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Types and diagnostic methods of internal faults in power transformers
2024-09-11Internal faults in power transformers can be classified into two types:Overheating and discharge faults. According to temperature, overheating faults can be divided into low-temperature overheating, medium temperature overheating, and high-temperature overheating. Discharge faults can be classified into high-energy discharge, low-energy discharge, and partial discharge based on their energy density. Three types.As for mechanical failures and internal water ingress and moisture, they will eventually develop into electrical failures.Overheating faults are caused by accelerated insulation degradation due to thermal stress.If thermal stress only causes the decomposition of insulating oil outside the heat source, the special gases produced are mainly methane and ethylene, which generally account for more than 80% of the total hydrocarbons. As the fault point increases, the proportion of ethylene will increase, and severe overheating will produce trace amounts of acetylene.When overheating i
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What is weak current engineering?
2024-09-11Power applications can be divided into strong power and weak power based on the strength of power transmission. The electricity consumption of a building complex generally refers to AC 220V 50Hz and above strong electricity. Mainly providing electricity for people, converting electricity into other energy sources such as air conditioning electricity, lighting electricity, power electricity, etc.There are mainly two types of weak electricity in smart buildings. One is low-voltage electricity such as national security voltage levels and control voltages, AC/DC, AC below 36V, and DC below 24V, such as 24V DC control power supply or emergency lighting backup power supply. Another type is information sources that contain voice, image, data, and other information, such as telephone, television, computer information, etc.People are accustomed to calling it weak current technology. It can be seen that the basic meaning of weak current technology in intelligent buildings is still the original w
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What is the MVA unit of electrical energy?
2024-09-10MVA in electricity is a unit of transformer capacity, power unit, or power unit generated by a generator.VA=WMVA=MW1MW=1000KW=1000000WKilowatt, an early unit of electrical energy, has a tendency to extend to the entire field of physics as a power unit. In electricity, kilowatt hour is exactly the same as degree, but with a different name.1 kW=1000 W=1000 J/s1 kW=1000 Newton meters per second (N m/s)1 kW=0.239 kcal/s1 kW=1.36 horsepowerWatt is a unit of power in the International System of Units. Watt is defined as 1 joule per second (1J/s), which is the rate at which energy (in joules) is converted, used, or dissipated per second. In the electrical unit system, it is volts multiplied by amperes multiplied by power factor (1V · A, abbreviated as 1 volt ampere).Unit conversion: Watt is named after British scientist James Watt, who made significant contributions to the development of steam engines. The name of this unit was first adopted at the 2nd meeting of the British Association for t
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Drying treatment method for transformers
2024-09-10The significance of transformer dryingThe purpose is to remove moisture from the insulation material of the transformer, increase its insulation resistance, and improve its flashover voltage. Transformers with voltages higher than 3kV must be dried.The transformer body is mainly assembled from iron core, coil, and insulation material. After assembly, before adding transformer oil, a drying process must be carried out to remove moisture and gas from the insulation material, so as to control the moisture content in the product quality within the limit, to ensure that the transformer has sufficient insulation strength and operation life. For high-voltage transformers, it is required that the moisture content of the insulation material be within 0.5%.Insulation drying standards and drying treatment for transformers(1) Drying standard:① Transformer insulation oil does not contain moisture. The breakdown voltage of the oil product shall not be lower than 75% of the factory data;② The insulat
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Three detection methods for capacitors
2024-09-09A capacitor is a device that contains an electric charge and is one of the electronic components used in a large number of electronic devices. Widely used in circuits such as DC, AC, coupling, bypass, filtering, tuning circuits, energy conversion, and control. The detection of capacitors is mainly divided into three categories: detection of fixed capacitors, detection of electrolytic capacitors, and detection of variable capacitors.1、 Fixed capacitance detection1. Detect small capacitors below 10pF. Because the fixed capacitance below 10pF is too small, measuring with a multimeter can only qualitatively check for leakage, internal short circuit, or breakdown. When measuring, a multimeter with R × 10k range can be used, and two probes can be connected to either pin of the capacitor. The resistance value should be infinite. If the measured resistance value (pointer swinging to the right) is zero, it indicates that the capacitor is damaged by leakage or internal breakdown.2. Check whether
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Under what circumstances would a gas chromatograph be used?
