Section 1.5 Structures of electricity supply grids Flashcards
Usual voltage in Germany for HV
- Extra high voltage = 380KV Nominal, 420 KV max
- High Voltage = 110KV Nominal, 123KV max
Usual voltage in Germany for MV
- 20 KV Nominal, 24KV Max
- 10 KV Nominal, 12KV Max
Usual voltage in Germany for LV
- 230V / 400V
What is the N1 criterion
The grid structure has to ensure security of supply
- Supply must not be interrupted if one failure occurs
- Only if a second failure occurs at the same time, a supply interruption can occur
Low Voltage Grids Structures
- The largest part of the consumers are connected to LV
- Connected to MV grids via substations
- Usually realized as four - wire system - for single-phase loads
Radial Systems
- Preferred for low load density areas
- Large loads can lead to problematic voltage drops
- Single failures can lead to interruption of several consumers
Solutions for ensuring N-1
- Connecting to neighboring grids
- Mobile back up generators
Loops Systems
- For higher-load density areas, cables are usually next to streets
- Both sides are used, and form loops
Branched Loops and Meshed networks
Security of supply increases with more in-feeds and increasing degree of meshing
- Intermediate form: Branched Loop
- Many in-feeds and meshes form a meshed network
- Disadvantage: Difficult supply restoration after blackout
Medium-Voltage Grids Structures
Fed by High Voltage Grids via transformer substations ( 20 - 50 MVA)
- Serves for energy distribution; only few direct load connections
- MV structures are loops operated as radial systems, or branched loops
- If one line fails, supply is secured by closing the loop and just disconnecting the failed line segment
- If one substation fails, only consumers directly served are affected
- Voltage depends on load density
- Rural areas: 20kv, underground cable or overhead lines
- Cities: Usually 10KV underground cables
High/Highest Voltage Grid Structures
Large power plants mainly feed into the HV grid at 380 KV
- Energy is fed into the 110KV grid
- 380/110KV transformers operated at 100-300MVA
- Very reliable
- Lines are redundant
- Intensive maintenance
- High degree of automation
in grid operation
- Probability of failure is low
Who operates the Transmission Systems?
Transmission System Operators TSOs
- Each TSO operates one control area
- Four German TSOs: Tennet, 50 Herzt Transmission, Amprion, TransnetBW
Distribution System Operators (DSOs)
900 Distributions System Operators operate at the 0.4 - 100kv grids in Germany
Control Areas for Transmission Systems
5 Control Areas:
- RG Continental Europe (UCTE)
- RG Nordic
- RG Great Britain
- RG Ireland
- RG Baltic
Common rules for transmission systems required defined by ENTSO-E in Europe
