HomeRegional NewsAfricaTechnical aspects to planning and designing LV distribution networks

Technical aspects to planning and designing LV distribution networks

Smart grids are all the rage but for the most part, authorities are concerned with building in redundancies and reducing losses. Using the Kenyan low voltage (LV) network as an example, the following checklist will endeavour to make for easier planning and safer designs.

This article first appeared in ESI Africa Issue 4-2019.
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In 2018, the Kenyan government launched the Kenya National Electrification Strategy (KNES) in partnership with the World Bank, to provide a roadmap to achieving universal access to electricity for all Kenyans by 2022. Under the government’s Vision 2030, universal access to electricity is key to meeting Kenya’s development goals and delivering on its Big Four Agenda priorities: namely affordable housing, manufacturing, food security, and universal healthcare. Furthermore, to ensure that electrification strategies are effectively achieved, there is need to build a stronger and more flexible grid by building in redundancies and reducing losses.

Engineer Joseph Oketch, the Director: Electricity and Renewable Energy Directorate at the Energy and Petroleum Regulatory Authority (EPRA), stresses: “There are two types of losses to be aware of. Firstly, technical losses due to distribution distance, size of conductor, and quality of distribution infrastructure; and secondly, commercial losses due to unmetered power supply, resulting from vandalism and theft.”

Kenya National Distribution Grid Code (KNDC)

The grid code defines the rules and regulations for various users for accessing and using the distribution network and operation systems. The objective of the KNDC is to improve the ability of Kenya’s power system to be planned and operated safely, reliably, efficiently, and economically in a transparent and non-discriminatory manner. It establishes the obligations for all distribution network service providers (DNSP) and distribution network users (DNU) of the distribution system (see Info Box above) for accessing and using the distribution system.

Low voltage (LV) distribution network

A low-voltage network or secondary network is a part of electric power distribution, which carries electric energy from distribution transformers to electricity meters of end customers. This network may include domestic and light industrial and commercial consumers. Low voltage lines start from LV bushings of transformers, to distribution lines to customers’ service drop-in lines, and several aspects are taken into consideration during their planning and designing.

Key planning and design considerations

All low voltage distribution networks, whether owned by government or the private sector, are developed in accordance with the Kenya National Distribution Grid Code. In this case, all network service providers are required to plan, design, maintain and operate their distribution networks to allow the transfer of power from generators to consumers with all facilities or equipment associated with the power system in service.

Distribution network users can seek a connection of a generating plant to the distribution system or a new or modified connection of the distribution system. The network service provider will therefore furnish the network user with the relevant distribution system specifications and requirements to assist them in planning and procurement of equipment for a new or modified connection to the distribution system.

Reviewing the connection capacity requirements: Small, medium and large

Small connections (10kVA and below)

• Connection capacity in kVA.

• Type and electrical loading of equipment to be connected, e.g. number and size of motors, cookers, electrical space and water electrical heating, air conditioning, or refrigeration.

• The date when the new or modified connection is required.

Medium connections (up to 2MVA)

• Expected connection point to the distributions; geographical and electrical.

• The date when connection is required.

• Single line diagrams of existing and proposed arrangements of main plant and apparatus showing the equipment rating and operating parameters.

• Type and electrical loading of equipment to be connected, e.g. number and size of motors, electrical heating, air conditioning, or refrigeration.

Large connections (greater than 2MVA)

• The load data.

• Type of load and control arrangements (e.g. controlled rectifier or large motor drives and type of starter employed).

• Maximum load on each phase at the time of Peak Demand.

• Demand profiles (48 x half hour average estimates) for Active and Reactive Power Demand for the day of Distribution System Peak Demand and for the day of the Transmission System Peak Demand.

Studies, assessments and stakeholder engagement requirements

(a) Distribution Impact Studies

To evaluate the impact of the proposed connection or modification to an existing connection on the Distribution System, after which the connection will be approved and a connection agreement reached.

(b) Load Assessment

To ascertain the load requirements for consumers.

(c) Survey of the Power Point

To determine the distance from the nearest transformer. If the distance is more than 600 metres an upgrade to high voltage and new transformers is required.

(d) Cost-Benefit Analysis

Analysis of constructing the network, including the commercial and social feasibility of the project.

(e) Environmental and Social Impact Assessment

This is a key requirement from the National Environment Management

Authority (NEMA), to assess and mitigate any environmental and social risks and impacts.

(f) Stakeholder Engagement

This is conducted at the county and community levels, to understand existing plans to electrify the area, reserve government land to be utilised as well as way leaves to be negotiated.

Safety requirements

• Height of the cables from the ground.

• Depth of cables.

• Distance from houses.

• Insulation coordination and lightning protection [Ed: see page 22 for more on lightning protection].

• Earthing details.

Network design requirements

• Design at the connection point.

• Physical layout adjacent to the connection point.

• Primary protection and backup protection.

• Control characteristics.

• Communications and alarms.

• Fault levels and fault clearance times.

• Switching and isolation facilities and procedures.

• Metering installations.

End-user connection requirements

• A single line diagram with the protection details.

• Metering system design details for any metering equipment being provided by the consumer.

• A general arrangement locating all the equipment on site.

• A general arrangement for each new or altered substation showing all exits and the position of all electrical equipment.

• Test certificates for all new switchgear and transformers, including measurement transformers to be used for metering purposes.

• The proposed methods of earthing cables and other equipment to comply with applicable regulatory instruments.

• Plant and earth grid test certificates from approved test authorities.

• A secondary injection and trip test certificate on all circuit breakers.

• Certification that all new equipment has been inspected before being connected to the supply.

• Operational arrangements.

Challenges implementing LV networks

• Acquisition of wayleaves can be tedious and expensive in cases where there is no government land reserve.

• Longer distance from existing transformers means additional investments in upgrading system to a high voltage (HV) level and new transformers.

• High losses can be experienced during distribution, in cases of poor distribution infrastructure or longer distribution distances, and due to unmetered supply.

• Areas with low load requirements are prevalent, making it commercially unviable.

• LV infrastructure and assets are easily vandalised.

• Underground lines can be easily damaged and pose a safety threat.

• Illegal connections due to ease of manipulating LV networks at consumer points.

The World Bank has supported Kenya’s flagship Last Mile Connectivity Programme and its Slum Electrification Programme, which have contributed to the phenomenal expansion of electricity access in the country in the last five years. According to Lucio Monari, director for energy and energy extractives at the World Bank, the Kenyan experience provides valuable lessons for other African countries in terms of the government’s commitment, incentive policies and regulation in efforts to expand and improve access to electricity. ESI

About the author
Jacinta Murunga is an energy and social sustainability professional, as well as a freelance researcher and writer on energy and social issues. Jacinta is passionate about social sustainability, environmental and social safeguards and is driven to make a difference using her 10 years’ experience, assisting communities, and private and public institutions to attain sustainability and E&S compliance respectively.

• Kenya National Distribution Grid Code of 2017
• Kenya Launches Ambitious Plan to Provide Electricity to all Citizens by 2022, World Bank, December 2018
• Kenya Charts Path to Achieving Universal Access to Electricity, World Bank, December 2018

Guest Contributor
The views expressed in this article by the author are not necessarily those of the publishers and/or association partners. While every effort is made to ensure accuracy, the publisher and editors cannot be held responsible for any inaccurate information supplied and/or published.