Causes and response to the fault in Koumoundourou EHVC

Complete restoration of the System operation in less than an hour.

IPTO informs that the incident of February 7 was caused by an electrical internal fault in a 400/150/30kV 280MVA autotransformer located inside the Koumoundourou Extra High Voltage Center (EHVC). In addition, it is noted that the corresponding 150 kV protection circuit breaker failed to operate. The combination of these two faults resulted in the outbreak of the blaze and the loss of power supply through High Voltage in areas of Attica and Peloponnese, which was addressed quickly and safely by the staff of IPTO, achieving the restoration of the System operation in less than an hour.

Specifically, regarding the equipment that has failure, it is noted that the autotransformer was built in 1986 and the circuit breaker in 1972, with both components being put into electrification and operation in 1991, which demonstrates the age of part of the equipment of the Transmission System. In acknowledgement of such condition, the Operator already announced a tender in 2018 for the supply of 10 new autotransformers in the context of the renovation of critical elements of the System. However, due to the appeals against the tender, the procedure was completed in early 2020 and the first autotransformers are expected to be delivered in the near future.

This tender is part of the ambitious five-year Asset Renovation Plan with a total budget of 80 million euros, which was first planned and implemented by the Company in 2018. This Renovation Plan provides targeted gradual replacements of obsolete components of the equipment in accordance with the prioritization set by the competent technical services of IPTO. Indicatively for 2021 and 2022, equipment renovations of 16.5 million and 21 million euros have been budgeted respectively.  

However, the Operator assures that, regarding the operation of the System after the incident and until the new autotransformer to be received and installed at Koumoundourou EHVC within three months, the smooth operation of the Transmission System will be ensured, without disturbances for the consumers, with proper plan and distribution of loads and production. The cooperation with HEDNO, PPC and Corinth Power will contribute substantially to this.

In addition, within the next few days, the contract for the complete reconstruction of the Koumoundourou EHVC is expected to be signed, which includes the replacement and expansion of the existing 150 kV and 400 kV switchgear equipment with modern closed type technology equipment (Gas Insulated Substation), as well as the addition of new power autotransformers and compensation reactors. The new EHVC will be put into operation in 2023 and will supply 21 lines of 150 kV and 4 lines of 400 kV, taking over much of the load in the Athens basin. In addition, the Attica-Crete cable will be interconnected in the new facilities of the EHVC, as well as the Eastern Corridor of Peloponnese (Megalopolis-Corinth-Attica).

Particularly, regarding the electricity system of Attica, in order to ensure the necessary level of reliability based on modern electricity needs, it is necessary to upgrade the Argyroupolis EHVC to High Voltage (from 150 kV to 400 kV), as well as the complete reconstruction of the EHVC in Rouf, in order to create additional, strong nodes in the Basin corresponding to the Koumoundrourou EHVC and Pallini EHVC.