There are two main types of Gas Supply Emergency
A local Gas Supply Emergency (GSE)
Local Gas Supply Emergencies are usually caused by a loss of pressure in one of the distribution networks. The local gas transporter will normally deal with the situation as the emergency doesn’t affect the national supply of gas.
A Network Gas Supply Emergency (NGSE)
This is an emergency on the National Transmission System (NTS) and is managed by the Network Emergency Co-ordinator (NEC). There are two types of national emergency:
A Gas Deficit Emergency (GDE). This happens when there’s not enough gas to meet demand and maintain a safe level of pressure. A GDE will quickly lead to large business users being told to turn off gas-using equipment.
A Critical Transport Constraint. This is when the network can’t maintain pressure at specific locations. This is usually resolved by interrupting the gas supply to local businesses only. There would also be appeals across the affected area for business and domestic users to use less gas.