Cable gis terminal insulation-vibration detection experimental device and application thereof

Abstract

The application discloses a cable GIS terminal insulation-vibration detection experiment device and application thereof, which comprises a power supply system, an experiment loop system, a vibration detection system and a partial discharge detection system.The experiment loop system is used for constructing a real operation scene of the cable GIS terminal and presetting various defects, and comprises a GIS cabin body, a cable GIS terminal and a support for supporting and fixing the GIS cabin body and the cable.The vibration detection system comprises a plurality of vibration sensors arranged on the experiment loop system, a multichannel data collector connected with the vibration sensors and an analysis system connected with the multichannel data collector.The partial discharge detection system is used for collecting partial discharge signals of the experiment loop system during operation, and comprises a signal coupler, a partial discharge analysis device and an independent power supply.The analysis system is in communication connection with the partial discharge analysis device, and is configured to receive synchronous vibration signals and partial discharge signals for joint analysis.The application realizes non-invasive identification of latent insulation hidden dangers and pure mechanical defects.

Description

Technical Field

[0001] This invention relates to the condition monitoring of electrical equipment, and in particular to a test apparatus for testing the insulation and vibration of cable GIS terminals and its application. Background Technology

[0002] Cable GIS (Gas Insulated Metal Enclosed Switchgear) terminals, as key nodes connecting high-voltage cables and GIS switchgear, are widely used in urban high-voltage transmission and distribution networks and large substations due to their compact structure, good sealing, and high safety and reliability. However, in actual operation, cable GIS terminals not only withstand high voltage and high current, but also endure the impact of circuit breaker opening and closing operations, electrothermal aging of their own materials, and micro-settlement of the foundation. These factors seriously threaten the mechanical integrity and insulation performance of the cable terminals. Furthermore, the good sealing of cable GIS terminals makes online operation and maintenance difficult, thus posing a significant hidden danger to the safe and stable operation of the power grid.

[0003] The failure evolution of cable GIS terminals is a deeply coupled process of mechanics and insulation, mainly manifested in two dimensions: First, stress anomalies in insulation components often precede electrical faults. In the early stages of insulation defect formation (such as stress cone installation deviations or stress concentration due to aging), although the threshold for observable partial discharge has not yet been reached, the mechanical modes (natural frequencies, mode shapes, etc.) of the insulation components have already changed due to changes in stress distribution. Traditional partial discharge detection can only capture discharge signals that have already occurred and cannot identify such insulation stress anomalies in the "latent period," thus exhibiting a significant detection lag. Second, purely mechanical defects are highly concealed and extremely harmful. During long-term operation, affected by alternating electrodynamic oscillations, conductor thermal expansion and contraction, and foundation micro-settlement, cable GIS terminals are prone to internal bolt loosening, plastic deformation of metal components, or abrupt changes in overall structure. This severely weakens the structural strength of the equipment and ultimately induces sudden insulation accidents.

[0004] Current research and testing methods for cable GIS terminals have significant limitations: On the one hand, existing testing technologies have not yet established a theory and method for "characterizing insulation stress state using mechanical vibration characteristics," making it impossible to use highly sensitive vibration detection to replace or supplement partial discharge detection in order to discover early insulation hazards that "do not discharge but exhibit abnormal stress." On the other hand, the lack of a systematic simulation platform for various mechanical faults makes it difficult to realistically reproduce working conditions such as bolt loosening and thermo / electrodynamic deformation in a laboratory environment. This results in the inability to effectively extract the characteristic fingerprints of these mechanical faults in vibration signals, making it difficult to perform online diagnosis of the mechanical health status of cable GIS terminals on-site. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problem of the lack of an experimental device in the prior art that can simultaneously simulate the real operating conditions of cable GIS terminals, pre-set various mechanical and insulation defects, and simultaneously collect vibration and partial discharge signals for joint analysis, so as to realize early, non-invasive, and accurate identification and diagnosis of latent insulation hazards and pure mechanical defects. The invention proposes an insulation-vibration detection experimental device for cable GIS terminals and its application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An experimental device for testing the insulation and vibration of a cable GIS terminal includes: a power supply system for providing adjustable high-voltage and high-current power at the power frequency to the experimental circuit; an experimental circuit system for constructing a realistic operating scenario for the cable GIS terminal and pre-setting various defects, comprising a GIS enclosure, a cable GIS terminal installed on the GIS enclosure, and a bracket supporting and fixing the GIS enclosure and the cable; a vibration detection system for acquiring and processing vibration signals of the experimental circuit system during operation, comprising multiple vibration sensors arranged on the experimental circuit system, a multi-channel data acquisition unit connected to the vibration sensors, and an analysis system connected to the multi-channel data acquisition unit; and a partial discharge detection system for acquiring partial discharge signals of the experimental circuit system during operation, comprising a signal coupler, a partial discharge analysis device, and an independent power supply for powering the partial discharge detection system; the analysis system is communicatively connected to the partial discharge analysis device and configured to receive synchronized vibration signals and partial discharge signals for joint analysis.

[0008] In some embodiments, the bracket includes: a top mounting area with a base plate, the GIS cabin being fixed to the base plate via a flange; a middle fixing and adjustment area with a crossbeam having elongated movable holes; and a clamp, fitted onto the cable leading out from the cable GIS terminal and connected to the movable holes on the crossbeam via bolts, allowing for fine-tuning and centering of the cable's horizontal position by adjusting the position of the bolts in the movable holes.

[0009] In some embodiments, the vibration sensor is fixed to the component under test by a mounting structure; for a GIS cabin, flange, or tailpipe, the mounting structure includes an insulating gasket and bolts, and the vibration sensor is rigidly connected to the GIS cabin, flange, or tailpipe by the bolts and insulating gaskets; for a cable, the mounting structure is a hose clamp, and the vibration sensor is pressed onto the surface of the cable by the tightened hose clamp.

[0010] In some embodiments, the power supply system includes: a voltage source employing a series resonant circuit, consisting of a series resonant reactor and a capacitive voltage divider, for providing high-frequency power voltage; and a current source employing a through-core high-current transformer, sleeved on a cable, for providing high current.

[0011] The present invention also provides a method for detecting the insulation and vibration of cable GIS terminals based on any of the above-described devices, comprising the following steps:

[0012] S1. Set up the experimental circuit, install the cable GIS terminal, and deploy the vibration detection system and partial discharge detection system;

[0013] S2. Under normal operating conditions, apply a preset voltage and current, and collect and record the reference vibration signal and reference partial discharge signal;

[0014] S3. Pre-install one or more types of defects in the experimental circuit system;

[0015] S4. Under defective working conditions, apply the same voltage and current as in step S2, and collect and record the current vibration signal and partial discharge signal;

[0016] S5. Compare and analyze the reference signal with the current signal, identify the system modal frequency drift caused by abnormal insulation stress by analyzing the frequency domain characteristics of the vibration signal, and / or identify mechanical structural defects by analyzing the time domain and frequency domain characteristics of the vibration signal; at the same time, analyze the characteristic changes of the partial discharge signal; establish the correlation between vibration characteristics and insulation and mechanical states to diagnose latent insulation hazards and mechanical defects.

[0017] In some embodiments, step S3, the operation of pre-setting defects includes at least one of the following: loosening the bolts on the GIS housing or the cable GIS terminal to below the rated torque; adjusting the spring compression of the internal stress cone of the cable GIS terminal to below the initial value; adjusting the position of the clamp to cause the cable to bend laterally; and causing the cable segment inserted into the GIS housing to bend plastically.

