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; and calculating a third positive sequence phase voltage vector and a third positive sequence line current vector of the third winding at the outlet, and reducing to the reference winding, and then returning to execute the above steps when detecting that the voltage or the current of any side of the power transformer to be detected changes, so as to obtain the voltage or the current of any side of the power transformer to be detected. 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 parameters are calculated by synchronously collecting positive sequence vector variables before and after voltage or current changes, so that the problems existing in the prior art are solved.

Description

Technical Field

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

[0002] Power transformers, as critical components of the power grid, have always been a key concern for the power industry. Transformer windings, a component prone to failure, pose a significant challenge to the stable operation of the power grid. Surveys have shown that over 20% of large transformers in power systems subjected to high current surges experience winding deformation. Further data reveals that among unplanned outages of transformers above 220 kV in my country, winding problems account for a significant portion of the downtime: 79.49% for 220 kV transformers and 98.92% for 500 kV transformers. Mechanical deformation of windings caused by electrodynamic forces has become a serious problem, accounting for as much as 70% of all winding accidents. Clearly, power transformer winding failures pose a significant threat to the safe operation of the power grid.

[0003] To meet this challenge, real-time understanding of transformer operating status and preventing sudden major equipment failures and grid incidents have become essential requirements for building a new energy and power system. Externally, the public and the economy are increasingly demanding power supply, and national pressure on safety regulation and power supply reliability assessments is also increasing. Internally, power companies face significant grid operation risks and a mismatch between equipment scale and maintenance resources when overhauling transformers. The risk of an equipment asset wall is becoming increasingly prominent, and maintenance work is about to enter a peak period.

[0004] When it comes to managing the safe operation of transformers, every step is crucial, from pre-commissioning type testing of new products to regular maintenance and online monitoring during operation. These inspection methods can generally be divided into two categories: one is inspection after the transformer has been shut down, and the other is online monitoring during operation. Transformer inspection targets are generally categorized into three main types: impedance parameters, oil quality, and internal partial discharge. These inspection targets each correspond to different parameters within the transformer and are not interchangeable. However, power outage inspections not only cause significant economic losses to the power grid but are also impractical to perform frequently in practice. Furthermore, oil-gas testing cannot monitor winding deformation, and partial discharge detection is susceptible to interference, presenting numerous challenges in engineering practice.

[0005] Currently, the power industry urgently needs a monitoring method that is highly reliable, easy to implement, and economical to operate. This is especially true for winding faults, which account for the largest proportion of transformer failures. Short-circuit impedance testing of transformers before connection to the grid has become a recognized mandatory inspection. The National Quality Inspection Center stipulates that a tested transformer's short-circuit impedance must fall within the specified range of industry standards to be considered qualified.

[0006] However, the existing transformer impedance parameter measurement methods are all power outage tests, such as the frequency response method, the short-circuit impedance method, the high-voltage self-oscillation method proposed by the Yunnan Electric Power Research Institute, and the traditional method of measuring the no-load and short-circuit characteristics of the transformer. In addition, the traditional method of 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] Against this backdrop, real-time online monitoring of power transformer impedance parameters has become a pressing technical challenge. The patent "Device and Method for Online Identification of Power Transformer Winding Parameters (CN101261297B)" discloses online identification of winding impedance (i.e., the short-circuit impedance of the winding) using a recursive least squares method. However, this method fails to achieve true real-time online monitoring in practice, and the calculated winding impedance parameters also suffer from significant errors.

[0008] In addition, although the existing online monitoring method of mechanical vibration can achieve 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 assessment is difficult to determine.

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

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

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

[0012] Synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector of the first winding of the power transformer under test at the inlet, the second positive-sequence phase voltage vector and the second positive-sequence line current vector of the second winding at the outlet, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector of the third winding at the outlet;

[0013] 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 converted to a reference winding to obtain a first converted positive-sequence phase voltage vector, a first converted positive-sequence line current vector, a second converted positive-sequence phase voltage vector, a second converted positive-sequence line current vector, a third converted positive-sequence phase voltage vector, and a third converted positive-sequence line current vector, wherein the reference winding is any one of the first winding, the second winding, and the third winding;

[0014] In the event that a change in voltage or current is detected on any side of the power transformer to be tested, returning to the step of synchronously collecting a first positive-sequence phase voltage vector and a first positive-sequence line current vector of a first winding at an inlet, a second positive-sequence phase voltage vector and a second positive-sequence line current vector of a second winding at an outlet, and a third positive-sequence phase voltage vector and a third positive-sequence line current vector of a third winding at an outlet of the power transformer to be tested, to obtain a changed first reduced-calculated positive-sequence phase voltage vector, a changed first reduced-calculated positive-sequence line current vector, a changed second reduced-calculated positive-sequence phase voltage vector, a changed second reduced-calculated positive-sequence line current vector, a changed third reduced-calculated positive-sequence phase voltage vector, and a changed third reduced-calculated positive-sequence line current vector;

[0015] Obtaining an equivalent circuit of the transformer excitation complex impedance branch at the headend, and determining a first winding complex impedance of the first winding, a second winding complex impedance of the second winding, and a third winding complex impedance of the third winding based on the first restored positive-sequence phase voltage vector, the second restored positive-sequence phase voltage vector, the second restored positive-sequence line current vector, the third restored positive-sequence phase voltage vector, the third restored positive-sequence line current vector, the changed first restored positive-sequence phase voltage vector, the changed second restored positive-sequence phase voltage vector, the changed second restored positive-sequence line current vector, the changed third restored positive-sequence phase voltage vector, and the changed third restored positive-sequence line current vector;

[0016] Obtain an equivalent circuit of the transformer excitation complex impedance branch at the head end, and determine the excitation complex impedance of the power transformer to be tested based on the first restored positive-sequence phase voltage vector, the first restored positive-sequence line current vector, the second restored positive-sequence line current vector, and the third restored positive-sequence line current vector, or based on the changed first restored positive-sequence phase voltage vector, the changed first restored positive-sequence line current vector, the changed second restored positive-sequence line current vector, and the changed third restored positive-sequence line current vector.

[0017] Optionally, the step of sequentially returning 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 returned positive-sequence phase voltage vector, a first returned positive-sequence line current vector, a second returned positive-sequence phase voltage vector, a second returned positive-sequence line current vector, a third returned positive-sequence phase voltage vector, and a third returned positive-sequence line current vector comprises:

[0018] Using the formula Determining the first normalized positive-sequence phase voltage vector, the first normalized positive-sequence line current vector, the second normalized positive-sequence phase voltage vector, the second normalized positive-sequence line current vector, the third normalized positive-sequence phase voltage vector, and the third normalized positive-sequence line current vector;

[0019] When i is 1, is the first calculated 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 a natural constant, j is an imaginary unit, is the angle by which the reference winding leads the first winding, is the first calculated positive sequence line current vector, is the first positive sequence line current vector; when i is 2, is the second calculated 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 calculated positive sequence line current vector, is the second positive sequence line current vector; when i is 3, is the third calculated 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 calculated positive sequence line current vector, is the third positive sequence line current vector.

