Improvements of Large Power Transformer Condition Real Time Monitoring and Diagnosis Expert System - a Romanian Experience

摘要

On-line monitoring and diagnosis of the primary equipment of high voltage electrical substations is generally recognized as necessary and beneficial for power companies, constituting one of the priority actions in developing SMART GRIDS. In Romania, and probably elsewhere, there have been and there are still different opinions on the opportunity of implementing and regarding the volume of high voltage equipment in a certain substation that needs to be on-line monitored, for reasons determined by the cost of the investment (versus overall efficiency) and by concerns regarding the maintenance of jobs both for operation and maintenance personnel. In Romania, during 2010-2013, CNTEE Transelectrica (the Romanian TSO) implemented a Smart Grid pilot project consisting of the on-line monitoring and diagnosis of all the primary equipment (power transformers, shunt reactors, circuit-breakers, disconnectors, current and voltage transformers, surge arresters) of three high voltage power substations, namely 400/110 kV Darste, 220/110 kV Gradiste and 220/110 kV Mostistea substations. In this paper it is made an analysis of the effectiveness of the mentioned online monitoring systems, in the detection and analysis of two incidents produced on-site (one at the 250/250/80 MVA 400/121/20 kV power transformer in Darste substation, and the other one at a 200/200/60 MVA 231/121/10.5 kV autotransformer in Gradiste substation). It also shows the dependence of the fault detection time and of the alarm time, to the on-line monitoring method, presenting also a comparison with the conclusions resulted from the off-line diagnoses and analyses done on-site, and how these conclusions influenced the management decisions. The paper mentions new rules for interpreting the results and for the management of the data, new rules resulted as necessary due to the way in which the on-line monitoring and diagnosis systems emphasize the production of electrical discharges inside power transformers.