August 2015

Power Monitoring: Maintaining High Performance in Large-Scale Multiple-Device Networks

With competition continuing to increase in the electrical energy market, reducing energy usage and cost is important. According to the International Energy Agency, improving the energy efficiency of our buildings, industrial processes, and transportation systems can reduce the world's energy needs in 2050 by one third1. The reason more and more companies have invested in energy efficiency in recent years is because the cost of adopting sophisticated power consumption monitoring systems is much less than the amount of energy savings that can be realized. In the past, we addressed the increase in electrical consumption in HVAC (Heating, Ventilation, and Air Conditioning) systems and Data Centers, and saw how to take advantage of protocol conversion solutions to monitor energy usage and transmit all of the data back to a control center for further analysis. In this article, we introduce a power substation application that not only implements remote monitoring, but also allows you to monitor multiple devices without sacrificing performance.

Application Background: Customer Challenges

Current trends in power management are having a major effect on the power substation industry. Starting in 2013, a leading company in power and automation technologies started offering a power monitoring solution that allowed users to connect multiple Modbus RTU devices, such as power meters, power RTUs, and protection relays to a Modbus TCP network. However, connectivity was not the major challenge that they faced. The major concern was the resultant latency; currently, the only solution they have been able to implement is connecting a single device to each serial port. However, they needed to find a way to avoid using the traditional round-robin polling mechanism, which supports only one Modbus protocol request-response action at a time, resulting in poor performance. What's worse, this solution wastes SCADA resources and network bandwidth. In addition, another important requirement is adopting an effective power and Ethernet redundancy regimen to ensure system reliability.

To summarize, there are three major requirements:

  1. Connecting a large-scale network of Modbus RTU devices to a Modbus TCP network, without keying-in any Modbus commands, and still maintaining high performance
  2. Dual Ethernet connections that support dual IP addresses
  3. Dual VAC/VDC power input

Moxa's Solution: High Performance with Active Polling

We addressed the above challenges of monitoring multiple devices in a large-scale network with an innovative, intelligent method that uses Moxa gateways to actively collect all of the data retrieved at a remote site. With this technology, you do not need to waste time configuring the hundreds of Modbus commands, storing them in your Modbus gateways as copies from the SCADA. Instead, the local controllers reply immediately to SCADA requests by sending pre-read data, without being delayed by slow serial device response.

Since the gateway actively and continuously retrieves data from Modbus devices simultaneously through different serial ports, users will see a dramatic reduction in the amount of time a Modbus device needs to wait to be accessed. SCADA systems can retrieve Modbus device data directly from the gateway's memory, instead of waiting for the gateway to pass commands to the serial ports, thereby enhancing the Modbus gateway's communication performance. Moxa's MB3660-8/16 gateway performs more than 10 times faster compared to a traditional round-robin polling mechanism.

Power and Ethernet Redundancy

For a complicated Modbus system, redundancy is extremely important. The MGate MB3660 Modbus gateways support redundancy for both the power input and Ethernet connection. The MGate MB3660 gateways come with dual AC or DC power inputs built in for power redundancy, and have dual Ethernet ports (that support different IPs) for network redundancy.

For more details about the MGate MB3660, check here. You may also refer to our Modbus FAQ.

References

  1. Sophie Hebden (2006-06-22). "Invest in clean technology says IEA report". Scidev.net. Retrieved 2010-07-16.
 
 
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