Power Capacitor-About the Application of Power Capacitor

Category：News Release time：Mar 10,2021

When the power capacitor is applied, there should be appropriate protection measures to ensure the use of the power capacitor.

At runtime, the current and voltage are different for different conditions.

If the voltage of the capacitor rises frequently and for a long time, the current should not exceed 1.3 times the rated current to avoid accidents.

In normal times, the operation of the capacitor should be checked frequently. If any of the following conditions are found, the operation should be stopped.

Inside the capacitor:

1. It feels stuffy, not ventilated, and the temperature is too high.

2. The casing is found to be cracked, disordered and discharging.

3. Hearing abnormal sounds.

Outside the capacitor:

1. Find deformation of appearance, such as swelling.

2. See oil leakage on the ground or outside the capacitor.

3. The casing is not properly connected to the ground.

Relevant information

2021 03-10

Wiring Method of Power Capacitor-Capacitor Bank Reactor and Filter

This type of wiring can utilize a current protection device connected to its neutral point. When a capacitor fault breaks down and is cut off, an unbalanced current will be generated, causing the protection device to operate and disconnect the power supply. This protection method is simple and effective, and is not affected by system voltage imbalance or ground faults.

Large capacity capacitor banks, such as those with small single capacity and a large number of parallel connections per phase, can choose double star wiring. If the voltage level is high and there are many series segments per phase, in order to simplify the structural layout, it is advisable to use single star wiring.

The primary side of the capacitor is connected with a series reactor and a parallel discharge coil. The function of the discharge coil is to quickly and reliably release the charge on the capacitor after disconnecting the power supply. Due to the frequent operation of switching on and off the capacitor bank, the interval between them may be very short. After the capacitor bank is disconnected from the power supply, there is a large amount of charge stored between its electrodes, which cannot disappear quickly on its own. In a short period of time, there is a high DC voltage between its electrodes. When the power is switched on again, it causes voltage superposition, which will produce high overvoltage and endanger the safe operation of the capacitor and the system. Therefore, it is necessary to install a discharge coil and connect it in parallel with a capacitor to form an inductive capacitive parallel resonant circuit, so that electrical energy can be consumed in resonance. The discharge coil should be able to reduce the capacitor terminal voltage to 50V within 5 seconds of disconnecting the power supply.

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2021 03-10

Electric Capacitor-Development Trend of Domestic High Voltage Electrical Apparatus

1. Combination and complete sets of electrical appliances have emerged to meet the needs of small size, small footprint, high performance, and high reliability. In addition to switchgear, FC cabinets, and multi-layer cabinets, various combinations have emerged, including load switch fuse combination capacitors, high-voltage contactor fuse combination appliances (used for FC cabinets), load switches, drop fuses, and lightning arresters, as well as lightning arresters, isolation switches, voltage and current inductors, and other combinations. These have developed into advanced types of combination equipment, such as gas charging cabinets (C-GIS), fully enclosed combination appliances (GIS), and full substation combinations such as prefabricated substations (including transformers and box transformers for high and low voltage electrical appliances).

2. Large capacity and high parameters: Due to the rapid growth of modern electricity consumption, the increase in industrial and agricultural electricity consumption, and the formation of high-voltage and large capacity power grids, it is required that the capacity and various parameters of high-voltage electrical appliances be rapidly increased. At present, the rated current of the main power transmission and distribution equipment has been increased from 1000A to 2500A to 4000A, and the short-circuit current has been increased from 16~20kA to 31.5~50kA, or even higher. The number of single pole breaks in 550kV circuit breakers has been reduced from 4 to 2, and the development of single pole breaks is being accelerated. If the main power transmission and distribution voltage in our country cannot be rapidly increased, then the trend of high capacity and high parameter requirements for high-voltage electrical appliances in our power grid will not cool down (the emergence of higher transmission voltage can unlock some ring networks of subordinate distribution voltage to reduce the short-circuit current of these power grids).

3. Mechatronics (intelligentization): With the development of computer and sensor technology and the improvement of power grid automation, the demand for intelligent functions of high-voltage electrical appliances has become more urgent. The combination of strong electrical equipment and advanced weak electrical technology can significantly expand the functions of high-voltage electrical appliances, providing better conditions for power grid automation, remote control, and online detection. Traditional electromagnetic relay protection devices, electrical instruments, and control devices with large volume, heavy weight, and single function will be replaced by multifunctional computers and sensors.

