Solutions for load measurement

• Rotor blades are subjected to extreme environmental conditions and strain. Due to the ever-increasing length of blades, growing demands are placed on monitoring.
• The rotor monitoring system (RM-S) from Phoenix Contact continuously monitors the stress and loads placed on the rotor blades.
• In the event that the set limit values are exceeded, alarms are triggered, and operators are always kept informed of the condition of the blades.

The rotor monitoring system (RM-S) measures the behavior under load as well as bending moments in rotor blades. To do so, strain gauges are attached to the inner side of the rotor blades of a wind turbine generator near the base of the blade.

The core element of the solution is the ILC 171 Inline controller from Phoenix Contact. The controller is connected to the sensors in the rotor blades via directly connected Inline modules. To protect the system against surge voltages and lightning strikes, protective devices are installed for the sensor cables, the antenna input of the GSM router, and the power supply. Optionally, a GSM modem can be used to upgrade the system for direct communication. In addition to the controller interfaces, a PROFIBUS or CAN interface can be integrated to establish an internal bus connection.

The controller acquires the signals from the connected sensors. During this quick signal processing, the measured values are filtered and checked for plausibility. Additionally, the measured values are used to determine the minimum, medium, and maximum bending moment, as well as the speed the rotor rotates at. If the set limit values are exceeded, an alarm can be set using freely programmable digital outputs. The processed data is made available simultaneously to the higher-level controller for signal scanning. Through the network, all raw data can be saved in a Microsoft SQL database or in CSV format, to an SD card or an FTP server, and can be evaluated using an independent system. The RM-S also records the present load spectrum. Load spectrum mapping is used for acquiring vibration amplitudes that cause structural damage to the rotor blades over the entire service life. These values make it possible to estimate the remaining service life.

As a retrofit or for new installations

The RM-S can be integrated directly into the electrical design of the system or retrofitted in existing systems. The retrofit version consists of a fully configured control cabinet, which is built into the hub and can be integrated into the controller via the existing interfaces.

Optionally, the data can be directly transmitted to the operator via the GSM modem. In the case of new installations, the required hardware, such as the controller and I/O modules, is integrated directly into the wind turbine generator’s pitch control cabinet. In this case, the software is transferred to the controller using an SD card.