1、why want to compensate reactive power
In recent years, rectifier, inverter, electric traction locomotives, rolling mill, electric arc furnace such as nonlinear, impact and unbalance industrial load increasing, makes the power quality problem increasingly prominent, for distribution network to the safe and stable operation of the power system and the normal work of electrical equipment has also had a very serious effect and harm. World industrial load power quality problem is serious, the electric iron is facing the voltage fluctuation, new energy sources such as wind power and solar energy grid-connected unstable factors, which leads to some important construction site power supply system of power compensation requirements increasingly urgent.
Compared with the loss of useful work in the grid, busywork loss is much larger, this is because the high voltage line, transformer equivalent reactance is much larger than the resistance, and transformer excitation reactive loss than excitation energy loss is bigger, have proved the grid of the most basic reactive power, generator reactive power from the far cannot satisfy the demand for reactive power of power grid. Due to loss of reactive power in power grid transmission and distribution line transmission is not stable, both to reduce the power factor, increase the line loss, produced a large number of voltage fluctuation and flicker, and line power three-phase imbalance, reduced power grid transmission capacity and transient steady limit, at the same time also produces a large number of harmful harmonic, so it is very necessary for power grid reactive power compensation. In addition, the power grid reactive power compensation can take appropriate devices and power grid voltage, choose the appropriate location in the long distance transmission lines set up the reactive power compensation device, also can improve network performance, improve the transmission capacity, the rational allocation of reactive power load side, can improve the power factor of power supply and distribution system, reduce the power loss, therefore, the role of reactive power compensation in power grid has received widespread attention.
2、Why do you want to purify the harmonic
Along with the advancement of science, computer and network monitoring host, DCS, PLC, frequency conversion device, UPS, advanced instrument, instrument, rectifier, switch and server, metering device, a storage device, signal processing system, vehicle control system and other advanced equipment widely used in metro, high-speed rail, airports, aerospace, stadium and other fields, the nonlinear load will produce surge, pulse, electromagnetic interference, such as low second harmonic power of pollution. These headed by harmonic power pollution, in turn, can cause great pollution to the equipment and power system. As the direct causes of low harmonic voltage instability (surge phenomena), the controller misoperation, frequency conversion device overvoltage trip, burn out SCR, motors, transformers and other power equipment. And the computer data system, control system, signal system, due to the higher harmonic harmonic interference and error causing misoperation caused directly communication signal data disorder, navigation, failure, flights, underground parking car crashes and other accidents. Harmonic wave specific as follows:
●Increase the load of electric power facilities, reduce the system power factor, reduce power generation, transmission and effective capacity and efficiency of electrical equipment, equipment waste, waste circuit and power loss.
●Caused resonance and harmonic current amplification, reactive power compensation capacitor lead to damaged by over current or over voltage of capacitor set or cannot be put into operation.
●Ripple torque motor vibration, impact, product quality and machine life.
●Due to eddy current and skin effect, make the motor, transformer, transmission line produce additional power loss and overheating, waste of electricity and accelerate insulation aging.
●Harmonic voltage, is proportional to the peak voltage enhances the insulating medium, in the form of electric field intensity, reduce the service life of the equipment.
●Zero sequence several times (3 times), harmonic current will lead to the centerline of the three phase four wire system overload, and to produce circulation in the delta connection of transformer winding, the winding current exceeds rating, serious when even cause an accident.
●Harmonic change protection relay action features, cause misoperation of relay protection facilities, relay protection device such as a automatic work disorder.
●Harmonic changed the rate of change of voltage or current and peak, delay the arc extinguishing, impact breaker breaking capacity.
●Make measuring instrument, especially the metering error of induction watt-hour meter.
●Interfere with the adjacent power electronic equipment, industrial control equipment and communications equipment, affect the normal operation of the equipment.