[0020] Optionally, obtaining an equivalent circuit of the transformer excitation complex impedance branch at the headend, determining a first winding complex impedance of the first winding, a second winding complex impedance of the second winding, and a third winding complex impedance of the third winding based on the first restored positive-sequence phase voltage vector, the second restored positive-sequence phase voltage vector, the second restored positive-sequence line current vector, the third restored positive-sequence phase voltage vector, the third restored positive-sequence line current vector, the changed first restored positive-sequence phase voltage vector, the changed second restored positive-sequence phase voltage vector, the changed second restored positive-sequence line current vector, the changed third restored positive-sequence phase voltage vector, and the changed third restored positive-sequence line current vector, includes:

[0021] Obtain an equivalent circuit of the transformer excitation complex impedance branch at the head end, and write a first equation based on the first calculated positive-sequence phase voltage vector, the second calculated positive-sequence phase voltage vector, the second calculated positive-sequence line current vector, the third calculated positive-sequence line current vector, the first winding complex impedance of the first winding, and the second winding complex impedance of the second winding;

[0022] Writing a second equation based on the second calculated positive-sequence phase voltage vector, the second calculated positive-sequence line current vector, the third calculated positive-sequence phase voltage vector, the third calculated positive-sequence line current vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding;

[0023] Writing a third equation based on the changed first normalized positive-sequence phase voltage vector, the changed second normalized positive-sequence phase voltage vector, the changed second normalized positive-sequence line current vector, the changed third normalized positive-sequence line current vector, the first winding complex impedance of the first winding, and the second winding complex impedance of the second winding;

[0024] A fourth equation is written based on the changed second calculated positive-sequence phase voltage vector, the changed second calculated positive-sequence line current vector, the changed third calculated positive-sequence phase voltage vector, the changed third calculated positive-sequence line current vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding;

[0025] Take any three equations from the first equation, the second equation, the third equation, and the fourth equation to form a system of equations, and solve 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.

[0026] Optionally, the first equation is

[0027] The second equation is

[0028] The third equation is

[0029] The fourth equation is

[0030] Wherein, Z1 is the complex impedance of the first winding, is the first calculated positive sequence phase voltage vector, is the second calculated positive sequence phase voltage vector, is the second calculated positive sequence line current vector after the change, is the first calculated positive sequence phase voltage vector after the change, is the second calculated positive sequence phase voltage vector after the change, is the second calculated positive sequence line current vector, is the third calculated positive sequence line current vector, is the third calculated positive sequence line current vector after the change, k BH is the rated voltage ratio between the reference winding and the high-voltage winding of the power transformer to be tested, Z2 is the complex impedance of the second winding, is the third calculated positive sequence phase voltage vector, is the third calculated positive-sequence phase voltage vector after the change, and Z3 is the third winding complex impedance.

[0031] Optionally, obtaining an equivalent circuit of the transformer excitation complex impedance branch at the head end, and determining the excitation complex impedance of the power transformer to be tested based on the first restored positive-sequence phase voltage vector, the first restored positive-sequence line current vector, the second restored positive-sequence line current vector, and the third restored positive-sequence line current vector, or based on the changed first restored positive-sequence phase voltage vector, the changed first restored positive-sequence line current vector, the changed second restored positive-sequence line current vector, and the changed third restored positive-sequence line current vector, includes:

[0032] Using the formula determining the excitation complex impedance;

[0033] Among them, Z m is the excitation complex impedance, is the first calculated positive sequence phase voltage vector, is the first calculated positive sequence line current vector, is the second calculated positive sequence line current vector, is the third calculated positive sequence line current vector, is the first calculated positive sequence phase voltage vector after the change, is the first calculated positive sequence line current vector after the change, is the second calculated positive sequence line current vector after the change, is the third calculated positive sequence line current vector after the change.

[0034] Optionally, the method further includes:

[0035] The load loss, impedance voltage percentage, no-load loss and no-load current percentage of the power transformer to be tested are determined according to the first winding complex impedance, the second winding complex impedance, the third winding complex impedance and the excitation complex impedance.

[0036] Optionally, determining the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer to be tested based on the first winding complex impedance, the second winding complex impedance, the third winding complex impedance, and the excitation complex impedance includes:

[0037] Using the formula Determining the load loss, impedance voltage percentage, no-load loss and no-load current percentage of the power transformer to be tested;

[0038] Among them, P ij is the load loss between the i-th winding and the j-th winding of the power transformer to be tested, and its unit is kW, real() is the real part function, and Z i is the value of the complex impedance of the i-th winding calculated by converting the reference winding to the nameplate parameters, Z j is the value of the complex impedance of the jth winding calculated by converting the reference winding to the nameplate parameters, S N is the rated capacity of the power transformer to be tested, in kVA, U N is the rated voltage of the transformer high voltage winding, in kV, U ij % is the impedance voltage percentage between the i-th winding and the j-th winding of the power transformer to be tested, imag() is the imaginary part function, P0 is the no-load loss, its unit is kW, and I0% is the no-load current percentage.

[0039] Optionally, the method further includes:

[0040] Determining whether the power transformer to be tested has an abnormality based on a comparison result between the first winding complex impedance, the second winding complex impedance, the third winding complex impedance and corresponding reference complex impedance thresholds; and / or,

[0041] Determine whether the power transformer to be tested has an abnormality based on the comparison results between the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer to be tested and the corresponding load loss threshold, impedance voltage percentage threshold, no-load loss threshold, and no-load current percentage threshold.

[0042] To achieve the above-mentioned object, the present invention provides, in a second aspect, a device for online monitoring of complex impedance parameters of a power transformer using synchronous vectors, the device comprising a sensor module and a controller;

[0043] The sensor module is connected to the controller;

[0044] The sensor module is used to be connected to the three phases of the first winding at the input, the three phases of the second winding at the output, and the three phases of the third winding at the output of the power transformer to be tested, respectively, and to measure the first three-phase voltage and the second three-phase current of the first winding at the input, the second three-phase voltage and the second three-phase current of the second winding at the output, and the third three-phase voltage and the third three-phase current of the third winding at the output;

[0045] 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 of the first winding at the input, the second positive-sequence phase voltage vector and the second positive-sequence line current vector of the second winding at the output, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector of the third winding at the output, and execute the method described in any one of the first aspects.

[0046] 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;

[0047] The first voltage sensor and the first current sensor are respectively connected to the three phases of the first winding at the input, and are used to measure the first three-phase voltage and the first three-phase current;

[0048] The second voltage sensor and the second current sensor are respectively connected to the three phases of the second winding at the outlet, and are used to measure the second three-phase voltage and the second three-phase current;

[0049] The third voltage sensor and the third current sensor are used to be respectively connected to the three phases of the third winding at the outlet, and to measure the third three-phase voltage and the third three-phase current.

[0050] To achieve the above-mentioned object, the present invention provides, in a third aspect, a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a controller, the controller executes the method as described in any one of the first aspects.

[0051] To achieve the above-mentioned objectives, the present invention provides a computer device in a fourth aspect, comprising a memory and a controller, wherein the memory stores a computer program, and when the computer program is executed by the controller, the controller executes the method as described in any one of the first aspects.

