A method and system for on-line testing of a reactor

Abstract

The application discloses an online test method and system for a reactor, and relates to the technical field of online test, and comprises the following steps: introducing low-energy direct current into the winding of a reactor to be put into operation to form a preset energy storage state; based on the preset energy storage state, the direct current is instantaneously cut off through a series arc extinguishing unit, and high-frequency oscillation is excited by using the capacitive component of the winding and an existing lightning arrester to the ground; a transient current response sequence corresponding to the instantaneously cut-off moment is obtained on the ground wire of the lightning arrester; the first amplitude, the peak value decay ratio and the main oscillation period are determined from the response sequence to generate a transient decay characteristic; and the transient decay characteristic is compared with a reference interval to determine the inter-turn insulation state. The application introduces low-energy direct current and instantaneously cuts off the current to excite high-frequency transient response, so as to solve the problem that the prior art is difficult to stably excite and collect high-frequency transient response with sufficient distinguishability for the inter-turn insulation abnormality of the reactor under the conditions of low additional energy and low site modification.

Description

Technical Field

[0001] This invention relates to the field of online testing technology, and more specifically, to a method and system for online testing of reactors. Background Technology

[0002] Reactors are crucial devices in power systems used for reactive power regulation, voltage control, and overcurrent limiting. The insulation condition of their windings, especially the inter-turn insulation, directly affects the safety of equipment operation and the stability of the system. For reactors that are in standby or intermittent operation for extended periods, early inter-turn insulation defects may gradually form inside the windings due to factors such as thermal aging, mechanical stress, and deterioration of insulation material performance. These defects are often difficult to identify directly through routine visual inspection or general steady-state parameter testing before the equipment is put into operation. Once put into operation with defects, they are prone to further development under electromagnetic transients, causing equipment damage or even more serious operational accidents.

[0003] In existing technologies, the detection of the insulation status of reactors mostly relies on power outage tests, conventional withstand voltage tests, or online monitoring after operation. However, under conditions of low additional energy and minimal on-site modifications, it is difficult to construct a high-frequency transient response with sufficient distinguishability for inter-turn insulation anomalies. In particular, it is difficult to achieve stable excitation and effective acquisition of this transient response without affecting the normal operation wiring structure of the equipment.

[0004] The above-disclosed technical solutions have at least the following technical problems: Under conditions of low additional energy and low on-site modification, the existing technology has difficulty in constructing a high-frequency transient response with sufficient distinguishability for reactor inter-turn insulation abnormalities, and in particular, it is difficult to achieve stable excitation and acquisition of the transient response without affecting the normal operation wiring structure of the equipment. Summary of the Invention

[0005] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide an online testing method and system for reactors. By introducing low-energy DC and implementing instantaneous current cutoff to excite a high-frequency transient response, and then determining the inter-turn insulation state based on the acquired transient attenuation characteristics, the present invention solves the problem that the prior art is unable to stably excite and acquire a high-frequency transient response with sufficient distinguishability for reactor inter-turn insulation anomalies under conditions of low additional energy and low on-site modification.

[0006] To achieve the above objectives, the present invention provides the following technical solution: On the one hand, an online testing method for a reactor includes the following steps: introducing low-energy DC to the winding of the reactor to be put into operation to form a preset energy storage state; based on the preset energy storage state, instantaneously cutting off the DC current through a series arc extinguishing unit, and using the ground capacitive component of the winding and the existing surge arrester to excite high-frequency oscillation; Obtain the transient current response sequence corresponding to the instantaneous current cut-off moment on the grounding lead of the surge arrester; determine the first amplitude value, peak attenuation ratio and main oscillation period from the response sequence to generate transient attenuation characteristics; compare the transient attenuation characteristics with the reference interval to determine the inter-turn insulation status.

[0007] In a preferred embodiment, the step of introducing low-energy DC to the winding of the reactor to be put into operation to form a preset energy storage state includes: injecting DC test current into the reactor winding and monitoring the current change rate; when the current change rate is lower than a preset threshold for a continuous preset period of time, determining that the winding has entered a stable conduction state; determining the winding energy storage based on the stable current value; and forming a preset energy storage state when the energy storage reaches the preset threshold.

[0008] In a preferred embodiment, determining the winding energy storage based on the stable current value includes: Obtain the equivalent inductance parameters of the reactor winding under low-energy DC test conditions; read the test current value under stable conduction conditions; calculate the winding magnetic field energy storage value based on the equivalent inductance parameters and test current value, as a quantitative characterization of the winding energy storage level.

