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Insulator, battery, resistor, inverter, composite insulator technical knowledge
Detailed description of the classification of inspection methods before installation of composite insulators
The performance advantages of composite insulators have been described in detail in the previous article. As a new type of composite power fittings, composite insulators have a comparative advantage in mechanical properties and electrical properties, compared to ceramics. The advantages of insulators and tempered glass insulators, composite insulators are obvious. However, before the installation of the insulator, it is still necessary to carry out sampling inspection and various performance experiments in order to carry out the installation and construction. The specific testing procedures are as follows.
Visual inspection
The appearance of the composite insulator can directly reflect whether the insulator is defective. In the visual inspection, the shed of the composite insulator and the sheath and the adhesive are inspected. The aging condition during the observation period and the rust at the end are as follows. In the case, the insulator is a direct scrap product.
1 The shed is catalyzed by corrosion and ruptured.
2 Electrical or electrical traces appear on the shed and sheath, and all of its length is greater than one tenth of the creepage distance of the insulator or that the etched depth is greater than 30% of the material layer at the designed location.
3 Degumming sealant failure degumming occurs.
4 water hydration decreased.
Mechanical load test
The purpose of this experiment is self-evident. The mechanical properties of composite insulators are their main properties. First, the mechanical load of the insulator is 75% mechanical load. After about 60 seconds, the mechanical load is raised to the damage value and recorded. Normal After three years of use of the load insulator in time, the damage value of this experiment should also be more than 90% of the load involved.
Drop experiment
The drop test for insulators is mainly to test the mechanical strength of the insulator and the age of the components such as the shed. The insulator is at an angle of 45 degrees to the ground, falling at a position of about one meter, free fall three times, and the jacket of the shed should remain intact after three trials. Otherwise, the cracking of the insulator indicates the old fire of the composite insulator and the protection of the umbrella skirt. The set is brittle.
Water seepage test
The main purpose of the water penetration test for insulators is to check the tightness of the insulator. The insulator is soaked in water for 24 hours. After drying, the DC voltage of 40 kV is measured. The leakage current of the composite insulator before and after water immersion should not be increased. More than 5μA.
The above experiments are carried out only by extracting 4-5% of the insulator, but the appearance inspection needs to be performed for each insulator.
1. Preparation of electrolyte
(1) The electrolyte must be prepared from chemically pure sulfuric acid and distilled water. The electrolyte density is generally from 1.25 to 1.29 g/cm3 (at 15 ° C). Industrial sulfuric acid and general water, due to impurities such as iron and copper, cause self-discharge and damage to the plates, and cannot be used in batteries. When the electrolyte is added to the battery, its temperature must be controlled between 21-32 °C.
(2) The relative density of the electrolyte should be determined according to the temperature of the area in use. When the room temperature is 30-40 ° C, the relative density of the electrolyte is 1.270; at 20-30 ° C, the relative density of the electrolyte is 1.280; when the temperature is below 20 ° C, the relative density of the electrolyte is 1.290.
(3) When preparing the electrolyte, the sulfuric acid should be poured into distilled water slowly, and the distilled water should not be poured into human sulfuric acid to prevent the sulfuric acid from splashing and injuring the human body and corroding the equipment.
(4) Simple detection of distilled water, as shown in Figure 1. Use a measuring cup with a capacity of 1000mL (bottom diameter is 100mm), take 500mL of distilled water, adjust the universal meter to R×1KQ, and insert the two sticks into the water wall on the inner wall. If the resistance value is greater than 100kΩ, it cannot be used.
2. Battery charging
(1) After the electrolyte is injected into the battery, the height of the electrolyte should be measured, generally 10-15 mm. The battery is then allowed to stand for 3-6 h until the electrolyte temperature is below 35 °C.
(2) Charging of the battery. As shown in FIG. 3, the battery 1 is inserted into the charger 2 for charging, and the positive electrode and the positive electrode of the battery are connected to the positive electrode, and the negative electrode is connected to the negative electrode. Charging must be done when the relative electrolyte density of the battery is below 1.20 (summer), 1.24 (winter) or when the battery is left for too long. The icy battery should be thawed first, the charging current should be as small as possible, not more than 3-5A, and the charging time is about 3-4h. During the charging process, when the battery cell voltage rises by 2.4V, more bubbles appear in the electrolyte, and the charging current should be halved. After the end of charging, a discharge test is to be carried out to prevent the battery from being damaged by vulcanization only to be surface-charged, which is practically unusable. Therefore, before charging, observe that the battery should be replaced if there is sulfide condensation. The battery electrolyte is strong acid, should avoid touching the skin, eyes or clothes, and pay attention to the following:
1 When inadvertently on the skin, rinse with plenty of water;
2 When you accidentally drink, rinse your stomach with plenty of water or milk, and swallow egg white or vegetable oil;
3 Wear protective goggles when working at close range. If you accidentally get on your eyes, rinse with water and apply eye drops.
