| Supply type | Typical Ze (Ω) | |-------------|----------------| | TN-S | 0.2 – 0.8 | | TN-C-S (PME) | 0.35 max | | TT | 10 – 20 | Make a second table:
| MCB type | 6A | 10A | 16A | 20A | 32A | 40A | |----------|------|------|------|------|------|------| | B | 7.7 | 4.6 | 2.9 | 2.3 | 1.44 | 1.15 | | C | 3.8 | 2.3 | 1.45 | 1.15 | 0.72 | 0.58 | | D | 1.9 | 1.15 | 0.72 | 0.58 | 0.36 | 0.29 | fault loop impedance calculator
Zs ≤ 0.8 × Zs(max) (for UK BS 7671 rule of thumb) Draw a table like this: | Supply type | Typical Ze (Ω) |