[0052] The embodiment of the present invention has the following beneficial effects: the above method synchronously collects the first positive-sequence phase voltage vector and the first positive-sequence line current vector of the first winding at the inlet of the power transformer to be tested, the second positive-sequence phase voltage vector and the second positive-sequence line current vector of the second winding at the outlet, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector of the third winding at the outlet; 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 converted to the reference winding to obtain the first converted positive-sequence phase voltage vector, the first converted positive-sequence line current vector, the second positive-sequence line current vector, the third positive-sequence phase voltage vector and the third positive-sequence line current vector. The 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 calculated, wherein the reference winding is any one of the first winding, the second winding and the third winding; when it is detected that the voltage or current on any side of the power transformer to be tested changes, the step of synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector of the first winding at the entrance of the power transformer to be tested, the second positive-sequence phase voltage vector and the second positive-sequence line current vector of the second winding at the exit, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector of the third winding at the exit of the power transformer to be tested is returned to obtain the changed first positive-sequence phase voltage vector and the first positive-sequence line current vector of the first winding at the entrance of the power transformer to be tested, The positive-sequence phase voltage vector, the first returned positive-sequence line current vector after the change, the second returned positive-sequence phase voltage vector after the change, the second returned positive-sequence line current vector after the change, the third returned positive-sequence phase voltage vector after the change and the third returned positive-sequence line current vector after the change are obtained; the equivalent circuit of the transformer excitation complex impedance branch at the head end is obtained, and the first returned positive-sequence phase voltage vector, the second returned positive-sequence phase voltage vector, the second returned positive-sequence line current vector, the third returned positive-sequence phase voltage vector, the third returned positive-sequence line current vector, the first returned positive-sequence phase voltage vector after the change, the second returned positive-sequence phase voltage vector after the change, the second returned positive-sequence line current vector, and the changed positive-sequence line current vector are obtained. 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 are determined based on the third calculated positive-sequence phase voltage vector and the changed third calculated positive-sequence line current vector; an equivalent circuit of the transformer excitation complex impedance branch at the head end is obtained, and the excitation complex impedance of the power transformer to be tested is determined based on the first calculated positive-sequence phase voltage vector, the first calculated positive-sequence line current vector, the second calculated positive-sequence line current vector, and the third calculated positive-sequence line current vector, or based on the changed first calculated positive-sequence phase voltage vector, the changed first calculated positive-sequence line current vector, the changed second calculated positive-sequence line current vector, and the changed third calculated positive-sequence line current vector;That is, it is possible to monitor the complex impedance parameters of the power transformer while it is operating. This means that real-time online monitoring of the complex impedance parameters of the transformer can be achieved without power outages. This allows real-time online monitoring of the operating status of the power transformer and risk assessment based on the complex impedance parameters, effectively resolving the power outage issue encountered in existing technologies. Furthermore, because this method uses positive-sequence variables before and after voltage or current changes to calculate the complex impedance parameters, the calculated complex impedance parameters are virtually error-free and highly accurate. Furthermore, the method is not subject to limitations imposed by test conditions. Furthermore, this method can detect changes in transformer parameters early, preventing the long-term accumulation of minor faults and thus avoiding the impact of major faults on the power system. This method plays an important role in detecting early-stage faults in AC transformers and converter transformers and ensuring the safe and stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0054] in:

[0055] Figure 1 Schematic diagram of a method for monitoring complex impedance parameters of a power transformer in an embodiment of the present application;

[0056] Figure 2 Schematic diagram of the equivalent circuit of the power transformer to be tested in an embodiment of the present application;

[0057] Figure 3 Schematic diagram of an equivalent transformation diagram corresponding to the equivalent circuit of the power transformer to be tested in an embodiment of the present application;

[0058] Figure 4 This is a schematic diagram of a complex impedance parameter monitoring device for a power transformer according to an embodiment of the present application;

[0059] Figure 5 This is another schematic diagram of a complex impedance parameter monitoring method for a power transformer according to an embodiment of the present application;

[0060] Figure 6 1 is a diagram of the internal structure of a computer device in some embodiments. DETAILED DESCRIPTION

[0061] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0062] Power transformers, as critical components of the power grid, have always been a key concern for the power industry. Transformer windings, a component prone to failure, pose a significant challenge to the stable operation of the power grid. Surveys have shown that over 20% of large transformers in power systems subjected to high current surges experience winding deformation. Further data reveals that among unplanned outages of transformers above 220 kV in my country, winding problems account for a significant portion of the downtime: 79.49% for 220 kV transformers and 98.92% for 500 kV transformers. Mechanical deformation of windings caused by electrodynamic forces has become a serious problem, accounting for as much as 70% of all winding accidents. Clearly, power transformer winding failures pose a significant threat to the safe operation of the power grid.

[0063] To meet this challenge, real-time understanding of transformer operating status and preventing sudden major equipment failures and grid incidents have become essential requirements for building a new energy and power system. Externally, the public and the economy are increasingly demanding power supply, and national pressure on safety regulation and power supply reliability assessments is also increasing. Internally, power companies face significant grid operation risks and a mismatch between equipment scale and maintenance resources when overhauling transformers. The risk of an equipment asset wall is becoming increasingly prominent, and maintenance work is about to enter a peak period.

[0064] When it comes to managing the safe operation of transformers, every step is crucial, from pre-commissioning type testing of new products to regular maintenance and online monitoring during operation. These inspection methods can generally be divided into two categories: one is inspection after the transformer has been shut down, and the other is online monitoring during operation. Transformer inspection targets are generally categorized into three main types: complex impedance parameters, oil quality, and internal partial discharge. These inspection targets each correspond to different parameters within the transformer and are not interchangeable. However, power outage inspections not only cause significant economic losses to the power grid but are also impractical to perform frequently in practice. Furthermore, oil-gas and partial discharge detection are susceptible to interference, have complex criteria, and present numerous challenges in engineering practice.

[0065] Currently, the power industry urgently needs a monitoring method that is highly reliable, easy to implement, and economical to operate. This is especially true for winding faults, which account for the largest proportion of transformer failures. Short-circuit complex impedance testing has become a recognized mandatory inspection for transformers before they are connected to the grid. The National Quality Inspection Center stipulates that a transformer's short-circuit complex impedance must vary within 5% to be considered acceptable.

[0066] However, existing methods for measuring transformer complex impedance parameters all involve power outage testing, such as the frequency response method, the short-circuit complex impedance method, the high-voltage self-oscillation method proposed by the Yunnan Electric Power Research Institute, and traditional methods for measuring transformer no-load and short-circuit characteristics. Furthermore, traditional methods for measuring transformer no-load and short-circuit characteristics are limited by test conditions, which undoubtedly poses a huge hidden danger to the stable operation of the power grid.

[0067] Against this backdrop, real-time online monitoring of the complex impedance parameters of power transformers has become a pressing technical challenge. The patent "Device and Method for Online Identification of Power Transformer Winding Parameters (CN101261297B)" discloses online identification of winding complex impedance (i.e., the short-circuit complex impedance of the winding) using a recursive least squares method. However, this approach fails to achieve true real-time online monitoring in practical applications, and the calculated winding complex impedance parameters also suffer from significant errors.

[0068] In addition, although the existing online monitoring method of mechanical vibration can achieve 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 assessment is difficult to determine.

[0069] Therefore, how to monitor the complex impedance parameters of the transformer in real time online without power outages, 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.

[0070] 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 using a synchronous vector. The method calculates the complex impedance parameters by real-time acquisition of positive-sequence variables before and after voltage or current changes to solve the problems existing in the prior art. The specific implementation principle will be described in detail in the following embodiments.

[0071] In a first aspect, the present application provides a method for online synchronous vector monitoring of complex impedance parameters of a power transformer.

[0072] See also Figure 1 , is a schematic diagram of a method for online monitoring of complex impedance parameters of a power transformer using synchronous vectors according to an embodiment of the present application, the method comprising:

[0073] Step 110: Synchronously collect a first positive-sequence phase voltage vector and a first positive-sequence line current vector of a first winding at an inlet of the power transformer under test, a second positive-sequence phase voltage vector and a second positive-sequence line current vector of a second winding at an outlet, and a third positive-sequence phase voltage vector and a third positive-sequence line current vector of a third winding at an outlet.

[0074] The power transformer to be tested refers to a transformer that needs to be monitored online.

