供配电系统简介

供配电系统

摘要：电力系统的基本功能是向用户输送电能。lOkV配电网是连接供电电源与工业、商业及生活用电的枢纽，其网络庞大及复杂。对于所有用户都期望以最低的价格买到具有高度可靠性的电能。然而，经济性与可靠性这两个因素是互相矛盾的。要提高供电网络的可靠性就必须增加网络建设投资成本。但是，如果提高可靠性使用户停电损失的降低小于用于提高可靠性所增加的投资，那么这种建设投资就没有价值了。通过计算电网的投资和用户停电的损失，最终可找到一个平衡点，使投资和损失的综合经济性最优。

关键词：供配电，供电可靠性，无功补偿，负荷分配

1 引言

电力体制的改革引发了新一轮大规模的电力建设热潮从而极大地推动了电力技术革命,新技术新设备的开发与应用日新月异,特别是信息技术与电力技术的结合在很大程度上提高了电能质量和电力供应的可靠性.由于技术的发展又降低了电力建设的成本进而推动了电网设备的更新换代.本文就是以此为契机以国内外配电自动化中一些前沿问题为内容;以配电自动化建设为背景对当前电力系统的热点技术进行一些较深入的探讨和研究.主要完成了如下工作:

(1)提出了配电自动化建设的两个典型模式即一体化模式和分立化模式.侧重分析了分立模式下的配电自动化系统体系结构,给出了软硬件配置主站选择管理模式最佳通讯方式等是本文研究的前提和实现平台.

(2)针对配电自动化中故障测量定位与隔离以及供电恢复这一关键问题分析了线路故障中电压电流等电量的变化导出了相间短路工况下故障定位的数学描述方程并给出了方程的解以及故障情况下几个重要参数s U& s I& e I& 选择表通过对故障的自动诊断与分析得出了优化的隔离和恢复供电方案自动实现故障快速隔离与网络重构减少了用户停电范围和时间有效提高配网供电可靠性文中还给出了故障分段判断以及网络快速重构的软件流程和使用方法.

(3)状态估计是实现配电自动化中关键技术之一本文在阐述状态估计方法基础上给出了不良测量数据的识别和结构性错误的识别方法针对状态估计中数据对基于残差的坏数据检测和异常以及状态量中坏数据对状态估计的影响及存在的问题提出了状态估计中拓扑错误的一种实用化检测和辩识方法针对窃电漏计电费问题独创性提出一种通过电量突变和异常分析防止窃电的新方法并在潍坊城区配电得到验证.

(4)针对配电网负荷预测建模困难参数离散度大以及相关因素多等问题本文在分析常规负荷预测模型及方法基础上引入了气象因素日期类型社会环境影响等参数给出了基于神经网络的电力负荷预测方法实例验证了方法的正确性.

(5)针对无源滤波在抑制谐波和无功补偿方面的不足以及补偿度的不连续性本文提出了一种PWM 主电路拓朴结构和基于无功功率理论的有源滤波方案建立了基于Saber Designer 仿真平台仿真分析证明了方案的可行性同时结合配电自动化技术对配电网动态无功优化补偿和降低线损的方法进行了设计分析通过实例计算验证了其客观的经济效益.

(6)针对中国电力市场未来的发展趋势以及政府监管下的电力市场公平交易设计了一种适合我国

电力市场现状按照电价分组电量协调分组竞价的短期电力交易模式给出了基于边际电价的机组组合算法制订交易计划的数学模型以及安全经济约束等在竞争比例逐步提高的情况下能够较好地解决原有中长期合同电价和短期竞争电价的矛盾减少电厂不公平的收益差异同时也可在电力市场全网的负荷曲线上对所有电厂进行限量优化减少总的系统购电费用.

