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Updated Distribution Lines for Renewables: Electric Serviceways

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Tony Sleva's picture
President Prescient Transmission Systems

Tony Sleva is president and co-founder of Prescient Transmission Systems, where he provides risk assessments and innovative solutions for updating the electric power grid. Tony has more than 50...

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Distribution lines have traditionally been designed and constructed to transfer energy from providers, host utility substations, to customers, residences and businesses. This design creates a challenge when utilities must integrate energy from distributed renewable energy sources, such as rooftop solar. Because distributed renewables create energy at various points along a distribution line, they require that energy be transferred both to and from electric warehouses (future substations with added components).

As the electric power grid evolves, distribution lines need to be converted to electric serviceways that optimize the use of renewable energy provided by distributed sources. This innovation will facilitate the transfer of excess renewable energy while providing constant voltage at all customer locations. Serviceways are the way to convert the grid from a series of one-way roads to a highway with many on and off ramps.

Once serviceways are in place, energy flow can be from homeowners to electric warehouses during the day, and from electric warehouses to homeowners at night. To accommodate this change in operating conditions, host utilities need to develop new components and methods for distributing electric energy.

This will not require a total overhaul of distribution lines; instead, new components will be added to the existing lines to enhance them. Three updates that will be required for a full conversion to electric serviceways are:

  1. Reducing impedance to optimize energy flow.
  2. Installing voltage control modules to boost serviceway efficiency.
  3. Developing advanced modeling to modernize energy distribution.

Let’s take a closer look at these three updates to explore the benefits of electric serviceways.

Update 1: Reduce Serviceway Impedance

Serviceway impedance must be optimized to facilitate the transfer of small scale renewable energy. The impedance of distribution lines is a fixed value that is a function of wire size and line length.  By designing, manufacturing, and installing high-current distribution-class series capacitors (D-Caps), serviceway impedance will be reduced. I have envisioned the design for this new technology, and am currently in the process of developing a prototype.

Once inserted in distribution lines, D-Caps can be activated to reduce the impedance of serviceways, thereby optimizing energy flow. When needed, D-Caps can be bypassed to return the serviceway impedance to the initial value. D-Caps will be pad-mounted, 1.2 KV, 600 amp components, and will be located at several locations along a serviceway.

Update 2: Install Voltage Control Modules

Next, voltage control must be addressed. Even with optimized serviceway impedance, voltage drop from the host substation to the furthermost homeowner can be up to 5%. Traditional distribution line voltage variations are illustrated in figure 1.

In the figure, you can see voltage variations at four nodes along a distribution line. This figure displays node voltage for every hour for one year. The nodes are located at progressively further distances from the electric warehouse. The voltages displayed in this chart range from 95% to 102.5% on an axis that ranges from 94% to 103%.

To address this wide range in voltage variation, new serviceways will have voltage control modules (VCM) installed. VCMs will always maintain serviceway voltage within ±0.5% of rated voltage. VCMs will be 15 KV, 2400 KVA units that are assembled using step down transformers, silicon controlled rectifiers (SCRs), capacitors, inductors, and microprocessor-based controllers. I’ll share more about VCMs in a future article on Energy Central.

On an electric serviceway, each VCM will monitor and control voltage by optimizing reactive energy flow. VCMs will respond quickly enough to counteract voltage variations when renewable energy sources start or stop producing energy. If, for example, a cloud obscures the sun and energy produced by rooftop solar panels drops, VCMs will immediately react to maintain constant serviceway voltage until the clouds pass.

Once a distribution line has been converted to a serviceway, voltage variations will be significantly smaller, as shown in figure 2. Just like figure 1, figure 2 displays voltage variations at four nodes along a distribution line, with 24 hourly calculations performed daily for one year. Unlike figure 1, figure 2 is displayed on an axis that ranges from 99% to 101%. The range of voltages displayed in this chart ranges from 99.5% to 100.5%.

Update 3: Develop Advanced Serviceway Modeling

With today’s technology, models of distribution lines could be significantly improved. As distribution lines are converted to serviceways, models must be updated to ensure accuracy and consistency in voltage variation calculations. Models will also be used to determine the optimal location for VCMs along the serviceways.

Serviceway models are mathematical representations of host utility electric warehouses, serviceways, renewable energy sources, and customer loads. Because renewable energy sources and customer loads vary minute to minute, serviceway models must be dynamic with variables for time of day, season of the year, renewable energy sources, and customer load types. Model inputs will be defined and selected by the user, with default values available for initial setup.

Results will be displayed on voltage sensitivity charts, like figures 1 and 2, where nodes will display the location of renewable energy sources, customer loads, VCMs, etc. Additionally, models will provide a list of the five highest and five lowest voltage calculations at each node. Users will have the ability to perform detailed analysis of any hour of any day in the model.

Electric Serviceways Will Efficiently Distribute Renewable Energy

Once these new technologies have been developed and applied, distribution lines will be converted to electric serviceways. Serviceways will help prepare the grid for distributed renewable energy sources by allowing for an easier transfer of energy from location to location. Energy flow will be optimized everywhere. Serviceway voltage will be controlled to a very tight tolerance. This will allow utility companies to optimize their systems and reduce expenditures on new equipment.

A demonstration electric serviceway can be operational as soon as 2024, once D-Caps and VCM designs are optimized, models are updated, prototypes are fabricated, and high energy testing is completed. Electric serviceways will be a game changer for the electric power industry.

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Dan Greenberg's picture
Dan Greenberg on Apr 15, 2021

Interesting post Tony! I'm wondering how your VCMs differ from the distributed, networked reactive power solutions offered by companies like Varentec?

Tony Sleva's picture
Tony Sleva on Apr 22, 2021

Both solutions address the same concern.  The VCMs that Prescient is proposing are utility grade components, 1500 KVA to 2500 KVA assemblies.

Bruno ANDRE's picture
Bruno ANDRE on Apr 19, 2021

Interresting analyze but i think you haven't consider a more simple solution alreday available : The Dynamic Line Rating (DLR); 

As long as the vaste majority of Distribution lines are overhead, the influence of wind, solar and all climate elements is hugh and is a way to optimize energy transfer on them; The use of dedicated sensors coupled with some calculation rules  make dynamic power transfer adjustment possible and also reduce the line ageing and black-out risk.

Same concept is already available on HV since more than 10 years and many suppliers have such package in their catalogue

Tony Sleva's picture
Tony Sleva on Apr 22, 2021

Transmission system operation is much different than distribution system operation. Electric serviceways will replace distribution lines.  Dynamic Line Rating devices are used with transmission lines to optimize power transfer from central power plants to load centers.  Dynamic Line Rating for distribution lines is very difficult ti implement.  On transmission systems, generation can be reallocated to optimize the cost of energy.  On distribution lines, power flows are a function of renewable energy, customer demand, and source substation location.  A much different ballgame.

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