Understanding Dynamic Line Rating

Most people do not know what dynamic line rating is. This is completely understandable since it is a term used in a specific part of power distribution. What has to be known is that a transmission line’s traditional operational limits are established with the use of rating methodologies for transmission lines that are static. The idea is to select the highly conservative values for operating conditions. As a result, we have static line ratings that are highly conservative. Lindsey Manufacturing Company understood that and created the flagship Lindsey DLR that is dynamic as opposed to static.

A static transmission line rating methodology is automatically dependent on various environmental variables. These are identified in the IEEE standard 738. Such variables are related to how much heat the line generates, the heat that is added to a line and the heat removed. The biggest problem with the system is that environmental variables are fixed. Because of this, there is a really low possibility conductors will sag or will exceed regulatory or operational limits for short time frames. Such methodology practically acknowledges the fact that all transmission line operational limits assigned through static formulas are conservative.

Nowadays, AAR (ambient adjusted ratings) and SAR (seasonally adjusted ratings) can push the line’s static ratings. This is done simply by taking into account the fact there are different environmental conditions that apply at different times. DLR (Dynamic Line Rating) is the transmission line’s real-time or forecasted capacity to carry power. This is based on operating temperature ratings coming in through real-time readings and reports about current weather conditions. DLR stands out as an extension of ambient adjusted ratings. A line cannot have just 4 ratings per year, all based on the season. We now have access to real-time data that can actually offer reliable readings every single hour of the day. The DLR of a transmission line is almost always ten to 25 percent higher than the static rating. This goes to prove how much loss appears when looking at the static reading system.

So many studies were already conducted and showed the fact that there is an additional capacity available. This automatically brings in higher opportunities in trading, congestion mitigation, operations and economic dispatch. At the same time, DLR application is a great tool that improves contingency planning. The lines that have slow load growth are effectively addressed and there is no need to have reconductoring or line upgrades installed. Even if such additions or moves are needed, they happen less often.

Unfortunately, even if there are clear economic advantages, Lindsey’s DLR is still sparsely deployed. This is because of two main reasons. The demand drivers show pretty weak economic rewards in deregulating the transmission environment. Also, the first generation systems that appeared on the market did have different problems the early adopters had to deal with. This discouraged a wider deployment.

The good news is that the new Lindsey Manufacturing DLR generation is close to flawless. The data that is gathered is highly useful in adapting output for the transmission lines.