Distribution transformer electrical parameter complex frequency domain on-line monitoring method and related equipment

Abstract

The embodiment of the invention discloses a power distribution transformer electrical parameter complex frequency domain on-line monitoring method and related equipment, and the method comprises the steps: injecting a pilot frequency detection signal into a low-voltage side of a power distribution transformer, and synchronously measuring a pilot frequency zero-sequence voltage vector and a pilot frequency zero-sequence current vector outputted by the low-voltage side of the power distribution transformer, and a neutral point voltage vector of the low-voltage side; according to the pilot-frequency zero-sequence voltage vector, the pilot-frequency zero-sequence current vector and the neutral point voltage vector of the low-voltage side, the short-circuit complex impedance of the high-voltage side to the low-voltage side of the distribution transformer is calculated, and according to the pilot-frequency zero-sequence voltage vector, the pilot-frequency zero-sequence current vector and the neutral point voltage vector of the low-voltage side, the method only needs to install sensing equipment on the low-voltage side of the distribution transformer for data acquisition; the cost and the monitoring difficulty of the monitoring system are reduced; the conditions that the voltage and the load of the low-voltage side are required to change and the like are not required, the error between the obtained electrical parameters and the actual electrical parameters is reduced, the complex impedance parameters and the rated complex impedance under different frequencies are obtained, and a foundation is laid for fault amplitude-frequency domain diagnosis of the transformer winding.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer parameter online monitoring, and in particular to a complex frequency domain online monitoring method for electrical parameters of a distribution transformer and related equipment. Background Art

[0002] Short-circuit loss and load loss are important parameters of distribution transformers, representing their operating efficiency and performance. On the one hand, when short-circuit loss and load loss are excessively high, the transformer's energy conversion efficiency is low, resulting in energy waste. On the other hand, over the long term, distribution transformers are inevitably affected by the environment, external faults, and other factors, leading to parameter changes and even major defects, reducing reliability. Therefore, a transformer's short-circuit loss and load loss reflect its performance and health. Therefore, these parameters, such as short-circuit loss and load loss (DC resistance), must be tested during transformer grid entry and routine preventive testing.

[0003] Currently, parameters such as short-circuit loss and DC resistance (load loss) of distribution transformers are primarily measured through offline testing. For distribution transformers already in operation, these tests must be taken out of service, which is time-consuming, labor-intensive, and requires power outages, impacting power supply continuity. To address this, professionals have developed online transformer testing methods. These methods, through real-time testing of the distribution transformer's short-circuit resistance and short-circuit reactance (loss), monitor whether the transformer's electrical parameters, such as DC resistance and short-circuit reactance, have significantly changed. This allows them to determine whether the transformer's health meets operational requirements and prevent major failures.

[0004] The document "Research on Online Detection Methods for Distribution Transformer Losses and Capacity (Wu Xihong)" proposes to calculate the transformer's short-circuit loss and no-load loss by online detecting the voltage and current on both sides of the distribution transformer. However, on the one hand, this method measures the high-voltage side voltage and current during implementation, requiring the addition of high-voltage voltage and current sensing equipment (such as PT and CT). The cost of the high-voltage sensing equipment is comparable to that of the distribution transformer, resulting in a high implementation cost. On the other hand, this method requires that the primary side voltage of the distribution transformer remain essentially unchanged. However, since the primary side voltage inevitably fluctuates during actual operation, the measurement error is relatively large. Furthermore, this method is susceptible to the influence of harmonics and three-phase imbalance, further increasing the measurement error.

[0005] The papers "Online Detection Method for Distribution Transformer Short-Circuit Reactance Considering Asymmetric Loads (Chen Minyu)" and "An Improved Online Detection Method for Distribution Transformer Short-Circuit Reactance (Wang Minglin)" propose repeatedly collecting the three-phase voltage and current on the high-voltage side of the distribution transformer, as well as the low-voltage side, and the three-phase voltage and current on the low-voltage side, as well as the high-voltage side neutral point voltage offset, under varying loads to calculate the distribution transformer's short-circuit complex impedance. This method requires high-voltage voltage and current sensing equipment on the high-voltage side of the distribution transformer, resulting in high implementation costs. Furthermore, it relies on load fluctuations, resulting in poor real-time performance.

[0006] The patent "Online Monitoring Method and System for Transformer Resistance Parameters Based on Winding Temperature Changes (CN119246953A)" discloses calculating winding resistance using an oil temperature sensor and a simulation model. However, this method is an indirect measurement, relying on the accuracy of simulation results, the validity of fitting curves, and material limitations. It is difficult to implement and its accuracy is difficult to guarantee. Furthermore, this method can only calculate the winding resistance of the distribution transformer and cannot monitor short-circuit reactance parameters.

[0007] It can be seen that real-time monitoring of distribution transformer parameters is crucial to ensuring the safe operation of the power grid. Although the existing online monitoring technology has been improved, it still has problems such as high implementation cost, high difficulty, and large measurement errors. Summary of the Invention

[0008] In view of this, the present invention provides a method for online monitoring of electrical parameters of a distribution transformer in a complex frequency domain.

[0009] The specific technical solution of the first embodiment of the present invention is: a method for online monitoring of electrical parameters of a distribution transformer in a complex frequency domain, the method comprising: injecting an out-of-frequency detection signal into the low-voltage side of the distribution transformer; the out-of-frequency detection signal is an out-of-frequency detection voltage or an out-of-frequency detection current; synchronously obtaining an out-of-frequency zero-sequence voltage vector and an out-of-frequency zero-sequence current vector outputted by the low-voltage side of the distribution transformer, and synchronously obtaining a neutral point voltage vector on the low-voltage side of the distribution transformer; obtaining a first short-circuit complex impedance of the low-voltage side of the distribution transformer to the high-voltage side under out-of-frequency conditions based on the out-of-frequency zero-sequence voltage vector, the out-of-frequency zero-sequence current vector, and the neutral point voltage vector;

[0010] Convert the first short-circuit complex impedance to a second short-circuit complex impedance between the low-voltage side and the high-voltage side of the distribution transformer at the power frequency; obtain the rated voltage ratio of the distribution transformer at the current operating gear; and obtain the third short-circuit complex impedance between the high-voltage side and the low-voltage side of the distribution transformer based on the first short-circuit complex impedance, the second short-circuit complex impedance and the rated voltage ratio.

[0011] Preferably, the first short-circuit complex impedance includes a first short-circuit resistance and a first short-circuit reactance, and the second short-circuit complex impedance includes a second short-circuit resistance and a second short-circuit reactance; then, obtaining the third short-circuit complex impedance from the high-voltage side to the low-voltage side of the distribution transformer based on the first short-circuit complex impedance, the second short-circuit complex impedance and the rated voltage ratio includes: obtaining the third short-circuit complex impedance from the high-voltage side to the low-voltage side of the distribution transformer based on the first short-circuit resistance, the second short-circuit reactance and the rated voltage ratio.

