Государственное Образовательное Учреждение

Высшего Профессионального Образования

"Норильский Индустриальный Институт"

РЕФЕРАТ

по английскому языку:

"Анализ проблем оценки качества электроэнергии"

Выполнил:

Прохоров А.Л.

Проверил:

Смирнова А.Т.

Норильск, 2010.

TABLE OF CONTENTS

Introduction

1. Analysis of power quality problems

2. Different kinds of disturbances

2.1 Frequency variations

2.2 Voltage amplitude variations

2.3 Voltage fluctuations

2.4 Flicker

2.5 Voltage dips – short interruptions

2.6 Waveform variation

2.7 Interharmonics

2.8 Unbalance

3. Conclusions

4. My research

ОГЛАВЛЕНИЕ

Введение

5. Анализ проблем электроснабжения

6. Различные виды искажений

6.1 Изменение частоты

6.2 Изменение амплитуды

6.3 Флуктуации напряжения

6.4 Доза фликера

6.5 Просадки напряжения

6.6 Изменение формы волны

6.7 Некратные гармоники

6.8 Асимметрия напряжений

7. Заключение

8. Список литературы

Introduction

In recent years power quality issues have captured the attention of many researchers, energy suppliers and customers. The problem of controlling power quality is becoming more relevant because of the widespread use of non-linear and time-varying single-phase or three-phase loads that increasingly affect the operation of distribution networks in residential, commercial and industrial areas. Power quality deterioration is due to transient disturbances (voltage sags, voltage swells, impulses, etc.) and steady-state disturbances (harmonic distortion, unbalance, flicker). The main causes of such disturbances as well as the detrimental effects they have on the electrical systems are described. Among these issues, harmonics are investigated more accurately in this article. Some definitions relevant to non-sinusoidal systems are provided in order to deeply understand the solutions proposed in the remainder. A topic several researchers are interested in is that non-linear loads should not be considered the only cause of the detrimental effects related to power systems. The responsibility for the power quality deterioration should be shared between the supplier and the customer. This kind of information could be provided by indices in a straightforward and simple way. The traditional indices used by the international standards cannot satisfy these specifications. To this purpose, a new index to evaluate the above-mentioned harmonic distortion phenomena in the supply electrical networks is more deeply discussed.

1. Analysis of Power Quality problems

Electricity is an essential aspect of today’s society. That is why such a valuable product rules the majority of the political and strategic choices. Moreover, the industrial and economical development of a country has to be sustained by an adequate amount of electricity produced. To some extent, electricity is the "first" product to be produced. Notwithstanding, over the last few years, the analysis of operation of the electrical systems has proved that the electrical energy should not be considered in terms of "quantity" alone. The "quality" of the supply is a serious issue to be addressed as well (Dugan et al., 1996; Arrillaga et al., 2000). In fact, like other industrial products, electrical energy is required to meet some quality requirements: the reliability of the supply must be known in terms of the continuity of service and the parameters to be kept within some specified standards. On the other hand, unlike other products, electrical energy can undergo a lot of changes starting from where it is produced to the point where it is delivered. In fact, it is generated far from the point of use, is fed to the grid by a variety of generators and arrives to the point of use via several transformers and through many kilometers of overhead and underground cabling. Additionally, networks are managed and maintained by a number of different suppliers. Therefore, it is evident that the quality of the delivered electrical energy is not an easy task to be accomplished. The situation is even more complicated if we consider that there is a lack of exhaustive statistical data on the quality of power the customer can access. In fact, in most of the cases, customers complain about the bad quality of supply causing expensive interruption of the production processes. On the other side, electricity suppliers argue that critical customers have to be directly involved in the hard task of ensuring the quality of power. The supplier should not be expected to deliver high-quality energy to every customer anytime and anywhere on the network. All this would mean huge costs to strengthen the network that only a few customers (in numerical, not consumption, terms) could take advantage of. In fact, there are some aspects that cannot be kept under control by the provider such as weather conditions causing damages and the characteristics of the customer loads which can be responsible for power quality deterioration phenomena. Therefore, the customer should co-operate in guaranteeing a high-quality electrical power flowing through the network.

So, what should we mean by the term "power quality" and what aim should be pursued by all the subjects involved in this matter? An ideal power supply would be the one that is always available, always within voltage and frequency tolerances, and has a pure noise free sinusoidal wave shape. ............