Black start
The start-up of a power plant (block) is referred to as a black start if this occurs independently of the power grid . Under black start capability is the ability of a power plant (blocks), independent of power supply starting to boot from the off state.
function
The black start capability is particularly important in the event of a widespread power failure in order to bring the energy network back into operation. Normally, the power required to start an energy generation unit is taken from the network. The energy of generating units capable of black start can then be used to start up generating units that are not capable of black start.
In contrast to hydropower plants, thermal power plants require a large amount of (electrical) energy for their own use before they can provide electrical or thermal power themselves. If a coal-fired or nuclear power plant block is provided with a black start-capable unit with sufficient power, then black-start capability can also be achieved for the entire system. Most of these are gas turbines that are put into operation in a black start using energy from accumulators or diesel generators . In every network, a sufficient number of power plants must be equipped with black start capability in order to be available for a network restart after a network breakdown.
Obstacles to thermal power plants
A major obstacle why thermal power plants are rarely black start capable is the contraction and shortening of the turbine shaft when it cools down from its operating temperature to ambient temperature. It then jams in the housing and can neither be turned nor removed; To restart the power plant, it must first be preheated so that it can rotate freely again before the hot steam can flow through it.
If a thermal power plant is switched off, the turbine shaft begins to heat up in good time so that the power plant can be put back into operation at the planned time.
Special requirements
A power plant capable of black start should have special characteristics:
- It should be able to start quickly: If the black start takes a long time, then the power plant cannot help restart a collapsed network; other power plants could help him out at the start - his black start capability is then useless.
- It must be able to work independently of external power sources: Not only the pure power generation process, but also other ancillary requirements must function independently of the network (control center, telephone and communication systems with network operator and management, substation ...). If necessary, isolated operation with a partial network is possible (supply of important consumers such as the police, hospital, fire department, THW).
- In addition, a power plant capable of black start should be able to withstand a high starting current if it was not possible to disconnect it from the grid beforehand.
- It should have a flexible start behavior.
Examples of (direct) black start capable power plants used in Germany are
- Hydropower plants and
- Compressed air storage power plants
- Combined multivalent systems ( Zolling power plant )
See also
Web links
Individual evidence
- ↑ What are black start and black start capability? Retrieved May 30, 2017 .