CN112595941B - Method and system for monitoring interlayer insulation of converter transformer winding - Google Patents
Method and system for monitoring interlayer insulation of converter transformer winding Download PDFInfo
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Abstract
The invention relates to a method and a system for monitoring insulation between converter transformer winding layers, which are used for acquiring a broadband common-mode impedance response curve of a transformer to be tested under the insulation health condition as a reference; dividing the frequency bands into 3 frequency bands in sequence according to the positions of the resonance points; measuring an online broadband common-mode impedance response curve under the working state of the transformer to be measured; and obtaining a ratio curve of the on-line broadband common-mode impedance and the broadband common-mode impedance under the insulation health condition as a judgment index, and evaluating the insulation state between the winding layers of the transformer to be tested. The invention utilizes the broadband common-mode impedance response curve to evaluate the insulation state of the power transformer, and utilizes different frequency bands of the broadband common-mode impedance response curve to realize different types of interlayer insulation monitoring; by utilizing the judgment indexes, the quantitative evaluation of the aging degree of the interlayer insulation of different types is realized, the interlayer insulation between the valve and the grid side winding and the interlayer insulation state in each side winding can be accurately evaluated, the sensor installation mode is not required to be invaded, and the reliability is high.
Description
Technical Field
The invention relates to the technical field of transformer modeling, in particular to a method and a system for monitoring insulation between converter transformer winding layers.
Background
Power system capacity and scale are expanding year by year. The capacity of new energy grid connection is continuously improved, and the types of load absorption tend to be diversified. Distributed new energy grid connection, electric vehicle charging pile access and energy storage technology are rapidly developed, so that the connection compactness and complexity of each unit of power generation, transmission, distribution and utilization in the grid are increased.
Power electronic converters play a crucial role in such complex grid systems. The power electronic converter is connected with an alternating current power grid and a direct current power grid, and high-efficiency conversion and flexible control among different energy types are guaranteed. The power electronic converter and the load are generally connected with a converter transformer to realize electric energy conversion and power transmission. Therefore, the converter transformer is widely applied to application scenes of ultra/extra-high voltage alternating current and direct current systems, rail transit systems, industrial variable frequency loads and the like.
In order to improve the power density of the converter transformer, the volume of the converter transformer can be reduced under a certain capacity, and the winding of the converter transformer is required to have a multilayer structure under partial application scenes. Thus, the type of interlayer insulation includes interlayer insulation between windings on the same side in addition to conventional interlayer insulation between windings on the valve side and the mesh side. However, monitoring of the inter-layer insulation in the same side winding is seldom mentioned. At present, no effective monitoring method aiming at insulation between different types of winding layers of the power transformer exists.
Compared with the conventional line-frequency power transformer, the power transformer (i.e., the converter transformer) of the power electronic converter system is more expensive to manufacture and has more serious challenges in terms of operational reliability. The price of each converter transformer of 800kV of Siemens company is up to 1 hundred million yuan. In recent years, several ac/converter substation major accidents have occurred by national grid companies. 4, 4 months in 2018, wherein the +/-800 kV Tianshan converter station pole I high-end Y/D-B phase converter transformer suddenly fails and catches fire; in 2019, 3 months +/-800 kV Zhaowei direct-current transmission engineering Yinan convertor station pole II low-end Y/Y-C phase convertor transformer suddenly fails and catches fire; in 11 months in 2019, the No. 3 main transformer of the Sn Union-Shandong 1000kV extra-high voltage Jinnanquan city substation detonates to cause 1 death and 2 injuries.
Therefore, the multiple and serious faults of the converter transformer can be seen, and huge economic loss and personal safety hazards are brought. The converter transformer has complex working conditions and a plurality of insulation fault inducers, and the field accident is developed by the aging of the insulation parts to a great extent. Therefore, compared with the traditional power transformer, the online monitoring method for the insulation aging of the converter transformer has higher requirements. Particularly, for the current insulation monitoring between converter transformer winding layers which is not deeply developed, an effective monitoring technology needs to be provided urgently.
