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Pittsburgh, Pennsylvania, September, 2001

A recent survey attributes that 92% of all disturbances in power system is caused by voltage sags. Three-phase voltage sag can be classified in seven types as shown in Fig.1 (Bollen MHJ, 2000). The electrical sensitive load often trips of shunts down when voltage sag occur. It's very important to know how these sensitive equipment works when the voltage sag occur. This is the reason to develop the voltage sag generator that can created varied type of voltage sag waveform. The purpose of voltage sag generator is use to test the immunity of equipment against the voltage sag.

The magnitude and angle of three phase voltage sag can calculate form equation 1 to equation 7(Bollen MHJ, 2000).

Type A

$$\begin{aligned} V\_a &= V \\ V\_b &= -\frac{1}{2}V - j\frac{1}{2}\sqrt{3}V \\ V\_c &= -\frac{1}{2}V + j\frac{1}{2}\sqrt{3}V \end{aligned} \tag{1}$$

Type B

$$\begin{aligned} V\_a &= V \\ V\_b &= -\frac{1}{2} - j\frac{1}{2}\sqrt{3} \\ V\_c &= -\frac{1}{2} + j\frac{1}{2}\sqrt{3} \end{aligned} \tag{2}$$

© 2012 Oranpiroj et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Oranpiroj et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Type C

$$\begin{aligned} V\_a &= 1\\ V\_b &= -\frac{1}{2} - j\frac{1}{2}\sqrt{3}V\\ V\_c &= -\frac{1}{2} + j\frac{1}{2}\sqrt{3}V \end{aligned} \tag{3}$$

Type D

$$\begin{aligned} V\_a &= V \\ V\_b &= -\frac{1}{2}V - j\frac{1}{2}\sqrt{3} \\ V\_c &= -\frac{1}{2}V + j\frac{1}{2}\sqrt{3} \end{aligned} \tag{4}$$

Type E

$$\begin{aligned} V\_a &= 1\\ V\_b &= -\frac{1}{2}V - j\frac{1}{2}\sqrt{3}V\\ V\_c &= -\frac{1}{2}V + j\frac{1}{2}\sqrt{3}V \end{aligned} \tag{5}$$

Type F

$$\begin{aligned} V\_a &= V \\ V\_b &= -j\frac{\sqrt{3}}{3} - \frac{1}{2}V - j\frac{\sqrt{3}}{6}V \\ V\_c &= +j\frac{\sqrt{3}}{3} - \frac{1}{2}V + j\frac{\sqrt{3}}{6}V \end{aligned} \tag{6}$$

Type G

$$\begin{aligned} V\_a &= \frac{2}{3} + \frac{1}{3}V \\ V\_b &= -\frac{1}{3} - \frac{1}{6}V - j\frac{\sqrt{3}}{2}V \\ V\_c &= -\frac{1}{3} - \frac{1}{6}V + j\frac{\sqrt{3}}{2}V \end{aligned} \tag{7}$$

#### Voltage Sag Waveform Using SagWave GUI 113

**Figure 1.** The seven type of voltage sag (Bollen MHJ, 2000).
