Research On Potential Accident And Risk Assessment Of Fujian Power Grid Based On Regulations

"Regulations on accident investigation and handling of electricity safety emergency" (Regulations for short) promulgated, higher requirements that electric power enterprises guarantee the stably and reliable supply of power system operation, and avoid accident effectively are brought forward. During the 12th and 13th Five-year Plans, leaping development and increasingly complicated operation bring more challenges to security and stability of Fujian power grid. So knowing the security level and taking corresponding prevention and control measures have hugely significance to Fujian power grid which is still developing. Compared with traditional methods, risk assessment combing probability and severity, can present the probability of contingency while introducing electrical, economic and social indicators to evaluate severity. Therefore, developing risk evaluation system (the first stage) of Fujian power grid based on the grade of accident defined by the Regulations, which by static security evaluation based on risk assessment, introducing the grade of accident defined by the Regulations as one of indicators, and ranking the contingency according to the ratio of the load loss, the system accomplish that combing probability and the grade of accident, presenting the likelihood and severity from an administrative perspective, and providing technical support for senior decision making.Because N-1 fault of Fujian power grid 220kV and 500kV system cannot bring about accident defined by the Regulations, multiple faults are main problems that should be considered. As the network expansion, the exponential combinations of multiple faults cause a problem called "curse of dimensionality", but only few of these disturb seriously the stability of power system operation. The critical question that the risk evaluation system must address is investigating a method that filtering the faults which are not of concern and generating fault sets whose size is ideal for computing.Based on the above project, this paper studies a method that generates N-2 fault sets of that cause line over-load. Refer it as severe failure sets for convenience narration. This paper puts forward the following two methods:one is diagnosing the faults that caused the other lines overload more quickly using power flow transfer; the other is excluding the multiple faults that influence domains have no intersection by combining the power flow estimation and influence domains.Method 1:Compared to the power flow calculation taking long time, power flow transfer estimation can quickly and effectively diagnose whether fault cause the other lines overload or not. Various common methods of power flow transfer estimation are compared, then LODF (line outage distribution factor) is used to power flow transfer estimation and severe failure sets generation, and a good result is obtained.Method 2:Through theoretical derivation, it is concluded that the comprehensive effect of two lines can be approximately regarded s the linear superposition of independent effect. So the number of N-2 fault which need detailed analysis is reduced. Using the advantage of LODF computing power flow transfer quickly, generate fault sets quickly that should be analyzed in detail.