2 配电网分析

配电网是电力系统中的一个重要环节，配电网接地方式和安全运行直接关系到电力系统的安全和稳定。而接地方式的选择，是与本国国情、自然环境、设备制造和运行水平等有关的，例如，雷电的活动情况、绝缘结构的设计、对周边的干扰等因素，都会影响中性点接地方式的选择;反过来，中性点接地方式对电力系统的设计、运行、调试以及发展都有很大影响。一般在电压等级较高的系统中，绝缘费用在设备总价格中占相当大的比重，降低绝缘水平带来的经济效益很显著，通常就采用中性点直接接地的方式，而采用自动重合闸来保证供电可靠性:相反，在电压等级较低的系统中，通常都采用中性点不接地的方式来提高供电可靠性。因此，在综合考虑供电可靠性、安全因素、过电压因素、继电保护的选择、投资费用等各方面因素的情况下，来论证正确选择配电网接地方式的重要性，以及如何不断开发，利用新型接地装置来应用在配电网接地系统中是当今配电网接地方式的一个重要课题。

本文主要工作是对lOkV配电网接地方式进行研究和比较选择。分别论述各类接地方式的优缺点，主要有国内外比较常用的中性点不接地方式、中性点经消弧线圈接地方式(也称谐振接地方式)、中性点电阻接地方式、中性点直接接地方式。通过技术比较确定最优接地方式，还利用一种近几年研究开发的，应用在谐振接地方式中的自动跟踪补偿装置，再配以灵敏的小电流接地选线保护，能够有效限制电网的故障接地电弧，更有利于电网的安全运行。本文首先对配电网各类接地方式做深入的研究。全面介绍国内外几种常用的中性点接地方式的运行特性，通过技术经济比较对不同的接地方式进行综合评价，再结合不同的接地方式的发展前景得出结论，优化了的谐振接地方式表现出很大的发展潜力。

然后，本文对lOkV配电网中性点谐振接地方式的运行特性进行了研究和介绍。从限制故障接地电弧的危害出发，重点论述如何利用电流谐振原理，有效熄灭故障接地电弧等。接着，本文结合国内外科技的发展和创新成果，对谐振接地优化方式中的微机接地保护性和自动跟踪补偿装置进行全面的分析与论述，说明谐振接地优化方式在供电可靠性、人身安全、设备安全和通信干扰等方面，具有较好的运行特性，既解决了小电流接地系统接地保护的选择性，又实现了自动调谐，使此种接地方式成为配电网比较理想的中性点接地方式。本文同时还对谐振接地方式实施技术进行了研究，包括消弧线圈的参数选择、安装、调整、运行与维护等内容。

最后，本文总结了本课题研究的内容。谐振接地籍助微机技术的支持，近些年来国内外均在进行

优化，优化谐振接地技术是提高供电可靠性、保护人身安全、设备安全和电磁环境等的一项合理的重要技术手段，而谐振接地实施技术更充分发挥谐振接地方式的功能，使谐振接地方式具有更好的技术经济指标。随著电网的不断发展和丰富的实践结果表明，以谐振接地方式为代表的小电流接地方式优于其他接地方式，这是配电网的中性点接地方式发展的总趋势，在今后的配电网接地方式中应推广应用。

本论文提出的思路、方案和结论不仅对于lOkV配电网中性点接地方式选择研究、实际工程应用具有实际的参考作用，对于其他电压等级中性点接地方式选择同样具有借鉴的作用。

电力系统的基本功能是向用户输送电能。lOkV配电网是连接供电电源与工业、商业及生活用电的枢纽，其网络庞大及复杂。对于所有用户都期望以最低的价格买到具有高度可靠性的电能。然而，经济性与可靠性这两个因素是互相矛盾的。要提高供电网络的可靠性就必须增加网络建设投资成本。但是，如果提高可靠性使用户停电损失的降低小于用于提高可靠性所增加的投资，那么这种建设投资就没有价值了。通过计算电网的投资和用户停电的损失，最终可找到一个平衡点，使投资和损失的综合经济性最优。论文针对配电网各种接线模式的特点，就各种接线模式的经济性和可靠性进行了分析。

3 小结

论文首先介绍lOkV配电网各种典型的接线模式和国外几个国家的典型接线模式，然后确定配电网接线模式分析的思路，明确进行分析的必要性和重要性。再提出最优分段数计算的必要性，阐述最优分段数对经济性和可靠性的影响，然后建立最优分段数计算模型，并简单介绍各种接线模式的供电方案。而后对配电网各种接线模式的可靠性和经济性进行了计算和分析，通过计算并描绘的各种图表。并对最优分段数作了分析和讨论。文章最后对各种接线模式的经济性和可靠性进行总结，分析了各种接线模式各自的优点和缺点，其适用情况。并结合实际情况针对lOkV配电网的规划和建设提出有益的建议。为lOkV配电网的规划设计及为建成网架坚实、布局合理、管理科学、能够安全、优质、高效运行的配电网提供理论的依据和有益的指引。

