The current switch model is missing the number of potential ports (necessary to model existing, but not equipped slots on a switch).
In SNMP, this is covered by ifNumber. The equivalent needs to be modelled in the IEC61850 model.
Proposal
I see 2 possibilities:
1) (preferred) add a DO to the (anyway already modified) LPHD e.g. IfCount (INS) or similar
2) (less good, because of dependencies) Make the modelling of ports in the Communication section mandatory for switches. <P type="Port">xxx</P> value should match PortNam, and an additional element <P type="PortNum">1</P> should match PortNum; “empty” slots would be modelled as <P type="PortNum">1</P> without a matching PortNum in the Switch DATA model (see also tissue 1295).