Transformer early fault monitoring method, device and equipment based on Tillegen theorem and medium

Abstract

The invention relates to the technical field of transformer on-line monitoring, in particular to a transformer early-stage fault monitoring method, device, equipment and medium based on the Tillegen theorem, and the method comprises the steps: deducing according to the Tillegen likelihood power theorem to obtain a likelihood power difference calculation model of branch connection admittance flowing through a transformer; drawing a similar power change curve of the short-circuit turns of the transformer and the branch connection conductance flowing through the internal fault; extracting voltage and current data in the current operation state for calculation to obtain a similar power difference value of the transformer in the current state and the normal state; comparing the similar power difference value with the similar power change curve, and judging the fault state and the development trend; the method comprises the following steps: deducing to obtain a similar active power variable quantity flowing through a branch connection admittance model when a transformer has a fault through a Teller-root similar power theorem, judging whether the fault occurs or not and the fault degree through similar active power difference value change characteristics, and solving the problem that an existing protection method of the transformer is difficult to identify under the conditions of a slight fault or winding deformation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer online monitoring, and in particular to a transformer early fault monitoring method, device, equipment and medium based on Tellegen's theorem. Background Art

[0002] The operational stability and reliability of power equipment are core elements of the development of the power system. Power equipment is not only the basis for ensuring power supply reliability, but also an important link in ensuring power safety.

[0003] With the increasing proportion of new energy in the power system and the application of a large number of nonlinear power electronic devices, the operating environment of the transformer has become more and more complex. Under the influence of large current impact or a large number of harmonics, the transformer is prone to early faults such as winding deformation and slight inter-turn short circuit. Such early faults are difficult to be detected by existing protection methods and have a significant accumulation effect. Therefore, there is an urgent need for an accurate, timely and effective fault diagnosis method to identify potential faults of the transformer, ensure its healthy and stable operation, and thus improve the overall stability of the power system.

[0004] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0005] The present invention provides a transformer early fault monitoring method, device, equipment and medium based on Tellegen's theorem, thereby effectively solving the problems in the background technology.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a transformer early fault monitoring method based on Tellegen's theorem, comprising the following steps:

[0007] S10: Based on Tellegen's quasi-power theorem, the quasi-power difference calculation model of the admittance flowing through the transformer branch is derived;

[0008] S20: Selecting data when the transformer is normal and when it has an internal fault and bringing them into the quasi-power difference calculation model to obtain a quasi-power change curve of the transformer short-circuit turns and the branch conductance when it has an internal fault;

[0009] S30: extracting the voltage and current data of the current operating state for calculation to obtain the difference in power between the transformer in the current state and the normal state;

[0010] S40: Compare the apparent power difference with the apparent power change curve to determine the fault state and development trend.

[0011] Further, in step S10, the selected transformer is represented by a T-type equivalent circuit, the system / load at both ends of the transformer is equivalent according to the Thevenin equivalent theorem, the equivalent circuit is drawn, and the equivalent circuit is converted into the form of branch admittance.

[0012] Further, in step S10, the quasi-power difference calculation model includes:

[0013]

[0014] Where, P is the apparent power difference; is the transformer excitation branch potential at time t0, is the transformer excitation branch potential at time t1, is the conductance of the branch at time t0, is the conductance of the branch at time t1, is the transformer primary voltage at time t0, is the transformer secondary voltage at time t0, is the transformer primary current at time t0, is the transformer secondary current at time t0, is the transformer primary voltage at time t1, is the transformer secondary voltage at time t1, is the transformer primary current at time t1, is the transformer secondary current at time t1.

[0015] Furthermore, the calculation model of the excitation branch potential includes:

[0016]

[0017] In the formula, is the transformer primary voltage at time t0, is the transformer secondary voltage at time t0, is the transformer primary current at time t0, is the transformer secondary current at time t0, Z1 is the equivalent impedance of the primary equivalent system, Z2' is the secondary impedance, is the transformer excitation current at time t0.

[0018] Further, in step S20, the data of the transformer in a normal state is selected and brought into the quasi-power difference calculation model, and the values ​​of the n inter-turn short-circuit rates are taken to obtain the quasi-active power change P at this time. k , where k = 1, 2, ... n, corresponding to n situations in turn, and the results are plotted as a quasi-power change curve.