4 When charging, flammable gas will be produced. Sparks should be avoided, and the charging or working area should be well ventilated.
(3) The dry charge battery is made of dry-charged electrode plate. After injecting the electrolyte for 1 hour, the vehicle can be started. In the case of urgent need, it can also be used immediately after the electrolyte is poured. In normal use, if there is sufficient time, it can be charged for 3-4h, which is more favorable for the performance of the battery.
(4) After charging, the density of the electrolyte is checked by a densitometer and the electrolyte is adjusted to the relative density. If it is low, the electrolyte having a relative density of 1.40 can be appropriately added, and if it is added, distilled water is added. After adjustment, it should be recharged for 2 hours. If the relative density still does not meet the requirements, it can be adjusted and recharged until it meets the specified value.
When the battery is in use, if the charging voltage is too low or the charging time is insufficient, etc., the following conditions should be replenished in time.
(1) when the relative density of the electrolyte drops below 1.20;
(2) The light is dim than usual and the starter is running weak (non-starting system or mechanical failure);
(3) When the battery discharge exceeds 25% (winter) or 50% (summer).
The supplementary charging current is about 1/10 of the capacity value, and the charging time is 10-11h (the charging current is 9A when the capacity is 9OAh).
After the battery is charged, the cell voltage of the cell is 2.5-2.7V, and the voltage remains unchanged within 2-3h.
4. Battery inspection
(1) Inspection of the electrolyte surface of the battery. As shown in Figure 4, when the battery electrolyte is below the lower limit, distilled water or electrolyte is added, but it cannot exceed the highest position.
(2) Inspection of the voltage of the battery. As shown in FIG. 5, the battery 2 is used to measure the voltage of the battery 2. When the battery current is 110A, the minimum voltage should be no lower than 9.6V; if the battery voltage is lower than this value within the measurement duration of 5-1Os. Indicates that the battery is leaking or defective.
(3) Check the relative density of the battery electrolyte. As shown in Fig. 6, the relative density of the battery electrolyte is measured by the relative density meter 1, the relative density should be 1.28 at 20 °C normal charging, and must be charged when the relative density is less than 1.13; if the relative density is less than 1.11 , you must replace the electrolyte or increase the relative density of the electrolyte before charging; if in one or two adjacent cells, the relative density of the electrolyte is significantly reduced (such as the relative density of five cells is 1.16, a cell In the case of 1.08), the battery is short-circuited and should be replaced.
The relative density of the battery electrolyte will vary with temperature. For example, the relative density of the battery at 1.20 ° C is 1.28; the relative density of 1.273 is acceptable at 30 ° C; 1.287 is acceptable at 10 ° C. Observe the relative density timing and the eye must be level with the level of the relative densitometer.
Several resistor detection methods
When the asynchronous motor is started, the slip ratio S is close to 1, when the slip is large, there is no power and the power factor is low.
When the asynchronous motor is rated for operation, when the slip ratio S is close to 0, the slip is small, no power is small, and the power factor is high.
When the inverter starts the motor, the output frequency is low, so that the asynchronous motor slip can be guaranteed within the rated slip range, so the motor is always working in the high power factor state.
Therefore, it can be said that the inverter changes the output frequency and controls the slip of the asynchronous motor within the rated slip range, thus ensuring high operating power factor of the motor.
If the ratio of the output frequency f of the inverter to the output voltage U is constant, the motor flux Φ is a constant value, that is, the excitation current (NIo) remains unchanged.
Excitation current (NIo) decreases only when the motor flux Φ decreases
Therefore, the main way to increase the power factor of the inverter is to control the slip rate of the asynchronous motor.
When the asynchronous motor is in the big horse-drawn car, the frequency converter can adjust the frequency-to-pressure ratio, reduce the magnetic flux Φ of the motor, reduce the reactive current, and improve the power factor.
