Method and device for judging secondary disconnection of current transformer of transformer
By obtaining the current data on the high, medium and low voltage side of the transformer and using the zero-sequence current of the low voltage side triangular winding as a criterion, combined with the delay mechanism, the accuracy of the secondary circuit breaking detection of the current transformer in the prior art is solved, the recognition accuracy is improved and misoperation is avoided, and the safety and stability of the power system are enhanced.
Patent Information
- Application Number
- CN202510362000.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-26
- Publication Date
- 2025-07-18
AI Technical Summary
In the prior art, when detecting the secondary circuit of the current transformer is disconnected, the accuracy and reliability are insufficient. Especially in complex faults, it is difficult to distinguish between primary equipment failure and current transformer secondary circuit of the current transformer, which is easy to lead to misjudgment or misjudgment.
By obtaining the current data on the high, medium and low voltage sides of the transformer, especially introducing the zero-sequence current of the triangular winding on the low voltage side as a criterion, the amplitude and phase relationship of the current are analyzed, and combined with the delay mechanism, the primary and secondary circuit breakers are accurately distinguished.
It improves the recognition accuracy of the secondary line disconnection of the current transformer, avoids protection malfunctions, and enhances the safety and stability of the power system.
Smart Images
Figure CN120334801A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of transformer condition monitoring, and particularly to a method and device for discriminating secondary open-circuit of a transformer current transformer. Background Art
[0002] In a power system, a current transformer (CT) is one of the important devices for measurement and protection. It scales down the current in a high-voltage system to a safe level for use by measurement and protection devices. However, when a current transformer fails, especially when there is an open-circuit in the secondary circuit, it may lead to serious consequences, such as misjudgment of transformer differential protection and zero-sequence overcurrent protection, and even serious accidents such as transformer explosion.
[0003] Traditional protection devices usually rely on differential current judgment logic to detect secondary open-circuit of current transformers. This method mainly identifies abnormal conditions by comparing the current differences flowing into and out of each side of the transformer. However, this method has limited ability to distinguish between high-resistance grounding faults and current transformer abnormalities. Another common strategy is to use the zero-sequence current on this side to detect secondary open-circuit of current transformers. However, this logic also faces challenges, especially in complex fault situations, such as accurately distinguishing between primary equipment fault open-circuit and secondary circuit open-circuit of current transformers.
[0004] The reliability and accuracy of existing detection means are limited in the face of complex power grid environments and changing operating conditions, and it is easy to have misjudgment or missed judgment. Summary of the Invention
[0005] In view of this, it is necessary to provide a method and system for discriminating secondary open-circuit of a transformer current transformer to solve the disadvantage of low accuracy in discriminating secondary open-circuit in the prior art.
[0006] A method for discriminating secondary open-circuit of a transformer current transformer includes: N1: Obtain the secondary current data of the high and medium voltage sides of the transformer, and the zero-sequence current data of the low voltage side delta winding; N2: Analyze the secondary current data of the high and medium voltage sides of the transformer: If the currents on the high and medium voltage sides of the transformer do not meet the preset current range, it is preliminarily determined that an open-circuit fault has occurred; If the amplitudes and phases of the in-phase currents on the high and medium voltage sides of the transformer do not conform to the winding connection relationship and turn ratio relationship of the transformer, it is preliminarily determined that there is a primary open-circuit or a secondary circuit open-circuit of the current transformer; N3: Conduct zero-sequence current analysis of the low voltage side delta winding: If zero-sequence current is generated in the low voltage side delta winding, it is determined that a primary open-circuit fault has occurred on the high and medium voltage sides; If no zero-sequence current is generated in the low voltage side bushing, it is determined that the secondary circuit of the current transformer is open-circuited.
