Answer by Dale Blundell (Atkins)
Cogeneration systems are normally connected in parallel with the local distribution network or ‘grid’, enabling seamless importing and exporting of power to or from the site. The DNO (Distribution Network Operator) will therefore need to understand:
- What protection systems are to be employed to ensure that the new generating plant does not have any adverse impact on the network fault levels and fault protection, and the speed and method of disconnection from the grid following an unexpected event.
- How the generated electricity will be synchronised to the network voltage and frequency. In support of this, the DNO may wish to conduct technical studies to fully establish protection and grid capacity requirements. The costs of any required upgrades can be sufficient to make the proposed system unattractive.
- If there is to be regular and/or substantial export, there is usually a requirement to obtain permission from the DNO.
- Protection systems need to ensure that if there is an electrical fault on the grid, the engine is isolated to prevent it feeding power into the fault.
In most cases, the installation of CHP systems requires permission from the local planning authority before a scheme can go ahead. This may involve obtaining permission to locate an external container on site or build a dedicated engine house. Permission may also be required to route services externally, or to close a road to allow a crane to lift plant onto a rooftop.
Obtaining planning permission is not guaranteed. Failure to obtain the relevant authority to proceed would put a complete block on the project – and so it is important to engage with the local planning authority at an early stage and to ensure permissions are obtained before investing in detailed technical design work.