Switchgear

A substation is a facility that is distributed or re-clamped in the electrical energy.

General Information

Switchgear, rather its busbars, form the "nodes" of high, medium and low voltage networks. The incoming and outgoing lines in the nodes are called branches. A distinction branches for feeds, disposals and couplings to other network nodes. Because of the variety of feeders and the need for the large cable cross sections terminal compartment are the "nodes" implemented as busbars. Virtually all branches are connected via a switchgear switchgear with the network nodes.

In the switchgear, the actual current distribution and the grouping of loads and loads carried. Switchgear allow the change of the network topology at faults and the Isolating and earthing of equipment for maintenance. A distinction is low voltage, medium voltage and high voltage switchgear.

Cable gardens are also counted among the switchgear, although, if anything, have only disconnector.

Requirements for switchgear

• Ensure a safe operation
• Encapsulation, isolation and cover high voltage carrying parts ( indoors )
• Isolation and grounding possibility for maintenance
• Ease of maintenance
• Small footprint
• Long-term integrity of contact connections
• Limiting the heating current-carrying parts
• For outdoor installations, a wide -area network grounding and lightning protection devices

Low and medium voltage

Switchgear for low and medium voltage are always executed in closed buildings. While switchgear for low voltage are housed in normal rooms in closed cabinets to switchgear for medium voltage are often in appropriate control rooms in the so-called switching cells, which are connected to each other by so-called busbars. Depending on the importance these are available as single busbar equipped ( with longitudinal separation ), double busbar or even triple busbar.

The spatial arrangement of the separate busbars allows working in a cubicle in accordance with certain safety rules. It just has the cable / line, which has supplied the cell to be switched off and grounded. In interpreting a busbar or Al- Cu - rails used, which must bear the maximum permissible continuous load current; this applies to the rails to each other even as well as for screw joints and the Phasenabzweigungen to circuit breakers, circuit breakers and other equipment.

Since the aluminum stays under the effect of pressure forces produced by steel screws tend to flow, it is due to the heating during operation gradually to a deterioration of Schienenschraubverbindungen to destruction. The consistent use of friction washers Stainless steel ( Niro) keeps the rail Nena pressing forces constant by the tension pulley expands in length. The arrangement of the steel screws with overlapping rails according to VDE regulations .... regulated.

Modern medium voltage switchgear is fully encapsulated executed ie all active components such as busbars and switchgear are inaccessible during normal operation. This requires a largely maintenance-free design of the busbar connections and switchgear. When insulating media for the hermetically sealed busbar compartment comes with gas-insulated switchgear SF6 gas (prior art ) or switchgear latest design a solid insulation from various Giesharzen used. Switching devices are executed depending on the rated voltage and short circuit breaking capacity of a vacuum switching devices and also with gas insulation.

Is a great flexibility in setting up the fields required (eg number of functions per field ) so offer classic switchgear with air as the insulating medium more room in the planning and expansion. They are primarily used in industry for applications where standardized compact switchgears are reaching the limits of the possible functions. Largely maintenance-free switching devices in the design with vacuum switch as gas -insulated switchgear (GIS ) are also available for this switchgear. In new buildings and upgrading work of transformer stations, however, usually standardized compact switchgear ( RMU with one to three transformer outlets ) come with solid insulation or in GIS implementation used.

High and very high voltage

Switchgear for high and very high voltage to be built either as a switchyard or as gas-insulated switchgear. The main difference is that an insulating gas such as SF6 is used, whereby the fully enclosed switchgear can be built much more compact and smaller space.

The space requirement of gas-insulated switchgear is approximately 1/10 of that of outdoor switchgear, making these plants can be accommodated in halls. For costs and maintenance costs are higher than for outdoor switchgear, so find gas-insulated systems, especially in dense urban areas with limited space application.

Special switchgear

Special switchgear converter stations for the high- voltage direct current (HVDC ) and Bahnstromumformerwerke. Another form of special switchboards are encountered in antenna switches of large channels with switchable polar pattern. Also a special type to be the carrier frequency of signal relays, or plants for the extraction of the carrier frequency signals.

Safety

No unauthorized persons may enter any switchgear because of the risk of partially accessible high voltage components. In Germany, however, the systems with closed must, from the inside opening doors be equipped ( panic lock ). Outdoor switchgear must be surrounded by a 1.80 -meter-high fence, which is often connected to the station grounding or a separate potential control ring. The access to the areas with high voltage equipment is only appropriately trained persons.

History

Switchgear are as old as the generation of electrical energy. The first versions were very simple: all the necessary ingredients were attached to a wall. As systems are mounted later on wooden panels, one could speak for the first time of electrical panels in the strict sense. To prevent fire, the wood was replaced by slate or marble. This was accompanied by a further advance, because the switching and measuring devices could be mounted on the front, while the wiring on the back was.

While in the early days at the substation site personnel worked around the individual switching operations run manually, both switchgear and substations from central control centers were increasingly controlled remotely by means of control in the first half of the 20th century. Nowadays include switching and transformer stations to the plant with the highest degree of automation: It can be automated to some 100 substations and transformer stations from a central control station controlled and monitored remotely. Staff is only ad hoc basis, for example, for maintenance on site.