[0009] In a preferred embodiment, the step of instantaneously interrupting the DC current through a series arc-extinguishing unit based on a preset energy storage state, and using the capacitive component of the winding and the existing surge arrester to excite high-frequency oscillations, includes: latching the test current value under a stable conduction state as an energy release reference; triggering the series arc-extinguishing unit to instantaneously disconnect when the test current value remains within a preset fluctuation range, so that the energy stored in the winding is injected into the capacitive component circuit of the surge arrester to the ground; monitoring the response current in the grounding lead of the surge arrester, identifying the first reverse current peak value within a preset short time window after the current interruption, thereby determining the formation of high-frequency oscillations.

[0010] In a preferred embodiment, the step of forming the high-frequency oscillation includes: taking the current-cutting moment as the oscillation start moment; performing zero-crossing detection and extreme value search on the response current of the arrester grounding lead within a preset determination time window to identify the first local peak with the opposite direction of the current before current-cutting; calculating the expected time delay range of the first half-cycle of the high-frequency oscillation based on the equivalent inductance of the winding and the arrester-to-ground capacitance; comparing the actual arrival time delay of the first local peak with the expected range; if the time delay falls within the expected time delay range, and there is at least one subsequent peak with opposite polarity after the first local peak, then it is determined that the high-frequency oscillation has formed.

[0011] In a preferred embodiment, the step of calculating the expected time delay range of the first half-cycle of the high-frequency oscillation based on the equivalent inductance of the winding and the capacitance to ground of the surge arrester includes: calculating the nominal period of the high-frequency oscillation based on the equivalent inductance parameters of the winding and the capacitance to ground of the surge arrester, and taking half of it as the nominal time delay of the first half-cycle; determining the comprehensive time delay tolerance based on the discrete time difference of the arc extinguishing unit, the time delay deviation caused by the parameter tolerance, and the time delay error introduced by the sampling resolution; and forming the expected time delay range by taking the nominal time delay of the first half-cycle as the center and combining it with the comprehensive time delay tolerance.

[0012] In a preferred embodiment, the acquisition of the transient current response sequence includes: within a preset baseline time window before the instantaneous current cut-off, collecting the background current through a high-frequency open current transformer fitted onto the grounding lead of the surge arrester to establish a background response baseline; monitoring the test branch current, and determining the actual current cut-off time as the moment when the test branch current drops to a preset threshold and does not recover; setting a disturbance shielding time window from the actual current cut-off time based on the arc extinguishing unit's discrete time difference and the duration of the disturbance, and marking the sampled data within it as invalid response segments.

[0013] In a preferred embodiment, the extraction of the transient current response sequence includes: after the disturbance shielding time window ends, identifying the reverse current peak with the opposite direction to the test current before current cutoff within the expected time delay range of the first half-cycle, as the starting response point; extracting subsequent decaying peak segments whose peak intervals fall within the preset half-cycle tolerance range and whose polarities alternate sequentially; associating the starting response point and the effective decaying peak segments in chronological order, and subtracting the background response baseline to obtain the transient current response sequence corresponding to the instantaneous current cutoff time.

[0014] In a preferred embodiment, determining the initial amplitude, peak attenuation ratio, and main oscillation period from the response sequence to generate transient attenuation characteristics includes: extracting subsequent local peaks in chronological order, starting from the initial response point corresponding to the reverse current peak; filtering out abnormal peaks and constructing an effective oscillation peak chain based on the alternating polarity relationship of peaks and the time interval between adjacent peaks of opposite and same polarity; taking the amplitude of the first effective peak in the peak chain as the initial amplitude, calculating the peak attenuation ratio from the amplitude ratio of adjacent peaks of the same polarity, and determining the main oscillation period from the time interval between adjacent peaks of the same polarity; and combining the initial amplitude, peak attenuation ratio, and main oscillation period to form transient attenuation characteristics.

[0015] On the other hand, an online testing system for reactors includes the following modules: an energy storage preset module, used to introduce low-energy DC to the winding of the reactor to be put into operation to form a preset energy storage state; an instantaneous current-cutting excitation module, used to instantaneously cut off the DC current through a series arc-extinguishing unit based on the preset energy storage state, and to excite high-frequency oscillations using the capacitive component of the winding and the existing surge arrester to ground; a transient response acquisition module, used to acquire the transient current response sequence corresponding to the instantaneous current-cutting moment on the grounding lead of the surge arrester; an attenuation characteristic analysis module, used to determine the initial amplitude, peak attenuation ratio and main oscillation period from the response sequence, and generate transient attenuation characteristics; and an insulation anomaly determination module, used to compare the transient attenuation characteristics with a reference interval to determine the inter-turn insulation status.