[0012] Preferably, the injecting of an out-of-frequency detection signal into the low-voltage side of the distribution transformer includes: synchronously injecting the same out-of-frequency detection signal into the three phases on the low-voltage side of the distribution transformer at the neutral point zero sequence; or synchronously injecting different out-of-frequency detection signals into the three phases on the low-voltage side of the distribution transformer at the neutral point zero sequence; or synchronously injecting different out-of-frequency detection signals into the three phases on the low-voltage side of the distribution transformer at the three-phase zero sequence.

[0013] Preferably, when the same different-frequency detection signal is synchronously injected into the three phases on the low-voltage side of the distribution transformer at the neutral point zero sequence, the first short-circuit complex impedance is obtained using the following formula:

[0014]

[0015] Among them, Z fy21 is the first short-circuit complex impedance, is the heterofrequency zero-sequence voltage vector, is the heterofrequency zero-sequence current vector, is the neutral point voltage vector.

[0016] Preferably, when different out-of-frequency detection signals are synchronously injected into the three phases on the low-voltage side of the distribution transformer at the three-phase zero sequence, the first short-circuit complex impedance is obtained using the following formula:

[0017]

[0018] Among them, Z fy21 is the first short-circuit complex impedance, and are the voltage vectors of different phases in the heterofrequency zero-sequence voltage vector, and are the current vectors of different phases in the heterofrequency zero-sequence current vector, is the neutral point voltage vector.

[0019] Preferably, the second short-circuit complex impedance is obtained using the following formula:

[0020]

[0021] Among them, Zfg21 is the second short-circuit complex impedance, Z fy21 is the first short-circuit complex impedance, f y is the frequency difference, f g is the industrial frequency, real() is the real part function, and imag() is the imaginary part function.

[0022] Preferably, the obtaining of the heterofrequency zero-sequence voltage vector and the heterofrequency zero-sequence current vector outputted on the low-voltage side of the distribution transformer includes: synchronously obtaining the three-phase heterofrequency voltage vector and the three-phase heterofrequency current vector outputted on the low-voltage side of the distribution transformer; converting the three-phase heterofrequency voltage vector into the heterofrequency zero-sequence voltage vector, and converting the three-phase heterofrequency current vector into the heterofrequency zero-sequence current vector.

[0023] The specific technical solution of the second embodiment of the present invention is: a complex frequency domain online monitoring system for electrical parameters of a distribution transformer, the system comprising: an heterofrequency detection power supply, a single-phase coupling unit, a detection output switch, a detection bypass switch, a neutral point voltage sensing unit, a three-phase voltage sensing unit, a three-phase current sensing unit and a control and calculation unit; one end of the heterofrequency detection power supply is respectively connected to one end of the detection bypass switch and grounded, the other end of the heterofrequency detection power supply is connected to one end of the single-phase coupling unit, and the other end of the single-phase coupling unit is connected to one end of the detection output switch, The other end of the detection output switch, the other end of the detection bypass switch and one end of the neutral point voltage sensing unit are respectively connected to the neutral point of the distribution transformer, the other end of the neutral point voltage sensing unit is grounded, one end of the three-phase voltage sensing unit and one end of the three-phase current sensing unit are connected to the three-phase outgoing line of the distribution transformer, the other end of the three-phase voltage sensing unit and the other end of the three-phase current sensing unit are connected to the control and calculation unit; the different-frequency detection power supply is used to provide the distribution transformer with a single-phase coupling unit and the detection output switch. The heterofrequency detection signal is injected into the low-voltage side of the distribution transformer; the series branch composed of the detection bypass switch, the heterofrequency detection power supply, the single-phase coupling unit and the detection output switch is connected in parallel, and is used to ground the neutral point of the distribution transformer when the electrical parameters are not monitored; the neutral point voltage sensing unit is used to obtain the neutral point voltage vector of the low-voltage side of the distribution transformer; the three-phase voltage sensing unit is used to obtain the heterofrequency zero-sequence voltage vector output by the low-voltage side of the distribution transformer; the three-phase current sensing unit is used to obtain the heterofrequency zero-sequence current vector output by the low-voltage side of the distribution transformer; the control The control and calculation unit is used to perform the following steps: obtaining a first short-circuit complex impedance from the low-voltage side to the high-voltage side of the distribution transformer at an irregular frequency according to the irregular zero-sequence voltage vector, the irregular zero-sequence current vector, and the neutral point voltage vector; converting the first short-circuit complex impedance to a second short-circuit complex impedance from the low-voltage side to the high-voltage side of the distribution transformer at an operating frequency; obtaining a rated voltage ratio of the distribution transformer at a current operating gear; and obtaining a third short-circuit complex impedance from the high-voltage side to the low-voltage side of the distribution transformer according to the first short-circuit complex impedance, the second short-circuit complex impedance, and the rated voltage ratio.

[0024] The specific technical solution of the third embodiment of the present invention is: an online monitoring device for electrical parameters of a distribution transformer, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method described in any one of the first embodiments of the present application.

[0025] The specific technical solution of the fourth embodiment of the present invention is: a computer-readable storage medium storing a computer program, which, when executed by a processor, enables the processor to perform the steps of the method described in any one of the first embodiments of the present application.

[0026] Implementing the embodiments of the present invention will have the following beneficial effects:

[0027] The present invention injects an out-of-frequency detection signal into the low-voltage side of the distribution transformer, and obtains the out-of-frequency zero-sequence voltage vector, out-of-frequency zero-sequence current vector and the neutral point voltage vector of the low-voltage side output by the distribution transformer. Therefore, it is only necessary to install a sensor device on the low-voltage side of the distribution transformer to acquire data, and there is no need to install a sensor device on the high-voltage side. The sensor device installed on the low-voltage side has the advantage of low cost compared with the sensor device installed on the high-voltage side, thereby reducing the cost of the monitoring system; the short-circuit complex impedance of the high-voltage side to the low-voltage side of the distribution transformer is calculated based on the out-of-frequency zero-sequence voltage vector, the out-of-frequency zero-sequence current vector and the neutral point voltage vector of the low-voltage side, without requiring conditions such as changes in the voltage and load on the low-voltage side, thereby reducing the error between the obtained electrical parameters and the actual electrical parameters, and at the same time obtaining the complex impedance parameters and rated complex impedance at different frequencies, laying a foundation for amplitude-frequency domain diagnosis of transformer winding faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application 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 application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1 A flowchart of the steps of a complex frequency domain online monitoring method for electrical parameters of a distribution transformer;

[0030] Figure 2a The first embodiment of the position of the injection point of the heterofrequency detection signal;