[0007] Preferably, when the transformer is operating normally, the normal ranges of the high- and medium-voltage side currents satisfy: I 0.H ≤0.06I n.H ，I 2.H ≤0.06I n.H ; I 0.M ≤I n.M ，I 2.M ≤0.06I n.M ; where, I 0.H Zero-sequence current of the high-voltage side; I 2.H Secondary current of the high-voltage side; I n.H is the current of a certain phase on the high-voltage side; I 0.M is the zero-sequence current of the medium-voltage side; I 2.M is the secondary current of the medium-voltage side; I n.M is the current of a certain phase on the medium-voltage side; When the high- and medium-voltage side currents do not conform to the normal ranges of the high- and medium-voltage side currents and remain for a preset duration, a disconnection fault is initially judged to have occurred.
[0008] Preferably, if the zero-sequence current of the low-voltage side delta winding satisfies the normal range of the zero-sequence current of the low-voltage side delta winding: 3I 0.L ≤3I 0.set , then it is determined that the secondary circuit of the current transformer is disconnected; where, 3I 0.L is the zero-sequence current of the low-voltage side delta winding, 3I 0.set is the setting value of the zero-sequence current of the low-voltage side delta winding; If the zero-sequence current of the low-voltage side delta winding does not conform to the normal range of the zero-sequence current of the low-voltage side delta winding, then it is determined that a primary disconnection fault has occurred on the high- and medium-voltage sides.
[0009] Preferably, after it is determined that the secondary circuit of the current transformer is disconnected, the secondary circuit disconnection protection of the current transformer is started after a preset delay.
[0010] Preferably, according to the maximum unbalanced zero-sequence current value during the normal operation of the transformer, the setting value of the zero-sequence current of the low-voltage side delta winding is set.
[0011] Preferably, after determining that the secondary circuit of the current transformer is open-circuited, the protection for the open-circuit of the secondary circuit of the current transformer is started after a preset delay.
[0012] Preferably, an alarm signal is sent out when it is determined that the secondary circuits of the current transformers on the high-voltage and medium-voltage sides are open-circuited.
[0013] A device for discriminating the open-circuit of the secondary of a transformer current transformer includes: A data acquisition module, configured to obtain the secondary current data of the high-voltage and medium-voltage sides of the transformer, as well as the zero-sequence current data of the delta winding on the low-voltage side; A high- and medium-voltage side analysis module, configured to analyze the secondary current data of the high-voltage and medium-voltage sides of the transformer: if the currents on the high-voltage and medium-voltage sides of the transformer do not conform to the preset current range, it is initially determined that a breakage fault has occurred; if the amplitudes and phases of the currents of the same phase on the high-voltage and medium-voltage sides of the transformer do not conform to the winding connection relationship and the turns ratio relationship of the transformer, it is initially determined that there is a primary breakage or an open-circuit of the secondary circuit of the current transformer; A low-voltage side analysis module, configured to perform zero-sequence current analysis on the delta winding on the low-voltage side: if zero-sequence current is generated in the delta winding on the low-voltage side, it is determined that a primary breakage has occurred on the high-voltage and medium-voltage sides; if zero-sequence current is not generated in the low-voltage side bushing, it is determined that the secondary circuit of the current transformer is open-circuited.
[0014] Preferably, a blocking module is configured to start the protection for the open-circuit of the secondary circuit of the current transformer after a preset delay after determining that the secondary circuit of the current transformer is open-circuited.
[0015] Preferably, it further includes: an alarm module, configured to send out an alarm signal when it is determined that the secondary circuits of the current transformers on the high-voltage and medium-voltage sides are open-circuited.
[0016] Compared with the prior art, the beneficial effects of the present application are as follows: The zero-sequence current of the delta winding on the low-voltage side is introduced as a criterion. By analyzing the current data of the high-voltage, medium-voltage, and low-voltage sides of the transformer, the recognition accuracy of the open-circuit of the secondary of the current transformer is improved. It can not only effectively distinguish the cases of breakage on the high-voltage and medium-voltage sides and the open-circuit of the secondary circuit of the current transformer, but also avoid the misoperation of the protection caused by the open-circuit of the secondary of the current transformer, thereby enhancing the safety and stability of the entire power device. Description of the Drawings
[0017] Figure 1 It is a schematic flowchart of a method for discriminating the open-circuit of the secondary of a transformer current transformer provided by an embodiment of the present application.