[0075] As for the method for determining the positive-sequence voltage and positive-sequence current, in some embodiments, the three-phase voltage and three-phase current of the first winding at the inlet, the three-phase voltage and three-phase current of the second winding at the outlet, and the three-phase voltage and three-phase current of the third winding at the outlet can be synchronously collected first, and then the first positive-sequence phase voltage vector and the first positive-sequence line current vector of the first winding at the inlet are determined according to the three-phase voltage and three-phase current of the first winding at the inlet, the second positive-sequence phase voltage vector and the second positive-sequence line current vector of the second winding at the outlet are determined according to the three-phase voltage and three-phase current of the second winding at the outlet, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector of the third winding at the outlet are determined according to the three-phase voltage and three-phase current of the third winding at the outlet.

[0076] Step 120: 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 converted to the reference winding to obtain the first converted positive-sequence phase voltage vector, the first converted positive-sequence line current vector, the second converted positive-sequence phase voltage vector, the second converted positive-sequence line current vector, the third converted positive-sequence phase voltage vector and the third converted positive-sequence line current vector, where the reference winding is any one of the first winding, the second winding and the third winding.

[0077] It should be noted that the present application converts the positive-sequence phase voltage vector and positive-sequence line current vector of each winding to the same reference reference, namely the reference winding, to ensure that the parameters of all windings are processed under the same reference conditions, thereby improving the accuracy and consistency of subsequent processing.

[0078] Regarding the determination method of the reference calculation, in some embodiments, 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 can be sequentially referenced to the reference winding based on the rated voltage ratio between each winding and the reference winding, as well as the angular relationship, to obtain the first referenced positive-sequence phase voltage vector, the first referenced positive-sequence line current vector, the second referenced positive-sequence phase voltage vector, the second referenced positive-sequence line current vector, the third referenced positive-sequence phase voltage vector and the third referenced positive-sequence line current vector.

[0079] Step 130: When it is detected that the voltage or current on any side of the power transformer to be tested changes, return to the step of synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector of the first winding at the inlet, the second positive-sequence phase voltage vector and the second positive-sequence line current vector of the second winding at the outlet, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector of the third winding at the outlet of the power transformer to be tested, so as to obtain the changed first restored positive-sequence phase voltage vector, the changed first restored positive-sequence line current vector, the changed second restored positive-sequence phase voltage vector, the changed second restored positive-sequence line current vector, the changed third restored positive-sequence phase voltage vector, and the changed third restored positive-sequence line current vector.

[0080] Regarding the method for determining whether the voltage or current on any side of the power transformer to be tested has changed, in some embodiments, the apparent power output by the power transformer to be tested can be monitored, and when the rate of change between the apparent power output by the power transformer to be tested at a current moment and the apparent power output at a previous moment is greater than a first preset percentage, it is determined that the voltage or current on any side of the power transformer to be tested has changed; wherein the first preset percentage can be obtained and set by an operator based on a large amount of experience, experiments or statistics, and of course, can also be set by the operator according to actual needs.

[0081] In some embodiments, preferably, the first preset percentage can be set to any percentage between 0.1% and 10%, or set to a range between 0.1% and 10%.

[0082] Step 140: Obtain an equivalent circuit of the transformer excitation complex impedance branch at the head end, and determine 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 based on the first calculated positive-sequence phase voltage vector, the second calculated positive-sequence phase voltage vector, the second calculated positive-sequence line current vector, the third calculated positive-sequence phase voltage vector, the third calculated positive-sequence line current vector, the changed first calculated positive-sequence phase voltage vector, the changed second calculated positive-sequence phase voltage vector, the changed second calculated positive-sequence line current vector, the changed third calculated positive-sequence phase voltage vector, and the changed third calculated positive-sequence line current vector.

[0083] It should be noted that since the complex impedance of the winding is proportional to both the voltage and the current, and changes in voltage or current will directly affect the voltage and current in the winding, in some embodiments, the present application determines the complex impedance of the winding by real-time acquisition of positive-sequence variables before and after the voltage or current changes.

[0084] Step 150: Obtain an equivalent circuit of the transformer excitation complex impedance branch at the head end, and determine the excitation complex impedance of the power transformer to be tested based on the first calculated positive-sequence phase voltage vector, the first calculated positive-sequence line current vector, the second calculated positive-sequence line current vector, and the third calculated positive-sequence line current vector, or based on the changed first calculated positive-sequence phase voltage vector, the changed first calculated positive-sequence line current vector, the changed second calculated positive-sequence line current vector, and the changed third calculated positive-sequence line current vector.

[0085] Similarly, since the excitation complex impedance of the power transformer to be tested is also proportional to the voltage and current, and 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 real-time acquisition of positive-sequence variables before and after the voltage or current changes.

[0086] For examples, see Figure 2 , is a schematic diagram of an equivalent circuit diagram of the power transformer to be tested in an embodiment of the present application, and the schematic diagram shows r GT is the resistance corresponding to the excitation conductance of the power transformer to be measured, x Br is the reactance corresponding to the magnetizing susceptance of the power transformer to be tested, R1, R2, and R3 are the winding resistances corresponding to the complex impedances of the windings from the 1st winding to the 3rd winding, and X1, X2, and X3 are the winding reactances corresponding to the complex impedances of the windings from the 1st winding to the 3rd winding (i.e., the complex impedance of the winding includes both the winding resistance and the winding reactance). Figure 3 , is a schematic diagram of an equivalent transformation diagram corresponding to the equivalent circuit diagram of the power transformer to be tested in the embodiment of the present application, which shows I m1 is the current in the loop where Z1 and Z2 are located, I m2 is the current in the loop where Z2 and Z3 are located.

[0087] In an embodiment of the present application, by real-time acquisition of positive-sequence variables before and after voltage or current changes to calculate complex impedance parameters, the complex impedance parameters of the transformer can be monitored in the operating state of the power transformer, that is, real-time online monitoring of the complex impedance parameters of the transformer can be achieved without power outage, so that the operating state of the power transformer can be monitored online in real time based on the complex impedance parameters and risk assessment can be performed, effectively solving the problem of power outage required in the prior art. Moreover, since this method uses positive-sequence variables before and after voltage or current changes to calculate the complex impedance parameters, the calculated complex impedance parameters are almost error-free and have a high accuracy rate. At the same time, there is no problem of being restricted by test conditions. Moreover, this method of the present application can detect changes in transformer parameters as early as possible, prevent the long-term accumulation of minor faults, and thus avoid the impact of major faults on the power system. It plays an important role in detecting early transformer faults and ensuring the safe and stable operation of the power system.

[0088] In addition, the 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 that preventive maintenance measures can be taken to avoid power grid accidents caused by sudden major equipment failures, significantly improving the operational reliability and stability of the power grid; compared with traditional power outage maintenance, the present application does not require power outages for monitoring, reducing the economic losses caused by power outages, while also reducing the inconvenience caused to the power grid and users by frequent power outages for maintenance. In addition, real-time monitoring can promptly detect and handle potential faults, avoiding more expensive repair and replacement costs caused by fault expansion; by real-time monitoring of 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, and for transformers with abnormal parameter changes, maintenance can be arranged in advance, thereby optimizing the allocation of maintenance resources; real-time monitoring of the transformer operating status and timely detection and handling of winding faults help maintain the transformer in good working condition, thereby improving the power supply quality and stability of the power grid and meeting the needs of the people and the economic society for high-quality power supply.

