ECONOMIC AND MARKET IMPACTStable operation of the national power system

Power system in Poland

Ensuring access to electricity requires an efficiently operating system that enables its seamless generation, processing, transmission and distribution. All the equipment connected to this system, together with consumers’ installations, form the national power system.

The power system belongs to a special type of critical infrastructure, as it determines the security of society, the economy and the state. This system is centrally controlled. The National Dispatching Center, the so-called dispatching service of PSE, is responsible for the operation of the Polish power system.

Cross-border connections

The national transmission system operates:

  • synchronously with the systems of the states of the Continental Europe (ENTSO-E),
  • with dedicated power units of the Dobrotwór power plant of the Ukrainian system,
  • non-synchronously with the Swedish system via a DC submarine cable,
  • non-synchronously with the Lithuanian system through a DC back-to-back converter station.

Fig. Cross-border connections

Transmission system management in the NPS

The operation of the transmission grid takes into account the needs of electricity consumers nationwide.

The current operational security of the power network is ensured by the dispatching services of the TSO and DSO as well as the operational services of generators and customers operating in a hierarchical system.

The national power system has the following hierarchy of dispatching services:

  • National Dispatching Center (KDM) - manages the operation of the 750, 400, 220 kV transmission grid, as well as selected 110 kV lines of system importance,
  • Area Dispatching Center (ODM) - manages the operation of the transmission grid and the switching operations of the 750, 400, 220 and 110 kV transmission grid,
  • Central Dispatching Centers, Branch Dispatching Centers (CDM, OCD) - manage the operation of the 110 kV distribution network and switching operations in the distribution network of 110 kV and below.

The dispatching services of TSOs cooperate directly with the dispatching services of DSOs (Central Dispatching Centers, Branch Dispatching Centers) and with the operational services of power generation companies (Power Plant On-Duty Engineer - DIRE). This cooperation is carried out in accordance with the Transmission Grid Code.

Fig. Organisation of dispatching services in the country

The cooperation of TSOs with TSOs of neighboring countries with respect to network operation is carried out in accordance with the terms and conditions set out in the ENTSO-E/UCTE network codes and conditions specified in bilateral agreements.

Balancing of power demand

In order to provide the generation capacity necessary to meet the demand, as a Transmission System Operator, we implement a coordination planning process for different time horizons. This process includes annual, monthly, and daily coordination plans.

The schedule of activities related to the development of plans and the scope of forecast and published data is defined in the Transmission Grid Code.

Coordination plans are designed to allow the levels of excess capacity available over forecast demand to be met as required during the assumed period. This is achievable by coordinating the repair and maintenance schedules of generating units and shutdowns of meshed network elements, taking into account plant and network constraints and planned inter-system exchange restrictions.

To ensure continuity of energy supplies and balance the system even under adverse conditions, we have a number of tools at our disposal during periods of peak electricity demand:

  • the capacity available in generation units that are not centrally dispatched units,
  • additional capacity at power plants in overload conditions, i.e. with more than nominal capacity (as part of system services),
  • contingency capacity supply from pumped storage power stations, which allow for short-term (2–4 hours) balancing of power demand (as part of system services),
  • dispatching capacity exchange with neighbouring TSOs,
  • Demand Side Response service provided on behalf of the TSO, i.e. DSR.

Measures to ensure reliable operation of the transmission system, including reliability metrics

PSE purchases system services to ensure secure and economic operation of the power system and, in particular, the achievement of the required reliability and quality parameters.

System Services:

  • Control System Services (RUS):
    - participation in primary control,
    - participation in secondary control,
    - under- or overload operation,
    - participation in automatic voltage and reactive power control.
  • Start-up service for Generating Units (start-up service).
  • Control-related system services representing pumped storage generating units:
    - participation in automatic voltage and reactive power control (ARNE),
    - compensation operation.
  • Control system services as part of the contingency reserve:
    - Contingency reduction of power consumption by consumers based on a bidding process (IRP).
  • Participation in the automatic voltage and reactive power control for generating units not actively participating in the balancing market.
  • Availability service for non-Centrally-Dispatched Generating Units (GWS service).
  • National power system restoration service.

