About Transmission 
The Transmission system carries electricity from the point at which it is produced e.g. wind farms, gas plants, hydro plants etc, around the country on 400kV and 220kV lines. It is operated by Eirgrid - the Transmission System Operator or TSO.
Eirgrid's main purpose is to ensure that sufficient electricity continues to flow through the system to meet Ireland's demand. They control the system from the National Control Centre in Dublin. From there they can monitor all generation stations and they know how much electricity is being generated at any one time.
If a station drops off the system they can call on another to provide more electricity in order to meet demand. Demand is at its highest between approximately 6 - 8pm and at it's lowest between 3 - 5am. Eirgrid also operate the Single Electricity Market (SEM) with the System Operator of Northern Ireland (SONI). You can read more about the SEM on the 'Markets' section of this webpage.
About Distribution
The Distribution system carries the electricity on 110kV and 38kV lines into our businesses, hospitals, schools and homes. It is operated by ESB Networks - the Distribution System Operator or DSO. ESB Networks connect generators to the system as well as all businesses, hospitals, schools and homes. They are also responsible for electricity meters and it is their staff - 3,000 in total - who read our meters at various intervals throughout the year.
About System Links (Transformers)
Electricity is 'transformed' from one voltage to another at substations. Substations historically were outdoors but new technology has meant they are now smaller and indoors so less of a blight on the landscape - and safer also. For more information on these switching technologies two companies currently supplying that technology are Siemens and ABB
Methods of Grid & Network Development
There are two methods of grid and network development i.e. underground cables and overhead wires. To date the majority of Ireland's national Grid and Network has been facilitated by the use of overhead wires with associated poles, pylons and sub-stations.