[0089] In a feasible implementation, step 120 in the above embodiment, sequentially returning 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 returned positive-sequence phase voltage vector, the first returned positive-sequence line current vector, the second returned positive-sequence phase voltage vector, the second returned positive-sequence line current vector, the third returned positive-sequence phase voltage vector, and the third returned positive-sequence line current vector, includes:

[0090] Using the formula Determining a first normalized positive-sequence phase voltage vector, a first normalized positive-sequence line current vector, a second normalized positive-sequence phase voltage vector, a second normalized positive-sequence line current vector, a third normalized positive-sequence phase voltage vector, and a third normalized positive-sequence line current vector;

[0091] When i is 1, is the first calculated 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 a natural constant, j is an imaginary unit, The angle at which the reference winding leads the first winding, is the first normalized positive sequence line current vector, is the first positive sequence line current vector; when i is 2, is the second calculated 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, The angle at which the reference winding leads the second winding, is the second normalized positive sequence line current vector, is the second positive sequence line current vector; when i is 3, is the third calculated 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, The angle at which the reference winding leads the third winding is is the third calculated positive sequence line current vector, is the third positive sequence line current vector.

[0092] It should be noted that if the winding to be calculated is the same as the reference winding, then k Bi , equal to 1, is equal to 0, equal equal It is understandable that since the winding to be calculated is the same as the reference winding, the rated voltage and angle relationship are the same. Therefore, k Bi , equal to 1, Equal to 0, and then equal equal

[0093] In the embodiments of the present application, by providing clear formulas and methods for winding reduction, not only the accuracy and consistency of the reduction are improved, but also the reduction process is simplified, and the development of real-time monitoring and dynamic analysis as well as intelligent operation and maintenance is supported, thereby promoting the safe and stable operation of the power grid and the improvement of the economic benefits of power companies.

[0094] It can be understood that improving the accuracy and consistency of the reduction calculation: by using clear formulas to reduce the positive-sequence phase voltage vector and positive-sequence line current vector of each winding to the reference winding, the accuracy and consistency of the reduction process can be ensured. This accuracy is crucial for the subsequent calculation of the winding complex impedance parameters, because the accurate calculation of the winding complex impedance depends on accurate voltage and current data; simplifying the reduction process: the formula includes the rated voltage ratio and angle relationship between the windings. These parameters are usually known during the transformer design and manufacturing process. Therefore, using these formulas for reduction can greatly simplify the reduction process and reduce the calculation complexity and time cost; 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, which means that accurate winding complex impedance parameters can be obtained in real time, and risk assessment and preventive maintenance can be performed based on these parameters, thereby improving the operational reliability and stability of the power grid.

[0095] In a feasible implementation, step 140 in the above embodiment obtains the equivalent circuit of the transformer excitation complex impedance branch at the head end, and obtains the equivalent circuit of the transformer excitation complex impedance branch at the head end according to the first restored positive-sequence phase voltage vector, the second restored positive-sequence phase voltage vector, the second restored positive-sequence line current vector, the third restored positive-sequence phase voltage vector, the third restored positive-sequence line current vector, the changed first restored positive-sequence phase voltage vector, the changed second restored positive-sequence phase voltage vector, the changed second restored positive-sequence line current vector, the changed third restored positive-sequence phase voltage vector and the transformer The method comprises the following steps: obtaining an equivalent circuit of the transformer excitation complex impedance branch at the head end, and writing a first equation according to the first calculated positive-sequence phase voltage vector, the second calculated positive-sequence phase voltage vector, the second calculated positive-sequence line current vector, the third calculated positive-sequence line current vector, the first winding complex impedance of the first winding, and the second winding complex impedance of the second winding; and writing a first equation according to the second calculated positive-sequence phase voltage vector, the second calculated positive-sequence phase voltage vector, the second calculated positive-sequence line current vector, the third calculated positive-sequence line current vector, the first winding complex impedance of the first winding, and the second winding complex impedance of the second winding. The second equation is written based on the voltage vector, the second calculated positive-sequence line current vector, the third calculated positive-sequence phase voltage vector, the third calculated positive-sequence line current vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding; the third equation is written based on the changed first calculated positive-sequence phase voltage vector, the changed second calculated positive-sequence phase voltage vector, the changed second calculated positive-sequence line current vector, the changed third calculated positive-sequence line current vector, the first winding complex impedance of the first winding, and the second winding complex impedance of the second winding; The fourth equation is written based on the changed second calculated positive-sequence phase voltage vector, the changed second calculated positive-sequence line current vector, the changed third calculated positive-sequence phase voltage vector, the changed third calculated positive-sequence line current vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding; any three equations from the first equation, the second equation, the third equation, and the fourth equation are selected to form a system of equations, and 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 are solved.

[0096] In an embodiment of the present application, by utilizing the calculated positive-sequence phase voltage vector and the calculated positive-sequence line current vector before and after the voltage or current changes, the complex impedance parameters of each winding can be calculated more accurately. This method takes into account the impact of voltage or current changes on the winding voltage and current, thereby improving the accuracy of the calculation.

[0097] In addition, this method can perform calculations based on real-time collected data, thereby supporting online monitoring of transformers, which helps to promptly detect abnormal changes in winding parameters and conduct risk assessments, thereby taking corresponding preventive maintenance measures; real-time monitoring of the complex impedance parameters of transformer windings helps to promptly detect and deal with potential faults, preventing the expansion of faults and causing greater impact on the power grid, which helps to improve the operational reliability and stability of the power grid and meet the needs of the people and the economic society for high-quality power supply.

[0098] In a feasible implementation, the first equation in the above embodiment is

[0099] The second equation is

[0100] The third equation is

[0101] The fourth equation is

[0102] Where Z1 is the complex impedance of the first winding, is the first calculated positive sequence phase voltage vector, is the second calculated positive sequence phase voltage vector, is the second calculated positive sequence line current vector after the change, is the first calculated positive sequence phase voltage vector after the change, is the second calculated positive sequence phase voltage vector after the change, is the second normalized positive sequence line current vector, is the third calculated positive sequence line current vector, is the third calculated positive sequence line current vector after the change, k BH is the rated voltage ratio between the reference winding and the high-voltage winding of the power transformer to be tested, Z2 is the complex impedance of the second winding, is the third calculated positive sequence phase voltage vector, is the third calculated positive sequence phase voltage vector after change, and Z3 is the third winding complex impedance.

[0103] In an embodiment of the present application, a method for determining the complex impedance parameters of the winding by using a specific formula using the calculated positive-sequence phase voltage vector and the calculated positive-sequence line current vector before and after the voltage or current changes has shown significant beneficial effects in improving calculation accuracy, enhancing real-time monitoring capabilities, optimizing grid operation reliability, reducing maintenance costs, and meeting high-quality power supply needs. This is of great significance for realizing online monitoring of transformer complex impedance parameters and ensuring safe and stable operation of the power system.

[0104] It can be understood that improving the calculation accuracy: by using precise mathematical formulas to calculate, the influence of voltage or current changes on winding voltage and current is taken into account, so that the complex impedance parameters of each winding can be calculated more accurately, avoiding errors caused by inconsistent benchmarks or simplified calculation processes, and improving the accuracy of complex impedance parameter calculations; enhancing real-time monitoring capabilities: this method is based on real-time collected data for calculation, supports online monitoring of transformers, can promptly detect abnormal changes in winding parameters, and conduct risk assessments, so as to take corresponding preventive maintenance measures; optimizing grid operation reliability: real-time monitoring of the complex impedance parameters of transformer windings helps to promptly detect And deal with potential faults to prevent the expansion of faults and cause greater impact on the power grid, which helps to maintain the good working condition of the transformer, thereby improving the power supply quality and stability of the power grid; reduce maintenance costs: through real-time monitoring, the maintenance plan of the transformer can be formulated more accurately. For transformers with stable parameters or small changes, the maintenance cycle can be appropriately extended, thereby optimizing the allocation of maintenance resources and reducing maintenance costs; meet the needs of high-quality power supply: real-time monitoring and accurate calculation of winding complex impedance parameters can help to timely discover and deal with winding faults, and ensure the safe and stable operation of the power system, which is of great significance to meeting the needs of the people and the economic society for high-quality power supply.

