In 110kV substation power quality monitoring, the main factors affecting power quality are various non-linear electrical equipment, transformers and various iron core reactors, which can be divided into the following categories: 1. Power electronic devices, this serious harmonic source. These devices produce a large number of harmonics in the process of rectification, inversion, voltage regulation and frequency conversion; 2. Electric arc furnace, such as AC arc furnace for steel making; 3. Household appliances, such as fluorescent lamps, TV sets, speed regulating fans, air conditioners, refrigerators, etc.; 4. Various high-tech equipment, such as electronic computers, power regulators, energy-saving lamps, etc. For the substation, a large number of power electronic equipment and various large capacity motors in the surrounding factories are the main harmonic sources, followed by a large number of urban household electrical equipment and so on.

On power quality monitoring, harmonics not only affect the normal operation of user equipment, but also have a great impact on power grid equipment and automation devices. For the influence of harmonics on power grid automation devices, the manufacturing process and working principle of automation devices should be improved, the anti-interference ability of devices should be strengthened, and the misoperation of devices should be prevented. However, it has no effect on improving the power quality of the power grid, and can only reduce the impact of grid harmonics on automation devices. Therefore, the power quality management system should strengthen the management of grid harmonic sources and change grid parameters to reduce or eliminate harmonic resonance.

For the harmonic generated by the motor controller, the shape of the harmonic is very clear, and the harmonic filter can be installed to reduce the harmonic current.

For users with special needs, isolation transformer can be installed: limiting the third harmonic of equalization.

When an active power filter is installed, a current is injected to compensate the harmonic current generated by the load accurately, and a pure positive dark wave will be obtained. Because the equipment works in parallel with the power supply system, it only controls the harmonic current, and the fundamental current does not flow through the filter. At present, active power filter is widely used.

For the power grid, we should optimize the power grid parameters, high side operation mode, installation location, mode and capacity of reactive power compensation device, eliminate the harmonic or reduce the amplification effect of power grid on harmonic.

In order to improve the power quality of 110kV substation, a series of measures need to be taken

The neutral point of 10kV and 35kV voltage transformer is equipped with nonlinear resistance;

Installing harmonic elimination device on 10kV bus

Change the parameters of 10kV shunt compensation capacitor to eliminate resonance and reduce the effect on harmonic.