is less than or equal to the rated capacity, step S840 is executed; if the sum of the two required capacities determined is greater than the rated capacity, step S850 is executed.

[0190] Continuing with the above example, the sum of the required capacity and the maximum required capacity S=S1+S3=8.9+24.50=33.4MVA. Therefore, the sum of the required capacity and the maximum required capacity is less than the rated capacity of the auxiliary transformer, 34MVA. Therefore, it is determined that the sum of the required capacity and the maximum required capacity is less than or equal to the rated capacity.

[0191] S840: Determine whether the pair of auxiliary transformers can operate under load while forming a circulating current.

[0192] S850: Determine that the pair of auxiliary transformers cannot operate under load while forming a circulating current.

[0193] The above is only a specific implementation of step S710. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances, all of which are within the scope of protection of this application.

[0194] Another embodiment of the present application provides an auxiliary power supply system, whose specific structure is as follows: Figure 1 ( Figure 1 As shown in the example of only three pairs of auxiliary transformers 20 and five first current transformers CT 30 , the system specifically includes: a bus tie switch Sm, two input busbars 10 , at least two pairs of auxiliary transformers 20 and at least five first current transformers CT 30 .

[0195] The connection relationship between the various components, the meaning of the two high-voltage sides of each pair of auxiliary transformers 20, the meaning of the two high-voltage sides of each pair of auxiliary transformers 20 being connected to the two input busbars 10 respectively, and the implementation method of the connection relationship of each pair of auxiliary transformers 20 on the low-voltage side have been described in detail above and will not be repeated here.

[0196] This embodiment also provides another implementation of the auxiliary power system. The specific structure can be found in Fig.13 ( Fig.13 Only four first selection switches Sx1 and five third current transformers CT 80 are used as an example for illustration). Based on the above embodiment, this embodiment further includes: at least four first selection switches Sx1 and at least five third current transformers CT80.

[0197] The high voltage side of each auxiliary transformer 20 is also connected to the unconnected input bus 10 via a first selection switch Sx1.

[0198] Assuming that the auxiliary power supply system includes three pairs of auxiliary transformers, and the high-voltage sides of the first auxiliary transformer, the third auxiliary transformer, and the fifth auxiliary transformer are all connected to the first input bus, and the high-voltage sides of the second auxiliary transformer, the fourth auxiliary transformer, and the sixth auxiliary transformer are all connected to the second input bus, then the high-voltage side of each auxiliary transformer is also connected to the input bus to which it is not connected through a first selection switch Sx1, specifically: the high-voltage side of the first auxiliary transformer is connected to the first input bus through the first selection switch Sx1 No. A, the high-voltage side of the third auxiliary transformer is connected to the first input bus through the first selection switch Sx1 No. B, the high-voltage side of the fifth auxiliary transformer is connected to the first input bus through the first selection switch Sx1 No. C, the high-voltage side of the second auxiliary transformer is connected to the second input bus through the first selection switch Sx1 No. D, the high-voltage side of the fourth auxiliary transformer is connected to the second input bus through the first selection switch Sx1 No. E, and the high-voltage side of the sixth auxiliary transformer is connected to the second input bus through the first selection switch Sx1 No. F.

[0199] The high voltage side of each auxiliary transformer 20 is also connected in series with the primary side of a third CT 80, the bus tie switch is also connected in series with the primary side of a third CT 80, and the secondary side of each third CT 80 is connected to the second bus differential protection device 05 in the power generation system corresponding to the auxiliary power supply system.

[0200] The above are only two implementation methods of the auxiliary power supply system. In practical applications, including but not limited to these, no specific limitations are made here and it can be determined according to specific circumstances, all of which are within the scope of protection of this application.

[0201] Another embodiment of the present application also provides another implementation of the auxiliary power system, and its specific structure is as follows: Fig.14 ( Fig.14 Only two output busbars 40 are taken as an example to illustrate the connection relationship of the tie switch SL, as shown in FIG. 1 , further comprising: at least two tie switches SL.

[0202] A tie switch SL is provided between the two low-voltage sides of each pair of auxiliary transformers 20 . In other words, a tie switch SL is provided between the two output busbars 40 connected to the two low-voltage sides of each pair of auxiliary transformers 20 .

