The present invention discloses a method of transmitting time-critical messages in an OSI layer 2 network tunnel from a first TED in a first substation to a second IED in a second substation over a WAN, wherein each of the first and second substation comprises an edge IED and is associated with a substation LAN, wherein each of the time-critical messages comprises message parameters. The method comprises the steps of: a) creating a translation table comprising corresponding values of the message parameters, between the LANs and the WAN, b) defining a virtual FED in the second substation using the translated values of the message parameters, to impersonate the first IED, c) translating the message parameters according to the translation table, by the edge IED of the first and second substation, d) forwarding the time-critical messages from the first IED in the first substation to the WAN, and e) receiving the time-critical messages by the second IED in the second substation from the WAN.