Supplement, split supplement, mixed supplement
Common compensation, separate compensation and mixed compensation, in simple terms, refer to whether the switching is a three-phase capacitor or a single-phase capacitor in the compensation device.
What is "co-supplement"?
The traditional contactor operates three-phase together, that is, when it is closed, all three phases are closed, and when it is disconnected, all three phases are disconnected. In this case, the capacitor used for compensation is a three-phase capacitor. Compensating the entire three-phase circuit at the same time is called common compensation. It is also called "three-phase compensation"
The advantages and disadvantages of a total supplement:
The control is simple, the price is low, the reliability is good, and the maintenance is convenient. Low requirements on the compensation controller. Insufficiency, when the three-phase is unbalanced, it cannot be compensated, or the more it is compensated, the more unbalanced.
What is "divided up"?
Because most of the high-power, high-load equipment in the power grid, they are very easy to cause three-phase imbalance during operation. When these devices work, only two-phase voltage is needed, and the other phase is not used at all, which causes three-phase imbalance. At this time, if you want to compensate, you can only compensate for two phases, otherwise there will be a problem of unbalanced reactive power. Therefore, some new switching switches such as composite switches and thyristor modules have begun to appear, which can work independently for the three phases of A, B, and C. Which phase needs to be switched on and off. This kind of compensation for single phase is called "divided compensation"
Generally speaking, if the maximum power imbalance does not exceed 15%, there is basically no need to make up for it. The reason is that the power supply bureau assesses the average power factor, and the unbalance within 15% can easily reach the standard after the average is compensated.
Advantages and disadvantages of sub-complement:
It can deal with unbalanced occasions with high compensation accuracy. Insufficiency, expensive, complicated control, complicated circuit. Difficulty in overhaul and maintenance. High requirements on the compensation controller.
What is "mixed supplement"?
When compensation includes both a common compensation branch and a separate compensation branch, we call this compensation method "mixed compensation". It means "separate supplement" and "share supplement" to work together.
In fact, in the case of three-phase imbalance, when the vacancies of each phase are inconsistent, in this case, a split compensation scheme is adopted. However, if all the sub-compensation branches are adopted, the cost will be very high. Therefore, it is hoped that the total supplementary branch can be used to compensate for the shortfall of the basic part, and the sub-compensation branch can be used to compensate the unbalanced part.
When using a hybrid compensation scheme, it is required that the incoming cabinet sampling must use three mutual inductors. For example, in the system, phase A needs reactive power 20kvar, phase B needs reactive power 25kvar, and phase C needs reactive power 30kvar. The system first puts in a set of 20kvar common compensation circuit, then puts a set of 5kvar separate compensation circuit into phase B, and puts a set of 10kvar separate compensation circuit into phase C to meet the system's demand for reactive power with the most economical investment. .
Compensation system in which the total compensation and the separate compensation are arranged at the same time. Usually sub-supplement accounts for 20% to 40%.
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