UK ESQCR 2002 Regulation 28: Network Characteristics and Earthing Guide

Key Takeaways

• Regulation 28 of the ESQCR 2002 mandates that electricity distributors (DNOs) provide critical network data upon request.
• This data includes the maximum prospective short circuit current (PSCC), external earth fault loop impedance (Ze), protective device ratings, and the earthing system type.
• Obtaining this formal written statement is essential for designing safe, compliant, and correctly protected solar PV and battery storage systems.
• Never make assumptions about network characteristics; incorrect data can lead to serious safety hazards and non-compliance with wiring regulations.

What is UK ESQCR 2002 Regulation 28 and why is it important for solar installations?

Regulation 28 of the Electricity Safety, Quality and Continuity Regulations 2002 (S.I. 2002/2665) obligates electricity distributors (DNOs) to provide a formal written statement of network electrical characteristics upon request. This information is vital for safely designing and connecting solar PV and battery storage systems, ensuring compliance with BS 7671. Without this data, installers risk designing systems that are inadequately protected or incorrectly earthed, posing significant safety risks.

Obtaining and Using Regulation 28 Data

The process of obtaining and correctly applying Regulation 28 data is a critical step in any solar PV or battery storage installation in the UK. This ensures your design aligns with the actual characteristics of the local electricity network.

1. Identify the Need for Data:Before designing or installing a solar PV or battery storage system, especially when submitting G98 or G99 applications, you must determine the specific network characteristics at the point of connection. This applies to Domestic Low Voltage Solar & Battery Connections (Single-Phase 230V), Three-Phase Commercial & Industrial Solar (Three-Phase 400V), and Private Substation & Microgrid Deployments. 2.Submit a Formal Request to Your DNO:As a person who can show a reasonable cause for requiring the information, such as an electrical contractor or solar PV installer, you are entitled to request this data. Contact your local Distribution Network Operator (DNO) to initiate the formal inquiry process for network characteristics. This is often part of the G98/G99 application or a separate dedicated request. 3.Receive and Review the Written Statement:The distributor shall provide a written statement detailing the required parameters. Carefully review this document. It will contain critical figures such as the maximum prospective short circuit current (PSCC) at the supply terminals and the maximum earth loop impedance (Ze) of the earth fault path outside the installation for low voltage connections. It will also specify the type and rating of the distributor's protective device or devices nearest to the supply terminals (e.g., BS 1361 / BS 88-3 cut-out fuse) and the type of earthing system applicable to the connection (e.g., TN-C-S / Protective Multiple Earthing, TN-S, or TT). 4.Incorporate Data into Design and Commissioning: Use the declared values for PSCC, Ze, protective device ratings, and earthing system type to inform your system design. This includes selecting appropriately rated AC isolators, consumer units, and ensuring correct earthing arrangements. Record the DNO declared maximum Ze and PSCC on Electrical Installation Certificates (EIC) and solar commissioning checklists. Verify that solar PV AC distribution boards have adequate kA fault ratings matching the distributor's declared prospective short-circuit current. For further guidance on PV installations, refer to our guide on /pk/guides/money/bs-7671-section-712-solar-pv-electrical-installation-guide.

Consequences of Non-Compliance and Mitigation

Key Parameters Mandated by Regulation 28

Regulation 28 of the Electricity Safety, Quality and Continuity Regulations 2002 (S.I. 2002/2665) specifies the exact information that electricity distributors must provide. This statutory instrument ensures that electrical installations, including solar PV and battery systems, can be designed and operated safely and compliantly.

The distributor shall provide, in respect of any existing or proposed consumer, a written statement of:

• Statutory Instrument: Electricity Safety, Quality and Continuity Regulations 2002 (S.I. 2002/2665).
• Regulation Reference: Regulation 28 (Information to be provided on request).
• Entitled Requestors: Any person who can show a reasonable cause for requiring the information, such as electrical contractors, solar PV installers, or EPCs.
• Mandatory Statement Form: The information must be provided as a written statement by the distributor.
• Required Parameter (a): Maximum Prospective Short Circuit Current (PSCC): This is the maximum prospective short circuit current at the supply terminals. This value is critical for selecting protective devices and switchgear with adequate breaking capacity.
• Required Parameter (b): Maximum Earth Loop Impedance (Ze): For low voltage connections, this is the maximum earth loop impedance of the earth fault path outside the installation. This value is essential for verifying automatic disconnection of supply (ADS) times in accordance with BS 7671.
• Required Parameter (c): Distributor's Protective Device Details: This includes the type and rating of the distributor's protective device or devices nearest to the supply terminals (e.g., BS 1361 / BS 88-3 cut-out fuse). This information is vital for coordinating protection within the installation.
• Required Parameter (d): Earthing System Type: The type of earthing system applicable to the connection (e.g., TN-C-S / Protective Multiple Earthing, TN-S, or TT). Understanding the earthing system is fundamental to designing a safe and compliant earthing arrangement for the solar PV system.
• Required Parameter (e): Declared Voltage, Frequency, and Permitted Variation: This includes the declared phase count, frequency, voltage, and permitted variation parameters specified in Regulation 27(1). For more details on these parameters, consult our guide on /pk/guides/money/uk-esqcr-2002-regulation-27-voltage-and-frequency-declaration-guide.

These parameters form the statutory basis for electrical contractor design and safety verification under BS 7671. Understanding the network connection consent process, which often precedes the need for Regulation 28 data, is also important; refer to /pk/guides/money/uk-domestic-solar-permitted-development-gpdo-class-a-guide for more information.

Safety: Ensuring Electrical Integrity

Adhering to Regulation 28 is a fundamental safety measure. Incorrect assumptions about network characteristics can lead to hazardous situations.

• Verify Cut-Out Fuse Ratings: Never assume cut-out fuse ratings; always verify distributor declared ratings prior to connecting large battery storage or solar inverters. This prevents overcurrent situations that could damage equipment or cause fires.
• Protective Bonding on PME Networks: On TN-C-S (PME) networks, ensure protective bonding of extraneous conductive parts complies with BS 7671 to prevent open-PEN conductor hazards. This is crucial for maintaining safety in the event of a neutral fault.
• Dedicated Earth Electrode for TT Systems: If the distributor provides a TT earthing system or cannot guarantee PME earth integrity, install a dedicated consumer earth electrode and Type S RCD. This establishes an independent earth reference for your installation, enhancing safety.

When to call a technician instead

This guide is primarily for technicians and installers. However, there are situations where further expert consultation is necessary:

• Unclear or Contradictory DNO Data: If the written statement from the DNO contains ambiguous, incomplete, or seemingly contradictory information, do not proceed with assumptions. Contact the DNO directly for clarification.
• Complex Network Configurations: For installations involving Private Substation & Microgrid Deployments or other complex network scenarios, specific DNO engineering input may be required beyond the standard Regulation 28 statement.
• Inability to Design Compliant Scheme: If, after receiving the Regulation 28 data, you are unable to design a compliant earthing or protection scheme that meets BS 7671 requirements, consult with a qualified electrical engineer specializing in grid connections.