An alternating resonance type sinusoidal oscillation wave voltage generating device and method

Abstract

The present invention discloses an alternating resonant sinusoidal oscillation wave voltage generating device and method, including: a charging control switch for controlling the start and stop of charging of an energy storage capacitor unit; a step-up transformer for increasing the voltage; a high-voltage rectifier connected to the step-up transformer for converting alternating current into direct current; an energy storage capacitor unit connected to the high-voltage rectifier for storing the electric energy output by the high-voltage rectifier; a high-voltage reactor connected to the energy storage capacitor unit for generating an oscillation wave voltage; a high-voltage electronic switch connected to the energy storage capacitor unit and the high-voltage reactor, respectively, for controlling the on and off of the energy storage capacitor unit and the high-voltage reactor; a signal acquisition unit connected to the high-voltage reactor for acquiring high-voltage signals and partial discharge signals; a control system for displaying oscillation wave voltage data and controlling the high-voltage electronic switch. The present invention provides a new option for the application of oscillation wave testing technology on high-voltage and ultra-high-voltage power cable lines.

Description

Technical Field

[0001] The invention belongs to the field of insulation diagnosis of electric power equipment, and in particular relates to an alternating resonance type sinusoidal oscillation wave voltage generating device and method. Background Art

[0002] Power cable lines are widely used in power systems due to their excellent electrical and mechanical properties. In order to ensure the reliable operation of power cables and improve power supply reliability, a variety of insulation state tests are required during the installation, handover and routine maintenance of cable lines. The current insulation test methods for power cable lines mainly include withstand voltage test, partial discharge test, and diagnostic tests such as DC resistance, leakage current, and dielectric loss factor that characterize the overall insulation state.

[0003] The DAC is currently widely used in partial discharge diagnostic testing of power cables, and its test results have been recognized by the industry. In recent years, technologies such as withstand voltage test and dielectric loss measurement based on oscillating wave testing have been proposed and applied, and the international standard IEEE Std 400.4 has been formulated. TM -2015. Oscillatory wave testing has developed into a technology that can be applied to comprehensive insulation diagnostic testing of power cable lines.

[0004] However, due to the intrinsic characteristics of the current oscillation wave technology principle, the application of oscillation wave testing technology in high-voltage and ultra-high voltage power cable insulation diagnosis is restricted. Traditional DC oscillation wave testing technology uses a high-voltage DC source as a direct excitation to charge the cable voltage to 2.5 times the maximum cable rated voltage. For transmission cables, due to the large capacitance and high voltage level, a certain charging time is inevitably required, which will lead to the accumulation of space charge in the cable insulation, causing insulation breakdown during cable testing or after commissioning. In 2021, the latest power cable insulation testing guideline CIGRE TB 841 issued by the International Organization of Large Electric Systems (CIGRE) also clearly stated: Considering the problem of space charge accumulation caused by the charging stage, traditional unipolar DC oscillation wave testing is not recommended for high-voltage and ultra-high voltage lines. Summary of the invention

[0005] In order to overcome the problem of space charge accumulation caused by the charging stage, the traditional unipolar DC oscillation wave test is not recommended for high-voltage and ultra-high-voltage lines. The present invention proposes an alternating resonant sinusoidal oscillation wave voltage generating device and method, which uses a new topological structure to generate a sinusoidal oscillation wave voltage on the power cable load, avoiding the problem of insulation space charge accumulation caused by the long-term high-voltage charging process of the cable in the traditional DC oscillation wave testing technology, and providing a new choice for the application of oscillation wave testing technology in high-voltage and ultra-high-voltage power cable lines.

[0006] To achieve the above object, the present invention provides the following solution: an alternating resonant sinusoidal oscillation wave voltage generating device, comprising:

[0007] A charging control switch, used to control the start and stop of charging of the energy storage capacitor unit;

[0008] Step-up transformer, used to increase voltage;

[0009] a high-voltage rectifier, connected to the step-up transformer, for converting alternating current into direct current;

[0010] An energy storage capacitor unit, connected to the high-voltage rectifier, and used to store the electric energy output by the high-voltage rectifier;

[0011] A high-voltage reactor, connected to the energy storage capacitor unit, for generating an oscillating wave voltage;

[0012] A high-voltage electronic switch, connected to the energy storage capacitor unit and the high-voltage reactor, respectively, for controlling the on-off of the energy storage capacitor unit and the high-voltage reactor;

[0013] A signal acquisition unit, connected to the high-voltage reactor, for acquiring high-voltage signals and partial discharge signals;

[0014] Control system for displaying oscillating wave voltage data and controlling high voltage electronic switches.