[0105] In addition, this method avoids the errors that may be caused by traditional power outage inspection methods and ensures the reliability of the winding complex impedance parameters.

[0106] In a feasible implementation, the method of determining the excitation complex impedance of the power transformer to be tested based on the first calculated positive-sequence phase voltage vector, the first calculated positive-sequence line current vector, the second calculated positive-sequence line current vector, and the third calculated positive-sequence line current vector, or based on the changed first calculated positive-sequence phase voltage vector, the changed first calculated positive-sequence line current vector, the changed second calculated positive-sequence line current vector, and the changed third calculated positive-sequence line current vector in the above embodiment includes:

[0107] Using the formula Determine the excitation complex impedance;

[0108] Among them, Z m is the complex impedance of the excitation, is the first calculated positive sequence phase voltage vector, is the first normalized positive sequence line current vector, is the second normalized positive sequence line current vector, is the third calculated positive sequence line current vector, is the first calculated positive sequence phase voltage vector after the change, is the first calculated positive sequence line current vector after the change, is the second calculated positive sequence line current vector after the change, is the third calculated positive sequence line current vector after the change.

[0109] In the embodiments of the present application, the implementation method of determining the excitation complex impedance by using a formula has shown significant beneficial effects in improving calculation accuracy, enhancing real-time monitoring capabilities, optimizing grid operation reliability, reducing maintenance costs, meeting high-quality power supply needs, simplifying the calculation process, and improving system flexibility. This is of great significance for realizing online monitoring of transformer complex impedance parameters and ensuring safe and stable operation of the power system.

[0110] It can be understood that the calculation accuracy is improved: by using precise mathematical formulas to calculate the excitation complex impedance, this method can fully consider the influence of voltage or current changes on the winding voltage and current, thereby more accurately calculating the excitation complex impedance parameters. This accuracy avoids errors caused by simplified calculations or inconsistent benchmarks, ensuring the accuracy of the excitation complex impedance calculation; enhance real-time monitoring capabilities: this method performs calculations based on real-time collected data, supports online monitoring of transformers, and can promptly detect abnormal transformer parameters by real-time monitoring of changes in excitation complex impedance, and conduct risk assessments, thereby taking corresponding preventive maintenance measures; optimize grid operation reliability: real-time monitoring of transformer excitation complex impedance helps to promptly detect and handle potential faults, prevent faults from expanding and causing greater impact on the grid, which helps to maintain the transformer in good working condition, thereby improving the power supply quality and stability of the grid; reduce Low maintenance cost: Through real-time monitoring of the excitation complex impedance, the maintenance plan of the transformer can be formulated more accurately. For transformers with stable parameters or small changes, the maintenance cycle can be appropriately extended, thereby optimizing the allocation of maintenance resources and reducing maintenance costs; meeting the needs of high-quality power supply: Real-time monitoring and accurate calculation of the excitation complex impedance parameters help to promptly detect and handle transformer faults and ensure 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; simplifying the calculation process: The formula directly uses the key positive-sequence voltage and current data before and after the voltage or current changes to calculate the excitation complex impedance, avoiding complex intermediate calculation steps, thereby simplifying the calculation process and improving calculation efficiency; improving system flexibility: This method does not rely on specific test conditions or equipment, and can perform real-time monitoring under normal operating conditions of the transformer, thereby improving the flexibility of the system.

[0111] In a feasible implementation, the method in the above embodiment also includes: determining the load loss, impedance voltage percentage, no-load loss and no-load current percentage of the power transformer to be tested based on the first winding complex impedance, the second winding complex impedance, the third winding complex impedance and the excitation complex impedance.

[0112] 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 tested, and then determine the load loss, impedance voltage percentage, no-load loss and no-load current percentage of the power transformer to be tested based on the rated voltage, rated capacity, and the complex impedance of the first winding, the complex impedance of the second winding, the complex impedance of the third winding and the excitation complex impedance.

[0113] In an embodiment 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 tested, not only is real-time online monitoring achieved without power outages, the accuracy and precision of the calculation of complex impedance parameters are improved, but also the accuracy and precision of the calculation of electrical parameters (such as load loss, impedance voltage percentage, no-load loss and no-load current percentage) are improved.

[0114] In a feasible implementation, the above embodiment determines the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer to be tested based on the first winding complex impedance, the second winding complex impedance, the third winding complex impedance, and the excitation complex impedance, including:

[0115] Using the formula Determine the load loss, impedance voltage percentage, no-load loss and no-load current percentage of the power transformer under test;

[0116] Among them, P ij is the load loss between the i-th winding and the j-th winding of the power transformer to be tested, its unit is kW, real() is the real part function, Z i is the complex impedance of the i-th winding, Z j is the complex impedance of the jth winding, S N is the rated capacity of the power transformer to be tested, in kVA, U N is the rated voltage of the reference winding, in kV, U ij % is the impedance voltage percentage between the i-th winding and the j-th winding of the power transformer to be tested, imag() is the imaginary part function, P0 is the no-load loss in kW, and I0% is the no-load current percentage.

[0117] In the embodiment of the present application, through a clear formula and the calculated complex impedance of the winding, combined with the rated capacity of the power transformer to be tested and the rated voltage of the reference winding, the load loss, impedance voltage percentage, no-load loss and no-load current percentage of the power transformer to be tested can be accurately calculated. This method avoids the errors that may be caused by power outage inspection in traditional methods, and improves the accuracy and precision of the calculation.

[0118] In addition, this method can be used for monitoring without power outages, and can obtain key electrical parameters such as load loss, impedance voltage percentage, no-load loss and no-load current percentage in real time when the transformer is in operation. This helps operation and maintenance personnel to understand the operating status of the transformer in a timely manner, take necessary preventive maintenance measures, and prevent sudden major equipment failures.

[0119] In a feasible implementation, the method in the above embodiment further includes: determining whether there is an abnormality in the power transformer to be tested based on the comparison results between the complex impedance of the first winding, the complex impedance of the second winding, and 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 tested based on the comparison results between the load loss and impedance voltage percentage between each winding from 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 and the corresponding no-load loss threshold and no-load current percentage threshold.

[0120] Among them, 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 obtained and set by the operator based on a large amount of experience, experiments or statistics. Of course, they can also be set by the operator according to actual needs.

[0121] 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 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 for the first time.

[0122] In other embodiments, it is also possible to determine whether the power transformer to be tested has an abnormality based on a comparison result between the change rate between the first winding complex impedance, the second winding complex impedance, the third winding complex impedance and the corresponding reference complex impedance threshold and a second preset percentage.

[0123] Specifically, if the rate of change between any one winding complex impedance and the corresponding reference complex impedance threshold is greater than a second preset percentage, it is determined that the power transformer to be tested has an abnormality.

[0124] In some embodiments, preferably, the second preset percentage can be set to any percentage between 10% and 30%, or set to a range between 10% and 30%.

[0125] In other embodiments, it is also possible to determine whether there is an abnormality in the power transformer to be tested based on the comparison results between the load loss between each winding from the first winding to the third winding, the impedance voltage percentage and the corresponding load loss threshold, the change rate between the impedance voltage percentage threshold and the third threshold percentage, and the comparison results between the no-load loss, no-load current percentage and the corresponding no-load loss threshold, the change rate between the no-load current percentage threshold and the third threshold percentage.

