Client: A Leading Aluminium Company Based at Chhattisgarh
Objective: Reliability Assessment for Power Supply Network
Duration: 5 months
Study:
The major concern with power failures to the aluminium plants was that the molten aluminium froze within hours after loss of DC power. And the cost to restart the process was very high. What complicated matters further was that these plants were located at different locations.
Techlabs did a reliability study of the power supply to the existing and new smelter plants. The electrical system reliability analysis study was to ensure the power supply continuity under system, environmental and plant disturbance conditions.
As per the process information available from the client, a power outage of about 3 hours was manageable in terms of revival of the frozen aluminium. Hence, the total power supply failure to the pot lines for duration more than 3 hours was considered as the criterion for conducting the reliability studies. The client was to indicate the cost to restart the process in case of such power failures, as this data was required to evaluate the annual risk cost and to perform cost analysis.
Approach:
The scenario called for an integrated solution that starts with, of course, data acquisition and creating an exhaustive database, analysing the data thus obtained.
Reliability is an indication of the ability of a component or system to perform its intended function during a specified time. The performance of the electrical network in an industrial plant is evaluated through standard indices. To calculate the load point reliability and protection zone reliability indices, we used the information given by the client such as equipment failure rate and restoration time.
The system was modeled in a power system simulator by Techlabs. Network Impedance data, technical parameters of all equipment, generation & load values, as furnished by the client, were used for system modeling. For the purpose of the reliability indices calculation, we used the information given by the client from the log book entries. Basically, we extracted the data such as failure rate and restoration time for each of the equipment indicated in the SLD.
System analysis was completed by reducing the “minimal cut-sets” to only those components that will produce a forced down time failure greater than 3 hours, the time estimated for the aluminium to freeze in the process. The relevant system reliability indices were calculated. Thereafter, different alternatives like redundancy of certain equipment or upgradation of equipment for better system performance were studied and the indices once again calculated for these new options. So the different options in case studies we performed are compared by calculated reliability indices with those options.
Conclusion:
Various schemes have been suggested in the report to improve the power supply reliability with cost benefit analysis for the proposed investment.
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