Reactive power compensation device introduction.
Reactive power compensation device introduction:
In the power system substation or directly in the power user substation installed reactive power supply, in order to change the flow of reactive power in the power system, so as to improve the voltage level of the power system, reduce network loss and improve the dynamic performance of the power system, this technical measure called reactive power compensation. Reactive power refers to the power component formed when the current flows through the capacitive reactance (XC) or inductive reactance (XL) when there is a phase Angle difference between the voltage U and the current I in an AC circuit. This power in the grid results in voltage drop (inductive reactance) or voltage rise (capacitive reactance) and joule loss (resistance heating), but no effective work is done. Therefore, reactive power needs to be compensated. Reasonable allocation of reactive power compensation (including where, how much capacity and what type) is an important part of power system planning and design. In operation, rational use of reactive compensation capacity and control of reactive power flow is one of the main tasks of power system dispatching.
Produce and influence:
In AC power system, the generator generates reactive power as well as active power, and it is the main reactive power source. In operation, due to the capacitive effect between lines and between lines, part of the reactive power is also generated, which is called line charging power. It is related to the voltage level, the length of the line and the structure of the line. The user (load) of electric energy needs both active power (P) and reactive power (Q), and its size is related to the power factor of the load; The flow of active and reactive power through transmission lines and transformers in a power system results in active power losses (ΔP) and reactive power losses (ΔQ), as well as voltage drops (ΔU). They have the following relationship:
Where P and Q are the active power and reactive power flowing into the transmission line (or transformer), U is the voltage measured at the same point of the transmission line (or transformer) and P and Q,R and X are the resistance and reactance of the transmission line (or transformer) respectively.
It can be seen that the flow of reactive power in transmission lines and transformers will increase the active power loss, reactive power loss and voltage drop. Because the reactance value of transformer and high voltage overhead line is much larger than the resistance value, the loss of reactive power is larger than that of active power, and the main factor causing voltage drop is the flow of reactive power.
In general, the reactive power generated by the generator in the power system and the charging power of the transmission line are not enough to meet the reactive power demand of the load and the reactive power loss in the system. In order to reduce the active power loss and voltage drop, a large amount of reactive power is not expected to flow in the network, so the load center needs to be installed with reactive power supply. In order to achieve reactive power supply in situ, zoning balance principle.
Reactive power compensation can receive the following benefits: (1) improve the user's power factor, thereby improving the utilization rate of electrical equipment; (2) Reduce the active power loss of the power network; (3) Control the reactive power flow of the power system reasonably, so as to improve the voltage level of the power system, improve the power quality, improve the anti-interference ability of the power system; (4) The dynamic performance of the power system and the transmission capacity and stability of the transmission lines can be improved by configuring the appropriate regulator on the dynamic reactive power compensation device; ⑤ The installation of static reactive compensator (SVS) can also improve the voltage waveform of the power grid, reduce the harmonic component and solve the problem of negative sequence current. For capacitors, cables, motors, transformers, etc., it can also avoid additional power loss and local overheating caused by high harmonics.