Mesh network (power supply)

A mesh network is a special form of power network in electrical power engineering , which is determined in the topology by a large number of nodes and meshes . Mesh networks usually have several feed points, such as power plants , and distribute electrical energy via several connecting lines, such as overhead lines , to the individual consumers.

The interconnected network at the transmission network level is an example of a mesh network . In addition, mesh networks are used to a lesser extent on the medium-voltage level and in 110 kV distribution networks. Extensive low-voltage networks, especially in urban areas, can in exceptional cases also be designed as a single or multiple-fed mesh network.

General

With an appropriate design, a mesh network offers the highest security of supply compared to other network topologies such as the radiation network and ring network , but is more complex to set up and operate. Consumers, for example individual subordinate substations in the high-voltage network, are always supplied in mesh networks from two or more sides and from two or more feed points.

Mesh networks require a complex power system protection and facilities such as the distance relays to errors to not only recognize, but also the fault location in the network determine. In normal operation, the power flows from the generators such as power plants to the consumers on the various individual connecting lines in the mesh network must be kept within the respective maximum permissible load limits, in addition to observing the N-1 rule .

Load flow control

The power flows of the individual lines are controlled in mesh networks by influencing the node voltage, which can be influenced by the reactive power flows independently of the active power . This possibility only exists with electrical power networks that are operated with alternating voltage. For reasons of efficiency, three-phase alternating voltage is usually selected in the context of three-phase high-voltage transmission . With direct voltage, as is the case with high-voltage direct current transmission (HVDC), there is no reactive power available, which is why HVDC systems are only used for direct end point connections and cannot form spatially extensive mesh networks.

The individual node alternating voltages in a mesh network can on the one hand be regulated directly via power plants, on the other hand influenced indirectly by controlling the reactive power flows in substations . The following methods are available in the power grid:

• in power stations directly at the synchronous generators by changing the magnetic excitation
• Step switches for power transformers that can be switched without interruption under load , also known as series regulation
• Use of phase shifting transformers on individual lines, also known as cross regulation
• Free-running synchronous generators that are operated with variable excitation without mechanical load and are installed as rotating phase shifter at selected nodes - usually larger substations
• Power electronics systems such as the Flexible AC Transmission System (FACTS)
• Static reactive power compensation by means of series and parallel reactors and capacitor banks in shunt or series connection.

As part of the medium-voltage directive , smaller and decentralized generating systems such as wind turbines must also be able to feed inductive or capacitive reactive power into the network to a certain extent at the request of the network operator - this is technically implemented using appropriate inverters with data interfaces for remote control.

literature

• Adolf J. Schwab: electrical energy systems . Generation, transport, transmission and distribution of electrical energy. 2nd Edition. Springer, 2009, ISBN 978-3-540-92226-1 .