This manufacturing facility has four major plants producing high quality IC fabrication. The Facility Manager was looking for a solution to sub-meter different buildings, areas and specific processes so as to establish a foundation for implementing an energy reduction strategy. The maximum separation between each plant was less than 2km, and more than 100 scattered monitoring points with loads of up to 800A were required for sub-metering in the initial phase of this project.
Sub-metering could be difficult to implement due to 7x24 manufacturing, building layout and geographical separation. Wireless technology could be an attractive solution because it would help reduce the implementation obstacles as well as lower the installation cost for sub-metering scattered manufacturing processes that have previously been thought to be too difficult and too costly to justify.
Solution & Result
Among different wireless technologies, LoRa has various advantages over the others in range and penetration power so it has been widely used in environmental monitoring as well as smart metering.
CET’s PMC-352 is a wireless loT energy meter using the latest LoRa wireless technology. It works with the PMC-1302-3 LoRa Gateway operating in AS923 band (16 frequency channels are available for selection). The LoRa Gateway supports the efficient transfer of serial packets between the upstream network-based application via a TCP/IP connection and the downstream wireless LoRa meters. Each LoRa Gateway can communicate with a maximum of 128 wireless LoRa meters with the same frequency channel assignment. To resolve the crosstalk issue, the LoRa meters and gateways are grouped in four zones where each zone is assigned a different frequency channel as highlighted in the network diagram.
The PMC1304-3 Modbus TCP-RTU Gateways are also deployed as embedded Modbus Master Devices to poll all the PMC-352 LoRa energy meters autonomously via the PMC-1302-3 LoRa Gateway and subsequently provide the data via Modbus TCP interface to the client’s SCADA or EMS system. This makes it extremely simple for the client’s system to collect data from these downstream LoRa energy meters over a local area network. This mechanism also offers an intermediate buffer to store the historical data from all the connected devices and provide an extra level of data redundancy.
For Current measurements, Split-core CTs or Rogowski Coils are used for easy and non-intrusive installation. Rogowski Coil has a number of advantages over the traditional iron-core CT such as light weight design, large window size, mechanical flexibility and the ability to measure up to 5000A with excellent linearity over its wide dynamic range. Specifically, Rogowski Coils are deployed to perform Current measurement for circuits with multiple outgoing cables that would be impossible to measure using normal iron-core CT.
The implementation of a wireless LoRa metering solution could save a lot of time and cost relative to wired technology because physical cable installation is not required for communication. The PMC-352 integrates the metering function, a LoRa wireless module and an external antenna into a compact housing to make installation simpler, faster and easier. Supporting Split-core CT or Rogowski Coil allows the PMC-352 installation to be done live without the need to shut down the plant. Further, the ability to support different RF Channel settings in LoRa makes it possible to easily create different virtual LoRa networks to arbitrarily segregate the entire manufacturing facility into different sub-metering groups to prevent cross-talk of devices in the overlapping physical or frequency boundaries. From the application perspective, it is extremely simple to integrate the sub-metering data into the client’s existing SCADA or Energy Management System because of the use of the industry standard Modbus RTU protocol over the LoRa physical layer.