Power transformer complex impedance parameter synchronous vector online monitoring method and device

Abstract

The embodiment of the invention discloses a power transformer complex impedance parameter synchronous vector online monitoring method and device, and the method comprises the steps: synchronously collecting a first positive-sequence phase voltage vector and a first positive-sequence line current vector of a first winding of a to-be-detected power transformer at an inlet, and a second positive-sequence phase voltage vector and a second positive-sequence line current vector of a second winding at an outlet; a third positive-sequence phase voltage vector and a third positive-sequence line current vector of the first winding at the outlet and the third winding at the outlet are reduced to the reference winding, and then the steps are executed again under the condition that it is detected that the voltage or current of any side of the power transformer to be detected changes. Determining the first winding complex impedance of the first winding, the second winding complex impedance of the second winding and the third winding complex impedance of the third winding, and determining the excitation complex impedance of the power transformer to be tested; the complex impedance parameter is calculated by synchronously collecting the positive sequence vector variables before and after the change of the voltage or the current in real time, so that the problems in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer parameter monitoring, and particularly to a method and device for online monitoring of synchronous vectors of complex impedance parameters of an AC power transformer and a commutation power transformer. Background Art

[0002] As a key device in the power grid, the safe operation of power transformers has always been a key concern in the power industry. As one of the components with more faults, the transformer winding poses a major challenge to the stable operation of the power grid. According to investigations, more than 20% of large transformers in the power system that have been subjected to large current shocks have experienced winding deformation. Further data reveals that in the cases of unplanned outages of transformers above 220 kV in China, the outage time due to winding problems accounts for a significant proportion: up to 79.49% in 220 kV transformers and even up to 98.92% in 500 kV transformers. The mechanical deformation of the winding under the action of electrodynamic force has become a serious problem accounting for up to 70% of the total winding accidents. Obviously, the winding faults of power transformers pose a great threat to the safe operation of the power grid.

[0003] To address this challenge, it has become an essential requirement for building a new energy system and a new power system to understand the operating state of transformers in real time and prevent sudden major equipment failures and power grid accidents. From an external perspective, the requirements of the people and the economic society for power supply are increasing day by day, and the pressure on national safety supervision and power supply reliability assessment is also constantly increasing. From an internal perspective, power enterprises face problems such as high power grid operation risks and mismatches between equipment scale and maintenance capabilities during transformer maintenance. The risk of the equipment asset wall is becoming increasingly prominent, and the maintenance work is about to enter a peak period.

[0004] In the management of the safe operation of transformers, every link from type tests before the commissioning of new products to regular maintenance and online monitoring during operation is crucial. These inspection methods can generally be divided into two categories: one is the inspection after the transformer stops operating, and the other is the online monitoring during the operation of the transformer. As the objects to be inspected of the transformer, they are generally divided into three categories: complex impedance parameters, oil quality, and internal partial discharge. These objects to be inspected correspond to different parameters inside the transformer respectively and cannot replace each other. However, power-off inspections not only cause huge economic losses to the power grid but are also not suitable for frequent implementation in actual operations; while gas-in-oil and partial discharge detections are susceptible to interference and have complex criteria, and also face many difficulties in engineering practice.

[0005] At present, the power industry urgently needs a monitoring method that is highly reliable, easy to implement and economical to operate. Especially for winding faults, which account for the largest proportion of transformer faults, the short-circuit complex impedance test of the transformer before it is connected to the grid has become a recognized mandatory inspection content. The National Quality Inspection Center stipulates that the short-circuit complex impedance change range of the tested transformer is within 5% to be qualified.

[0006] However, the existing methods for measuring transformer complex impedance parameters are all power-off inspections, such as the frequency response method, the short-circuit complex impedance method, the high-voltage self-excited oscillation method proposed by Yunnan Electric Power Research Institute, and the traditional method for measuring the no-load and short-circuit characteristics of the transformer. In addition, the traditional method for measuring the no-load and short-circuit characteristics of the transformer is also limited by the test conditions, which undoubtedly brings huge hidden dangers to the stable operation of the power grid.

[0007] In this context, real-time online monitoring of the complex impedance parameters of power transformers has become a technical problem that needs to be solved urgently. The patent "Online Real-time Identification Device and Method for Power Transformer Winding Parameters (CN101261297B)" discloses the online identification of winding complex impedance (i.e., short-circuit complex impedance of winding) by recursive least squares method, but this method cannot truly realize real-time online monitoring in actual application, and the calculated winding complex impedance parameters also have the problem of large errors.

[0008] In addition, although the existing online monitoring method of mechanical vibration can realize the qualitative judgment of the change of transformer compression force, so that the operating status of the power transformer can be monitored online in real time, the threshold of mechanical vibration evaluation is difficult to determine.

[0009] Therefore, how to monitor the complex impedance parameters of the transformer in real time online without power outage so that the operating status of the power transformer can be monitored in real time online based on the complex impedance parameters and risk assessment can be performed is a technical problem that needs to be solved urgently. Summary of the invention

[0010] Based on this, it is necessary to propose a method and device for online monitoring of the complex impedance parameters of power transformers by synchronous vector in order to solve the above problems. The complex impedance parameters of AC transformers and converter transformers are calculated online by real-time synchronous acquisition of positive sequence vector variables before and after voltage or current changes, so as to solve the problems existing in the prior art.

[0011] To achieve the above object, the present invention provides, in a first aspect, a method for online monitoring of complex impedance parameters of a power transformer by synchronous vectors, the method comprising:

[0012] Synchronously collect the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding of the power transformer to be measured, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding;

[0013] Successively reduce the first positive-sequence phase voltage vector, the first positive-sequence line current vector, the second positive-sequence phase voltage vector, the second positive-sequence line current vector, the third positive-sequence phase voltage vector and the third positive-sequence line current vector to the reference winding to obtain the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence phase voltage vector and the third reduced positive-sequence line current vector, where the reference winding is any one of the first winding, the second winding and the third winding;

[0014] In the case where the voltage or current on any side of the power transformer to be measured changes, return to execute the step of synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding of the power transformer to be measured, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding, so as to obtain the changed first reduced positive-sequence phase voltage vector, the changed first reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed second reduced positive-sequence line current vector, the changed third reduced positive-sequence phase voltage vector and the changed third reduced positive-sequence line current vector;

[0015] Obtain the equivalent circuit of the transformer excitation complex impedance branch at the neutral point, and determine the first winding complex impedance of the first winding, the second winding complex impedance of the second winding, the third winding complex impedance of the third winding and the excitation complex impedance of the power transformer to be measured according to the first reduced positive-sequence phase voltage, the first reduced positive-sequence line current, the second reduced positive-sequence phase voltage, the second reduced positive-sequence line current, the third reduced positive-sequence phase voltage, the third reduced positive-sequence line current, the changed first reduced positive-sequence phase voltage, the changed first reduced positive-sequence line current, the changed second reduced positive-sequence phase voltage, the changed second reduced positive-sequence line current, the changed third reduced positive-sequence phase voltage and the changed third reduced positive-sequence line current; the winding complex impedance is the short-circuit complex impedance.

[0016] Optionally, the step of successively reducing the first positive-sequence phase voltage vector, the first positive-sequence line current vector, the second positive-sequence phase voltage vector, the second positive-sequence line current vector, the third positive-sequence phase voltage vector, and the third positive-sequence line current vector to a reference winding to obtain a first reduced positive-sequence phase voltage vector, a first reduced positive-sequence line current vector, a second reduced positive-sequence phase voltage vector, a second reduced positive-sequence line current vector, a third reduced positive-sequence phase voltage vector, and a third reduced positive-sequence line current vector includes:

[0017] Using the formula to determine the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence phase voltage vector, and the third reduced positive-sequence line current vector;

[0018] wherein, when i = 1, is the first reduced positive-sequence phase voltage vector, k Bi is the rated voltage ratio between the reference winding and the first winding, is the first positive-sequence phase voltage vector, e is the natural constant, j is the imaginary unit, is the angle by which the reference winding leads the first winding, is the first reduced positive-sequence line current vector, is the first positive-sequence line current vector; when i = 2, is the second reduced positive-sequence phase voltage vector, k Bi is the rated voltage ratio between the reference winding and the second winding, is the second positive-sequence phase voltage vector, is the angle by which the reference winding leads the second winding, is the second reduced positive-sequence line current vector, is the second positive-sequence line current vector; when i = 3, is the third reduced positive-sequence phase voltage vector, k Bi is the rated voltage ratio between the reference winding and the third winding, is the third positive-sequence phase voltage vector, is the angle by which the reference winding leads the third winding, is the third reduced positive-sequence line current vector, is the third positive-sequence line current vector.

[0019] Optionally, obtain the equivalent circuit of the transformer exciting complex impedance branch at the neutral point. According to the first reduced positive-sequence phase voltage, the first reduced positive-sequence line current, the second reduced positive-sequence phase voltage, the second reduced positive-sequence line current, the third reduced positive-sequence phase voltage, the third reduced positive-sequence line current, the changed first reduced positive-sequence phase voltage, the changed first reduced positive-sequence line current, the changed second reduced positive-sequence phase voltage, the changed second reduced positive-sequence line current, the changed third reduced positive-sequence phase voltage, and the changed third reduced positive-sequence line current, determine the first winding complex impedance of the first winding, the second winding complex impedance of the second winding, the third winding complex impedance of the third winding, and the exciting complex impedance of the power transformer under test, including:

[0020] Obtain the equivalent circuit of the transformer exciting complex impedance branch at the neutral point. According to the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence line current vector, the first winding complex impedance of the first winding, and the exciting complex impedance of the power transformer under test, write the first equation;

[0021] According to the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the third reduced positive-sequence line current vector, the second winding complex impedance of the second winding, and the exciting complex impedance of the power transformer under test, write the second equation;

[0022] According to the second reduced positive-sequence phase voltage vector, the third reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the third reduced positive-sequence phase voltage vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding, write the third equation;

[0023] Obtain the equivalent circuit of the transformer exciting complex impedance branch at the neutral point. According to the changed first reduced positive-sequence phase voltage vector, the changed first reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed second reduced positive-sequence line current vector, the changed third reduced positive-sequence line current vector, the first winding complex impedance of the first winding, and the exciting complex impedance of the power transformer under test, write the fourth equation;

[0024] According to the changed first reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed third reduced positive-sequence line current vector, the second winding complex impedance of the second winding, and the exciting complex impedance of the power transformer under test, write the fifth equation;

[0025] Based on the changed second reduced positive-sequence phase voltage vector, the changed third reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed third reduced positive-sequence phase voltage vector, the complex impedance of the second winding of the second winding, and the complex impedance of the third winding of the third winding, write the sixth equation;

[0026] Take the first equation, the second equation, the third equation, and the fourth equation to form a system of equations, or take the first equation, the second equation, the fifth equation, and the sixth equation to form a system of equations, or take the third equation, the fourth equation, the fifth equation, and the sixth equation to form a system of equations, or take the first equation, the third equation, the fourth equation, and the fifth equation to form a system of equations, or take the second equation, the fourth equation, the fifth equation, and the sixth equation to form a system of equations, and solve for the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding, and the exciting complex impedance of the power transformer to be measured.

[0027] Optionally, the first equation is

[0028] The second equation is

[0029] The third equation is

[0030] The fourth equation is

[0031] The fifth equation is

[0032] The sixth equation is

[0033] Where Z1 is the complex impedance of the first winding, Z2 is the complex impedance of the second winding, Z3 is the complex impedance of the third winding, Z m is the exciting complex impedance, is the first reduced positive-sequence phase voltage vector; is the changed first reduced positive-sequence phase voltage vector; is the second reduced positive-sequence phase voltage vector; is the changed second reduced positive-sequence phase voltage vector; is the third reduced positive-sequence phase voltage vector; is the changed third reduced positive-sequence phase voltage vector; is the first reduced positive-sequence line current vector; is the changed first reduced positive-sequence line current vector; is the second reduced positive-sequence line current vector; is the changed second reduced positive-sequence line current vector; is the 3rd reduced positive-sequence line current vector; is the changed 3rd reduced positive-sequence line current vector.

[0034] Optionally, the method further includes:

[0035] Determine the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer under test according to the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding, and the exciting complex impedance.

[0036] Optionally, the determining the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer under test according to the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding, and the exciting complex impedance includes:

[0037] Using the formula to determine the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer under test;

[0038] where P ij is the load loss between the i-th winding and the j-th winding of the power transformer under test, with the unit of kW, real() is the real part extraction function, Z i is the value of the i-th winding complex impedance calculated by reducing it from the reference winding to the nameplate parameters, Z j is the value of the j-th winding complex impedance calculated by reducing it from the reference winding to the nameplate parameters, S N is the rated capacity of the power transformer under test, with the unit of kVA, U N is the rated voltage of the high-voltage winding of the transformer, with the unit of kV, U ij % is the impedance voltage percentage between the i-th winding and the j-th winding of the power transformer under test, imag() is the imaginary part extraction function, P0 is the no-load loss, with the unit of kW, and I0% is the no-load current percentage.

[0039] Optionally, the method further includes:

[0040] Determine whether there is an abnormality in the power transformer under test according to the comparison results between the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding and the corresponding reference complex impedance thresholds; and / or,

[0041] Determine whether there is an abnormality in the power transformer under test according to the comparison results between the load loss, impedance voltage percentage, no-load loss, no-load current percentage of the power transformer under test and the corresponding load loss threshold, impedance voltage percentage threshold, no-load loss threshold, no-load current percentage threshold.

[0042] Optionally, synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding of the power transformer to be measured, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding includes:

[0043] Synchronously collecting the first three-phase voltage and the second three-phase current at the inlet of the first winding, the second three-phase voltage and the second three-phase current at the outlet of the second winding, and the third three-phase voltage and the third three-phase current at the outlet of the third winding;

[0044] Determining the first positive-sequence phase voltage vector and the first positive-sequence line current vector according to the first three-phase voltage and the first three-phase current, determining the second positive-sequence phase voltage vector and the second positive-sequence line current vector according to the second three-phase voltage and the second three-phase current, and determining the third positive-sequence phase voltage vector and the third positive-sequence line current vector according to the third three-phase voltage and the third three-phase current.

[0045] To achieve the above object, in a second aspect, the present invention provides an on-line monitoring device for synchronous vectors of complex impedance parameters of a power transformer, and the device includes a sensor module and a controller;

[0046] The sensor module is connected to the controller;

[0047] The sensor module is used to be respectively connected to the three phases at the inlet of the first winding of the power transformer to be measured, the three phases at the outlet of the second winding, and the three phases at the outlet of the third winding, and is used to measure the first three-phase voltage and the second three-phase current at the inlet of the first winding, the second three-phase voltage and the second three-phase current at the outlet of the second winding, and the third three-phase voltage and the third three-phase current at the outlet of the third winding;

[0048] The controller is used to synchronously collect the first three-phase voltage, the first three-phase current, the second three-phase voltage, the second three-phase current, the third three-phase voltage and the third three-phase current, so as to synchronously collect the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding, and execute the method according to any one of the first aspect.

[0049] Optionally, the sensor module includes a first voltage sensor, a second voltage sensor, a third voltage sensor, a first current sensor, a second current sensor and a third current sensor;

[0050] The first voltage sensor and the first current sensor are used to be respectively connected to the three-phase connection of the first winding at the inlet, and to measure the first three-phase voltage and the first three-phase current;

[0051] The second voltage sensor and the second current sensor are used to be respectively connected to the three-phase connection of the second winding at the outlet, and to measure the second three-phase voltage and the second three-phase current;

[0052] The third voltage sensor and the third current sensor are used to be respectively connected to the three-phase connection of the third winding at the outlet, and to measure the third three-phase voltage and the third three-phase current.

[0053] To achieve the above object, in a third aspect, the present invention provides a computer-readable storage medium storing a computer program, which when executed by a controller causes the controller to execute the method according to any one of the first aspect.

[0054] To achieve the above object, in a fourth aspect, the present invention provides a computer device including a memory and a controller, the memory storing a computer program, which when executed by the controller causes the controller to execute the method according to any one of the first aspect.

[0055] By adopting the embodiment of the present invention, the following beneficial effects are achieved: synchronously collect the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding of the power transformer to be measured, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding; sequentially reduce the first positive-sequence phase voltage vector, the first positive-sequence line current vector, the second positive-sequence phase voltage vector, the second positive-sequence line current vector, the third positive-sequence phase voltage vector and the third positive-sequence line current vector to the reference winding to obtain the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence phase voltage vector and the third reduced positive-sequence line current vector, where the reference winding is any one of the first winding, the second winding and the third winding; in the case where the voltage or current on any side of the power transformer to be measured changes, return to execute the step of synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding of the power transformer to be measured, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding, so as to obtain the changed first reduced positive-sequence phase voltage vector, the changed first reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed second reduced positive-sequence line current vector, the changed third reduced positive-sequence phase voltage vector and the changed third reduced positive-sequence line current vector; obtain the equivalent circuit of the transformer exciting complex impedance branch at the neutral point, and determine the first winding complex impedance of the first winding, the second winding complex impedance of the second winding, the third winding complex impedance of the third winding and the exciting complex impedance of the power transformer to be measured according to the first reduced positive-sequence phase voltage, the first reduced positive-sequence line current, the second reduced positive-sequence phase voltage, the second reduced positive-sequence line current, the third reduced positive-sequence phase voltage, the third reduced positive-sequence line current, the changed first reduced positive-sequence phase voltage, the changed first reduced positive-sequence line current, the changed second reduced positive-sequence phase voltage, the changed second reduced positive-sequence line current, the changed third reduced positive-sequence phase voltage and the changed third reduced positive-sequence line current;That is, it can monitor the complex impedance parameters of the power transformer during its operation, which means it can truly achieve real-time online monitoring of the complex impedance parameters of the transformer without power outage, enabling real-time online monitoring of the operation status of the power transformer based on the complex impedance parameters and conducting risk assessment. This effectively solves the problem of power outage required in the prior art. Moreover, since the positive sequence variables before and after the voltage or current change are used to calculate the complex impedance parameters, the calculated complex impedance parameters have almost no error, with high accuracy. At the same time, there is no problem of being restricted by test conditions. Additionally, this method of the present application can detect changes in transformer parameters as early as possible, prevent the long-term accumulation of minor faults, thereby avoiding the impact of major faults on the power system, and plays an important role in detecting early transformer faults and ensuring the safe and stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0057] Wherein:

[0058] Figure 1 is a schematic diagram of a method for monitoring the complex impedance parameters of a power transformer in an embodiment of the present application;

[0059] Figure 2 is a schematic diagram of the equivalent circuit of the power transformer to be measured in an embodiment of the present application;

[0060] Figure 3 is a schematic diagram of the equivalent transformation diagram corresponding to the equivalent circuit of the power transformer to be measured in an embodiment of the present application;

[0061] Figure 4 is a schematic diagram of a device for monitoring the complex impedance parameters of a power transformer in an embodiment of the present application;

[0062] Figure 5 is another schematic diagram of a device for monitoring the complex impedance parameters of a power transformer in an embodiment of the present application;

[0063] Figure 6 is the internal structure diagram of a computer device in some embodiments. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0065] As a key device in the power grid, the safe operation of power transformers has always been a key concern in the power industry. As one of the components with more faults, the transformer winding poses a major challenge to the stable operation of the power grid. According to investigations, among large transformers in the power system that have been impacted by large currents, more than 20% have experienced winding deformation. Further data reveals that in the cases of unplanned outages of transformers above 220 kV in China, the outage time due to winding problems accounts for a significant proportion: this proportion is as high as 79.49% in 220 kV transformers, and even reaches 98.92% in 500 kV transformers. The mechanical deformation of the winding under the action of electromagnetic force has become a serious problem accounting for up to 70% of the total winding accidents. Obviously, the winding faults of power transformers pose a great threat to the safe operation of the power grid.

[0066] To address this challenge, it has become an essential requirement for building a new energy system and a new power system to understand the operating status of transformers in real time and prevent sudden major equipment failures and power grid accidents. From the external situation, the requirements of the people and the economic society for power supply are increasing day by day, and the pressure on national safety supervision and power supply reliability assessment is also continuously increasing. From the internal situation, power enterprises face problems such as high power grid operation risks and mismatches between equipment scale and maintenance capabilities during transformer maintenance. The risk of equipment asset walls is becoming increasingly prominent, and the maintenance work is about to enter a peak period.

[0067] In the management of the safe operation of transformers, every link is crucial, from the type test before the new product is put into operation to the regular maintenance and on-line monitoring during operation. These inspection methods can generally be divided into two categories: one is the inspection after the transformer stops running, and the other is the on-line monitoring during the operation of the transformer. As the objects to be inspected of the transformer, they are generally divided into three categories: complex impedance parameters, oil quality, and internal partial discharge. These objects to be inspected correspond to different parameters inside the transformer respectively and cannot replace each other. However, power-off inspection not only causes huge economic losses to the power grid but is also not suitable for frequent operation in actual operation; while the detection of gases in oil and partial discharge is vulnerable to interference and the criteria are complex, and there are also many difficulties in engineering practice.

[0068] At present, the power industry urgently needs a monitoring method that is highly reliable, easy to implement and economical to operate. Especially for winding faults, which account for the largest proportion of transformer faults, the short-circuit complex impedance test of the transformer before it is connected to the grid has become a recognized mandatory inspection content. The National Quality Inspection Center stipulates that the short-circuit complex impedance change range of the tested transformer is within 5% to be qualified.

[0069] However, the existing methods for measuring transformer complex impedance parameters are all power-off inspections, such as the frequency response method, the short-circuit complex impedance method, the high-voltage self-excited oscillation method proposed by Yunnan Electric Power Research Institute, and the traditional method for measuring the no-load and short-circuit characteristics of the transformer. In addition, the traditional method for measuring the no-load and short-circuit characteristics of the transformer is also limited by the test conditions, which undoubtedly brings huge hidden dangers to the stable operation of the power grid.

[0070] In this context, real-time online monitoring of the complex impedance parameters of power transformers has become a technical problem that needs to be solved urgently. The patent "Online Real-time Identification Device and Method for Power Transformer Winding Parameters (CN101261297B)" discloses the online identification of winding complex impedance (i.e., short-circuit complex impedance of winding) by recursive least squares method, but this method cannot truly realize real-time online monitoring in actual application, and the calculated winding complex impedance parameters also have the problem of large errors.

[0071] In addition, although the existing online monitoring method of mechanical vibration can realize the qualitative judgment of the change of transformer compression force, so that the operating status of the power transformer can be monitored online in real time, the threshold of mechanical vibration evaluation is difficult to determine.

[0072] Therefore, how to monitor the complex impedance parameters of the transformer in real time online without power outage so that the operating status of the power transformer can be monitored in real time online based on the complex impedance parameters and risk assessment can be performed is a technical problem that needs to be solved urgently.

[0073] In response to the above problems, the present application proposes a method and device for online monitoring of the complex impedance parameters of a power transformer by synchronous vector, which calculates the complex impedance parameters by real-time synchronous acquisition of positive-sequence vector variables before and after the voltage or current changes, so as to solve the problems existing in the prior art. The specific implementation principle will be described in detail in the following embodiments.

[0074] In a first aspect, the present application provides a method for online monitoring of complex impedance parameters of a power transformer by synchronous vector.

[0075] See also Figure 1 , is a schematic diagram of a method for monitoring complex impedance parameters of a power transformer in an embodiment of the present application, the method comprising:

[0076] Step 110: Synchronously collect the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding of the power transformer to be measured, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding.

[0077] Among them, the power transformer to be measured refers to the transformer that needs to be monitored online.

[0078] In some embodiments, for the determination method of positive-sequence voltage and positive-sequence current, first synchronously collect the three-phase voltage and three-phase current at the inlet of the first winding, the three-phase voltage and three-phase current at the outlet of the second winding, and the three-phase voltage and three-phase current at the outlet of the third winding, and then determine the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding according to the three-phase voltage and three-phase current at the inlet of the first winding, determine the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding according to the three-phase voltage and three-phase current at the outlet of the second winding, and determine the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding according to the three-phase voltage and three-phase current at the outlet of the third winding.

[0079] Step 120: Successively reduce the first positive-sequence phase voltage vector, the first positive-sequence line current vector, the second positive-sequence phase voltage vector, the second positive-sequence line current vector, the third positive-sequence phase voltage vector, and the third positive-sequence line current vector to the reference winding to obtain the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence phase voltage vector, and the third reduced positive-sequence line current vector, where the reference winding is any one of the first winding, the second winding, and the third winding.

[0080] It should be noted that in this application, by converting the positive-sequence phase voltage vectors and positive-sequence line current vectors of each winding to the same reference basis, that is, the reference winding, it can be ensured that the parameters of all windings are processed under the same reference conditions, thereby improving the accuracy and consistency of subsequent processing.

[0081] In some embodiments, for the determination method of reduction, according to the rated voltage ratio and angular relationship between each winding and the reference winding, successively reduce the first positive-sequence phase voltage vector, the first positive-sequence line current vector, the second positive-sequence phase voltage vector, the second positive-sequence line current vector, the third positive-sequence phase voltage vector, and the third positive-sequence line current vector to the reference winding to obtain the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence phase voltage vector, and the third reduced positive-sequence line current vector.

[0082] Step 130: When it is detected that the voltage or current on any side of the power transformer under test changes, return to execute the step of synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding of the power transformer under test, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding, so as to obtain the changed first reduced positive-sequence phase voltage vector, the changed first reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed second reduced positive-sequence line current vector, the changed third reduced positive-sequence phase voltage vector, and the changed third reduced positive-sequence line current vector.

[0083] Regarding the determination method for the change in voltage or current on any side of the power transformer under test, in some embodiments, the apparent power output by the power transformer under test can be monitored. When the change rate between the apparent power output by the power transformer under test at the current moment and the apparent power at the previous moment is greater than the first preset percentage, it is determined that the voltage or current on any side of the power transformer under test has changed; among them, the first preset percentage can be set by the operator based on a large amount of experience, experiments, or statistics. Of course, it can also be set by the operator according to actual needs.

[0084] In some embodiments, preferably, the first preset percentage can be set to any percentage in the range of 0.1% to 10%, or set to the range of 0.1% to 10%.

[0085] Step 140: Obtain the equivalent circuit of the transformer excitation complex impedance branch at the neutral point. According to the first reduced positive-sequence phase voltage, the first reduced positive-sequence line current, the second reduced positive-sequence phase voltage, the second reduced positive-sequence line current, the third reduced positive-sequence phase voltage, the third reduced positive-sequence line current, the changed first reduced positive-sequence phase voltage, the changed first reduced positive-sequence line current, the changed second reduced positive-sequence phase voltage, the changed second reduced positive-sequence line current, the changed third reduced positive-sequence phase voltage, and the changed third reduced positive-sequence line current, determine the first winding complex impedance of the first winding, the second winding complex impedance of the second winding, the third winding complex impedance of the third winding, and the excitation complex impedance of the power transformer under test; the winding complex impedance is the short-circuit complex impedance.

[0086] It should be noted that since the winding complex impedance of the winding has a proportional relationship with both voltage and current, and the change in voltage or current will directly affect the voltage and current in the winding. Therefore, in some embodiments, the present application determines the winding complex impedance of the winding by synchronously collecting the positive-sequence vector variables before and after the change in voltage or current in real time.

[0087] Similarly, since there is also a proportional relationship between the excitation complex impedance of the power transformer under test and the voltage and current, and the changes in voltage or current will directly affect the voltage and current in the winding, in some embodiments, the present application determines the excitation complex impedance of the winding by synchronously collecting the positive sequence vector variables before and after the change in voltage or current in real time.

[0088] For example, please refer to Figure 2 , which is a schematic diagram of the equivalent circuit of the power transformer under test in the embodiment of the present application. The r shown in this schematic diagram GT is the resistance corresponding to the excitation conductance of the power transformer under test, and x Br is the reactance corresponding to the excitation susceptance of the power transformer under test. R T1 , R T2 , R T3 are the winding resistances corresponding to the winding complex impedances of the first winding to the third winding respectively, and X T1 , X T2 , X T3 are the winding reactances corresponding to the winding complex impedances of the first winding to the third winding respectively; please refer to Figure 3 , which is a schematic diagram of the equivalent transformation diagram corresponding to the equivalent circuit of the power transformer under test in the embodiment of the present application. The shown in this schematic diagram is the zero-sequence current, and Z m is the parallel impedance complex impedance of r GT and x Br in the excitation circuit of the power transformer under test. I m1 is the current in the loop where Z m and Z1 are located, and I m2 is the current in the loop where Z m and Z2 are located, and I m3 is the current in the loop where Z2 and Z3 are located.

[0089] In the embodiment of the present application, by calculating the complex impedance parameters by synchronously collecting the positive sequence vector variables before and after the change in voltage or current in real time, it is possible to monitor the complex impedance parameters of the transformer during the operation of the power transformer, that is, it is possible to truly realize real-time online monitoring of the complex impedance parameters of the transformer without power outage, so that it is possible to monitor the operation state of the power transformer based on the complex impedance parameters in real time and conduct risk assessment, effectively solving the problem of power outage required by the prior art. And since this method calculates the complex impedance parameters by using the positive sequence variables before and after the change in voltage or current, the calculated complex impedance parameters have almost no error, with high accuracy. At the same time, there is no problem of being restricted by test conditions. And this method of the present application can detect the changes in transformer parameters as early as possible, prevent the long-term accumulation of minor faults, thereby avoiding the impact of major faults on the power system, and plays an important role in detecting early faults of transformers and ensuring the safe and stable operation of the power system.

[0090] In addition, this method of the present application also has the following advantages: By real-time online monitoring of the complex impedance parameters of the transformer, abnormal changes in the transformer windings can be detected in a timely manner, so as to take preventive maintenance measures, avoid power grid accidents caused by sudden major equipment failures, and significantly improve the operation reliability and stability of the power grid; Compared with traditional power-off maintenance, this application can monitor without power-off, reducing the economic losses caused by power-off. At the same time, it also reduces the inconvenience caused to the power grid and users by frequent power-off maintenance, and real-time monitoring can detect and handle potential faults in a timely manner, avoiding more expensive repair and replacement costs caused by the expansion of faults; By real-time monitoring of the changes in the complex impedance parameters of the transformer, the maintenance plan of the transformer can be formulated more accurately. For transformers with small or stable parameter changes, the maintenance cycle can be appropriately extended, while for transformers with abnormal parameter changes, maintenance can be arranged in advance, so as to optimize the allocation of maintenance resources; Real-time monitoring of the operation status of the transformer, timely detection and handling of winding faults, helps to maintain the good working state of the transformer, and further improves the power supply quality and stability of the power grid, meeting the needs of the people and the economic society for high-quality power supply.

[0091] In a feasible implementation manner, in step 120 of the above embodiment, the first positive-sequence phase voltage vector, the first positive-sequence line current vector, the second positive-sequence phase voltage vector, the second positive-sequence line current vector, the third positive-sequence phase voltage vector, and the third positive-sequence line current vector are sequentially reduced to the reference winding to obtain the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence phase voltage vector, and the third reduced positive-sequence line current vector, including:

[0092] Using the formula To determine the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence phase voltage vector, and the third reduced positive-sequence line current vector;

[0093] Wherein, when i is 1, Is the first reduced positive-sequence phase voltage vector, k Bi Is the rated voltage ratio between the reference winding and the first winding, Is the first positive-sequence phase voltage vector, e is the natural constant, j is the imaginary unit, Is the angle by which the reference winding leads the first winding, Is the first reduced positive-sequence line current vector, Is the first positive-sequence line current vector; when i is 2, Is the second reduced positive-sequence phase voltage vector, k Bi Is the rated voltage ratio between the reference winding and the second winding, Is the second positive-sequence phase voltage vector, is the angle by which the reference winding leads the second winding, is the second reduced positive-sequence line current vector, is the second positive-sequence line current vector; when i = 3, is the third reduced positive-sequence phase voltage vector, k Bi is the rated voltage ratio between the reference winding and the third winding, is the third positive-sequence phase voltage vector, is the angle by which the reference winding leads the third winding, is the third reduced positive-sequence line current vector, is the third positive-sequence line current vector.