[0016] The technical effects and advantages of the online testing method and system for reactors of this invention are as follows: This invention first introduces low-energy DC to the reactor to be put into operation while it is still in its on-site installation state to form controllable energy storage. Then, a series arc-extinguishing interruption unit is used to instantaneously cut off the DC test current, so that the energy storage in the winding and the capacitive component of the existing surge arrester to ground form a high-frequency oscillation. The corresponding transient response is non-intrusively collected on the grounding lead of the surge arrester, and transient attenuation characteristics such as the initial amplitude, peak attenuation ratio and main oscillation period are extracted. After comparison with the reference interval, the inter-turn insulation status is determined. Thus, without changing the on-site installation state of the reactor and without the need for additional complex high-voltage testing equipment, it is possible to quickly screen for potential inter-turn insulation problems before commissioning. This method is beneficial to improving the convenience and consistency of test implementation, and can enhance the ability to identify early inter-turn insulation anomalies through transient response characteristics, and has good on-site applicability. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating an online testing method for reactors according to the present invention. Figure 2 This is a schematic diagram of the structure of an online reactor testing system according to the present invention; Figure 3 This is the test circuit diagram for the reactor; Figure 4 This is a schematic diagram of the wiring and transient response acquisition principle for online testing of reactors. Figure 5 Comparison of high-frequency transient response of the grounding lead of the surge arrester. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1, Figure 1 This invention provides an online testing method for reactors, comprising the following steps: S1, low-energy DC is introduced into the winding of the reactor to be put into operation to form a preset energy storage state; In this embodiment, the process of introducing low-energy DC into the winding of the reactor to be put into operation to form a preset energy storage state includes: Under the condition that the reactor is in the isolation state before commissioning and the on-site installation wiring structure remains unchanged, connect the low-energy test branch between the high-voltage end and the grounding end of the reactor; Control the low-energy test branch to conduct, so that the DC power supply introduces DC test current into the reactor winding through the series protection and disconnection unit; The process of collecting the change of the DC test current is determined, and when the rate of change of the DC test current within a continuous preset time period is less than a preset slope threshold, the winding current is determined to have entered a stable conduction state. The continuous preset time period is specifically obtained by performing multiple low-energy DC input tests on the same type of healthy reactor, recording the length of time during which the rate of change of the current first drops to the stable range and remains there, and obtaining multiple stable duration samples. The statistical quantile value of the stable duration samples is used as the continuous preset time period. The preset slope threshold is specifically obtained by extracting the absolute value of the rate of change of the current after entering the stable segment in the low-energy DC input test of the same type of healthy reactor, establishing a stable state rate of change sample set, and using the upper envelope statistical value of this sample set as the preset slope threshold. The winding energy storage level is determined based on the test current value under stable conduction conditions, and the winding is deemed to have formed a preset energy storage state when the energy storage level reaches a preset energy storage threshold. The preset energy storage threshold is specifically obtained as follows: the corresponding energy storage level is calculated based on the test current value under stable conduction conditions and the equivalent inductance parameters of the winding, and a minimum identifiable energy storage threshold is determined in conjunction with the minimum identifiable requirement of the first amplitude value; under the condition that the minimum identifiable energy storage threshold does not exceed the upper limit of the safe breaking energy of the series arc-extinguishing breaking unit, the minimum identifiable energy storage threshold or the value after setting its safety margin is determined as the preset energy storage threshold.

[0020] Furthermore, determining the winding energy storage level based on the test current value under stable conduction conditions includes: Obtain the equivalent inductance parameters of the winding of the reactor under low-energy DC test conditions; Read the test current value under stable conduction conditions; The energy storage value of the winding magnetic field is calculated based on the equivalent inductance parameters of the winding and the test current value. The magnetic field energy storage value is used as the winding energy storage level, or the magnetic field energy storage value is compared with a preset energy storage threshold. When the magnetic field energy storage value reaches the preset energy storage threshold, the winding is determined to have reached the preset energy storage state.

[0021] The specific formula for calculating the energy storage value of the winding magnetic field is as follows:

[0022] in, This represents the energy stored in the winding magnetic field. This represents the equivalent winding inductance of the reactor under low-energy DC test conditions. The test current value is the value under stable conduction conditions.

[0023] S2, based on the preset energy storage state, instantaneously cuts off the DC current through the series arc extinguishing unit, and uses the winding and the existing surge arrester to excite high-frequency oscillations to the ground capacitive component; In this embodiment, the step of instantaneously interrupting the DC current through a series arc-extinguishing unit based on a preset energy storage state, and using the winding and existing surge arrester to excite high-frequency oscillations to the ground capacitive component, includes: The test current value under stable conduction state is latched, and the winding energy storage level corresponding to the test current value is used as the energy release benchmark for this current cut-off. During the current-cutting window when the test current value is kept within the preset fluctuation range, the series arc-extinguishing interruption unit is synchronously triggered to switch from the conducting state to the high blocking state, so that the winding energy storage is separated from the low energy test branch and preferentially injected into the charging and discharging circuit corresponding to the existing arrester's ground capacitive component. Monitor the response current in the grounding lead of the surge arrester and identify the first reverse current peak within a preset short time window after current cut-off; Upon detecting the first reverse current peak, it was determined that the energy stored in the winding had been converted into high-frequency oscillations between the winding and the existing arrester's capacitive component to ground. If the first reverse current peak is not detected or the time delay of the first reverse current peak exceeds the preset range, it is determined that the current throttling has not formed an effective high-frequency oscillation, and the low-energy DC input and instantaneous current throttling are re-executed.

