Wireless sensors monitor carbon brushes in hydropower

At the Pikerfoss hydropower plant in the middle of Numedalslågen, Norway, up to 120 cubic meters of water flows through the turbine every second. Now this power becomes smarter and safer with El-Watch wireless sensors.

Pikerfoss is a hydropower plant with 16 MW installed capacity. This is more or less enough to power about 3,000 Norwegian households. The mechanical energy from the water is converted into electrical energy through coal brushes that are close to the slip ring. In this process, the brushes wear down gradually, and they must be changed after about a year. When the brushes are to be replaced, the power plant must be stopped.

Real time temperature reduces risk

The temperature of the brushes says something about the condition of the brushes, whether they wear smoothly and when it is time to change. The temperature of the brushes also gives an indication of a bigger problem: Coal dust from the worn brushes may cover electrical contacts and brushes and cause overlays and fire. In that case, production must be stopped for a long time while expensive equipment, in worst case, the whole generator must be replaced.

Glitre Energi, who owns the power plant, took action to reduce the fire risk. Together with El-Watch, they installed wireless temperature sensors on some of the brushes in Pikerfoss hydropower plant. The small IoT sensors measure continuously and give instant message if something is out of the ordinary.

Jonas Hertel, head of analysis and technical development in Glitre, monitors the temperature of the carbon brushes in the Pikerfoss power plant with Neuron wireless sensors.

This is the brush that transfers power to the generator. The small hole between the copper wires is the point where the temperature is measured with a wireless PT100 sensor.

Leif Haviken points out the "submarine" where the wireless sensors are at work. The picture is taken through the control rooms window. From the drop-shaped hatch to the left, there is a shaft of seven meters down to the generator where the brushes and sensors are located. El-Watch’ guy, Hallvard Helgetun, on his way to inspect the sensors.
Inconvenient access makes it extra relevant to leave the inspection to wireless sensors. Wireless sensors with probe (pt100) sample every third seconds.

The range is impressing

The range is impressive, says the manager of generators in Glitre Energi, Leif Haviken. Although the small Neuron surface temperature sensor sample every third second and have an estimated battery life of 15 years, they still have enough power to deliver the data through concrete and steel.

The sensors are located deep down in the “submarine” from where they wirelessly transmit data through a deep shaft in concrete closed with a steel hatch. The radio signal then penetrates through a window and into the cabinet where the gateway is located. From the gateway, the data are sent to the Neuron Cloud solution. Glitre can see the readings and set alarms in the Neuron dashboard, or they may use our API or MQTT to send the data to another platform.

The graph below shows the real time temperature on three of the brushes installed in the powerplant.

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