[0018] Figure 2 It is a schematic flowchart of a method for discriminating the open-circuit of the secondary of a transformer current transformer provided by another embodiment of the present application.
[0019] Figure 3It is a schematic structural diagram of a secondary open - circuit discrimination device 300 for a transformer current transformer provided by an embodiment of the present application. Detailed implementation manners
[0020] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0021] The explanations and definitions of some terms in the present application are as follows: Zero - sequence current ( 3I 0 ) : When an asymmetrical fault (such as a single - phase grounding fault) occurs in the power system, a zero - sequence component of current will appear. The zero - sequence current is the sum of the three - phase currents. Under normal conditions, due to the three - phase balance, this sum should be zero; however, in the case of asymmetrical faults or other specific conditions, the three - phase currents are no longer balanced, resulting in the appearance of zero - sequence current.
[0022] Maximum unbalanced zero - sequence current: Under normal operating conditions, due to load imbalance, slight asymmetry, or other non - fault factors, there may be a certain zero - sequence current. This current is called "unbalanced zero - sequence current", and under certain operating conditions, this imbalance may reach a maximum value, that is, the maximum unbalanced zero - sequence current.
[0023] Setting: Setting refers to the process of setting the action parameters of a protection device according to the actual operating conditions and protection requirements. For zero - sequence current protection, it is to determine a suitable action threshold value to ensure that the protection action is triggered only when a real fault occurs, rather than due to normal unbalanced states.
[0024] Please refer to Figure 1 , Figure 1 It is a schematic flowchart of a method for discriminating secondary open - circuit of a transformer current transformer provided by an embodiment of the present application. The method for discriminating secondary open - circuit of a transformer current transformer includes the following steps: N1: Obtain the secondary current data of the high - voltage and medium - voltage sides of the transformer, as well as the zero - sequence current data of the low - voltage side delta winding.
[0025] Collect current data from the high - voltage, medium - voltage, and low - voltage sides of the transformer, including the phase currents of the high - voltage and medium - voltage sides of the transformer and the zero - sequence current data of the low - voltage side delta winding.
[0026] N2: Analyze the secondary current data of the high - voltage and medium - voltage sides of the transformer.
[0027] Specifically, it may include checking for situations such as sudden changes in current and imbalance of three-phase currents, and comparing whether the current amplitude and phase conform to the expected relationship.
[0028] If the sudden change in current of the high and medium voltage sides of the transformer is less than the preset current value, it is preliminarily determined that a disconnection fault has occurred. That is, under normal operating conditions, the currents on each side of the transformer should be balanced. If the current of a certain phase suddenly decreases significantly or becomes zero, it may indicate that a disconnection fault has occurred in that phase.
[0029] If the amplitude and phase of the same-phase currents on the high and medium voltage sides of the transformer do not conform to the winding connection relationship and turns ratio relationship of the transformer, it is preliminarily determined that there is a primary disconnection or a secondary circuit disconnection of the current transformer. During normal operation, the amplitude and phase of the same-phase currents on each side should conform to the winding connection relationship and turns ratio relationship of the transformer. If this relationship is violated, it may indicate the existence of a primary disconnection or a problem in the secondary circuit of the current transformer.
[0030] The "disconnection fault" herein mainly refers to the situation where the current of a certain phase on the high and medium voltage sides of the transformer decreases significantly or approaches zero, which usually means that there may be a physical disconnection in that phase, such as a wire break or a loose connection. "Primary disconnection" specifically refers to a disconnection fault occurring in the primary equipment (such as cables, busbars, switches, etc.) on the high voltage side or medium voltage side of the transformer. This kind of fault not only causes current changes but also destroys the balance relationship between the three-phase currents. By comparing the amplitude and phase of the same-phase currents, if it is found that they do not conform to the winding connection relationship and turns ratio relationship of the transformer, it is preliminarily determined that there is a primary disconnection or a problem in the secondary circuit of the current transformer.