[0018] In some embodiments, in steps S2 and S4, after acquiring the vibration signal, the original vibration signal is preprocessed before analysis. The preprocessing includes: filtering the original vibration signal using a Butterworth bandpass filter, with the lower cutoff frequency of the filter set to 1-10 Hz and the upper cutoff frequency set to 1000-2000 Hz; and using forward-backward filtering technology to eliminate the phase delay introduced during the filtering process.

[0019] The present invention also provides a method for analyzing cable GIS terminal fault diagnosis data based on any one of the methods described above, the method being executed by an analysis system and including the following steps:

[0020] S01. Compare the time-domain waveforms and frequency-domain spectra of vibration signals under normal working conditions and various defective working conditions, and extract vibration characteristic parameters caused by mechanical structure defects or abnormal insulation stress. The characteristic parameters include one or more of the following: resonance frequency shift and higher harmonic amplitude change.

[0021] S02. Analyze the amplitude changes of higher harmonics in the frequency domain. If the amplitude of higher harmonics increases, it is diagnosed as a loose mechanical connection or a structural nonlinear contact defect.

[0022] S03. Compare the timing of abnormal vibration signals and partial discharge signals in the time domain:

[0023] If the vibration signal shows characteristic changes but the partial discharge signal does not increase, the diagnosis is that there is an abnormal insulation stress or a pure mechanical defect in the latent period that has not yet caused partial discharge.

[0024] If abnormal vibration signals occur simultaneously with or after partial discharge signals, the insulation defect is diagnosed as being in the stage accompanied by partial discharge.

[0025] S04. Based on the analysis results of steps S01 to S03, comprehensively determine whether the fault type of the cable GIS terminal is a mechanical defect, a latent insulation defect, or an insulation defect accompanied by discharge.

[0026] The present invention also provides a cable GIS terminal fault diagnosis system, comprising: one or more processors; a memory; wherein the memory stores a computer program; and when the computer program is executed by the one or more processors, it implements the steps of the cable GIS terminal fault diagnosis data analysis method as described above.

[0027] The present invention also provides a cable GIS terminal factory testing station, comprising: the cable GIS terminal insulation-vibration testing device as described in any of the above claims; and the cable GIS terminal fault diagnosis system as described above; wherein the testing station is used for rapid screening and performance evaluation of the mechanical structural integrity and insulation reliability of mass-produced cable GIS terminals.

[0028] The beneficial effects of this invention compared to the prior art include:

[0029] The cable GIS terminal insulation-vibration testing experimental device and method provided by this invention integrates an adjustable power supply system, a test circuit system with pre-set defects, a vibration detection system, and a partial discharge detection system into one unit, and configures an analysis system for signal synchronization and joint analysis, forming a complete detection system. This system can realistically reproduce the operating conditions and various defect states of the cable GIS terminal, allowing vibration signals and partial discharge signals to be acquired synchronously under the same conditions. Through analysis of the synchronized signals, system mode frequency drift caused solely by abnormal insulation stress without accompanying partial discharge can be identified, thereby achieving early detection of latent insulation hazards; simultaneously, changes in vibration signal characteristics caused by mechanical structural defects can also be identified. Therefore, this invention provides an experimental platform for early and comprehensive fault diagnosis of cable GIS terminals, overcoming the lag and limitations of traditional partial discharge detection, and achieving non-invasive identification of latent insulation hazards and purely mechanical defects.

[0030] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the vibration response model under different defect states on which the embodiments of the present invention are based.

[0032] Figure 2 This is a schematic diagram of the overall structure of a cable GIS terminal insulation-vibration testing experimental platform according to an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the overall structure of the experimental circuit system support in one embodiment of the present invention.

[0034] Figure 4a This is a schematic diagram of the structure of the flange connection area at the top of the bracket in one embodiment of the present invention.

[0035] Figure 4b This is a partially enlarged schematic diagram of the flange connection area at the top of the bracket in one embodiment of the present invention.

[0036] Figure 5 This is a schematic diagram of the structure of the clamp fixing area in the middle of the bracket in one embodiment of the present invention.

[0037] Figure 6 This is a connection diagram of a vibration detection system in one embodiment of the present invention.

[0038] Figure 7 This is a flowchart of a defect setting method in one embodiment of the present invention.

[0039] Figure 8 This is a flowchart of the detection workflow in one embodiment of the present invention. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0041] This invention, based on the principles of vibration dynamics, constructs vibration response models for GIS cable terminals under different defect states, as follows: Figure 1 As shown, this model analyzes the abnormal sources of equipment vibration signals into three independent physical paths, corresponding to abnormal insulation internal stress, partial discharge effect, and mechanical structural defects, respectively. Specifically:

[0042] 1. Modal frequency drift caused by abnormal internal stress in insulation (without discharge state)

[0043] Insulation defects manifest as abnormal stress at the insulation interface, but have not yet generated partial discharge. At this stage, the defect does not act as a "vibration source" but rather as a "structural parameter" that alters the overall vibration modes of the system. According to acoustoelastic theory, the equivalent elastic modulus of the material... E The stiffness matrix of the system will change nonlinearly with the stress state, which will in turn affect the system's stiffness matrix. K Things have changed.

[0044] The inherent vibration characteristics of the system are determined by the following equation:

[0045]

[0046] in: M The system quality matrix (remains unchanged); K This is the initial stiffness matrix; Indicates anomaly due to internal stress The resulting stiffness matrix change term (i.e., stiffness perturbation term). Its specific form can be obtained through experimental calibration or finite element analysis based on acoustoelastic theory. For the embodiments of this invention, the core lies in... Changes in the system's inherent frequency will cause The physical phenomenon of drift serves as the theoretical basis for subsequent diagnosis; This refers to the system's natural frequency (modal frequency). This is a modal vibration mode. The process does not involve the propagation of a new signal source within the medium; rather, it involves a change in the vibration characteristics of the system itself. Under the excitation of power frequency electric force, this manifests as a frequency shift in the resonance peaks (natural frequencies) of the vibration response spectrum.

[0047] 2. Propagation of Maxwell stress waves excited by partial discharge (accompanied by discharge state)

[0048] In this path, the insulation defect has progressed to the discharge stage, and the partial discharge point becomes an internal "pulse vibration source." When partial discharge occurs in the air gap or interface inside the insulation, the instantaneous accumulation and release of charge generates a pulsed electric field. This electric field acts on the dielectric, generating transient Maxwell stress. This stress acts as an impact force on the insulator, exciting mechanical waves, which propagate to the outer shell through the epoxy resin sleeve.

[0049] When a partial discharge occurs inside the insulation, the instantaneous charge rearrangement generates a pulsed Maxwellian electrical stress in the dielectric. The stress and electric field strength E The square of (t) is proportional to the square of the number of t, which can be expressed as:

[0050]

[0051] The mechanical wave excited by this pulsed force in the medium can be described by the wave equation:

[0052]

[0053] in For displacement field; c Wave speed; S ( t ) is a source term related to the energy and location of the discharge pulse; Represents the Laplace operator; represents the partial derivative; t represents time. The vibration sensor collects high-frequency vibration pulses excited by Maxwell stress (propagating through the medium) and power frequency vibrations, while the partial discharge sensor collects electrical pulse signals generated by the discharge circuit. The two are causally related in the time domain.