Power Supply and Distribution System

ABSTRACT:

The basic function of the electric power system is to transport the electric power towards customers. The l0kV electric distribution net is a key point that connects the power supply with the electricity using on the industry, business and daily-life. For the electric power, all costumers expect to pay the lowest price for the highest reliability, but don't consider that it's self-contradictory in the co-existence of economy and reliable.To improve the reliability of the power supply network, we must increase the investment cost of the network construction.

But, if the cost that improve the reliability of the network construction, but the investment on this kind of construction would be worthless if the reducing loss is on the power-off is less than the increasing investment on improving the reliability .Thus we find out a balance point to make the most economic,between the investment and the loss by calculating the investment on power net and the loss brought from power-off.

KEYWORDS:power supply and distribution, power distribution reliability，reactive compensation, load distribution

The revolution of electric power system has brought a new big round construction,which is pushing the greater revolution of electric power technique along with the application of new technique and advanced equipment. Especially, the combination of the information technique and electric power technique, to great ex- tent, has improved reliability on electric quality and electric supply. The technical development decreases the cost on electric construction and drives innovation of electric network. On the basis of national and international advanced electric knowledge, the dissertation introduces the research hotspot for present electric power system as following.

Firstly, This dissertation introduces the building condition of distribution automation(DA), and brings forward two typical construction modes on DA construction, integrative mode and fission mode .It emphasize the DA structure under the condition of the fission mode and presents the system configuration, the main station scheme, the feeder scheme, the optimized communication scheme etc., which is for DA research reference.

Secondly, as for the (DA) trouble measurement, position, isolation and resume, This dissertation analyzes the changes of pressure and current for line problem, gets math equation by educing phase short circuit and problem position under the condition of single-phase and works out equation and several parameter s U& , s I& and e I& table on problem . It brings out optimized isolation and resume plan, realizes auto isolation and network reconstruction, reduces the power off range and time and improves the reliability of electric power supply through problem self- diagnoses and self-analysis. It also introduces software flow and use for problem

judgement and sets a model on network reconstruction and computer flow.

Thirdly, electricity system state is estimated to be one of the key techniques in DA realization. The dissertation recommends the resolvent of bad measurement data and structure mistake on the ground of describing state estimate way. It also advances a practical test and judging way on topology mistake in state estimate about bad data test and abnormity in state estimate as well as the problem and effect on bad data from state measure to state estimate .As for real time monitor and control problem, the dissertation introduces a new way to solve them by electricity break and exceptional analysis, and the way has been tested in Weifang DA.

Fourthly, about the difficulty for building the model of load forecasting, big parameter scatter limit and something concerned, the dissertation introduces some parameters, eg. weather factor, date type and social environment effect based on analysis of routine load forecasting and means. It presents the way for electricity load forecasting founded on neural network(ANN),which has been tested it’s validity by example and made to be good practical effect.

Fifthly, concerning the lack of concordant wave on preventing concordant wave and non-power compensation and non-continuity on compensation, there is a topology structure of PWM main circuit and nonpower theory on active filter the waves technique and builds flat proof on the ground of Saber Designer and proves to be practical. Meanwhile, it analyzes and designs the way of non-power need of electric network trends and decreasing line loss combined with DA, which have been tested its objective economic benefit through counting example.

Sixthly, not only do the dissertation design a way founded on the magrginal electric price fitted to our present national electric power market with regards to future trends of electric power market in China and fair trade under the government surveillance, that is group competition in short-term trade under the way of grouped price and quantity harmony, but also puts forward combination arithmetic, math model of trading plan and safty economical restriction. It can solve the original contradiction between medium and long term contract price and short term competitive price with improvement on competitive percentage and cut down the unfair income difference of electric factory, at the same time, it can optimize the electric limit for all electric factories and reduce the total purchase charge of electric power from burthen curve of whole electric market network.

