PSI - Issue 48

Aleksandar Šotić et al. / Procedia Structural Integrity 48 (2023) 266 – 273 Šotić et al / Structural Integrity Procedia 00 (2023) 000 – 000

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probabilities and uncertainties, the logical choice is to work on eliminating, reducing and controlling the hazards and possible unwanted outcomes, in other words, to work on building the system safety. An important system feature, such as safety, must be built into the system design - it cannot be simply, effectively and effortlessly added to an already built system. The theory behind this work is based on systems theory, systems engineering and cognitive engineering, i.e., to the concept developed by prof. Nancy Leveson (2004). The paper will touch on several current examples from HE reality in order to demonstrate the usability and power of the presented methodology.

2. Materials and methods 2.1. Example of HPP Pirot

The example that will primarily be taken into consideration is HPP Pirot. The reason for considering the safety of HPP Pirot is a series of events that have followed this HPP in recent years. The authors of the paper do not have technical documentation for HPP Pirot, and the data presented are public (EPS and HPP Pirot internet portals, as well as press clippings). Zavojsko Lake and HPP Pirot are an example of an exceptional project and engineering endeavor, when a natural disaster, a landslide that blocked the Visočica River valley in February 1963, was used to build a system of great strategic importance, the clean water reservoir, with useful volume over 150 million m3, and the Pirot HPP, which was completed and put into operation in 1990. HPP Pirot, located on the outskirts of Pirot, is a derivation type HPP with tunnel, pipeline under pressure (penstock) and a reservoir for annual management of flows. Zavojsko Lake reservoir, which was created by a dam at the village Zavoj, uses the waters of the Visočica River and its tributaries. On average, the power plant is capable to a daily peak load diagram when flow variations are extreme, and consumption peaks are short-lived and sharp. The HPP system will be described below by structuring and specifying the physical components of the system (reconstructed according to the available data for the purposes of this paper, possibly not fully precise).

Fig. 1. Schematic representation of the Pirot Hydraulic Engineering System

Projects and official reports are one side of story as some of the issues remain 'between the lines'. On the other hand, press clippings served as a reliable overview (and additional source) of events that caused public reactions, that is, what could be characterized as "unwanted events or conditions" in the sense of the definitions in the Introduction. A very brief chronological overview of the press clippings is given below:  (2013) City swimming pool in Pirot, designed and constructed as a HPP compensation pool, transferred to the City of Pirot.  (2015, summer) Due to the algal bloom in bathing water, the city swimming pool in Pirot is closed to the public use; Local authorities blame HPP Djerdap operating mode, for not providing enough fresh water.