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Question:

Why do all connection and control cables feature two rated voltage ranges, for example U0/U 300/500 V?

Answer:

The rated voltage of a cable is the voltage on which the construction and testing of the cable is based in the context of electrical inspections. It is specified in the form of two voltage values: U0/U.
Many ÖLFLEX® connection and control cables have a rated voltage of U0/U 300/500 V.

• U0 is the rms-value (root mean square) of the voltage between a live conductor (core) and the earth (ground).
The earth can be a metallic cable sheath (copper braid) or an earthed surrounding medium such as the metal casing of a device or control cabinet.
The U0 value is lower than the U value, as there is as electrical separation only one layer of insulation between the live copper conductor and surrounding metallic medium.

• U is the rms-value of the voltage between 2 live conductors (cores) of a multicored cable or within a system of single cores.
The U value is higher than the U0 value since there are always as electrical separation two layers of insulation between two live copper conductors in a multi-core cable or between two single cores in a switch cabinet.

The electrical voltage is measured in Volt (V).