[0031] N3: Analyze the zero-sequence current of the low-voltage side delta winding.
[0032] If zero-sequence current is generated in the low-voltage side delta winding, it is determined that a primary disconnection fault has occurred on the high and medium voltage sides; if no zero-sequence current is generated in the low-voltage side bushing, it is determined that the secondary circuit of the current transformer is disconnected.
[0033] The traditional differential current judgment logic and the logic of the zero-sequence current transformer disconnection on the same side are difficult to correctly distinguish high-resistance grounding and current transformer anomalies, and cannot effectively distinguish between primary equipment fault disconnection and secondary circuit disconnection of the current transformer. The solution provided in the embodiments of the present application can more accurately distinguish whether there is a primary disconnection on the high and medium voltage sides by introducing the zero-sequence current information of the low-voltage side delta winding. Specifically, when a primary phase disconnection fault occurs on the high and medium voltage sides, the low-voltage side delta winding will generate zero-sequence current; while in the case of a secondary disconnection of the high and medium voltage side current transformers, the low-voltage side delta winding will not generate zero-sequence current; therefore, this feature can be used to effectively judge the secondary disconnection of the current transformer.
[0034] Further, please refer to Figure 2 ,Figure 2 It is a schematic flow chart of a method for discriminating secondary open circuit of a transformer current transformer provided by another embodiment of the present application.
[0035] When the transformer is operating normally, the normal ranges of the high-voltage and medium-voltage side currents satisfy: I 0.H ≤0.06I n.H ，I 2.H ≤0.06I n.H ; I 0.M ≤I n.M ，I 2.M ≤0.06I n.M ; where, I 0.H is the zero-sequence current of the high-voltage side; I 2.H is the secondary current of the high-voltage side; I n.H is the current of a certain phase on the high-voltage side; I 0.M is the zero-sequence current of the medium-voltage side; I 2.M is the secondary current of the medium-voltage side; I n.M is the current of a certain phase on the medium-voltage side; If the high-voltage and medium-voltage side currents do not conform to the normal ranges of the high-voltage and medium-voltage side currents and remain for a preset duration, a disconnection fault is initially judged. Specifically, when the transformer is operating normally, it is usually expected that the zero-sequence current is very small or even close to zero because the three-phase system is theoretically balanced and does not generate significant zero-sequence components. However, in actual operation, due to factors such as load imbalance and slight asymmetry, there may be a small amount of zero-sequence current. In this embodiment, according to the specific situation of the power grid and the requirements of the protection device, 0.06I n.H and 0.06I n.M are used as setting values to filter out normal unbalanced currents to distinguish between the normal operating state and the fault state and avoid misjudging as a fault due to these small fluctuations. That is to say, for example, I 0.H ≤0.06I n.H , it is considered that the system is in a normal operating state or there is only a slight imbalance, and the protection action is not triggered. It should be noted that the setting of the above setting values is an exemplary illustration in this embodiment and can be modified and set as needed in practice.
[0036] If it exceeds the set value and remains for a preset duration, it indicates that there may be an asymmetric fault in the system (such as single-phase grounding fault, primary open circuit, etc.). In this case, further analysis is required and corresponding protection measures should be taken. Among them, there are various transient phenomena in the power system, such as lightning strikes, switch operations, etc. These can all cause abnormal current signals in a short period. If the judgment of maintaining the preset duration is not set, these short-term interferences may be misjudged as CT open circuit, thus wrongly blocking the protection device. By setting a judgment (delay) of maintaining a certain preset duration, it can be ensured that only when a CT open circuit actually occurs will the protection be blocked, rather than being caused by transient interferences.
[0037] In some cases, especially when a short-circuit fault occurs, the current transformer may record very high current values. In this case, it may also show phenomena similar to CT open circuit. If the protection is blocked immediately, it may lead to the failure to handle the actual serious fault in a timely manner. By setting a delay, the system can be given enough time to distinguish whether it is a real CT open circuit or a short-circuit fault and take corresponding measures.