Therefore, simply speaking, the conclusion of "low frequency, low output voltage, small reactive current" is wrong, lowering the frequency, lowering the voltage, but the frequency-to-pressure ratio is constant, which is to ensure that the motor core flux Φ is constant, equal to the motor design magnetic Φ, that is, the magnetic flux Φ at the power frequency
When the big horse car is used, the motor flux Φ can be reduced, that is, the value of the frequency-to-pressure ratio is changed, that is, at the same frequency, the voltage is appropriately reduced, and the field current is lowered.
Reduce the frequency, reduce the voltage, do not reduce the magnetic flux Φ, the excitation current does not change, the reactive power remains unchanged
Change the frequency-to-pressure ratio, reduce the motor flux Φ, reduce the excitation current, reduce the reactive power, and improve the power factor
Electrical Encyclopedia: Factors Affecting the Mechanical Strength of Composite Insulators
The mechanical strength of organic composite insulators has unique advantages in the insulator family, but its mechanical strength is still affected by three aspects.
1 Power fitting strength
The mechanical strength of the electric power fittings matched with the organic composite insulator affects the mechanical strength of the organic composite insulator. When the insulator string is installed, the mechanical strength of the hardware for the organic composite insulator also has relatively high requirements. This is the reason why the right amount of water in a wooden barrel is determined by the shortest piece of wood.
2 composite insulator core strength
Mandrel strength is a decisive factor in the tensile strength of an insulator. Insulators need to have strong tensile strength against wire tension in power transmission and distribution lines. This is the key to the mechanical strength of the composite composite bar.
3 Connection structure of power fittings and composite insulators
The insulator string needs to be used in conjunction with the fitting during the installation process. The mechanical strength of the link fitting determines the service life of the insulator string. This is done in the installation of organic composite insulators. The inner-type, outer-bend or inner-outer knot combination is the main form of composite insulator installation. In addition, the crimp joint structure is also in line with the common form of insulator installation.
The most common form of organic composite insulators in China is the internal composite insulator, which is used frequently in the hanging circuit, and has been widely used in domestic transmission and distribution lines, and its good mechanical properties. And the electrical performance can guarantee the performance of most domestic transmission lines for the performance of insulators. The convenience of power supply for decades is self-evident. This is also the choice of domestic composite transmission and substation. main reason.
Electrical Encyclopedia: Special Functions and Performance of Composite Insulators in Power Transmission and Distribution Lines
It is well known that ceramic insulators are relatively weak in terms of mechanical properties and electrical properties compared to tempered glass insulators. In UHV lines that are being constructed in China, ceramic insulators are no longer sufficient. But in the same way, tempered glass insulators also have some disadvantages in use, in which case composite insulators are born. At the same time, we can understand the technical characteristics and application requirements of high-voltage composite insulators.
1, comprehensive performance
Insulators of polymer organic materials have greater advantages in mechanical strength and insulating ability than ceramic insulators and glass insulators. Their greatest advantage is reflected in the anti-soil flashing ability. Compared with the traditional hungry insulators, the composite insulator improves the formulation of the shed and increases the mechanical strength and hydrolysis resistance of the inner core of the insulator. In terms of mechanical properties, the performance of the composite insulator is greatly improved. . The improved material of the composite insulator adhesive and the closed structure of the two ends of the metal fittings and the structure of the metal fittings have greatly improved the performance of the composite insulators!
2 Features
Compared with traditional insulators, composite insulators have obvious characteristics, small size and light weight. They are relatively intuitive features of composite insulators, and their strength is high. They are not easily broken during transportation and during installation. More significant features. The production process is simple, the waste generation is less, the production energy consumption is low, and the production advantages are also a great help for the promotion of the composite insulator.
3 composite insulator with equalizing ring
The main function of the voltage equalizing ring on the composite insulator is to achieve the purpose of effectively controlling the electric field strength inside the insulator. Effective control of the electric field strength inside the insulator can avoid internal partial discharge. At the same time, the grading ring can also control the electric field strength outside the insulator and the technical connection part, and achieve the function of driving the power frequency arc, which plays a protective role for the composite type and the transmission and distribution line. The composite insulator after the grading ring is installed can maximize the anti-smudge ability.
In different power transmission and distribution lines, the size of the voltage equalizing ring installed in the composite insulator is different. This is determined according to the needs of the power line. There is no uniform standard in the standard, and the line designer needs the characteristics according to the line. Choose your own.