[0054] 3. Abnormal vibration transmission caused by mechanical defects

[0055] In this path, mechanical defects such as loose bolts lead to a decrease in connection stiffness and nonlinear contact, generating an excitation source and altering the transmission characteristics of vibration energy. Mechanical defects reduce the contact stiffness between components. k The vibrational energy can decrease, and even gap collisions may occur. The electrodynamic force generated by the conductor, acting as an excitation source, is transmitted through the loose interface. Due to changes in boundary conditions, the vibrational energy cannot be effectively constrained, or nonlinear harmonics are generated. The system's vibration transfer function... Mutation occurs:

[0056]

[0057] in, The vibration response spectrum of the system; The vibration transfer function representing a system containing mechanical defects; The spectrum represents the excitation source. For loose contact, the contact force... F c It often manifests as nonlinear terms (such as piecewise linear stiffness):

[0058]

[0059] in, Represents the linear stiffness coefficient; Represents the nonlinear stiffness coefficient; x This represents the relative displacement of the contact area. The nonlinear term leads to the generation of high-frequency components. The vibration signal propagates through the object to the sensor, which detects the superposition of the power frequency vibration signal and the high-frequency components.

[0060] For the application research of the above three theories, Theory 2 can be achieved through partial discharge detection, but there are currently no relevant research devices for Theories 1 and 3 specifically for cable GIS terminals. Therefore, this invention provides a cable GIS terminal insulation-vibration detection device, which aims to establish a deep correlation between partial discharge signals and mechanical vibration signals by simulating actual operating conditions throughout the entire cycle. This device can achieve two core functions: first, by monitoring the vibration mode changes caused by abnormal stress in insulation components, it can identify potential insulation defects before partial discharge occurs; second, by detecting and analyzing abnormal vibration signals of mechanical faults, it can accurately identify changes in mechanical structure caused by bolt loosening and thermal / electrical deformation of metal components. This device has significant engineering value for constructing a comprehensive evaluation system for the mechanical and insulation conditions of cable GIS terminals, improving the early fault detection rate and power supply reliability.

[0061] This invention provides a cable GIS terminal insulation-vibration testing experimental device, comprising: a power supply system for providing adjustable power frequency high voltage and high current to the experimental circuit; an experimental circuit system for constructing a real operating scenario of the cable GIS terminal 200 and pre-setting various defects, including a GIS enclosure 201, a cable GIS terminal 200 installed on the GIS enclosure 201, and a bracket 300 supporting and fixing the GIS enclosure 201 and the cable 600; and a vibration detection system for collecting and processing vibration signals of the experimental circuit system during operation, comprising components arranged in the actual circuit. The experimental circuit system includes multiple vibration sensors 401, a multi-channel data acquisition unit 402 connected to the vibration sensors 401, and an analysis system 403 connected to the multi-channel data acquisition unit 402; a partial discharge detection system for acquiring partial discharge signals during the operation of the experimental circuit system, which includes a signal coupler 501, a partial discharge analysis device 502, and an independent power supply 503 for powering the partial discharge detection system; the analysis system 403 is communicatively connected to the partial discharge analysis device 502 and configured to receive synchronized vibration signals and partial discharge signals for joint analysis.

[0062] The bracket 300 includes: a top mounting area with a base plate 301, on which the GIS cabin 201 is fixed via a flange; a middle fixed adjustment area with a crossbeam 302, on which an elongated movable hole 303 is provided; and a clamp 304, which is fitted onto the cable leading out from the cable GIS terminal 200 and connected to the movable hole 303 on the crossbeam 302 via bolts. By adjusting the position of the bolts in the movable hole 303, the horizontal position of the cable can be finely adjusted and aligned.

[0063] Vibration sensor 401 is fixed to the component under test by a mounting structure. For GIS cabin 201, flange or tailpipe, the mounting structure includes insulating gaskets and bolts. Vibration sensor 401 is rigidly connected to GIS cabin 201, flange or tailpipe by bolts and insulating gaskets. For cable, the mounting structure is a hose clamp. Vibration sensor 401 is pressed onto the cable surface by tightening the hose clamp.

[0064] The power supply system includes: a voltage source, which adopts a series resonant circuit and consists of a series resonant reactor 101 and a capacitor voltage divider 102, used to provide high-frequency power voltage; and a current source, which adopts a core-type high-current transformer 103, which is sleeved on the cable 600, used to provide high current.

[0065] This invention also provides a method for detecting the insulation and vibration of cable GIS terminals based on the device described above, comprising the following steps:

[0066] S1. Set up the experimental circuit, install the cable GIS terminal 200, and deploy the vibration detection system and partial discharge detection system;

[0067] S2. Under normal operating conditions, apply a preset voltage and current, and collect and record the reference vibration signal and reference partial discharge signal;

[0068] S3. Pre-set one or more types of defects on the experimental circuit system; the operation of pre-setting defects includes at least one of the following: loosening the bolts on the GIS housing 201 or the cable GIS terminal 200 to below the rated torque; adjusting the spring compression of the stress cone inside the cable GIS terminal 200 to below the initial value; adjusting the position of the clamp 304 to cause the cable to bend laterally; causing the cable segment inserted into the GIS housing 201 to bend plastically.

[0069] S4. Under defective working conditions, apply the same voltage and current as in step S2, and collect and record the current vibration signal and partial discharge signal;

[0070] S5. Compare and analyze the reference signal with the current signal, identify the system modal frequency drift caused by abnormal insulation stress by analyzing the frequency domain characteristics of the vibration signal, and / or identify mechanical structural defects by analyzing the time domain and frequency domain characteristics of the vibration signal; at the same time, analyze the characteristic changes of the partial discharge signal; establish the correlation between vibration characteristics and insulation and mechanical states to diagnose latent insulation hazards and mechanical defects.

[0071] In steps S2 and S4, after acquiring the vibration signal, the original vibration signal is preprocessed before analysis. The preprocessing includes: filtering the original vibration signal using a Butterworth bandpass filter, with the lower cutoff frequency of the filter set to 1-10 Hz and the upper cutoff frequency set to 1000-2000 Hz; and using forward-backward filtering technology to eliminate the phase delay introduced during the filtering process.

[0072] This invention also provides a method for analyzing cable GIS terminal fault diagnosis data based on the method described above. The method is executed by the analysis system 403 and includes the following steps:

[0073] S01. Compare the time-domain waveforms and frequency-domain spectra of vibration signals under normal working conditions and various defective working conditions, and extract the vibration characteristic parameters caused by mechanical structural defects or abnormal insulation stress. The characteristic parameters include one or more of the following: resonant frequency shift and higher harmonic amplitude variation.

[0074] S02. Analyze the amplitude changes of higher harmonics in the frequency domain. If the amplitude of higher harmonics increases, it is diagnosed as a loose mechanical connection or a structural nonlinear contact defect.

[0075] S03. Compare the timing of abnormal vibration signals and partial discharge signals in the time domain:

[0076] If the vibration signal shows characteristic changes but the partial discharge signal does not increase, it is diagnosed as a latent insulation stress abnormality or a purely mechanical defect that has not yet triggered partial discharge; if the vibration signal abnormality occurs simultaneously with or after the partial discharge signal, it is diagnosed as an insulation defect accompanied by partial discharge.

[0077] S04. Based on the analysis results of steps S01 to S03, comprehensively determine whether the fault type of the cable GIS terminal is a mechanical defect, a latent insulation defect, or an insulation defect accompanied by discharge.

[0078] This invention also provides a cable GIS terminal fault diagnosis system, comprising: one or more processors; a memory; a computer program stored in the memory; and when the computer program is executed by one or more processors, it implements the steps of the cable GIS terminal fault diagnosis data analysis method as described above.