At present, the power industry widely adopts a class of application technologies based on physical and chemical state parameters (temperature, vibration, gas in oil, and the like) and a class of application technologies based on high-frequency electromagnetic state signals (partial discharge) to realize online insulation state monitoring of all power transformers. According to the test requirements and regulations of GB 50776-.
(1) A series of off-line detection such as a lightning impulse test, an oil chromatographic analysis, a low-voltage partial discharge test, an insulation resistance test and the like is carried out in the factory test process of one converter transformer of a Tizhou extra-high voltage direct-current transmission project of the tin union, and the fault reason is not found, so that the product can only be returned to a workshop to drop a hanging cover and be disassembled for inspection, and the turn-to-turn short circuit caused by the insulation damage of a winding is determined. (2) Local overheating is caused by manufacturing process defects of the Tianshan converter transformer winding, and due to the lack of a reliable online insulation aging monitoring means, the development condition of internal insulation defects cannot be known in time in the running process. (3) The accident report of the spring city substation indicates that the abnormal data of several electrified detection results before the accident occurs are not found, the acetylene detection results comprising 3 times of oil chromatographic analysis are all in the range of 0.29-0.32 uL/L and are less than 1uL/L specified by the GB 24846 plus 2018 regulations, and the results are displayed to be normal by ultrasonic wave, high-frequency partial discharge detection and infrared temperature measurement.
The on-line insulation state monitoring method of the power transformer based on the physical and chemical state parameters has the following defects: (1) the change rule of the physicochemical state quantity caused by insulation aging is complex, the monitoring result is often not visual, the influence of environmental conditions and sensor installation is complex, the method basically depends on experience and mathematical methods for processing, the explanation mechanism is obscure, and the standard is difficult to unify. (2) The change of the physical and chemical state parameters is weak usually, and in order to ensure the precision and the signal to noise ratio, a sensor is usually required to be arranged in a box body of a power transformer, so that the method has the characteristic of invasiveness of sensing equipment, and the complexity of operation, maintenance and repair of an equipment body and a sensing device is increased. (3) The method generally monitors and evaluates the whole insulation system of the monitoring transformer, and the quantitative evaluation of the aging degree of the specified insulation type cannot be definitely performed on the insulation between winding layers of the monitoring transformer.
A monitoring method based on ultra/ultrahigh frequency partial discharge signals generally needs a specially-assigned sensor, the sensitivity of a monitoring result is affected by the installation position of the sensor, the economy is low, a mechanism is not completely clear, and an evaluation method is too complex and has no generality. This type of method also generally does not allow a quantitative assessment of the degree of ageing of a given insulation type with explicit reference to monitoring the insulation between winding layers of a transformer.
Another insulation monitoring method for power transformers based on simple electrical state parameters (voltage and current) still cannot be applied on line in a large range. On one hand, reliable and sensitive insulation aging monitoring cannot be realized only by depending on power frequency components of voltage and current. When the power transmission at the source side and the power receiving at the network side are adjusted and fluctuated in real time, the operating voltage and the operating current of the power transformer also change dynamically, and the influence of the dynamic operating condition of the system on the measurement precision of the electric quantity signal is inevitably introduced. From an evaluation method perspective, identifying voltage and current magnitude variations caused by insulation aging and operating conditions, respectively, also presents challenges. On the other hand, more insulation state information can be obtained by utilizing the wide-frequency band components of the voltage and the current, and how to effectively utilize the inherent harmonic component of the converter system to realize the monitoring of the insulation between the winding layers of the converter transformer is one of the technical problems to be solved by the invention.
