Classic approach to preventive maintenance of equipment in power system substations was based on periodical maintenance according to regulations and best practices recommended by vendors. SCADA system in HOPS is used primary for real-time monitoring and control of the equipment in substations. Real time data available in SCADA databases contain useful information for substation maintenance optimization based on operational conditions. Malfunctions and failures in the substations are monitored via SCADA system. Analyses of these data can be used to evaluate maintenance strategy and plan the reconstructions and replacement of the equipment. This article presents current maintenance management approach in HOPS, which is the only transmission system operator in Croatia, and possible improvements in efficiency of equipment maintenance using SCADA data. Prerequisite for the analyses of these kinds of data is standardization and unification of information names and structures. HOPS put a lot of effort in standardization of SCADA data during last refurbishment of control centers. Use of SCADA data for analysis drives the need for standardization and vice versa. Examples of statistical analyses of the SCADA data are done on multiple levels. High level analyses is used to provide the global overview of the real time data. It can point to suspicious information that require detailed analyses. The signals that appear often in the list can indicate that there is a problem in the primary equipment, monitoring system or alarm configuration. Low level analyses can be done on target information important for equipment maintenance. In this paper some low level analyses are presented for switching equipment, transformer lifetime, equipment in operation, and tap changer operation. An analysis is made for number of switching operations for breakers and disconnectors in different operational conditions. Preventive maintenance should be done based on number of switching in normal operations and even more often for breakers that are often interrupting fault current. SCADA data can be used for availability of the equipment and duration of failures thus providing valuable information to managers. An analysis on RTU communication availability is shown.

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Operating personnel in control room act on SCADA alarm generated on data from station computer. Using new technologies and advanced technical solutions assistance tool can be designed. This tool provides quick help in busy situations for operator. For this new tool with three types of case studies insight will be given in this paper. Introduction part has short information about numbers of alarms and events in Control centre, and their distribution during one month period. Basic principles for alarm handling in SCADA system is given with all limitations. New tool, Intelligent Alarm Processing system is designed and implemented in control room. It has connection to SCADA system with standard data exchange format CIM/XML and run in real time, with only few seconds delay. This system based on Multilevel Flow Model has root cause analyses implemented for power system. Detail fault location algorithm description with block scheme for this Intelligent Alarm Processing system is part of third chapter. Special attention must be paid for modelling protection data in SCADA system which are sent to this new tool. Demonstration of Intelligent Alarm Processing system operation is reported in fourth chapter. Three characteristic disturbances in transmission network were elaborated. Most complex and challenging disturbances for operator in control room is cascading event. This case study is presented in detail in four sequences through graphical user interface. Second case study is also challenging for operators, heavy winter storm with numerous isolated events. In this case study very effective graphical presentation and alarm list with three types, primary event, consequences and detail list for this events were demonstrated. This list pointed out exactly and clearly what happened in the network. Last case study presents common disturbances which appears on daily basis, where this tool is of great assistance because it points on transmission elements very fast.