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Top1. Introduction
Home appliance and industrial devices contain more electronic components along with the technological developments. These devices distort the quality of energy and theyalso become more sensitive to this change in quality. Before 20th century, electrical energy has been mostly used by electricalmotors, lighting systems and heating devices. The impact of these usages to fundamental frequency was so little. The rise and fall of current value are proportional to voltage in these kinds of linear loads. Some industries have started to use rectifier and power supplies to improve efficiency in recent years. The form of sine wave has been disordered because of unpropotional current and voltage. This kind of loads is called non-linear loads. The increasing usage of these non-linear loads has emerged many problems. Consequently, international standards have been determined with the concept of energy quality. Quality of electrical energy is defined by availability of nominal values on voltage amplitude and frequency in a power system with proper sine waveform. Following current, voltage and frequency parameters have been examined to determine whether the quality of energy is appropriate to international standards or not.
Parameters:
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Current-Voltage Harmonics;
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Voltage sags and swells;
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Transient;
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Flicker;
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Potential difference between neutral and earth;
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Current and voltage imbalance between phases;
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Frequency changes;
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K factor.
The wave form of current and voltage is requested in the full sinusoidal form infacilities powered by alternative current. This is only ensured when a linear load is being powered by a sinusoidal source. However, increasing usage of non-linear loads such as converters, arc furnaces and power electronics components cause non-linear current-voltage characteristic which distorts the sinusoidal form of current and voltage. This is called harmonic decomposition which means there are different frequency values in the electrical distribution system other than the base system frequency (Dugan et al., 2002). During production, transmission and distribution of electrical energy, current and voltage should be sinusoidal oscillating at 50Hz frequency. This condition is one of the main factors that determine the quality of electrical energy. However, due to the effects of non-linear elements voltage and currents move away from its sinusoidal form. Harmonic signals generated by non-linear loads cause harmonic voltages in the system. Thus, linear loads which do not produce harmonic may be exposed to harmonic pollution as well (IEEE, 2003). These non-sinusoidal wave forms are periodic and they are sum of different sinusoidal waves which has different frequencies and amplitudes. These sinusoidal waves other than the fundamental signal are called “harmonics” (Figure 1) (Zhang at all, 2010).
The basic harmonic components of a half period are shown in Figure 1 (Adak, 2006). Figure 1 shows only odd harmonics such as 3, 5, 7 and 11 present in power systems because of the symmetry of the sinusoidal wave so even harmonics do not exist. Harmonics are generally token place when a nonlinear elements ornon-sinusoidal source exist in the system individually or both. The presence of harmonic current and voltage means distortion of sine wave in power systems (ABS GuidanceNotes, 2006).