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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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Under what circumstances does surface tension disappear
2024-08-27The surface tension tester under the UHV power company can help many power workers conduct various power tests more conveniently.The surface tension will disappear or significantly decrease in the following situations:Reaching critical temperature:When the temperature reaches the critical temperature (Tc) of the liquid, the boundary between the liquid and gas phases disappears, and the liquid no longer has a clear surface, so the surface tension will decrease to zero. This process corresponds to the critical point in the phase diagram where the liquid phase directly transitions to the gas phase.Extreme high pressure:Under extremely high pressure, the interactions between liquid molecules may change, resulting in a decrease in surface tension. However, this effect is usually not significant under low pressure and requires a high pressure environment to cause significant changes.Add surfactants:Surfactants are a class of compounds with amphiphilic properties (both hydrophilic and oleophi
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What are the applications of surface tension in physics
2024-08-27The surface tension tester under the UHV power company can help many power workers conduct various power tests more conveniently.Surface tension has a wide range of applications in physics, and the following are some of the main application areas and examples:Research on Liquid Surface Morphology:The automatic shrinking trend and shape change of liquid surfaces, such as the spherical shape of water droplets, is due to the effect of surface tension. This phenomenon is commonly used in physics to study the surface morphology of liquids and their relationship with surface tension.Capillary phenomenon:The capillary phenomenon is the result of surface tension acting on small pipe diameters. For example, the height at which water rises or falls in a thin tube is related to the diameter of the tube and the surface tension of the liquid. This phenomenon has applications in biology, chemistry, and engineering, such as water transport from plant stems and ink transfer at pen tips.Infiltration an
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What are cable fault prevention measures
2024-08-26The cable fault tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.Cable fault prevention measures refer to a series of measures taken to reduce the probability of cable faults occurring and minimize the losses caused by faults. These measures are mainly based on the common causes and types of cable failures, aiming to improve the reliability and safety of cable systems. The following is a detailed analysis of cable fault prevention measures:1、 Analysis of Cable Failure CausesThere are various reasons for cable failures, including:Mechanical damage: such as damage during installation, direct damage from external forces, vibration or impact loads from moving vehicles, etc.Insulation moisture: such as unsealed joint box or terminal box structure, poor cable manufacturing, etc.Insulation aging and deterioration: Due to the free air gap inside the insulation medium under the action of an electric field, the insulation decreases, or overheating
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What is cable fault detection method
2024-08-26The cable fault tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.The cable fault detection methods mainly include the following, which can be flexibly selected and used according to the type of fault and actual situation:1. Non destructive testing methodNon destructive testing method uses physical means to detect cables without damaging the cables themselves. Common non-destructive testing methods include:Infrared thermography: Determine the presence of a fault by detecting changes in heat on the surface of the faulty cable. Infrared thermal imaging cameras can quickly and accurately locate potential hotspots in cables.Ultrasonic testing: By sending ultrasonic signals and receiving reflected signals, the fault points inside the cable are detected. The ultrasonic detector can monitor the sound wave reflection signal of the cable in real time and determine the location and type of the fault through analysis.Electromagnetic wave detection: u
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What are the conditions for series resonance
2024-08-23The series resonance under Wuhan UHV can help many power workers conduct various power tests more conveniently.The conditions for series resonance can be summarized as follows:Component connection sequence: Inductive, capacitive, and resistive components in a circuit must be connected in a certain order. Usually, inductors are located before capacitors, while capacitors are located before resistors. This arrangement of connection sequence plays a crucial role in the resonance characteristics of the circuit.Component value selection:At the resonant frequency, the impedance of inductive and capacitive components is equal, that is, the inductive impedance (X_L) is equal to the capacitive impedance (X_C). Expressed mathematically as: wL=1/wC, where w is the angular frequency at the resonant frequency, L is the inductance value, and C is the capacitance value.The impedance of inductors and capacitors matches the impedance of resistive elements.External excitation frequency: The frequency of
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What is energy exchange between inductors and capacitors
2024-08-23The series resonance under Wuhan UHV can help many power workers conduct various power tests more conveniently.The energy exchange between inductance and capacitance refers to the mutual conversion of electrical energy and magnetic or electric field energy between inductance and capacitance components and the power source in an AC circuit. This energy exchange is a common phenomenon in electronic circuits, especially playing an important role in circuits such as resonant circuits, filtering circuits, and oscillators.The following is a detailed explanation of energy exchange between inductors and capacitors:Energy exchange of inductors:Inductance is a component that can store electrical energy and release it over time. When the inductor is powered on, due to the slow rate of current change in the circuit, a magnetic field will be generated inside the inductor, which will continuously change with the change of current.If the power is turned off, the magnetic field will generate a reverse
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Causes of cable faults
2024-08-22The cable fault tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.The causes of cable faults can be summarized into multiple aspects, and the following are some of the main reasons and their detailed explanations:Mechanical damage:Damage during installation: Accidentally damaging the cable during installation, pulling the cable due to excessive mechanical traction, or excessively bending and damaging the cable.Direct external damage: Construction activities on or near the cable path, such as excavation, pile driving, etc., may cause direct external damage to the cable.Vibration or impact load of driving vehicles: may cause lead (aluminum) sheath cracking of underground cables.Damage caused by natural phenomena, such as tension caused by land subsidence, may break intermediate joints or conductors.Insulation moisture:The structure of the junction box or terminal box is not sealed or poorly installed, resulting in water ingress.Poor cable ma
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Cable failure caused by insulation moisture
2024-08-22The cable fault tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.Cable faults caused by insulation moisture are one of the common types of faults in cable operation, accounting for about 13% of the total number of cable faults. The following is a detailed summary of the main causes and related information of cable failures caused by insulation moisture:Poor or failed sealing:One of the main causes of insulation moisture is inadequate or ineffective sealing at the middle or terminal of the cable. Poor sealing causes moisture to enter the interior of the cable, reducing insulation resistance and increasing leakage current.Poor manufacturing processes or material defects in cable manufacturing, such as holes or cracks in the outer protective layer of the cable, can also increase the risk of moisture intrusion.Cable operating environment:During the laying and operation of cables, they may cross roads, bridges, culverts, etc. Due to weather or
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