[0203] Assuming that the two low-voltage sides of the first pair of auxiliary transformers are respectively connected to the first output bus and the second output bus, the two low-voltage sides of the second pair of auxiliary transformers are respectively connected to the third output bus and the fourth output bus, and the two low-voltage sides of the third pair of auxiliary transformers are respectively connected to the fifth output bus and the sixth output bus, then a connecting switch is provided between the two output busbars connected to the two low-voltage sides of each pair of auxiliary transformers. Specifically, the meaning is: a first connecting switch is provided between the first output bus and the second output bus, a second connecting switch is provided between the third output bus and the fourth output bus, and a third connecting switch is provided between the fifth output bus and the sixth output bus.

[0204] The above is only one implementation of the auxiliary power supply system. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances, all of which are within the scope of protection of this application.

[0205] Another embodiment of the present application provides another implementation of the auxiliary power system, and its specific structure can be found in Figure 4 ( Figure 4 Only one construction transformer 50 and three second CTs 60 are used as an example for illustration). Based on the above embodiment, this embodiment further includes: at least one construction transformer 50, at least three second CTs 60 and two power lines 70.

[0206] The two input busbars 10 are respectively connected to two power lines 70, and the two power lines draw power from two substations 03 respectively; each power line 70 is connected in series with the primary side of a second CT 60, and the high-voltage side of each construction transformer 50 is connected in series with the primary side of a second CT 60; the secondary side of each second CT 60 is connected to the first bus differential protection device 01.

[0207] This embodiment also provides another implementation of the auxiliary power system. The specific structure can be found in Fig.15 ( Fig.15 Only three second selection switches Sx2 and three fourth CTs 90 are used as an example for illustration). Based on the previous embodiment, this embodiment further includes: at least three second selection switches Sx2 and at least three fourth CTs 90 .

[0208] Each power extraction line 70 is also connected to the unconnected input bus 10 via a second selection switch Sx2.

[0209] Assuming that in the auxiliary power supply system, the first input bus is connected to the first power supply line, and the second input bus is connected to the second power supply line, then each power supply line is also connected to the input bus that is not connected to itself through a second selection switch. Specifically, the first power supply line is also connected to the second input bus through the second selection switch No. A, and the second power supply line is also connected to the first input bus through the second selection switch No. B.

[0210] The high voltage side of each construction transformer 50 is also connected to the unconnected input bus 10 via a second selection switch Sx2.

[0211] Assuming that the auxiliary power supply system includes two construction transformers, and the high-voltage sides of the two construction transformers are connected to the first input bus, the high-voltage side of each construction transformer is also connected to the input bus to which it is not connected through a second selection switch. Specifically, the high-voltage side of the first construction transformer is connected to the second input bus through the second selection switch No. C, and the high-voltage side of the second construction transformer is connected to the second input bus through the second selection switch No. D.

[0212] Each power supply line 70 is connected in series with the primary side of a fourth CT 90, the high voltage side of each construction transformer 50 is also connected in series with the primary side of a fourth CT 90, and the secondary side of each fourth CT 90 is connected to the second mother differential protection device 04 in the power generation system corresponding to the auxiliary power supply system.

[0213] The above are only two implementation methods of the auxiliary power supply system. In practical applications, including but not limited to these, no specific limitations are made here and it can be determined according to specific circumstances, all of which are within the scope of protection of this application.

[0214] For the above description of the disclosed embodiments, the features recorded in each embodiment in this specification can be replaced or combined with each other, so that professionals in the field can implement or use the present application. The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with a preferred embodiment, it is not used to limit the present invention. Any technician familiar with the field can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A CT polarity verification method for an auxiliary power system, characterized in that: The auxiliary power supply system comprises at least two pairs of auxiliary transformers, two input busbars and bus tie switches respectively connected to the two input busbars at both ends; The CT polarity verification method comprises: When the auxiliary power supply system is in a normal operating state, a circulating current is formed successively on the circuits where the bus tie switch and each pair of the auxiliary transformers are located; The two high-voltage sides of each pair of auxiliary transformers are respectively connected to the two input busbars; After each circulation current is formed, detecting the CT polarity relationship between the branches where the two auxiliary transformers forming the circulation current are located and the branch where the bus tie switch is located; Taking the bus tie switch as a reference, the CT polarity relationship between the branches where the auxiliary transformers are located is determined according to the CT polarity relationship between the branches where the auxiliary transformers are located and the branch where the bus tie switch is located.

2. The CT polarity verification method of the auxiliary power system according to claim 1, characterized in that: The loop current is formed successively on the loop where the bus tie switch and each pair of the auxiliary transformers are located, including: Closing the bus tie switch; gradually connecting the two low-voltage sides of each pair of auxiliary transformers; After the two low-voltage sides of a pair of the auxiliary transformers are connected each time, a voltage difference is generated between the pair of the auxiliary transformers whose two low-voltage sides are connected.