[0079] This invention also provides a cable GIS terminal factory testing station, comprising: the cable GIS terminal insulation-vibration testing device as described above; and the cable GIS terminal fault diagnosis system as described above; wherein the testing station is used to quickly screen and evaluate the mechanical structural integrity and insulation reliability of mass-produced cable GIS terminals.

[0080] This invention establishes a true multiphysics experimental platform integrating insulation detection and vibration modal theory, enabling the identification of insulation hazards through vibration characteristics during the latency period before partial discharge occurs, overcoming the lag of traditional detection methods. Simultaneously, by quantitatively simulating defects such as bolt loosening and cable bending under real high-voltage, high-current conditions, vibration characteristics of typical faults are extracted, providing a novel technical approach for non-invasive early diagnosis of cable GIS terminals.

[0081] The following describes specific embodiments of the present invention.

[0082] The cable GIS terminal insulation-vibration detection device provided in this embodiment includes a primary circuit simulating real working conditions for the cable GIS terminal and a secondary circuit for vibration and partial discharge detection. The overall structure is as follows: Figure 2 As shown, it can be configured with various operating conditions, mechanical and insulation defects, to achieve joint detection and research of partial discharge and vibration. The device mainly includes the following systems:

[0083] 1. Power supply system: mainly includes current source and voltage source.

[0084] (1) The voltage source adopts the existing series resonant high-voltage power supply scheme, which mainly consists of a series resonant reactor 101 and a capacitor voltage divider 102. The power supply output impedance is matched with the experimental circuit parameters. The circuit resonance is achieved by manually and continuously adjusting the reactor, thereby generating the required power frequency high voltage in the test circuit. The voltage range is 0~400kV. Series resonant reactor 101: It generates high voltage by resonating with the system's capacitor through inductance. It is placed next to the circuit, and the high voltage end is connected to the capacitor voltage divider 102. Capacitor voltage divider 102: It is located to the right of the series resonant reactor 101 and consists of two capacitor columns connected in parallel. It is mainly used to measure the high voltage value of the system in real time, convert the voltage signal into a low voltage signal proportionally for the measurement system, and resonate with the series resonant reactor 101.

[0085] (2) The current source adopts a manually adjustable core-type high-current transformer 103 with a current range of 0~2kA. By using electromagnetic coupling to generate a large current in the cable position, the temperature field generated by conductor heating and the electrodynamic force generated by the current are simulated, and the influence of thermal expansion and electromagnetic force on the mechanical structure of the cable GIS terminal 200 is realistically reproduced. It is installed in the cable position in the loop, with the cable passing through its center.

[0086] The current source has a maximum output current of twice the rated current of the test sample, and adopts a continuous adjustment method with a maximum rate of change of 10A / s. The control system has built-in hardware-level limit protection. When the current exceeds the maximum value, the power supply is automatically cut off, physically eliminating the generation of short-circuit inrush current and preventing damage to the insulation and mechanical structure of the test sample.

[0087] 2. Experimental Loop System: The experimental loop system is the core physical carrier of the device, used to construct a realistic operating scenario for the cable GIS terminal 200 and pre-set various defects. The experimental loop system includes the water terminal device, high-voltage power cable, the cable GIS terminal 200 under test, high-voltage busbar 207, and supporting structure.

[0088] (1) Water terminal device 206: set at the far end of cable 600, using deionized water to form a uniform electric field to achieve safe transition of high voltage end, ensuring the insulation safety of non-test area during the experiment, and used to connect high voltage bus 207 and cable circuit.

[0089] (2) Insulating cylinder 204: composed of epoxy resin and glass fiber, which serves to isolate the high voltage of the output terminal and the equalizing ring from the metal GIS cabin 201.

[0090] (3) GIS cabin 201: To simulate real GIS equipment, the GIS cabin 201 is made of aluminum alloy and filled with insulating gas (such as sulfur hexafluoride SF6) to connect the cable GIS terminal 200 and together with the insulating cylinder to form a sealed cabin.

[0091] (4) Conductive rod 202: Located in the center of the GIS cabin 201, it is the transmission channel of high voltage current. One end is connected to the external high voltage source through the outgoing end, and the other end is connected downward to the cable GIS terminal 200 terminal 2001.

[0092] (5) Equalizing ring 205: An equalizing ring 205 is installed at the outlet to smooth the electric field, improve the electric field distribution at the outlet end, and prevent tip discharge.

[0093] (6) Cable GIS Terminal 200: Its components include epoxy resin sleeve 2002, stress cone 2003, and spring fastening device, etc. The stress cone 2003 is tightly pressed against the inner cone surface of the sleeve by the mechanical support force of the spring, forming a critical insulation interface. Various defects can be set in the cable GIS terminal 200 to simulate actual defects. The device can adapt to various faults. Table 1 shows the defect setting method of the multi-factor cable test circuit. The defect setting process is as follows: Figure 7 As shown, setting certain faults requires additional tools, such as wrenches. The cable GIS terminal 200 is generally a test product, a prefabricated finished product available on the market, and can be directly installed at the bottom of the GIS compartment 201 via a flange.

[0094] Terminal block 2001: Located at the very top, it electrically connects the lower cable conductor to the upper conductive rod.

[0095] Epoxy resin sleeve 2002: As the main insulating shell, it wraps around the internal components, providing electrical insulation and mechanical support.

[0096] Stress cone 2003: Located inside epoxy resin sleeve 2002, it is fitted over the insulation layer of cable 600 and is used to improve the electric field distribution at the cut point of cable shielding and prevent electric field concentration.

[0097] Flange 2004: Located in the middle of the cable GIS terminal 200, it is used to fix the cable GIS terminal 200 as a whole to the GIS compartment 201, and plays a role in sealing and fixing.

[0098] Spring 2005: Located inside the flange 2004, it provides constant mechanical pressure to ensure that the stress cone 2003 fits tightly against the interface.

[0099] Tail tube 2006: Located at the bottom of the GIS cable terminal 200, it protects the cable lead-out section and serves as a grounding or sealing auxiliary function.

[0100] Table 1. Defect Setting Methods for Multi-Factor Cable Test Circuits

[0101] (7) High-voltage busbar 207: The circuit connection line adopts a low-impedance conductor and is externally fitted with a corrugated aluminum tube to optimize the surface electric field and prevent corona interference. The high-voltage end of the series resonant reactor 101 and the high-voltage end of the capacitor voltage divider 102 are electrically connected to the equalizing ring of the GIS cabin 201 to transmit high-voltage power.

[0102] (8) Bracket 300: Provides mechanical support and fixation for the entire GIS cabin 201 and cable GIS terminal 200 structure. To accurately reflect the mechanical stress conditions at the engineering site, the GIS cabin 201 is installed on a carbon steel galvanized bracket 300 at a certain height. After the cable is led out of the cable GIS terminal 200, a vertical section of more than 1.5 meters is fixed by clamp 304 to avoid excessive lateral mechanical tension caused by external bending of the cable, which could lead to deformation of the internal structure of the terminal. Subsequently, the cable transitions to a horizontal laying state.

[0103] The overall frame structure of the bracket 300 is as follows Figure 3As shown, the support frame 300, serving as the main body of the entire support system, employs four vertical square steel columns as the main load-bearing components. These columns are connected by welding or bolting horizontal and diagonal connecting beams to form a frame structure, ensuring overall rigidity. Four diagonal braces extend outwards from the bottom of the support frame 300 to increase the support area at the bottom, improve the stability of the overall structure, and prevent tipping due to an excessively high center of gravity during high-pressure experiments. Vertically, the support frame 300 is divided into two main functional areas: a top mounting area and a central fixed adjustment area.

