Improved maintenance of secondary substations using grid digitalization benefits

Digitalization of the network

The digitalization of the network is, in general terms, to increase the level of automation and observability of the grid. Digitalization not only is applied at electrical networks but also in other fields such as telecommunication networks. The automation is part of the digitalization. Automation means that it is possible to do something remotely.

Telemetering improves automation. In the distribution network, the digital infrastructure and automation aim to improve the quality of service. The collection of all the data that is available in the network has to be well organized and analyzed.

Digitalization is applied at a distribution level in three parts of the grid:

High Voltage Distribution Grid (>36 kV)

The level of digitalization is the highest. High voltage grid has a great level of automation. In addition to the digital devices that are placed in substations, there are also smart meters for generation plants (thermal, wind, solar…) and for big industries that are connected to the high voltage grid.

In this case, there are smart meters (type 1 and 2, so as to measure the energy produced and consumed and there are also smart meters in substations from High Voltage to Medium Voltage in order to verify both measures.

Medium Voltage Distribution Grid (1-36 kV)

In this part of the grid many digital devices have been deployed recently. These devices are reconnectors, disconnectors, switches, circuit breakers, voltage and current sensors, etc. They detect outages that cut the supply, for instance, when there is a short-circuit in a line due to a tree fall or after striking a flock of birds.

Remote Management and new remote control technology has also been introduced in Secondary Substations. There are also smart meters of type 3 in order to register the energy consumed and generated by plants connected to MV.

In general, digital devices are put in strategic places in the network. They are also used to, in case of a fault, to feed the clients affected and reduce the number of people affected by the lost of supply, reducing also the time of interruption.

Low Voltage Distribution Grid (<1kV)

In the LV network, smart meters have been deployed in the last 6 years. Currently, 60% of meters have “smart” functions in Spain. Apart from smart meters, there are also other digital devices, such as data concentrators (DCs) that transmit the information from smart meters at regular intervals to a central system (metering system and network supervision).

This Master Thesis focus on the Low Voltage Distribution Grid.

The development of distribution networks always favors technologies that are simple, reliable, robust and economically viable. By contrast, evolution of network operation favors improving system monitoring and control.

The collected information from smart meters, sensors, concentrators and other digital devices is processed by various software for:

• Supervision and command (Supervisory Control and Data Acquisition (SCADA)/Distribution Management System (DMS)), to analyze the state of the system, identify and localize faults, and carry out recovery actions when necessary.
• Forecast management of consumption and generation based on past usage data collected by the smart meters, and of forecast programs by the flexibility aggregators, which allow to estimate future congestions and constraints.
• Asset management, to evaluate at a longer term maintenance and modernization needs based on historical data (power quality, incidents, increases in peak consumption and/or generation, etc.).

Finally, special equipment is also deployed for transmitting commands issued by the dispatching centers or at the suppliers’ request:

Remote-controlled operation devices, which allow opening and closing breakers/switches (either to optimize the operation scheme or reconfigure the network during disruptions).