Research And Analysis Of Cascading Failure In Oilfield Electric Power System

A series of power failures have happened worldwide in recent years, the cascading failure is the main cause of the power system failures. So it is urgent to study and analyze for cascading failures. The old method to analyze power system is building the math model after dividing electric network into four parts such as generate electricity , transmit electricity, power distribution and load, this method can not do well in studying the cascading failures of power system ,and it is hard to warn people the beginning of cascading failures. Therefore, we need the whole sight to concern more about the study of cascading failures from the entirety network angle, thus most possibly guarantees the power system's brittleness not stimulated frequently.Daqing oilfield has 4 electric plant and more than 300 110(35) kV electric stations and 4000 kms all kinds of transportion lines. According as oilfield electric power system, this paper proposed a definiteness method of brittleness study of cascading failures which based on the other author's achievement. Firstly, it built a math model of system, mainly concern the right action of relay protection during the simulation. FP/OLP will cut the line in 0.1ms when the power of line reached the 200% of power rating.The power failures in the last few years indicated that most large scope power failures is transmit network run at the extreme limit, the power has transmitted largely because of event of low probability, and cause the adjacent component overload, the overload trip arouse the power failures.After cut the line ,the condition of cascading failures research are: (1)the load of network and the power of generator do not change;(2)the line is lossless line ,that is ,the delivered power and absorbed power do not change;(3)no considering the situation of malfunction and refusing action of relay protection.Based on the IEEE39 ,this paper regard the condition of judging the terminate of cascading failures as: (1)the cutting line lead to split of system, it can be deemed that the system lose stabilization, the search route of cascading failures is stopped; (2) the depth of cutting is larger than 6, but the system has not destabilized , the search route of cascading failures is stopped;(3)there is no more line cut during the simulation of cascading failures;(4)the power flow algorithm do not convergence, it can be deemed that the system lose stabilization, and needn't to continue to solve.Based on lots of documentation, this paper confirms the theory of study and analysis of cascading failures are :(1) Chose initial fault firstly, i.e. Chose the line which can arouse cascading failures to study. Three steps method of initial fault search is presented in the paper. Namely ascertain key transmission surface firstly, Chose the branch line of initial fault based on centricity model secondly, and ascertain special key branch line of system thirdly.(2) Resolve the ground power flow based PQ method, i.e. calculate voltage value and angle of every node according to given types of system node, then calculate power flow of head terminal and end terminal.(3) chose initial fault branch line to open and calculate the distribution of power flow in branch line left using integrate PQ method and compensatory method one by one, i.e. the calculation of system opening power flow.(4) Analyze the transient stabilization and calculate the angle difference of arbitrate two generators. If the angle difference exceed 180 degree, it can be deemed that the system lose stabilization. Stop calculation. Otherwise come into the next step.(5) Compare the opening power flow and setting power flow of every branch road. branch road is opened if the opening power flow is bigger than the setting power flow and then carry the opening calculation over again. End the calculation if the opening power flow of all the branch roads is all smaller than the setting power flow.(6) Export the result of all the opening branch roads. At the same time opening order is also exported orderly during the process of exportation. If the opening of one line cause overload at lines over two, chose one line to open.(7) Form fault tree of opening road according to the basic theory of fault tree. The top layer of fault tree means the lost of system stabilization miss. Initial fault branch line is at the substrate layer of fault tree and cascading failures opening road is at the middle layer. It can be got the fault tree of cascading failure in daqing oilfield line.(8) Calculate the fault tree quantitatively including the calculation of occurring probability of cascading failures and scalpel collect etc.In the end, using the C# to oilfield electric power system program and calculate the cascading failures of IEEE39. Including the power flow calculation, after power system's failures and the data display of power flow after redistributed; the choice and display of initial fault line; the analysis of initial fault line; the judging and execution of automatic ending conditions; the formation and display and analysis of fault tree.