1, the negative effect of reactive power in distribution system
In theory, the reactive power flows only in the grid, only the form of the conversion, does not consume energy, such as in the sinusoidal circuit, the pure inductance in a cycle of absorption of the average power is equal to zero. But in the distribution system is not ideal pure inductance, pure capacitance circuit, affected by the hysteresis, eddy current, magnetic saturation of useless air gap factors such as exchange of energy in the electromagnetic, will cause the reactive power flow is not equivalent, but the consumption, the consumption is called reactive power consumption.
The reactive power consumption of the distribution line is 10% of the total reactive power consumption of the distribution system, because the total reactive power loss is proportional to the square value of the current, the greater the load, the greater the total reactive power loss. In addition, the greater the proportion of the large cross-section conductor (line impedance value and the cross-section of the conductor) reactive power consumption.
2, the analysis of reactive power consumption of double winding transformer
Transformer reactive power consumption including excitation reactive power consumption (independent of load) and the leakage reactance of the reactive power consumption (and load) part two. The transformer is a kind of inductive reactive load. In the process of power transmission, the reactive power consumption of the transformer is much larger than the active power loss. Therefore, it is necessary to analyze the reactive power consumption. The consumption is related to the factors such as the transformer manufacturing technology, material and load rate, and the reactive power consumption accounts for about 20% of the total reactive power consumption of the distribution system.
3, reactive power consumption analysis of three-phase asynchronous motor
The equivalent circuit of asynchronous motor and transformer equivalent circuit, reactive power consumption and leakage reactance excitation and reactive power consumption of asynchronous motor, due to the special structure of the asynchronous motor, the main magnetic field through the air gap between the stator and the rotor are closed, so the motor reactive power consumption than its active power the loss is much greater, at the same time, the reactive power absorbed is much larger than other electrical components. The operating characteristics of asynchronous motor, motor no-load, no-load current at this time most of the magnetizing current (reactive current), so its efficiency in the light load and no load, the power factor is very low, the motor needs to absorb reactive power from the grid a lot. At the same time, it means that the reactive power consumption is increased, and the loss accounts for about 70% of the total reactive power consumption of the distribution system.