Lindmore Irrigation District uses Ethernet radios to improve SCADA communications system and pumping efficiency.
In many areas of the world, agriculture depends on irrigation. This is particularly true in Central California where increased demand and limited water supply creates many challenges for irrigation districts.
Because of their importance to the agriculture base, investments in maintaining and upgrading irrigation systems must have a high priority. Automation is necessarily a part of that investment because it enables water districts to conserve water and power and to lower labor costs and reduce overhead while ensuring accurate billing.
An electrical engineering firm is working with the Lindmore Irrigation District in Lindsay, Calif., to upgrade its SCADA network. As part of this upgrade Phoenix Contact was chosen to provide Wireless Ethernet (TWE) radios, antennas, and power supplies (Figure 1).
Figure 1. A Phoenix Contact radio and power supply mounted in a control cabinet
Irrigation Challenges
The Lindmore Irrigation District is located in the east central portion of California's San Joaquin Valley. It receives its water from the Friant-Kern Canal, a 152-mile Central Valley Project aqueduct managed by the U.S. Bureau of Reclamation in Central California.
The district serves the communities of Lindsay and Strathmore, Calif., as well as around 1,200 agricultural customers that grow citrus, olives and almonds in a 100 square-mile (10-mile x 10-mile) area. It also provides supplemental irrigation capacity to Fresno, Tulare and Kern counties.
Completed in 1951, the Friant-Kern Canal begins at Millerton Lake, a reservoir on the San Joaquin River north of Fresno. It flows south along the eastern edge of the San Joaquin Valley, ending at the Kern River near Bakersfield. The canal provides water at 5,000 cubic feet per second (cfs) at its source, gradually decreasing to 2,000 cfs at the Kern River.
On the west side of the district, water is delivered to about 500 farmers on more than 26,000 acres. Water flows from east to west from the canal through 18- to 22-inch main pipelines. Pipes connected to the main pipelines run north to south to supply water to the farmers.
The 10-mile by 10-mile area is a very large area to cover, but pumping is not required on the west side of the canal because these pipelines are gravity fed.
The three gravity-fed bilateral pipelines (called “avenues”) are approximately five miles apart. Each of the first two is about 10 miles long. The third is about eight miles long. These bilateral pipelines transport the water from the canal to the farmers.
Rise tubes or pipes located every 2 to 5 miles along the bilateral pipelines maintain head pressure. Specifically, a programmable logic controller (PLC) that is part of the district's SCADA system maintains the head pressure by operating gate valves at the rise tubes. Before the PLCs were installed, operators had to drive to each rise tube to manually open and close the gate valves.
However, locations on the east side of the canal need pumps to push the water to higher elevations. A pumping plant operates several pumps with motors from 25 to 60 horsepower—some with variable frequency drives (VFDs) and some without. Water delivery rates range from 1.7 cfs to 3.3 cfs. The system was largely manually controlled, which left considerable room for improvement.
Manual to Automatic Control Conversion
The primary objective of the pumping plant is to maintain reservoir level and flow demand (Figure 2).
Figure 2. Irrigation pumps deliver water to customers in the higher elevations to the east of the canal.
When farmers call with their water requirements, district operators select the number of pumps to operate. Each pump has a selectable setpoint at the reservoir level. Once the reservoir level reaches its setpoint, the pumps stop. Head pressure at the reservoir maintains the line pressure.
In the past, the district relied on manual metering to provide water to its customers. When a customer needed water, a technician had to drive to the customer's site and manually open a valve. This process provided almost no flow rate or water volume data. The only way to measure how much water was delivered was to note how long the valve was open.
Not knowing exactly how much water each customer received made billing difficult and potentially inaccurate, not to mention the wasting of resources. Deviation between the amount of water actually provided and the estimated amounts could vary from 30 to 40 percent.
The district estimated water volume according to motor horsepower, pump efficiency and elevation. If the district operators knew the field size and flow, they just needed to determine how many pumps they needed to operate. For example, if they needed a flow rate of 6.6 cfs, they turned on three pumps and billed accordingly.
The State of California maintains official flow measurements at the canal water connection points. The state allowed the Lindmore Irrigation District to connect to its meters. The water measurement deviations were based on the difference between the state's measurements and the district's estimates.
Before the upgrades, the district's water delivery and measurement system was not accurate or efficient. Now, the district measures and monitors actual water use. The operators record exactly how much water flows and where it goes, and the database keeps track of the water use and billing.
To make this monitoring possible, the district installed flow meters to measure how much water flows through each pump, and what's being pumped back to the reservoirs. The district also knows the each reservoir's capacity and measures the water levels, which were also included in the SCADA system.
Lindmore Irrigation District's SCADA upgrade included implementing PLCs and VFDs at pump stations, motor-driven valves and wireless communication technology to link all local automation to the human machine interface (HMI) platforms. Converting the district's SCADA system communications to a wireless platform greatly improved its accuracy and data collection throughput.
Because of the upgrade, the district reduced personnel resource requirements. Technicians will no longer be required to initiate water distribution. Water conservation is improved through more accurate water monitoring, and Lindmore Irrigation District customers can rest assured that their water bills will be accurate.
