THE CONTRIBUTION TO DISTRIBUTION NETWORK …

1 THE CONTRIBUTION TO DISTRIBUTION NETWORK FAULT LEVELS FROM THE connection OF distributed generation CONTRACT NUMBER: DG/CG/00027/00/00 URN NUMBER: 05/636 The DTI drives our ambition of prosperity for all by working to create the best environment for business success in the UK. We help people and companies become more productive by promoting enterprise, innovation and creativity. We champion UK business at home and abroad. We invest heavily in world-class science and technology. We protect the rights of working people and consumers. And we stand up for fair and open markets in the UK, Europe and the world. The CONTRIBUTION to DISTRIBUTION NETWORK Fault Levels From the connection of distributed generation DG/CG/00027/00/00 URN This work was commissioned and managed by the DTI's distributed generation Programme in support of the Technical Steering Group (TSG) of the distributed generation Co-ordinating Group (DGCG).

2 The DGCG is jointly chaired by DTI and Ofgem, and further information can be found at Contractor KEMA Limited The work described in this report was carried out under contract as part of the DTI Technology Programme: New and Renewable Energy, which is managed by Future Energy Solutions. The views and judgements expressed in this report are those of the contractor and do not necessarily reflect those of the DTI or Future Energy Solutions. First published 2005 Crown Copyright 2005 WS5 P01 Steering Group The KEMA Consulting report for the Department of Trade and Industry s New & Renewable Energy Programme on The CONTRIBUTION to DISTRIBUTION NETWORK Fault Levels from the connection of distributed generation Introduction: In support of DGCG TSG WS5, the Department of Trade and Industry s New & Renewable Energy Programme commissioned KEMA Limited to undertake an investigation and report on The CONTRIBUTION to DISTRIBUTION NETWORK Fault Levels from the connection of distributed generation .

3 The investigation was undertaken during 2004/5 and was subject to review and commentary by the TSG WS5 Project 01 Manager and other WS5 members while in progress. The final report was submitted to Future Energy Solutions (FES acting for the DTI New & Renewable Energy Programme) in April 2005. Objective: The aim of the study was to identify the likely impact that distributed generation (DG) will have on GB DISTRIBUTION NETWORK fault levels in the period to 2010, and addresses how these increased fault levels could be managed to ensure that they do not act as a barrier to the increased penetration of DG. The study also includes an overview of the likely longer term impact of new forms of generation . The study focused on two areas in particular: the circumstances and scenarios that are most likely to give rise to fault level issues that require to be addressed; and the options and likely costs for addressing these fault level issues.

4 Methodology: Three main sources of information were used: KEMA s own experience in the Netherlands (where DG penetration exceeds current levels in GB); material already published; and analysis of DNOs Long Term Development Statements. The study included some significant work to assess DISTRIBUTION NETWORK fault level headroom the extent to which fault levels can be raised before installation of replacement apparatus with higher fault level ratings becomes necessary. Findings: KEMA have reported on their findings in the context of a range of levels of penetration of DG, providing a range of estimates of the costs attributable to resolving fault level increases. KEMA have reported their view that issues arising from increases in DISTRIBUTION NETWORK fault levels will not constrain achievement of current targets for DG penetration.

5 The KEMA report also includes commentary on international experience with HV (11 kV & 33 kV) connected DG, options for managing increased fault levels, the measurement and calculation of fault levels, and a summary of the characteristics of DG machines. Next steps: TSG WS5 members have received the findings established in the KEMA report with interest. However, members are alert to the fact that changes in fault levels, arising from new DG connected to existing DISTRIBUTION networks, need to be considered in the context of other changes ( voltage control, active management, etc). Caution should be exercised in the regard given to cost estimates attributable to fault level change, given that other changes will often be the trigger for additional expenditure incurred to enable connection . NETWORK Operators and generators are encouraged to read the KEMA report, and consider its findings in the context of generator connection charging proposals.