On 5 April, 2021, the need to ensure that the NPS could be balanced necessitated the use of a countermeasure in the form of a non-market reduction in the generation of wind sources, amounting to approximately 1,000 MW, between 10:00 a.m. and 2:00 p.m. The need to reduce generation from wind sources was triggered by a large surplus of electricity supply over demand for electricity, due to the accumulation of high generation from wind and PV sources with a low electricity demand on that day.

The reduction was applied as a last resort, after other remedies available to the TSO had been exhausted. The non-market generation reduction was performed at the recommended level. It made it possible to balance the NPS and, in particular, to achieve the necessary controllability of the negative power reserve.

The formal basis for the TSO's non-market generation reduction were the provisions of Regulation (EU) 2019/943 of the European Parliament and of the Council, Commission Regulation (EU) 2017/1485, as well as the Energy Law and the Transmission Grid Code.

System operation reliability indices (ENS, AIT)

The indices describing the continuity of power supply and the duration of power interruptions (ENS and AIT) were calculated for a group of delivery points, which include end users and electricity DSOs with one delivery point from the transmission grid. Shutting down the delivery point of these customers results in an interruption of energy supplies from the transmission grid.

To determine the reliability of network operation in accordance with applicable regulations, ENS and AIT indices for emergency outages are calculated

Worth knowing

System operation reliability indices

ENS – the index of energy not supplied by the power transmission system. It is expressed in MWh per year and is the sum of the products of the capacity not supplied due to the interruption and its duration. This index includes short, long and very long interruptions and outages with and without consideration of catastrophic outages.

AIT – index of the average interruption time in the power transmission system. Expressed in minutes per year, it is the product of 60 and the index of energy not served (ENS) by the power transmission system divided by the average capacity supplied by the power transmission system expressed in MW.

In 2020-2021 and 2018, there were no events resulting in emergency power interruptions and outages to consumers at delivery points from the transmission grid identified as above. The indicators calculated for 2017 and 2019 reflect emergency interruptions and outages, the reasons for which are described below.

There was one emergency interruption resulting in no power to the consumer in 2019. The interruption lasted approximately 36 hours and was caused by a spontaneous shutdown of the 110 kV line from which the consumer drawing power from the transmission grid was supplied. The immediate cause of the interruption was a ground fault due to a tree coming close along the line section.

In 2017, there was one emergency interruption that resulted in an approximately 3-hour failure in electricity delivery to one consumer supplied from the transmission grid. The interruption was caused by an emergency manual shutdown of the power supply lines. The cause of the power cut to the consumer was a third party’s climbing a 220 kV line tower. The shutdown of other devices, lines and transformers associated with the site was dictated by safety concerns.

Low levels of the ENS and AIT indices demonstrate a high level of operational reliability of the transmission grid managed by PSE, as well as to the reliability of power supplies to customers connected to that grid.

ENS and AIT indices for all outages (planned and emergency)

In 2021, there was an increase in the values of the ENS and AIT indicators calculated for all shutdowns, when compared to the previous years. It was mainly due to a scheduled outage, a much longer one than in previous years, for one of the consumers supplied from the transmission grid, due to an extensive scope of work carried out by the TSO on the consumer's power supply assets (extension and modernisation of an autotransformer bay in the 110 kV switchgear). The date of the outage was agreed in advance with the consumer.

The low values of ENS and AIT indices have a positive impact on the confidence of consumers connected to the transmission grid. The reduction of the number and duration of planned outages in the supply of electricity to consumers results, among other things, from the implementation of a system to optimise the schedule of repair and maintenance works of transmission grid elements supplying the consumers. The shutdowns in the case of scheduled outages are carried out by PSE at times agreed with the consumers – usually during periods of no energy consumption as declared by the consumers. As a result, during outages, customers adjust their demand or use other methods of supplying electricity (e.g., from the DSO network).

WCD – electricity supply continuity index

Electricity supply continuity index

To determine the continuity of electricity supplies, the so-called WCD index is calculated.

Worth knowing

The index was calculated as the total amount of electricity supplied to transmission service consumers (DSOs and end users) divided by the sum of the amount of electricity not served and supplied to these consumers during the year.

