Westinghouse Electric Corporation

Roger E Ray

Shan C Sun

Charles W Einolf, Jr

Harold B Shutterly

Karl C Koch

Russel W Gonnam

Pamela M Maynard-Nenno

John C Gambale

The multiplexer in a multichannel, secure digital communication system repetitively embeds a sequence of byte length uniquely coded synchronizing signals in each of n successive frames of one channel of a multichannel, time multiplexed digital bit stream. Redundant protective relay data and associated parity check data are embedded in four of the n frames in a second, preferably adjacent channel, with the remaining of the n frames in the second channel containing additional of the uniquely coded synchronizing signals. The time multiplexed serial bit stream is transmitted to a remote station, preferably by fiber optic communications media. The most recent bits of the received serial bit stream equal in number to the number of bits spanned by the two channels in n frames are retained in n-1 serially connected serial in, serial out shift registers. Sixteen bit portions, a frame apart, of the retained most recent bits of the serial bit stream are applied to n serial in, parallel out shift registers. The parallel outputs of these shift registers corresponding to the frames of the two channels encoded with the synchronizing signals are compared with the sequence of uniquely coded signals stored in addresses in PROMs. When the compared signals match, which will occur once in every n frames, a synchronization signal is generated and the protective relay data and parity check data are read directly from the other parallel outputs of the serial in, parallel out shift registers. Similar rapid resynchronization of voice and data channels in the time multiplexed serial bit stream can be achieved by counting the number of bits in the bit stream from the generation of the synchronization signal in the relay protection channels to the beginning of the time slot for a selected voice or data channel.

Apparatus and method for secure digital communication

A protective relay system for providing pilot protection for two and three terminal alternating current transmission lines, which system does not require a continuous metallic circuit between the relaying points. The evaluation circuit develops operating and restraining quantities, modified by a predetermined constant which determines the operating characteristic of the relay system.

Protective relay apparatus

This disclosure relates to a protective relaying system for a polyphase power transmission line in which at least two separate line operating conditions at a remote end of a protected line section are transmitted to a local end of the line section over a single communication channel. In the preferred illustrated embodiment, the operating conditions of three-line conductors are sequentially transmitted whenever a fault condition is sensed on any one or more of the three-line conductors. During the normal, non-faulted operation, a coded signal is continually transmitted to maintain the time derived signals at the receiver in substantial synchronism with the time derived signals of the transmitter. The coded signal also establishes a trip inhibiting or guard signal at the receiver.

Time division multiplex system for a segregated phase comparison relay

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Coral Springs, FL, United States of America

Roger E Ray