Internal MV circuits

Internal MV circuits are dedicated to the supply of the secondary MV/LV substations dispersed in the installation. They are three typical principles commonly used for this purpose Fig. D11:

• Single feeder
• Dual feeder
• Open ring

Fig. D11 – Single feeder, Dual feeder, Open ring

Comparison of these three typical principles of internal distribution is given Fig. D12.

Fig. D12 – Comparison of the typical internal circuits

	MV circuit configuration
Characteristic to consider	Single feeder	Open ring	Dual feeder
Site topology	Any	Single or several buildings	Single or several buildings
Power demand	Any	> 1250kVA	> 2500kVA
Disturbance sensitivity	Long interruption acceptable	Short interruption acceptable	Short interruption not acceptable