[0104] Flange connection area, such as Figure 4a and Figure 4b As shown, this area primarily supports the GIS housing 201 and the epoxy resin sleeve 2002. Base plate 301: Located at the top of the bracket 300, it is a square metal plate with large holes, serving as a transitional connector between the cable GIS terminal 200 and the bracket 300. GIS housing 201: Located above the base plate 301, its bottom is connected to the base plate 301 via a flange structure. Fixed base plate flange 306: Located at the bottom edge of the GIS housing 201, used to securely lock the GIS housing 201 to the base plate 301 with bolts, ensuring the mechanical fixation of the GIS housing 201. Epoxy resin sleeve 2002: Vertically arranged through the central hole of the base plate 301. Its upper part is located inside the GIS housing 201, and its lower part is suspended inside the bracket 300.

[0105] Fixed epoxy sleeve flange 307: This component is located below the base plate 301, closely attached to the bottom of the epoxy resin sleeve 2002. Its function is to clamp the epoxy resin sleeve 2002 and, in conjunction with the fixing structure above, vertically suspend and fix the epoxy resin sleeve 2002, preventing axial displacement or rotation of the epoxy resin sleeve 2002 under stress. The clamp 304 structure is as follows... Figure 5 As shown, it is mainly used for limiting and fixing cables, and has a horizontal position adjustment function. The clamp 304 has a circular metal ring structure, which is composed of two semi-circular rings connected by bolts. Its main function is to fix the cable. The clamp connection hole 305 is located on the lugs on both sides of the clamp 304, and is used to connect to the support beam 302 by bolts. The movable hole 303 for moving the clamp is an elongated hole opened on the beam 302. Its key function is to allow the clamp 304 to move horizontally along the direction of the elongated hole during installation.

[0106] The installation method and connection logic are as follows:

[0107] Overall Positioning: First, place the bracket 300 at the predetermined experimental position, using the bottom diagonal brace to ensure verticality and stability. Top Assembly: Hoist the GIS compartment 201 to the top of the bracket 300, aligning it via the base plate 301 and the fixed base plate 301 flange. Simultaneously, the epoxy resin sleeve 2002 is installed and locked to the base plate 301 via the fixed epoxy sleeve flange 307, allowing it to hang naturally vertically. Lower Alignment and Fixing: Place the clamp 304 at the corresponding height position of the cable GIS terminal 200. Align the clamp connection holes 305 on both sides of the clamp 304 with the corresponding holes on the bracket crossbeam 302. Before tightening the bolts, use the elongated feature of the movable hole 303 to fine-tune the horizontal position of the clamp 304, ensuring that the cable and the epoxy resin sleeve 2002 above are on the same vertical axis, eliminating installation stress. After positioning, insert the bolts and tighten them to complete the fixation.

[0108] 3. Vibration Detection System: This system utilizes a high-sensitivity vibration sensor network to capture minute vibration mode changes caused by mechanical defects or abnormal insulation stress. A connection diagram of the vibration detection system is shown below. Figure 6 As shown.

[0109] (1) Hardware composition: The vibration detection system includes several vibration sensors 401 (e.g., high-sensitivity piezoelectric accelerometer with sensitivity of 50mV / g, frequency band of 0.1-10kHz, and sampling rate of 128 kHz), signal transmission cables, and multi-channel high-speed data acquisition unit.

[0110] Signal transmission cable 404: Each vibration sensor 401 is connected to the multi-channel data acquisition unit 402 via an independent signal transmission cable. As a transmission channel for analog signals, it is responsible for transmitting the weak voltage vibration signals picked up by the sensors to the acquisition front end with low loss and low interference. Figure 6 The solid black line clearly illustrates this one-to-one star connection topology. Considering the interference from the high-voltage electromagnetic environment, both the vibration sensor 401 and the signal transmission cable employ double or multi-layer electromagnetic shielding.

[0111] The multi-channel data acquisition unit 402 is located at the measurement site. Its front-end interface connects to all signal transmission cables, and its back-end connects to the analysis system 403 via a data cable. The multi-channel data acquisition unit 402 features multi-channel synchronous acquisition capabilities, responsible for conditioning (amplifying, filtering) and analog-to-digital conversion (A / D) of analog vibration signals from different measurement points, converting physical vibrations into digital signals to ensure synchronization of data from each measurement point on the time axis. The multi-channel data acquisition unit 402 possesses wide bandwidth (covering low-frequency mechanical vibration to high-frequency structural resonance) and high sampling rate characteristics, ensuring complete recording of transient vibration waveforms.

[0112] The analysis system 403 can be a computer connected to the multi-channel data acquisition unit 402 to receive digitized vibration data. Figure 2 Partial discharge analysis system 403 and Figure 6 The vibration analysis system 403 is on the same computer. The two signals are time-aligned by sharing the computer system clock. Software synchronization technology is used to ensure the correspondence between the electrical signal and the mechanical vibration signal on the microsecond time scale.

[0113] (2) In view of the low-frequency (such as DC bias, baseline drift) and high-frequency (such as random noise, electromagnetic interference) signal characteristics present in the field environment, this embodiment preprocesses the original vibration signal. A Butterworth bandpass filter with the largest flat amplitude characteristic in the passband is selected to preserve the true energy distribution of the signal to the greatest extent. Its amplitude-frequency response model is:

[0114]

[0115] In practice, the filter parameters are set as follows:

[0116] Order (S): Set to 4th order to achieve a balance between filtering effect and computational efficiency;

[0117] Lower cutoff frequency ( ): Select 1~10 Hz to filter out low-frequency drift interference;

[0118] Upper cutoff frequency ( ): Select 1000~2000 Hz, used to filter out high-frequency electromagnetic noise.

[0119] The filter parameters mentioned above are set based on the following: the lower cutoff frequency of 1-10 Hz is used to filter out low-frequency interference from environmental vibration and system sway; the upper cutoff frequency of 1000-2000 Hz aims to retain the main high-frequency structural resonance components excited by mechanical loosening and insulation stress wave propagation, while filtering out higher-frequency electromagnetic noise. Specific values ​​can be fine-tuned according to the modal characteristics of the actual device under test.

[0120] To eliminate time-domain waveform distortion caused by the nonlinear phase delay introduced by the filter, a forward-backward filtering technique is employed. That is, the signal first undergoes forward filtering, the output sequence is inverted in the time domain and then filtered a second time, and finally inverted again to restore the timing sequence. Its frequency-domain equivalent expression is:

[0121]

[0122] in, The frequency response of a single-pass filter. Its complex conjugate. Because It is always a real number, and its phase angle is always zero. This completely eliminates phase delay, ensuring that the reconstructed vibration waveform is not distorted and maximally restores the weak vibration characteristics caused by insulation defects.

[0123] (3) Vibration sensor 401 arrangement and installation: In view of the mechanical structure characteristics and vibration transmission path of the cable GIS terminal 200, the sensor is mainly arranged on the surface of the following main components to achieve comprehensive monitoring of the mechanical status of the equipment as a whole and key parts.

[0124] GIS Cabin 201: Sensors are installed to monitor the vibration modes and internal resonance characteristics of the main body of the equipment.