[0031] Figure 2b A second embodiment of the position of the injection point of the heterofrequency detection signal;

[0032] Figure 2c A third embodiment of the position of the injection point of the heterofrequency detection signal;

[0033] Figure 3 This is the equivalent circuit diagram of the detection circuit of the complex frequency domain online monitoring method for the electrical parameters of the distribution transformer;

[0034] Figure 4aA schematic diagram of a first embodiment of the structure of a complex frequency domain online monitoring system for electrical parameters of a distribution transformer;

[0035] Figure 4b A schematic diagram of a second embodiment of the structure of a complex frequency domain online monitoring system for electrical parameters of a distribution transformer;

[0036] Figure 4c A schematic diagram of a second embodiment of the structure of a complex frequency domain online monitoring system for electrical parameters of a distribution transformer;

[0037] Figure 5 A diagram of the internal structure of a computer device;

[0038] Among them, 201, heterodyne frequency detection power supply; 202, single-phase coupling unit; 203, detection output switch; 204, detection bypass switch; 205, neutral point voltage sensing unit; 206, three-phase voltage sensing unit; 207, three-phase current sensing unit; 208, control and calculation unit; 209, three-phase coupling unit. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0040] The terms "first," "second," and the like in the specification, claims, and drawings of this application are used to distinguish between different objects, not to describe a particular order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or modules is not limited to the listed steps or modules but may optionally include steps or modules not listed, or may optionally include other steps or modules inherent to the process, method, product, or apparatus.

[0041] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0042] See also Figure 1, is a flowchart of a method for online monitoring of electrical parameters of a distribution transformer in a complex frequency domain in the first embodiment of the present application, to reduce the error between the obtained electrical parameters and the actual electrical parameters, the method comprising:

[0043] Step 101: inject an inter-frequency detection signal into the low-voltage side of the distribution transformer; the inter-frequency detection signal is an inter-frequency detection voltage or an inter-frequency detection current;

[0044] Step 102: Obtain the zero-sequence voltage vector of the low-voltage side output of the distribution transformer. and the zero-sequence current vector And obtain the neutral point voltage vector of the low voltage side of the distribution transformer

[0045] Step 103: According to the different-frequency zero-sequence voltage vector The different-frequency zero-sequence current vector and the neutral point voltage vector Obtain the first short-circuit complex impedance Z of the low-voltage side to the high-voltage side of the distribution transformer under different frequencies fy21 ;

[0046] Step 104: Restore the first short circuit impedance Z fy21 The second short-circuit complex impedance Z of the low-voltage side to the high-voltage side of the distribution transformer converted to the power frequency fg21 ;

[0047] Step 105: Obtain the rated voltage ratio of the distribution transformer at the current operating gear;

[0048] Step 106: According to the first short-circuit complex impedance Z fy21 The second short-circuit complex impedance Z fg21 The third short-circuit complex impedance between the high-voltage side and the low-voltage side of the distribution transformer is obtained by comparing the rated voltage to the rated voltage.

[0049] Specifically, an out-of-frequency detection power supply is used to inject an out-of-frequency detection signal into the low-voltage side of the distribution transformer. The frequency of the out-of-frequency detection signal can be 30Hz to 2000Hz and is not equal to the power frequency. When the out-of-frequency detection power supply is a current source, the injected out-of-frequency current amplitude is 0.1% to 10% of the rated current on the low-voltage side. When the out-of-frequency monitoring power supply is a voltage source, the injected out-of-frequency voltage amplitude is 0.1% to 10% of the rated voltage on the low-voltage side. After injecting the out-of-frequency detection signal into the low-voltage side of the distribution transformer, the out-of-frequency zero-sequence voltage vector outputted by the low-voltage side of the distribution transformer is obtained. and the zero-sequence current vector and the neutral point voltage vector on the low voltage side of the distribution transformer Thus, the first short-circuit complex impedance Z of the low-voltage side to the high-voltage side is obtained fy21By using these vector data, the short-circuit complex impedance of the transformer can be calculated more accurately, which is one of the important indicators for evaluating transformer performance. The magnitude of the short-circuit complex impedance reflects the electrical characteristics of the transformer under short-circuit fault conditions and is crucial to the design and operational stability of the transformer. fy21 The second short-circuit complex impedance Z between the low-voltage side and the high-voltage side of the distribution transformer converted to the power frequency fg21 , the power frequency is the standard frequency of the power system. Converting the test results under different frequencies to the power frequency can make the monitoring results closer to the actual operating conditions, thereby improving the accuracy and reliability of the test. Obtain the rated voltage ratio of the distribution transformer under the current operating gear, according to the first short-circuit complex impedance Z fy21 , the second short-circuit complex impedance Z fg21 The third short-circuit complex impedance of the high-voltage side to the low-voltage side of the distribution transformer is obtained by comparing the rated voltage ratio. The third short-circuit complex impedance is used to obtain the final monitoring result of the distribution transformer.

[0050] The method in this embodiment injects an out-of-frequency detection signal into the low-voltage side of the distribution transformer and obtains the out-of-frequency zero-sequence voltage vector, out-of-frequency zero-sequence current vector, and neutral-point voltage vector of the low-voltage side output by the distribution transformer. Therefore, it is only necessary to install a sensor device on the low-voltage side of the distribution transformer to acquire data, and it is not necessary to install a sensor device on the high-voltage side. The sensor device installed on the low-voltage side has a low-cost advantage over the sensor device installed on the high-voltage side, thereby reducing the cost of the monitoring system. The short-circuit complex impedance of the high-voltage side to the low-voltage side of the distribution transformer is calculated based on the out-of-frequency zero-sequence voltage vector, the out-of-frequency zero-sequence current vector, and the neutral-point voltage vector of the low-voltage side. There is no need to require that the low-voltage side voltage remains essentially unchanged or the load changes. Therefore, the fluctuation of the distribution transformer is reduced, and the influence of harmonics and three-phase imbalance on the measured electrical parameters is reduced, thereby reducing the error between the obtained electrical parameters and the actual electrical parameters. At the same time, the complex impedance parameters and rated complex impedance at different frequencies are obtained, laying the foundation for amplitude-frequency domain diagnosis of transformer winding faults.

[0051] In a specific embodiment, the first short-circuit complex impedance includes a first short-circuit resistance and a first short-circuit reactance, and the second short-circuit complex impedance includes a second short-circuit resistance and a second short-circuit reactance; then according to the first short-circuit complex impedance Z fy21 The second short-circuit complex impedance Z fg21 and the rated voltage ratio to obtain a third short-circuit complex impedance between the high-voltage side and the low-voltage side of the distribution transformer, comprising: obtaining the third short-circuit complex impedance between the high-voltage side and the low-voltage side of the distribution transformer according to the first short-circuit resistance, the second short-circuit reactance and the rated voltage ratio.

