Evaluation of Fault Level of Sensitive Equipment Caused by Voltage Sag via Data Mining
Abstract :
So far, there is no literature to evaluate the fault level of sensitive equipment(FLSE) caused by voltage sag from the perspective of the power grid. In practice, although the FLSE are dominated by the voltage sag of node, the voltage sag of the node is associated with whole power grid, including the voltage grade and location of the node, the distance between the concerned node and location of fault, and the weather and date at the time of fault, which are all named as voltage sag properties (VSP). In view of this gap, this paper evaluates the FLSE using the long-time monitoring data of VSP of some regional power grid by data mining method based on multi dimensional matrix simplification and the improved gray target theory .The data mining process can be divided into three steps: 1) construct a data base consisted of VSP and FLSE using long-time monitoring data, 2) mine the association rules between VSP and FLSE by multidimensional matrix simplification, and 3)match some actual scenario with the mined association rules by the improved gray target theory .Performance and effectiveness of the proposed method are verified through the simulation and field case.
? VOLTAGE SAGS are one of the most harmful power quality disturbances for sensitive end-users.
? Enormous resources are lost every year due to industrial equipment malfunctions as a consequence of voltage sags.
? Most of the severe voltage sags are caused by Voltage sags have been registered by usual Digital Fault Recorders (DFRs) installed on the transmission lines.
? The recording is setup for both over-current and under-voltage events.
? Voltage sags were characterized by the minimum rms voltage and the duration faults on the transmission and distribution grids.
? The gray target theory is proposed for solving the multi-polar and multi-attribute mode decision problem.
? According to the polarity of each index , the bull's-eye can be determined in the target.
? In the mining process of association rules, VSP require to be transformed into qualitative values, so the mining association rules need to be represented by qualitative values of different dimensions.
? The magnitude and duration of the sag are randomly located in any region of the tolerance curve.
? This paper introduces the concept of cost of the un served energy”, assuming that this represent an end user’s cost.
? The cost of the utility was assumed to be the cost of reparations plus the loss of revenue
? The effect of voltage sags on industrial loads has been the focus of previous papers and several mitigation methods to improve equipment’s ride-through capability have been proposed.
? When several voltage sags were registered within one minute, only the one with the minimum magnitude was considered.
? This paper employs the energy loss function and the tolerance curve of sensitive equipment to calculate the failure rate of equipment caused by voltage sag.
? The advantage of the method is that the failure rate can be calculated only based on one voltage sag event without the need for long-term voltage sag data .
? Propose the improved gray target theory to make the matching result more accurate and avoid the multiple matching results.
? Performance and effectiveness are verified through the field case.
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