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 Banks, aerospace, subway, high-speed rail, airport, stadium, etc, the nonlinear load will produce surge, pulse, electromagnetic interference, such as harmonic pollution of power. 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 deal to stop, data disorder, flights, parking car crashes and other accidents. Harmonic specific hazard is 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.