[0052] Specifically, in an industrial frequency environment, factors such as grid harmonics and electromagnetic interference from adjacent equipment will affect the measurement accuracy. The out-of-frequency test can avoid industrial frequency harmonic interference through frequency offset, thereby improving the accuracy of the first short-circuit resistance measurement. The spectrum separation of the out-of-frequency signal and the industrial frequency signal is easier to achieve, and the pure test signal can be extracted through filtering technology to reduce the impact of background noise on resistance measurement. Measuring reactance at industrial frequency is more direct, but large currents may require equipment; measuring resistance at out-of-frequency may be more accurate, but the problem of frequency conversion needs to be considered. Combining the two may complement each other. For example, using out-of-frequency resistance measurement to reduce loss errors, and industrial frequency reactance measurement is more accurate. Then, the short-circuit complex impedance of the high-voltage side to the low-voltage side is converted through the relevant formula of the rated voltage ratio. The specific formula is: Z 12 =k 2 Z fg21 , where Z 12 is the short-circuit complex impedance of the low-voltage side to the high-voltage side of the distribution transformer under power frequency, Z fg21 is the short-circuit complex impedance of the distribution transformer from the low-voltage side to the high-voltage side; k is the current transformation ratio of the distribution transformer.

[0053] In a specific embodiment, the current load loss and impedance voltage of the distribution transformer are calculated according to the following formula, including:

[0054]

[0055] Among them, P S is the current load loss of the distribution transformer, S N is the rated capacity of the distribution transformer, U N is the rated voltage of the distribution transformer at the current operating position, U X % is the impedance voltage of the distribution transformer.

[0056] In a specific embodiment, the current transformation ratio of the distribution transformer is obtained by the following method: calculating the absolute value of the difference between the power frequency impedance modulus and the modulus of the impedance composed of the short-circuit resistance and short-circuit reactance of the low-voltage side to the high-voltage side of each gear on the low-voltage side of the distribution transformer in series; determining the gear corresponding to the minimum of the above absolute values ​​as the current operating gear of the distribution transformer, and the rated voltage ratio under the current operating gear is the current transformation ratio of the distribution transformer.

[0057] In a specific embodiment, the injecting of an out-of-frequency detection signal into the low-voltage side of the distribution transformer includes: synchronously injecting the same out-of-frequency detection signal into the three phases on the low-voltage side of the distribution transformer at the neutral point zero sequence; or synchronously injecting different out-of-frequency detection signals into the three phases on the low-voltage side of the distribution transformer at the neutral point zero sequence; or synchronously injecting different out-of-frequency detection signals into the three phases on the low-voltage side of the distribution transformer at the three-phase zero sequence.

[0058] In the specific embodiment, see Figure 2a 、 Figure 2b and Figure 2c , which is a structural diagram of injecting heterofrequency detection signals into the distribution transformer at different injection points in this application. Figure 2a When the three phases are injected with current of the same frequency, the neutral point current only reflects the zero-sequence component (the total is three times the single-phase current), and the zero-sequence impedance can be directly calculated without complex phase decoupling. Only a single-frequency signal source and a neutral point access device are required. The instrument is small in size and low in cost. Figure 2b In the test, different frequency signals (such as 45Hz, 55Hz, and 65Hz) are injected into the three phases, and the impedance of each phase is measured synchronously through frequency domain separation. Multi-frequency data can be obtained in a single test, shortening the total test time. The frequency response differences of each phase can also be analyzed independently to identify defects such as single-phase winding deformation and inter-turn short circuit (for example, an abnormal decrease in the impedance of phase A may indicate a short circuit). Figure 2c In the system, different frequencies are injected into the zero-sequence points of the three phases (such as 45Hz for phase A, 55Hz for phase B, and 65Hz for phase C) to directly separate the zero-sequence impedance of each phase and avoid inter-phase coupling interference; the system supports the calculation of inter-phase mutual inductance parameters and provides data support for the optimization of three-phase unbalanced load.

[0059] In the specific embodiment, see Figure 2a , It is the power supply for frequency detection; Z a 、Z b 、Z c is the load of each phase on the low-voltage side of the distribution transformer; Z bd is the short-circuit complex impedance (including short-circuit resistance and short-circuit reactance) of the low-voltage side of each phase of the distribution transformer to the high-voltage side, which is the same for the three phases; Z OH is the single-phase coupling unit impedance; is the measured distribution transformer neutral point voltage vector; is the measured three-phase voltage vector on the low-voltage side of the distribution transformer; is the measured three-phase current vector flowing into the low-voltage side of the distribution transformer. According to the circuit principle, is the zero-sequence voltage vector of the low-voltage side of the distribution transformer obtained by calculating the three-phase differential frequency voltage; The zero-sequence current vector of the distribution transformer low-voltage side output is obtained based on the three-phase frequency-different current. When different frequency-different detection signals are injected into the three phases of the distribution transformer low-voltage side at the neutral point zero sequence, according to Figure 3 According to Kirchhoff's voltage law, the first short-circuit complex impedance Z fy21 It is obtained using the following formula:

[0060]

[0061] Among them, Z fy21 is the first short-circuit complex impedance, is the heterofrequency zero-sequence voltage vector, is the heterofrequency zero-sequence current vector, is the neutral point voltage vector.

[0062] In the specific embodiment, see Figure 2b When the same frequency-different detection signal is injected synchronously into the three phases of the low-voltage side of the distribution transformer at the neutral point zero sequence, the first short-circuit complex impedance Z of the different phases fy21 It is obtained using the following formula:

[0063]

[0064] Specifically, Figure 2b middle It is the power supply for frequency detection; Z la 、Z lb 、Z lc is the load of each phase on the low-voltage side of the distribution transformer; Z a 、Z b 、Z c is the short-circuit complex impedance (including short-circuit resistance and short-circuit reactance) of each phase of the distribution transformer from the low-voltage side to the high-voltage side, Z a 、Z b 、Z c The first short-circuit complex impedance Z fy21 ; Z OH is the single-phase coupling unit impedance; is the measured distribution transformer neutral point voltage vector; is the measured three-phase voltage vector on the low-voltage side of the distribution transformer; is the measured three-phase current vector of the heterodyne frequency flowing into the low-voltage side of the distribution transformer.

[0065] In the specific embodiment, see Figure 2c When different frequency detection signals are injected into the three phases of the low voltage side of the distribution transformer synchronously at the three phase zero sequence, the first short-circuit complex impedance Z fy21 It is obtained using the following formula:

[0066]

[0067] Among them, Z fy21 is the first short-circuit complex impedance, and are the voltage vectors of different phases in the heterofrequency zero-sequence voltage vector, and are the current vectors of different phases in the heterofrequency zero-sequence current vector, is the neutral point voltage vector.

