肯尼亚低压配电网规划设计的技术问题 

Technical aspects to planning and designing LV distribution networks

智能电网风靡一时，但在很大程度上，当局关心的是增加冗余和减少损失。以下清单将以肯尼亚低压电网为例，力求使规划更容易，设计更安全。

本文首次出现在ESI非洲版4-2019年。

在此处阅读完整的digimag或订阅此处接收打印副本
2018年，肯尼亚政府与世界银行合作推出了《肯尼亚国家电气化战略》，为到2022年实现所有肯尼亚人普遍用电提供了路线图。根据政府的2030年愿景，普及电力是实现肯尼亚发展目标和实现其四大议程优先事项的关键：即负担得起的住房、制造业、粮食安全和全民保健。此外，为了确保电气化战略得到有效实现，需要建立一个更强大和更灵活的网格，通过建设冗余和减少损失。

能源和石油管理局（EPRA）电力和可再生能源局局长约瑟夫·奥基奇（Joseph Oketch）强调：“有两类损失需要注意。首先，由于配电距离、导线尺寸和配电基础设施质量造成的技术损失；其次，由于故意破坏和盗窃造成的未计量电源造成的商业损失。”

肯尼亚国家配电网规范（KNDC）
《电网规范》规定了各种用户接入和使用配电网及操作系统的规章制度。国家发展委员会的目标是提高肯尼亚电力系统以透明和非歧视的方式安全、可靠、高效和经济地规划和运行的能力。它规定了配电系统的所有配电网服务提供商（DNSP）和配电网用户（DNU）（见上文信息框）访问和使用配电系统的义务。
低压配电网
低压电网或二次网是配电网的一部分，它将电能从配电变压器输送到终端用户的电能表。这个网络可能包括国内和轻工业和商业消费者。低压线路从变压器的低压套管开始，到配电线路，再到用户的厂用掉电线路，在规划和设计时考虑了几个方面。
主要规划和设计考虑因素
所有低压配电网，无论是政府所有还是私营部门所有，均按照肯尼亚国家配电网规范进行开发。在这种情况下，所有网络服务提供商都必须规划、设计、维护和运行其配电网，以允许将电力从发电机转移到用户手中，同时提供与电力系统相关的所有设施或设备。
配电网用户可以寻求发电厂与配电系统的连接，或配电系统的新连接或修改连接。因此，网络服务提供商将向网络用户提供相关的配电系统规范和要求，以帮助他们规划和采购新的或修改后的配电系统连接设备。
审查连接容量要求：小型、中型和大型
小连接（10kVA及以下）
•连接容量（kVA）。
•待连接设备的类型和电气负荷，例如电机、炊具、电气空间和水电气加热、空调或制冷的数量和尺寸。
•需要新连接或修改连接的日期。
介质连接（高达2兆瓦）
•预期的配电连接点；地理和电气。
•需要连接的日期。
现有席和设备布置的单线图，显示设备额定值和操作参数。
•待连接设备的类型和电气负载，例如电机、电加热、空调或制冷的数量和尺寸。
大连接（大于2兆瓦）
•负载数据。
•负载类型和控制装置（例如，受控整流器或大型电机驱动器和所用起动器类型）。
高峰需求席上各阶段的最大负荷。
•配电系统高峰需求日和输电系统高峰需求日的有功和无功需求曲线（48 x半小时平均估计值）。
研究、评估和利益相关者参与要求
（a） 分布影响研究
评估所提出的连接或修改对配电系统上现有连接的影响，之后将批准连接并达成连接协议。
（b） 负荷评估
确定用户的负荷要求。
（c） 电源点测量
以确定距最近变压器的距离。如果距离超过600米，则需要升级到高压和新变压器。
（d） 成本效益分析
网络建设分析，包括项目的商业和社会可行性。
（e） 环境和社会影响评估
这是国家环境管理的一个关键要求
当局（NEMA），评估和减轻任何环境和社会风险和影响。
（f） 利益相关者参与
这是在县和社区层面进行的，以了解现有的计划，使该地区电气化，储备政府土地，以及使用的方式进行谈判。
安全要求
•电缆离地高度。
•电缆深度。
•与房屋的距离。
•绝缘协调和防雷[Ed:有关防雷保护的更多信息，请参见第22页]。
•接地细节。
网络设计要求
•连接点设计。
•连接点附近的物理布局。
•主保护和后备保护。
•控制特性。
•通信和警报。
•故障等级和故障清除时间。
•开关和隔离设施和程序。
•计量装置。
最终用户连接要求
•带有保护细节的单线图。
•用户提供的任何计量设备的计量系统设计细节。
•现场所有设备的总布置图。
每一个新的或变电所的总布置图显示所有出口席和所有电气设备的位置。
•所有新开关设备和变压器的试验证书，包括用于计量目的的测量变压器。
•建议的接地电缆和其他设备的方法，以符合适用的监管文书。
•经批准的测试机构出具的工厂和接地网测试证书。
•所有断路器的二次注入和跳闸试验证书。
•证明所有新设备在连接到电源之前都经过检查。
•业务安排。
实施低压网络的挑战
•在没有政府土地储备的情况下，获得通行权可能是乏味和昂贵的。
与现有变压器相比，更长的距离意味着将系统升级到高电压（HV）级和新变压器席上的额外投资。
•在配送过程中，如果配送基础设施差或配送距离较长，以及由于供应不足，可能会出现高损失。
•低负荷要求的区域普遍存在，使其在商业上不可行。
•低压基础设施和资产很容易被破坏。
•地下管线很容易损坏，并构成安全威胁。
•由于易于在消费点操纵低压网络，因此存在非法连接。
世界银行支持肯尼亚的旗舰“最后一英里连通性方案”和“贫民窟电气化方案”，这两个方案在过去五年中促进了该国电力供应的显著扩大。据世界银行能源和能源采掘主任卢西奥·莫纳里说，肯尼亚的经验为其他非洲国家提供了宝贵的经验，包括政府在努力扩大和改善电力供应方面的承诺、激励政策和监管。电喷雾
关于作者
Jacinta Murunga是能源和社会可持续发展专业人士，也是能源和社会问题的自由研究员和作家。Jacinta热衷于社会可持续性、环境和社会保障，并致力于利用她10年的经验，帮助社区、私人和公共机构分别实现可持续性和E&S合规。
工具书类
•肯尼亚2017年国家配电网规范
•肯尼亚启动雄心勃勃的计划，到2022年向所有公民提供电力，世界银行，2018年12月
•肯尼亚绘制了实现普及电力的路径图，世界银行，2018年12月

2020年非洲和中东地区电力及能源展览会：

2020年南非能源展：http://www.world-fairs.org/show-839.html

 2020年沙特电力展：  http://www.world-fairs.org/show-943.html

2020年东非肯尼亚电力展：http://www.world-fairs.org/show-938.html

2020年北非埃及电力展：http://www.world-fairs.org/show-941.html

  2020年西非尼日利亚电力展：http://www.world-fairs.org/show-944.html

原文：

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.
Read the full digimag here or subscribe to receive a print copy here

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.

References
• 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