[0024] Furthermore, the step of determining, upon identifying the first reverse current peak, that the winding energy storage has been converted into high-frequency oscillations between the winding and the existing surge arrester's capacitive component to ground includes: The moment when the series arc-extinguishing and interrupting units complete the flow cutoff is taken as the oscillation start moment; Within a preset judgment time window after the oscillation initiation time, zero-crossing detection and extreme value search are performed on the response current in the grounding lead of the surge arrester to identify the first local peak value that is opposite to the current direction before the current cut-off. Based on the equivalent inductance parameters of the winding and the ground capacitance parameters of the existing surge arrester, the expected time delay range of the first half-cycle of the corresponding high-frequency oscillation is determined. Calculate the peak arrival delay of the first local peak relative to the oscillation start time, and determine whether the peak arrival delay falls within the expected delay range; When the arrival delay of the peak falls within the expected delay range, and at least one subsequent peak of opposite polarity is detected after the first local peak, it is determined that the winding energy storage has been converted into high-frequency oscillation between the winding and the existing arrester's capacitive component to ground.

[0025] It should be noted that determining the expected time delay range of the first half-cycle of the corresponding high-frequency oscillation based on the equivalent inductance parameters of the winding and the existing surge arrester's ground capacitance parameters includes: Obtain the equivalent inductance parameters of the reactor winding and the ground capacitance parameters of the existing surge arrester; Based on the equivalent inductance parameters and the ground capacitance parameters, the nominal period of the corresponding high-frequency oscillation is calculated, and half of the nominal period is determined as the nominal delay of the first half-cycle. Obtain the discrete time difference of the series arc extinguishing interruption unit, the calculation deviation caused by the parameter tolerance, and the time delay error corresponding to the response sampling resolution; The discrete time difference of the interruption, the calculation deviation and the time delay error are superimposed to form a comprehensive time delay tolerance; Based on the nominal delay of the first half-cycle and the comprehensive delay tolerance, the expected delay range for the first half-cycle of the corresponding high-frequency oscillation is determined.

[0026] The nominal period of the high-frequency oscillation is specifically calculated using the following formula:

[0027] in, The nominal period of the high-frequency oscillation. These are the equivalent inductance parameters of the winding. These are the existing surge arrester's ground capacitance parameters.

[0028] The acquisition of the discrete time difference of the series arc extinguishing interruption unit, the calculation deviation caused by the parameter tolerance, and the time delay error corresponding to the response sampling resolution includes: Under multiple no-load current cut-off conditions, the time difference between the interruption trigger moment and the actual current drop to zero of the series arc extinguishing interruption unit is recorded, the distribution interval of the time difference is statistically analyzed, and the half width corresponding to the distribution interval is determined as the interruption discrete time difference. Obtain the nominal values ​​and allowable deviation ranges of the winding equivalent inductance parameters and the existing surge arrester ground capacitance parameters. Calculate the nominal time delay of the first half-cycle corresponding to different parameter boundary values, and determine half of the difference between the maximum and minimum time delays as the calculation deviation caused by parameter tolerance. Based on the response sampling period, the maximum time resolution interval between adjacent sampling points is determined, and half of the maximum time resolution interval is determined as the time delay error corresponding to the response sampling resolution. The discrete time difference of the interruption, the calculation deviation, and the time delay error are superimposed to obtain the comprehensive time delay tolerance.

[0029] S3, obtain the transient current response sequence corresponding to the instantaneous current cut-off moment on the grounding lead of the surge arrester; In this embodiment, obtaining the transient current response sequence corresponding to the instantaneous current cutoff moment on the grounding lead of the surge arrester includes: Within the preset baseline time window before instantaneous current cutoff, the background current response in the grounding down conductor is collected by a high-frequency open current transformer fitted on the grounding down conductor of the surge arrester, and the baseline of the background response corresponding to this test is established. Monitor the current in the test branch, and determine the actual current cut-off time as the moment when the current in the test branch drops to a preset cut-off threshold and does not recover. Use the actual current cut-off time as the data acquisition time anchor point. Based on the discrete time difference of the interruption of the series arc extinguishing interruption unit and the duration of the arc extinguishing disturbance, the disturbance shielding time window starting from the actual cut-off time is determined; The sampled data within the disturbance shielding window is marked as an invalid response segment and is not included in the subsequent high-frequency oscillation response extraction. After the disturbance shielding time window ends, the peak value of the reverse current relative to the direction of the test current before current cutoff is searched within the expected time delay range of the first half-week, and the peak value of the reverse current is determined as the starting response point. Starting from the initial response point, extract subsequent decaying peak segments whose peak intervals fall within a preset half-cycle tolerance range and whose peak polarities alternate sequentially. By associating the starting response point and the subsequent effective attenuation peak segments in chronological order and subtracting the baseline response, a transient current response sequence corresponding to the instantaneous current cutoff moment is obtained.