[0038] Adopting the above delay mechanism allows the protection system to have time to confirm the authenticity of the CT open circuit and reduces unnecessary protection blocking caused by misjudgment. This helps to improve the reliability and stability of the entire protection system and ensures that the protection is blocked only when it is truly necessary.
[0039] In addition, according to different grid operation regulations and standards, there may be different requirements for the operating time and response speed of the protection device. Appropriately setting the delay can ensure that the operation of the protection device complies with relevant regulations and standards, and at the same time can cooperate with other protection devices to optimize the overall protection strategy.
[0040] Furthermore, if the zero-sequence current of the low-voltage side delta winding meets the normal range of the zero-sequence current of the low-voltage side delta winding: 3I 0.L ≤3I 0.set , it is determined that the secondary circuit of the current transformer is open; where 3I 0.L is the zero-sequence current of the low-voltage side delta winding, 3I 0.set is the setting value of the zero-sequence current of the low-voltage side delta winding; If the zero-sequence current of the low-voltage side delta winding does not meet the normal range of the zero-sequence current of the low-voltage side delta winding, it is determined that a primary open circuit fault occurs in the high- and medium-voltage sides.
[0041] Under normal operating conditions, due to the balance of three-phase currents, theoretically, no zero-sequence current should be generated. However, in actual operation, due to load imbalance, slight asymmetry, or other non-fault factors, there may be a small amount of zero-sequence current. The zero-sequence current setting value ( 3I 0.set ) is usually set slightly higher than the maximum unbalanced zero-sequence current value that may occur during normal operation to ensure that the protection device will not be mis-triggered under normal conditions. If the zero-sequence current of the low-voltage side delta winding is less than or equal to 3I 0.set , it means that there is no significant asymmetry fault (such as single-phase ground fault) or primary open-circuit condition in the system. At this time, it can be considered that the transformer and its related circuits are in a healthy state and no additional protection measures are required.
[0042] If the zero-sequence current of the low-voltage side delta winding is less than or equal to 3I 0.set , the possibility of a primary open-circuit in the high- and medium-voltage sides can be excluded. Because when a primary open-circuit occurs in the high- and medium-voltage sides, an obvious zero-sequence current will be generated on the low-voltage side, exceeding the set value, and it can be further confirmed that it is a problem with the secondary circuit of the current transformer rather than a primary equipment fault.
[0043] Furthermore, after determining the disconnection of the secondary circuit of the current transformer, the disconnection protection of the secondary circuit of the current transformer is started after a preset delay. Without an appropriate delay mechanism, the protection device may be frequently blocked due to short-term current fluctuations, which not only affects the normal operation of the system but also may lead to unnecessary maintenance work. In this embodiment, by setting a certain duration requirement, unnecessary protection blocking can be reduced to ensure that actions are taken only when a fault actually exists.
[0044] For example, I 0.H >0.06I n.H maintain for 3 seconds, and this delay can be adjusted according to specific circumstances in actual applications. For example, in some occasions with high requirements for response speed, a shorter delay may be selected; while in other occasions, a longer delay may be selected to more conservatively judge faults.
[0045] Furthermore, after the current exceeds the setting value and maintains the preset time, multiple levels of protection measures can also be combined to act together. For example, when a fault is detected, continue with another delay, such as 0.1 second, and then perform the CT disconnection protection action; in addition, fast protection can also be selected according to the situation, that is, immediately perform the CT disconnection protection when a serious fault is detected.
[0046] Furthermore, in the case of confirming the disconnection of the secondary circuit of the current transformer, the system shall issue an alarm signal and block the relevant protection functions to prevent the misoperation of the protection caused by the disconnection of the secondary circuit of the current transformer.