Therefore, the existing online insulation state monitoring method for the power transformer has the problems of insufficient sensitivity, insufficient accuracy and the like, is applied to insulation monitoring of the converter transformer, and also has the problem that the targeted quantitative evaluation of the insulation aging degree between winding layers is difficult to realize. At present, the power industry and academic research work have few non-invasive online insulation state monitoring technologies specially designed for power transformers of power electronic converter systems.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method and a system for monitoring the interlayer insulation of a converter transformer winding, which can realize quantitative evaluation of the interlayer insulation of the converter transformer winding, avoid invasion of a sensor installation mode and reduce the problem of low reliability caused by a sensing device; in an operating environment with strong electromagnetic interference, high-precision and high signal-to-noise ratio measurement results of monitoring state parameters are ensured; the state monitoring parameters are not influenced by the dynamic operation condition of the system, and the insulation evaluation method is simple and visual; including the inter-layer insulation between the valves, the mesh side windings and the inter-layer insulation inside each side (valve side/mesh side) winding.
In order to achieve the above object, the present invention provides a method for monitoring insulation between layers of a converter transformer winding,
acquiring a broadband common-mode impedance response curve of a transformer to be tested under an insulation health condition as a reference; dividing the frequency bands into 3 frequency bands in sequence according to the positions of the resonance points, wherein the first frequency band is a linear band, the second frequency band is a resonance band, and the third frequency band is a linear band;
measuring an online broadband common-mode impedance response curve under the working state of the transformer to be measured;
and obtaining a ratio curve of the on-line broadband common-mode impedance and the broadband common-mode impedance under the insulation health condition as a judgment index, and evaluating the insulation state between winding layers of the transformer to be tested based on the judgment index.
Further, the evaluating the insulation state between the winding layers of the transformer to be tested based on the judgment index comprises: when the first frequency band judgment index and the third frequency band judgment index are reduced, judging that the interlayer insulation between the transformer valve side winding and the network side winding is aged; when the first frequency band judgment index is unchanged and the third frequency band judgment index is reduced, the aging of the interlayer insulation inside the transformer valve side or network side winding is judged; and when the first frequency band index and the third frequency band index are not changed, judging that the interior is not aged.
Further, obtaining a broadband common-mode impedance response curve of the transformer to be tested under the insulation health condition comprises:
after the valve side is connected with the neutral point of the grid side winding, an impedance analyzer is used for directly measuring to obtain an offline broadband common-mode impedance response curve;
further, obtaining a broadband common-mode impedance response curve of the transformer to be tested under the insulation health condition comprises: and calculating by using the equivalent transformer model to obtain an offline broadband common-mode impedance response curve.
Further, obtaining a broadband common-mode impedance response curve of the transformer to be tested under the insulation health condition comprises: and when the transformer to be tested initially runs, measuring an online broadband common-mode impedance response curve in a working state.
Further, measuring the online broadband common-mode impedance response curve comprises: measuring phase voltage u of any phase valve side windingpAnd net side neutral point current i0(ii) a Calculating upAnd i0Has a common mode component of amplitude UpAnd I0Calculating the common-mode impedance response:
the invention provides a system for monitoring the interlayer insulation of a converter transformer winding, which comprises a detection module, a storage module and a calculation module;
the detection module is used for detecting a measured online broadband common-mode impedance response curve of the transformer to be detected in a working state;
the storage module stores a broadband common-mode impedance response curve of the transformer to be tested under the insulation health condition, and the broadband common-mode impedance response curve is sequentially divided into 3 frequency bands according to the positions of resonance points, wherein the first frequency band is a linear band, the second frequency band is a resonance band, and the third frequency band is a linear band;
the calculation module calculates a ratio curve of the on-line broadband common-mode impedance to the broadband common-mode impedance under the insulation health condition as a judgment index, and evaluates the insulation state between winding layers of the transformer to be tested based on the judgment index.