[0019] Further, in step S30, the voltage and current data of the current operating state are extracted, and the quasi-power difference P of the current operating state of the transformer is obtained according to the quasi-power difference calculation model. c .

[0020] Furthermore, in step S40, the quasi-power difference of the previous operating state is compared with the quasi-power change curve to determine the fault state and development trend thereof, including:

[0021] Determine the power difference P of the current operating state c Satisfied: 0.9P k <P c <1.1P k , where P k is the pre-calculated power P of a certain turn-to-turn short-circuit ratio k ;

[0022] If so, it is determined that the transformer is working in the same k Under the corresponding state;

[0023] If not, compare P k <P c <P (k+1) ,k=1,2…n-1, where P1>P n , n is a positive integer greater than 1, find the corresponding state range.

[0024] Furthermore, in step S40, the fault state and development trend are determined. When it is determined that the transformer is in a turn-to-turn short-circuit state, an alarm is issued. If it is a serious turn-to-turn short-circuit, the circuit breaker can be directly tripped.

[0025] The present invention also includes a transformer early fault monitoring device based on Tellegen's theorem, using the above method, including:

[0026] A quasi-power difference calculation model unit is used to derive a quasi-power difference calculation model of the branch admittance flowing through the transformer according to Tellegen's quasi-power theorem;

[0027] The quasi-power variation curve unit selects data when the transformer is normal and when there is an internal fault and brings it into the quasi-power difference calculation model to obtain a quasi-power variation curve of the transformer short-circuit turns and the branch conductance flowing during the internal fault;

[0028] The current apparent power difference calculation unit is used to extract the voltage and current data of the current operating state for calculation to obtain the apparent power difference between the current state and the normal state of the transformer;

[0029] The comparison and judgment unit is used to compare the quasi-power difference with the quasi-power change curve to judge the fault state and development trend.

[0030] The present invention also includes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method described above is implemented.

[0031] The present invention also includes a storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described above is implemented.

[0032] The beneficial effects of the present invention are:

[0033] This method is based on the transformer T-type branch admittance model. The Tellegen quasi-power theorem is used to derive the change in the quasi-active power flowing through the branch admittance model when the transformer fails. The change characteristics of the quasi-active power difference are used to determine whether a fault has occurred and the extent of the fault. This method solves the problem that the existing transformer protection methods are difficult to identify in the case of minor faults or winding deformation. This method is simple and convenient to judge. It only needs to use existing electrical quantities, and can determine the quasi-power difference between any two states. It can detect the transformer fault state and its evolution process, and further improve the safety of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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 some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 This is a flow chart of a transformer early fault monitoring method based on Tellegen's theorem;

[0036] Figure 2 It is the transformer T-branch admittance equivalent circuit;

[0037] Figure 3 It is the transformer fault degree-conductance increment curve;

[0038] Figure 4 It is the conductivity increment result when a 2% inter-turn fault occurs in the transformer;

[0039] Figure 5 It is a structural diagram of a transformer early fault monitoring device based on Tellegen's theorem;

[0040] Figure 6 A schematic diagram of the structure of a computer device. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0042] Embodiment 1:

[0043] like Figure 1 As shown: A transformer early fault monitoring method based on Tellegen's theorem includes the following steps:

[0044] S10: Based on Tellegen's quasi-power theorem, the quasi-power difference calculation model of the admittance flowing through the transformer branch is derived;

[0045] S20: Select the data of the transformer in normal state and internal fault state and bring them into the quasi-power difference calculation model to obtain the quasi-power change curve of the transformer short-circuit turns and the branch conductance flowing during the internal fault state; this step provides a "reference curve" of the fault characteristics for comparison in subsequent judgments;

[0046] S30: extracting the voltage and current data of the current operating state for calculation, and obtaining the difference between the apparent power of the transformer in the current state and the normal state; this step calculates the apparent power change in the current state in real time, and provides real-time data support for judging the actual operating state of the transformer;

[0047] S40: Compare the apparent power difference with the apparent power change curve to determine the fault state and development trend. This step can determine the matching degree between the current state and the fault model through comparison, thereby determining whether a fault exists and the severity of the fault.

[0048] At present, the electrical quantity methods for detecting and identifying internal faults of power transformers mainly include short-circuit impedance method, low-voltage pulse method and frequency response method. In recent years, in order to realize online monitoring of transformer faults, some scholars have extended these methods into online methods. The online monitoring methods of transformer internal faults based on non-electrical quantities include dissolved gas analysis method, fault sound extraction method, etc.