[0015] Preferably, the alternating resonant sinusoidal oscillation wave voltage generating device further comprises:

[0016] Protection circuit, used to limit the current;

[0017] The tested cable is respectively connected to the energy storage capacitor unit and the high-voltage reactor for discharge.

[0018] Preferably, the protection circuit includes a protection resistor circuit and a buffer protection circuit;

[0019] The protection resistor circuit is located between the high-voltage rectifier and the energy storage capacitor unit and is used to limit the charging current;

[0020] The buffer protection circuit is located between the energy storage capacitor unit and the high-voltage electronic switch, and is used to limit the pulse current size when the high-voltage electronic switch is turned on.

[0021] Preferably, the high-voltage rectifier includes a first rectifier diode, a second rectifier diode, a third rectifier diode, and a fourth rectifier diode;

[0022] The first rectifier diode, the second rectifier diode, the third rectifier diode and the fourth rectifier diode form a full-bridge rectifier circuit.

[0023] Preferably, the high-voltage electronic switch comprises an insulated gate bipolar transistor or a light-triggered thyristor;

[0024] The insulated gate bipolar transistor is used to cut off the primary resonant current, thereby controlling the light-triggered thyristor to be passively turned off.

[0025] The light-triggered thyristor is used to control the on and off of the discharge circuit of the energy storage capacitor unit.

[0026] Preferably, the control system includes a master control lower computer and a client upper computer;

[0027] The master control lower computer is used to output logic control signals, and collect high voltage and partial discharge data and send them to the client upper computer;

[0028] The client host computer is used for joint positioning, discharge amount calibration, pressurization, and processing the data sent by the master control slave computer, and drawing PRPD maps and partial discharge positioning maps based on the processed data.

[0029] A method for generating an alternating resonant sinusoidal oscillation wave voltage,

[0030] Turn on the power supply equipment, close the charging control switch, and charge the energy storage capacitor unit after the AC power is converted into DC power by the step-up transformer and the high-voltage rectifier. After the charging is completed, close the charging control switch;

[0031] Close the high-voltage electronic switch, and the energy storage capacitor unit starts to discharge through the high-voltage reactor and the cable under test. Then open the high-voltage electronic switch, and the high-voltage reactor and the cable under test form a secondary resonant circuit, forming a sinusoidal oscillation wave voltage on the cable under test. The signal acquisition unit collects the high-voltage signal and partial discharge signal, and sends the collected signals to the control system. After data processing by the control system, the oscillation wave voltage and partial discharge data are displayed.

[0032] Preferably, the process of closing the high-voltage electronic switch includes: in the initial state, the insulated gate bipolar transistor remains forward biased and the light-triggered thyristor remains turned off, and when the energy storage capacitor unit reaches a preset voltage value, the light-triggered thyristor is triggered to turn on, and the control system controls the insulated gate bipolar transistor to reverse bias and cut off the current to make the light-triggered thyristor passively turned off, and then the insulated gate bipolar transistor is forward biased again.

[0033] The present invention discloses the following technical effects:

[0034] The present invention provides an alternating resonant sinusoidal oscillation wave voltage generating device and method, which avoids the long-term pressure application problem of traditional DC oscillation waves, eliminates the hidden danger of accumulated space charge in the insulation of power cables during insulation testing, and promotes the application and development of oscillation wave testing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is a structural schematic diagram of an alternating resonant sinusoidal oscillation wave voltage generating device and method according to an embodiment of the present invention;

[0037] Figure 2 A topological schematic diagram of a buffer protection circuit according to an embodiment of the present invention;

[0038] Figure 3 A schematic diagram of a high-voltage electronic switch according to an embodiment of the present invention;

[0039] Figure 4 A schematic diagram of the control logic of a high-voltage electronic switch according to an embodiment of the present invention;

[0040] Figure 5 1 is an equivalent circuit diagram corresponding to different control timings of the alternating resonant sinusoidal oscillation wave voltage generating device of an embodiment of the present invention, (a) is an equivalent circuit diagram corresponding to t<t0, (b) is an equivalent circuit diagram corresponding to when the tested cable is charged to U0, (c) is an equivalent circuit diagram corresponding to when the energy storage capacitor unit and the tested cable are discharged together, (d) is an equivalent circuit diagram corresponding to when t≥t1;

[0041] Figure 6 Schematic diagram of an oscillating wave voltage generated on a cable test sample by an alternating resonant sinusoidal oscillating wave voltage generating device and method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Embodiment 1

[0045] like Figure 1As shown, the present invention provides an alternating resonant sinusoidal oscillation wave voltage generator, and the test device is composed of a charging control switch, a step-up transformer, a high-voltage rectifier, a protective resistor, an energy storage capacitor unit, a buffer protection circuit, a high-voltage electronic switch, a high-voltage reactor, a signal acquisition unit, a control system, and a plurality of functional units of the tested cable. Under the control of the upper computer and the lower computer, the new oscillation wave generator can realize a sinusoidal oscillation wave voltage with adjustable amplitude, effectively stimulate the potential defects of the cable body and its accessories to produce partial discharge, obtain the oscillation wave high voltage and partial discharge signal through the signal acquisition system, and complete various oscillation wave detection items required by the regulations.

