The winter record for instantaneous electrical energy demand on the Peninsula was set on December 17 2007, at 18:53 h, with 45.450 MW. The historical maximum for summer was set on July 19 2010, at 13:26 h, when it reached 41.318 MW. This data confirms the progressive closing of the gap between the maximum winter and summer values.

The maximum instantaneous power of wind energy was recorded on 29 January 2015 at 7:27 pm, with 17,553 MW, representing an increase of 2.9% on the previous maximum of 17,056 MW, recorded on 6 February 2013.

The maximum hourly production of wind energy was also set on 29 January 2015 with 17,436 MWh between 7:00 and 8:00 pm, an increase of 3.1% compared to the previous maximum of 16,918 MWh on 6 February 2013.

Similarly, the maximum of daily wind energy was reached on 12 February 2016 with 367,341 MWh an increase of 2.77% compared to 357,741 MWh on 30 January 2015. 

From a technical point of view, an interconnection allows the national electrical systems to achieve a greater reliability in covering the demand and a greater stability and guarantee of the frequency and voltage. Moreover, it guarantees supply security in the areas near the borders as the neighbouring electrical system can provide support should any problems occur.

The economic benefits are derived from the inherent potential for the execution of mutually beneficial exchanges between systems or their agents. Additionally, the increase in meshing generally reduces the transmission energy losses, which results in the better economic operation of the combined system. The interconnection additionally provides a reduction in the need operational reserves as well as the possibility of the better management of surpluses and a better utilisation of the power stations.

The total commercial capacity represents 3% of the Peninsula’s actual demand. A new interconnection line that will connect Spain and France via Catalonia is underway, doubling the current interconnection capacity. However, this will still be far below the European recommendations which establish a figure of at least 10 % for interconnection capacity between national electrical systems.

The aforementioned importance of the benefits makes the interconnection with the European system of vital importance for the Spanish electrical system as it would allow it integration into a superior system.

This high voltage line addresses three specific necessities: guaranteeing an adequate level of supply to cover the increasing demand in the Gerona area, supplying the high speed train and reinforcing the interconnection with France. Additionally, reinforcing the aforementioned Spain/France interconnection is a prerequisite in order to facilitate the secure integration of the enormous potential of wind power in Spain.

The special regime control centre (Cecre) is located at Red Eléctrica's Madrid head quarter and is the world's first control centre dedicated to integrating a country's special regime generation, particularly wind power, into the electrical system operation under secure conditions.

It is the only centre in Europe specialised in the training of electrical system operators. This school, created by Red Eléctrica, provides the operators with adequate training in a variety of system operation situations and scenarios, from the simplest to the most complex and that due to the characteristics and design of electrical systems require that the operators have the knowledge of how they need to be managed, such as recovering the service after a disturbance.

The Operation School possesses a training simulator, which is the core instrument which allows the operators to interact with the electrical system in a similar way as they would in real situations.

Voltage, expressed in the electrical system in kV (equivalent to 1,000 volts), is the difference of electrical potential between two points of an electrical circuit. It is increase/decrease in potential energy per unit of charge.

On the other hand, power, expressed in the electrical system in MW (equivalent to 1 million watts), informs us of the energy produced or consumed per unit of time, the second.

The frequency of the voltage wavelength is the parameter which informs us of the balance that exists between generation and consumption, and that must be present within the electrical system to prevent a disturbance that could lead to a loss in supply to consumers. Expressed in Hertz (Hz), the balance is perfect in the European system when its value is 50 Hz.

A grid is meshed when it has different connections between substations, allowing energy to flow via alternative routes in the event that one should fail. This characteristic facilitates having a more robust system when faced with disturbances and performing maintenance that would not be possible to execute without causing supply outages.

It is the set of actions and activities that are necessary to guarantee the continuity and security of the electrical supply, and the correct functioning of the production and transmission system, ensuring that the energy produced by the generators is evacuated and delivered to the distribution networks complying with the quality and security requirements set out in the regulations currently in effect.

The high voltage transmission grid on the Peninsula is made up of lines, substations, transformers and electrical elements with voltages equal to or higher than 220 kV. Also included are those other installations, independent of voltage, that fulfil transmission functions or play a role in international interconnections. The distribution network is made up of lines, substations, transformers and electrical elements with voltages less than 220 kV. In the case of the Canary and Balearic Islands, the transmission grid is made up additionally of lines with voltages equal to or higher than 66 kV.

The transmission grid allows the transmission of large quantities of energy over long distances, whereas the distribution network is an intermediate element between the transmission grid and the final consumers that has less energy transmission capacity in regard to distance and magnitude.

The burying of a 220 or 400 kV line can represent a significant deterioration of the area crossed, and its magnitud will depend on its value and sensitivity.

An example is the partial burying of the San Sebastián de los Reyes-Morata-Loeches line, impacted by the Barajas Airport plan. This case, however, cannot be extrapolated to other projects, as with different environmental conditioning factors, the environment could be impacted. Consequently, due to environmental and technological limitations as well as its cost, the massive burying of electrical transmission lines is not advisable. 

Scientific studies have proven that the exposure to electromagnetic fields generated by high voltage electrical installations do not pose a risk to health. The electromagnetic field at the nearest point to a line is 10 microteslas, whereas the World Health Organisation considers 100 microteslas as the maximum reference allowable for public exposure.

We are surrounded by electrical appliances, such as the microwave, that generate an electromagnetic field larger than that of a 400 kV line.

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A voltage gap is a sudden fall in voltage which occurs as a consequence of a short-circuit in a node of the electrical system, which in turn is dealt with by the protection equipment. This phenomenon occurs when some generators, like wind turbines, which are not yet able to support short-circuits, disconnect abruptly when one is detected.

The collision of birds with electrical transmission lines (220 and 400 kV) generally occurs with ground cables (which protect the lines from electrical discharges during storms), these cables are less visible as they are smaller in diameter than conductor cables. For this reason, the activities aimed at reducing the risk of collision is based on marking these lines by means of devices which increase their visibility.

Regarding transmission lines, those equal to or superior to 220 kV, it is impossible for electrocution to occur because the distances which separate the conductors of the different phases from each other, or from the metallic parts of the supports, are too big thus making it impossible for a simultaneous contact to happen.