A principle of selecting Isolation Voltage for PV Systems

In this episode, we refer to several factors of selecting isolation voltage for solar application.

There are many isolated power converters in the PV system. Since PV system is normally experiencing higher impulse voltage and working under poor environment, it’s necessary to use power supplies with higher insulation. The insulation of an isolated power supply depends on Overvoltage, pollution degree and System Voltage.

For Overvoltage, the operating environment of mains-powered equipment is divided into four overvoltage category (OVC) areas according to the level of surge protection. For example, OVC IV is suitable for PV systems connected to the input power source.

Secondly, pollution degree is classified according to the amount of dust and other pollutants present in the environment.

Finally, the open circuit voltage of solar panel equals the system voltage. We need to use the system voltage of the next higher level to determine the withstand voltage.

These are three important factors which affect the required creepage and clearance distances to ensure product safety.

The insulation between two conductors shall be designed according to the following:

a) Clearance is determined by impulse voltages and overvoltage;

b) Creepage is determined by working voltage and pollution degree. For reinforced insulation, the creepage distance needs to be doubled.

CTC is dedicated to provide power converters with different isolation voltages to meet the requirements of PV systems.

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