2024-09-09The oil chromatography analyzer under UHV power can help many power workers conduct various power tests more conveniently.In daily work, the sound of a gas chromatograph is often heard. When will gas chromatography be used, as this instrument has a wide range of applications in many industries? Gas chromatograph is a computer-controlled multi-purpose high-performance series chromatograph. Mainly used for quality inspection, scientific research, pollution inspection, and production control of industrial production intermediates and industrial products.Before using the gas chromatograph, open all glass ports of the titration cup and clean the titration cup, drying tube, and sealing plug with water. After cleaning, dry in an oven at approximately 80 ° C and then cool in a natural environment. Please note that the materials of the cathode chamber and measuring electrode should not be cleaned with water. It can be cleaned promptly with organic solvents such as acetone and methanol, and then
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The purpose, method, and precautions of transformer DC resistance testing
2024-09-06The DC resistance tester under UHV power can help many power workers conduct various power tests more conveniently.The purpose of testing the DC resistance of a transformer is to:1. Check the welding quality of the winding joints and whether there is a turn to turn short circuit in the winding;2. Whether the contact of each position of the on load tap changer is good, and whether the actual position of the tap changer is consistent with the indicated position;3. Whether the outgoing line is disconnected;4. For three-phase power transformers, calculate the unbalance rate of their three-phase DC resistance based on the test results to determine whether it meets the design or relevant standardsMeasurement of transformer DC resistance using a DC resistance testerMeasuring DC resistance is an important item in transformer testing. By measuring the DC resistance, the conductive circuit of the equipment can be checked for defects such as poor contact, poor welding, coil faults, and wiring err
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Product Description and Application Scope of DC High Voltage Generator
2024-09-06The DC high-voltage generator under the UHV power company can help many power workers conduct various power tests more conveniently.1、 Precautions for using discharge rods as supporting products for DC high-voltage generatorsWhen discharging a large capacitor sample, after the test is completed, disconnect the test power and wait for a period of time to allow the charge on the sample to self discharge to the ground through the voltage doubler and grounding terminal. The sample itself. It can be observed that the voltage reading on the voltmeter on the control box is gradually decreasing. When the voltmeter drops to a lower voltage, usually around 5Kv~15Kv, a discharge rod can be gradually moved to the vicinity of the tested product and discharged freely through air. At this time, a hissing sound can be heard. If there is no sound, the tip of the discharge rod can be used to contact the sample, and finally the sample can be directly discharged to the ground.2. The accumulated charge of
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How long does it take to retest the transformer
2024-09-05What tests should be conducted before putting a transformer into use if it has been out of service for one month or has been idle or out of service for more than six months?1. After the transformer is shut down for one month, the insulation resistance should be measured before resuming power transmission. Only after passing the test can it be put into operation.2. Transformers that have been idle or suspended for more than 6 months should undergo insulation resistance and insulation oil withstand voltage tests before being put into operation.3. The special service life of drainage and irrigation transformers in dry and cold areas can be appropriately extended, but not exceeding 8 months.What regulations must be followed for the operation and shutdown of transformers?(1) Newly commissioned transformers must undergo 5 impulse tests at rated voltage and 3 tests after maintenance.(2) When the transformer is put into operation, first place it in the cooler. The cooler runs for a period of t
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Operation and use of pointer type insulation resistance tester
2024-09-05The insulation resistance tester under UHV power can help many power workers conduct various power tests more conveniently.Insulation diagnosis is an important means of detecting insulation defects or faults in electrical equipment. The pointer type insulation resistance tester is a specialized instrument for measuring insulation resistance. At present, electrical equipment is developing towards high capacity, high voltage, diversified structure, and sealing.Operation and wiring method of pointer type insulation resistance tester:1) Before the experiment, the power supply and all external connections of the test equipment should be disconnected, and the test substance should be short circuited to ground and discharged for 1 minute. If the capacitance is large, it should be discharged for at least 2 minutes to avoid electric shock affecting the measurement results.2) Check if the instrument pointer is at infinity or adjust the mechanical zero screw.Attention: When adjusting the mechanic
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Preparation before battery internal resistance test
