Archive for the ‘G75’ Category

TECHNICAL – Electrical Supply Standards and Other Documents

Wednesday, May 20th, 2009

Standards and Other Documents

Electricity Safety, Quality and Continuity Regulations (ESQCR)
The Electricity Safety, Quality and Continuity Regulations 2002 – Statutory Instrument Number 2665 -HMSO ISBN 0-11-042920-6 abbreviated to ESQCR in this document.
[Available FoC on DTI web site:]

BS EN 50160 Voltage characteristics of electricity supplied by public distribution systems

BS 7671: 2001 Requirements for Electrical Installations IEE Wiring Regulations 17th Edition.

Distribution Codes
a) The Distribution Code of the DNOs of Great Britain

[Available FoC on Distribution Code website]

b) The Distribution Code for Northern Ireland

Grid Codes

a) The Grid Code for England and Wales
b) The Grid Code for Scotland
c) The Grid Code for Northern Ireland

Engineering Recommendation G5/4-1 (2001)
Planning levels for harmonic voltage distortion and the connection of nonlinear equipment to transmission and distribution networks in the United Kingdom.

Engineering Recommendation G12/3

Requirements for the application of protective multiple earthing to low voltage

Engineering Recommendation G59/1, Amendment 1 (1995)
Recommendations for the Connection of Embedded Generating Plant to the Regional Electricity Companies’ Distribution Systems.

Engineering Recommendation G74
Procedures to meet the requirements of IEC 909 for the calculation of short circuit currents in three phase AC power systems.

Engineering Recommendation G75/1, (2002)
Recommendations for the connection embedded generation plant to public distribution networks above 20kV or with outputs over 5MW.

Engineering Recommendation G83/1-1 (2003)
Recommendations for the connection of small-scale embedded generators (up to 16A per phase) in parallel with public low-voltage distribution networks.

Engineering Recommendation P2/6
Security of Supply

Distribution planning standards of voltage and of security of supply. (Parts of
Scottish Hydro Electric Power Distribution Ltd Area)

Engineering Recommendation P14
Preferred switchgear ratings.

Engineering Recommendation P24
AC traction supplies to British Rail.

Engineering Recommendation P25
The short circuit characteristics of electricity boards low voltage distribution
networks and the co-ordination of overcurrent protective devices on 230V single phase supplies up to 100A.

Engineering Recommendation P26/1
The estimation of the maximum prospective short circuit current for three phase 415V supplies.Engineering Recommendation P28 (1989)
Planning limits for voltage fluctuations caused by industrial, commercial and domestic equipment in the United Kingdom.

Engineering Recommendation P29 (1990)
Planning limits for voltage unbalance in the UK for 132 kV and below.

Electricity Association Engineering Recommendation S34 (1986)
A guide for assessing the rise of earth potential at substation sites, 1986.

Electricity Association Technical Specification (EA TS) 41-24 November 2009
Guidelines for the design, installation, testing and maintenance of main earthing systems in substations,.

Engineering Technical Report No. 113, Revision 1 (1995)
Notes of Guidance for the Protection of Embedded Generating Plant up to 5 MW for Operation in Parallel with Public Electricity Suppliers’ distribution systems.

All Engineering Recommendations are available from:

Energy Networks Association
18 Stanhope Place
Marble Arch
W2 2HH
Tel: 0207 706 5100
Fax: 0207 706 5101

Electrical Grid Connected Generation & DNO’s

Wednesday, May 20th, 2009

Grid Connected Generation

Terminology to Start

• Developer

– You!

• Distribution Network Owner/Operator (DNO)

– Owns, maintains, develops and operates the physical network
– SP Manweb, United Utilities in the North West
– Not the slightest bit interested in selling or buying energy from you

• Electricity Supplier

– Party to contract with to buy & sell energy
– Npower, PowerGen, Scottish Power, British Gas, etc…
– Not the slightest bit interested in the physical connection

• Ofgem

– Electricity and Gas Market regulator
– Also administers the ROC process if your technology is eligible

Just Some of the Legal Issues

• If grid connected, then it is a legal requirement to have permission to connect & operate any form of generation

– Needs to have a DNO connection agreement
– Needs to have correct electrical protection
– Needs to have correct earthing
– Needs to have an export meter (if exporting)
– Needs to have a supplier contract (if exporting)

