What is the voltage rating of RV K 1.8/3 kV cable and what does U₀/U mean?

The cable has a rated voltage of 1.8/3 kV, where U₀ = 1.8 kV is the power‑frequency voltage between conductor and earth or metallic screen, and U = 3 kV is the voltage between phase conductors. This rating designates it for use in low‑voltage networks where the maximum phase‑to‑earth voltage does not exceed 1.8 kV and the phase‑to‑phase voltage does not exceed 3 kV, per IEC designations.