[0030] It should be noted that, because the surge arrester grounding lead simultaneously experiences interruption spikes, arc-extinguishing disturbances, and background interference at the moment of current throttling, directly analyzing the waveform over the entire time period could easily lead to misidentification of non-target transients as oscillating responses. Therefore, this implementation method first establishes a baseline response before current throttling, then sets a disturbance shielding window using the actual current throttling moment as the time anchor point to eliminate unstable disturbance components in the initial interruption phase. Subsequently, only subsequent peak segments that satisfy the expected time delay and polarity alternation pattern of the first half-cycle are extracted, thereby forming a transient current response sequence corresponding to this instantaneous current throttling.

[0031] S4. Determine the initial amplitude, peak decay ratio, and main oscillation period from the response sequence to generate transient decay characteristics; In this embodiment, the step of determining the initial amplitude, peak attenuation ratio, and main oscillation period based on the transient current response sequence, and generating transient attenuation characteristics, includes: Starting from the initial response point corresponding to the peak of the reverse current, the subsequent local peaks are extracted in the transient current response sequence in chronological order, and the occurrence time, polarity, and amplitude of each local peak are recorded. Based on whether the time interval between adjacent peaks of opposite polarity falls within the expected delay range of the first half-cycle, and whether the time interval between adjacent peaks of the same polarity falls within the tolerance range corresponding to the nominal oscillation period, abnormal peaks are screened out, and an effective oscillation peak chain is constructed; let the local peaks extracted from the transient current response sequence be denoted in chronological order as: ,in Let k be the time when the k-th local peak occurs. The amplitude of the kth local peak, The polarity of the k-th local peak is given by a value of +1 or 0. 1. After filtering out abnormal peaks, the effective oscillating peak chain is obtained:

[0032] Read the amplitude of the first effective peak in the effective oscillation peak chain, and perform amplitude conversion in combination with the energy release benchmark corresponding to this interception to determine the amplitude of the first oscillation; Calculate the amplitude ratio of adjacent peaks of the same polarity in the effective oscillation peak chain to determine the peak attenuation ratio; Calculate the time interval between adjacent peaks of the same polarity in the effective oscillation peak chain, and determine the main oscillation period based on the representative value of the time interval; The initial amplitude value, the peak attenuation ratio, and the main oscillation period are combined to form a transient attenuation characteristic group. , which serves as the transient decay characteristic characterizing the dissipation properties of the transient current response sequence.

[0033] The time interval between adjacent opposite polarity peaks Meets the expected latency range for the first half of the week The time interval between adjacent peaks of the same polarity Satisfying the nominal oscillation period tolerance range When the peak value is reached, the corresponding peak value is retained.

[0034] Preferably, the absolute amplitude of the first effective peak value is set to The energy release benchmark is Then the first amplitude value Let the peak sequence of the same polarity be... Then the local attenuation ratio , Peak attenuation ratio Let the interval between adjacent peaks of the same polarity be... Then the main oscillation period .

[0035] S5 compares the transient attenuation characteristics with the reference range to determine the inter-turn insulation status.

[0036] In this embodiment, the step of comparing the transient attenuation characteristics with the reference interval to determine the inter-turn insulation state includes: Based on the energy release reference, wiring structure and environmental conditions corresponding to this experiment, the corresponding reference ranges for the first amplitude value, peak attenuation ratio and main oscillation period are selected from the pre-established reference feature library. The initial amplitude, peak attenuation ratio, and main oscillation period of the transient decay characteristics are compared with the upper and lower limits of the corresponding reference intervals to determine the offset direction and amount of each characteristic relative to the corresponding reference interval. Specifically, if the initial amplitude is lower than the lower limit, it is defined as a negative offset; if the peak attenuation ratio is higher than the upper limit, it is defined as a positive offset; if the main oscillation period is lower than the lower limit or higher than the upper limit, it is defined as a negative offset or a positive offset, respectively. When the initial amplitude value is lower than the lower limit of its reference range and the low output reaches the preset initial amplitude offset threshold, and the peak attenuation ratio is higher than the upper limit of its reference range and the high output reaches the preset attenuation ratio offset threshold, it is determined that there is an oscillation dissipation enhancement offset. After confirming the existence of enhanced oscillation dissipation offset, it is further determined whether the main oscillation period falls within the corresponding main oscillation period reference range; When the main oscillation period falls within the corresponding reference range, and the first amplitude value is lower than the corresponding lower limit and the peak attenuation ratio is higher than the corresponding upper limit in at least two consecutive tests, it is determined that the reactor has an inter-turn insulation abnormality. When the initial amplitude, peak attenuation ratio, and main oscillation period all fall within the corresponding reference range, the inter-turn insulation condition is determined to be normal. If the main oscillation period exceeds the corresponding reference range and no oscillation dissipation enhancement offset is detected, the current response is determined not to meet the inter-turn insulation abnormality characteristic mode, and a retest command is output.