• D-code : Distribution Code for UK Distribution Networks

• G-code : Grid Code for UK Transmission Networks

• Electricity at Work Regulations

Engineering Recommendations

• Technical connection requirements are detailed in the Engineering Recommendations

– DNOs view these as “Rules” rather than just “Recommendations”

• G83: Less than 6kW (16A/phase)

– No connection agreement required but must notify DNO once on

• G59: Less than 5MW and less than 20kV connection

– Must have a connection agreement

• G75: Anything else up to 50MW or transmission connected

– Must have a connection agreement

DNO Responsibilities

• Statutory obligations under the terms of their licence

– Secure operation and development of the network
– Safe & reliable operation of the network
– Ensure fair and equal access to the network
– Least cost options for connection
– Lifetime of network not just your connection

• Must respond to a connection application within 90 days. Remember, they’re not out to get you, but they have responsibilities too!

 Electrical Connection Issues

• Technical issues to be considered during connection study/investigation

– Thermal limits
– Voltage limits & step change
– Reverse power-flows through transformers
– Short-circuit rating of switchgear
– Protection arrangements & co-ordination
– Harmonics & Power Quality
– Transient stability (usually only for larger generators)

• Energy Metering

• There will be the need to provide a reasonable level of data on the generator and the site connections

• The connection and protection will need to be witnessed and approved by the DNO in order to complete the connection process

 Network Capacity Issues

• The Distribution Network has real limits

• Due to load growth and the drive towards maximising use of existing assets, available headroom is often quite limited

– Cable ratings reached during peak load
– Voltage drop/rise reached
– Circuit breaker short-circuit limits reached

• The Capacity Race

– It is not just fiction it is unfortunately real in some locations
– First-come, first-served & Interactive Applications
– There are some solutions but most do add cost and complexity

 Rule of Thumb Connection Capacities

< 6kW 240V
< 1MW 415V (3-phase)
< 1-10MW 11kV
< 30MW 33kV
< 50MW 66kV/132kV
> 50MW 132kV upwards & National Grid interfaces…

As with any project, the bigger the project, it is important that you have the right level of advice or expertise to de-risk the project.

 So, what do I do to get connected?

• Contact your friendly neighbourhood consultant ☺

But seriously:

• Start with a rough idea of what you want to do

– Check that your site can fit it and you can afford it
– Check that all other regulatory issues are okay

• Have an informal “chat” about connection possibilities with DNO generator connections or knowledgeable person

– Check that your initial idea still sounds sensible

 When contacting the DNO

• Contact DNO – generation connections (NOT Demand)

– The connection process will be more likely to be successful with good communication between the developer and the local DNO

• Determine your connection route: G83, G59 or G75
– This may have costs associated with it

• Be prepared for a process not just rubber stamping

– Planning & Information phase
– Detailed Design phase
– Installation phase
– Testing & Commissioning phase

 Working with the DNO

• Seek an early meeting to discuss your project

– Outline the scheme
– Discuss the DNO’s process for connections
– Request an indicative connection design and budgetary cost estimate with a split between contestable & non-contestable works

• Review your project

– Submit the formal connection application
– Remember to accept the connection offer!

• Submission of data to DNO

– Make sure that this is appropriate and timely to avoid delays

• Testing and Commissioning

– Plan in advance to avoid delays as staff will usually be quite busy

 Connection Charges

• Application Fees

– These vary between DNO and size and voltage level of project
– Complex projects may involve additional fees

• Connection Assets

– Developer will be expected to pay full costs for all sole-use assets

• Generation Use of System Charges

– Site dependent & in lieu of network reinforcement costs
– Each DNO has own policy in-line with Ofgem guidance

Competition in Connections

• Developer as two options:

– Get the DNO to do all works necessary for the connection
– 3rd party to provide all contestable works which DNO then adopts

• Contestable Works

– Supply & installation of any new assets up to the point of connection to the existing network. Adoption agreement required.

• Non-Contestable Works

– Any studies, reinforcement or installation on existing network
– Design & specification of any new assets, consents & way-leaves

• Note: The DNO will not get involved in any “on-site” works

 Finally, just when you thought it was too easy

Other non-electrical issues still need to be resolved

– Planning Permission?
– EIA, Emissions?
– Health & Safety?
– Commercial?
– Installation & transport?
– CDM?