[0046] To further optimize the solution, the charging control switch uses a solid-state relay switch with a rated parameter of 220V / 60A to control the charging state. When it is turned on, the 220V AC voltage charges the energy storage capacitor unit. After the charging is completed, the charging control switch is turned off to stop charging the energy storage capacitor unit and isolate the energy storage capacitor unit from the charging power supply.

[0047] Further optimization scheme, step-up transformer, the typical application ratio of this step-up transformer is 220V / 7000V, the power is 1000W, the input power frequency voltage is initially stepped up, and then the energy storage capacitor unit is charged after rectification by the high-voltage rectifier. The step-up transformer ratio and power can be reasonably set according to the load conditions, and its output voltage value must match the rated voltage of the energy storage capacitor unit.

[0048] To further optimize the solution, the high voltage rectifier is a full-bridge rectifier circuit composed of 4 rectifier diodes with a withstand voltage of 30kV and a current carrying capacity of 20A.

[0049] To further optimize the solution, the protection resistor should have a resistance of 1kΩ to limit the charging current and prevent overcurrent from damaging other devices.

[0050] To further optimize the solution, the energy storage capacitor unit consists of 4 high-voltage film capacitors with a rated voltage of 2.5kV and a capacitance of 10mF connected in series. The number of series connections can be reasonably set according to the load conditions, and the rated voltage must match the step-up transformer.

[0051] To further optimize the solution, the buffer protection circuit is as follows Figure 2 As shown, in this circuit, the rated voltage of the inductor is 10kV, and the inductance value is 10mH; the rated voltage of the reverse diode is 10kV, and the current is 150A; the resistance value is 100Ω, and the power is 500W.

[0052] Further optimization scheme, the high-voltage electronic switch is composed of 10 insulated gate bipolar transistors (IGBTs) with anti-parallel diodes with a rated voltage of 3.6 kV and 24 light-triggered thyristors (LTTs) with a rated voltage of 7.5 kV in series. Figure 3 The typical trigger signals of IGBT and LTT are as follows. Figure 4 As shown in the figure, in the initial state, the IGBT maintains forward bias and the LTT remains off. When the energy storage capacitor unit reaches the preset voltage value, the LTT is triggered to turn on. At a certain moment, the IGBT is reverse biased to cut off the current and passively turn off the LTT. Then the IGBT is forward biased again to prevent the IGBT itself from being subjected to high voltage. This high-voltage electronic switch combines the fully controlled characteristics of the IGBT with the high withstand voltage characteristics of the LTT to achieve a fully controlled electronic switch with high withstand voltage.

[0053] To further optimize the solution, the high-voltage reactor has an inductance of 1.5H and a withstand voltage of 180kV. It serves as an intermediate transition element for alternating resonance and also forms a resonant circuit with the cable load to generate an oscillating wave voltage on the load.

[0054] To further optimize the solution, a signal acquisition unit is provided, which transmits the collected high voltage signal and partial discharge signal to a lower computer and uploads them for user analysis.

[0055] To further optimize the solution, the control system consists of a master control lower computer and a client upper computer. The master control lower computer directly outputs the logic control signal required for the system operation, and has the acquisition function to collect high voltage and partial discharge data and upload them to the upper computer system. The upper computer system includes joint positioning, discharge calibration, pressurization, data processing (PRPD spectrum, positioning spectrum, historical data viewing, etc.) functions.

[0056] According to a further optimization scheme, in the oscillation wave generating method of the present invention, the high-voltage reactor and the cable under test are both grounded at one end, so the two can be replaced by inductive test products and capacitive test products respectively, and the oscillation wave testing technology can be carried out for power equipment of different properties.