The distribution network is an important link among the power system. Its neutral grounding mode and operation connects security and stability of the power system directly. At the same time, the problem about neutral grounding is associated with national conditions, natural environment, device fabrication and operation. For example, the activity situation of the

thunder and lightning, insulating structure and the peripheral interference will influence the choice of neutral grounding mode Conversely, neutral grounding mode affects design, operation, debugs and developing. Generally in the system higher in grade in the voltage, the insulating expenses account for more sizable proportion at the total price of the equipment. It is very remarkable to bring the economic benefits by reducing the insulating level. Usually such system adopt the neutral directly grounding and adopt the autoreclosing to guarantee power supply reliability. On the contrary, the system which is lower in the voltage adopts neutral none grounding to raise power supply reliability. So it is an important subject to make use of new- type earth device to apply to the distribution network under considering the situation in such factors of various fields as power supply reliability, safety factor, over-voltage factor, the choice of relay protection, investment cost, etc.

The main work of this paper is to research and choice the neutral grounding mode of the l0kV distribution network. The neutral grounding mode of the l0kV network mainly adopts none grounding, grounding by arc suppressing coil, grounding by reactance grounding and directly grounding. The best grounding mode is confirmed through the technology comparison. It can help the network run in safety and limit the earth electric arc by using auto-tracking compensate device and using the line protection with the detection of the sensitive small ground current. The paper introduces and analyzes the characteristic of all kind of grounding modes about l0kV network at first. With the comparison with technological and economy, the conclusion is drawn that the improved arc suppressing coil grounding mode shows a very big development potential.

Then, this paper researches and introduces some operation characteristics of the arc suppressing coil grounding mode of the l0kV distribution network. And then the paper put emphasis on how to extinguish the earth electric arc effectively by utilizing the resonance principle. This paper combines the development of domestic and international technology and innovative achievement, and introduces the computer earth protection and autotracking compensate device. It proves that the improved arc suppressing coil grounding mode have better operation characteristics in power supply reliability, personal security, security of equipment and interference of communication. The application of the arc suppressing coil grounding mode is also researched in this paper.

Finally, the paper summarizes this topic research. As a result of the domination of the arc suppressing coil grounding mode, it should be more popularized and applied in the distribution network in the future.The way of thinking, project and conclusions in this thesis have effect on the research to choose the neutral grounding mode not only in I0kV distribution network but also in other power system..

The basic function of the electric power system is to transport the electric power towards customers. The l0kV electric distribution net is a key point that connects the power supply with the electricity using on the industry, business and daily-life. For the electric power, all costumers expect to pay the lowest price for the highest reliability, but don't consider that it's self-contradictory in the co-existence of economy and reliable. To improve the reliability of the power supply network, we must increase the investment cost of the network con- struction But, if the cost that improve the reliability of the network construction, but the investment on this kind of construction would be worthless if the reducing loss is on the power-off is less than the increasing investment on improving the reliability .Thus we find out a balance point to make the most economic, between the investment and the loss by calculating the investment on power net and the loss brought from power-off. The thesis analyses on the economic and the reliable of the various line modes, according to the characteristics various line modes existed in the electric distribution net in foshan..

First, the thesis introduces as the different line modes in the l0kV electric distribution net and in some foreign countries. Making it clear tow to conduct analyzing on the line mode of the electric distribution net, and telling us how important and necessary that analyses are.

Second, it turns to the necessity of calculating the number of optimization subsection, elaborating how it influences on the economy and reliability. Then by building up the calculation mode of the number of optimization subsection it introduces different power supply projects on the different line modes in brief. Third, it carries on the calculation and analyses towards the reliability and economy of the different line modes of electric distribution net, describing drafts according by the calculation. Then it makes analysis and discussion on the number of optimization subsection.

At last, the article make conclusion on the economy and reliability of different line modes, as well as, its application situation. Accordion to the actual circumstance, the thesis puts forward the beneficial suggestion on the programming and construction of the l0kV electric distribution net in all areas in foshan. Providing the basic theories and beneficial guideline for the programming design of the lOkV electric distribution net and building up a solid net, reasonable layout, qualified safe and efficiently-worked electric distribution net.