[0049] Online detection methods for electrical quantities, such as the online short-circuit impedance method, the online frequency response method and the vibration detection method, all have certain shortcomings. The online short-circuit impedance method can diagnose early transformer faults according to the changing law of short-circuit reactance, but its implementation relies on high-precision measurement technology and data processing technology, and the short-circuit reactance changes are relatively simple and the diagnostic sensitivity is low; although the online frequency response method has been applied in related fields, its recognized disadvantage is that it lacks tools for fault quantification and is difficult to perform setting calculations. Fault judgment relies on the experience of operating personnel and requires high professional quality of personnel; and the vibration detection method is easily affected by factors such as sensor accuracy and on-site electromagnetic interference, and requires additional measuring elements in addition to the power frequency current and voltage measurement, which increases the difficulty of engineering implementation and is still in the theoretical development stage.

[0050] As for the non-electrical quantity detection methods, additional measuring equipment is required, and since temperature, sound and other signals are secondary quantities, it is difficult to achieve online real-time monitoring, and there is no strict quantitative relationship to reflect the severity of the fault.

[0051] Tellegen's theorem is a basic theorem that is universally applicable to circuits and has the same status as Kirchhoff's law. Tellegen's first theorem is essentially the conservation of energy in circuits, which is specifically explained as the sum of the power absorbed by all branches of any circuit is always zero. At present, Tellegen's first theorem has been studied and applied to power systems to a certain extent, such as energy differential protection and power differential protection. Among them, active power differential protection is used in busbar protection and transmission line protection as an auxiliary scheme for main protection or differential protection because it has the advantage of not being affected by the asynchronous data on both sides.

[0052] Tellegen's second theorem is also expressed as the sum of the power of the circuit and is not affected by the composition of the branch components. It is called the "quasi-power theorem" or "quasi-power theorem". The characteristic of Tellegen's quasi-power theorem is that its research object includes two circuits, and there is no need for there to be a practical connection between the two circuits. It can be different moments of a circuit or different circuits. This means that Tellegen's quasi-power theorem can be used to represent the state change of a circuit and the difference between two circuits. Therefore, Tellegen's quasi-power theorem has high flexibility. However, since the basic condition for Tellegen's quasi-power theorem to hold is that the topology of the two circuits is the same, this situation is relatively rare in actual power systems. Therefore, there are few reports on the results of the quasi-power theorem in the field of power system equipment monitoring and protection.

[0053] The present invention is based on the transformer T-type branch admittance equivalent circuit and Tellegen's quasi-power theorem, and proposes a transformer early fault monitoring method based on Tellegen's quasi-power theorem. This method extracts electrical quantities in normal state and early fault state, calculates and analyzes the difference between the two states through Tellegen's quasi-power theorem, and combines the change characteristics of branch admittance in the transformer T-type equivalent circuit during fault to judge the current state of the transformer. This method does not require the addition of any measuring equipment, and can monitor the operating state of the transformer online and predict its fault development state, effectively improving the operating safety of the transformer, and has broad application prospects in the field of online monitoring of transformers.

[0054] This method is based on the transformer T-type branch admittance model. The Tellegen quasi-power theorem is used to derive the change in quasi-active power flowing through the branch admittance model when the transformer fails. The change characteristics of the quasi-active power difference are used to determine whether a fault has occurred and the extent of the fault. This solves the problem that the existing transformer protection methods are difficult to identify in the case of minor faults or winding deformation. This method is simple and convenient to judge. It only needs to use existing electrical quantities, and can determine the quasi-power difference between any two states. The transformer fault state and its evolution process are detected, further improving the safety of the transformer.

[0055] One of the core points of the present invention is to derive a calculation formula for the quasi-power difference flowing through the transformer branch admittance by theoretical deduction, and the measured change in quasi-active power is the core parameter for judging the severity of the fault.

[0056] The second core point of the present invention is to draw a relationship diagram between the number of short-circuit turns of the transformer and the change in the apparent power difference flowing through the transformer branch admittance based on simulation. When the transformer has different degrees of early faults, the magnitude of the apparent power flowing through the transformer branch admittance will also change. Through prior testing or collecting data during operation, it is also possible to draw a trend diagram of the apparent active power change under different fault degrees, providing a basis for subsequent online monitoring.

