Some workplace installation of the GridLab have a local RS-485 network. This type of network is mainly used to communicate between several devices of the same type and ends within the GridLab usually with a RS-485 to TCP/IP gateway or something like that.
Usage Within the District Units
The power meters SICAM P50, which are a part of the District Units, uses such a RS-485 network. The communication between a master device and the power meters happens over an Exsys EX-6051 RS-485 to TCP/IP gateway. The configuration of that gateway may be found in the device description of the Exsys EX-6051 and the Internet Protocol.
The used protocol is Modbus RTU. The protocol parameters are listed below.
The addresses of the power meters consists of two digits. The tens position indicates the District Unit of the power meter and the units position the power meter within the District Unit. So for example the address of the the power meter 4 of the District Unit 2 is 24.
The RS-485 bus is connected over a custom cable. A custom cable was necessary because there are different types of devices connected together on the bus. The Exsys EX-6051 RS-485 to TCP/IP gateway requires another pinout than the SICAM P50 power meters. The following figure shows the pinning and configuration of that cable.