In agricultural installations using SWA, what protective-conductor requirement must be observed?

In agricultural installations using SWA, what protective-conductor requirement must be observed?

• A. The steel armour must be used as the sole protective conductor
• B. The steel armour must not be used as the sole protective conductor; a core inside the cable must be provided
• C. Armour is optional and can be used as protection only
• D. No protective conductor is required

Answer: (B)

The important idea is that the protective conductor (earth) path must be a defined, reliable path to earth, not something you rely on casually for fault protection. In SWA cables, the steel armour mainly serves to protect the conductors physically. It’s not guaranteed to stay continuous or intact in field conditions (think vibration, impact, corrosion, or damage common in agricultural setups), and fault currents need a low-impedance, dependable path to trip protective devices quickly. Therefore, a dedicated protective conductor must be provided inside the cable (or a separate conductor run) and connected to earth at the proper points. This ensures a reliable earth path even if the armour is damaged or compromised. The armour alone should not be used as the sole protective conductor.

The important idea is that the protective conductor (earth) path must be a defined, reliable path to earth, not something you rely on casually for fault protection. In SWA cables, the steel armour mainly serves to protect the conductors physically. It’s not guaranteed to stay continuous or intact in field conditions (think vibration, impact, corrosion, or damage common in agricultural setups), and fault currents need a low-impedance, dependable path to trip protective devices quickly. Therefore, a dedicated protective conductor must be provided inside the cable (or a separate conductor run) and connected to earth at the proper points. This ensures a reliable earth path even if the armour is damaged or compromised. The armour alone should not be used as the sole protective conductor.