Calculation On Short-circuit Current Of Power System In Alumina Refinery Based On Linear Addition Method

The power system of alumina refinery consists of the captive power station, power network and power consumers in alumina refinery. Along with the development of modern science and technology, the capacity of alumina refinery increases rapidly, and the electricity capacity of some alumina refineries swells more than hundred MW, and electric control level gets higher. While the power load and equipment performance develop significantly, it’s more important to calculate the short circuit current for the purpose of well analyzing the stability, reliability and flexibility of electricity power system.Based on existing short circuit current theory, a new method is illustrated in this article to accurately and fast calculate short circuit current, in the face of overcoming the restrict occurring in the common methods. The linear addition method in short circuit current calculation is applicable in linear circuits, and maintains the same currents and voltages before and after the transformation. The method gains good effects on short circuit current calculation in the captive power station of alumina refinery.The main character of power system in alumina refinery is the multiple generators in the system as well as the electricity networks to keep reliability and quality of the system. The complexity of the system reveals the deficits of usual methods of short circuit current calculation. The indication value method needs a lot of complicate network transformation formula; it’s even out of use in multiple power source points network and complicate power network because of lacking formula in use. The element capacity method could not be used in limited capacity power system due to its being only used in infinity capacity systems. The node catheter matrix method and node impedance method applies complicate matrix calculation, and usually needs software to work out the result, which results in largeness calculation and not being easily checked in engineering.The linear addition method solves those problems above. The transfer reactance of every power source point is calculated individually, which is very easy and clear, then the short circuit current is figured out. The short circuit current arrangement is drew out for every power source point and the whole arrangement is obtained by adding all the short circuit current of each branch of every power source point. The short circuit current calculation of3 generators and electricity networks is illustrated in the article, the process of which is clear tallying with the result of usual methods.In the face of expansion background of many alumina refineries, power system of4generators and electricity networks is put forward in the article. Usual indication value method and element capacity method could not solve such problem. On the other way, the linear addition method analyzes the circuit on individual power source point, which eases the complicate networks, which results in favorable calculation of transfer reactance and current of circuit branch. The method solves the short circuit current calculation in applicable engineer well.This method is validated feasible to calculate the short circuit current of captive power station in alumina refinery. If this method is widely used in short circuit calculation, it can verify the results of matrix operation. In the computer programming, it can save a plenty of calculation time and occupy less memory due to its simple arithmetic without matrix operation. Therefore it’s even helpful in the online calculation of short circuit.