Further, the estimating, by the calculation module, the insulation state between winding layers of the transformer to be tested based on the judgment index includes: when the first frequency band judgment index and the third frequency band judgment index are reduced, judging that the interlayer insulation between the transformer valve side winding and the network side winding is aged; when the first frequency band judgment index is unchanged and the third frequency band judgment index is reduced, the aging of the interlayer insulation inside the transformer valve side or network side winding is judged; and when the first frequency band index and the third frequency band index are not changed, judging that the interior is not aged.
Further, the detecting module detecting an online broadband common-mode impedance response curve measured in the working state of the transformer to be measured includes: measuring phase voltage u of any phase valve side windingpAnd net side neutral point current i0(ii) a Calculating upAnd i0Has a common mode component of amplitude UpAnd I0Calculating the common-mode impedance response:
further, before the transformer to be detected initially runs, the detection module measures an online broadband common-mode impedance response curve in a working state and sends the online broadband common-mode impedance response curve to the storage module to be stored as the broadband common-mode impedance response curve in the insulation health condition.
The technical scheme of the invention has the following beneficial technical effects:
(1) the invention utilizes the broadband common-mode impedance response curve to evaluate the insulation state of the power transformer, and utilizes different frequency bands of the broadband common-mode impedance response curve to realize different types of interlayer insulation monitoring; by utilizing the judgment indexes, the quantitative evaluation of the aging degrees of the different types of interlayer insulation is realized, and the interlayer insulation between the valve and the grid side winding and the interlayer insulation state in the winding at each side (valve side/grid side) can be accurately evaluated.
(2) According to the invention, an additional sensor is not required to be installed, so that the sensor installation mode is avoided, and the problem of low reliability brought by the sensing device is reduced.
(3) The state monitoring parameters are not influenced by the dynamic operation condition of the system, and the insulation evaluation method is simple and visual; and in an operating environment with strong electromagnetic interference, the high-precision and high signal-to-noise ratio measurement result of the monitoring state parameter is ensured.
Drawings
FIG. 1 is a reference curve of an offline broadband common-mode impedance response of a transformer under test;
FIG. 2 is a three-stage plot of the broadband common-mode impedance response;
FIG. 3 is a schematic diagram of a converter system;
FIG. 4 is a reference curve of the offline broadband common-mode impedance response of the transformer according to the embodiment;
FIG. 5 is a test wiring diagram;
fig. 6 shows the results of simulation experiments of interlayer dielectric aging between the primary and secondary windings, where (a) is the measured common-mode impedance versus frequency, (b) is the determination index versus frequency, and (c) is the relationship between the determination index and the aging degree;
fig. 7 shows the results of simulation experiments of aging of the insulation between the inner layers of the valve-side winding, in which (a) is a curve showing the variation of the measured common-mode impedance with frequency, (b) is a curve showing the variation of the determination index with frequency, and (c) is a curve showing the relationship between the determination index and the degree of aging.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
The invention provides a method for monitoring interlayer insulation of a converter transformer winding, which comprises the following steps:
(1) the method comprises the steps of obtaining a broadband common-mode impedance response curve of a transformer to be tested under the insulation health condition, and sequentially dividing the transformer to be tested into 3 frequency bands according to the positions of resonance points, wherein the first frequency band is a linear band, the second frequency band is a resonance band, and the third frequency band is a linear band.
In one embodiment, after the valve side and the grid side winding neutral point are connected according to the wiring mode of fig. 1, an impedance analyzer is used to test the offline broadband common-mode impedance response curve of the transformer to be tested under the insulation health condition, and the offline broadband common-mode impedance response curve is used as a reference.
In another embodiment, the offline broadband common-mode impedance response curve is obtained by using a transformer equivalent model calculation. And determining characteristic parameters of components of the common-mode broadband circuit model of the transformer to be tested at each scanning frequency according to the transformer equivalent model of the transformer. In Simulink software, a transformer common-mode broadband circuit model is constructed, excitation under different scanning frequencies is given to solve the response, and a response curve is obtained. The transformer equivalent model adopts the existing calculation model.