[0057] The third core point of the present invention is to use the data collected during the operation of the transformer to calculate and obtain the quasi-power difference of the branch admittance flowing through the transformer, correspond to the calculated curve, and judge the current operating state of the transformer.

[0058] Among them, in step S10, the selected transformer is represented by a T-type equivalent circuit, and the system / load at both ends of the transformer is equivalent according to the Thevenin equivalence theorem, then the equivalent circuit is drawn, and the equivalent circuit is converted into the form of branch admittance. Specifically, the model takes into account the potential, resistance and leakage impedance of the primary and secondary sides of the transformer, and can simulate the electrical characteristics of the transformer more accurately. It performs calculations and analyses based on existing electrical quantities (such as voltage and current) without the need for additional measuring equipment. This not only reduces the complexity and cost of engineering implementation, but also avoids errors or failures caused by factors such as equipment installation or environmental interference, thereby improving the stability and reliability of the system.

[0059] In this embodiment, in step S10, the quasi-power model of the transformer at the time t0 of normal operation and the time t1 of early fault occurrence (taking turn-to-turn short circuit as an example) is listed according to Tellegen's quasi-power theorem, including:

[0060]

[0061] In the formula, is the transformer primary voltage at time t0, is the transformer secondary voltage at time t0, is the transformer excitation branch potential at time t0, is the transformer primary current at time t0, is the transformer secondary current at time t0, is the transformer excitation current at time t0; is the transformer primary voltage at time t1, is the transformer secondary voltage at time t1, is the transformer excitation branch potential at time t1, is the transformer primary current at time t1, is the transformer secondary current at time t1, is the transformer excitation current at time t1.

[0062] Subtracting the two equations in the model, we can get:

[0063]

[0064] Therefore, the difference in apparent power flowing through the transformer excitation branch at two moments can be expressed by the voltage and current on the primary and secondary sides, which can be converted into:

[0065]

[0066] Also because

[0067] I m =E·(G T +jBT );

[0068] In the formula, G T is the conductance of the branch, B T is the branch susceptance, and E is the branch potential.

[0069] Transform the above model into:

[0070]

[0071] In the formula, is the conductance of the branch at time t0, is the susceptance of the branch at time t0; is the conductance of the branch at time t1, is the susceptance of the branch at time t1.

[0072] The left side of the above model is divided into two parts: real part and imaginary part, where:

[0073] Real part It is the apparent power on the conductance, recorded as P, called the apparent active power, that is, the apparent power difference. When the transformer has an internal fault such as a turn-to-turn short circuit, the branch conductance G of its equivalent circuit T changes, the more serious the short circuit, G T The larger the value of P is, the larger the value of P is. Regardless of whether the transformer is in the case of excitation inrush current or external fault, as long as there is no fault inside the transformer, the branch conductance G T unchanged, so the value of P is 0; therefore, by the change in the value of P, it is possible to determine whether the transformer has an internal fault and the severity of the fault, and it is not affected by working conditions such as excitation inrush current and external faults.

[0074] As a preference of the above embodiment, in step S10, the power difference calculation model includes:

[0075]

[0076] Where, P is the apparent power difference; is the transformer excitation branch potential at time t0, is the transformer excitation branch potential at time t1, is the conductance of the branch at time t0, is the conductance of the branch at time t1, is the transformer primary voltage at time t0, is the transformer secondary voltage at time t0, is the transformer primary current at time t0, is the transformer secondary current at time t0, is the transformer primary voltage at time t1, is the transformer secondary voltage at time t1, is the transformer primary current at time t1, is the transformer secondary current at time t1.

[0077] This method can effectively evaluate the severity of the internal fault of the transformer by calculating the change of the quasi-power difference P. When the transformer has internal faults such as inter-turn short circuit, the value of the quasi-power difference P increases with the severity of the fault. This quantitative fault assessment method helps operation and maintenance personnel quickly judge the severity of the fault and take corresponding measures to avoid further deterioration of the fault.

[0078] Among them, the calculation model of the excitation branch potential includes:

[0079]

[0080] In the formula, is the transformer primary voltage at time t0, is the transformer secondary voltage at time t0, is the transformer primary current at time t0, is the transformer secondary current at time t0, Z1 is the equivalent impedance of the primary equivalent system, Z2' is the secondary impedance, is the transformer excitation current at time t0.

