Scheme 5 Scheme 6 Scheme 7 Outgoing line Metering Incoming line 1 Incoming line 1 Incomingline isolation Incomingline isolation Incomingline Metering Metering Incoming line 2 Incoming line 2 PT PT PT Outgoing line Outgoing line Outgoing line Outgoing line Outgoingline Outgoingline Outgoingline Outgoingline Outgoingline PT PT Contact Isolation Outgoing line Outgoing line Contact Isolation