Maintaining the transmission network

Our network infrastructure also includes a 450 kV submarine cable line of 127 km in length. The length of the entire line connecting Poland with Sweden is 254 km.

The condition of the transmission network is confirmed by a high collective transmission equipment availability factor ( DYSU ), which reached 99.77 percent in 2019, with the reference value of 99.5.

The maintenance of network assets requires permanent supervision of the operation and condition of individual elements of the transmission network. Operation supervision services were established for the purpose within the Operations Department in 2016: the Supervision Centre (Centrum Nadzoru, CN) in Konstancin-Jeziorna and five Regional Supervision Centres (RCN) in Warsaw, Radom, Katowice, Poznań and Bydgoszcz. The Regional Supervision Centres are functionally subordinate to the Supervision Centre and are responsible for their designated areas of PSE’s network assets.

The main responsibilities of the operation supervision services include:

• Exercising ongoing supervision of the operation and condition of network assets owned by PSE (on a 24/7 basis);
• Ensuring the continuous controllability and observability of facilities, equipment and systems;
• Ensuring the availability and operational security of equipment;
• Supervision of work in progress;
• Performing switching and control operations in accordance with the operational allocation of responsibilities between the KDM/ODM dispatch services and the CN/RCN operation supervision services;
• The coordination by Regional Supervision Centres of operation instructions for substations and lines by performing the coordinator function pursuant to the provisions of the Occupational Health and Safety Manual for work on power equipment and systems;
• The planning and optimisation of maintenance and new build work on PSE network assets;
• Cooperation with units of Distribution System Operators, generators and contractors.

The CN/RCN operation supervision services play a key role in the event faults or failures occur in transmission network assets during which actions are initiated and fault elimination processes are activated on the basis of signals from SCADA systems or notifications from other entities. The services monitor the condition of transmission network equipment on an ongoing basis, defining time or quantitative constraints in their operation, affecting the operational management conditions.

Actions taken by CN/RCN services in the event of failure include:

• the analysis of causes, origin and extent of disturbance,
• organisation of incident site protection,
• taking the decision on the method of disturbance elimination,
• dispatching available resources of O&M Teams (ZES) and Specialist Engineers (I-SPEC) in order to organise the elimination of disturbance,
• supervising and coordinating disturbance elimination work.

In the event an extensive cross-zonal failure occurs (between responsibility areas of territorially competent RCNs), the individual RCNs cooperate with one another. In such a case, the Supervision Centre coordinates all activities of PSE’s operation services from different areas and subcontractors commissioned by PSE.

In the interest of ensuring operational continuity, the CN/RCN operation supervision services are prepared to provide for a potential crisis situation that necessitates leaving the regular workplace, without losing the ability to perform basic tasks, primarily to exercise continuous supervision over the operation and condition of network assets. In 2018, the process of commissioning backup CN/RCN locations was completed. Since 1 January 2019, the centres have been providing full functional redundancy for the primary centres, owing to which they significantly improve the operational continuity of CN/RCN operation supervision services.

In the network assets maintenance process, the CN/RCN operation supervision services supported by O&M Teams (ZES) and Specialist Engineers (I-SPEC), who have the requisite knowledge and skills for direct work on equipment. There are 28 PSE O&M Teams established across the country. Through their work, ZES employees ensure the security of operating as well as diagnostic and maintenance activities. The competence and specialised skills of ZES employees are maintained at a high level owing to systematic technological training. Besides, owing to the maintenance personnel development programme launched, the training provided is comprehensive and systematic.

Of the 107 electrical substations owned by PSE as many as 73 are controlled and supervised remotely, which allows switching operations to be performed from KDM/ODM/CN/RCN superior centres, thus facilitating the operation of the PPS. Other substations are successively adjusted through upgrades to the remote control and supervision standard. In the substations in which the remote control and supervision function is restricted from superior centres; all operations are performed by substation or ZES personnel.

The O&M personnel work mentioned above allows the transmission network to be maintained in a proper operational condition, which enables dispatch services to fulfil their duties related to network operation management.

There are many external and environmental factors that pose a real hazard to the operation of EHV transmission lines, but what has become a growing problem in recent years is the non-woven fabric of various types used in agriculture/orchard growing. Due to the incorrect fastening to the ground and wind gusts, the fabric turns into a kite flying freely in the air, which, when coming into contact with an obstacle in the form of power line elements, effectively wraps around tower structures, isolators, current-carrying wires or earth wires. Strips of flying agricultural non-woven fabric are long enough to simultaneously catch on current-carrying wires of all phases and touch the ground. This poses an obvious risk for transmission line operation and for members of the public. The identification of such a hazard necessitates the protection of the incident site by responsible services and emergency shutdown of lines (often classified as “must-run” in terms of system operation) in order to eliminate the hazard. Non-woven fabric removal work takes at least several hours, for reasons such as the need to prepare safe work zones, the use of aerial work platforms, and because the fabric is often intricately tangled with line elements. Every unscheduled line outage for such work generates high costs and involves personnel including O&M Teams, forcing them to interrupt scheduled work. In 2019 alone, 9 unscheduled lone outages caused by agricultural non-woven fabric were reported, with the number of such cases increasing year on year.

PSE inventory management for network assets is aimed to ensure that a necessary stock of equipment, devices, spare parts, subassemblies and items is kept for the correct maintenance of the company’s network assets. In addition, inventory management is to enable the collection of stock for the purposes of ongoing tasks and the maintenance of the organisation’s asset infrastructure.

Coordination of work as part of the network asset inventory management is the responsibility of the Equipment and Material Reserves Operator (hereinafter: Reserves Operator). The basic task of the unit is to maintain inventory at a sufficient level in accordance with the quantity standard set by PSE’s Operations Department, specifying the minimum quantities of particular equipment types to be kept in stock in order to ensure the operational continuity of the company, e.g. in an emergency situation. In addition, inventory not subject to the quantity standard is also held in storage.

Currently, the following items are kept in storage:

• primary circuit equipment, including circuit breakers, instrument transformers, disconnectors, surge limiters, auxiliary transformers,
• secondary circuit equipment, including protection devices (distance, unit, earth fault, differential), power plant automatic voltage control (ARNE), transformer station automatic control (ARST), relays, transducers,
• HVDC components: equipment dedicated to the Słupsk DC Substation,
• line components, including EHV line supporting structures, glass and porcelain insulators, line accessories, wires, cables,
• power transformer components, including e.g. bushings and tap changers.

The withdrawal of equipment and materials from reserve stock together with the provision of required means of transport and loading is the responsibility of the Logistics Centre which operates on a 24 hour basis. Work of the Logistics Centre is performed jointly by the Reserves Operator (during the warehouse working hours) and by Radom RCN (in afternoon and night hours, on weekends and public holidays). Quick response and efficient transport may significantly reduce the time to repair major failures in the PPS.