Why do low-voltage switchgear need capacitance compensation?
Dec 30, 2020
In the low-voltage power distribution part, there are incoming cabinets, outgoing cabinets, and of course capacitor compensation cabinets. What is the role of the capacitor compensation cabinet? As the name suggests, it plays a role in capacitor compensation. Let’s take a look at the principle of capacitor compensation. When compensating, the capacitor and the load are connected in parallel. The capacitor is the same as the electric bank. When the load increases, the output voltage of the power supply will drop due to the internal resistance of the power supply. The two ends of the capacitor must maintain the original voltage, which is A part of the electricity in the capacitor will flow out, delaying the downward trend of the voltage, which is the principle of capacitor compensation.
1. The compensation principle of power capacitors
In principle, a capacitor is equivalent to a generator that generates capacitive reactive current. The principle of reactive power compensation is to connect the device with capacitive power load and inductive power load in parallel on the same capacitor, and the energy is converted between the two loads. In this way, the load on the transformers and transmission lines in the grid is reduced, thereby increasing the output functional power. In the case of outputting a certain active power, the loss of the power supply system is reduced. In comparison, capacitors are the easiest and most economical way to reduce the load on transformers, power supply systems, and industrial distribution. Therefore, it is imperative to use capacitors as reactive power compensation in power systems. At present, it is very common to use shunt capacitors as reactive power compensation devices
2. Features of power capacitor compensation
advantage
Power capacitor reactive power compensation device is easy to install, easy to increase or decrease in installation location; low active power loss (only about 0.4% of rated capacity); short construction period; small investment; no rotating parts, easy operation and maintenance; individual capacitor bank damage, Does not affect the operation of the entire capacitor bank and other advantages.
Disadvantage
The shortcomings of power capacitor reactive power compensation devices are: it can only be adjusted in stages, and cannot be smoothly adjusted; poor ventilation, once the capacitor operating temperature is higher than 70 ℃, it is prone to expansion and explosion; poor voltage characteristics, poor short-circuit stability, There is residual charge after removal; the accuracy of reactive power compensation is low, which is easy to affect the compensation effect; the operation and management of the compensation capacitor is difficult and the problem of the safe operation of the capacitor is not taken seriously.
