*3.9. Distributor*

This agen<sup>t</sup> is in charge of carrying the electricity at the final stage of the delivery, between the transmission grid and the final consumers connected to distribution.

Traditionally, the only objective of this agen<sup>t</sup> was to provide the physical infrastructure between the transport grid and the final consumers. However, its activities are now larger due to the amount of information that they manage generated by smart meters. Therefore, it became an information provider too, since it manages all the telemetry and metering infrastructure. This agen<sup>t</sup> as traditionally highly regulated since it was considered a natural monopoly [54]. Nevertheless, efforts to make the sector more competitive are arising [58].

A new critical activity for the distributor is as the "information provider", being responsible for gathering measurements and other information of the rest of the agents so that they may evaluate the response. For doing so, the distribution agen<sup>t</sup> owns a large number of physical assets. Among them are medium- and low-voltage grids, transformers, and consumer's telemetry equipment; the distributor also owns a large advanced metering infrastructure (AMI) that collects large quantities of information. After this, thanks to a measured data managemen<sup>t</sup> (MDM) system, all this information is filtered, processed, and organized in order to obtain valuable information for the correct functioning of the system.

The entities in charge of this agen<sup>t</sup> have to maintain, monitor, and improve the physical assets and provide the collected information. Therefore, the only transactions of this agen<sup>t</sup> are received fees from generators, storage, and consumers. The users of the distribution system bear the costs of its maintenance and modernization via taxes.

## *3.10. Wholesale Market Operator*

This agen<sup>t</sup> is an entity that provides a service, whereby the offers to sell electricity are matched with bids to buy electricity, ensuring the balance between them [59,60].

The main objective is to ensure the correct and transparent functioning of the economic transactions associated with the power sector, as well as organizing the different electricity markets, including wholesale, future markets, and the collection of all the bilateral contracts over the counter (OTC) that have an impact on the system. This information has to be provided to the TSO to ensure the correct functioning of the system.

The WMO is an independent actor in liberalized frameworks, strictly regulated. The WMO is characterized by a trading platform that it controls in order to manage all the bids to buy and sell products. One of its main tasks is to couple the market by matching the sell and buy offers.

Regarding transactions among agents, the generators, storage, and the consumers bear the costs associated with the WMO, paying the fees directly or via a third party. Regarding energy transactions, a minimum level for buying (EW-B) and selling (EW-S) electricity in this market is established depending on its size. Generators and VPPs offer electricity in the market and are compensated with cash flows. These come from the retailers and consumers that participate in the market. Storage has the

capacity to buy and sell electricity to obtain benefits. Thus, cash flows between storage and the WMO are bidirectional.
