From the earliest electric power systems until today, distribution lines have been designed and constructed solely to transfer power from providers (ex: host utility substations) to customers (ex: residences, businesses). This Point A to Point B design creates a challenge when utilities must integrate power from distributed renewable energy sources, such as rooftop solar. Distributed renewables require that power be transferred both to and from electric warehouses (substations, presently) because power is created at various points along the distribution line.
As the electric power grid evolves, distribution lines need to be converted to electric serviceways that optimize the use of renewable energy provided by rooftop solar and other distributed renewable energy 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 superhighway with on and off ramps.
Once electric serviceways are in place, power 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 power.
This will not require a total overhaul of distribution lines; instead, new components will be added to the existing lines to modify them. Let’s take a closer look at three updates to distribution lines that will be necessary for a full conversion to electric serviceways: enhancing impedance to optimize power flow, implementing voltage control modules to boost serviceway efficiency, and developing advanced modeling to modernize power distribution. We’ll also explore the benefits of electric serviceways.
Update 1: Enhance Serviceway Impedance to Optimize Power Flow
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 creating and installing high-current distribution-class series capacitors (D-Caps), serviceway impedance will be reduced. Prescient is currently in the process of developing D-Caps, so contact us if you have questions about these innovative devices.
Once inserted in distribution lines, D-Caps can be activated to reduce the impedance of serviceways, thereby optimizing power 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: Implement Voltage Control Modules to Boost Efficiency
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 sensitivity with maximum and minimum voltage 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.
Each VCM will monitor and control serviceway voltage by optimizing reactive power 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 power 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 maximum and minimum voltage 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 Serviceway Modeling to Modernize Distribution
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.
Serviceways Aid the Distribution of Renewable Energy
Once these new technologies have been developed and applied to traditional distribution lines, the 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 power from location to location. Power 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. Serviceways can easily handle the full rated capacity of the line, including energy from renewable energy sources.
Once D-Caps and VCM designs are optimized, models are updated, prototypes are fabricated, and high power testing is completed, a demonstration serviceway can be operational as soon as 2024.
Electric serviceways will be a game changer for the electric power industry. If you’d like to learn more about electric serviceways, or consider converting your distribution lines, contact us. We’d love to discuss the opportunities and advantages at greater lengths with interested parties.
To learn more about Prescient’s recommendations for preparing transmission lines for distributed renewables, check out our blog on electric powerways.