By Sandra Esposito and Fred Czubba
Similar to larger traditional hydroelectric systems, small hydropower systems (in Canada, 1 to 50 MW of installed capacity) produce electricity by converting mechanical energy from running water into electric energy. Small hydro systems either provide power to a connected grid or operate independently in stand-along applications in isolated remote areas.
Small hydro is a clean, renewable and predictable energy source and one of the best alternatives to the highly pollutant and costly diesel generation that currently provides electric energy in most remote communities across Canada. The potential energy produced by small hydropower technologies is estimated at 15,000 MW.
The focus of this case study is an existing dam in northern Canada. As with other schemes, this project features a reservoir that supplies water to a hydroelectric powerhouse, storing a significant amount of energy to feed into an electric transmission grid. To determine the amount of available energy, operators must accurately monitor the water height in the reservoir. As water flow varies during seasons, operators must maintain sufficient water levels in the reservoir to generate electricity.
This article illustrates how the move to a wireless sensor control system resolved the problems associated with an existing hard-wired hydrostatic water level monitoring system prone to frequent failures at a small hydroelectric power station in northern Canada.
A monitoring case study
An aging hydrostatic level sensing system at the dam (that connected to the power station via a hard-wired cable) frequently failed due to damage caused by falling trees and problems with ground faults and lightning strikes. Additionally, no power existed at the dam.
Installing a new hard-wired system posed physical challenges and high costs because of the environment. Adding a second hard-wired system to provide redundancy would double the cost. In addition, the wired system required cable and a power source for operations that limited its use in locations where communication services and power were limited or unavailable. Loss of power, which is typical around dams, can result in lost data and down operations.
The challenge, therefore, was installing a water level measurement system that could reliably monitor water levels at remote locations and transmit data to a power generation control system located 2 miles downstream from the dam in a secure, reliable, consistent and cost-effective manner.
A wireless telemetry system with a parallel repeater station provides a secure and robust solution to give power station staff valuable field data to determine the available energy in the reservoir. Meeting the stringent requirements of the dam monitoring application, the wireless system is failsafe, performs at extreme high and low temperatures, and operates only on battery and solar power, eliminating the need for cable and the associated risk of failure due to lightning strikes and ground faults.
The configuration of the new wireless remote sensing system, installed in 2017, consists of two solar-powered nodes that power and extract data from dual hydrostatic level transmitters suspended behind the dam in stilling tubes. Both nodes interface with individual gateways that store recent sensor readings in Modbus format. The gateways manage outbound communications to another gateway for delivery to a nearby control center.
This figure illustrates the configuration of the sensor control system installed at this hydroelectric facility.
One of the gateways interfacing with a node at the dam also serves as part of a parallel repeater station, sending redundant data to an alternate or backup gateway before its transmission to a final gateway situated near the control station. The parallel repeater station provides a secure, robust and redundant communication path for the data signal.
With a range of up to about 3 miles, the network with a redundant communications link is self-installing and self-configuring, so it immediately starts once the operator enters the settings, address and parameters for the individual components at a remote location. The wireless nodes automatically install into the radio networking system and adapt to network changes in traffic volume, radio transmission conditions, gateway availability and presence/absence of the adjacent node.
The sensor control system continually sends data on reservoir water levels to the control room. Using this information, operators can determine how much water is available and calculate how much electricity the powerhouse can generate for a certain amount of time based on water volume.
Alarm thresholds inform the control room when water levels are rising or falling beyond set parameters. Information is available across the entire power generation supply chain via an Ethernet module as other power plants within a region work together in a load sharing and load shedding system.
Results from this installation
Designed with a redundant sensor and communication link, the wireless dam level monitoring system increased the reliability of data transmission to the control center. The configuration of the telemetry system also allowed plant maintenance personnel to implement preventative maintenance on system A while system B maintained operations. In addition, maintenance personal no longer needed to check 3 miles of wires from the dam to the powerhouse, increasing uptime while ensuring an outage did not occur due to a maintenance or system failure. While efficiency is an important component in any power generation plant, reducing the possibility of an outage is a much higher priority.
<<author bios>>
Sandra Esposito is sales and marketing director with SignalFire Wireless Telemetry. Fred Czubba is president of AXE Consulting Ltd.
