Rated insulation level

The combination of voltage values that characterizes the insulation of the equipment with regard to its capability to withstand dielectric stresses. These values are selected based on the rated voltage of the bank/system.

Standard insulation values are given for altitudes <1000 m above sea level. For higher altitudes, a correction factor must be used.

Lightning impulse test

The lightning impulse test is performed with a standardized wave shape (1.2/50 µs) for simulation of lightning overvoltage. The value is expressed in kV peak.

Rated Power Frequency Withstand Voltage

This test is to show that the apparatus can withstand the power frequency over-voltages that can occur.

The Rated Power Frequency Withstand voltage indicates the required withstand voltage. The value is expressed in kV rms.

Rated SIWL

For voltages >300 kV, the power-frequency voltage test is partly replaced by the switching impulse test. The wave shape 250/2500 µs simulates switching overvoltage.

The rated Switching Impulse Withstand Level (SIWL) indi- cates the required withstand level phase-to-earth (phase-to- ground), between phases and across open contacts.

The value is expressed in kV as a peak value.

Degree of protection

The extent of protection provided by an enclosure against access to hazardous parts, against entry of solid foreign objects and/or against entry of water and is verified by standardized test meth- ods. (IEC 60529)

IP code

A coding system to indicate the degrees of protection provided by an enclosure against access to hazardous parts, entry of solid for- eign objects, entry of water and to give additional information in connection with such protection. (IEC 60529)