In another embodiment, the wideband common-mode impedance response curve is not obtained in an off-line manner, but is measured in an on-line state and stored as a wideband common-mode impedance response curve under an insulation healthy condition when the transformer to be tested initially operates.
The test frequency range of the wide frequency common mode impedance response curve needs to include the resonant frequency band. In other words, the off-line frequency-common mode impedance response curve can be divided into three segments according to the position of the resonance point, such as the general curve Z shown in fig. 20. For different transformer division positions, the first frequency band and the third frequency band are required to be linear bands, and the resonance band is located in the second frequency band.
(2) And measuring an online broadband common-mode impedance response curve under the working state of the transformer to be measured.
As shown in fig. 3, the method for measuring an online wideband common-mode impedance response curve of a converter system, taking phase a as an example, includes the following steps:
i) measuring phase voltage u of phase-A valve side windingapAnd net side neutral point current i0；
ii) calculating uapAnd i0Has a common mode component of amplitude UapAnd I0；
iii) calculating the common-mode impedance response Z, and drawing a three-section online broadband common-mode impedance response in a broadband range.
Those skilled in the art will appreciate that phase a is merely exemplary and should not be construed as limiting the present invention and that phase B and phase C may be used instead to measure the phase voltages and use the magnitudes to calculate the common mode impedance response.
(3) And obtaining a ratio curve of the on-line broadband common-mode impedance and the off-line broadband common-mode impedance as a judgment index, and evaluating the insulation state between winding layers of the transformer to be tested based on the judgment index.
Defining a quantitative determination index
I.e. the ratio of the on-line broadband common-mode impedance response to the off-line reference.
In two linear bands, namely a first band I and a third band III, quantitative evaluation of the aging degree of different interlayer insulation types is made by combining judgment indexes, and when the judgment indexes of the first band I and the third band III are reduced (less than 1), the interlayer insulation aging between a transformer valve side winding and a network side winding is judged; when the first frequency band judgment index is unchanged and the third frequency band judgment index is reduced, the aging of the interlayer insulation inside the transformer valve side or network side winding is judged; when the first and third frequency band indicators are unchanged (equal to 1), it is determined that there is no internal aging. There was no case where the insulation became large, as shown in table 1.
TABLE 1
The invention also provides a system for monitoring the insulation between layers of the converter transformer winding, which realizes the online monitoring of the insulation condition of the transformer by adopting the method. The device comprises a detection module, a storage module and a calculation module;
and the detection module is used for detecting the on-line broadband common-mode impedance response curve measured under the working state of the transformer to be detected. Measuring phase voltage u of any phase valve side windingpAnd net side neutral point current i0(ii) a Calculating upAnd i0Has a common mode component of amplitude UpAnd I0Calculating the common-mode impedance response:
the storage module stores a broadband common-mode impedance response curve of the transformer to be tested under the insulation health condition, and the broadband common-mode impedance response curve is divided into 3 frequency bands according to the positions of resonance points, wherein the first frequency band is a linear band, the second frequency band is a resonance band, and the third frequency band is a linear band. In one embodiment, the storage module stores an offline broadband common-mode impedance response curve. In one embodiment, the storage module stores a broadband common-mode impedance response curve under the insulation health condition as an online measured broadband common-mode impedance response curve, the detection module measures the online broadband common-mode impedance response curve under the working state before the transformer to be detected initially runs, and sends the online broadband common-mode impedance response curve to the storage module to be stored as the broadband common-mode impedance response curve under the insulation health condition, and the 3 frequency bands are defined in advance according to the characteristics of the transformer.
