The role of low-voltage reactive power compensation. First of all, we need to clarify the concept of reactive power and recognize the importance of reactive power compensation. Reactive power compensation should include compensation for fundamental reactive power and compensation for harmonic reactive power. Here are some related issues and analysis about low-voltage reactive power compensation for your reference and study at work.
(1) What are the standards for compensation cabinets? What are the standards for capacitors?
1) Relevant standards of the Ministry of Machinery:
JB/T 7115-2011 Low-voltage motor on-site reactive power compensation device
JB 7113-1993 Low-voltage shunt capacitor device
2) Relevant standards of the Ministry of Electric Power:
DL∕T 597-2017 Technical conditions for the use of low-voltage reactive power compensation controller
3) National standard
GB/T 15576-2008 Low-voltage complete reactive power compensation device
GB/T 12747.1-2017 Self-healing shunt capacitors for AC power systems with a nominal voltage of 1000V and below Part 1: General
GB/T 12747.2-2017 Self-healing shunt capacitors for AC power systems with a nominal voltage of 1000V and below Part 2: Aging test, self-healing test and destructive test
(2) Why should a power capacitor compensation device be installed in the system?
AC asynchronous motors, electric welding machines, induction cookers and other equipment widely used in industrial production are all inductive loads. During the energy conversion process, these inductive loads make the voltage applied to them lead the current by an angle. The cosine of this angle is called the power factor. When the power factor, i.e. the reactive power, is very large, there will be the following hazards:
1) Increase the line current, increase the line loss, and waste electric energy;
2) Due to the increase in line current, once the transmission line is far away, the voltage drop on the line will be large, and the voltage is too low, which may affect the normal use of the equipment;
3) For transformers or generators, the reactive power is large, and the current output by the transformer or generator is also large. Often, the output current has reached the rated value. At this time, if the load is increased, it is necessary to add another transformer or generator set, which wastes resources; after compensating the capacitor, the output current of the transformer or generator is greatly reduced under the same load, and the load unit can withstand it even if it is increased. There is no need to add another transformer or generator, which can save resources.
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4) Industrial users with a monthly average power factor below 0.92 and ordinary users below 0.9 will be fined at different amounts by the power supply management department.
Adding a parallel capacitor compensation cabinet is one of the methods to compensate the power factor (there are also methods such as using overexcited synchronous motors, phase regulators, and asynchronous motor synchronization).
(3) What are the current standards for power capacitors used for compensation?
The two current standards are:
GB/T 12747.1-2017 Self-healing parallel capacitors for AC power systems with nominal voltages of 1000V and below Part 1: General
GB/T 12747.2-2017 Self-healing parallel capacitors for AC power systems with nominal voltages of 1000V and below Part 2: Aging test, self-healing test, and destructive test