4. With the widespread use of excellent insulation and arc extinguishing media such as SF6 and vacuum in high-voltage capacitor products, as well as production processes based on advanced high-tech (such as CAM), the maintenance cycle of products can be extended to 10 years, or even lifelong maintenance free maintenance. Moreover, with the development of electronic and information technology, online detection technology is becoming more practical, and the user departments have the conditions to achieve the transformation from fault diagnosis to condition based maintenance. The operation and maintenance will also implement the principles of "few people, high efficiency, safety, and reliability". The next decade will be a period of significant development for maintenance free products, which will gradually occupy a certain position in the power system.

5. With the development of high voltage and large capacity power grids, excessive closing overvoltage and large short-circuit current in the system are detrimental to the safety and reliability of the power system. In today's rapidly developing electronic control technology, it is possible to achieve phase selection and no-load line closing of circuit breakers. The selection of phase closing no-load lines can minimize the closing overvoltage, which is very important for reducing the insulation level and improving the technical and economic level of ultra-high voltage power grids. Breaking large short-circuit currents (especially those above 50kA and larger asymmetric currents) imposes a heavy burden on high-voltage circuit breakers. If a favorable phase (i.e. shorter arc time and small half wave) can be automatically selected for breaking, the breaking capacity of high-voltage circuit breakers can be improved, and the safety and reliability of the power system can be enhanced. Therefore, utilizing advanced electronic control technology to achieve phase selection, opening and closing of high-voltage circuit breakers is one of the development directions of high-voltage circuit breakers.

6. Oil free switchgear has been used as an insulation and arc extinguishing medium in the high-voltage electrical industry for over a hundred years, and is still widely used in transformers and switches today. However, oil medium is a flammable and explosive substance, and it is inconvenient to operate and maintain. With the rise of SF6 and vacuum switches in switchgear, the use of oil switches is decreasing (oil switches are no longer used at 363kV and above). It can be said that "oil-free" is a development trend and an important equipment policy for switchgear.

But oil switches are relatively economical and have rich experience in use, so in the next 10 years, there will still be a certain proportion of medium and high voltage switches.

The above examples are only recent developments in switchgear. There are also some medium to long term potential for the development of switch devices, such as superconducting switches, static electronic switches (non mechanical switches), and highly environmentally friendly switches. Due to technological and economic limitations, it is difficult to have substantial start-up and development in the near future.

7. Trend of Integration of Various Professions In the 1950s and 1970s, various specialties of power transmission and transformation equipment, such as transformers, switches, lightning arresters, transformers, and secondary control protection measurement systems, had clear division of labor and boundaries, and did not interfere with each other. Nowadays, with the emergence of GIS, C-GIS, mechatronics switchgear, and prefabricated substations, the various specialties of power transmission and transformation equipment, as well as strong and weak electricity specialties, have been tightly integrated and difficult to separate. Therefore, the high-voltage electrical engineering profession should not only adapt to the trend of integration and development of various professions, penetrate each other, break down professional barriers, but also infiltrate and integrate with electronic technology, computers, and secondary systems. In short, we should have a clear understanding of the development trends of high-voltage electrical appliances listed above, especially for manufacturers engaged in the high-voltage electrical appliance industry, they should adapt to market trends, readjust professional configurations, and moderately develop products with technical reserves to welcome the arrival of the new generation of high-voltage electrical appliances.

Conclusion: In terms of high-voltage capacitors, SG6 technology, vacuum technology, combination technology, etc. have been applied to product structures and have basically achieved "oil-free". In the process, there have been introduced shell production lines, vacuum epoxy casting and injection molding equipment, mechanical machining centers, etc. At present, based on market research, high voltage electrical equipment market transaction rates, and customer feedback, domestic equipment with voltage levels of 500KV and below can meet domestic needs, and its technical parameters have approached or reached the national advanced level.

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2021 03-10

Accurate Discharge Methods of Power Capacitors

Method 1:

Start by unplugging the electrical appliance.

Use a 20,000 ohm, 2 watt resistor, which can be bought in most electronics stores at a very low price.

Connect the probe of the resistor to the terminal of the capacitor to discharge the capacitor.

If the capacitor has three terminals, connect the resistor to one of the outer terminals and the middle terminal, and then connect the remaining one of the outer terminals and the middle terminal.

Method 2:

Connect one end of the resistor to a probe and the other end to a crocodile clip. Wrap it with insulating tape.

The crocodile clip is clamped to the ground wire, and the other pole of the capacitor is connected with the meter pen. There will be no spark when discharging.

It is necessary to note that if you continue to discharge a lot of capacitors, the resistance will heat up, so you can choose a larger wattage.

Other methods:(capacitor)

For lamp discharge, method 2 is similar to 100-200 watt lamp.

Use a 60-80W soldering iron to discharge, the method is similar.

Insulation grounding discharge.

pour ：

Do not test without professional knowledge.

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