TWACS??, A New Viable Two-Way Automatic Communication System for Distribution Networks. PART II: Inbound Communication

A new concept of two-way automatic communication for distributed systems, henceforth abbreviated as TWACS??, is introduced in this paper. This paper restricts itself to the discussion of inbound signalling from the remote transponder units at the customer's premises to the receiver located at the substation. Inbound signalling uses current pules, precisely generated and limited to only a small segment of a half cycle of the 60 Hz wave. The inbound signal is detected in the neutral or phase bus conductor at the substation. Bit coding, multichannel assignment, detection algorithms and propagation characteristics are explained and discussed and the paper concludes with field results obtained at many different utilities. A previous companion paper [1] presents the basic functions and features of TWACS?? and describes outbound communication. This paper focuses on TWACS?? inbound communication and presents the subject as follows: ??? general description of TWACS?? inbound communication technology, ??? signal generation and propagation, ??? signal detection, ??? bit coding and multichannel signalling, ??? noise characteristics, ??? error correction and detection, ??? field experience. Using a block diagram of a typical TWACS?? installation, the operation, synchronization and performance of inbound communication is introduced. Inbound signals are generated by drawing current pulses at the remote transponder units. The actual transmitter consists of a low impedance load inductor and a pair of anti-parallel connected SCRs in parallel with the 240 V line. By limiting the on time of the SCRs the amplitude and duration of the current pulses can be controlled.