[0126] Specifically, if the rate of change between any one of the load loss, impedance voltage percentage, no-load loss and no-load current percentage and the corresponding load loss threshold, impedance voltage percentage threshold, no-load loss threshold and no-load current percentage threshold is greater than a third preset percentage, it is determined that there is an abnormality in the power transformer to be tested.

[0127] In some embodiments, preferably, the third preset percentage can be set to any one percentage between 5% and 20%, or set to a range between 5% and 20%.

[0128] In the embodiment of the present application, by adding the comparison of the winding complex impedance with the reference complex impedance threshold, the comparison of the load loss, the impedance voltage percentage, the no-load loss and the no-load current percentage with the corresponding thresholds, etc., the intelligence level of transformer operation and maintenance can be further improved, major equipment failures can be prevented, the safety of the power grid can be guaranteed, and the allocation of maintenance resources can be optimized, thereby promoting the safe and stable operation of the power grid and improving the economic benefits of power companies.

[0129] In a second aspect, the present application provides a device for online monitoring of complex impedance parameters of a power transformer using synchronous vectors.

[0130] See also Figure 4 , is a schematic diagram of a synchronous vector online monitoring device for complex impedance parameters of a power transformer in an embodiment of the present application, which includes a sensor module 410 and a controller 420.

[0131] The sensor module 410 is connected to the controller 420 .

[0132] In a feasible implementation, the sensor module 410 is used to be connected to the three phases of the first winding at the input, the three phases of the second winding at the output, and the three phases of the third winding at the output of the power transformer to be tested, respectively, and to measure the first three-phase voltage and the second three-phase current of the first winding at the input, the second three-phase voltage and the second three-phase current of the second winding at the output, and the third three-phase voltage and the third three-phase current of the third winding at the output; 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 of the first winding at the input, the second positive-sequence phase voltage vector and the second positive-sequence line current vector of the second winding at the output, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector of the third winding at the output, and execute any method as described in the first aspect.

[0133] In an embodiment of the present application, the device includes a sensor module 410 and a controller 420, which can collect positive-sequence variables before and after the voltage or current changes in real time to calculate complex impedance parameters, and monitor the complex impedance parameters of the transformer when the power transformer is in operation. 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 the operating status of the power transformer can be monitored online in real time based on the complex impedance parameters and risk assessment can be performed, effectively solving the problem of power outage required in the prior art. Since this method uses positive-sequence variables before and after the voltage or current changes to calculate the complex impedance parameters, the calculated complex impedance parameters are almost error-free and have a high accuracy rate. At the same time, there is no problem of being restricted by test conditions. In addition, this method of the present application can detect changes in transformer parameters as early as possible, prevent the long-term accumulation of minor faults, and thus avoid the impact of major faults on the power system. It plays an important role in detecting early transformer faults and ensuring the safe and stable operation of the power system.

[0134] based on Figure 4 , see Figure 5 , is another schematic diagram of an online monitoring device for synchronous vectors of complex impedance parameters of a power transformer in an 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.

[0135] In a feasible implementation, the first voltage sensor 411 and the first current sensor 414 are used to be respectively connected to the three phases of the first winding at the entrance, 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 phases of the second winding at the exit, 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 phases of the third winding at the exit, and to measure the third three-phase voltage and the third three-phase current.

[0136] In an 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, which can synchronously collect three-phase voltage and three-phase current, and ensure the accuracy and reliability of the data, which is crucial for the subsequent calculation of parameters such as winding complex impedance, load loss, impedance voltage percentage, no-load loss and no-load current percentage.

[0137] In addition, the device has a simple structure, is easy to operate, and has high practical value and promotion prospects.

[0138] It should be noted that the voltage and current in this application are in vector form; for example, the second normalized positive-sequence phase voltage vector was once measured to be -2.43-63.1ikV, and the second normalized positive-sequence line current vector was once measured to be -8.74-62.86iA.

[0139] In a third aspect, the present application further provides a computer-readable storage medium storing a computer program. When the computer program is executed by a controller, the controller executes a method for online monitoring of complex impedance parameters of a power transformer by a synchronous vector in the above-mentioned method embodiment.

[0140] In a fourth aspect, the present application further provides a computer device including a memory and a controller, wherein the memory stores a computer program. When the computer program is executed by the controller, the controller executes a method for online monitoring of complex impedance parameters of a power transformer by a synchronous vector in the above-mentioned method embodiment.

[0141] Figure 6 The internal structure diagram of the computer device in some embodiments is shown. The computer device can be a terminal, a server, or a gateway. Figure 6 As shown, the computer device includes a controller, a memory and a network interface connected through a system bus.

[0142] 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 the various steps in the above method embodiment. The internal memory may also store a computer program. When the computer program is executed by the controller, the controller can implement the various steps in the above method embodiment. It will be understood by those skilled in the art that Figure 6 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0143] Those skilled in the art will understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing related hardware through a computer program, and 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 embodiments of the above-mentioned methods.

[0144] Among them, any reference to memory, storage, database or other media used in the various 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. As an illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchl ink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0145] It should be noted that the technical features of the above embodiments can be combined in any manner and can be applied to a dual-winding transformer through simple transformation by those skilled in the art. To simplify the description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there are no contradictions in the combination of these technical features, they should be considered to be within the scope of this specification.

[0146] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for online monitoring of complex impedance parameters of power transformers by synchronous vectors, characterized in that: The method comprises: Synchronously collecting the first positive-sequence phase voltage vector and the first positive-sequence line current vector of the first winding of the power transformer under test at the inlet, the second positive-sequence phase voltage vector and the second positive-sequence line current vector of the second winding at the outlet, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector of the third winding at the outlet; 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 converted to a reference winding to obtain a first converted positive-sequence phase voltage vector, a first converted positive-sequence line current vector, a second converted positive-sequence phase voltage vector, a second converted positive-sequence line current vector, a third converted positive-sequence phase voltage vector, and a third converted positive-sequence line current vector, wherein the reference winding is any one of the first winding, the second winding, and the third winding; In the event that a change in voltage or current is detected on any side of the power transformer to be tested, returning to the step of synchronously collecting a first positive-sequence phase voltage vector and a first positive-sequence line current vector of a first winding at an inlet, a second positive-sequence phase voltage vector and a second positive-sequence line current vector of a second winding at an outlet, and a third positive-sequence phase voltage vector and a third positive-sequence line current vector of a third winding at an outlet of the power transformer to be tested, to obtain a changed first reduced-calculated positive-sequence phase voltage vector, a changed first reduced-calculated positive-sequence line current vector, a changed second reduced-calculated positive-sequence phase voltage vector, a changed second reduced-calculated positive-sequence line current vector, a changed third reduced-calculated positive-sequence phase voltage vector, and a changed third reduced-calculated positive-sequence line current vector; Obtaining an equivalent circuit of the transformer excitation complex impedance branch at the headend, and determining a first winding complex impedance of the first winding, a second winding complex impedance of the second winding, and a third winding complex impedance of the third winding based on the first restored positive-sequence phase voltage vector, the second restored positive-sequence phase voltage vector, the second restored positive-sequence line current vector, the third restored positive-sequence phase voltage vector, the third restored positive-sequence line current vector, the changed first restored positive-sequence phase voltage vector, the changed second restored positive-sequence phase voltage vector, the changed second restored positive-sequence line current vector, the changed third restored positive-sequence phase voltage vector, and the changed third restored positive-sequence line current vector; Obtain an equivalent circuit of the transformer excitation complex impedance branch at the head end, and determine the excitation complex impedance of the power transformer to be tested based on the first restored positive-sequence phase voltage vector, the first restored positive-sequence line current vector, the second restored positive-sequence line current vector, and the third restored positive-sequence line current vector, or based on the changed first restored positive-sequence phase voltage vector, the changed first restored positive-sequence line current vector, the changed second restored positive-sequence line current vector, and the changed third restored positive-sequence line current vector.

