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The principle and application of frequency conversion series resonance
2025-07-30The structure of variable frequency series resonance mainly consists of a variable frequency control power supply, excitation transformer, capacitor, and capacitor voltage divider. The application range of variable frequency series resonance: Suitable for various large power transformers, power cables, steam turbines, hydro generators, and other capacitive equipment. The AC withstand voltage test must be strictly conducted regularly according to the test regulations. Under power frequency conditions, due to the large capacitance of the test object or high requirements for the test voltage, there are also high requirements for the power capacity of the test device. Traditional power frequency withstand voltage devices often have large individual volumes, heavy weights, are not easy to transport on site, and are not easy to combine arbitrarily, resulting in poor flexibility. The principle of frequency conversion series resonance: When the circuit frequency f=1/2 π√ LC, the circuit reso
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Correct use of frequency conversion series resonance withstand voltage test device and power supply
2025-07-30The power input of the variable frequency series resonant withstand voltage test device is divided into two parts. From the production design requirements of the variable frequency series resonant withstand voltage test device, the "working power supply", as the name suggests, is mainly used to provide power for the normal operation of the instrument. It can also be referred to as variable frequency series resonant withstand voltage. The frequency modulation power box of the testing device provides neural control for the working power supply, and the "power supply" provides a guarantee for the resonant output high voltage of the upper and lower stages. The quality of power supply is directly related to the output voltage and power when testing cables or tested products.1. The working power supply of the instrument generally needs to be connected to 220V; the recommended power supply for the equipment is 380V;2. The live wire of the instrument's working power supply should be discon
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Condition analysis before series resonance withstand voltage test
2025-07-29In electrical testing, parallel resonance and series resonance are both structural branches of the series resonance testing device, with a slight difference in their names. Below is a basic introduction to series resonance. What is series resonance? Due to the fact that most power preventive tests are conducted on large capacity and high voltage electrical equipment, it is recommended to use power frequency withstand voltage for insulation performance testing, which eliminates the requirement for using DC high-voltage generators for insulation performance testing of electrical equipment. Although both belong to destructive tests, after long-term research, the use of power frequency withstand voltage has better stability and safety compared to DC withstand voltage. Due to the large capacity and high voltage of electrical equipment, power frequency withstand voltage equipment such as oil immersed test transformers often cannot meet the testing requirements. In China, in order to achiev
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A comprehensive introduction to the components of series resonance
2025-07-29Series resonance is a circuit property and also a testing device for series resonance. Series resonance is a very practical and important voltage withstand test device in power systems. Its components are: variable frequency power supply, excitation transformer, high-voltage reactor, and capacitive voltage divider. So what are the functions of these components? 1、 Variable frequency power supplyThe function of a variable frequency power supply is to convert a 220V/380V, 50Hz power supply into a frequency adjustable and voltage continuously adjustable power supply. The variable frequency power supply also has functions such as operation, protection, control, and monitoring of the power system.2、 Excitation transformerThe function of the excitation transformer is to boost the voltage output by the variable frequency power supply, and the excitation transformer isolates both high and low voltage. 3、 High voltage reactorThe function of a high-voltage reactor is to cause series resonance
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What are the main methods for voltage withstand testing of power cables?
2025-07-28Cable withstand voltage test is a detection method for discovering cable faults. During the testing process, it is susceptible to various factors that may cause malfunctions, short circuits, and other issues. The following introduces the main methods of cable withstand voltage testing.1、 Ultra low frequency withstand voltage testThe ultra-low frequency (0.1Hz) withstand voltage test method first appeared in 1980, mainly used as a non-destructive testing method to observe whether there are insulation defects in cables during operation. This method has been validated through extensive laboratory and field experiments, and the low-frequency withstand voltage test has shown good application results in the withstand voltage test of low-voltage power cables. This method utilizes the principle of converting 50Hz AC power into DC voltage through rectification and filtering, then converting the DC voltage into 1kHz AC voltage through an inverter circuit, and finally completing the amplitude mod
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What is series resonance? What are the hazards of series resonance in circuit systems?