[0037] Example 2, Figure 2 The present invention discloses an online testing system for reactors, comprising the following modules: Energy storage preset module: used to introduce low-energy DC to the winding of the reactor to be put into operation to form a preset energy storage state; Instantaneous current-cutting excitation module: It is used to instantaneously cut off the DC current by connecting the arc-extinguishing unit in series based on the preset energy storage state, and to excite high-frequency oscillation by using the ground capacitive component of the winding and the existing surge arrester. Transient response acquisition module: used to acquire the transient current response sequence corresponding to the instantaneous current cut-off moment on the grounding lead of the surge arrester; Attenuation characteristic analysis module: used to determine the initial amplitude, peak attenuation ratio and main oscillation period from the response sequence, and generate transient attenuation characteristics; Insulation anomaly determination module: used to compare transient attenuation characteristics with the reference range to determine the inter-turn insulation status.

[0038] Figure 3 A test apparatus for implementing the above-described online test method is provided, comprising a high-voltage fuse 1, a vacuum contactor 2, a dry cell battery pack 3, a storage oscilloscope 4, and a high-frequency open-circuit current transformer 5. The high-voltage fuse 1, the three-phase high-voltage arc-extinguishing chambers of the vacuum contactor 2, and the dry cell battery pack 3 are connected in series to form a low-energy test branch. One end of the low-energy test branch is connected to the high-voltage terminal of the reactor under test, and the other end is connected to the grounding terminal of the reactor under test. The signal input terminal of the storage oscilloscope 4 is connected to the secondary winding of the high-frequency open-circuit current transformer 5, which is clamped to the grounding lead of the surge arrester of the reactor under test.

[0039] In this embodiment, the withstand voltage rating of the high-voltage fuse 1 is greater than 1.5 times the AC grid voltage at which the reactor operates. The vacuum contactor 2 adopts a three-phase structure, with the three-phase arc-extinguishing chambers connected in series to improve the arc-extinguishing capability when the DC circuit is interrupted; the rated voltage of each arc-extinguishing chamber can be 10kV. The vacuum contactor 2 is also equipped with a wireless remote control opening and closing mechanism to enable remote control during testing.

[0040] During the test, vacuum contactor 2 is first closed, allowing the low-voltage DC current output from the dry cell battery pack 3 to flow into the winding of the reactor under test through the high-voltage fuse 1 and vacuum contactor 2, thus creating a low-energy storage state in the winding. Subsequently, after the preset test conditions are met, vacuum contactor 2 is quickly opened. Due to the strong current-cutting capacity of the series arc-extinguishing chamber, the DC current in the winding is instantaneously cut off, thereby forming a chopped overvoltage at both ends of the winding. The chopped overvoltage, together with the ground capacitive component of the reactor's existing surge arrester, forms a high-frequency transient oscillation response.

[0041] The high-frequency transient oscillation response, transmitted through the grounding lead of the surge arrester, manifests as a corresponding transient current signal. This signal is non-invasively acquired by the high-frequency open-type current transformer 5 and recorded in the storage oscilloscope 4. By analyzing the characteristics of the recorded waveform, such as the initial amplitude, decay rate, and oscillation period, it can be determined whether the inter-turn insulation state of the reactor winding is normal. If there is an abnormality in the inter-turn insulation of the reactor, its equivalent dissipation component will increase, leading to a weakening and accelerated decay of the high-frequency transient oscillation response, and even making it difficult to form a stable oscillation. Based on this, it is possible to detect potential inter-turn insulation defects in the reactor before commissioning.

[0042] In this embodiment, the low-energy test branch remains disconnected during normal reactor operation, thus not substantially affecting the reactor's normal operating circuit. Furthermore, this embodiment utilizes the existing surge arrester branch at the reactor site to construct the transient response, eliminating the need for additional large-capacity high-voltage capacitors, which helps reduce the complexity and implementation cost of the on-site testing equipment.

