DINGXIN SULAWESI NICKEL PLANT SVC PROJECT

Customer Needs
Dingxin Group has invested in Indonesia to explore the local nickel ore resources and produce nickel alloy in Sulawesi Island.
In project phase-I, totally 3pcs*11MVA ore furnaces had been used to melt ores and produce nickel alloy. Ore furnaces are such a kind of loads that is similar with electric arc furnaces but working more smoothly. However the situation during its boring stage is still tough with high three-phase unbalances and voltage fluctuations. And things become even worse in week grids.
The nickel alloy plant was powered by its own power generation plant of merely 2*65MW. As it's such a small grid with no inter-link with the outside world, the network is very week and easily failure when powering such impacting loads.

Before the SVC was introduced into this system, "the power generators trip 4~5 times every day due to its unbalance protection, which is so annoying and caused so much loss to us", said by the plant operation engineers. Sometimes the furnaces can even hardly operate. This became a big headache ever since the plant was put into operation.


RXPE Solution
It is noticed that unbalance is the most key problem in this case. And static var compensators can be one of the possible measures to mitigate the unbalance of the ore furnaces.
- Generators: 2pcs * 35kV/65MW
- Ore furnaces: 3pcs * 11MVA+20% overload



After a careful system study and simulation, it shows that a 75Mvar SVC at 35kV busbar can solve the problem. The SVC was rated as -25Mvar (inductive) to +50Mvar (capacitive) with a total dynamic reactive power range of 75Mvar. The SVC branches were connected at the 35kV busbar, same with the ore furnaces.
In order to mitigate the three-phase unbalance, a control strategy with combined close-loop and open-loop controls are adopted. The open-loop control mainly focus on three phase balancing and voltage fluctuation, while the close-loop control will take care of the power factor compensation. Below is a comparison of unbalance mitigation with/without SVC：


From this comparison we see that the SVC detects the loads'real-time currents, and then compensate certain amount of unbalanced currents to have successfully mitigated the three-phase unbalance. This had finally made the ore furnaces appear as "balance loads".



Customer Benefits
The Sulawesi nickel plant SVC was delivered in the year 2015. It had successfully solved the unbalance problem of the loads. The plant's power generators had operated smoothly with no more trips again after the SVC was put into operation. Customer is so happy that they had purchased another two of RXPE SVCs for their project phase-II in the same year.



Liaoning Rongxin Xingye Power Tech Co., Ltd
108 Keji Rd., Anshan 114051 China
Email: overseas@rxpe.com


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