During typhoons and torrential rain, the water level of rivers may become too high for the rainfall to be discharged through gravity. Pumping stations are used to pump water from the city into nearby rivers. Pumping prevents accumulation of flood water in urban catchment areas. When the water level of the river rises to a critical level, the sluice gate must be closed to prevent the river from flooding the city. These pumping stations must be connected to a central control center by an extremely reliable communication network.

Station pumps need to be large and powerful in order to move the amount of water needed, but because the pumps are so large, they can create a significant amount of electromagnetic interference (EMI) which can create havoc on traditional commercial communications networks. At a particularly large-scale application this involves 66 permanent and 21 temporary pumping stations, and the authorities responsible turned to Etherwan for technical consultation and implementation.

The application requirements are to ensure the safety of people in areas with flood hazards; to support remote monitoring and automation control of many devices; to maintain reliable performance of the station systems in hot or cold weather;  to maintain fast recovery times; to allow management as necessary to divide the network into sub areas; and finally to maintain a simple network topology.

The challenge of the project is the high EMI levels from the pumps which is a major concern. Additionally, some of the pumping station sensors connected to a programmable logic controller (PLC) which had its own communication BUS. Noise between the PLC and the Ethernet Switch was present. Finally, advance layer 3 networking was overly complicated for the environment. Thus, Etherwan has employed EX77900, EX27000, and Ex39924 to complete the job.

EX77900 is a Lite Layer 3 Hardened Managed 24-port Gigabit and 4-port 1G/10G SFP+ Switch (includes Lite Layer 3 and VRRP gateway redundancy), the EX27000 is a Managed 24-port 10/100BASE and 4-port Gigabit Switch, and the EX39924 an Industrial Unmanaged 24-port Gigabit Switch with 4/16-port combo SFP Slots.

To meet the challenge of the environment with high EMS and electrical surge issues, the EX77900 was chosen because it is certified for EN 61000-4-2 through EN 61000-4-8, which ensures a high level of resistance to ESD, RFI, burst and surge standards. This would effectively address the “noise” problem from the large pumps in the pumping stations.

For maintenance reasons, the network had to be divided into easily managed sub-networks. In this circumstance, a Lite layer 3 switch was the ideal solution because it allows high performance Layer 3 segmentation at a lower cost. Basic RIP and static routing protocols were all that was needed in this application, the EX77900 was a perfect fit and saved thousands over other solutions that were just overkill for the application.

For maximum network redundancy and minimized failover time, Etherwan's proprietary Alpha-Ring protocol was used in conjunction with VRRP (Virtual Router Recovery Protocol), ensuring redundancy in the event of any failure type. A recovery time of milliseconds instead of seconds can mean the difference between millions of gallons of water pouring into designated catchment areas – or pouring into the city streets.

The VRRP protocol provides for automatic assignment of available routers to participating hosts. This increases the availability and reliability of routing paths (the connection between the subnetworks), Working together, the Alpha-ring and VRRP protocols ensure the availability and reliability of data links for this critically important network. Etherwan's years of experience and technical expertise delivered a robust, redundant yet simple cost-effective solution. Maximum reliability and a simple design at a reasonable cost was the way to address this clients needs.