5. Key Revision in Amendment 1 (1990)
The most significant change introduced by Amendment 1 is the complete replacement of Table I. The new table provides a more comprehensive and structured mapping of cable and system voltages.
TABLE I: Relationship between U₀/U and (Um)
| Rated voltage of cables and accessories<br>(U₀ kV) | Nominal system voltage<br>(U kV) | Highest voltage for equipment<br>(Um kV) |
| 1,8 | 3 | 3,6 |
| 3,6 | 6 | 7,2 |
| 6 | 6 | 7,2 |
| 6 | 10 | 12 |
| 8,7 | 10 | 12 |
| 8,7 | 15 | 17,5 |
| 12 | 20 | 24 |
| 18 | 30 | 33 |
| 26 | 45 | 47 |
| 36 | 60 | 66 |
| 64 | 110 | 115 |
| 76 | 132 | 138 |
| 87 | 150 | 161 |
| 127 | 220 | 230 |
| 160 | 275 | 287 |
| 190 | 330 | 345 |
| 220 | 380 | 400 |
| 290 | 500 | |
| 420 | 700 | 750 |