Will The Implementation of Dynamic Line Rating Technology Aid In Increasing Transmission Conductor Capacity?
Evaluating the condition of overhead conductor connectors should play a vital role in determining the answer to that question.
As you undoubtedly know, the North American electric grid has grown to approximately 600,000 miles of transmission. of which 240,000 operate at high voltages (i.e., >230 kilovolts, kV). Most of the North American electrical grid was built post World War II and 70% of transmission lines are 40 years or older. Empirical data indicates average connector service life is 40-70 years, provided they have been installed properly and the circuit is operated within the design parameters originally assigned for a maximum continuous conductor temperature of 75°C (167°F).
After 1970, single-stage connectors were introduced for use on transmission lines using ACSR conductor. These connectors were designed for a maximum conductor temperature of 75˚C. To prevent annealing and loss of tensile strength, these types of connectors should not operate above 93°C. Transmission lines using ACSS conductor built before the year 2001 used mineral oil based inhibitor, which itself has thermal limitations of 163˚C. With age, these elements impact system efficiency and safety.
The most common causes of overhead conductor failures and outages are the degradation of splices and connectors due to corrosion, fatigue, thermal cycling, or improper installation. Dynamic line ratings and methodology will allow utilities to increase ampacity on lines when the conditions of wind, ambient temperature, and nighttime radiation keep the conductors at a lower temperature to maintain sag. However, these conditions have virtually no effect on the electrical interface deep within the connector. Studies indicate the simple fact that an increase in conductor temperature will lead to accelerated aging and connector degradation at the electrical interface. This is particularly concerning given the increasing power demand and the fact that a significant portion of the electrical grid is made up of aging infrastructure. Neglecting to address the connectors in the process will lead to catastrophic failures, line-down incidents, and unplanned outages.
The importance of considering the condition of connectors on overhead conductors in the evaluation process cannot be overstated. For instance, in a 2021 Wildfire Mitigation Plan report from a major utility, 37% of wildfire ignitions resulted from Transmission line failures of conductor and splice/clamp/connectors in High Fire Threat Districts. And reports from other utilities show similar findings. These failures are often the result of corrosion, fatigue, thermal cycling, or improper installation.
Therefore, it is crucial to proactively assess and address the condition of connectors to ensure a seamless transition and prevent potential failures and disruptions in the electrical grid. By implementing measures such as the installation of Engineered, Electrical/mechanical Shunts (EEMS), which can enhance the capacity and reliability of transmission lines, we can mitigate the risks associated with aging infrastructure and increasing power demand.
In conclusion, the evaluation process for transmission lines should include a thorough assessment of overhead conductor connectors, considering their impact on system efficiency, safety, and capacity to ensure the reliable operation of the electric grid and minimize the risks of connector failures and subsequent disruptions. Therefore, with proper measures in place, Dynamic Line Rating technology has the ability to provide a positive outcome.