Realization of reactive power compensation in distribution transformer monitoring system

Abstract

In term of operating condition in distribution system,a system based on GPRS networks is proposed by taking a practical distribution monitoring system as an example. The structure and operational principle of reactive power compensation function in this system is introduced in details. Distribution transformer terminal takes the reactive power as criterion, tracks the reactive power changes, switches the capacitors dynamically. In order to make the control more reasonable, reactive power and voltage criterion is taking as the main criterion to switch the capacitor groups. That is controlling the capacitor bank under the precondition that the voltage is not over the bound, by the principle that less reactive power absorbing from the power system of the transformer. As a result, the voltage quality can be improved, the power factor can be raised and network losses can be reduced effectively, switching oscillating and reactive-power reversing can be prevented. Besides some other constraint conditions of the capacitor banks are used as the auxiliary criterion, such as threshold of voltage and current harmonic content protection and less switching times of capacitors. This system has functions of limit alarm, over-voltage protection, under-voltage protection and open-phase blocking protection. Distribution monitoring is an important research direction on power system research. Reactive power compensation, as an important part in distribution system reformation, deserves attention greatly. A reactive power automatic compensation equipment which is applied to low voltage side of distribution transformer is designed in this paper. The proposed system can be provided with a multifunction, such as reactive power compensation, transformer operation status monitoring, distribution harmonic monitoring and analysis, record of active and reactive electricity, time sharing charge of power energy, etc. It can feed the data back to the upper stations, and realize the function of "Three Remote" (remote measuring, remote control, and remote adjustment) by the GPRS communication network. The application results of the distribution monitoring system in the grid are satisfactory.