[0094] It should be noted that if the winding to be reduced and the reference winding are the same winding, then k Bi is equal to 1, is equal to 0, is equal to is equal to It can be understood that since the winding to be reduced and the reference winding are the same winding, the rated voltage and angle relationships are the same. Therefore, k Bi is equal to 1, is equal to 0, and thus is equal to is equal to

[0095] In the embodiments of the present application, by providing clear formulas and methods for winding reduction, not only the accuracy and consistency of reduction are improved, but also the reduction process is simplified, and it supports real-time monitoring and dynamic analysis as well as the development of intelligent operation and maintenance, promoting the safe and stable operation of the power grid and the improvement of the economic benefits of power enterprises.

[0096] It can be understood that improving the accuracy and consistency of reduction: By using explicit formulas to reduce the positive-sequence phase voltage vectors and positive-sequence line current vectors of each winding to the reference winding, the accuracy and consistency of the reduction process can be ensured. This accuracy is crucial for subsequent calculations of winding complex impedance parameters because the accurate calculation of winding complex impedance depends on accurate voltage and current data; Simplifying the reduction process: The formulas contain the rated voltage ratios and angular relationships between windings, and these parameters are usually known during the transformer design and manufacturing process. Therefore, using these formulas for reduction can greatly simplify the reduction process, reducing computational complexity and time costs; Supporting real-time monitoring and dynamic analysis: Since the reduction process is based on real-time collected voltage and current data, it can support real-time monitoring and dynamic analysis. This means that accurate winding complex impedance parameters can be obtained in real time, and risk assessment and preventive maintenance can be carried out based on these parameters, thereby improving the operational reliability and stability of the power grid.

[0097] In a feasible implementation manner, for step 140 in the above embodiment, to obtain the equivalent circuit of the transformer exciting complex impedance branch at the neutral point, and determine the first winding complex impedance of the first winding, the second winding complex impedance of the second winding, the third winding complex impedance of the third winding, and the exciting complex impedance of the power transformer to be measured according to the first reduced positive-sequence phase voltage, the first reduced positive-sequence line current, the second reduced positive-sequence phase voltage, the second reduced positive-sequence line current, the third reduced positive-sequence phase voltage, the third reduced positive-sequence line current, the changed first reduced positive-sequence phase voltage, the changed first reduced positive-sequence line current, the changed second reduced positive-sequence phase voltage, the changed second reduced positive-sequence line current, the changed third reduced positive-sequence phase voltage, and the changed third reduced positive-sequence line current, it includes: obtaining the equivalent circuit of the transformer exciting complex impedance branch at the neutral point, and writing the first equation according to the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence line current vector, the first winding complex impedance of the first winding, and the exciting complex impedance of the power transformer to be measured; writing the second equation according to the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the third reduced positive-sequence line current vector, the second winding complex impedance of the second winding, and the exciting complex impedance of the power transformer to be measured; writing the third equation according to the second reduced positive-sequence phase voltage vector, the third reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the third reduced positive-sequence phase voltage vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding; obtaining the equivalent circuit of the transformer exciting complex impedance branch at the neutral point, and writing the fourth equation according to the changed first reduced positive-sequence phase voltage vector, the changed first reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed second reduced positive-sequence line current vector, the changed third reduced positive-sequence line current vector, the first winding complex impedance of the first winding, and the exciting complex impedance of the power transformer to be measured; writing the fifth equation according to the changed first reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed third reduced positive-sequence line current vector, the second winding complex impedance of the second winding, and the exciting complex impedance of the power transformer to be measured; writing the sixth equation according to the changed second reduced positive-sequence phase voltage vector, the changed third reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed third reduced positive-sequence phase voltage vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding;Take the first equation, the second equation, the third equation, and the fourth equation to form a system of equations, or take the first equation, the second equation, the fifth equation, and the sixth equation to form a system of equations, or take the third equation, the fourth equation, the fifth equation, and the sixth equation to form a system of equations, or take the first equation, the third equation, the fourth equation, and the fifth equation to form a system of equations, or take the second equation, the fourth equation, the fifth equation, and the sixth equation to form a system of equations, and solve for the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding, and the exciting complex impedance of the power transformer to be measured.

[0098] In the embodiment of the present application, by collecting the reduced positive-sequence phase voltage vector and the reduced positive-sequence line current vector before and after the voltage or current change in real time to calculate the complex impedance of the winding, not only the accuracy and precision of the calculation are improved, but also the reliability and stability of the monitoring method are enhanced, supporting real-time online monitoring and dynamic analysis, which helps to improve the safety and stability of the power grid operation, optimize the allocation of maintenance resources, and promote the development of intelligent operation and maintenance.

[0099] It can be understood that improving the accuracy and precision of the winding complex impedance calculation: by using the reduced positive-sequence phase voltage vector and the reduced positive-sequence line current vector before and after the voltage or current change respectively to calculate the complex impedance of each winding, the accuracy and precision of the calculation can be greatly improved. This accuracy is obtained through real-time monitoring of the transformer in actual operation, avoiding the errors that may be brought by the traditional power-off inspection method; enhancing the reliability and stability of the monitoring method: this method uses the data before and after the voltage or current change of the transformer to calculate the complex impedance of the winding. Since the voltage or current change is a common phenomenon in actual operation, this method can be used frequently without being restricted by test conditions, enhancing the reliability and stability of the monitoring method; supporting real-time online monitoring and dynamic analysis: this method can calculate the complex impedance of the winding in real time by collecting the voltage and current data before and after the voltage or current change in real time, supporting real-time monitoring and dynamic analysis. This enables the operation and maintenance personnel to timely detect the change of the winding complex impedance and take preventive measures to prevent the occurrence of faults.

[0100] In a feasible implementation manner, the first equation in the above embodiment is

[0101] The second equation is

[0102] The third equation is

[0103] The fourth equation is

[0104] The fifth equation is

[0105] The sixth equation is

[0106] Among them, Z1 is the complex impedance of the first winding, Z2 is the complex impedance of the second winding, Z3 is the complex impedance of the third winding, and Z m is the exciting complex impedance, is the first reduced positive-sequence phase voltage vector; is the changed first reduced positive-sequence phase voltage vector; is the second reduced positive-sequence phase voltage vector; is the changed second reduced positive-sequence phase voltage vector; is the third reduced positive-sequence phase voltage vector; is the changed third reduced positive-sequence phase voltage vector; is the first reduced positive-sequence line current vector; is the changed first reduced positive-sequence line current vector; is the second reduced positive-sequence line current vector; is the changed second reduced positive-sequence line current vector; is the third reduced positive-sequence line current vector; is the changed third reduced positive-sequence line current vector.

[0107] In the embodiment of the present application, the method of determining the winding complex impedance parameters by using the reduced positive-sequence phase voltage vectors and reduced positive-sequence line current vectors before and after the voltage or current change through specific formulas shows significant beneficial effects in improving calculation accuracy, enhancing real-time monitoring capabilities, optimizing the reliability of power grid operation, reducing maintenance costs, and meeting the high-quality power supply requirements. This is of great significance for realizing the on-line monitoring of transformer complex impedance parameters and ensuring the safe and stable operation of the power system.

