Capacitor compensation cabinet
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When two capacitor banks are used together, along with two reactive power compensators, and the current and voltage are sampled using the same wire, could over-compensation occur? Is the COS value shown above correct? When used separately at two points on the busbar, what will happen to the sampling current after the first sampling current?
In my opinion, there is no problem with the first option; it’s just that the compensation from the second route occurs later than that from the first route, resulting in a delay in compensation. If the power factor reaches the set value, then the second route will stop functioning. I think the second scenario is also fine, as capacitive compensation operates at the front end of the sampling point, so separating them should be no problem. However, compensating with just two compensation cabinets, in my opinion, is not very good. Could overvoltage occur as a result of one capacitor being disconnected while another is used for compensation?
Over-compensation occurs only when few devices are in use; a portion of the capacitance should be reduced, and it is recommended to use a star connection method for centralized high-voltage compensation
First, let’s clarify one issue: why does over-compensation occur? Over-compensation happens as a result of changes in the load, and the compensation value should be predetermined. Therefore, whether it is parallel capacitors or series capacitors, the magnitude of the current should be determined based on changes in the load. This is precisely the principle behind relay protection – first, detect changes in the load or the circuit, and then have the protection system automatically activate or deactivate the capacitors. Thus, the choice of protection system is quite important. The four leading companies in relay protection in China are NARI, NARI Nanjing (the Nanjing Design Institute is really excellent), XJ, and Sifang; by reviewing their materials, one can see a great deal of expertise there
I would say I basically agree with the opinion above. The occurrence of compensation is an objective reality in the implementation of static compensation schemes! This behavior is particularly evident with impact loads; even the best relay protection and switching systems provide compensation in a stepwise manner. Frequent switching poses a risk of operational overvoltage, and the magnitude of this risk depends on the engineering experience of the integrated supply vendor!
If the load does not change much, manual switching can be used
Personally, I believe that total investment could be overcompensated for, as this can be seen from the power factor meter. A group of capacitors can be switched in or out manually depending on the power factor condition.
Trying a modular compensation capacitor combined with a compensation controller can solve the issue effectively