In a power system, loads can be divided into two basic types: linear and non-linear. These two load types exhibit different characteristics in the relationship between current and voltage, which have different effects on the stability and efficiency of the power system.
A linear load is a load whose current is proportional to the voltage. In other words, when the voltage increases, the current also increases in the same proportion, and vice versa. This relationship is represented in a straight line and hence it is called a linear relationship. A typical example of a linear load is a purely resistive load, such as a light bulb, electric furnace, etc. When these devices are operating, the relationship between current and voltage is constant and does not change with changes in voltage or current.
Linear loads have comparatively less impact on the power system as they produce few harmonic components. Harmonics are a common problem in power systems, and they can cause problems such as voltage fluctuations, overheating of equipment, and reduced efficiency. Since the current waveform of linear loads is very close to the voltage waveform, they produce very few harmonics and have a relatively small impact on the power system.
In contrast to linear loads, the relationship between current and voltage in nonlinear loads is not linear. This means that when the voltage increases, the current does not increase in the same proportion, or the phase difference between the voltage and the current is not zero. A typical example of a nonlinear load is an electronic device such as a computer, TV, charger, etc. When these devices are operating, the relationship between current and voltage is nonlinear due to the nonlinear nature of the internal electronic components (such as diodes, transistors, etc.).
Nonlinear loads have a greater impact on the power system because they produce more harmonic components. Harmonics can cause many problems in the power system, such as equipment overheating, electromagnetic interference, energy waste, etc. Harmonics can also cause the protection device to malfunction, affecting the stability and reliability of the power system. Therefore, in order to reduce the impact of harmonics on the power system, some measures need to be taken, such as using filters, optimizing equipment design, etc.
In general, linear and nonlinear loads exhibit different characteristics in the relationship between current and voltage, which have different effects on the stability and efficiency of the power system. Understanding the differences and characteristics of these two load types helps us better understand and optimize the operation of the power system.