IEEE Power & Energy Magazine - March/April 2020 - 49

were installed on the 63-kV grid in southwestern France as
a research project. The system used a Wi-Fi communication system between the onsite modules and a 3G network
linking the site to a web-hosted platform installed in RTE's
regional control centers.
Directed by a dispatcher in a control center, commands
are sent to a master controller that has the desired level of
impedance injection. Several operating modes can be selected
to reach maximum flexibility:
1) a fixed predefined current threshold for automatic impedance injection
2) an operator-selected predefined response for different automatic impedance injections based on the line
loading
3) direct manual commands from the dispatcher to inject
impedances.
For instance, it is possible to program all of the modules to
inject impedances when the current level reaches 600 A and
have a scalability programmed scenario where 30% of the
modules inject impedance when currents reach 300 A, while
another 30% make injections when currents reach 500 A and
so on. Alternatively, the operator can exercise complete control over the number of injected modules.

A Demonstration Project in Operation
After tests conducted in 2017, RTE installed a demonstration line in 2018 with 102 SmartModules (34 per phase) on
the Dantou-Villeneuve 63-kV circuit in southern France to
resolve post-contingency overload situations. The system
has the ability to modulate approximately 10% of the total
line impedance.
Line power-flow control management leads to optimized
grid usage in real time and represents a flexible solution to
local uncertainty. The SmartModules shown in Figure 6 offer
several potential economic benefits through their operational
flexibility, possible reuse and relocation, and
low initial capital-expenditure investment
that provides easily scalable solutions if system needs change in the future. The installation requires a short line outage; when helicopters are used, the work can be completed
in fewer than 10 min per module. SmartModules are designed to last for at least 20 years
(including the controls and power electronics)
with limited preventative maintenance (visual
evaluations during normal line inspections at
least every five years) and, if needed, repairs.

the flows on the lines. The devices have been deployed on
line conductors at 63 kV in the demonstration project, but
installations of up to 400 kV are possible. The installed project utilizes "push-mode" regulation, which increases the
line's impedance.
New power-flow modulation FACTS devices use a similar compact-technology approach. They can be installed in
substations and offer push and pull operation modes (by
increasing or decreasing the impedance of the circuit). Compared to series reactors and phase-shifting transformers,
the new FACTS equipment promises an improved flexible
operation and is the economic choice for some applications
that require medium-size flow modulation.

Large Batteries for Grid Purposes
Subtransmission Grid Areas
With Renewable-Generation Congestion
An increasing number of 63- and 90-kV subtransmission
areas are or will be congested in the near future due to
large volumes of renewable generation. This is not by accident; during the past 10 years, negotiations among regulatory authorities, utilities, and energy-industry stakeholders
led to many regional renewable-energy development plans.
The plans facilitated grid development through shared costs
among new generation owners, in particular the new players in renewable energy. That led to a belief, widely shared
among stakeholders in France, that the grid-expansion plans
would be too expensive to accommodate 100% of the renewable generators' nominal power. Thus, it was decided to
size the overall grid to accommodate 70% of the renewable
sources' nominal power ratings. This may lead to localized
renewable-generation curtailment when all of the renewable
generation in a relatively small area is producing close to
100% of its nominal capacities.

Applications and Next Steps
A solution is available for grid planners to
resolve overloads and rapidly adapt the network by redirecting the power flow instead of
building new lines. Similar to the DLR solutions, SmartModules are a way to develop
flexibility in grid operation by influencing
march/april 2020

figure 6. SmartModules installed on a transmission line. (Source: RTE; used
with permission.)
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IEEE Power & Energy Magazine - March/April 2020

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