[0057] Embodiment 2

[0058] The present invention also provides an alternating resonant sinusoidal oscillation wave voltage generation method, comprising the following steps:

[0059] Step 1: Remove the tested cable from the system, remove its cross-connection, and reliably ground its shield and armor;

[0060] Step 2: Use a calibrator to calibrate the partial discharge amount;

[0061] Step 3: Turn on the power supply of the equipment, close the charging control switch, charge the energy storage capacitor unit to the voltage U0, and after charging is completed, turn off the charging control switch;

[0062] Step 4: At this time, its equivalent circuit and switch control timing are as follows Figure 4 , Figure 5 As shown, the load sinusoidal oscillation wave voltage is as follows Figure 6 As shown, the details are as follows:

[0063] S1, the control sequence of high voltage electronic switch is as follows Figure 3 Where t<t0, its equivalent circuit is as follows Figure 5 (a) shown.

[0064] At S2 and t0, LTT is triggered and turned on, and the energy storage capacitor unit will discharge the high-voltage reactor and the cable under test. The cable under test will be charged to U0 in a very small time interval, and its equivalent circuit is as follows: Figure 5 As shown in (b), the energy storage capacitor unit and the tested cable are discharged together through the high-voltage reactor. The equivalent circuit is as follows: Figure 5 As shown in (c), the current flowing through the high-voltage reactor can be expressed as:

[0065]

[0066] L=L1+L2, γ=tan -1 (-α),

[0067]

[0068] Among them, C0 represents the capacitance value of the energy storage capacitor unit; L1 represents the buffer inductance value; L2 represents the inductance value of the high-voltage reactor; and R2 represents the resistance value of the high-voltage reactor.

[0069] The corresponding timing of this stage is t0≤t<t1.

[0070] At S3 and t1, the IGBT is reverse biased, so that the current flowing through the LTT is less than its holding current, and the high-voltage electronic switch will be turned off. The corresponding timing of this stage is t≥t1, and the equivalent circuit is as follows: Figure 5 (d) The circuit state changes from resonance 1 to resonance 2 to generate a sinusoidal oscillation wave voltage on the cable under test, which can be expressed as:

[0071]

[0072] in, t x =t-t1, t1 is the time when the high-voltage electronic switch 7 is turned off, I0 is the current amplitude of the high-voltage reactor when the high-voltage electronic switch 7 is turned off, U x0 is the voltage amplitude of the measured cable when the high-voltage electronic switch 7 is turned off, C x Indicates the equivalent capacitance value of the cable under test.

[0073] Step 5: At the starting point of the sinusoidal oscillation wave, the data acquisition channel is turned on to collect high voltage and partial discharge signals, and transmit them to the host computer after the collection is completed;

[0074] Step 6: After receiving all the data, the host computer program completes data processing and analysis, and draws PRPD maps, partial discharge location maps, etc.

[0075] Step 7: Measurement ends.

[0076] In summary, the significant advantages of the present invention compared with the prior art are summarized as follows:

[0077] 1) The present invention provides an alternating resonant sinusoidal oscillation wave voltage generating device and method, which generates a new type of sinusoidal oscillation wave voltage. The traditional oscillation wave test technology uses a DC charging oscillation wave generation scheme, which is a cosine oscillation wave. The oscillation wave voltage generating device and method involved in the present invention patent designs a new type of oscillation wave test topology.

[0078] 2) The present invention provides an alternating resonant sinusoidal oscillation wave voltage generating device and method, and proposes a low-cost, high-voltage, and high-current fully-controlled high-voltage electronic switch structure, which integrates the fully-controlled characteristics of an insulated gate bipolar transistor and the high-voltage and high-current characteristics of a photo-controlled transistor.

[0079] 3) The present invention provides an alternating resonant sinusoidal oscillation wave voltage generating device and method, which avoids the long-term pressure application problem of traditional DC oscillation waves, eliminates the hidden danger of accumulated space charge in the insulation of power cables during insulation testing, and promotes the application and development of oscillation wave testing technology.

[0080] 4) The present invention provides an alternating resonant sinusoidal oscillation wave voltage generating device and method, the overall system is compact, has the characteristics of modular expansion, and can develop equipment with different output voltage levels for multiple voltage levels.

[0081] 5) The present invention provides an alternating resonant sinusoidal oscillation wave voltage generating device and method, the system control logic is clear and simple, and the operability is strong, which is conducive to the on-site operation of on-site test personnel.

[0082] 6) The present invention provides an alternating resonant sinusoidal oscillation wave voltage generating device and method, which are economical and easy to use. The test device avoids the use of a large number of power electronic devices and their control modules, greatly reducing the production cost of the test device. A small generator pre-charges the test capacitor to meet the test requirements. The test equipment has a series of advantages such as low cost, light weight, miniaturization, modularization, and low demand for on-site power supply capacity.