The calculation module calculates a ratio curve of the on-line broadband common-mode impedance and the off-line broadband common-mode impedance as a judgment index, and evaluates the insulation state between winding layers of the transformer to be tested based on the judgment index. The calculation module evaluates the insulation state between winding layers of the transformer to be tested based on the judgment index, and comprises the following steps: when the first frequency band judgment index and the third frequency band judgment index are reduced, judging that the interlayer insulation between the transformer valve side winding and the network side winding is aged; when the first frequency band judgment index is unchanged and the third frequency band judgment index is reduced, the aging of the interlayer insulation inside the transformer valve side or network side winding is judged; and when the first frequency band index and the third frequency band index are not changed, judging that the interior is not aged.
Examples
The transformer is a 15kVA 380/220V three-phase YN/YN wiring dry-type transformer.
As shown in fig. 4, an example transformer was tested for an off-line wide-band common-mode impedance response curve under insulation health conditions using an impedance analyzer as a reference. The first frequency range is less than 100kHz, the second frequency range is 100-200 kHz, and the third frequency range is 200-300 kHz.
As shown in fig. 5, the voltage rich in harmonic content output by the industrial frequency converter is applied to the connection example transformer. Measuring primary side A phase winding phase voltage u by using differential probeapAnd the voltage u across the sampling resistorR0。
Calculating uapAnd uR0Common mode component, the broadband common mode impedance response of the on-line experiment is
Aging simulation experiments were performed for two types of interlayer insulation, respectively:
and (3) carrying out 7%, 20% and 42% aging degree simulation on the interlayer insulation between the primary side winding and the secondary side winding to obtain a real-time online broadband common-mode impedance response curve. FIGS. 6(a) and (b) are a comparison of sets of curves in frequency band I and frequency band III, respectively, and FIG. 6(c) is a comparison of sets of curves in frequency band I and frequency band IIIp1The relation curve of the judgment index and the aging degree calculated in time is good in linearity, and the quantitative evaluation capability is proved to be possessed.
Quantitative evaluation capability is provided for the inter-layer insulation within the valve side winding as shown in fig. 7. And (3) carrying out 20% and 50% aging degree simulation on the interlayer insulation of the primary side winding to obtain a real-time online broadband common-mode impedance response curve.FIGS. 7(a) and (b) are a comparison of sets of curves in frequency band I and frequency band III, respectively, and FIG. 7(c) is a comparison of sets of curves in frequency band I and frequency band IIIp2The relation curve of the time determination index and the aging degree has good linearity, and the capability of quantitative evaluation is proved to be possessed.
In summary, the present invention relates to a method and a system for monitoring insulation between layers of a converter transformer winding, which obtain a wideband common mode impedance response curve of a transformer to be tested under an insulation health condition as a reference; dividing the frequency bands into 3 frequency bands in sequence according to the positions of the resonance points; measuring an online broadband common-mode impedance response curve under the working state of the transformer to be measured; and obtaining a ratio curve of the on-line broadband common-mode impedance and the broadband common-mode impedance under the insulation health condition as a judgment index, and evaluating the insulation state between the winding layers of the transformer to be tested. The invention utilizes the broadband common-mode impedance response curve to evaluate the insulation state of the power transformer, and utilizes different frequency bands of the broadband common-mode impedance response curve to realize different types of interlayer insulation monitoring; by utilizing the judgment indexes, the quantitative evaluation of the aging degree of the interlayer insulation of different types is realized, the interlayer insulation between the valve and the grid side winding and the interlayer insulation state in each side winding can be accurately evaluated, the sensor installation mode is not required to be invaded, and the reliability is high.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.