Maintaining the supply continuity indices at a high level is the result of the TSO's operation and maintenance policy for transmission assets.

The amount of electricity not supplied to transmission service consumers during the year was determined taking into account both scheduled and unscheduled interruptions in energy supplies to consumers. The index used in the calculation of the total amount of electricity supplied from the transmission grid during the year is the volume of electricity taken from the transmission grid at all delivery points by end customers and DSOs connected to the transmission grid.

Actions taken by PSE to maintain continuity of electricity supplies to consumers:

  • Preparation of coordination plans for network works in the long and short term horizons.
    The work schedules for both the maintenance and repair of network elements and generating units are prepared in such a way as to ensure that the required levels of surplus capacity available over the forecast demand are met over the assumed period and that the required criteria for safe operation of the network, including the reliability criterion (n-1), are met.
  • Development and implementation of a uniform operating model allowing for cyclic, standardised and measurable assessment of the technical condition of equipment and its operating environment. Thanks to these actions, the most worn-out and oldest elements of network assets – potential sources of emergency and disturbance conditions – are preventively replaced.
  • Implementation of the operating services development programme. It allows for continuous improvement of the competence of our own maintenance services, including those performing work in the field.
  • Taking investment activities. Optimises the load on transmission lines and eliminates overload conditions on transmission system elements.
  • Systematic standardisation of network equipment and creation of a storage base. It allows to make necessary replacements quickly and in a financially optimal way.
  • Working closely and making arrangements with the transmission service consumers at every stage, from planning to implementation.

Index of electricity losses in the transmission process

The process of electricity transmission is inextricably linked to energy losses. They result from technical losses, which are caused by physical phenomena occurring in the electrical power network (voltage and current losses). The magnitude of the losses depends on a number of factors, the most important of which is the electricity flow in the network – the amount of generation and demand, and weather conditions.

TSO-owned networks have managed to maintain a low proportion of losses in recent years. When compared with previous years, this indicator has been significantly reduced in terms of the TSO network flow. This is best represented by a chart showing electricity input and output to the TSO network.

2021 was a record year for PSE in terms of energy flows in the network – the year-on-year electricity input increased by as much as 12%. Thanks to adequate projects in grid infrastructure, the record flows did not significantly affect the loss ratio. In 2021, the loss amounted to 1,712,542 MWh, representing 1.47 % of the total electricity input to the system.

Engineering security of critical infrastructure and a coherent protection system

We are an enterprise of strategic importance to the national security. Our company is:

  • a critical infrastructure operator,
  • the owner of facilities subject to mandatory protection,
  • the owner of facilities of particular importance for the safety and defense of the state,
  • an enterprise of particular economic and defense importance.

Certain tasks and responsibilities have been imposed on PSE in connection with these functions.

As an operator of critical infrastructure, PSE is required to ensure the protection of the company's facilities15. In accordance with the National Programme for Critical Infrastructure Protection, this obligation is understood very broadly and includes activities aimed at ensuring physical, technical, personal, ICT and legal security, as well as ensuring continuity of operations and the ability to restore critical infrastructure.

15Such obligations are imposed on PSE under the Act of 26 April 2007 on crisis management, the Act of June 10, 2016 on anti-terrorist activities, the Act of March 18, 2010 on the special powers of the minister responsible for state assets and their exercise in certain capital companies or capital groups operating in the electricity, oil and gas fuel sectors, and the Act of August 22, 1997 on the protection of persons and property.

The standard of our company's substation fencing reduces the risks arising from the analysis of the potential hazards that may occur in relation to PSE facilities. Principles have been adopted as the basis of the technical specification to ensure the security and protection of all PSE assets, i.e. employees, equipment and sensitive information. In 2021, PSE inspected the technical condition of substations on an ongoing basis according to the Instructions of organisation and performance of maintenance works on EHV lines and substations. In addition, the Technical Protection Department has completed the Technical Protection System (SOT) pre-commissioning tests at the individual EHV substations, after which it monitors the performance of the aforementioned systems on an ongoing basis. The technical condition of the Technical Protection Systems is directly linked to the use of appropriate forms and methods of applying or reinforcing existing physical protection at the individual facilities.

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