[0068] In a specific embodiment, the second short-circuit complex impedance Z fg21 It is obtained using the following formula:

[0069]

[0070] Among them, Z fg21 is the second short-circuit complex impedance, Z fy21 is the first short-circuit complex impedance, f y is the frequency difference, f g is the industrial frequency, real() is the real part function, and imag() is the imaginary part function.

[0071] In a specific embodiment, the obtaining of the zero-sequence voltage vector of the low-voltage side output of the distribution transformer and the zero-sequence current vector The method comprises: synchronously acquiring the three-phase heterofrequency voltage vector outputted from the low-voltage side of the distribution transformer and the three-phase heterofrequency current vector outputted from the low-voltage side of the distribution transformer; converting the three-phase heterofrequency voltage vector into the heterofrequency zero-sequence voltage vector. and converting the three-phase heterodyne current vector into the heterodyne zero-sequence current vector Specifically, according to the symmetrical component method, the heterogeneous zero-sequence voltage vector is the average value of the three-phase heterogeneous voltage vectors, and the heterogeneous zero-sequence current vector is the average value of the three-phase heterogeneous current vectors.

[0072] In this embodiment, the transformer simulation model is parameterized based on the S11-M-200 / 10 transformer. The capacity is set to 200 kVA, and the connection group is Dyn11. The rated voltages of the high-voltage side 1st to 5th gears are 9.5 kV, 9.75 kV, 10 kV, 10.25 kV, and 10.5 kV, respectively, and the rated voltage of the low-voltage side is 0.4 kV. The transformer short-circuit complex impedance is 4%, and the transformer is set to operate in gear 3. Based on this, the winding reactance on the delta-connected side of the transformer is calculated to be 20 Ω, and the leakage reactance of the transformer model in the simulation model is accordingly set to 0.04 pu. The transformer load loss is 2.6 kW, and based on this, the winding resistance on the delta-connected side of the transformer is calculated to be 6.5 Ω.

[0073] In a specific embodiment, the first embodiment of the online monitoring method for electrical parameters of a distribution transformer in this application is as follows: disconnect the detection bypass switch and close the detection output switch. Apply a frequency detection power supply to the neutral point on the low-voltage side of the distribution transformer, and inject a frequency detection voltage (current) into the low-voltage side of the distribution transformer. Apply a frequency detection power supply with a frequency of 100 Hz and an amplitude of 10V to the three phases on the low-voltage side of the distribution transformer. The detection power supply is a voltage source. The three-phase heterodyne voltage vector on the low-voltage side of the distribution transformer, the three-phase heterodyne current vector flowing into the low-voltage side of the distribution transformer, and the neutral point voltage on the low-voltage side of the distribution transformer are synchronously measured, which are: Phase A voltage is 3.53-7.94i; Phase B voltage is 3.53-7.94i; Phase C voltage is 3.53-7.94i; Phase A current is -0.18+0.4i; Phase B current is -0.18+0.4i; Phase C current is -0.18+0.4i; and the neutral point voltage is 3.55-7.94i. The heterodyne zero-sequence voltage vector on the low-voltage side of the distribution transformer is calculated to be 3.53-i7.94V, and the heterodyne zero-sequence current vector outputted from the low-voltage side of the distribution transformer is 0.18-i0.4A. The electrical parameter detection circuit of the distribution transformer after applying the heterodyne detection power supply is obtained, such as Figure 2a As shown. Based on the electrical parameter detection circuit, a monitoring equation is written to obtain the short-circuit complex impedance of the distribution transformer's low-voltage side to its high-voltage side under heterodyne conditions: 0.0104+i0.064Ω, its short-circuit resistance: 0.0104Ω, and its short-circuit reactance: 0.064Ω. Using the low-voltage side power frequency impedance calculation formula, the short-circuit reactance of the distribution transformer's low-voltage side to its high-voltage side under power frequency conditions is calculated to be 0.032Ω. The distribution transformer's current operating gear is gear 3, and its rated voltage ratio at this gear is 25. Using the formula, the short-circuit complex impedance of the distribution transformer's high-voltage side to its low-voltage side is calculated to be: 6.5+i20Ω, resulting in a short-circuit resistance of 6.5Ω and a short-circuit reactance of 20Ω. The detection output switch is disconnected, and the detection bypass switch is closed simultaneously.

[0074] In a specific embodiment, the second embodiment of the method for online monitoring of electrical parameters of a distribution transformer in this application is as follows: applying a three-phase frequency detection power supply to the low-voltage side of the distribution transformer, and injecting a frequency detection voltage (current) into the low-voltage side of the distribution transformer. A frequency detection power supply with a frequency of 100 Hz and an amplitude of 10 V is applied to the three-phase frequency detection power supply on the low-voltage side of the distribution transformer, and the detection power supply is a voltage source. The three-phase heterodyne voltage vectors on the low-voltage side of the distribution transformer, the three-phase heterodyne current vectors flowing into the low-voltage side of the distribution transformer, and the neutral point voltage on the low-voltage side of the distribution transformer are synchronously measured, which are: Phase A voltage is 4.08-9.13i(V); Phase B voltage is 4.08-9.13i(V); Phase C voltage is 4.08-9.13i(V); Phase A current is 1.29-3.06i(A); Phase B current is 1.29-3.06i(A); Phase C current is 1.29-3.06i(A); Neutral point voltage is 3.87-9.18i(V); The electrical parameter detection circuit of the distribution transformer after applying the heterodyne detection power supply is obtained, such as Figure 2c As shown. According to the electrical parameter detection circuit, the monitoring equation is written as:

[0075] The short-circuit resistance and short-circuit reactance of the low-voltage side to the high-voltage side of the distribution transformer under different frequencies are 0.0104Ω and 0.0634Ω respectively. The current transformation ratio of the distribution transformer, the short-circuit resistance of the high-voltage side to the low-voltage side, the short-circuit reactance, the load loss, and the impedance voltage parameters are further obtained, including: obtaining the rated capacity of the distribution transformer when it leaves the factory, the rated voltage ratio of each gear, the load loss, and the impedance voltage parameters, and calculating the module value of the impedance composed of the short-circuit resistance and short-circuit reactance of the low-voltage side to the high-voltage side of each gear on the low-voltage side of the distribution transformer in series; the simulation model sets the rated capacity of the transformer to 200kVA, and the transformer is There are five gears, with rated voltage ratios of 1st to 5th gear being 23.75, 24.375, 25, 25.625, and 26.25, respectively. The load loss is 2.6kW, and the impedance voltage is 4%. The moduli of the impedance formed by the series short-circuit resistance and short-circuit reactance of the low-voltage side to the high-voltage side of the distribution transformer for gears 1 to 5 are calculated to be 0.03037Ω, 0.03199Ω, 0.03365Ω, 0.03535Ω, and 0.0371Ω, respectively. According to the formula, the short-circuit complex impedance (including the short-circuit resistance and short-circuit reactance) of the distribution transformer low-voltage side to the high-voltage side at different frequencies is converted to the short-circuit complex impedance of the distribution transformer low-voltage side to the high-voltage side at the power frequency, and the modulus of the short-circuit complex impedance of the low-voltage side to the high-voltage side at the power frequency is further calculated. The short-circuit complex impedance (including short-circuit resistance and short-circuit reactance) of the distribution transformer's low-voltage side to high-voltage side at different frequencies is converted to the short-circuit complex impedance of the distribution transformer's low-voltage side to high-voltage side at power frequency, which is 0.0104 + 0.032 Ω. The modulus of the short-circuit complex impedance of the low-voltage side to high-voltage side at power frequency is calculated to be 0.03365 Ω. Calculate the absolute value of the difference between the power frequency impedance modulus and the modulus of the impedance formed by the series connection of the short-circuit resistance and short-circuit reactance of the low-voltage side to the high-voltage side for each gear on the low-voltage side of the distribution transformer. The values ​​for gears 1 to 5 are 0.003 Ω, 0.002 Ω, 0.000 Ω, 0.002 Ω, and 0.003 Ω, respectively. The gear corresponding to the minimum absolute value is determined as the current operating gear of the distribution transformer, and the rated voltage ratio for the current operating gear is determined as the current transformation ratio of the distribution transformer. The gear corresponding to the minimum absolute value is gear 3, with a rated voltage ratio of 25. The short-circuit resistance and reactance of the distribution transformer's low-voltage side to high-voltage side at power frequency are converted to 6.5Ω and 20Ω, respectively, based on the formula. The current load loss and impedance voltage of the distribution transformer are calculated to be 2.6kW and 4%, respectively.

[0076] Specifically, Figure 2c In the case of a power distribution transformer, the three-phase impedance is the same. According to the circuit principle,

[0077]

[0078] The three equations can be added together to form the following equation:

[0079]

[0080] Further:

[0081]

[0082] So we can further list:

[0083]

[0084] In the specific embodiment, see Figure 4a, is a structural diagram of an amplitude-frequency domain online monitoring system for electrical parameters of a distribution transformer in this application. The online monitoring system includes: an heterodyne detection power supply 201, a single-phase coupling unit 202, a detection output switch 203, a detection bypass switch 204, a neutral point voltage sensing unit 205, a three-phase voltage sensing unit 206, a three-phase current sensing unit 207 and a control and calculation unit 208; one end of the heterodyne detection power supply 201 is respectively connected to one end of the detection bypass switch 204 and grounded, the other end of the heterodyne detection power supply 201 is connected to one end of the single-phase coupling unit 202, and the single-phase coupling unit The other end of 202 is connected to one end of the detection output switch 203, the other end of the detection output switch 203, the other end of the detection bypass switch 204 and one end of the neutral point voltage sensing unit 205 are respectively connected to the neutral point of the distribution transformer, the other end of the neutral point voltage sensing unit 205 is grounded, one end of the three-phase voltage sensing unit 206 and one end of the three-phase current sensing unit 207 are connected to the three-phase output line of the distribution transformer, the other end of the three-phase voltage sensing unit 206 and the other end of the three-phase current sensing unit 207 are connected to the control and calculation unit 208; the frequency detection power supply 201 is used The single-phase coupling unit 202 and the detection output switch 203 are used to inject an out-of-frequency detection signal into the low-voltage side of the distribution transformer; the detection bypass switch 204, the out-of-frequency detection power supply 201, the single-phase coupling unit 202 and the detection output switch 203 are connected in parallel to form a series branch for grounding the neutral point of the distribution transformer when no electrical parameter monitoring is performed; the neutral point voltage sensing unit 205 is used to obtain the neutral point voltage vector of the low-voltage side of the distribution transformer; the three-phase voltage sensing unit 206 is used to obtain the out-of-frequency zero-sequence voltage vector outputted by the low-voltage side of the distribution transformer; the three-phase current sensing unit 207 is used to Obtain an out-of-frequency zero-sequence current vector outputted from the low-voltage side of the distribution transformer; the control and calculation unit 208 is configured to perform the following steps: obtain a first short-circuit complex impedance from the low-voltage side to the high-voltage side of the distribution transformer under out-of-frequency conditions based on the out-of-frequency zero-sequence voltage vector, the out-of-frequency zero-sequence current vector, and the neutral point voltage vector; convert the first short-circuit complex impedance to a second short-circuit complex impedance from the low-voltage side to the high-voltage side of the distribution transformer under the power frequency; obtain a rated voltage ratio of the distribution transformer under the current operating position; and obtain a third short-circuit complex impedance from the high-voltage side to the low-voltage side of the distribution transformer based on the first short-circuit complex impedance, the second short-circuit complex impedance, and the rated voltage ratio.

[0085] Specifically, one side of the heterofrequency detection power supply is connected to the neutral point of the low-voltage side of the distribution transformer through a single-phase coupling unit and a detection output switch, and the other side is grounded; the single-phase coupling unit is used to couple the detection signal of the heterofrequency detection power supply to the system; any type or combination of resistors, capacitors, inductors, transformers, voltage transformers, etc. can be used. The detection output switch is used to connect the heterofrequency detection power supply and the single-phase coupling unit to the neutral point of the distribution transformer; any AC switch such as a contactor or circuit breaker can be used. The detection bypass switch is connected in parallel with the series branch formed by the heterofrequency detection power supply, the single-phase coupling unit, and the detection output switch, and is used to ground the neutral point of the distribution transformer when no detection is performed. Any AC switch such as a contactor or circuit breaker can be used. The neutral point voltage sensing unit is connected to the neutral point of the distribution transformer and is used to measure the neutral point frequency-differential voltage on the low-voltage side of the distribution transformer. It can adopt any form such as voltage transformer, voltage divider, Hall sensor, etc. The three-phase voltage sensing unit is connected to the three-phase outgoing line on the low-voltage side of the distribution transformer and is used to measure the three-phase frequency-differential voltage on the low-voltage side of the distribution transformer. It can adopt any form such as voltage transformer, voltage divider, Hall sensor, etc. The three-phase current sensing unit is used to measure the frequency-differential current output from the low-voltage side of the distribution transformer and is connected to the three-phase outgoing line on the low-voltage side of the distribution transformer. It can adopt any form such as current transformer, Rogowski coil, etc. The control and calculation unit controls the output voltage or output current signal amplitude of the frequency-differential detection power supply. When the frequency of the frequency-differential detection power supply is When the frequency is variable, it is also used to control the output frequency of the different-frequency detection power supply; control the opening and closing of the detection bypass switch and the detection output switch; receive current and voltage signals from the three-phase voltage sensing unit, the three-phase current sensing unit, and the neutral point voltage sensing unit; calculate the different-frequency zero-sequence voltage vector on the low-voltage side of the distribution transformer; calculate the different-frequency zero-sequence current vector output from the low-voltage side of the distribution transformer; calculate the short-circuit resistance and short-circuit reactance of the low-voltage side to the high-voltage side of the distribution transformer under different frequencies according to the formula; calculate the short-circuit reactance of the low-voltage side to the high-voltage side of the distribution transformer under the power frequency; obtain the current operating gear of the distribution transformer and the rated voltage ratio under the gear; calculate the short-circuit resistance and short-circuit reactance of the high-voltage side to the low-voltage side of the distribution transformer.