[0125] Flange 2004 connection: Sensors are installed to monitor the tightness of the connection interface between the cable GIS terminal 200 and the GIS cabin 201 and the mechanical stability of the sealing structure.

[0126] Tailpipe 2006: A sensor is placed here to capture the mechanical coupling characteristics and stress concentration at the connection between the cable outlet and the terminal.

[0127] Support bracket 300: Used to deploy sensors to assess the stability of the supporting foundation;

[0128] Cable 600: Sensors are arranged on the body of cable 600 to monitor the transmission characteristics and attenuation law of vibration waves on the cable line.

[0129] Metal components are rigidly connected using bolts with insulating washers. Pre-drilled mounting holes allow the sensor to be directly screwed in and secured with stainless steel bolts. A high-hardness insulating ceramic washer is added between the sensor and the housing, and fitted onto the bolt. This method, while cutting off ground loop interference, utilizes the bolt preload to provide extremely high contact rigidity, ensuring the flatness of the sensor's amplitude-frequency response within the 0.1–10 kHz frequency band, and avoiding signal attenuation and phase lag caused by adhesive layers.

[0130] For the cable, a high-strength stainless steel worm gear driven hose clamp is selected. The sensor is placed on the cable surface, and the hose clamp is used to surround the cable and the sensor. By tightening the adjusting screw on the hose clamp, a strong radial contraction force is generated, pressing the sensor tightly onto the cable.

[0131] 4. Partial discharge detection system: used to monitor electrical signals generated by insulation defects, which complement and corroborate vibration signals.

[0132] (1) Signal coupling and acquisition: The detection circuit with the signal coupler 501 connected in parallel with the main circuit is used to connect the discharge pulse signal to the wide-bandwidth, high dynamic range partial discharge analysis device 502.

[0133] (2) Interference prevention and transmission: To ensure measurement safety and signal purity under high voltage conditions, optical fiber is used for data transmission between the acquisition unit and the control terminal to achieve complete electrical isolation. The acquisition front end is powered by an independent 503 power supply to cut off conducted interference from the mains power supply.

[0134] Independent power supply 503: Provides a stable power supply for the entire partial discharge test system, ensuring that the accuracy of test data is not affected by power grid fluctuations.

[0135] Partial discharge analysis device 502 (general partial discharge measurement and analysis system): the core detection device, connected between signal coupler 501 and multi-device control unit, amplifies, filters and digitizes the signal transmitted from signal coupler 501, and transmits the processed signal to multi-device control unit.

[0136] Signal Coupler 501: Connects the general partial discharge measurement and analysis system to the high-voltage circuit, and is responsible for picking up high-frequency partial discharge signals and isolating the high voltage.

[0137] Multi-device control unit: Connects and controls the start-up, shutdown, and parameter adjustment of hardware devices such as the general partial discharge measurement and analysis system and signal coupler 501, and has multiple ports to facilitate simultaneous connection to multiple general partial discharge measurement and analysis systems.

[0138] Analysis system 403: Composed of a computer terminal (sharing a computer system with vibration analysis system 403), connected to multiple device control units, used for human-computer interaction, waveform display, data storage and fault diagnosis analysis.

[0139] Based on the operating environment simulation system, current and voltage source system, vibration detection system, and partial discharge detection system, this cable GIS terminal insulation-vibration detection device has the following functions and uses:

[0140] 1. Industrialization Adaptation and Batch Performance Testing

[0141] Designed to meet the industrial needs of cable accessory manufacturing and power grid connection testing, this device boasts high versatility and ease of use. Employing a standardized interface design, it is compatible with various plug-in cable GIS terminals, enabling rapid assembly, disassembly, and testing. It allows for rapid screening and performance evaluation of mass-produced cable GIS terminals under rated voltage, rated current, and overload conditions, verifying their mechanical structural integrity and insulation reliability, thereby improving factory yield and the inherent safety level of grid-connected equipment.

[0142] 2. Study on vibration characteristics of insulation defects under multiple working conditions

[0143] This device can flexibly adjust the voltage level and load current to simulate the operating environment of cable GIS terminals under light load, full load, overload, and different temperature fields. Based on this, by pre-setting insulation defects such as loosening (e.g., 50%-90% of rated torque), deformation, or stress (e.g., initial spring compression of 50%), the excitation effect of different operating conditions on defect states is studied. By comparing the vibration response differences between normal and defect states, the influence of changes in operating conditions on the vibration characteristics of insulation defects is analyzed, providing a theoretical basis for fault diagnosis under online conditions.

[0144] 3. Capturing vibration characteristics of potential insulation defects (non-discharge)

[0145] Addressing the "latent period" in the early stages of insulation defect development before partial discharge occurs, this device focuses on early warning technology based on vibration signals. When there is electric field concentration or aging (modulus change) of insulation material inside the cable GIS terminal but no breakdown or discharge has occurred, vibration mode drift will occur under the action of an alternating electric field. This device uses a high-sensitivity sensor to capture this mechanical vibration anomaly in the non-discharge state, exploring the possibility of using vibration signals to identify potential insulation hazards, and overcoming the technical bottleneck of blind spots in traditional partial discharge detection.

[0146] 4. Study on vibration correlation characteristics of internal insulation discharge

[0147] When insulation defects develop to the stage of partial discharge, this device can simultaneously acquire partial discharge electrical pulse signals and mechanical vibration signals. The partial discharge detection system and the vibration detection system are connected to the same computer (analysis system). The unified system clock of the computer operating system is used to timestamp the two data streams. The software system is set to "synchronous trigger mode". When the acquisition command is issued, the software simultaneously starts recording the partial discharge and vibration data streams.

[0148] This study investigates the superposition effect of shock waves generated by discharge and the inherent mechanical vibration of equipment, analyzing the specific fingerprints of different discharge types (such as surface discharge, air gap discharge, and tip discharge) on the vibration spectrum. By establishing the intrinsic correlation between electrical signals and vibration signals, the problem of poor anti-interference capability of single partial discharge detection is solved, improving the accuracy of locating and characterizing internal insulation discharge faults.

[0149] 5. Study on the characteristics of vibration spectrum of mechanical defects

[0150] This device supports the simulation of various defects commonly found in cable GIS terminals, including bolt loosening, spring relaxation, conductor thermal deformation, and cable bending. By acquiring the vibration time-domain waveforms and frequency-domain spectra under these defect conditions, it analyzes the resonant frequency shifts and harmonic component changes caused by variations in mechanical structure stiffness and damping. The device focuses on studying the typical vibration characteristic parameters of various mechanical faults to achieve accurate diagnosis of mechanical-insulation defects in cable GIS terminals.

[0151] 6. Research on Defect Recovery Technology for Cable GIS Terminals

[0152] To verify the effectiveness of maintenance and repair strategies, this device supports restorative studies of GIS terminals after simulated faults. For example, after torque calibration of loose fasteners and straightening of abnormally bent cables, full-condition testing is conducted again on the device. By comparing vibration and insulation indicators before and after repair, the repair effects of different restoration techniques are quantitatively evaluated, and the correlation between restoration processes (such as the magnitude of fastening torque and the degree of cable bending) and the degree of equipment performance recovery is explored, thereby optimizing maintenance and repair process guidelines in actual operation and maintenance.

[0153] Figure 8 This is a schematic diagram of the detection workflow in this embodiment. The usage process of this experimental device follows a logical closed loop of "loop construction—object installation—sensor deployment—benchmark testing—defect simulation cycle—data analysis". The specific steps are as follows:

[0154] Step 1: Construction and connection of the main experimental circuit

[0155] Basic support positioning: Place the support frame at the predetermined experimental position and unfold the four diagonal braces at the bottom to ensure the stability and verticality of the overall structure.