Claims (8)
1. A method for monitoring insulation between layers of a converter transformer winding is characterized by comprising the following steps:
acquiring a broadband common-mode impedance response curve of a transformer to be tested under an insulation health condition as a reference; dividing the frequency bands into 3 frequency bands in sequence according to the positions of the resonance points, wherein the first frequency band is a linear band, the second frequency band is a resonance band, and the third frequency band is a linear band;
measuring an online broadband common-mode impedance response curve under the working state of the transformer to be measured;
acquiring a ratio curve of online broadband common-mode impedance to broadband common-mode impedance under an insulation health condition as a judgment index, and evaluating the insulation state between winding layers of the transformer to be tested based on the judgment index;
the method for evaluating the insulation state between the winding layers of the transformer to be tested based on the judgment indexes comprises the following steps: when the first frequency band judgment index and the third frequency band judgment index are reduced, judging that the interlayer insulation between the transformer valve side winding and the network side winding is aged; when the first frequency band judgment index is unchanged and the third frequency band judgment index is reduced, the aging of the interlayer insulation inside the transformer valve side or network side winding is judged; and when the first frequency band judgment index and the third frequency band judgment index are not changed, judging that the interior is not aged.
2. The method for monitoring insulation between layers of a converter transformer winding according to claim 1, wherein obtaining a broadband common-mode impedance response curve of a transformer to be tested under insulation health conditions comprises:
and after the valve side and the neutral point of the grid side winding are connected, an impedance analyzer is used for directly measuring to obtain an offline broadband common-mode impedance response curve.
3. The method for monitoring insulation between layers of a converter transformer winding according to claim 1, wherein obtaining a broadband common-mode impedance response curve of a transformer to be tested under insulation health conditions comprises: and calculating by using the equivalent transformer model to obtain an offline broadband common-mode impedance response curve.
4. The method for monitoring insulation between layers of a converter transformer winding according to claim 1, wherein obtaining a broadband common-mode impedance response curve of a transformer to be tested under insulation health conditions comprises: and measuring an online broadband common-mode impedance response curve under the working state of the transformer to be measured during initial operation.
5. According to the rightThe method for monitoring insulation between layers of a converter transformer winding according to any of claims 1 to 4, wherein measuring an online broadband common mode impedance response curve comprises: measuring phase voltage u of any phase valve side windingpAnd net side neutral point current i0(ii) a Calculating upAnd i0Has a common mode component of amplitude UpAnd I0Calculating the common-mode impedance response:
6. a converter transformer winding interlayer insulation monitoring system is characterized by comprising a detection module, a storage module and a calculation module;
the detection module is used for detecting an online broadband common-mode impedance response curve of the transformer to be detected in the working state;
the storage module stores a broadband common-mode impedance response curve of the transformer to be tested under the insulation health condition, and the broadband common-mode impedance response curve is sequentially divided into 3 frequency bands according to the positions of resonance points, wherein the first frequency band is a linear band, the second frequency band is a resonance band, and the third frequency band is a linear band;
the calculation module calculates a ratio curve of the on-line broadband common-mode impedance to the broadband common-mode impedance under the insulation health condition as a judgment index, and evaluates the insulation state between winding layers of the transformer to be tested based on the judgment index;
the calculation module evaluates the insulation state between winding layers of the transformer to be tested based on the judgment index, and comprises the following steps: when the first frequency band judgment index and the third frequency band judgment index are reduced, judging that the interlayer insulation between the transformer valve side winding and the network side winding is aged; when the first frequency band judgment index is unchanged and the third frequency band judgment index is reduced, the aging of the interlayer insulation inside the transformer valve side or network side winding is judged; and when the first frequency band judgment index and the third frequency band judgment index are not changed, judging that the interior is not aged.
7. The converter transformer winding interlayer insulation monitoring system according to claim 6, characterized in thatCharacterized in that, the detection module detects the online broadband common mode impedance response curve of the transformer to be detected under the working state, and comprises: measuring phase voltage u of any phase valve side windingpAnd net side neutral point current i0(ii) a Calculating upAnd i0Has a common mode component of amplitude UpAnd I0Calculating the common-mode impedance response:
8. the system for monitoring insulation between converter transformer winding layers according to claim 6 or 7, wherein the detection module measures an online broadband common-mode impedance response curve in an operating state before the transformer to be tested initially runs, and sends the online broadband common-mode impedance response curve to the storage module for storage as the broadband common-mode impedance response curve in an insulation health state.
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