[0086] In the specific embodiment, see Figure 4bThe online monitoring system includes an inter-frequency detection power supply, a single-phase coupling unit, a neutral point voltage sensing unit, a three-phase voltage sensing unit, a three-phase current sensing unit, and a control and calculation unit. One side of the inter-frequency detection power supply is connected to the neutral point on the low-voltage side of the distribution transformer via the single-phase coupling unit and a detection output switch, and the other side is grounded. The single-phase coupling unit is used to couple the detection signal from the inter-frequency detection power supply to the system. Any type of device, including resistors, capacitors, inductors, transformers, and voltage transformers, or any combination thereof, can be used. The neutral point voltage sensing unit is connected to the neutral point of the distribution transformer and is used to measure the neutral point heterodyne voltage on the low-voltage side of the distribution transformer. It can adopt any form such as voltage transformer, voltage divider, Hall sensor, etc. The three-phase voltage sensing unit is connected to the three-phase outgoing line on the low-voltage side of the distribution transformer and is used to measure the three-phase heterodyne voltage on the low-voltage side of the distribution transformer. It can adopt any form such as voltage transformer, voltage divider, Hall sensor, etc. The three-phase current sensing unit is used to measure the heterodyne current outputted from the low-voltage side of the distribution transformer and is connected to the three-phase outgoing line on the low-voltage side of the distribution transformer. It can adopt any form such as current transformer, Rogowski coil, etc. The control and calculation unit controls the output voltage or output current signal amplitude of the heterodyne detection power supply. value; when the frequency of the different-frequency detection power supply is variable, it is also used to control the output frequency of the different-frequency detection power supply; receive the voltage and current signals of the neutral point voltage sensing unit, the three-phase voltage sensing unit, and the three-phase current sensing unit; calculate the different-frequency zero-sequence voltage vector on the low-voltage side of the distribution transformer; calculate the different-frequency zero-sequence current vector outputted by the low-voltage side of the distribution transformer; obtain the short-circuit resistance and short-circuit reactance of the low-voltage side to the high-voltage side of the distribution transformer under different frequencies according to the formula; calculate the short-circuit reactance of the low-voltage side to the high-voltage side of the distribution transformer under the working frequency; obtain the current operating gear of the distribution transformer and the rated voltage ratio under the gear; calculate the short-circuit resistance and short-circuit reactance of the high-voltage side to the low-voltage side of the distribution transformer.

[0087] In the specific embodiment, see Figure 4cThe online monitoring system includes: an heterofrequency detection power supply, a three-phase coupling unit; a three-phase voltage sensing unit; a three-phase current sensing unit; a neutral point voltage sensing unit; a control and calculation unit; the heterofrequency detection power supply is connected to the low-voltage side outlet of the distribution transformer through the three-phase coupling unit, and the heterofrequency detection voltage and current injected into the transformer by the heterofrequency detection power supply are sinusoidal signals, and the three-phase power supply contains a zero-sequence component; the three-phase coupling unit is used to connect the heterofrequency detection power supply and the low-voltage side outlet of the distribution transformer, and can adopt any type or combination of resistors, capacitors, inductors, transformers, voltage transformers, etc. The three-phase voltage sensing unit is connected to the three-phase outgoing line on the low-voltage side of the distribution transformer and is used to measure the three-phase heterodyne voltage on the low-voltage side of the distribution transformer; it can adopt any form such as voltage transformer, voltage divider, Hall sensor, etc.; the three-phase current sensing unit is used to measure the heterodyne current injected by the heterodyne detection power supply into the low-voltage side of the distribution transformer, and is connected between the three-phase outgoing line on the low-voltage side of the distribution transformer and the three-phase coupling unit, and can adopt any form such as current transformer, Rogowski coil, etc.; the neutral point voltage sensing unit is connected to the neutral point of the distribution transformer and is used to measure the heterodyne voltage on the neutral point of the low-voltage side of the distribution transformer. Any form such as a voltage transformer, a voltage divider, a Hall sensor, etc. can be used; the control and calculation unit is used to control the output voltage or output current signal amplitude of the different-frequency detection power supply; when the frequency of the different-frequency detection power supply 1 is variable, it is also used to control the output frequency of the different-frequency detection power supply; receive the current and voltage signals of the three-phase voltage sensing unit, the three-phase current sensing unit, and the neutral point voltage sensing unit, and calculate the current transformation ratio of the distribution transformer, the short-circuit resistance of the high-voltage side to the low-voltage side, the short-circuit reactance, the load loss, and the impedance voltage parameters based on the above voltage and current signals and the calculation formula.

[0088] In a specific embodiment, the third embodiment of the present application provides an online monitoring device for electrical parameters of a distribution transformer, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of the method described in any one of the first embodiments of the present application.

[0089] In a specific embodiment, the fourth embodiment of the present application provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor performs the steps of the method described in any one of the first embodiments of the present application.

[0090] Figure 5 The internal structure of a computer device in one embodiment is shown. The computer device can be a terminal or a server. Figure 5The computer device includes a processor, a memory, etc. connected via a system bus. 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 processor, the processor can implement the method of this embodiment. The internal memory may also store a computer program. When the computer program is executed by the processor, the processor can implement the method of this embodiment. It will be understood by those skilled in the art that Figure 5 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.

[0091] The above embodiments merely represent 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.