[0108] It can be understood that improving the calculation accuracy: calculations are performed through precise mathematical formulas, taking into account the influence of voltage or current changes on the winding voltage and current, so as to more accurately calculate the complex impedance parameters of each winding, avoiding errors caused by inconsistent benchmarks or simplified calculation processes, and improving the accuracy of complex impedance parameter calculation; enhancing real-time monitoring capabilities: this method calculates based on real-time collected data, supports online monitoring of transformers, can promptly detect abnormal changes in winding parameters, and conduct risk assessments, thereby taking corresponding preventive maintenance measures; optimizing the reliability of power grid operation: real-time monitoring of the complex impedance parameters of transformer windings helps to promptly detect and handle potential faults, prevent the expansion of faults from causing greater impacts on the power grid, helps to maintain the good working condition of the transformer, and further improves the power supply quality and stability of the power grid; reducing maintenance costs: through real-time monitoring, the maintenance plan of the transformer can be formulated more precisely. For transformers with stable or less variable parameters, the maintenance cycle can be appropriately extended, thereby optimizing the allocation of maintenance resources and reducing maintenance costs; meeting the demand for high-quality power supply: real-time monitoring and accurate calculation of winding complex impedance parameters help to promptly detect and handle winding faults, ensuring the safe and stable operation of the power system, which is of great significance for meeting the needs of the people and the economic society for high-quality power supply.

[0109] In a feasible implementation manner, the method in the above embodiment further includes: determining the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer to be measured according to the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding, and the magnetizing complex impedance.

[0110] In some embodiments, it is also necessary to obtain the rated voltage of the reference winding and the rated capacity of the power transformer to be measured, and then determine the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer to be measured according to the rated voltage, rated capacity, the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding, and the magnetizing complex impedance.

[0111] In the embodiments of the present application, by determining the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer to be measured, not only is real-time online monitoring achieved without power outage, the accuracy and precision of complex impedance parameter calculation are improved, but also the accuracy and precision of electrical parameter (such as load loss, impedance voltage percentage, no-load loss, and no-load current percentage) calculation are improved.

[0112] In a feasible implementation manner, the above-mentioned determining the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer to be measured according to the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding, and the magnetizing complex impedance includes:

[0113] Using the formula to determine the load loss, percentage impedance voltage, no-load loss, and percentage no-load current of the power transformer to be measured;

[0114] wherein, P ij is the load loss between the i-th winding and the j-th winding of the power transformer to be measured, with the unit of kW, real() is the real part extraction function, Z i is the complex impedance of the i-th winding, Z j is the complex impedance of the j-th winding, S N is the rated capacity of the power transformer to be measured, with the unit of kVA, U N is the rated voltage of the reference winding, with the unit of kV, U ij % is the percentage impedance voltage between the i-th winding and the j-th winding of the power transformer to be measured, imag() is the imaginary part extraction function, P0 is the no-load loss, with the unit of kW, and I0% is the percentage no-load current.

[0115] In the embodiment of the present application, through the clear formula and the reduced complex impedance of the winding, combined with the rated capacity of the power transformer to be measured and the rated voltage of the reference winding, the load loss, percentage impedance voltage, no-load loss, and percentage no-load current of the power transformer to be measured can be accurately calculated. This method avoids the errors that may be brought by power-off inspection in the traditional method and improves the accuracy and precision of the calculation.

[0116] In addition, this method can be monitored without power-off, and key electrical parameters such as load loss, percentage impedance voltage, no-load loss, and percentage no-load current can be obtained in real time under the operating state of the transformer, which helps the operation and maintenance personnel to timely understand the operating state of the transformer, take necessary preventive maintenance measures, and prevent sudden major equipment failures.

[0117] In a feasible implementation manner, the method in the above embodiment further includes: determining whether there is an abnormality in the power transformer to be measured according to the comparison results between the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding and the corresponding reference complex impedance thresholds; and / or, determining whether there is an abnormality in the power transformer to be measured according to the comparison results between the load loss, percentage impedance voltage, no-load loss, percentage no-load current of the power transformer to be measured and the corresponding load loss threshold, percentage impedance voltage threshold, no-load loss threshold, percentage no-load current threshold.

[0118] Among them, the reference complex impedance threshold, load loss threshold, percentage impedance voltage threshold, no-load loss threshold, and percentage no-load current threshold can all be set by the operator according to a large amount of experience, experiments or statistics. Of course, they can also be set by the operator according to actual needs.

[0119] In some embodiments, the reference complex impedance threshold, load loss threshold, impedance voltage percentage threshold, no-load loss threshold, and no-load current percentage threshold can all be the factory values on the factory nameplate. Of course, in other embodiments, the reference complex impedance threshold can also be the average value of the winding complex impedance obtained historically, or the winding complex impedance obtained initially.

[0120] For determining whether there is an abnormality in the power transformer under test based on the comparison results between the load loss, impedance voltage percentage, no-load loss, no-load current percentage of the power transformer under test and the corresponding load loss threshold, impedance voltage percentage threshold, no-load loss threshold, and no-load current percentage threshold, in some embodiments, it can be determined whether there is an abnormality in the power transformer under test according to the comparison results between the load loss and impedance voltage percentage of each winding among the first winding to the third winding and the corresponding load loss threshold and impedance voltage percentage threshold, and the comparison results between the no-load loss and no-load current percentage of the power transformer under test and the corresponding no-load loss threshold and no-load current percentage threshold.

[0121] In other embodiments, it can also be determined whether there is an abnormality in the power transformer under test according to the comparison result between the change rate of the complex impedance of the first winding, the second winding, and the third winding with respect to the corresponding reference complex impedance threshold and a second preset percentage.

[0122] Specifically, if the change rate of any one winding complex impedance with respect to the corresponding reference complex impedance threshold is greater than the second preset percentage, it is determined that there is an abnormality in the power transformer under test.

[0123] In some embodiments, preferably, the second preset percentage can be set to any percentage in the range of 10% to 30%, or set to the range of 10% to 30%.

[0124] In other embodiments, it can also be determined whether there is an abnormality in the power transformer under test according to the comparison results between the change rates of the load loss and impedance voltage percentage of each winding among the first winding to the third winding with respect to the corresponding load loss threshold and impedance voltage percentage threshold and a third threshold percentage, and the comparison results between the change rates of the no-load loss and no-load current percentage with respect to the corresponding no-load loss threshold and no-load current percentage threshold.

[0125] Specifically, if the change rate of any one of the load loss, impedance voltage percentage, no-load loss, and no-load current percentage with respect to the corresponding load loss threshold, impedance voltage percentage threshold, no-load loss threshold, and no-load current percentage threshold is greater than the third preset percentage, it is determined that there is an abnormality in the power transformer under test.

[0126] In some embodiments, preferably, the third preset percentage can be set to any percentage within 5% to 20%, or set to the range of 5% to 20%.

[0127] In the embodiments of the present application, by adding the comparison of the winding complex impedance with the reference complex impedance threshold, the load loss, the percentage of impedance voltage, the no-load loss, and the comparison of the no-load current percentage with the corresponding thresholds, etc., the intelligent level of transformer operation and maintenance can be further improved, major equipment failures can be prevented, the power grid safety can be guaranteed, the maintenance resource allocation can be optimized, and the safe and stable operation of the power grid and the economic benefits of power enterprises can be promoted.

[0128] In a feasible implementation manner, step 110 in the above embodiments synchronously collects the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding of the power transformer to be measured, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding, including: synchronously collecting the first three-phase voltage and the second three-phase current at the inlet of the first winding, the second three-phase voltage and the second three-phase current at the outlet of the second winding, and the third three-phase voltage and the third three-phase current at the outlet of the third winding; determining the first positive-sequence phase voltage vector and the first positive-sequence line current vector according to the first three-phase voltage and the first three-phase current, determining the second positive-sequence phase voltage vector and the second positive-sequence line current vector according to the second three-phase voltage and the second three-phase current, and determining the third positive-sequence phase voltage vector and the third positive-sequence line current vector according to the third three-phase voltage and the third three-phase current.

[0129] In the embodiments of the present application, by synchronously collecting the three-phase voltage and the three-phase current and calculating the positive-sequence vector, the accuracy and reliability of the data can be ensured, which is crucial for subsequent calculation of parameters such as winding impedance, load loss, percentage of impedance voltage, no-load loss, and no-load current percentage.