[0081] By providing a calculation model for the excitation branch voltage, this method can more accurately calculate the excitation branch voltage of the transformer under different operating conditions. The model takes into account factors such as the voltage, current and equivalent impedance on the primary and secondary sides, ensuring the accuracy and reliability of the calculation results. This provides a solid foundation for further analyzing the working status of the transformer and judging faults.

[0082] In this embodiment, in step S20, the data of the transformer when it is normal is selected and brought into the quasi-power difference calculation model, and the values ​​of n inter-turn short-circuit rates are taken to obtain the quasi-active power change P at this time. k , where k = 1, 2, ... n, corresponding to n situations in turn, and the results are plotted as a quasi-power change curve.

[0083] This method calculates the quasi-power difference under different turn-to-turn short-circuit rates and establishes a quasi-power change curve model related to the degree of internal fault. This model can sensitively detect turn-to-turn short-circuit faults at an early stage, and because the curve can provide reference values ​​under multiple states, its detection accuracy and reliability are significantly enhanced. Especially in the early stage, subtle changes in turn-to-turn short-circuit can also be effectively captured through the changing trend of the curve.

[0084] Among them, in step S30, the voltage and current data of the current operating state are extracted, and the quasi-power difference value P of the current operating state of the transformer is obtained according to the quasi-power difference calculation model. c .

[0085] By extracting the voltage and current data of the current operating state of the transformer and using the quasi-power difference calculation model to calculate the current quasi-power difference P in real time c , which can realize real-time monitoring of the transformer status. This real-time monitoring can quickly capture any subtle abnormal changes inside the transformer, thereby improving the sensitivity and timeliness of fault detection.

[0086] As a preferred embodiment of the above, in step S40, the apparent power difference of the previous operation state is compared with the apparent power change curve to determine the fault state and development trend thereof, including:

[0087] Determine the power difference P of the current operating state c Satisfied: 0.9P k <P c <1.1P k , where P k is the pre-calculated power P of a certain turn-to-turn short-circuit ratio k ;

[0088] If so, it is determined that the transformer is working in the same k Under the corresponding state;

[0089] If not, compare P k <P c <P (k+1) ,k=1,2…n-1, where P1>P n , n is a positive integer greater than 1, find the corresponding state range.

[0090] By taking the power difference P of the current operating state c The pre-calculated power variation curve P k By comparing, the current fault state of the transformer can be accurately determined. Specifically, by determining P c Whether the apparent active power change of a certain turn-to-turn short-circuit rate is satisfied 0.9P k <P c <1.1P k , can directly identify that the transformer is in a specific short-circuit state. This method makes fault judgment more accurate and can provide accurate equipment status information for operation and maintenance personnel.

[0091] This method can not only determine the current fault state, but also cSimilar power changes with multiple turn-to-turn short-circuit rates (P1, P2, P3...P n ) to identify the development trend of the fault. If P c Does not meet the specific power change condition 0.9P k <P c <1.1P k , then by further comparing and finding the corresponding state range, it is possible to effectively identify whether the fault is deteriorating or stabilizing, thereby predicting the evolution trend of the fault in advance.

[0092] In this embodiment, in step S40, the fault state and development trend are determined. When it is determined that the transformer is in a turn-to-turn short circuit state, an alarm is issued. If it is a serious turn-to-turn short circuit, the circuit breaker may be tripped directly.

[0093] When the monitoring system determines that the transformer is in a turn-to-turn short-circuit state, the system will immediately send out an alarm signal. The timely alarm mechanism enables the operation and maintenance personnel to quickly understand the abnormal condition of the equipment and take corresponding inspection and repair measures to effectively prevent the fault from further deteriorating and avoid transformer damage or more serious power grid accidents. If the monitoring system further determines that the transformer has a serious turn-to-turn short-circuit (for example, the short-circuit rate reaches a certain critical value), the system will automatically trigger a tripping operation. This automated control mechanism can immediately cut off the connection between the faulty transformer and the power grid without human intervention, preventing the fault from spreading to other equipment or causing a larger power outage, thereby ensuring the safety and stable operation of the entire power grid.