[0047] In addition, according to specific circumstances, it may be necessary to isolate the fault area through an automatic control system or manual intervention. For example, relevant switches connected to the fault phase can be disconnected to prevent the fault from spreading to other parts. Start the standby power supply or switch the load to maintain power supply continuity and minimize the impact on users. The standby power supply can be quickly started or the critical load can be switched to other normally operating power paths. Adjust the operating parameters, such as redistributing the load and adjusting the voltage level, to maintain the stable operation of the entire power grid. At the same time, once the specific location and nature of the fault are determined, professional personnel should be organized as soon as possible for rapid fault repair, etc.
[0048] In summary, this application analyzes the current data on the high, medium, and low voltage sides of the transformer and introduces the data of the delta winding on the low voltage side as an additional criterion to improve the recognition accuracy of the disconnection of the secondary circuit of the current transformer. It can not only effectively distinguish the disconnection of the primary circuit on the high and medium voltage sides and the disconnection of the secondary circuit of the current transformer, but also avoid the misoperation of the protection caused by the disconnection of the secondary circuit of the current transformer, thereby enhancing the safety and stability of the entire power system.
[0049] Based on the same inventive concept, this application also provides a discriminator 300 for the disconnection of the secondary circuit of the transformer current transformer, as Figure 3 shown in the structural schematic diagram of the discriminator 300 for the disconnection of the secondary circuit of the transformer current transformer, including: A data acquisition module 301 for acquiring the secondary current data on the high and medium voltage sides of the transformer and the zero-sequence current data of the delta winding on the low voltage side; A high and medium voltage side analysis module 302 for analyzing the secondary current data on the high and medium voltage sides of the transformer: if the currents on the high and medium voltage sides of the transformer do not meet the preset current range, a disconnection fault is initially judged; if the amplitudes and phases of the currents in the same phase on the high and medium voltage sides of the transformer do not conform to the winding connection relationship and transformation ratio relationship of the transformer, a primary disconnection or a disconnection of the secondary circuit of the current transformer is initially judged; A low voltage side analysis module 303 for performing zero-sequence current analysis on the delta winding on the low voltage side: if zero-sequence current is generated in the delta winding on the low voltage side, it is determined that a primary disconnection has occurred on the high and medium voltage sides; if zero-sequence current is not generated in the low voltage side bushing, it is determined that the secondary circuit of the current transformer is disconnected.
[0050] Furthermore, it further includes a blocking module 304 for blocking the protection for the disconnection of the secondary circuit of the current transformer after a preset delay after determining the disconnection of the secondary circuit of the current transformer.
[0051] An alarm module 305 is used to determine when the secondary windings of the high- and medium-voltage side current transformers are open-circuited and issue an alarm signal.
[0052] For the specific implementation manners of the various functional modules of the transformer current transformer secondary open-circuit discrimination device 300 in the above embodiments, reference may be made to the descriptions in the above embodiments of the transformer current transformer secondary open-circuit discrimination method, and details thereof will not be repeated in this embodiment.
Claims
1. A method for discriminating secondary open circuit of a transformer current transformer, characterized in that, Including: N1: Obtain the secondary current data of the high-voltage and medium-voltage sides of the transformer, and the zero-sequence current data of the delta winding on the low-voltage side; N2: Analyze the secondary current data of the high-voltage and medium-voltage sides of the transformer: If the currents on the high-voltage and medium-voltage sides of the transformer do not conform to the preset current range, it is preliminarily judged that a disconnection fault has occurred; If the amplitudes and phases of the in-phase currents on the high-voltage and medium-voltage sides of the transformer do not conform to the winding connection relationship and turns ratio relationship of the transformer, it is preliminarily judged that there is a primary disconnection or a secondary circuit disconnection of the current transformer; N3: Conduct zero-sequence current analysis of the delta winding on the low-voltage side: If zero-sequence current is generated in the delta winding on the low-voltage side, it is determined that a primary disconnection has occurred on the high-voltage and medium-voltage sides; If no zero-sequence current is generated in the low-voltage side bushing, it is determined that the secondary circuit of the current transformer is disconnected.