[0130] The present application provides a power transformer complex impedance parameter synchronous vector online monitoring device in a second aspect.

[0131] Please refer to Figure 4 , which is a schematic diagram of a power transformer complex impedance parameter synchronous vector online monitoring device in the embodiments of the present application. The device includes a sensor module 410 and a controller 420.

[0132] Among them, the sensor module 410 is connected to the controller 420.

[0133] In a feasible implementation, the sensor module 410 is used to connect to the three phases at the inlet of the first winding, the three phases at the outlet of the second winding, and the three phases at the outlet of the third winding of the power transformer to be measured respectively, and is used to measure the first three-phase voltage and the second three-phase current at the inlet of the first winding, the second three-phase voltage and the second three-phase current at the outlet of the second winding, and the third three-phase voltage and the third three-phase current at the outlet of the third winding; the controller 420 is used to synchronously collect the first three-phase voltage, the first three-phase current, the second three-phase voltage, the second three-phase current, the third three-phase voltage and the third three-phase current, so as to synchronously collect the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding, and execute the method according to any one of the first aspect.

[0134] In the embodiment of the present application, the device includes a sensor module 410 and a controller 420, which can synchronously collect the positive-sequence vector variables before and after the voltage or current change in real time to calculate the complex impedance parameters, and monitor the complex impedance parameters of the transformer during the operation of the power transformer, that is, it can truly realize the real-time online monitoring of the complex impedance parameters of the transformer without power outage, so that the operation state of the power transformer can be monitored in real time online based on the complex impedance parameters and risk assessment can be carried out, effectively solving the problem of power outage required by the prior art. Moreover, since the positive-sequence variables before and after the voltage or current change are used to calculate the complex impedance parameters, the calculated complex impedance parameters have almost no error, the accuracy rate is relatively high, and there is no problem of being restricted by test conditions. At the same time, this method of the present application can detect the change of transformer parameters as early as possible, prevent the long-term accumulation of minor faults, thereby avoiding the impact of major faults on the power system, and plays an important role in detecting early faults of the transformer and ensuring the safe and stable operation of the power system.

[0135] Based on Figure 4 , please refer to Figure 5 , which is another schematic diagram of an online monitoring device for synchronizing vectors of complex impedance parameters of a power transformer in the embodiment of the present application. The sensor module 410 includes a first voltage sensor 411, a second voltage sensor 412, a third voltage sensor 413, a first current sensor 414, a second current sensor 415 and a third current sensor 416.

[0136] In a feasible implementation, the first voltage sensor 411 and the first current sensor 414 are used to be respectively connected to the three-phase of the first winding at the inlet, and to measure the first three-phase voltage and the first three-phase current; the second voltage sensor 412 and the second current sensor 415 are used to be respectively connected to the three-phase of the second winding at the outlet, and to measure the second three-phase voltage and the second three-phase current; the third voltage sensor 413 and the third current sensor 416 are used to be respectively connected to the three-phase of the third winding at the outlet, and to measure the third three-phase voltage and the third three-phase current.

[0137] In the embodiment of the present application, the sensor module 410 includes the first voltage sensor 411, the second voltage sensor 412, the third voltage sensor 413, the first current sensor 414, the second current sensor 415 and the third current sensor 416, and can synchronously collect the three-phase voltage and the three-phase current, which can ensure the accuracy and reliability of the data, and is crucial for subsequent calculation of parameters such as the complex impedance of the winding, the load loss, the percentage of impedance voltage, the no-load loss and the percentage of no-load current.

[0138] In addition, the device has a simple structure and convenient operation, and has high practical value and popularization prospect.

[0139] It should be particularly noted that the voltage and current in the present application are in vector form; for example, the first measurement of the second reduced positive-sequence phase voltage is -0.86 - 22.08ikV, and the first measurement of the second reduced positive-sequence line current is -25.06 - 179.57iA.

[0140] The present application also provides a computer-readable storage medium in a third aspect, storing a computer program, which when executed by a controller, enables the controller to execute a method for online monitoring of complex impedance parameters of a power transformer in a synchronous vector manner in the above method embodiment.

[0141] The present application also provides a computer device in a fourth aspect, including a memory and a controller, the memory stores a computer program, which when executed by the controller, enables the controller to execute a method for online monitoring of complex impedance parameters of a power transformer in a synchronous vector manner in the above method embodiment.

[0142] Figure 6 The internal structure diagram of the computer device in some embodiments is shown. The computer device can specifically be a terminal, a server, or a gateway. As Figure 6 shown, the computer device includes a controller, a memory and a network interface connected through a system bus.

[0143] Among them, the memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium of the computer device stores an operating system and may also store a computer program. When the computer program is executed by the controller, the controller can implement each step in the above method embodiments. The internal memory may also store a computer program. When the computer program is executed by the controller, the controller can execute each step in the above method embodiments. Those skilled in the art can understand that Figure 6 The structure shown in Figure 6 is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the computer device to which the solution of this application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0144] Those of ordinary skill in the art can understand that all or part of the processes in the above method embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the above method embodiments.

[0145] Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and Rambus dynamic RAM (RDRAM), etc.

[0146] It should be noted that the technical features of the above embodiments can be combined arbitrarily, and can also be used for a double-winding transformer through simple transformation by those skilled in the art. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0147] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. An online monitoring method for synchronous vectors of complex impedance parameters of a power transformer, characterized in that, The method includes: Synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the entrance of the first winding of the power transformer under test, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the exit of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the exit of the third winding; Successively reducing the first positive-sequence phase voltage vector, the first positive-sequence line current vector, the second positive-sequence phase voltage vector, the second positive-sequence line current vector, the third positive-sequence phase voltage vector, and the third positive-sequence line current vector to the reference winding to obtain the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence phase voltage vector, and the third reduced positive-sequence line current vector, where the reference winding is any one of the first winding, the second winding, and the third winding; In the case where the voltage or current on any side of the power transformer under test changes, return to execute the step of synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the entrance of the first winding of the power transformer under test, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the exit of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the exit of the third winding, so as to obtain the changed first reduced positive-sequence phase voltage vector, the changed first reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed second reduced positive-sequence line current vector, the changed third reduced positive-sequence phase voltage vector, and the changed third reduced positive-sequence line current vector; Obtain the equivalent circuit of the transformer excitation complex impedance branch at the neutral point, and determine the first winding complex impedance of the first winding, the second winding complex impedance of the second winding, the third winding complex impedance of the third winding, and the excitation complex impedance of the power transformer under test according to the first reduced positive-sequence phase voltage, the first reduced positive-sequence line current, the second reduced positive-sequence phase voltage, the second reduced positive-sequence line current, the third reduced positive-sequence phase voltage, the third reduced positive-sequence line current, the changed first reduced positive-sequence phase voltage, the changed first reduced positive-sequence line current, the changed second reduced positive-sequence phase voltage, the changed second reduced positive-sequence line current, the changed third reduced positive-sequence phase voltage, and the changed third reduced positive-sequence line current; the winding complex impedance is the short-circuit complex impedance.

2. The method according to claim 1, wherein The step of successively reducing the first positive-sequence phase voltage vector, the first positive-sequence line current vector, the second positive-sequence phase voltage vector, the second positive-sequence line current vector, the third positive-sequence phase voltage vector, and the third positive-sequence line current vector to the reference winding to obtain the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence phase voltage vector, and the third reduced positive-sequence line current vector includes: Using the formula to determine the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence phase voltage vector, and the third reduced positive-sequence line current vector; Wherein, when i is 1, is the first reduced positive-sequence phase voltage vector, k Bi is the rated voltage ratio between the reference winding and the first winding, is the first positive-sequence phase voltage vector, e is the natural constant, and j is the imaginary unit, is the angle by which the reference winding leads the first winding, is the first reduced positive-sequence line current vector, is the first positive-sequence line current vector; when i is 2, is the second reduced positive-sequence phase voltage vector, k Bi is the rated voltage ratio between the reference winding and the second winding, is the second positive-sequence phase voltage vector, is the angle by which the reference winding leads the second winding, is the second reduced positive-sequence line current vector, is the second positive-sequence line current vector; when i is 3, is the third reduced positive-sequence phase voltage vector, k Bi is the rated voltage ratio between the reference winding and the third winding, is the third positive-sequence phase voltage vector, is the angle by which the reference winding leads the third winding, is the third reduced positive-sequence line current vector, is the third positive-sequence line current vector.