[0094] The present invention is based on Tellegen's quasi-power theorem. The core point is to obtain the quasi-power difference of the branch admittance flowing through the transformer through the calculation method of Tellegen's quasi-power theorem, which is the basis of this method; by collecting data under various internal faults of the transformer for calculation, and making a fault development curve, a basis is provided for judging what kind of fault it is.

[0095] Aiming at the problem that the internal fault state of the transformer is difficult to detect, the present invention proposes a novel transformer early fault monitoring method based on Tellegen's theorem, which can solve the problem that the current transformer online detection method needs to install additional equipment and is difficult to monitor in real time, and reduce the losses caused by the early fault of the transformer that is difficult to detect and develops into a serious fault. The benefits brought by the present invention are significant, as detailed as follows:

[0096] ① The proposed method introduces Tellegen's quasi-power theorem into the field of transformer online monitoring. The Tellegen's quasi-power theorem is used to calculate the difference in quasi-active power between two operating states of the transformer, which can represent the internal fault of the transformer and its development state, and monitor the transformer in real time. In addition, since the voltage and current at any two moments can be used for calculation, the method has strong flexibility.

[0097] ② Compared with differential current protection, the proposed method is not affected by excitation surge current and has a wider protection range. It does not require additional measuring equipment and uses the collected voltage and current for calculation. It can monitor phase failure without other operations and has broad application prospects.

[0098] ③When the transformer has an early fault, the change in conductivity is very small, which affects the accuracy of the calculation. Therefore, it is difficult to directly use the current and voltage after the fault to calculate the branch conductivity for fault judgment. The proposed method can select a state with a large difference in power from the current state (such as an external fault state) for calculation, amplify the fault characteristics, and make the judgment more sensitive.

[0099] ④The proposed scheme is a universally applicable method and can be used in various transformers.

[0100] Embodiment 2:

[0101] Take the most common three-phase three-column transformer as an example:

[0102] Step 1: Use a T-type equivalent circuit to represent the selected transformer, and equate the system / load at both ends of the transformer according to the Thevenin equivalence theorem, then draw the equivalent circuit as shown below: Figure 2 As shown in the figure and Z1 are the power supply potential and equivalent impedance of the primary side equivalent system, and Z'2 are the secondary side potential and impedance, Z1, Z'2, Z T It is the primary side, secondary side leakage impedance and excitation branch impedance parameters in the transformer T-type equivalent circuit. Change the equivalent circuit and convert it into the form of branch admittance, such as Figure 2 As shown, G T With B T Represents the conductance and susceptance of the branch.

[0103] Step 2: Select the time t0 of normal operation and the time t1 of early transformer failure (taking turn-to-turn short circuit as an example), with the same topology circuit in both cases; write the quasi-power equations at the two times according to Tellegen's quasi-power theorem, and use phasors to represent the quasi-power.

[0104]

[0105] In the formula, is the transformer primary voltage at time t0, is the transformer secondary voltage at time t0, is the transformer excitation branch potential at time t0, is the transformer primary current at time t0, is the transformer secondary current at time t0, is the transformer excitation current at time t0; is the transformer primary voltage at time t1, is the transformer secondary voltage at time t1, is the transformer excitation branch potential at time t1, is the transformer primary current at time t1, is the transformer secondary current at time t1, is the transformer excitation current at time t1.

[0106] Subtracting the two equations in equation (1), we can get:

[0107]

[0108] Therefore, the difference in the apparent power flowing through the transformer excitation branch at two moments can be expressed by the voltage and current on the primary and secondary sides, which is given by equation (3).

[0109]

[0110] Also because

[0111] I m =E·(G T +jB T ); (4)

[0112] In the formula, G T is the conductance of the branch, B T is the branch susceptance, and E is the branch potential.

[0113] The following formula (5) can be obtained:

[0114]

[0115] The left side of equation (5) is divided into two parts: the real part and the imaginary part, where:

[0116] Real part It is the quasi-power on the conductance, recorded as P, called the quasi-active power. When the transformer has an internal fault such as a turn-to-turn short circuit, the branch conductance G of the equivalent circuit T changes, the more serious the short circuit, G T The larger the value of P is, the larger the value of P is. Regardless of whether the transformer is in the case of excitation inrush current or external fault, as long as there is no fault inside the transformer, the branch conductance G T unchanged, so the value of P is 0. Therefore, by the change of the value of P, it is possible to determine whether the transformer has an internal fault and the severity of the fault, and it is not affected by working conditions such as excitation inrush current and external faults.

