| Parameter | Description | |-----------|-------------| | | Full load current of the circuit | | Cable length (m) | One-way distance from source to load | | Voltage (V) | System voltage (e.g., 230V, 400V) | | Phase | Single-phase or three-phase | | Installation method | Buried, in conduit, on tray, clipped direct, etc. | | Ambient temperature (°C) | Affects current-carrying capacity | | Insulation type | PVC, XLPE, rubber, etc. | | Allowable voltage drop (%) | Typically 3% for lighting, 5% for power | | Short-circuit rating | Optional for high-fault installations | Core Calculations 1. Current-Carrying Capacity (Ampacity) Using correction factors: [ I_z = I_n \times k_temp \times k_group \times k_soil \dots ] where ( I_z ) ≥ circuit design current. 2. Voltage Drop Single-phase: [ V_d = \frac2 \times L \times I \times (R \cos\phi + X \sin\phi)1000 ] Three-phase: [ V_d = \frac\sqrt3 \times L \times I \times (R \cos\phi + X \sin\phi)1000 ] Result must be ≤ permitted drop. 3. Short-Circuit Temperature Rise Ensures cable can withstand fault current until protection operates. Example Calculation (Simplified) Load: 30A, 230V single-phase Length: 50m Installation: Clipped direct, PVC insulated, 30°C ambient Allowed drop: 3% (6.9V)
