Electrical losses on the federal transmission system

If equipment overheats, some of the power it generates is dissipated (either manually or by force) as heat.

Origin of active electrical losses 

Active electrical losses correspond to power that is dissipated as heat, either by natural ventilation or by being forced to cool down to keep the equipment’s operating temperatures below the limit specified by the manufacturer.

The active losses primarily consist of:

  • losses due to the magnetisation of transformers once they are active (‘iron losses’ or ‘no-load losses’); losses due to the heating of windings in transformers when current is flowing through them (‘copper losses’ or ‘load losses’);
  • losses due to the heating of conductors in overhead lines and underground cables as a result of the power transmitted by such equipment.

While losses for the first group remain virtually constant, losses for the other two groups vary depending on the square of the current transmitted by the equipment in question and also depend on the manufacturing characteristics of the equipment (length of the circuit, cross section of conductors and type of materials used in the conductors).

Method for determining losses

To determine the quantity of energy dissipated via losses during a given period, every day Elia records a lot of situations observed during the real-time operation of the grid. This makes it possible to calculate the individual losses of each electrical circuit, factoring in the actual current running through the equipment in question.

The variety of situations encountered makes it possible to accurately take account of:

  • the actual configuration of the grid (equipment taken offline for maintenance, changes to circuit topology, etc.);
  • the amplitude and profile of international power exchanges;
  • the configuration of injections into the grid;
  • the amplitude and profile of offtakes from the grid.

For any given situation, the power lost on the grid is equivalent to the sum of losses on all equipment on the grid in question.

The energy lost during a given period is equivalent to the sum of power lost in all situations during that period, with each situation weighted according to the duration of the occurrence.

Basis for calculating active losses on the federal grid

The Belgian federal electricity grid currently comprises equipment operating at nominal voltages of 380 kV, 220 kV and 150 kV. This equipment includes overhead lines, underground cables, phase shifting transformers and voltage transformers which interlink these voltages.

The basis for calculating active losses on the federal grid to be compensated in kind (see below) includes all equipment, excluding equipment that is part of grid users’ connections.

Actual losses via connection equipment are attributed directly to the grid user in question and are part of that user’s offtakes from the network.

Compensation in kind by the Access Responsible Party

Each Access Responsible Party must compensate active network losses for all of its network accesses (as per Article 161 of the federal Grid Code – Royal Decree of 19 December 2002). Active losses observed on the federal grid are compensated in kind by the sum of contributions by the Access Responsible Party in question.

To formulate – in an objective, transparent and non-discriminatory way – the contribution expected from each Access Responsible Party, the contribution is expressed in the form of a percentage of net offtakes linked to the portfolio of the Access Responsible Party in question.

Elia calculates the percentage on the basis of forecast losses and estimated future offtakes.

  • As of 1 January 2017, the applicable percentages will be:
    • Peak hours (weekdays from 8am till 8pm): 1,35%
    • Long off peak hours (weekdays from 8pm till 8am and week-ends): 1,25%
  • As of 1 January 2016, the applicable percentages will be:
    • Peak hours (weekdays from 8am till 8pm): 1,35%
    • Long off peak hours (weekdays from 8pm till 8am and week-ends): 1,25%
  • Percentages applied in 2014:
    • peak: 1.20%;
    • off-peak: 1.00%;
    • weekend: 1.05%.
  • Percentages applied in 2013:
    • peak: 1.05%;
    • off-peak: 1.00%;
    • weekend: 1.00%.
  • Percentages applied in 2012:
    • peak: 1.2%;
    • off-peak: 1%;
    • weekend: 1.05%.

The concrete application of this compensation percentage is set out in Article 11 of the Access Responsible Party (ARP) Contract.

Previous losses recorded by Elia