2024-09-04The battery charging and discharging tester under the UHV power company can help many power workers conduct various power tests more conveniently.There are many types of battery internal resistance testing equipment, and their main difference lies in the type of battery being tested. The capacity and terminal voltage of the tested battery are different. Here we are talking about the preparation before battery testing for power, communication, and UPS power battery testing1. Fully charge the tester and check if it is working properly2. Prepare some necessary maintenance tools and protective tools, such as insulation and fixing protective tools3. Check the historical records of the test battery. Many units may not have this record. It is currently unclear when the battery was installed and put into use, but you must do some homework to figure it out.4. Prepare some adhesive labels and conditionally write the model, internal resistance value, test date, and label on them.5. Bring a thermo
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Analysis method and results of factors affecting DC leakage
2024-09-041. The influence of high-voltage connecting lines on ground leakage currentDue to the fact that the wires connected to the test product are usually exposed to the air (without shielding), the pressurized end of the test product is exposed to the outside, so the surrounding air may be released, and the leakage current of the product to the ground, especially in high-altitude and thin air areas, is more likely to occur, which can affect the accuracy of the measurement of ground leakage current. Measures such as increasing the diameter of the wire, reducing the tip or increasing corona shielding, shortening the wire, and increasing the distance from the ground can reduce the impact on the measurement results.2. The influence of air humidity on surface leakage currentWhen the air humidity is high, the surface leakage current is much greater than the volume leakage current. The dirt on the surface of the tested product is prone to moisture absorption, increasing surface leakage current. The
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Application scope of air drying generator
2024-09-03Dry air generator is a very important gas manufacturing equipment in industrial production. It uses non thermal regeneration to adsorb compressed air and absorb moisture from the gas, thereby obtaining a lower dew point temperature, dry and clean gas purification equipment. Equipment suitable for users who obtain dew points below -23 ℃. It uses activated alumina with a pore size similar to that of water molecules as the adsorbent, and adopts the internationally advanced pressure swing adsorption principle. When adsorbed at room temperature, the partial pressure of water molecules in the air is greater than that in the adsorbent.It enters the adsorbent, condenses into water droplets on the surface of the adsorbent, releases condensation heat, and is stored in the upper part of the adsorption tower. During regeneration, about 15% of the dry air enters the regeneration cylinder through a needle valve at normal pressure, allowing water molecules in the adsorbent to escape. The heat stored
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Reasons and solutions for lubricating oil entering emulsification
2024-09-03The presence of moisture and vigorous stirring are the main reasons for oil emulsification. Oil and water are incompatible, as oil has a lower density than water. When oil and water are mixed, under the action of temperature, vibration, pressure, etc., they wrap around each other to form countless tiny separation surfaces, which appear white under the refraction of light. When observed with the naked eye, it appears milky white.Lubricating oil must have three necessary conditions to form lotion:1. There must be two immiscible (or partially miscible) liquids;2. There should be emulsifiers (surfactants that can reduce interfacial tension) in the two mixed liquids;3. Lotion can only be formed with energy, such as strong mixing, circulation and flow. Moisture, vigorous stirring, and emulsifiers can all cause lubricant emulsification.Emulsified white lubricating oil can be demulsified and dehydrated through a vacuum oil filter. The water separation device of the oil filtration equipment use
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What are the advantages of directly buried cable laying
2024-09-02The cable fault tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.The advantages of directly buried cable laying can be clearly summarized as follows:Simple and convenient construction:Direct burial cable laying is the process of burying cables directly underground, parallel to the ground, without the need for additional support structures, reducing construction complexity.The construction period is short because the steps of directly burying cables are relatively simple and can be completed quickly.Low investment cost:Compared to other cable laying methods such as ducts, cable trenches, tunnels, etc., direct buried cable laying does not require additional structures or facilities, resulting in lower investment costs.The direct burial method avoids a large amount of excavation and construction costs, reducing initial investment.Good heat dissipation conditions:The cable is directly buried underground, and the soil has a certain insulation
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Test method for series resonance withstand voltage