2. The method according to claim 1, characterized in that The step of sequentially returning 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 returned positive-sequence phase voltage vector, a first returned positive-sequence line current vector, a second returned positive-sequence phase voltage vector, a second returned positive-sequence line current vector, a third returned positive-sequence phase voltage vector, and a third returned positive-sequence line current vector comprises: Using the formula Determining the first normalized positive-sequence phase voltage vector, the first normalized positive-sequence line current vector, the second normalized positive-sequence phase voltage vector, the second normalized positive-sequence line current vector, the third normalized positive-sequence phase voltage vector, and the third normalized positive-sequence line current vector; When i is 1, is the first calculated 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 a natural constant, j is an imaginary unit, is the angle by which the reference winding leads the first winding, is the first calculated positive sequence line current vector, is the first positive sequence line current vector; when i is 2, is the second calculated 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 calculated positive sequence line current vector, is the second positive sequence line current vector; when i is 3, is the third calculated 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 calculated positive sequence line current vector, is the third positive sequence line current vector.

3. The method according to claim 1, characterized in that The step of obtaining an equivalent circuit of the transformer excitation complex impedance branch at the head end, and determining a first winding complex impedance of the first winding, a second winding complex impedance of the second winding, and a third winding complex impedance of the third winding according to the first restored positive-sequence phase voltage vector, the second restored positive-sequence phase voltage vector, the second restored positive-sequence line current vector, the third restored positive-sequence phase voltage vector, the third restored positive-sequence line current vector, the changed first restored positive-sequence phase voltage vector, the changed second restored positive-sequence phase voltage vector, the changed second restored positive-sequence line current vector, the changed third restored positive-sequence phase voltage vector, and the changed third restored positive-sequence line current vector, comprises: Obtain an equivalent circuit of the transformer excitation complex impedance branch at the head end, and write a first equation based on the first calculated positive-sequence phase voltage vector, the second calculated positive-sequence phase voltage vector, the second calculated positive-sequence line current vector, the third calculated positive-sequence line current vector, the first winding complex impedance of the first winding, and the second winding complex impedance of the second winding; Writing a second equation based on the second calculated positive-sequence phase voltage vector, the second calculated positive-sequence line current vector, the third calculated positive-sequence phase voltage vector, the third calculated positive-sequence line current vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding; Writing a third equation based on the changed first normalized positive-sequence phase voltage vector, the changed second normalized positive-sequence phase voltage vector, the changed second normalized positive-sequence line current vector, the changed third normalized positive-sequence line current vector, the first winding complex impedance of the first winding, and the second winding complex impedance of the second winding; A fourth equation is written based on the changed second calculated positive-sequence phase voltage vector, the changed second calculated positive-sequence line current vector, the changed third calculated positive-sequence phase voltage vector, the changed third calculated positive-sequence line current vector, the second winding complex impedance of the second winding, and the third winding complex impedance of the third winding; Take any three equations from the first equation, the second equation, the third equation, and the fourth equation to form a system of equations, and solve 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.

4. The method according to claim 3, characterized in that The first equation is The second equation is The third equation is The fourth equation is Wherein, Z1 is the complex impedance of the first winding, is the first calculated positive sequence phase voltage vector, is the second calculated positive sequence phase voltage vector, is the second calculated positive sequence line current vector after the change, is the first calculated positive sequence phase voltage vector after the change, is the second calculated positive sequence phase voltage vector after the change, is the second calculated positive sequence line current vector, is the third calculated positive sequence line current vector, is the third calculated positive sequence line current vector after the change, k BH is the rated voltage ratio between the reference winding and the high-voltage winding of the power transformer to be tested, Z2 is the complex impedance of the second winding, is the third calculated positive sequence phase voltage vector, is the third calculated positive-sequence phase voltage vector after the change, and Z3 is the third winding complex impedance.

5. The method according to claim 1, wherein The step of obtaining an equivalent circuit of the transformer excitation complex impedance branch at the head end, and determining the excitation complex impedance of the power transformer to be tested based on the first calculated positive-sequence phase voltage vector, the first calculated positive-sequence line current vector, the second calculated positive-sequence line current vector, and the third calculated positive-sequence line current vector, or based on the changed first calculated positive-sequence phase voltage vector, the changed first calculated positive-sequence line current vector, the changed second calculated positive-sequence line current vector, and the changed third calculated positive-sequence line current vector, comprises: Using the formula determining the excitation complex impedance; Among them, Z m is the excitation complex impedance, is the first calculated positive sequence phase voltage vector, is the first calculated positive sequence line current vector, is the second calculated positive sequence line current vector, is the third calculated positive sequence line current vector, is the first calculated positive sequence phase voltage vector after the change, is the first calculated positive sequence line current vector after the change, is the second calculated positive sequence line current vector after the change, is the third calculated positive sequence line current vector after the change.

6. The method according to claim 1, characterized in that The method further comprises: The load loss, impedance voltage percentage, no-load loss and no-load current percentage of the power transformer to be tested are determined according to the first winding complex impedance, the second winding complex impedance, the third winding complex impedance and the excitation complex impedance.

7. The method according to claim 6, characterized in that Determining the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer to be tested based on the first winding complex impedance, the second winding complex impedance, the third winding complex impedance, and the excitation complex impedance includes: Using the formula Determining the load loss, impedance voltage percentage, no-load loss and no-load current percentage of the power transformer to be tested; Among them, P ij is the load loss between the i-th winding and the j-th winding of the power transformer to be tested, and its unit is kW, real() is the real part function, and Z i is the value of the complex impedance of the i-th winding calculated by converting the reference winding to the nameplate parameters, Z j is the value of the complex impedance of the jth winding calculated by converting the reference winding to the nameplate parameters, S N is the rated capacity of the power transformer to be tested, in kVA, U N is the rated voltage of the transformer high voltage winding, in kV, U ij % is the impedance voltage percentage between the i-th winding and the j-th winding of the power transformer to be tested, imag() is the imaginary part function, P0 is the no-load loss, its unit is kW, and I0% is the no-load current percentage.

8. The method according to claim 1 or 6, characterized in that The method further comprises: Determining whether the power transformer to be tested has an abnormality based on a comparison result between the first winding complex impedance, the second winding complex impedance, the third winding complex impedance and corresponding reference complex impedance thresholds; and / or, Determine whether the power transformer to be tested has an abnormality based on the comparison results between the load loss, impedance voltage percentage, no-load loss, and no-load current percentage of the power transformer to be tested and the corresponding load loss threshold, impedance voltage percentage threshold, no-load loss threshold, and no-load current percentage threshold.

9. A device for online monitoring of complex impedance parameters of power transformers by synchronous vectors, 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 of the first winding at the input, the three phases of the second winding at the output, and the three phases of the third winding at the output of the power transformer to be tested, respectively, and to measure the first three-phase voltage and the second three-phase current of the first winding at the input, the second three-phase voltage and the second three-phase current of the second winding at the output, and the third three-phase voltage and the third three-phase current of the third winding at the output; 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 of the first winding at the input, the second positive-sequence phase voltage vector and the second positive-sequence line current vector of the second winding at the output, and the third positive-sequence phase voltage vector and the third positive-sequence line current vector of the third winding at the output, and perform the method described in 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 respectively connected to the three phases of the first winding at the input, 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 respectively connected to the three phases of the second winding at the outlet, 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 respectively connected to the three phases of the third winding at the outlet, and to measure the third three-phase voltage and the third three-phase current.

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