title: "EREP 130: Application Guide for EREC P2 Security of Supply" type: wiki last_updated: 2026-04-13 primary_source: /Users/robertboswall/knowledge/sources/energy-networks/ena-erep-130.md tags: [erec-p2, security-of-supply, f-factors, distributed-generation, dsr, electricity-storage, dno]
EREP 130: Application Guide for EREC P2 Security of Supply
ENA Engineering Report 130, Issue 3 (August 2019) Companion guidance to EREC P2 Issue 7. Tells DNOs how to carry out the P2 security assessment in practice.
What it does
EREC P2 sets the standard. EREP 130 tells you how to apply it.
It covers four questions for any section of DNO network:
- What is the Group Demand to be secured (and what P2 supply class does it fall into)?
- Can network assets (intrinsic capacity plus Transfer Capacity) secure it?
- Can Contracted DG/DSR Schemes/ES make up any shortfall?
- Can Non-Contracted DG/DSR Schemes/ES make up any further shortfall?
If the answer is still no, the DNO must consider reinforcement, seek contracts, or apply for a timebound derogation from Ofgem.
Key concepts
Group Demand
Not just what the meters say. Group Demand = Measured Demand + Latent Demand. Latent Demand is the extra demand that would materialise if DG stopped exporting, if DSR was switched off, or if ES stopped exporting/constraining import.
- If Non-Contracted DG/DSR/ES aggregate is less than 5% of Measured Demand, Latent Demand can be ignored (de-minimis).
- Cold Load Pickup (electric heating, EVs, refrigeration recovering after an outage) must also be considered where material.
Contracted vs Non-Contracted
The distinction is central to Issue 3. A Contracted contribution is backed by a bilateral agreement with the DNO specifying the amount and terms. A Non-Contracted contribution is the fortuitous output from a DG/DSR/ES that has no security obligation to the DNO.
- Contracted security contribution: use the contract terms.
- Non-Contracted DG security contribution: use F-factors from Annex D.
- Non-Contracted DSR: assume zero unless DNO has specific site data.
- Non-Contracted ES export: requires site-specific analysis (EREP 131).
F-factors
F-factors translate a generator's Declared Net Capability (DNC) into a security contribution in MW:
Security contribution = F factor (%) x DNC
F-factors are derived from Imperial College London analysis of 2013-2018 DNO export data. The values are set at mean minus one standard deviation, giving an 84.1% probability that the actual contribution meets or exceeds the calculated value.
Key F-factor values (Approach 1, Annex D):
Non-intermittent DG: - Waste: 35% (winter), 32% (summer) - Biomass: 30% (winter), 25% (summer) - Landfill gas: 28% (winter), 27% (summer)
Intermittent DG (Tm = 3 hrs): - Offshore wind: 20% (winter), 15% (summer) - Onshore wind: 15% (winter), 11% (summer) - Hydro run-of-river: 18% (winter), 7% (summer) - Solar: 0% (winter), 10% (summer)
F-factors for intermittent generation decrease as persistence (Tm) increases. Solar is always 0% in winter (demand peak is after dark). Wind farms effectively provide zero contribution for very long outages (Tm > 120 hrs).
Capping
No single DG/DSR/ES should be so large that its loss becomes the credible worst case (the FCO should always be defined by a Circuit outage, not by DG/DSR/ES loss). Where a facility exceeds the capacity of the largest Circuit, its contribution is Capped at that Circuit's capacity.
Three assessment approaches for Non-Contracted DG
- Approach 1: Lookup tables by technology type and season. Quickest; appropriate for first-pass screening.
- Approach 2: Lookup tables by technology type, season, and actual capacity factor band. More accurate for well-characterised facilities.
- Approach 3: Excel/VBA model from EREP 131. Used for bespoke analysis and Non-Contracted ES.
Mandatory obligations
- DNOs shall conduct annual security compliance reviews for all substations with Group Demand over 12 MW, aligned to the RFPR submission.
- DNOs shall apply for a timebound technical derogation from Ofgem if remedial works cannot be completed before non-compliance occurs.
- A supplementary CBA using VoLL = £17,000/MWh (default) is required if remedial options are not economically justifiable.
Relationship to other instruments
| Instrument | Relationship |
|---|---|
| EREC P2/7 | The standard EREP 130 explains how to apply |
| EREP 131 | Provides the software tool for Approach 3 (bespoke DG/ES analysis) |
| DCODE | EREP 130 approved by GB Distribution Code Review Panel; compliance with DCODE Annex 1 standards required |
| G99/G98 | DG/ES connection standards; interface protection requirements relevant to fault ride-through assessments |
| Grid Code | Group Demand at GSPs must be consistent with demand data submitted to transmission companies |
Why this matters for GB energy policy
As distributed generation and storage grow, F-factors determine how much of that capacity can count towards a DNO's security compliance without network reinforcement. Low F-factors for intermittent generation (especially wind at long persistence periods) mean DNOs cannot rely heavily on wind for security - they need either contracts, storage, or network. This is a material input to the economics of rural network hosting capacity and to how DNOs treat battery storage applications at the connection stage (see F.6.1 in EREP 130 for the new-ES-connection worked example).