[0117] According to formula (5), the calculation formula of P can be obtained as follows:

[0118]

[0119] Where, P is the apparent power difference; is the transformer excitation branch potential at time t0, is the transformer excitation branch potential at time t1, is the conductance of the branch at time t0, is the conductance of the branch at time t1, is the transformer primary voltage at time t0, is the transformer secondary voltage at time t0, is the transformer primary current at time t0, is the transformer secondary current at time t0, is the transformer primary voltage at time t1, is the transformer secondary voltage at time t1, is the transformer primary current at time t1, is the transformer secondary current at time t1.

[0120] Among them, the calculation method of the excitation branch potential E is as follows:

[0121]

[0122] In the formula, is the transformer primary voltage at time t0, is the transformer secondary voltage at time t0, is the transformer primary current at time t0, is the transformer secondary current at time t0, Z1 is the equivalent impedance of the primary equivalent system, Z2' is the secondary impedance, is the transformer excitation current at time t0.

[0123] Step 3: Select the data when the transformer is normal and when it has an internal fault, and substitute them into equation (6) in step 2 to obtain the apparent active power difference flowing through the excitation branch at this time. Based on the results of the calculation points, draw a relationship diagram between the fault degree and the apparent active power change. The more points selected, the more complete the curve.

[0124] Select normal, turn-to-turn short circuit 0.1%, turn-to-turn short circuit 0.3%, turn-to-turn short circuit 0.4%, turn-to-turn short circuit 0.5%, turn-to-turn short circuit 1.0%, turn-to-turn short circuit 1.5%, turn-to-turn short circuit 2.0%, and get the apparent active power change P at this time respectively. k , where k = 1, 2, ... 7, corresponding to the above 7 cases. The obtained results are plotted into a curve, such as Figure 3 .

[0125] Step 4: Extract the voltage and current data of the current operating state, and substitute it into the formula in step 2 to calculate the apparent active power P1 of the transformer at this moment. Take the data when the inter-turn short circuit is 2%, and substitute it into the formula in step 2 to calculate, and we get Figure 4 , in the figure, P1=15.9446W.

[0126] Step 5: Compare P1 with P k Compare, if 0.9P is satisfied k <P1<1.1P k , then it is determined that the transformer is working in the same k Under the corresponding state, 0.9P7<P1<1.1P7, it is judged that the transformer state is 2% turn-to-turn short circuit.

[0127] Step 6: If P1 does not meet the conditions of step 5, compare P k <P1<P (k+1) ,k=1,2…6,P1>P7, find the corresponding state range.

[0128] Step 7: Determine the operating status of the transformer. When it is determined that the transformer is in a turn-to-turn short-circuit state, an alarm is issued. If it is a serious turn-to-turn short-circuit, the circuit breaker can be tripped directly.

[0129] The present invention also includes a transformer early fault monitoring device based on Tellegen's theorem, such as Figure 5 As shown, using the method as described above, including:

[0130] A quasi-power difference calculation model unit is used to derive a quasi-power difference calculation model of the branch admittance flowing through the transformer according to Tellegen's quasi-power theorem;

[0131] The quasi-power variation curve unit selects the data of the transformer in normal state and internal fault state and brings them into the quasi-power difference calculation model to obtain the quasi-power variation curve of the transformer short-circuit turns and the branch conductance flowing through the internal fault state;

[0132] The current apparent power difference calculation unit is used to extract the voltage and current data of the current operating state for calculation to obtain the apparent power difference between the current state and the normal state of the transformer;

[0133] The comparison and judgment unit is used to compare the apparent power difference with the apparent power change curve to judge its fault state and development trend.

[0134] See also Figure 6 A computer device 400 provided in an embodiment of the present application includes: a processor 410 and a memory 420, wherein the memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, the above method is executed.

[0135] The embodiment of the present application further provides a storage medium 430 on which a computer program is stored. When the computer program is run by the processor 410, the above method is executed.

[0136] Among them, the storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable red-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, disk or optical disk.