[0156] High voltage generator connection: Place the series resonant reactor and capacitive voltage divider next to the circuit.

[0157] Connecting the capacitor divider and the high-voltage end of the reactor allows for real-time voltage monitoring and enables a resonant circuit. The outputs of the series resonant reactor and capacitor divider are connected to the equalizing ring and internal conductive rod at the GIS cabin's outgoing line via a high-voltage busbar (with an outer corrugated aluminum tube).

[0158] High-current loading connection: Install a through-hole high-current transformer on the predetermined cable path below the GIS cabin, and pass the cable through the center hole of the through-hole high-current transformer. Connect the water terminal device to the end of the cable loop and connect the deionized water circulation system to ensure insulation safety and heat dissipation in areas not under test.

[0159] Step 2: Installation of GIS terminal for the cable under test

[0160] Top assembly: The GIS cabin is hoisted onto the base plate at the top of the support frame and locked in place by fixing the base plate flange and bolts.

[0161] Terminal Insertion: Vertically insert the GIS cable terminal to be tested (including prefabricated components such as epoxy resin sleeve, stress cone, and cable) from below the bracket. Ensure that the epoxy resin sleeve passes through the center hole of the base plate and enters the GIS compartment, and suspend and fix it using the fixed epoxy resin sleeve flange. Connect the top terminal block to the conductive rod inside the GIS compartment to complete the electrical connection.

[0162] Cable alignment and securing: Use a cable clamp to secure the cable. Align the clamp's connecting hole with the corresponding hole (long, narrow slot) on the support beam.

[0163] Fine-tuning alignment: Before tightening the bolts, use the displacement space of the movable hole to fine-tune the position of the clamp left and right to ensure that the cable and the epoxy resin sleeve above are on the same vertical axis, thus eliminating the internal stress during installation.

[0164] After confirming the location, tighten the clamp bolts and ensure that at least 1.5 meters of vertical section remains after the cable exits the GIS compartment.

[0165] Step 3: Layout and Installation of Vibration Detection System

[0166] Vibration sensor placement: High-sensitivity piezoelectric accelerometers (sensitivity 50mV / g, frequency band 0.1-10kHz) were selected. Using bolts and hose clamps, the sensors were installed at the following key measuring points: GIS cabin: monitoring shell modes and resonance; flange connection: monitoring connection tightness; tailpipe: monitoring mechanical coupling at the cable outlet; support frame: monitoring foundation stability.

[0167] Cable body: Monitors vibration wave transmission attenuation. Each sensor is connected to the multi-channel data acquisition unit via a shielded signal transmission cable.

[0168] Partial discharge detection system setup: Install the signal coupler in the high-voltage circuit.

[0169] The signal is transmitted to a general partial discharge measurement and analysis system via optical fiber and is powered by an independent power supply to isolate interference.

[0170] System Synchronization Connection: The multi-channel data acquisition unit of the vibration detection system and the multi-device control unit of the partial discharge detection system are connected to the same analysis system (computer). Software synchronization technology is used to calibrate the system clock to ensure that the vibration signal and the partial discharge signal are aligned at the microsecond level on the time axis.

[0171] Step 4: Normal Operating Condition Benchmark Test

[0172] Start the water terminal circulation and measurement system.

[0173] Joint loading: Manually adjust the inductance value of the series resonant reactor slowly and continuously to match it with the circuit parameters to achieve series resonance, and apply a 64kV power frequency voltage to simulate the operating voltage of a 110kV system relative to ground.

[0174] Adjust the core-type high-current transformer, gradually increasing the current to stabilize the circuit current at 1000A, simulating the full-load thermal effect and electrodynamic force.

[0175] Data recording: After the system has reached thermal stability, record the vibration waveform and partial discharge signal under normal conditions.

[0176] After the test is completed, the voltage is reduced, the current is reduced, and the power is cut off.

[0177] Step 5: Defect Simulation Cyclic Test

[0178] For the four typical defects, proceed one by one according to the process of "setting defects -> loading tests -> power outage recovery":

[0179] Before any operation involving contact with the experimental circuit or test sample, the following power outage safety procedures must be strictly followed: 1) Disconnect the power system output; 2) Reliably ground the high-voltage output terminal using a dedicated grounding rod; 3) Wait for a period of time to ensure that the capacitor charge is completely released. Subsequent operations can only proceed after confirming that there is no power.

[0180] Test 1: Bolt loosening defect

[0181] Settings: Use a wrench to manually loosen specific bolts connecting the conductive rod (control the number and degree of loosening; you can loosen 1 or 3 bolts, or 50% or 90% of the rated torque).

[0182] Test: Reapply 64kV voltage and 1000A current, and record vibration and partial discharge data.

[0183] Restoration: After the power outage, tighten the bolts to reset the circuit.

[0184] Test 2: Spring relaxation defect

[0185] Settings: Adjust the spring's positioning bolt to change the spring's compression (simulating aging relaxation), setting it to 50% of the initial spring compression (simulating moderate aging relaxation) or 90% (simulating severe aging relaxation).

[0186] Test: Apply 64kV voltage and 1000A current, and record vibration and partial discharge data.

[0187] Recovery: After a power outage, adjust the spring to the standard compression level.

[0188] Test 3: External bending defects in cables

[0189] Setup: Loosen the clamp on the bracket and use the movable hole to move the clamp laterally a certain distance (2cm to simulate moderate bending, 5cm to simulate severe offset) to force the cable to generate lateral bending stress.

[0190] Test: Apply 64kV voltage and 1000A current, and record vibration and partial discharge data.

[0191] Restoration: After a power outage, re-align and tighten the clamps.

[0192] Test 4: Internal bending defects in the cable

[0193] Settings: Unplug the cable GIS terminal again and use external force to cause the cable segment inserted into the cable GIS terminal to undergo plastic bending. The bending height can be set to 5mm (moderate stress concentration, simulating poor installation straightening) and 10mm (severe stress concentration, simulating extreme installation errors).

[0194] Test: After reinstallation, apply 64kV voltage and 1000A current, and record vibration and partial discharge data.

[0195] Restoration: Replace with a normal cable segment or straighten and reinstall.

[0196] Step Six: Data Analysis and Diagnosis

[0197] The collected data is processed using an analysis system.

[0198] Compare vibration signals under normal operating conditions and under various defective operating conditions: observe the distortion of the time-domain waveform;

[0199] Analyze the amplitude variations of higher harmonics (such as 200Hz, 300Hz, etc.) in the frequency domain.

[0200] By combining partial discharge signals, we can analyze whether vibration anomalies occur before partial discharge, thereby verifying the effectiveness of the "vibration method for diagnosing latent insulation hazards" and establishing a fault feature database.

[0201] The cable GIS terminal insulation-vibration detection device designed in this invention can fully simulate the actual operating conditions of cable GIS terminals. Combining vibration detection and partial discharge detection methods, it studies the correlation between the vibration characteristics and insulation defects of cable GIS terminals, as well as the impact of mechanical defects on vibration characteristics. This device aims to provide precise prevention, diagnosis, and maintenance measures for mechanical loosening, structural deformation, and potential insulation hazards within cable GIS terminals. It also establishes a fault database based on vibration-insulation characteristics, which is of great significance for preventative detection of inherent insulation defects, distinguishing between mechanical and insulation defects, achieving non-invasive detection of cable GIS terminals, and improving the safety and stability of power transmission and distribution networks.

