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Transmission Network Outputs Methodology Consultation

RIIO-T1 Transmission Network Output Measures

Under the RIIO (Revenue = Incentives + Innovation + Outputs) regulatory model, the companies’ performance is assessed by the regulator, using a set of primary and secondary outputs.

Outputs are a fundamental element of the RIIO framework.  Primary outputs, (Safety, Reliability and Availability, Environmental Impact, Connections, Customer Satisfaction and Social Obligations) monitor each onshore Transmission Owner’s (TO) performance for the delivery of end services to consumers.  The Network Output Measures (NOMs) are binding secondary outputs which show that the TOs are providing consumers with long-term value for money through a set of early warning measures or lead indicators. These assess the underlying performance of the transmission system.

The Electricity Transmission Licence, requires that in conjunction with the other onshore Transmission Licensees (SHET and NGET) we have a Network Output Measures (NOMs) Methodology to demonstrate that we are providing consumers with long-term value for money. It provides a joint basis for measuring asset risk which is designed to direct investment in the right areas, enabling effective management of network risk.  Using a risk-based approach, the transmission companies assess their asset base and direct investment in order to control the risk those assets present to the network, to health & safety and to the environment.  

The current version of the Transmission NOMS Methodology is Version 18 and reflects in its consequence calculation the impact arising from System, Safety, Environment and Financial consequences arising from the failure of an asset.

The three transmission companies whilst implementing the Network Asset Risk Annex (NARA) of the Methodology, identified an error had been made to two equations which contribute to the overall System Consequence calculation.  Further details can be found on the consultation paper.  As System Consequence is a common section across all three transmission companies we are jointly undertaking a short consultation on the changes needed to the Methodology NARA to correct both formulae.

The consultation paper and response pro-forma can be found below: 

The consultation will close on 21st September 2020 at 5pm.

Responses should be sent to: 




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