[0137] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0138] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0139] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0140] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0141] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0142] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0143] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0144] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A transformer early fault monitoring method based on Tellegen's theorem, characterized in that: The steps include: S10: Based on Tellegen's quasi-power theorem, the quasi-power difference calculation model of the admittance flowing through the transformer branch is derived; S20: Selecting data when the transformer is normal and when it has an internal fault and bringing them into the quasi-power difference calculation model to obtain a quasi-power change curve of the transformer short-circuit turns and the branch conductance when it has an internal fault; S30: extracting the voltage and current data of the current operating state for calculation to obtain the difference in power between the transformer in the current state and the normal state; S40: Compare the apparent power difference with the apparent power change curve to determine the fault state and development trend.

2. The transformer early fault monitoring method based on Tellegen's theorem according to claim 1 is characterized in that: In step S10, the selected transformer is represented by a T-type equivalent circuit, the system / load at both ends of the transformer is equivalent according to the Thevenin equivalent theorem, the equivalent circuit is drawn, and the equivalent circuit is converted into the form of branch admittance.

3. The transformer early fault monitoring method based on Tellegen's theorem according to claim 1 is characterized in that: In step S10, the quasi-power difference calculation model includes: Where, P is the apparent power difference; is the transformer excitation branch potential at time t0, is the transformer excitation branch potential at time t1, is the conductance of the branch at time t0, is the conductance of the branch at time t1, is the transformer primary voltage at time t0, is the transformer secondary voltage at time t0, is the transformer primary current at time t0, is the transformer secondary current at time t0, is the transformer primary voltage at time t1, is the transformer secondary voltage at time t1, is the transformer primary current at time t1, is the transformer secondary current at time t1.

4. The transformer early fault monitoring method based on Tellegen's theorem according to claim 3 is characterized in that: The calculation model of the excitation branch potential includes: In the formula, is the transformer primary voltage at time t0, is the transformer secondary voltage at time t0, is the transformer primary current at time t0, is the transformer secondary current at time t0, Z1 is the equivalent impedance of the primary equivalent system, Z2' is the secondary impedance, is the transformer excitation current at time t0.

5. The transformer early fault monitoring method based on Tellegen's theorem according to claim 1 is characterized in that: In step S20, the data of the normal transformer is selected and brought into the quasi-power difference calculation model, and the values ​​of n inter-turn short-circuit rates are taken to obtain the quasi-active power change P at this time. k , where k = 1, 2, ... n, corresponding to n situations in turn, and the results are plotted as a quasi-power change curve.

6. The transformer early fault monitoring method based on Tellegen's theorem according to claim 1 is characterized in that: In step S30, the voltage and current data of the current operating state are extracted, and the quasi-power difference P of the current operating state of the transformer is obtained according to the quasi-power difference calculation model. c .

7. The transformer early fault monitoring method based on Tellegen's theorem according to claim 1 is characterized in that: In step S40, the apparent power difference of the previous operating state is compared with the apparent power change curve to determine the fault state and development trend thereof, including: Determine the power difference P of the current operating state c Satisfied: 0.9P k <P c <1.1P k , where P k is the pre-calculated power P of a certain turn-to-turn short-circuit ratio k ; If so, it is determined that the transformer is working in the same k Under the corresponding state; If not, compare P k <P c <P (k+1) ,k=1,2…n-1, where P1>P n , n is a positive integer greater than 1, find the corresponding state range.

8. The transformer early fault monitoring method based on Tellegen's theorem according to claim 1 is characterized in that: In step S40, the fault status and development trend are determined. When it is determined that the transformer is in a turn-to-turn short circuit state, an alarm is issued. If it is a serious turn-to-turn short circuit, a direct trip can be performed.

9. A transformer early fault monitoring device based on Tellegen's theorem, characterized in that: Use of the method according to any one of claims 1 to 8, comprising: A quasi-power difference calculation model unit is used to derive a quasi-power difference calculation model of the branch admittance flowing through the transformer according to Tellegen's quasi-power theorem; The quasi-power variation curve unit selects data when the transformer is normal and when there is an internal fault and brings it into the quasi-power difference calculation model to obtain a quasi-power variation curve of the transformer short-circuit turns and the branch conductance flowing during the internal fault; The current apparent power difference calculation unit is used to extract the voltage and current data of the current operating state for calculation to obtain the apparent power difference between the current state and the normal state of the transformer; The comparison and judgment unit is used to compare the quasi-power difference with the quasi-power change curve to judge the fault state and development trend.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 8 is implemented.

11. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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