[0202] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several equivalent substitutions or obvious modifications can be made without departing from the concept of the present invention, and all such modifications, achieving the same performance or purpose, should be considered within the scope of protection of the present invention.

Claims

1. A test device for insulation-vibration testing of cable GIS terminals, characterized in that, include: The power supply system provides adjustable high-voltage and high-current power at the power frequency to the experimental circuit, thereby realistically replicating the electrodynamic and thermal effects of the cable GIS terminal (200) during operation through a combined loading method. The experimental circuit system is used to construct a realistic operating scenario for the cable GIS terminal (200) and pre-set various defects. It includes a GIS enclosure (201), the cable GIS terminal (200) installed on the GIS enclosure (201), and a bracket (300) supporting and fixing the GIS enclosure (201) and the cable (600). The vibration detection system is used to collect and process vibration signals from the experimental circuit system during operation. It includes multiple vibration sensors (401) arranged on the experimental circuit system and a... (401) A multi-channel data acquisition unit (402) connected to the multi-channel data acquisition unit (402), and an analysis system (403) connected to the multi-channel data acquisition unit (402); a partial discharge detection system for acquiring partial discharge signals of the experimental circuit system during operation, comprising a signal coupler (501), a partial discharge analysis device (502), and an independent power supply (503) for powering the partial discharge detection system; the analysis system (403) is communicatively connected to the partial discharge analysis device (502) and configured to receive synchronized vibration signals and partial discharge signals, so as to analyze the partial discharge signals based on the time-domain synchronized vibration signals and partial discharge signals. The partial discharge signal is subjected to joint analysis; the joint analysis includes: comparing the occurrence sequence of the vibration signal abnormality and the partial discharge signal in the time domain; if the vibration signal shows a characteristic change but the partial discharge signal does not increase, it is diagnosed that there is a latent insulation stress abnormality or a pure mechanical defect that has not yet caused partial discharge; if the vibration signal abnormality and the partial discharge signal occur simultaneously or after each other, it is diagnosed that the insulation defect is in the stage accompanied by partial discharge; wherein the bracket (300) supports the GIS cabin (201) and the cable GIS terminal (200) in a vertical state; the bracket (300) includes: a top mounting area with a base plate. (301) The GIS cabin (201) is fixed to the base plate (301) by a flange; the middle fixed adjustment area is provided with a crossbeam (302), and the crossbeam (302) has a long strip-shaped movable hole (303); the clamp (304) is sleeved on the cable leading out of the cable GIS terminal (200) and is connected to the movable hole (303) on the crossbeam (302) by bolts. By adjusting the position of the bolt in the movable hole (303), the horizontal position of the cable can be finely adjusted and aligned to eliminate installation stress and truly restore the mechanical stress situation on the engineering site; the vibration sensor (401) is used to monitor the system modal frequency drift caused by abnormal insulation stress; the analysis system (403) is configured to identify the system modal frequency drift by analyzing the frequency domain characteristics of the vibration signal.

2. The apparatus according to claim 1, characterized in that, The vibration sensor (401) is fixed to the component under test by a mounting structure. For the GIS cabin (201), flange or tailpipe, the mounting structure includes an insulating gasket and bolts. The vibration sensor (401) is rigidly connected to the GIS cabin (201), flange or tailpipe by the bolts and insulating gaskets. For the cable, the mounting structure is a hose clamp. The vibration sensor (401) is pressed onto the surface of the cable by the tightened hose clamp.

3. The apparatus according to claim 1, characterized in that, The power supply system includes: a voltage source, which adopts a series resonant circuit and is composed of a series resonant reactor (101) and a capacitor voltage divider (102) to provide high-frequency power voltage; and a current source, which adopts a through-core high-current transformer (103) and is mounted on a cable to provide high current.

4. A method for detecting the insulation and vibration of cable GIS terminals based on the device described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Set up the experimental circuit, install the cable GIS terminal (200), and deploy the vibration detection system and partial discharge detection system; S2. Under normal operating conditions, apply a preset voltage and current, and collect and record the reference vibration signal and reference partial discharge signal; S3. Pre-install one or more types of defects in the experimental circuit system; S4. Under defective working conditions, apply the same voltage and current as in step S2, and collect and record the current vibration signal and partial discharge signal; S5. Compare and analyze the reference signal with the current signal, identify the system modal frequency drift caused by abnormal insulation stress by analyzing the frequency domain characteristics of the vibration signal, and / or identify mechanical structural defects by analyzing the time domain and frequency domain characteristics of the vibration signal; at the same time, analyze the characteristic changes of the partial discharge signal; establish the correlation between vibration characteristics and insulation and mechanical states to diagnose latent insulation hazards and mechanical defects.

5. The method according to claim 4, characterized in that, In step S3, the operation of pre-setting defects includes at least one of the following: loosening the bolts on the GIS housing (201) or the cable GIS terminal (200) to below the rated torque; adjusting the spring compression of the stress cone inside the cable GIS terminal (200) to below the initial value; adjusting the position of the clamp (304) to cause the cable to bend laterally; and causing the cable segment inserted into the GIS housing (201) to bend plastically.

6. The method according to claim 4, characterized in that, In steps S2 and S4, after acquiring the vibration signal, the original vibration signal is preprocessed before analysis. The preprocessing includes: filtering the original vibration signal using a Butterworth bandpass filter, with the lower cutoff frequency of the filter set to 1-10 Hz and the upper cutoff frequency set to 1000-2000 Hz; and using forward-backward filtering technology to eliminate the phase delay introduced during the filtering process.

7. A method for analyzing cable GIS terminal fault diagnosis data based on the method described in any one of claims 4 to 6, characterized in that, The method is executed by the analysis system (403) and includes the following steps: S01. Compare the time-domain waveforms and frequency-domain spectra of vibration signals under normal working conditions and various defective working conditions, and extract vibration characteristic parameters caused by mechanical structure defects or abnormal insulation stress. The characteristic parameters include one or more of the following: resonance frequency shift and higher harmonic amplitude change. S02. Analyze the amplitude changes of higher harmonics in the frequency domain. If the amplitude of higher harmonics increases, it is diagnosed as a loose mechanical connection or a structural nonlinear contact defect. S03. Compare the timing of abnormal vibration signals and partial discharge signals in the time domain: If the vibration signal shows characteristic changes but the partial discharge signal does not increase, the diagnosis is that there is an abnormal insulation stress or a pure mechanical defect in the latent period that has not yet caused partial discharge. If abnormal vibration signals occur simultaneously with or after partial discharge signals, the insulation defect is diagnosed as being in the stage accompanied by partial discharge. S04. Based on the analysis results of steps S01 to S03, comprehensively determine whether the fault type of the cable GIS terminal is a mechanical defect, a latent insulation defect, or an insulation defect accompanied by discharge.

8. A cable GIS terminal fault diagnosis system, characterized in that, include: One or more processors; Memory; The memory stores a computer program; when the computer program is executed by the one or more processors, it implements the steps of the cable GIS terminal fault diagnosis data analysis method as described in claim 7.

9. A cable GIS terminal factory testing station, characterized in that, include: The cable GIS terminal insulation-vibration testing apparatus according to any one of claims 1 to 3; The cable GIS terminal fault diagnosis system according to claim 8; wherein, the testing station is used to quickly screen and evaluate the mechanical structural integrity and insulation reliability of mass-produced cable GIS terminals.

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