Patent ID: 6947269

Claim:
A system of communicating information over a communication line which connects at least two protective relays for an electric power line wherein communication between the two relays is in the form of successive data messages which include output status bits from one relay to the other relay, the output bits representing the result of protection functions carried out by the one relay, wherein the communication has a channel capacity which is not completely used by the output bits transmitted, the communication system of this invention comprising: processing means for encoding additional data from said one relay and inserting it into vacant channels in the communication between the two relays; means for including synchronization information for said additional data on a synchronization channel in the communication, as part of the successive data messages; means for transmitting said data messages successively on the communication line; and processing means at the second relay for receiving and decoding the successive data messages to produce replicated output bits and the additional data transmitted from the one relay, wherein the speed and security of the additional data is approximately at least as good as that for the output bits.