Power quality is a major concern for utilities, military affairs, industries, transport and infrastructure segments.
The marjor problems existing in the power quality:
-The poor power factor -Harmonic pollution -Three-phase imbalance -Unstable voltage -High/low voltage
-The harm caused by poor power factor problems
The remote transmission of the reactive power in power grid reduces the network loss and low voltage;
System power factor can not meet the national standard, resulting in the power tariff fine;
Load mutation, power grid flicker, etc cause the drop of the quality in power supply;
The capacity of the power distribution system increases, thus increasing the investment in equipment.
-The harm caused by the serious harmonic pollution
Causing the reactive power compensation capacitor resonant and the harmonic current amplifying, resulting that the capacitor group are damaged due to over-current or over-voltage or can not put into operation;
Zero sequence (3 times) harmonic current will lead to the centerline overload of the three phase four wire system, and produce circulation in the transformer winding of the delta connection, the winding current exceeds rating, serious when even cause accidents；
Harmonic will change the action characteristic of protective relay, cause misoperation of relay protection facilities, make the automatic equipment such as relay protection work in a mess;
Harmonic changed the rate of change and peak of voltage or current, delay the arc extinguishing, impact the breaking capacity of the circuit breaker;;
Interfere with the adjacent power electronic equipment, industrial control equipment and communications equipment, affect the normal operation of the equipment;
Affect the motor efficiency and normal operation, resulting in vibration and noise, shorten the motor life;
Due to eddy current and skin effect, make the motor, transformer, transmission line and so on generate power loss so that overheating, waste electric energy and accelerate the aging of insulation;
Cause the resonance of power network.
-The harm caused by the three phase current balance
The impact for the transformer
Three-phase load imbalance caused increased transformer losses and reduced efficiency
Three-phase imbalance may cause the transformer to burn
Three-phase unbalanced operation causes zero phase sequence current, so that the transformer is local heat the impact for the high-voltage lines
Increase the loss of high-voltage lines
Increase the trip number of high-voltage lines, shorten the life of the switch equipment
the impact for the low-voltage lines
Increase the loss of low-voltage lines
Make certain low voltage phase current and temperature be too high or even burned
the impact for the users
Three-phase voltage imbalance causes user equipment to burn.
One phase or two phase load are too big, will lead to excessive decline of line voltage, result in low terminal voltage.
The electrical terminal voltage is low, affecting the user to use electricity in production and life.
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