Electrical substation

A substation is a part of the electrical supply network of a power supply company and is used to connect different voltage levels. Substations exist with the power transformers always switchgear, built as outdoor switchyard or in encapsulated form gas-insulated switchgear and other equipment for measuring and control technology. Systems without transformers are also referred to as load distribution plant ( load balancer or derailleur).

Due to the high degree of automation of the operation performed in many substations, such as executing switching operation, fully automatic or remotely controlled from control centers, without operating personnel.

General

For low-loss transmission of electrical energy from the power plant to the consumer, the electrical energy is transported via multiple voltage levels. The optimum voltage level is selected according to the transmitting power and the distance. In the substation, the transformation of electrical energy between two or more voltage levels takes place. The voltage levels can be classified as follows as:

• On regional transport networks (220 kV or 400 kV and greater, or with high voltage direct current transmission ( HVDC) ). The plants are mostly outdoor installations, sometimes indoor installations.
• Regional transport networks (110 kV). Outdoor or indoor installations in cities.
• Through local distribution (30 to 60 kV), mostly indoor installations.
• On local / local distribution ( 6-20 kV) most indoor installations.

Plants that make the loop lashing destined for the final consumer low voltage are referred to as transformer stations, substations or local network stations.

Substations to supply electrically powered trains are referred to as sub-station (see also traction current ).

400 kV outdoor air system with busbars and Pantografentrennern

Substation with 110 kV side (front), transformer and much larger 400 kV side (rear)

Transformer platform in the open sea of the offshore wind farm Baltic 1

Primary equipment

In addition to the transformers necessary for the transformation are present in the substation and switchgear for the upper and lower voltage side outgoing lines. The technical equipment (transformers, busbars, etc.) and the lines are redundant, as a rule, so that in the event of a resource, the supply is still guaranteed.

Secondary technology

The term secondary systems fall the facilities of a substation, which are not involved in the loop lashing direct sense. But includes, for the operation of very important functions such as:

• Local control ( control of the individual switchgear bays on site, usually over a field control cabinet )
• Voltage control ( keeping the mains voltage at different load conditions )
• Network protection (monitoring of lines for short- circuit or ground fault shutdown with the relevant line )
• Energy metering
• Telemetry ( remote transmission of measurement data to a remote network control center )
• Remote control (remote control and monitoring by a remote network control center )
• Own needs ( secured DC and AC power supply, battery systems, rectifiers and inverters to maintain the function of the system in case of power failure or network problems)
• Ripple control system (control existing on the net consumers, load management )

Special shapes

A special form of a transformer station (UW ) is the simplified substation ( VUW ). While the most common conventional substations lines and transformers are connected to busbars, in simplified substations typically be waived on the high voltage side to busbars. The cables are only connected in this case by a circuit breaker and circuit breaker directly to the transformer. A coupling between the lines is possible. VUWs be used when only a few (2-3) lines on the high-voltage side are present and in the medium and high voltage for cost savings (elimination of the busbar and thus saving the busbar disconnectors ).

Arise from this fact also the disadvantages of VUWs: Since no bus exists as a " distributor ", would also be useless transformer connected with the failure of a line ( at VUW without coupling between the lines ). The failure of system components or wiring is complicated by offset. Also subsequent expand the plant is limited. If an additional line to be connected, is also an additional coupling (if it value is placed ) and / or an additional transformer needed. For more additional lines, the cost advantage is therefore used up quickly. In such a case is out of the VUW by incorporation of a bus bar is often a conventional substation.

At high voltage substations for several levels above 100 kV, it is sometimes required to accommodate the system to a plurality of separate areas in the immediate vicinity, which are interconnected by coupling lines. This usually includes any area the complete switchgear - usually including the transformers - for this level and is completely fenced for themselves. The line connection between the system components is usually done by overhead cables and rarely by underground cable. Examples of such shared Substations are the substation Hoheneck in Ludwigsburg and the transformer station in the district crown by Witten.

Transport links

Large Substations (highest applied voltage over 100 kV) must be accessible for heavy haulage, as large power transformers up to 500 tonnes. The access roads should not be too tight because of the size of the transformers. Some, particularly older substations for 400 kV or 220 kV also have a private siding for delivery of the transformers.

Locations

Listings of switchgear and substations can be found in the following lists:

• List of switchgear high voltage grid in Germany
• List of switchgear high voltage grid in Austria
• List of switchgear in the high voltage network in Switzerland