2025-07-28Series resonant devices are widely used in power systems. What is series resonance? What are the hazards of series resonance in circuit systems?What is series resonance?In a series circuit composed of resistors, inductors, and capacitors, when the capacitive reactance XC is equal to the inductive reactance XL, i.e. XC=XL, the phase of the voltage U and current I in the circuit are the same, and the circuit is purely resistive. This phenomenon is called series resonance. When a circuit has series resonance, the impedance of the circuit is Z=√ R2+(XC-XL)/2=R. The total impedance in the circuit is minimized, and the current will reach its maximum value. When resonance occurs, inductance equals capacitance, so the effective value of the voltage across the inductance and capacitance is equal, i.e. UL=UC. And due to their opposite phases, these two voltages cancel each other out.What are the hazards of series resonance in circuit systems?In the formula, ω 0LU/R is referred to as the quality
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Advantages of Variable Frequency Series Resonant Boosting Device
2025-07-25The role of series resonance is very extensive.Only when you are a customer using a cable specific variable frequency series resonant boost device, will you have the opportunity to become an experiencer of this boost device. With the emergence of cable specific frequency conversion series resonant boosting devices, convenience has been demonstrated in so many waves of development.Why do we talk about the convenience of the cable specific variable frequency series resonant boosting device when it comes to its function? So it is precisely because of the emergence of cable specific variable frequency series resonant boosting devices that so many people have focused on the birth of this boosting device, which has provided a great development platform for its appearance. However, it is precisely from the use of cable specific variable frequency series resonant boosting devices that some of its advantages and functional improvements can be known.For example, the testing workload for the cabl
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Selection of Series Resonance Test Equipment
2025-07-25When choosing equipment, it is important to master the correct method before completing the selection process. In the process of selecting a series resonance test device, how should the relevant work be done well. Only when you have mastered all the methods well can you ensure the final result.In the process of selecting equipment, it is best to have a clear understanding of the specific functions. Different devices still have differences in their functions. When we can have a good understanding of the corresponding functions and make the corresponding choices in this way, the most important thing is to make the necessary adjustments.Function is one aspect, and we also need to pay attention to the brand of the series resonance test device. There is a great relationship between brand and quality. Choosing a better brand can often ensure quality and also guarantee after-sales service. Anyone in the process of choosing should always do a good job from a comprehensive perspective in order
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Application of series resonance test device in high-voltage withstand voltage test
2025-07-24The application of series resonance test device in high-voltage withstand voltage test greatly reduces the difficulty of high-voltage withstand voltage test. Traditional high-voltage withstand voltage testing has disadvantages such as large testing equipment, difficult mobility, and slow testing efficiency. The series resonant high-voltage withstand voltage test device overcomes the shortcomings of traditional high-voltage withstand voltage tests and has made significant improvements on this basis, making high-voltage withstand voltage tests more efficient.For the AC withstand voltage test of electrical equipment such as 220kV high-voltage bushings, main transformers, and isolating switches, the series resonant withstand voltage test device has a wide range of applications and is also a very practical and easy-to-use withstand voltage test equipment for various high-voltage testing departments and power decoration testing engineering units.The series resonant withstand voltage test dev
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What are the basic methods and measures for series resonant harmonic control?
2025-07-24At present, there are three basic methods and measures for harmonic control. In the treatment of series resonance, it can be divided into two parts: centralized management of substations and on-site decentralized processing of nonlinear electrical equipment. According to the principle of whoever pollutes should treat it, it should be dispersed on-site at non-linear electrical equipment. However, for a large number of scattered civilian equipment, only centralized management can be carried out.1、 Increase system capacity. To reduce system impedance, series resonance is to popularize the capacity of power supply and the level of power supply voltage, thereby improving the harmonic anti-interference ability of nonlinear electrical equipment. This method is relatively expensive and usually requires coordination with the power grid development plan.2、 Isolation of harmonics. The harmonics generated by nonlinear electrical equipment not only directly affect the current level of the power gri
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Scope of application of the complete set of frequency conversion series resonance test equipment
2025-07-23Variable frequency series resonance is the use of the principle of series resonance to adjust the output frequency of the variable frequency controller, so that the circuit inductance L and the test sample C resonate in series. The high-voltage reactor L is an important component of the resonant circuit. When the power frequency is equal to 1/(2 π√ LCX), it resonates in series with the test sample CX, and the series resonance voltage is the voltage applied to the test sample.The variable frequency series resonant withstand voltage device mainly consists of a variable frequency controller, excitation transformer, high-voltage reactor, high-voltage voltage divider, etc.Variable frequency series resonance is suitable for various large power transformers, power cables, steam turbines, hydro generators, and other capacitive equipment. The AC withstand voltage test must be strictly conducted regularly according to the test regulations. Under power frequency conditions, due to the large capac
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How to choose the best series resonant device?
