Patent Publication Number: US-9906270-B2

Title: Concurrent outbound communications in a TWACS

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of U.S. provisional patent application 62/138,715 filed Mar. 26, 2015. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     BACKGROUND OF THE INVENTION 
     This invention relates to a Two-Way Automated Communications System (TWACS) used by electrical utilities to communicate between the utility and a customer site; and, more particularly, to concurrent outbound communications in a TWACS communications system. 
     In an electrical utility, a TWACS concurrent outbound signal injection scheme is employed to simultaneously route outbound communications on three phases of the voltage waveform propagating through the utility&#39;s low voltage distribution network. In this regard, a TWACS outbound signal is the “common language” used to describe a signal generated by Substation Control Equipment (SCE) utilized in the TWACS power-line communication system. The outbound signal is carried on an AC distribution voltage routed to remote locations (e.g., customer sites) and received by Remote Communication Equipment (RCE) installed at the remote location. Commands contained in an outbound signal cause the RCE to perform various tasks, one of which is transmitting a communication or signal back to the SCE. This response is referred to as an inbound signal or inbound communication. 
     SCE equipment installed at a power distribution substation uses expensive coupling transformers to inject an outbound signal into a waveform propagated through the utility&#39;s power distribution system, and to acquire and detect an inbound signal on the system&#39;s high voltage circuits. These circuits are typically 7 kV-35 kV circuits. Both the SCE and RCE have to transmit at relatively high current levels to produce a signal that can be detected at the other end of the power distribution system. In the system, there are usually a large number of RCE points per distribution substation. A distribution substation then typically feeds a large number of distribution transformers that step down the high voltage propagated through the power distribution system to low voltage levels necessary for customer use. And, while there are typically few RCE points per distribution transformer, this topology, which is common in the United States, suits the current TWACS implementation well. 
     However, in certain foreign countries and some domestic applications, the topology of a power distribution system is significantly different from the topology described above. In these applications, a power distribution system or network has many fewer distribution transformers and many more electrical utility customers per distribution transformer. In addition, the accessibility to install TWACS SCE equipment in the power distribution substations in some of these utilities can be severely limited. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention utilizes only three of the previously required six power system vectors (A-B, A-C, B-C, A-n, B-n, C-n) necessary to communicate with RCE devices installed in the three phases (A-n, B-n, C-n) of a utility&#39;s low voltage distribution network for the propagation of concurrent outbound signals communicated over a TWACS. This reduction in phase vectors, in turn, simplifies a silicon-controlled rectifier (SCR) array used in a distribution control unit (DCU) at a utility substation for generating outbound signals which are now generated concurrently rather than sequentially. 
     The present invention further improves a search process for determining which outbound signal transmission path for a RCE device provides the best results for signal reception for a valid inbound communication by a factor of three. Subsequent transmissions of outbound signals to individual RCE devices, or groups of RCE devices, and the receipt of resultant inbound communications is also improved by a factor of three. 
     Other objects and features will be in part apparent and in part pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system diagram illustrating an outbound silicon-controlled rectifier (SCR) array; 
         FIG. 2  illustrates vector separation for the three phases; 
         FIG. 3  illustrates a sequential outbound search approach to determine which phase vector yields the best results for a valid inbound communication; 
         FIG. 4  illustrates a concurrent search approach to determine which phase vector yields the best results for a valid inbound communication; 
         FIG. 5  illustrates meter reading using sequential outbound communication signals; and, 
         FIG. 6  illustrates a resulting meter reading capability using concurrent outbound communications. 
     
    
    
     Corresponding reference characters indicate corresponding elements throughout the several views of the drawings. 
     DESCRIPTION OF THE INVENTION 
     In accordance with the invention, an improvement to a TWACS communication system utilizes a distribution concentrator unit (DCU) located on the low voltage side of a power distribution network to communicate with a large number of RCE points per distribution transformer. Because a TWACS signal does not have to traverse an entire distribution network, from high voltage to low voltage, for outbound signals, and then back again for inbound signals, in order to produce an adequate signal for communications. An advantage of this approach is that the amplitude for a TWACS signal injected into the distribution network, in order produce an adequate signal for communications, is significantly reduced. 
     The normal method for injection the outbound signal uses a large coupling transformer together with a very high powered SCR array that can inject an outbound signal into only one of the six phase vectors (A-B, A-C, B-C, A-n, B-n, C-n) on the power system at a time. With the improvement of the present invention, only three of the six power system vectors (A-n, B-n, C-n) are required to communicate with RCE devices installed in the three phases of the utility&#39;s low voltage distribution network. This reduction from the six vectors to only phase-to-neutral vectors allows an outbound injection SCR array to be greatly simplified. See  FIG. 1 . Simplification of the SCR array, and the separation of vectors, now allows the SCRs in the array to be operated independently, and therefore concurrently. In this regard, and as shown in  FIGS. 2-5 , injected concurrent outbound signals are interleaved on the three phases (φA, φB, φC) by 120°. 
     To improve the throughput of the TWACS communication system for both searching devices and acquiring meter readings, it is desirable to perform as much of the communication as possible simultaneously all three of the phases of the power system. 
     In previous TWACS system implementations, an outbound signal was injected on one of the three phases and the SCE equipment would “listen” for a response on that phase. Each of the other phase vectors, in turn, would be similarly injected into the waveform and monitored. The results were then evaluated and the phase vector yielding the best results for a valid inbound communication would then be designated as the transmission path for the particular RCE device. This methodology was referred to as a search or sequential process and is shown in  FIG. 3 . 
     Now, an outbound signal is concurrently injected on all three phase vectors with all three phases of a subsequent inbound signal being received simultaneously. This inbound signal is evaluated and the phase producing the best signal reception for a valid inbound communication now determines the path for the particular RCE. It will be appreciated by those skilled in the art that this new signaling method improves the speed of the search process by a factor of three. See  FIG. 4 . 
     Also In previous TWACS system implementations, it was common that an outbound message be broadcast to all RCE devices with an inbound response not being requested. The outbound message would be injected first on one phase vector, and then on each of the other two phase vectors in turn. Now, using concurrent outbound injection in accordance with the present invention, an outbound signal is broadcast using all three phase vectors at the same time. Again it will be appreciated by those skilled in the art that this new signaling method improves the speed of the process by a factor of three. 
     Further in previous TWACS communication schemes, to have all three phases of an inbound signal occur simultaneously, the phase vectors of the TWACS outbound signal had to be injected sequentially, with appropriate delays being necessary between the outbound signaling and the subsequent inbound signaling. When performing functions requiring responses from RCE devices, a unique outbound message is formulated that simultaneously addresses groups of RCE devices on each of the three phases. This is as shown in  FIG. 5 . These unique outbound commands are now sent concurrently to individual RCE devices or to groups of RCE devices on each of the three phases with all the groups of RCE devices responding simultaneously. This is as shown in  FIG. 6 . This reduces the outbound communication time by a factor of three. 
     Based on the foregoing, the method of the present invention now allows a single search command (outbound signal) to be communicated on all three phases concurrently causing line-to-neutral connected RCE devices to respond to the to the concurrent outbound signal by identifying to which phase a device is connected. Also, in accordance with the method, concurrent outbound signals representing a broadcasted command are sent to all RCE devices on all three phases simultaneously. In addition, the method enables the acquisition of inbound communications from unique or individual RCE devices, or groups thereof, on each of the three phases as directed by an outbound communication sent to them. 
     In view of the above, it will be seen that the several objects and advantages of the present disclosure have been achieved and other advantageous results have been obtained.