The California Energy Commission is proposing to increase transmission line capacities by installing new conductors that carry more than twice as much current as existing conductors of the same size.
The advanced conductors, known as high-temperature low-sag or HTLS, have a higher core tensile strength than existing aluminum-conductor steel-reinforced conductors, or ACSR.
HTLS has many advantages over ACSR, the CEC said. HTSL conductors can withstand continuous temperatures of 150 to 210 degrees Celsius, whereas ACSR conductors peak around 100 degrees Celsius. HTSL conductors also sag less than ACSR, reducing the risk of wildfires, and experience less line loss, which increases the overall efficiency of the grid.
However, the CEC said utilities still primarily use traditional ACSR cable technology for their transmission lines, even though HTLS conductors have been on the market for about 10 years. HTLS is more expensive than ACSR, but new material-engineering developments associated with HTSL have led to potential commercialization of the conductors, the commission said.
Replacing existing ACSR conductors with HTLS conductors can increase transmission line capacities, thereby reducing the need to build new transmission towers and other more transmission infrastructure, the CEC said. Furthermore, continuing decreases in costs for HTLS conductors will shorten the length of their payback period, making them a more competitive option.
Transmission-line conductor failure caused four ignitions in Pacific Gas & Electric’s territory from 2015 to 2017, making it the second-leading cause of transmission-induced ignitions in the investor-owned utility’s territory.
HTLS conductor replacement could be a part of the CEC’s Electric Program Investment Charge program. The commission on June 28 reviewed a research road map for the EPIC program, which focused on research and development of renewable-energy generation technologies for utility-scale applications.
The road map will be used to strategically target future EPIC investments and provide optimal benefits to IOU electric ratepayers, the CEC said.
At the workshop, the CEC reviewed eight possible research and development areas for future EPIC funding, including energy storage, solar, offshore wind, land-based wind, bioenergy, geothermal energy, small hydropower, and grid integration.
In the grid-integration research area, the CEC is looking to install more smart inverters. Smart inverters could allow for more distributed energy resources while providing operators with access to energy data in real time.
“To integrate the power from many renewable sources onto the grid, the electricity produced by renewables must pass through an inverter to match the voltage and frequency of power on the grid,” the CEC said. “Smart inverters can allow data to be transferred faster and identify failing equipment.”
Smart inverters are connected to the internet in order to increase data transfer speed, which could mean an increase in cyberattacks on the grid. To mitigate cyberattacks, algorithms could be used in the smart inverters. The algorithms would monitor the grid and provide advance warning to a utility operator of a possible emerging attack, according to scientists in Lawrence Berkeley National Laboratory’s Computational Research Division.
“There are laws that govern the way the power grid operates from a physical perspective,” Berkeley Lab cybersecurity expert Sean Peisert said. “So we leverage those insights to understand the ways in which hackers might attempt to do something to the grid.”
“If an attacker tries to manipulate the settings in a number of photovoltaic inverters, we’ll observe these manipulations, then identify the settings in PV inverters that have not been hacked, and finally, dispatch the appropriate settings to the inverters deemed safe in order to counter that attack,” researcher Daniel Arnold said.
The CEC and the California Public Utilities Commission in 2013 formulated the Smart Inverter Working Group, which says smart inverters are an important technology that can mitigate the impact of heavy penetrations of distributed energy resources. However, the group is currently considering additional inverter functionality that may or may not require communication with the grid.