2025-07-23In their work, power workers often need to conduct resonance tests on high-voltage power cables to identify the resonance point of the cables. Therefore, they need to use series resonance test devices. Many people do not know how to choose because there are many resonance test devices on the market, and often businesses only consider their own interests and ignore the actual needs of customers. They recommend expensive and fully functional equipment, which is completely unnecessary. This article will briefly introduce how to choose a suitable series resonance test device for oneself.1、 According to the withstand voltage level of their own cables, the series resonance test device is mainly used for high-voltage cable withstand voltage tests of 10-35KV. The higher the voltage level, the larger the volume and weight of the series resonance equipment, so the cost also increases. Power workers can choose suitable resonant devices based on their own cable grade, without selecting too high a
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What are the possible reasons for insulation failure of power equipment in withstand voltage testing?
2025-07-22Q: What are the possible reasons for the insulation failure of power equipment in the withstand voltage test?Answer: During the withstand voltage test, the possible reasons for the insulation failure of power equipment include:(1) Insulation degradation. For example, moisture in transformer oil, moisture in solid insulation, insulation aging, etc. can all lead to a decrease in insulation performance and may fail the withstand voltage test.(2) The testing method and voltage measurement method are incorrect. For example, during transformer testing, if the untested winding does not have a short circuit to ground, the untested winding may discharge to ground and be misjudged as unqualified. For example, when testing large capacity test objects, the voltage is still measured on the low voltage side. Due to the rising effect of capacitance, the actual voltage applied to the tested object exceeds the test voltage, causing the tested object to break down and be misjudged as unqualified.(3) Wit
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Abnormal phenomena and preliminary analysis in AC withstand voltage test
2025-07-221、 The situation reflected by regulatory agenciesWhen the power is turned on, the electromagnetic switch is turned on, and the voltage regulator is turned on, the voltage regulator will make a heavy sound. This may be due to the 220V voltage regulator being connected to the 380V power supply incorrectly. If the current reading is abnormal at this time, it may be due to the voltage regulator not being at zero position, or a short circuit or similar short circuit on the output side. Forgetting to remove the grounding rod is common.2、 The situation reflected by the voltmeter(1) The voltmeter indicates. After the power is turned on, the voltmeter immediately gives an indication that the voltage regulator is not at zero position. If the voltmeter has a large indication and a sound, it may immediately smell it.(2) The voltmeter shows no indication. After power on, the voltage regulator meter shows no indication. This may be caused by poor contact of the carbon brush in the autotransformer, a
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What are the advantages and characteristics of variable frequency series resonance?
2025-07-21What are the advantages and characteristics of variable frequency series resonance?1. The placement of variable frequency power supply is vertical and horizontal, which is particularly suitable for on-site operation and observation.2. Equipped with special shock-absorbing rubber support feet and protective aluminum boxes both inside and outside, it can effectively reduce bumps and vibrations during transportation and impact during lifting. Ensuring the long-term stability and reliability of the variable frequency power supply;3. Parameter display: The touch or external mouse LCD interface display system can display resonance voltage (i.e. the target voltage set before the test), test frequency, measurement frequency, low voltage voltage, low voltage current, withstand voltage time, overvoltage protection, overcurrent protection, flashover protection, voltage rise and stage timing, etc. The working mode switch capacitor, inductance, frequency exchange calculation, parameter query, etc.
