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RTU’s (Remote Telemetry Units) have long been used in the energy sector for managing power distribution. The Power Grid is a geographically dispersed system that requires RTUs for local control and remote asset monitoring for the grid operators. RTUs are the eyes and ears of the operations team.

As the energy industry diversifies, often by connecting smaller power generation assets to the main grid, a problem has arisen. Traditional RTUs, usually used to monitor points where large generation plants connect with the grid, are not easily transferred to a more diverse range of assets. In this blog, we look at how operators can select smaller, more economical RTUs that suit the needs of a diversified energy market.

Diversification of the energy sector is a double-edged sword. On the one side, there is a huge benefit in the reduction in reliance on fossil and nuclear fuels as well as the creation of market opportunities for new investors and new consumers. On the negative side, many of the alternative energy sources do not have the same level of control as traditional plants. Solar power plants and wind turbines can make some adjustments to output by tilting panels or feathering blades, but both are at the mercy of the environment and can undergo large, sudden changes in ability to supply. This requires precise monitoring and control at every interconnect to the grid, increasing the demands for data by the grid’s operational systems.

Smaller RTUs can meet this challenge, and more. Here, we answer some of the most common questions design engineers in the energy sector will need to have answers for.

 

What impact have renewable power generation plants had on existing systems?

Wind, solar, hydro, biomass and wave solutions for power generation have all added significant sources to traditional networks in recent years. In most developed countries around the world, renewable energy now produces a growing proportion of the total energy output - recently exceeding 20% for the first time in the UK. Compared to large coal, gas and nuclear plants where a single point of entry to the system carries the bulk of supply, operators now need to manage a much wider portfolio of assets with much smaller demands at each location. This has resulted in a need for smaller RTUs that are just as capable as existing equipment and sufficiently rugged to be field mounted, anywhere that the power gird reaches.

Has the power industry always used RTUs?

Yes, the power industry has always used RTUs to manage the power grid, however, these were traditionally designed to suit large interconnection points. For the newer assets, a smaller RTU, with similar functionality, is required.

Why is there growing demand for smaller, smarter RTUs?

A typical power station is around 1 Gigawatt (1GW). The RTUs to monitor the connection between these facilities and the power grid are not suitable for the vast range of smaller, renewable options. At these smaller power connections to the network, the asset monitoring and control RTUs used for a full-scale power distribution would be overkill. We have seen growing demand for our RTUs which can be cost effectively deployed on these assets.

TBox RTUs have been used for decades to monitor power consumption at critical assets. One of the earliest uses of these products was to monitor power consumption and battery backup at telecommunications towers. RTUs allow telecommunications operators to monitor the incoming supply from the main grid and any local backup generation or backup storage at their facilities and, in the event of a grid failure, help them decide what actions need to be taken to ensure continued operations of the critical telecommunications network.                                                                                                                                                            

Using an RTU in the renewable sector

Our TBox RTUs are being used on wind turbine towers in Greece, monitoring production, rather than consumption, at each tower. These kinds of RTUs, even with a small footprint, have enough capacity to manage the limited number of I/O points that are required at each power generation tower. You will find some more of our case studies here.

TBox has also been used on 30MW solar power plants in France and on grid connected Solar Arrays in Australia, producing as little as 250kW. 

4) What is the RTU responsible for on-site?

At small sites, the RTU is both the site controller and the site communications gateway. The RTU collects data directly, and can also provide a secure VPN, to other devices that may be operating on site, such as PLCs. The collected data is then made available to the grid operators who can issue commands back to the RTU to regulate the station.

With its ability to report alarms and historical data via email, SMS, FTP and MQTT, a TBox is the ideal choice for small power plants that need to manage both physical assets and wider communications demands.

5) What about non-renewable fuelled gensets?

Remote communities around the world often rely on small diesel generator sets (gensets) for their power, and historically, they have used manual, often irregular, monitoring schemes. With a growing focus on the environment, RTUs are now being added to monitor not only genset status, but emissions.

In Asia, our TBox RTUs are being used to monitor diesel generator systems 24/7, providing emissions data to a central reporting system. The data can be accessed by both government environmental agencies and the wider community through an Air Quality Index app. In addition, the RTUs assist in asset management by monitoring the generator health; tracking exhaust temperatures, heater exchange throughput and oil quality as part of proactive maintenance measures.

6) Can RTUs be used with "non-grid" power networks?

Yes, hospitals, universities, airports and railway lines often have their own internal power network that needs management. They have the same control and communications requirements as the main grid. Most importantly, these large facilities are typically critical assets that must always remain operational, so reliability and resilience to faults are key requirements.

Electrified railway networks, for example, source their main supply from the grid and then distribute the power along the railway network. The rail network is almost as geographically dispersed as the power grid, covering the same territory, but following only the railway lines. The demands on RTUs used in the Railway Network have many similarities to a Power Network RTU - they are exposed to remote environments, occasional voltage spikes and must be able to store, manage and report large volumes of data.

7) Are smaller RTU’s resilient to the network environment?

Yes, an important feature with any RTU is resilience to the site environment. That is especially relevant to the power sector where renewable resources are often in remote geographical areas. It takes time to travel to remote locations to perform repairs, so RTU’s must resist damage to reduce the number of callouts. The device is equipped with layers of redundancy so that even if a major event damages one piece of the system, the RTU will continue to operate.

Ovarro RTUs can operate in these rugged conditions at temperatures between -40°C and +85°C and have up to 5,000V of isolation on I/O cards to protect the CPU from spurious electrical events.

8) What if the power generator fails?

Even when a generator is unable to supply power, the main grid operator still needs to have visibility of what is happening on site. It could be as simple as a lack of resources; no fuel, no sunshine, no wind; or a catastrophic failure such as an onsite fire. Any available information is important to the ongoing management of the network. It is the responsibility of the RTU to provide insight for the grid operators regardless of the state of the generator itself.

RTU’s have always operated in areas where power is either unreliable or unavailable. Each Ovarro RTU draws only a few Watts and can easily run off a solar power system or even a small and insignificant feed from the site generator. The RTUs also incorporate a battery management system and can run off a small rechargeable battery for extended periods.

9) Can RTUs act autonomously?

Yes, RTUs are fully programmable and can carry out local control algorithms under the supervision of central operators or perform control fully autonomously. This is a core design criteria as remote communications links are often unreliable. RTUs must be able to continue to operate locally when there is no remote connectivity.

In remote locations, or during emergencies when communications systems are under pressure, fail or are limited, RTUs will maintain local control and historical data storage.  RTUs add resilience to the control network by moving the real time control locally where it cannot be impacted by threats to the remote communications links.

10) How will RTUs evolve in the future?

The trend in modern information collation is to push some of the data management back out to the field. For many years there has been an ongoing trend in increasing the volume of data collected from the field. If you need a field hardened PC, or “edge computer” for monitoring electrical current, temperature, emissions, power and asset health, then you need an RTU.

RTUs are specifically designed to perform local control and gather and relay information to SCADA or the cloud, providing operators with the information they need for efficiency management and asset management, in addition to real time control.