3. The method according to claim 1, wherein Obtain the equivalent circuit of the excitation complex impedance branch of the transformer at the neutral point. Determine the first winding complex impedance of the first winding, the second winding complex impedance of the second winding, the third winding complex impedance of the third winding, and the excitation complex impedance of the power transformer under test according to the first reduced positive-sequence phase voltage, the first reduced positive-sequence line current, the second reduced positive-sequence phase voltage, the second reduced positive-sequence line current, the third reduced positive-sequence phase voltage, the third reduced positive-sequence line current, the changed first reduced positive-sequence phase voltage, the changed first reduced positive-sequence line current, the changed second reduced positive-sequence phase voltage, the changed second reduced positive-sequence line current, the changed third reduced positive-sequence phase voltage, and the changed third reduced positive-sequence line current, including: Obtain the equivalent circuit of the excitation complex impedance branch of the transformer at the neutral point. Write the first equation according to the first reduced positive-sequence phase voltage vector, the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the second reduced positive-sequence line current vector, the third reduced positive-sequence line current vector, the first winding complex impedance of the first winding, and the excitation complex impedance of the power transformer under test; Write the second equation according to the first reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the third reduced positive-sequence line current vector, the second winding complex impedance of the second winding, and the excitation complex impedance of the power transformer under test; Write the third equation according to the second reduced positive-sequence phase voltage vector, the third reduced positive-sequence line current vector, the second reduced positive-sequence phase voltage vector, the third reduced positive-sequence phase voltage vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding; Obtain the equivalent circuit of the excitation complex impedance branch of the transformer at the neutral point. Write the fourth equation according to the changed first reduced positive-sequence phase voltage vector, the changed first reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed second reduced positive-sequence line current vector, the changed third reduced positive-sequence line current vector, the first winding complex impedance of the first winding, and the excitation complex impedance of the power transformer under test; Write the fifth equation according to the changed first reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed third reduced positive-sequence line current vector, the second winding complex impedance of the second winding, and the excitation complex impedance of the power transformer under test; Write the sixth equation according to the changed second reduced positive-sequence phase voltage vector, the changed third reduced positive-sequence line current vector, the changed second reduced positive-sequence phase voltage vector, the changed third reduced positive-sequence phase voltage vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding; Take the first equation, the second equation, the third equation, and the fourth equation to form a system of equations, or take the first equation, the second equation, the fifth equation, and the sixth equation to form a system of equations, or take the third equation, the fourth equation, the fifth equation, and the sixth equation to form a system of equations, or take the first equation, the third equation, the fourth equation, and the fifth equation to form a system of equations, or take the second equation, the fourth equation, the fifth equation, and the sixth equation to form a system of equations, and solve for the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding, and the exciting complex impedance of the power transformer under test.

4. The method according to claim 3, wherein The first equation is The second equation is The 3rd equation is The 4th equation is The 5th equation is The 6th equation is wherein, Z1 is the complex impedance of the first winding, Z2 is the complex impedance of the second winding, Z3 is the complex impedance of the third winding, and Z m is the exciting complex impedance; is the first reduced positive-sequence phase voltage vector; is the changed first reduced positive-sequence phase voltage vector; is the second reduced positive-sequence phase voltage vector; is the changed second reduced positive-sequence phase voltage vector; is the third reduced positive-sequence phase voltage vector; is the changed third reduced positive-sequence phase voltage vector; is the first reduced positive-sequence line current vector; is the changed first reduced positive-sequence line current vector; is the second reduced positive-sequence line current vector; is the changed second reduced positive-sequence line current vector; is the third reduced positive-sequence line current vector; is the changed third reduced positive-sequence line current vector.

5. The method according to claim 1, characterized in that, The method further includes: Determine the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer under test according to the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding, and the exciting complex impedance.

6. The method according to claim 5, characterized in that, The determining the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer under test according to the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding, and the exciting complex impedance includes: Using the formula to determine the load loss, impedance voltage percentage, no-load loss and no-load current percentage of the power transformer to be measured; Among them, P ij is the load loss between the i-th winding and the j-th winding of the power transformer to be measured, with the unit of kW, real() is the real part extraction function, Z i is the value of the i-th winding complex impedance calculated from the reference winding to the nameplate parameters, Z j is the value of the j-th winding complex impedance calculated from the reference winding to the nameplate parameters, S N is the rated capacity of the power transformer to be measured, with the unit of kVA, U N is the rated voltage of the high-voltage winding of the transformer, with the unit of kV, U ij % is the impedance voltage percentage between the i-th winding and the j-th winding of the power transformer to be measured, imag() is the imaginary part extraction function, P0 is the no-load loss, with the unit of kW, and I0% is the no-load current percentage.

7. The method according to claim 1 or 5, characterized in that, The method further includes: Determine whether the power transformer under test is abnormal according to the comparison results between the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding and the corresponding reference complex impedance thresholds; and / or, Determine whether the power transformer under test is abnormal according to the comparison results between the load loss, impedance voltage percentage, no-load loss, no-load current percentage of the power transformer under test and the corresponding load loss threshold, impedance voltage percentage threshold, no-load loss threshold, no-load current percentage threshold.

8. The method according to claim 1, wherein The synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the entrance of the first winding of the power transformer under test, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the exit of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the exit of the third winding includes: Synchronously collect the first three-phase voltage and the second three-phase current at the entrance of the first winding, the second three-phase voltage and the second three-phase current at the exit of the second winding, and the third three-phase voltage and the third three-phase current at the exit of the third winding; Determine the first positive-sequence phase voltage vector and the first positive-sequence line current vector according to the first three-phase voltage and the first three-phase current, determine the second positive-sequence phase voltage vector and the second positive-sequence line current vector according to the second three-phase voltage and the second three-phase current, and determine the third positive-sequence phase voltage vector and the third positive-sequence line current vector according to the third three-phase voltage and the third three-phase current.

9. An on-line monitoring device for synchronous vectors of complex impedance parameters of a power transformer, characterized in that, The device includes a sensor module and a controller; The sensor module is connected to the controller; The sensor module is used to be connected to the three phases at the inlet of the first winding, the three phases at the outlet of the second winding, and the three phases at the outlet of the third winding of the power transformer to be measured respectively, and is used to measure the first three-phase voltage and the second three-phase current at the inlet of the first winding, the second three-phase voltage and the second three-phase current at the outlet of the second winding, and the third three-phase voltage and the third three-phase current at the outlet of the third winding; The controller is used to synchronously collect the first three-phase voltage, the first three-phase current, the second three-phase voltage, the second three-phase current, the third three-phase voltage and the third three-phase current, so as to synchronously collect the first positive-sequence phase voltage vector and the first positive-sequence line current vector at the inlet of the first winding, the second positive-sequence phase voltage vector and the second positive-sequence line current vector at the outlet of the second winding, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector at the outlet of the third winding, and execute the method according to any one of claims 1 to 8.

10. The device according to claim 9, characterized in that, The sensor module includes a first voltage sensor, a second voltage sensor, a third voltage sensor, a first current sensor, a second current sensor and a third current sensor; The first voltage sensor and the first current sensor are used to be connected to the three phases at the inlet of the first winding respectively, and are used to measure the first three-phase voltage and the first three-phase current; The second voltage sensor and the second current sensor are used to be connected to the three phases at the outlet of the second winding respectively, and are used to measure the second three-phase voltage and the second three-phase current; The third voltage sensor and the third current sensor are used to be connected to the three phases at the outlet of the third winding respectively, and are used to measure the third three-phase voltage and the third three-phase current.

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