By Yuan Xuping

The article discusses the cost of communication resources in a low voltage carrier wave AMR system, in order to catch the attention of developers.

The keyword of the design principle of the Topo relay independent network technology is the “Topo relay approach”. The independent networking technology follows the principle of “the end of the active side, the PTMP half duplex communication.”

On the existing low voltage grid, the correct relay location is chosen using the “blurred relay” method. The method of learning the network system is “exhaustive attack”. The route is changeable according the environment, so it is necessary to search again the failed communication routes in the network. Therefore, at the moment of meter reading this process is inserted in order to maintain the mid-level route link. It takes much time to establish the network consumption, and the carrier wave communication is energy intensive. If the network technology is elaborately designed, the learning time can be included in the practical applications.

The key to the design principle of the dynamic network technology is “conflict avoidance”. The Lonworks network technology is based on carrier sense, with the support of related hardware to realise conflict avoidance by testing the signal-to-noise ratio and signal Q value in carrier wave communication.

There are two models of the dynamic network technology, interactive subnet and “flooding”.

Interactive subnet network technology
In an interactive subnet network, the whole communication net is divided into several parts. A concentrator is used to build the subnet, and to allot the subnet identification number as well as identification numbers of the nodes in the subnet. The concentrator chooses a node in the subnet as the route gateway according to the Q value, in order to ensure continuity in communication. This needs network forming time, meanwhile the network maintenance process should be inserted at the moment of meter reading.

“Flooding” network technology
One more key in the design principle of flooding network technology is the “random router.” The flooding model network is a multi-way random routing. The “conflict avoidance” method makes it possible to realise multi-way routings in different net spaces. Each node member takes the initiative to play the role of transit gateway, and starts networking when a recording order is sent by the concentrator, and then quickly finds the route to the targeted meter. The node responds to the orders sent to it, while transmitting orders sent to other nodes, and when the network is idle, the orders are delayed randomly for a period before transmission.

This is the way of realising a flooding network. Communication is realised by way of abandoning repeated receiving package, and controlling way-up and way-down directions, package numbers, and other order transmission methods. “Flooding” is a swift way of meter reading, but more nodes are needed in the relay doing the transmitting, which means more energy will be consumed.

In the low voltage AMR “flooding” system developed by Shenzhen Star Instrument Co., Ltd., communication between the front end processor and the concentrator is via GPRS, with switching to FTP when there is a big data transaction. Communication between the server, administrative equipment and the front processor is via FTP. Meter reading between the concentrator and meter is via “flooding”, with the concentrator monitoring and reading power consumption information of the meters in the delivery area.

The system realises such functions as alarming in abnormal carrier wave conditions, monitoring the operation conditions, consumption information reading, charge controlling, phase self monitoring, load balance analysis and power line damage analysis, etc.

The class priority should be sorted according to the Q value. The principle of a limited topo relay level should be ensured, and the periphery nodes of the subnet should have higher priority when establishing the message delivery route.

Two or more concentrators should be used for control in a large region. The conflict between the nets can be avoided through the “conflict avoidance” approach.

In addition, the function of self-adjusting the receiving limitation in carrier wave chips should be added, as should a reasonable receiving limitation value according to the noise at site, and adjusted according to the change of the environment.