3. The CT polarity verification method of the auxiliary power system according to claim 2, characterized in that: A voltage difference is generated between a pair of auxiliary transformers whose two low-voltage sides are connected, including: The gear positions of the on-load tap changers of the pair of auxiliary transformers are adjusted so that there is a gear position difference between the gear positions of the on-load tap changers of the pair of auxiliary transformers.

4. The CT polarity verification method of the auxiliary power system according to claim 1, characterized in that: The current value of the circulating current formed each time is greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system.

5. The CT polarity verification method of the auxiliary power system according to any one of claims 1 to 4, characterized in that: The auxiliary power supply system includes at least one construction transformer and two power lines, the high-voltage sides of all the construction transformers are connected to the same input bus, and the two input busbars are respectively connected to two power lines; after detecting the CT polarity relationship between the branches where each auxiliary transformer is located and the branches where the bus tie switch is located, it also includes: When the auxiliary power supply system is in normal operation, closing the bus tie switch; Detect the CT polarity relationship between the branch where each of the construction transformers is located, the branch where the power line corresponding to the first target input bus is located, and the branch where the bus tie switch is located; the first target input bus is the input bus to which the construction transformer is not connected; Taking the bus tie switch as a reference, determine the CT polarity relationship between the branches where each construction transformer is located, the branches where the power lines corresponding to the first target input bus are located, and the branches where the bus tie switch is located, according to the CT polarity relationship between the branches where each construction transformer is located, the branches where the power lines corresponding to the first target input bus are located, and the branches where the auxiliary transformers are located.

6. The CT polarity verification method of the auxiliary power system according to claim 5, characterized in that: Before detecting the CT polarity relationship between the branch where each of the construction transformers is located, the branch where the power line corresponding to the first target input bus is located, and the branch where the bus tie switch is located, the method further includes: Disconnect the connection between the second target input bus and its corresponding power supply line; the second target input bus is the input bus connected to the construction transformer.

7. The CT polarity verification method of the auxiliary power system according to claim 5, characterized in that: After determining the CT polarity relationship among the branch where each of the construction transformers is located, the branch where the power line corresponding to the first target input bus is located, and the branch where each of the auxiliary transformers is located, the method further includes: When the auxiliary power supply system is in normal operation, the CT polarity relationship between the branch where the target construction transformer is located and the branch where the power-taking line corresponding to the second target input bus is located is detected; the second target input bus is the input bus connected to the construction transformer, and the target construction transformer includes at least one construction transformer; Taking the target construction transformer as a reference, determine the CT polarity relationship between the branch where the power line corresponding to the first target input bus is located and the branch where the power line corresponding to the second target input bus is located, based on the CT polarity relationship between the branch where the power line of the first target input bus is located, the branch where the power line of the second target input bus is located, and the branch where the target construction transformer is located.

8. The CT polarity verification method of the auxiliary power system according to claim 5, characterized in that: Before closing the bus tie switch, or before detecting the CT polarity relationship between the branch where each construction transformer is located, the branch where the power line corresponding to the first target input bus is located, and the branch where the bus tie switch is located, the method further includes: Adjust the load of at least one of the construction transformers so that the current of the second target input bus is greater than the minimum sampling current accuracy of any bus differential protection device in the power generation system corresponding to the auxiliary power supply system; the second target input bus is the input bus connected to the construction transformer.

9. The CT polarity verification method of the auxiliary power system according to any one of claims 1 to 4, characterized in that: Before forming a circulating current in the loops of the bus tie switch and each pair of the auxiliary transformers one by one, the method further includes: determining whether any pair of the auxiliary transformers can operate under load while forming a circulating current; If the pair of auxiliary transformers can operate under load while forming a circulating current, the steps of successively forming a circulating current on the bus tie switch and the loop where each pair of auxiliary transformers are located are performed.

10. The CT polarity verification method of the auxiliary power system according to claim 9, characterized in that: Determining whether any pair of the auxiliary transformers can operate under load while forming a circulating current comprises: determining a required capacity of the auxiliary transformer in the pair of auxiliary transformers when a circulating current is formed in the pair of auxiliary transformers; determining a maximum required capacity of the auxiliary transformer in the pair of the auxiliary transformers when the pair of the auxiliary transformers operates under load; Determining whether the sum of the required capacity and the maximum required capacity is greater than the rated capacity of the auxiliary transformer; If the sum of the required capacity and the maximum required capacity is less than or equal to the rated capacity, it is determined that the pair of auxiliary transformers can operate under load while forming a circulating current.

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