Benefits of Using Sub-1GHz Connectivity for Grid Asset Monitoring, Protection and Control

Increased demand for health and condition monitoring of remote power distribution and automation assets to oversee primary equipment health and condition monitoring to optimize power management; resource allocation; fault location, isolation, and service restoration (FLISR). Remote monitoring of the grid helps to achieve efficient operation of the grid, reduce the number and duration of outages, and minimize losses.

The evolution of the grid requires wireless connectivity to be added to existing wired connections for asset monitoring and control. The main factors for increasing wireless connectivity include:

Adopt a decentralized microgrid model with distributed energy resources for use with traditional generation, transmission, and distribution.

Increased demand for health and condition monitoring of remote power distribution and automation assets to oversee primary equipment health and condition monitoring to optimize power management; resource allocation; fault location, isolation, and service restoration (FLISR). Remote monitoring of the grid helps to achieve efficient operation of the grid, reduce the number and duration of outages, and minimize losses.

Data analysis of grid assets can help operators identify faults quickly, while enabling predictive maintenance of major equipment, which is almost non-existent today. Determining which specific wireless technology to use, such as Sub-1 GHz, Bluetooth® Low Energy, Wi-Fi®, or multi-standard protocols, depends on data, bandwidth, distance between nodes, number of connections required, available power, and factors such as the required response time.

In grid assets, nodes in remote locations like fault indicators need to be connected to a data collector, as shown in Figure 1, for automatic data exchange with a centralized system. In such applications, wireless communication such as sub-1 GHz is chosen because of its wide range (ranging from tens of meters to thousands of kilometers) and very low power consumption (average current in the tens of microamps) . Sub-1 GHz is also an easy-to-configure, low-cost technology when adding multiple nodes in the field, using a common collector to fetch data on demand from remote devices.

Benefits of Using Sub-1GHz Connectivity for Grid Asset Monitoring, Protection and Control

Figure 1: Using Sub-1 GHz to connect a fault indicator to a data collector

Adding sub-1 GHz connectivity involves two-way communication with the data collectors in the star network. Nodes are configured to have faster response times to communicate failure information, communicate failure information including location with minimal delay, thereby providing faster recovery or self-healing capabilities.

Sub-1 GHz offers these advantages over other wireless connectivity solutions, including 2.4 GHz Bluetooth Low Energy communication:

• Longer communication range due to the use of lower transmission frequencies and data rates, as receiver sensitivity is a function of data rate. As a general rule of thumb, reducing the data rate by a factor of four can double the communication range.

• The ability of low frequency (longer wavelength) radio frequency (RF) waves to penetrate obstacles enables sub-1 GHz operation in a variety of environments.

• Low duty cycle allowed in sub-1 GHz RF regulations to reduce interference.

One of the common grid terminal equipment using sub-1 GHz connections is a fault current indicator (FCI) for medium and high voltage transmissions. The FCI is powered by harvesting power from the load current. Available for acquisition currents in the range of tens of microamps. The biggest challenge in integrating an FCI connection is whether it will work properly when the power is harvested when there is no load current to harvest the power. In addition, the requirement to operate in a wide range of environmental conditions (such as line of sight, obstacles, etc.) also limits the use of traditional capacitors or some batteries. Therefore, for RF communication, it is crucial to simplify data transfer to reduce current consumption, and this is achieved by optimizing the communication mode between nodes and collectors.

There are two modes for managing data transmission (TX) and reception (RX): beacon mode and non-beacon mode. In non-beacon mode, the sensor node is always in receive mode, as there is no defined time when the data collector can communicate with it, which translates into higher current consumption (~5 mA). In addition to optimizing transmit power levels based on distance between nodes, beacon mode communication (see Figure 2) is best suited as it enables duty cycling between wake-up and sleep modes on sensor nodes to aid in the transmission and reception of to save power when the unit is turned off.

Benefits of Using Sub-1GHz Connectivity for Grid Asset Monitoring, Protection and Control

Benefits of Using Sub-1GHz Connectivity for Grid Asset Monitoring, Protection and Control

Figure 2: Beacon Mode Communication

The beacon mode consists of broadcasting a beacon from the data collector at fixed time intervals, which all sensor nodes can receive. It synchronizes communication between individual sensor nodes and collectors. Sensor nodes only wake up when they receive a beacon, and deciphering the beacon provides information to the sensor if the collector wants to send or receive data before the next beacon. This process allows the sensor to switch to sleep mode during transitions, which is ideal for fault indicators.

TI reference design for adding connectivity to FCI

Designers face numerous hardware and firmware challenges when integrating sub-1 GHz connectivity into FCIs. The Internet of Everything Grid Reference Design: Using Sub-1 GHz RF Connection Fault Indicator, Data Collector, Mini-RTU Displays:

The integration of low power radios involves:

• Network settings.
• Use beacon mode for sending and receiving.
• Data exchange including configuration and over-the-air firmware upgrades.
• Fault identification and data communication.
• How to minimize power consumption between fault indicators and data collectors by:
• Current consumption data for the US (915-MHz), ETSI (868-MHz) and China (433-MHz) bands are currently available.
• The RX current is less than 6 mA and the TX current is less than 16 mA (at +10 dBm).
• Ability to achieve an average current consumption of less than 20 μA while implementing a 5 s beacon interval (fault indicator configured in RX mode) in a star network.

This reference design provides a single development environment with code portability to a variety of The connectivity protocol features a ready-to-use, easy-to-update, low-power connectivity solution that helps address the challenges associated with node firmware development.

Sub-1 GHz is a simple, easy-to-use and install cost-optimized method of adding wireless connectivity to existing grid assets, making legacy assets more reliable and providing faster fault response.

Are you doing grid connection work in any form? What challenges are you facing? Please tell us your opinion in the comments section.

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