2. The method for discriminating the secondary open circuit of a transformer current transformer according to claim 1, characterized in that When the transformer is operating normally, the normal current range of the high-voltage and medium-voltage sides satisfies: I 0.H ≤0.06I n.H ，I 2.H ≤0.06I n.H ； I 0.M ≤I n.M ，I 2.M ≤0.06I n.M ； Among them, I 0.H is the zero-sequence current on the high-voltage side; I 2.H is the secondary current on the high-voltage side; I n.H is the current of a certain phase on the high-voltage side; I 0.M is the zero-sequence current on the medium-voltage side; I 2.M is the secondary current on the medium-voltage side; I n.M is the current of a certain phase on the medium-voltage side; If the currents on the high-voltage and medium-voltage sides do not conform to the normal current range of the high-voltage and medium-voltage sides and remain for a preset duration, it is preliminarily judged that a disconnection fault has occurred.
3. The method for discriminating the secondary open circuit of a transformer current transformer according to claim 2, characterized in that, Including: If the zero-sequence current of the low-voltage side delta winding conforms to the normal range of the zero-sequence current of the low-voltage side delta winding: 3I 0.L ≤ 3I 0.set , then it is determined that the secondary circuit of the current transformer is open; where 3I 0.L is the zero-sequence current of the low-voltage side delta winding, 3I 0.set is the setting value of the zero-sequence current of the low-voltage side delta winding. If the zero-sequence current of the delta winding on the low-voltage side does not conform to the normal zero-sequence current range of the delta winding on the low-voltage side, it is determined that a primary disconnection fault has occurred on the high-voltage and medium-voltage sides.
4. The method for discriminating the secondary open circuit of a transformer current transformer according to claim 3, wherein, Also including: After determining that the secondary circuit of the current transformer is disconnected, start the secondary circuit disconnection protection of the current transformer after a preset delay.
5. The method for discriminating the secondary open circuit of a transformer current transformer according to claim 3, wherein Including: Set the zero-sequence current setting of the delta winding on the low-voltage side according to the maximum unbalanced zero-sequence current value when the transformer is operating normally.
6. The method for discriminating the secondary open circuit of a transformer current transformer according to claim 1, wherein Including: Send an alarm signal when it is determined that the secondary of the high-voltage and medium-voltage side current transformers is disconnected.
7. A discriminator for secondary open circuit of transformer current transformer, characterized in that, Including: A data acquisition module for obtaining the secondary current data of the high-voltage and medium-voltage sides of the transformer and the zero-sequence current data of the delta winding on the low-voltage side; A high- and medium-voltage side analysis module for analyzing the secondary current data of the high-voltage and medium-voltage sides of the transformer: If the currents on the high-voltage and medium-voltage sides of the transformer do not conform to the preset current range, it is preliminarily judged that a disconnection fault has occurred; If the amplitudes and phases of the in-phase currents on the high-voltage and medium-voltage sides of the transformer do not conform to the winding connection relationship and turns ratio relationship of the transformer, it is preliminarily judged that there is a primary disconnection or a secondary circuit disconnection of the current transformer; A low-voltage side analysis module for conducting zero-sequence current analysis of the delta winding on the low-voltage side: If zero-sequence current is generated in the delta winding on the low-voltage side, it is determined that a primary disconnection has occurred on the high-voltage and medium-voltage sides; If no zero-sequence current is generated in the low-voltage side bushing, it is determined that the secondary circuit of the current transformer is disconnected.
8. The transformer current transformer secondary open circuit discrimination device according to claim 7, characterized in that, Including: A blocking module for blocking the secondary circuit disconnection protection of the current transformer after a preset delay after determining that the secondary circuit of the current transformer is disconnected.
9. The transformer current transformer secondary open circuit discrimination device according to claim 8, characterized in that, Also including: An alarm module for sending an alarm signal when it is determined that the secondary of the high-voltage and medium-voltage side current transformers is disconnected.