Transmission and energy storage Flashcards
What is the role of transmission networks?
To transport electrical energy in bulk from generation sites to electrical substations
What is a load centre in power systems?
A place where consumers have maximum power demand
What are the main components of high-voltage AC systems?
Transmission lines, transformers, protection systems and auxiliary assets
Why is the transmission system typically built in a meshed layout?
To increase reliability and operational flexibility despite higher construction costs and more complex protection requirements
What are the main line components in a transmission line?
Resistance inductance and capacitance uniformly distributed along the entire length of the line
What causes inductance in a transmission line?
The changing flux from AC current flow creates flux linkages inducing internal and external inductance
Why does capacitance exist between overhead line conductors?
Because air acts as insulation creating capacitance between conductors
What is the corona effect in transmission lines?
It is an electrical breakdown in air causing the conductor to leak charges producing noise, vibration, power loss and ozone corrosion
What factors affect the corona effect?
- supply voltage
- conductor surface condition
- air density
- spacing between conductors
What is the skin effect in transmission lines?
It is the tendency of AC current to concentrate near the surface of a conductor reducing current density at greater depths
What causes the skin effect?
An induced magnetic field creates eddy currents that partially cancel the internal current flow making current denser near the conductor’s surface
What is the proximity effect in AC transmission lines?
It is the redistribution of current in parallel conductors caused by magnetic interactions increasing apparent resistance
How do eddy currents form due to the proximity effect?
Magnetic fields from one conductor induce eddy currents in the adjacent conductor altering current distribution
What factors affect the proximity effect?
- frequency (increases with increasing frequency)
- conductor diameter (proximity increases with increasing conductor size)
- material type (ferromagnetic increases the effect)
- conductor structure (solid vs stranded; solid increases effect)
What is conductor transposition in transmission lines?
It involves regularly swapping conductor positions to balance inductance and reduce voltage drops
What is sag in a transmission line?
It is the vertical distance between the line’s support points and its lowest point, preventing excessive tension
How do ice and wind affect transmission line sag?
Wind increases horizontal weight while ice adds vertical weight changing the conductor’s overall weight per unit length
What is the clearance of overhead lines?
It is the minimum safe distance between overhead lines and nearby objects ensuring safety
What factors influence the required clearance of overhead lines?
- voltage level
- type of surroundings (e.g. roads, water, residential areas)
- line sag (temperature factors, wind, ice)
What is energy storage capacity?
It is the maximum amount of energy that can be stored in a system
What is energy density?
It is the amount of energy stored per unit mass volume or size of a material or device
What is power density?
It is the measure of how quickly a storage system can release power expressed in W/kg or W/liter
What is a high-voltage DC (HVDC) system?
It converts generated AC into DC for transmission and then back to AC at the receiving end for distribution
