Sizing and protection of conductors

Conductor sizing and protection

• Conductor sizing: methodology and definition
• Overcurrent protection principles
• Practical values for a protective scheme
• Location of protective devices
• Conductors in parallel

Practical method for determining the smallest allowable cross-sectional area of circuit conductors

• General method for cable sizing
• Recommended simplified approach for cable sizing
• Sizing of busbar trunking systems (busways)

Determination of voltage drop

• Maximum voltage drop limit
• Calculation of voltage drop in steady load conditions

Short-circuit current

• Short-circuit current at the secondary terminals of a MV/LV distribution transformer
• 3-phase short-circuit current (Isc) at any point within a LV installation
• Isc at the receiving end of a feeder as a function of the Isc at its sending end
• Short-circuit current supplied by a generator or an inverter

Particular cases of short-circuit current

• Calculation of minimum levels of short-circuit current
• Verification of the withstand capabilities of cables under short-circuit conditions

Protective earthing conductor (PE)

• Connection and choice for protective earthing conductor
• Sizing of protective earthing conductor
• Protective conductor between MV/LV transformer and the Main Low Voltage Switchboard (MLVS)
• Equipotential conductor

The neutral conductor

• Sizing the neutral conductor
• Protection of the neutral conductor
• Breaking of the neutral conductor
• Isolation of the neutral conductor

External links

• Electrical Conceptual information given in "Cahiers Techniques"
• Electrical design software