SCADA System Upgrade
The electrical engineering firm advised the district to upgrade to a wireless system because of inefficiencies in the communications among the PLCs within the SCADA system. They knew that, with the wireless system, the Ethernet connection at each site would allow remote administration capabilities. This would provide more bandwidth to enable the engineers to perform instant remote diagnostics from their office. The technology would also provide reliable operation.
Six TWE radios have been installed at the time of this article. To provide district-wide radio coverage, a 60-foot antenna tower was erected at the district's central office.
Around 28 additional radios will be installed during the next 12 to 18 months on all reservoirs, pump stations and main trunk lines. As many as 1,200 radios may be installed over several years. Four master radios are planned for the entire project.
A PLC at each reservoir transmits data to the pumping plant to control the pumps. The junction box and the radios at the pumping plant transmit the data to the district's office SCADA computer. One PC with Web client access is used as the SCADA server. The district's other PC is at the district office where the operators can access the Internet, if necessary.
The PLCs' use the EtherNet/IP multicast protocol and the ability of the wireless system to transmit this protocol reliably and quickly contributed significantly to the success of the upgrade project.
Each avenue master junction box is equipped with an HMI to monitor and control the operation of its avenue and the entire district. Operators can make set point changes, monitor and acknowledge alarms at each of the five HMIs. The HMIs communicate with the radios via Ethernet.
The electrical engineering firm controls the level by opening and closing large gate valves based on the number of shaft turns because it has no feedback of gate valve position.
The engineers run the gate valve motor 5 seconds and wait 35 seconds to see if the level is achieved. The next upgrade will use proportional integral derivative (PID) control to maintain the levels.
The engineers used 900 MHz radios for communications from the reservoirs to the pumping plants and for the bilateral connections to the district's offices. The bilateral connection radios provide the parameters listed in Table 1.
| Table 1. Bilateral Connection Parameters |
| Pump Status |
| Reservior levels |
| Gravity-fed water system information |
| Pumping plant PLC data |
| Run status |
| Run command |
| Pit level |
| Line pressure |
| Communication status |
| Line voltage level |
| Line voltage condition |
| Motor current (for each pump) |
| Motor demand |
| Motor kVAR |
| Motor phase rotation |
| Number of run hours per motor per day |
| UPS battery status |
| Daily recorded data |
| Global ratings |
The rise tube PLCs transmit the parameters listed in Table 2.
| Table 2. Rise tube PLC parameters |
| Level |
| Flow |
| Gate valve open status |
| Gate valve motor control status |
| Communication status |
| UPS status |
The plan was, first, to measure the flow of the main lines to calculate the total volume of water then tie those measurements to the radios that are installed. The engineers needed a saturated radio network so they can cover the entire district.
PLCs use messaging blocks to read and write to the registers. Also, alarm status is passed along in message blocks. These alarms include high and low levels, high and low pressures, uninterruptible power system (UPS) battery status, control door open and the temperature inside the PLC and radio cabinets. The radios transmit these data to the SCADA system.
PLCs control reservoir levels by varying the VFD signals for pump speed. PLCs control individual vessel levels using control valves. PLC inputs include pump run status; run commands; power loss; and pressure, flow and level indicating transmitters. Analog outputs control the VFDs. The PLCs connect to the radios through Ethernet connections. This scenario allows the engineers to program and maintain PLC programs via a secure virtual private network (VPN) to their office.
Improved Communications
The district's original radios used serial data and were limited in terms of bandwidth and data. However, the new wireless system uses Ethernet, which allows engineers to connect via the Internet. The flexibility and Web connectivity of the TWE radios allow the district to connect to nearly any device at any site. For example, operators can monitor VFD status to acquire data such as kVAR and kVA demands to make energy adjustments so they can take advantage of off-peak utility hours.
The new radios offer the ability to configure a single radio as a master, slave or slave/repeater via built-in Web-based management pages. Having this configuration software built into the radio also simplifies installation.
Compatibility with third-party control protocols was another important decision criterion. The ability of the TWE radio to wirelessly transmit the PLC's EtherNet/IP multicast protocol in a quick and reliable manner was a big factor contributing to the success of the upgrade.
The wireless system allows engineers to connect to each PLC remotely to diagnose potential problems. It is also expandable to multipoint communication. More bandwidth is available to expand communications to farmers' fields to collect data such as flow, pressure and motor run status. The Ethernet radios also monitor reservoir levels and update the PLCs and the SCADA system to control the pumping plant.
Based on the engineers' recommendation, Lindmore Irrigation District chose the TWE radios because of product availability, technical support, product quality and terms of warranty. The radios were tested and had no communication failures over an 11-month period.
Prior to implementation, the Phoenix Contact engineering team examined the radio signal path. Based on the survey information, it added new functions to the radios—such as network filtering to reduce multicasting and blocking certain frequencies. Because of the reliability of the TWE radios, service calls to the district sites have been virtually eliminated. Reduced service calls translate directly to less travel time.
“We believe we'll achieve better water distribution control both from a logic standpoint as well as a control system design standpoint, and we anticipate much less maintenance,” says Lindmore Irrigation District General Manager Michael Hagman.
Pumps & Systems, September 2011