[0083] 7) The present invention provides an alternating resonant sinusoidal oscillation wave voltage generating device and method, which can be used for insulation diagnosis test of various power equipment. According to the oscillation wave generating method proposed by the present invention, the high-voltage reactor and the capacitor to be tested are both single-ended grounded. Therefore, this test scheme can be used for inductive power equipment, such as transformers, reactors, etc., and can also be used for capacitive power equipment, such as power cables, GIS, power capacitors, etc.

[0084] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for generating an alternating resonant sinusoidal oscillation wave voltage, characterized in that: The method is implemented based on an alternating resonant sinusoidal oscillation wave voltage generator, and includes the following steps: Turn on the power supply equipment, close the charging control switch, and charge the energy storage capacitor unit after the AC power is converted into DC power by the step-up transformer and the high-voltage rectifier. After the charging is completed, close the charging control switch; The high-voltage electronic switch is closed, and the energy storage capacitor unit starts to discharge through the high-voltage reactor and the cable under test. Then the high-voltage electronic switch is opened, and the high-voltage reactor and the cable under test form a secondary resonant circuit, forming a sinusoidal oscillation wave voltage on the cable under test. The signal acquisition unit collects the high-voltage signal and the partial discharge signal, and sends the collected signals to the control system. After data processing by the control system, the oscillation wave voltage and partial discharge data are displayed; The alternating resonant sinusoidal oscillation wave voltage generating device comprises: A charging control switch, used to control the start and stop of charging of the energy storage capacitor unit; Step-up transformer, used to increase voltage; a high-voltage rectifier, connected to the step-up transformer, for converting alternating current into direct current; The high voltage rectifier comprises a first rectifier diode, a second rectifier diode, a third rectifier diode and a fourth rectifier diode; The first rectifier diode, the second rectifier diode, the third rectifier diode and the fourth rectifier diode form a full-bridge rectifier circuit; An energy storage capacitor unit, one end of which is connected to the protection resistor circuit and the buffer protection circuit, and the other end is grounded, and is used to store the electric energy output by the high-voltage rectifier; A high-voltage reactor, one end of which is connected to the high-voltage electronic switch and the cable under test, and the other end is grounded, and is used to generate an oscillating wave voltage; A high-voltage electronic switch, connected to the energy storage capacitor unit and the high-voltage reactor, respectively, for controlling the on-off of the energy storage capacitor unit and the high-voltage reactor; A signal acquisition unit, one end of which is connected to the high-voltage reactor and the cable under test, and the other end is grounded, and is used to collect high-voltage signals and partial discharge signals; A control system, connected to the high-voltage electronic switch and the signal acquisition unit, respectively, for displaying the oscillation wave voltage data and controlling the high-voltage electronic switch; The alternating resonant sinusoidal oscillation wave voltage generating device also includes: Protection circuit, used to limit the current; The tested cable is connected to the energy storage capacitor unit and the high-voltage reactor respectively for discharge; The protection circuit includes a protection resistor circuit and a buffer protection circuit; The protection resistor circuit is located between the high-voltage rectifier and the energy storage capacitor unit and is used to limit the charging current; The buffer protection circuit is located between the energy storage capacitor unit and the high-voltage electronic switch, and is used to limit the pulse current size when the high-voltage electronic switch is turned on.

2. The alternating resonant sinusoidal oscillation wave voltage generating method according to claim 1, characterized in that: The high-voltage electronic switch includes an insulated gate bipolar transistor and a light-triggered thyristor; The insulated gate bipolar transistor is used to cut off the primary resonant current, thereby controlling the passive shutdown of the light-triggered thyristor; The light-triggered thyristor is used to control the on and off of the discharge circuit of the energy storage capacitor unit.

3. The method for generating an alternating resonant sinusoidal oscillation wave voltage according to claim 1, characterized in that: The control system includes a master control lower computer and a client upper computer; The master control lower computer is used to output logic control signals, and collect high voltage and partial discharge data and send them to the client upper computer; The client host computer is used for joint positioning, discharge amount calibration, pressurization, and processing the data sent by the master control slave computer, and drawing PRPD maps and partial discharge positioning maps based on the processed data.

4. The alternating resonant sinusoidal oscillation wave voltage generating method according to claim 1, characterized in that: The process of closing the high-voltage electronic switch includes: in the initial state, the insulated gate bipolar transistor remains forward biased and the light-triggered thyristor remains turned off, when the energy storage capacitor unit reaches a preset voltage value, the light-triggered thyristor is triggered to turn on, and the control system controls the insulated gate bipolar transistor to reverse bias and cut off the current to make the light-triggered thyristor passively turned off, and then the insulated gate bipolar transistor is forward biased again.

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