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What are the functions of variable frequency series resonant devices
2025-07-21What are the functions of variable frequency series resonant devices1) Internally controlled by an embedded touch screen, the operation function has been optimized and the operation is simple2) Automatic frequency scanning to find resonance points The frequency range is 20-300Hz, and the sweep range can be manually set. The sweep time is 3 minutes (full frequency sweep) Frequency resolution 0.1Hz3) Automatic testing, users can set the testing program, and the system automatically completes the testing process according to the set program4) During automatic testing, the resonance state of the system is automatically tracked. When the resonance state changes beyond the set area, the system automatically tracks the resonance point Ensure that the system operates at output throughout the entire process, and plot the frequency voltage curve during frequency modulation.5) Automatically track the voltage during withstand voltage, and adjust the voltage to the target voltage when the voltage f
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What should be noted when using power frequency withstand voltage testing equipment
2025-07-18Series resonance testing equipment is widely used in cable withstand voltage testing, which can meet the testing requirements of cable handover testing and preventive testing, and has a small testing capacity. So what should be noted when using a series resonance test device for AC withstand voltage testing of high-voltage cross-linked cables?1. We can only conduct analysis tests after the cables to be tested have been installed in place and meet the development requirements for operation.2. The core wire of the test phase should be connected to a high voltage source, and the shielding layer of the test phase, non test phase core wire, and non test phase shielding layer should all be grounded. After confirming that the information is correct, the test can begin.3. The overvoltage protector of the cable shielding layer is short circuited, and the corresponding end cable metal shielding layer or metal sleeve is temporarily grounded.4. If the cable head is directly connected to the GIS, t
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How to determine whether the series resonant test sample has been broken down?
2025-07-18Whether the test sample has been punctured can be judged according to the following situations:1. According to the analysis of the meter connected during the experiment, in general, if the ammeter suddenly rises, it indicates that the test object has broken down (overcurrent relay action, automatic tripping). But when the ratio of the capacitance impedance XC of the test sample to the leakage impedance XL of the test transformer is not greater than 2, although the test sample breaks down, the ammeter reading will not change significantly, and sometimes the ammeter reading may even decrease.If this situation occurs, the voltage on the high voltage side should be monitored based on the measuring voltage device on the high voltage side. If the test sample breaks down, its voltmeter will only suddenly drop, and the voltmeter measured on the low voltage side will also drop, but sometimes it is not very obvious.2. Analyze based on the condition of the experimental control circuit. If the set
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Application of Frequency Conversion Series Resonance
2025-07-17In recent years, people's living standards have been increasing, and the demand for electricity resources has also been growing. In order to meet the power supply needs, high-voltage cross-linked cables have been widely used in the power system. To ensure the safe and stable operation of high-voltage cables, on-site completion handover tests must be conducted after cable laying is completed. Below, Dingsheng Power analyzes the application of variable frequency series resonance technology in cable high-voltage testing.Cable on-site handover test1. Test items and equipment wiringWhen measuring the insulation resistance of the outer sheath of the cable core, the measuring personnel should select a suitable range megohmmeter to measure the insulation resistance of the cable according to the actual situation, in order to determine whether the insulation resistance value of the cable meets the relevant requirements.When conducting the AC withstand voltage test of cable core wire to sheat
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Operating conditions and environmental requirements for frequency conversion series resonant withstand voltage device
2025-07-17Operating conditions and environmental requirements for frequency conversion series resonant withstand voltage device1、 Usage requirements: For indoor use.2、 Altitude: The operating area has an altitude not exceeding 1000m.3、 Beyond an altitude of 1000m, it shall be negotiated between the user and the manufacturer.1. Temperature range for series resonance test environment: The operating temperature range is -25 ℃~+45 ℃,2. Series resonance uses humidity: relative humidity does not exceed 80%.3. Seismic requirements: The resonant device should withstand an earthquake intensity of seven degrees without damage, that is, it should not be damaged under the action of horizontal acceleration of 0.15 minus vertical acceleration of 0.1g.Series resonance test, the variable frequency series resonance device mainly consists of a variable frequency controller, excitation transformer, high-voltage reactor, high-voltage voltage divider, etc. Variable frequency controllers are divided into two categori
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