Grid Code Compliance Studies (ENA G99)

Any new generation or storage system connecting to a UK distribution network must meet the requirements of the ENA Engineering Recommendation G99. These standards ensure that embedded generation operates safely, reliably, and in harmony with the wider grid. 

Our consultants carry out Grid Code Compliance Studies to verify that your system meets the necessary technical and performance criteria — including voltage control, frequency response, fault ride-through, and protection co-ordination. This ensures safe integration, regulatory compliance, and operational reliability from initial design through to connection approval. 

When?  

G99 studies are required for all generating plants seeking connection to the distribution network, with the level of analysis depending on generator type and capacity: 

• Type A (<1 MW): Basic compliance checks. 

• Type B (1–10 MW): Studies covering Fault Ride Through (FRT), Limited Frequency Sensitivity (LFSM-O), and reactive power flow. 

• Type C/D (>10 MW or ≥110 kV): Comprehensive dynamic studies including FRT, LFSM-O/U, Frequency Sensitive Mode (FSM), and reactive power stability. 

Early engagement is key; initiating studies at the design stage helps streamline the DNO approval process and avoid costly rework or connection delays. 

Benefits 

A Grid Code Compliance Study helps you: 

• Demonstrate full compliance with ENA G99 and DNO connection requirements. 

• Verify generator control and protection performance under grid disturbances. 

• De-risk project approval and accelerate grid connection timelines. 

• Build confidence with regulators, insurers, and investors. 

• Support the safe and reliable integration of renewable generation into the UK grid. 

Looking beyond G99? 

EA Technology also provides comprehensive Power Quality Studies covering harmonics (G5/5), voltage fluctuation (P28), and unbalance (P29) to ensure your connection meets all DNO standards.