**4. Effect of switch mode devices in power system**

The main devices in any power systems include thermal loads, electronic devices and inductive loads. Thermal loads, including the traditional lighting, can be modelled as a simple resistance. In regions where a considerable part of heating is based on electricity, heating constitutes a large share of the thermal load. Electronic devices include television and personal computer. The most common inductive appliances are cooling devices, which are air conditioning systems and refrigerators. Different values of power from 150W to 2000W are used for induction motors, depending on the application type and geographical region of use.

In this section we take a closer look to the different equipment and the effects of the harmonics on individual devices on both distribution and consumer sides. This section mainly focuses on theoretical study of the effects of the harmonics on the key performance indicators rather than practical measurements. Fig. 2 shows the fundamentals of the analysis in the rest of this section.

Fig. 7. Relation between using CFL (as a switch mode device) and the power system equipment.

### **4.1 General power system KPI**

The most important and most useful KPI of the power system include:

#### **4.1.1 Total Harmonic Distortion (THD)**

THD is defined as in equation 6:

$$THD = \frac{\sqrt{\sum\_{u=2}^{n} V\_u^2}}{V\_1} \tag{6}$$

This factor may be calculated for voltage, current or power. Current THD is normally much higher than the voltage THD for electronic devices and is more than 100%.

## **4.1.2 Crest Factor**

200 Power Quality Harmonics Analysis and Real Measurements Data

The main devices in any power systems include thermal loads, electronic devices and inductive loads. Thermal loads, including the traditional lighting, can be modelled as a simple resistance. In regions where a considerable part of heating is based on electricity, heating constitutes a large share of the thermal load. Electronic devices include television and personal computer. The most common inductive appliances are cooling devices, which are air conditioning systems and refrigerators. Different values of power from 150W to 2000W are used for induction motors, depending on the application type and geographical

In this section we take a closer look to the different equipment and the effects of the harmonics on individual devices on both distribution and consumer sides. This section mainly focuses on theoretical study of the effects of the harmonics on the key performance indicators rather than practical measurements. Fig. 2 shows the fundamentals of the analysis

Fig. 7. Relation between using CFL (as a switch mode device) and the power system

*THD*

2 2 1 *<sup>n</sup> <sup>n</sup> V*

(6)

*V*

 

The most important and most useful KPI of the power system include:

**4. Effect of switch mode devices in power system** 

region of use.

equipment.

**4.1 General power system KPI** 

THD is defined as in equation 6:

**4.1.1 Total Harmonic Distortion (THD)** 

in the rest of this section.

Crest Factor is the indicator that shows the ratio of the peak value of the wave shape to its average value in a time interval (rms)1, as shown in equation 7.

$$\mathbf{C} = \frac{\left\|\mathbf{x}\right\|\_{peak}}{\mathbf{x}\_{rms}} \tag{7}$$

This factor is especially important for the analysis of the effect on protective and control equipment such as relays.

### **4.1.3 Power Factor**

Power Factor is caused by the input rectifying capacitor of the ballast circuit. The capacitive characteristic of CFL is an advantage in systems with a high inductive load.

### **4.2 Power substation equipment**

This section studies the effect electronic devices on the substation equipments, which provide the low voltage power to the end users and can be classified to the following categories:
