### Industry 4.0 IIoT, Cloud, and Edge Computing for Next-Generation Offshore Wind Farms
Figure 3 illustrates a data-acquisition system designed in the IIoT-Edge computing paradigm. In the figure, IIoT sensors are mounted to measure physical quantities on critical infrastructure. These IIoT devices collect highly granular data at different sampling rates. The data collected from the wind turbines is sent via sub-sea ethernet-based fiber optical cables to the offshore hub (set to house a pico data center (PDC)). A cluster of x86 servers, with diverse computing and memory capacities, are deployed within the PDC. Using the server cluster applications, these computing and memory resources are clustered in a unified server resource pool [32; 59] and allocated to the Edge Computing Platform (ECP) node, virtual Protection, Automation, and Control (vPAC) node, and other IT/OT systems needed to facilitate wind farm operations. Table 1 denotes the data transfer performance requirements and communication modes for different offshore wind farm services. The communication direction is based on the IT/OT architecture of the next-generation offshore wind farm data-acquisition system illustrated in Figure 3. These offshore wind farm services are further described in the following two data transfer scenarios:  
**IIoT-to-ECP node scenario:** The IEC61400-25 wind turbine and metmast sensors collect highly granular analog measurements at a 50 Hz sampling rate and send them to a local data acquisition module [2] within the wind turbine, as illustrated in Figure 3. This local data acquisition module pre-processes these data and facilitates actuation through the local control ensemble in the wind turbine. Further, it sends the sensor data through short-range ethernet-based fiber optic patch cords to the nacelle switch [4]. The nacelle switch communicates with the tower switch, sending the data as ethernet frames to the PDC switch network through the multiplexed subsea fiber optic cable. The PDC switch network then relays the data to the ECP node's MQTT broker [60]. The sensor data received at the MQTT broker are stored in different topics. In this design, it is inferred that some topics contain sub-topics. For instance, the \"_/wind-turbine/temperature_\" topic contains the subtopics \"_/wind-turbine/temperature/gear-oil_\", \"_/wind-turbine/temperature/nacelle/_\", \"_/wind-turbine/temperature/ambient_\", and others, structured hierarchically for efficient data categorization and retrieval. In the ECP node, IoT apps subscribe to the data in the topics using the Apache Kafka message streaming tool to manage high subscription rates. Additionally, the cloud instance applications and the O&M team (enterprise network) subscribe to these data through the wide area network. **IIoT-to-vPAC node scenario:** Current and voltage sensors are mounted on critical electrical components in the wind turbine to collect analog current and voltage measurements at a 20 kHz sampling rate [12]. As illustrated in Figure 3, these current and voltage sensors are connected to differential voltage probes and current clamps. The differential voltage probe and the current clamp send the analog current and voltage measurements to merging units (MU) using short-range ethernet-based fiber optic cables. The MU digitizes these analog current and voltage measurements into IEC 61850-9-2 Sampled Values (SVs) -- according to the SV protocol, as described at [[https://www.typhoon-hil.com/documentation/typhoon-hil-software-manual/References/iec_61850_sampled_values_protocol.html](https://www.typhoon-hil.com/documentation/typhoon-hil-software-manual/References/iec_61850_sampled_values_protocol.html)]([https://www.typhoon-hil.com/documentation/typhoon-hil-software-manual/References/iec_61850_sampled_values_protocol.html](https://www.typhoon-hil.com/documentation/typhoon-hil-software-manual/References/iec_61850_sampled_values_protocol.html)) (accessed on 4 June 2024) -- and then publishes them on the process bus network.