[0043] Figure 4 This is a schematic diagram of the wiring and transient response acquisition principle for the online test of the reactor of the present invention. The online test device in this embodiment includes a high-voltage fuse, a vacuum contactor, a dry battery pack or DC power supply, a storage oscilloscope, and a high-frequency open-ended current transformer. The high-voltage fuse, vacuum contactor, and dry battery pack or DC power supply are connected in series to form a low-energy test branch. This low-energy test branch is connected between the high-voltage terminal and the grounding terminal of the reactor to be put into operation, and is used to introduce low-energy DC to the reactor winding, causing the winding to form a preset energy storage state. After the preset test conditions are met, the vacuum contactor is controlled to quickly open, instantaneously cutting off the DC test current, so that the energy stored in the winding and the capacitive component to ground of the existing surge arrester together form a high-frequency transient oscillation circuit. The high-frequency open-ended current transformer is sleeved on the grounding lead of the surge arrester, and non-invasively acquires the transient current response exhibited by the high-frequency transient oscillation in the grounding lead, and sends the acquired signal to the storage oscilloscope for waveform recording and feature extraction. This figure mainly illustrates the implementation method of the present invention, which utilizes the existing surge arrester branch to construct high-frequency oscillation and complete transient response acquisition without changing the on-site installation state of the reactor.

[0044] Figure 5 This diagram illustrates the significant differences in transient current responses collected by high-frequency open-type current transformers when the arrester grounding lead is in a healthy state and an abnormal state under the same low-energy excitation conditions. The horizontal axis represents time in milliseconds; the vertical axis represents the transient current response amplitude, characterizing the strength of transient current changes on the grounding lead during high-frequency oscillations.

[0045] The blue curve in the figure represents the transient current response under healthy conditions, while the orange curve represents the transient current response under abnormal grounding conditions. It can be seen that in the initial stage of the transient response, the first oscillation peak of the healthy state curve is significantly larger. This indicates that when the arrester's grounding down conductor connection is normal and the circuit continuity is good, the high-frequency oscillation signal formed after low-energy triggering can be sufficiently coupled into the grounding down conductor path, resulting in a higher amplitude of the acquired transient current.

[0046] In contrast, under the abnormal state corresponding to the orange curve, the peak value of the transient response is significantly reduced, especially in the first few oscillation cycles, where the peak amplitude is lower than that of the healthy state curve. This indicates that when there are issues such as loose grounding leads, poor contact, local cracks, increased grounding loop impedance, or discontinuities in the high-frequency path, the transmission of high-frequency transient energy in the grounding path is weakened, resulting in a decrease in the response amplitude collected by the high-frequency open-circuit transformer.

[0047] From the perspective of oscillation decay characteristics, the healthy state curve maintains a relatively obvious oscillating waveform over a longer period, with a relatively slow decay process; the abnormal state curve, on the other hand, approaches zero more quickly, with a faster decrease in oscillation amplitude. This difference indicates that changes in the state of the grounding down conductor not only affect the initial peak value of the transient response but also alter the damping characteristics and energy decay rate during the oscillation process. This embodiment, by acquiring the high-frequency transient current response at the grounding down conductor of the surge arrester and extracting the peak amplitude, decay rate, and oscillation duration characteristics, can distinguish between the healthy and abnormal states of the grounding down conductor, thus providing a basis for online identification of abnormal grounding down conductor connections.

[0048] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Without departing from the technical concept of the present invention, those skilled in the art can make equivalent substitutions or modifications to the device structure, device parameters, and control methods, and such equivalent substitutions or modifications should all fall within the scope of protection of the present invention.

[0049] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0050] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0051] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0052] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0053] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0054] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for online testing of reactors, characterized in that, Includes the following steps: Low-energy DC is introduced into the winding of the reactor to be put into operation to form a preset energy storage state; Based on the preset energy storage state, the DC current is instantly cut off by the series arc extinguishing unit, and high-frequency oscillation is excited by the ground capacitive component of the winding and the existing surge arrester. Obtain the transient current response sequence corresponding to the instantaneous current cut-off moment on the grounding lead of the surge arrester; The initial amplitude, peak decay ratio, and main oscillation period are determined from the response sequence to generate transient decay characteristics; The transient attenuation characteristics are compared with the reference range to determine the inter-turn insulation status.

2. The online testing method for reactors according to claim 1, characterized in that, The process of introducing low-energy DC into the winding of the reactor to be put into operation to form a preset energy storage state includes: Inject DC test current into the reactor winding and monitor the rate of change of current. When the rate of change of current within a preset time period is lower than a preset threshold, the winding is determined to enter a stable conduction state. The winding energy storage is determined based on the stable current value. When the energy storage reaches the preset threshold, a preset energy storage state is formed.

3. The online testing method for reactors according to claim 2, characterized in that, The determination of winding energy storage based on stable current value includes: Obtain the equivalent inductance parameters of the reactor windings under low-energy DC test conditions; Read the test current value under stable conduction conditions; The energy storage value of the winding magnetic field is calculated based on the equivalent inductance parameters of the winding and the test current value, which serves as a quantitative characterization of the energy storage level of the winding.