6 Chris Mortley Manager, TSG WS5 P01 May 2005 1 Table of Contents Table of Contents ..1 Executive Summary ..3 1. Introduction ..7 Background .. 7 Aim of Study .. 8 Scope of Document .. 8 Structure of Document .. 9 References .. 9 2. Technical Review ..14 Introduction .. 14 Relationship between DG and Fault Levels .. 14 Likely Impact in the Period to 2010 .. 17 LV connected 17 International experience with LV connected DG .. 19 MV and HV connected DG .. 20 International Experience with MV and HV connected DG .. 29 3. Options for Managing Increased Fault Levels ..32 Introduction .. 32 Overview of Fault Level Management Methods .. 32 Uprating and replacement of components .. 32 Increase impedance .. 32 Is limiter .. 34 Superconducting fault current limiter .. 34 Power 34 Solid state fault current limiter .. 35 NETWORK splitting and reconfiguration.

7 35 Sequential 35 Active fault level management .. 36 Fault Level Management Costs .. 36 DG connected to MV and 37 Case Study Example .. 43 4. Measurement and Calculation of Fault Level Values ..44 Introduction .. 44 Fault Level Calculation .. 44 Fault Level Measurement .. 45 Conclusion .. 46 5. Constraints to DG Penetration due to Fault Level Limitations ..48 Introduction .. 48 LV NETWORK .. 48 MV/HV 49 6. Characteristics of DG Machines ..51 2 Introduction .. 51 DG types and their contributions .. 51 Impact on make and break currents .. 53 7. Longer term perspective (to 2020-2030) ..55 Introduction .. 55 New generation technologies .. 58 Conclusion .. 59 Appendix A: Example Netherlands DG Project ..1 3 Executive Summary This document presents KEMA s view on the impact of distributed generation on fault levels in response to a request by the DGCG TSG Workstream 5.

8 The increasing demand on Great Britain s DISTRIBUTION networks imposed by new distributed generation (such as renewable, micro CHP or CHP) will impact on the operation of the NETWORK in a number of areas including voltage levels and fault levels. In general all new distributed generation contributes some increase to fault levels, and this would in some cases result in the fault level exceeding the design limit of the NETWORK equipment to which it is connected if no action is taken to address it. This report focuses on two major areas: the circumstances and scenarios that are most likely to give rise to fault level issues that require to be addressed; and the options and likely costs for addressing these fault level issues. In examining the circumstances and scenarios most likely to give rise to fault level issues, we examine the generic structure of the GB DISTRIBUTION networks and identify the areas where the type of distributed generation likely to require connection has the greatest CONTRIBUTION to fault level relative to the fault level headroom available at that point in the NETWORK .

9 Our conclusion is that this is most likely to occur with the connection of distributed generation to urban 11 kV and 33 kV networks, and that the most likely form of distributed generation requiring connection to these networks is small, medium and large CHP, landfill gas and waste incineration. Whilst we conclude that the connection of distributed generation to urban 11 kV and 33 kV networks is most likely to result in fault level issues, there will also be instances of large-scale distributed generation connections to both rural and urban networks which provide sufficient CONTRIBUTION to fault levels to exceed the fault level headroom available at that particular location. We also examine the likely impact of the fault level issue over time, particularly in the period to 2010 but also beyond that. In so doing, we consider the development of distributed generation to date in Great Britain, taking into account the factors that have influenced development to date but are in the process of changing, such as the change to the connection charging methodologies.

10 The change from deep connection charging to shallower connection charging provides poorer locational signals than in the past, and may result in a significant increase in connection requests in areas with very low fault level headroom as the costs to the developer will now be lower than before. We also consider the situation with regards to the levels of distributed generation currently in place in comparison to the Government s targets for 2010, and the 4 potential paths towards the targets in relation to the fault level issue. In particular, we conclude that the targets in relation to CHP are unlikely to be met in the absence of a significant increase in small, medium and large CHP projects. An increase in CHP projects, which would be most likely to occur in urban areas, would lead to an increase in fault level issues as urban networks tend to have the lowest fault level headroom.