2024-09-02The series resonance under Wuhan UHV can help many power workers conduct various power tests more conveniently.The series resonance withstand voltage test method is an important method for testing the insulation performance of equipment in power systems. The following is a detailed explanation of the method, including its principles, steps, and precautions:principleThe series resonant withstand voltage test method is based on the characteristics of the series resonant circuit and the capacitance properties of the insulation material of high-voltage equipment. By connecting the tested device in series with the power supply, a resonant circuit is formed, and the power supply frequency is adjusted to achieve a resonant state of the circuit. In the resonant state, the current in the circuit reaches its maximum value, and the capacitive properties of the insulation material of the tested device can cause a lag phase of the current, causing the current and voltage in the resonant circuit to
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What are the advantages and disadvantages of the series resonance withstand voltage test method
2024-08-29The series resonance under Wuhan UHV can help many power workers conduct various power tests more conveniently.The series resonance withstand voltage test method is widely used in power systems, and its advantages and disadvantages are as follows:advantage:Reduce test time: During the series resonance withstand voltage test, the power supply only needs to be input to two identical insulators at the same time to obtain two identical withstand voltage results, greatly reducing the test time.Reduce testing costs: As the power supply only needs to be input to two identical insulators at the same time, the number of equipment used and power requirements are reduced, thus reducing testing costs.High experimental accuracy: Due to the use of the same conditions for withstand voltage measurement, the obtained data has high accuracy.Light weight and small volume of the system: The series resonance experimental device has a relatively small weight and volume, generally 1/5 to 1/10 of a regular ex
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What are the limitations of the series resonance withstand voltage test method
2024-08-29The series resonance under Wuhan UHV can help many power workers conduct various power tests more conveniently.Although the series resonance withstand voltage test method has many advantages in power systems, it also has some limitations. The following is a detailed explanation of the limitations of this method:Safety risks of high voltage operation:The series resonance withstand voltage test process involves high voltage, which poses strict safety requirements for the testing personnel. Testers must possess strict safety knowledge and operational skills to prevent dangerous situations such as electric shock and arc during the testing process.Due to the high test voltage, higher requirements have been put forward for the insulation performance and protective measures of the equipment to prevent equipment damage and personnel injury.Difficulty in designing and debugging resonant circuits:The design of resonant circuit that matches the characteristics of the tested electrical equipment i
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What is the difference between high impedance fault and low impedance fault
2024-08-28The cable fault tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.High impedance faults and low impedance faults are two common abnormal situations in cable faults, and they have significant differences in definition, causes, effects, detection methods, and handling methods. The following is a detailed analysis:definitionHigh resistance fault: refers to a fault situation where the resistance in the cable is abnormally high. Usually, a high resistance fault occurs when the insulation layer of a cable is damaged, resulting in a decrease in insulation resistance, but it is not close to zero and is between several hundred kiloohms and several megaohms.Low resistance fault: refers to a fault situation where the resistance in the cable is abnormally low. The resistance value of the cable will become abnormally low in low resistance faults, approximately below 1 ohm.reasonHigh resistance fault: may be caused by cable aging, insulation damage, loo
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How to determine whether it is a high resistance fault or a low resistance fault
2024-08-28The cable fault tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.To determine whether a cable fault is a high resistance fault or a low resistance fault, the following steps and indicators can be used:1、 Measure insulation resistanceUsing an insulation resistance tester: Firstly, use an insulation resistance tester (such as a megohmmeter) to measure the insulation resistance value of the cable.2、 Judging based on insulation resistance valueHigh resistance fault:When the insulation resistance of one or more cores of a cable is higher than the normal value, but does not reach infinity (usually the insulation resistance is greater than 100k Ω, which is lower than the normal insulation resistance of the cable), it can be judged as a high resistance fault.High impedance faults may be caused by cable aging, insulation damage, poor joint contact, and other reasons.Low resistance fault:When one or more cores of the cable are grounded, or the insu
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