4. The online testing method for reactors according to claim 3, characterized in that, The method, based on a preset energy storage state, instantaneously interrupts the DC current through a series arc-extinguishing unit, and utilizes the ground capacitive component of the winding and existing surge arrester to generate high-frequency oscillations, includes: The test current value under the latched stable conduction state is used as the energy release reference; When the test current value remains within the preset fluctuation range, the series arc extinguishing and breaking unit is triggered to disconnect instantaneously, so that the winding energy storage is injected into the ground capacitive component circuit of the surge arrester. Monitor the response current in the grounding lead of the surge arrester, and identify the first reverse current peak within a preset short time window after current cutoff, thereby determining the formation of high-frequency oscillation.

5. The online testing method for reactors according to claim 4, characterized in that, The steps for generating the high-frequency oscillation include: The moment of damming is taken as the starting moment of oscillation; Within a preset judgment time window, zero-crossing detection and extreme value search are performed on the response current of the grounding lead of the surge arrester to identify the first local peak value that is opposite to the current direction before current cutoff. The expected time delay range of the first half cycle of the high-frequency oscillation is calculated based on the equivalent inductance of the winding and the capacitance to ground of the surge arrester. Compare the actual arrival delay of the first local peak with the expected range; If the delay falls within the expected delay range, and there is at least one subsequent peak of opposite polarity after the first local peak, then a high-frequency oscillation is determined to have formed.

6. The online testing method for reactors according to claim 5, characterized in that, The calculation of the expected time delay range of the first half-cycle of the high-frequency oscillation based on the equivalent inductance of the winding and the capacitance to ground of the surge arrester includes: The nominal period of the high-frequency oscillation is calculated based on the equivalent inductance parameters of the winding and the capacitance to ground of the surge arrester, and half of this period is taken as the nominal time delay of the first half cycle. Based on the discrete time difference of the arc extinguishing unit, the time delay deviation caused by the parameter tolerance, and the time delay error introduced by the sampling resolution, the comprehensive time delay tolerance is determined. The expected latency range is formed by taking the nominal latency of the first half of the week as the center and combining it with the comprehensive latency tolerance.

7. The online testing method for reactors according to claim 6, characterized in that, The acquisition of the transient current response sequence includes: Within the preset baseline time window before instantaneous current cutoff, the background current is collected by a high-frequency open current transformer fitted onto the grounding lead of the surge arrester to establish the background response baseline. The actual current cutoff time is defined as the moment when the test branch current drops to a preset threshold and remains there without recovering. Based on the discrete time difference of the arc extinguishing unit and the duration of the disturbance, a disturbance shielding time window is set from the actual cut-off time, and the sampled data within it is marked as invalid response segments.

8. The online testing method for reactors according to claim 1 or 7, characterized in that, The extraction of the transient current response sequence includes: After the disturbance shielding time window ends, identify the reverse current peak that is opposite to the direction of the test current before current cutoff within the expected time delay range of the first half-week, and use it as the starting response point; Extract subsequent decaying peak segments whose peak intervals fall within a preset half-cycle tolerance range and whose polarities alternate sequentially; By correlating the starting response point and the effective attenuation peak segment in chronological order and subtracting the baseline response, a transient current response sequence corresponding to the instantaneous current cutoff moment is obtained.

9. The online testing method for reactors according to claim 8, characterized in that, The step of determining the initial amplitude, peak attenuation ratio, and main oscillation period from the response sequence to generate transient attenuation characteristics includes: Starting from the initial response point corresponding to the peak of the reverse current, subsequent local peaks are extracted in chronological order. Based on the alternation of peak polarity and the time interval between adjacent peaks of opposite and same polarity, abnormal peaks are screened out to construct an effective oscillating peak chain; The amplitude of the first effective peak in the peak chain is taken as the first oscillation amplitude. The peak attenuation ratio is calculated by the amplitude ratio of adjacent peaks of the same polarity. The main oscillation period is determined by the time interval of adjacent peaks of the same polarity. The initial amplitude, peak attenuation ratio, and main oscillation period are combined to form the transient attenuation characteristics.

10. A system using the online testing method for reactors as described in any one of claims 1-9, characterized in that, Includes the following modules: Energy storage preset module: used to introduce low-energy DC to the winding of the reactor to be put into operation to form a preset energy storage state; Instantaneous current-cutting excitation module: It is used to instantaneously cut off the DC current by connecting the arc-extinguishing unit in series based on the preset energy storage state, and to excite high-frequency oscillation by using the ground capacitive component of the winding and the existing surge arrester. Transient response acquisition module: used to acquire the transient current response sequence corresponding to the instantaneous current cut-off moment on the grounding lead of the surge arrester; Attenuation characteristic analysis module: used to determine the initial amplitude, peak attenuation ratio and main oscillation period from the response sequence, and generate transient attenuation characteristics; Insulation anomaly determination module: used to compare transient attenuation characteristics with the reference range to determine the inter-turn insulation status.

Images