Connection to the utility network

The possible solutions for the connection of an installation to the utility network are the following:

• Connection to the LV network for small and medium size installations requiring less than 400 kVA. Fixing this limit is always under the responsibility of the local utility managing the LV network
• Above this previous limit, connection to the MV network with either LV or MV metering. LV metering is generally authorized for installation including a single MV/LV transformer not exceeding the rated power limit fixed by the utility, generally around 1250 kVA.

The possible connections to a MV utility network are the following, (see Figure D8, D9 and D10):

• MV single-line service,
• MV ring-main service,
• MV duplicate supply service, including two load break switches equipped with an automatic change over,
• MV dual supply service with two independent connections to the utility and two bus bars connected with a bus tie. The two utility incomers and the bus tie are equipped with an automatic change over.

Comparison of this four modes of connection are summarized in Fig. D7

Fig. D7 – Comparison of the modes of connection

Characteristic to consider	Configuration
	LV	MV
		Single-line	Ring-main	Duplicate supply	Dual supply
Activity	Any	Any	Any	High tech, sensitive office, health-care	Very sensitive installations
Site topology	Single building	Single building	Single or several buildings	Single or several buildings	Single or several buildings
Service reliability	Minimal	Minimal	Standard	Enhanced	Very high
Power demand	< 400 kVA	≤ 1250kVA	Any	Any	Any
Other connection constraints	Any	Isolated site	Low density urban area	High density urban area	Dedicated measures taken by the utility

Fig. D8 – MV connection with LV metering

Fig. D9 – MV connection with MV metering

Fig. D10 – Dual MV connection with MV metering