Investigation On Power Supply System Reliability Of Large-scale Petrochemical Enterprise

The products of petrochemical enterprises are inflammable, explosive, toxic, and strongly-corrosive. The distinct characteristic of large-scale petrochemical enterprises are high continuity of production process, high automation, complicated technology, various facilities and easy to cause the ruinous accident. So that the requirement of reliability, continuity and security for enterprise power supply is critical.After the 1000KTA ethylene project is constructed in 2008, the power generation and supply system of ZRCC would be marked with the following characteristics: large capacity of power supply system, more than 400MVA; strong capability and proportion of self-power; low capacity and large amount of self-provided generators; complicated power grid shared by power generation, supply and distribution; various power supply voltage; cable power distribution system widely applied because Ningbo located in thunderstorm area; large amount of high voltage and capacity generators in plant areas; and the startup of high capacity motors, especially, for the purpose of process continuity, the re-startup of some motors after very short time of power failure, which impact significantly on reliability of power system; also, the harmonic, generated by a large number of power electronic equipments applied in petrochemical firms, casts a shadow on reliable operation of primary and secondary equipments linked with power grid.One side is that high continuity of production process, high automation, complicated technology and products are inflammable, explosive, toxic, and strongly-corrosive. On the other hand, power grid structure for petrochemical enterprises is complicated. Therefore it is necessary to carry out the overall process reliability study for petrochemical enterprises' electrical system. So that this could greatly increase the reliability of design, production, application and maintenance and enhance the reliable operation for petrochemical enterprises' electrical system.The thesis begins with design of reliability for petrochemical enterprises' electrical system characteristics, combine the LLC equipment management philosophy with equipment reliability, and determine the fault tree application and in power grid structure and operation mode. According to the characteristics of petrochemical enterprises' electrical equipment and long experience, the Barretter starting is applied for large motor startup to overcome the disadvantage of traditional step-down startup. In view of continuous operation for petrochemical enterprises, the traditional backup power self-starting is changed to residual voltage so that the backup power technology is improved. According to the actuality of integrative power generation, transfer and distribution in ZRCC, and stable operation of power generator, the new ASVG(Advanced Static Var Generator) has been introduced in power distribution system to enhance the Var control of the power plant and reliability of the voltage. Based on the working experience, the UPS connection mode has been improved to guarantee the online maintenance when if any UPS failure. Because petrochemical enterprises are marked with the characteristics of high load, high reliability requirement of power supply and power cable used for power supply and distribution, the neutral grounding method has been applied in to resolve the issue of single phase over-voltage.Application of overall process reliability philosophy in largescale petrochemical enterprise electrical system would greatly ensure the reliability of power supply, increase the profit and promote the international competitiveness.