[0092] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any person skilled in the art may utilize the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes for application in other fields. However, any simple modification, equivalent change, and modification of the above embodiments made in accordance with the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for online monitoring of electrical parameters of distribution transformers in complex frequency domain, characterized in that: The method comprises: Injecting an out-of-frequency detection signal into the low-voltage side of the distribution transformer; the out-of-frequency detection signal is an out-of-frequency detection voltage or an out-of-frequency detection current; Synchronously acquiring the heterogeneous frequency zero-sequence voltage vector and the heterogeneous frequency zero-sequence current vector outputted by the low-voltage side of the distribution transformer, and synchronously acquiring the neutral point voltage vector on the low-voltage side of the distribution transformer; Obtaining a first short-circuit complex impedance from the low-voltage side to the high-voltage side of the distribution transformer under heterogeneous frequencies according to the heterogeneous zero-sequence voltage vector, the heterogeneous zero-sequence current vector, and the neutral point voltage vector; Converting the first short-circuit complex impedance to a second short-circuit complex impedance between the low-voltage side and the high-voltage side of the distribution transformer at the power frequency; Obtaining the rated voltage ratio of the distribution transformer at the current operating gear; A third short-circuit complex impedance between the high-voltage side and the low-voltage side of the distribution transformer is obtained according to the first short-circuit complex impedance, the second short-circuit complex impedance, and the rated voltage ratio.

2. The method for online monitoring of electrical parameters of a distribution transformer in complex frequency domain according to claim 1, characterized in that: The first short-circuit complex impedance includes a first short-circuit resistance and a first short-circuit reactance, and the second short-circuit complex impedance includes a second short-circuit resistance and a second short-circuit reactance; Then, obtaining a third short-circuit complex impedance between the high-voltage side and the low-voltage side of the distribution transformer according to the first short-circuit complex impedance, the second short-circuit complex impedance, and the rated voltage ratio includes: A third short-circuit complex impedance between the high-voltage side and the low-voltage side of the distribution transformer is obtained according to the first short-circuit resistance, the second short-circuit reactance, and the rated voltage ratio.

3. The method for online monitoring of electrical parameters of distribution transformers in complex frequency domain according to claim 1, characterized in that: The injecting of an out-of-frequency detection signal into the low-voltage side of the distribution transformer comprises: The same frequency-different detection signal is injected synchronously into the three phases on the low-voltage side of the distribution transformer at the neutral point zero sequence; or injecting different frequency detection signals synchronously into the three phases on the low voltage side of the distribution transformer at the neutral point zero sequence; Or different out-of-frequency detection signals are synchronously injected into the three phases on the low-voltage side of the distribution transformer at the three-phase zero sequence.

4. The method for online monitoring of electrical parameters of a distribution transformer in complex frequency domain according to claim 3, characterized in that: When the same out-of-frequency detection signal is synchronously injected into the three phases on the low-voltage side of the distribution transformer at the neutral point zero sequence, the first short-circuit complex impedance is obtained using the following formula: Among them, Z fy21 is the first short-circuit complex impedance, is the heterofrequency zero-sequence voltage vector, is the heterofrequency zero-sequence current vector, is the neutral point voltage vector.

5. The method for online monitoring of electrical parameters of distribution transformers in complex frequency domain according to claim 3, characterized in that: When different out-of-frequency detection signals are synchronously injected into the three phases on the low-voltage side of the distribution transformer at the three-phase zero sequence, the first short-circuit complex impedance is obtained using the following formula: Among them, Z fy21 is the first short-circuit complex impedance, and are the voltage vectors of different phases in the heterofrequency zero-sequence voltage vector, and are the current vectors of different phases in the heterofrequency zero-sequence current vector, is the neutral point voltage vector.

6. The method for online monitoring of distribution transformer electrical parameters in complex frequency domain according to claim 1, characterized in that: The second short-circuit complex impedance is obtained using the following formula: Among them, Z fg21 is the second short-circuit complex impedance, Z fy21 is the first short-circuit complex impedance, f y is the frequency difference, f g is the industrial frequency, real() is the real part function, and imag() is the imaginary part function.

7. The method for online monitoring of distribution transformer electrical parameters in complex frequency domain according to claim 1, characterized in that: The obtaining of the different-frequency zero-sequence voltage vector and the different-frequency zero-sequence current vector outputted by the low-voltage side of the distribution transformer includes: Synchronously acquiring a three-phase, different-frequency voltage vector outputted by the low-voltage side of the distribution transformer and a three-phase, different-frequency current vector outputted by the low-voltage side of the distribution transformer; The three-phase heterogeneous voltage vector is converted into the heterogeneous zero-sequence voltage vector, and the three-phase heterogeneous current vector is converted into the heterogeneous zero-sequence current vector.

8. A complex frequency domain online monitoring system for electrical parameters of distribution transformers, characterized in that: The system includes: a different frequency detection power supply, a single-phase coupling unit, a detection output switch, a detection bypass switch, a neutral point voltage sensing unit, a three-phase voltage sensing unit, a three-phase current sensing unit and a control and calculation unit; One end of the different-frequency detection power supply is respectively connected to one end of the detection bypass switch and grounded, the other end of the different-frequency detection power supply is connected to one end of the single-phase coupling unit, the other end of the single-phase coupling unit is connected to one end of the detection output switch, the other end of the detection output switch, the other end of the detection bypass switch and one end of the neutral point voltage sensing unit are respectively connected to the neutral point of the distribution transformer, the other end of the neutral point voltage sensing unit is grounded, one end of the three-phase voltage sensing unit and one end of the three-phase current sensing unit are both connected to the three-phase outgoing lines of the distribution transformer, and the other end of the three-phase voltage sensing unit and the other end of the three-phase current sensing unit are both connected to the control and calculation unit; The different-frequency detection power supply is used to inject different-frequency detection signals into the low-voltage side of the distribution transformer through the single-phase coupling unit and the detection output switch; The series branch composed of the detection bypass switch, the different-frequency detection power supply, the single-phase coupling unit and the detection output switch is connected in parallel, and is used to ground the neutral point of the distribution transformer when no electrical parameter monitoring is performed; The neutral point voltage sensing unit is used to obtain the neutral point voltage vector of the low voltage side of the distribution transformer; The three-phase voltage sensing unit is used to obtain the different-frequency zero-sequence voltage vector outputted by the low-voltage side of the distribution transformer; The three-phase current sensing unit is used to obtain the different-frequency zero-sequence current vector output by the low-voltage side of the distribution transformer; The control and calculation unit is used to perform the following steps: Obtaining a first short-circuit complex impedance from the low-voltage side to the high-voltage side of the distribution transformer under heterogeneous frequencies according to the heterogeneous zero-sequence voltage vector, the heterogeneous zero-sequence current vector, and the neutral point voltage vector; Converting the first short-circuit complex impedance to a second short-circuit complex impedance between the low-voltage side and the high-voltage side of the distribution transformer at the power frequency; Obtaining the rated voltage ratio of the distribution transformer at the current operating gear; A third short-circuit complex impedance between the high-voltage side and the low-voltage side of the distribution transformer is obtained according to the first short-circuit complex impedance, the second short-circuit complex impedance, and the rated voltage ratio.

9. An online monitoring device for electrical parameters of a distribution transformer, comprising a memory and a processor, characterized in that: The memory stores a computer program, and when the computer program is executed by the processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

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