## 1 Introduction  
Ecology is the study of environmental systems, and is not only interested in the individual components of nature, but also in how the parts interact. Industrial ecology is a discipline that has recently been developed, particularly in Europe. Industrial ecology is an interdisciplinary framework for designing and operating industrial systems as living systems interdependent from natural systems. Its aim, among others, is to follow the energy use throughout the industrial processes, in order to improve the efficiency of energy producing. Many ecological and environmental impacts are the side products of electrical power generation, delivery, and consumer systems [1]. The electrical power system can be regarded as a large network system consisting of electrical power generators, voltage transformers, connecting cables, and power consumers [2]. The environmental impact of the production and consumption of electrical energy is becoming more significant because modern society is using an increasing amount of electrical power [3]. This power is usually produced at power plants that convert some other kind of energy into electrical power: conventional, nuclear, and renewable energy sources (RES). Each system has pros and cons, but many of them may pose a threat to the environment. Additionally, the common use of electronic power converters affects the deterioration of electrical power quality. This lower quality of power places a greater burden on the environment [4]. The electrical power quality is a set of parameters describing the properties of the process of provision energy to the user under operating conditions, determining the continuity of the supply (power outage), and characterizing the supply voltage (its value and frequency, shape of waveform, and asymmetry in the multi-phase systems) [5]. The voltage waveforms in the electrical network, often thought of as composed of pure sinusoidal signals, can contain a wide variety of disturbances [6]. The main phenomena related to power quality include:  
* Harmonic and other derogations from the expected frequency of the alternating voltage,
* Voltage fluctuations, particularly those causing flickering lights,
* Voltage dips and short interruptions,
* Asymmetry within the three-phase system,
* Surges, having the characteristics of high frequency. A set of standards has been introduced to cover this field. They define the types and sizes of disturbance, and also the tolerance of various types of equipment to the possible disturbances that may be encountered. The principal standards in this field are the series of IEC 61000 [7], norms EN 50160 [8] and IEEE 1159 [9]. Electrical energy is a product, and like all other products, should meet the relevant quality requirements [10]. A proper operation of electrical equipment requires that the supply voltage only varies within a specified range around the nominal value [11,12]. The presence of disturbances in the electrical network (deterioration of the electrical power quality) is associated with a decrease in the energy production and conversion efficiency [13]. On the other hand, disturbances in the supply voltage mean that the components consuming electrical energy may reach an excessive usage level. It is important to note that the production technologies of the equipment for the generation of electrical energy from renewable sources are not fully \"green\". The RES devices also introduce some disturbances to the electrical network. To minimize the influence of these disturbances, some protectors or noise filters are used [4,14]. A proper choice of equipment can be achieved after the determination of parameters of electrical disturbances as a result of the assessment of the electrical power quality. Commercially available instruments for electrical power quality estimations also measure other parameters characterizing the power quality.