Revolutionizing Grid Architecture: A New Paradigm for Resilient, Elastic Distribution Networks
In an era defined by the urgent transition to clean energy and the rapid electrification of transport and industry, the architecture of power distribution systems is undergoing a profound transformation. No longer can grids be viewed as passive conduits delivering electricity from centralized plants to end users. Instead, they are evolving into dynamic, interactive platforms—capable of managing bidirectional flows, integrating volatile renewable generation, and responding in real time to shifting demand patterns. At the forefront of this evolution is a groundbreaking proposal from engineers at State Grid Weihai Power Supply Company in China, who have reimagined the very structure of medium- and high-voltage distribution networks to meet the demands of the new power system.
Published in the January 2024 issue of Shandong Electric Power, a leading Chinese technical journal, the research by Gong Junxiang, Xu Youlin, Zhang Jing, and Xu Chunhua introduces a novel “hierarchical, parallel looped platform-type” distribution network architecture. This design fundamentally departs from traditional radial or open-loop configurations by embracing closed-loop operation across both 110 kV high-voltage and 10 kV medium-voltage tiers—enabled by advanced protection schemes, intelligent soft open points (SOPs), and a honeycomb spatial layout that enhances redundancy, resilience, and local energy balancing.
The implications are far-reaching. As distributed energy resources—such as rooftop solar, wind farms, battery storage, and electric vehicle (EV) charging stations—proliferate, conventional distribution systems struggle with voltage instability, protection coordination failures, and inefficient power routing. The authors argue that the legacy “closed-loop design, open-loop operation” model, once a pragmatic compromise to manage short-circuit currents and simplify relay settings, has become a bottleneck in the age of high renewable penetration and digitalized grid control.
Their solution is both elegant and pragmatic: a layered network where every critical node enjoys multiple power supply paths, faults are isolated within milliseconds without customer interruption, and surplus local generation is consumed as close as possible to its source—first on the 10 kV feeder, then at the 110 kV substation, and only as a last resort transmitted upward to the 220 kV transmission level. This “local-first” energy balancing philosophy not only reduces transmission losses but also minimizes grid congestion and enhances overall system stability.
At the heart of the proposal are two innovative high-voltage topologies for the 110 kV level: the “212” dual-source chain structure and the “323” triple-source chain structure. In the “212” configuration, each 110 kV substation receives two parallel feeders from the same 220 kV upstream substation, operating in a closed loop under normal conditions. A single inter-station tie line—kept in hot standby—provides backup connectivity to neighboring 220 kV zones. Crucially, every line segment and transformer is equipped with instantaneous (non-time-delayed) primary protection, allowing faults to be cleared in milliseconds while the healthy circuit seamlessly assumes the full load. This eliminates the multi-second outages typical of conventional auto-transfer schemes, achieving what the authors describe as “zero-perception” power continuity—a new benchmark for reliability.
The “323” structure takes redundancy a step further. Here, three 220 kV substations each feed two lines into a ring that interconnects three 110 kV substations, with each 110 kV unit powered by transformers sourced from different upstream nodes. This creates a meshed, multi-directional supply capable of withstanding even catastrophic failures—such as the complete loss of one 220 kV station—without interrupting service to end users. Load redistribution occurs automatically via safety automation systems on the 10 kV side, rerouting power through the remaining healthy transformers.
Both configurations are designed to scale into a honeycomb-like spatial pattern, where 220 kV and 110 kV substations form the vertices of hexagonal cells. This geometry is not merely aesthetic; it offers optimal connectivity with minimal infrastructure, allowing modular expansion as load grows. More importantly, it ensures that any substation outage can be managed by transferring its load in equal portions to adjacent nodes—four for a 110 kV station, three for a 220 kV station—thereby preventing cascading failures and maintaining voltage stability.
The upstream 220 kV substations themselves are re-engineered to support this new paradigm. The authors recommend a three-transformer configuration with a 220/110/35 kV voltage profile. The 110 kV bus employs a segmented ring main or double-bus arrangement, operated in parallel to enable looped power flow. Short-circuit current levels are carefully controlled—40 kA at 110 kV, 31.5 kA at 35 kV—to ensure equipment survivability while allowing closed-loop operation. Calculations show that with typical transformer impedances (e.g., 14% high-medium, 24% high-low), parallel operation keeps fault currents well within design limits.
Equally transformative is the redesign of the 110 kV substation itself. For the “212” high-voltage input, the team proposes using three split-winding transformers (63/40/40 MVA rating, split factor Kf=4). Each transformer’s two 10 kV windings feed separate bus sections, which are then interconnected via intelligent SOPs. These solid-state power electronic devices do far more than just link buses—they actively manage power flow, balance loading between transformers, provide dynamic reactive power compensation, and, during faults, isolate sections faster than mechanical breakers can operate. In the event of a transformer outage, SOPs can even emulate virtual synchronous generators, providing voltage and frequency support to maintain stability until backup paths are engaged.
For the “323” configuration, conventional two-winding transformers are used, but the 10 kV bus groups are still tied together with SOPs featuring bypass functionality. This allows, during severe contingencies, the direct connection of a de-energized bus section to a healthy feeder via the SOP’s mechanical bypass switch—ensuring uninterrupted supply while preserving the benefits of electronic control during normal operation. The authors calculate that a 15 MVA SOP rating is sufficient to handle both steady-state power transfer and transient support needs.
The medium-voltage layer—10 kV—is where the vision becomes tangible for end users. Here, the “212” dual-source ring structure mirrors the high-voltage approach: two feeders from the same 110 kV bus group form a closed loop, serving a cluster of loads and distributed generation. Crucially, these loops from different substations are interconnected via SOP-equipped tie lines, creating a truly meshed medium-voltage network that transcends traditional substation boundaries.
This breaks the century-old paradigm where medium-voltage circuits are electrically isolated by transformer groups to limit fault currents. With SOPs acting as controllable, fast-acting barriers, the entire 10 kV network can operate as a unified, flexible platform. During normal operation, SOPs optimize load sharing across four feeders (two from each substation) and maximize local consumption of solar or wind output. During a fault—say, a cable failure in one segment—instantaneous protection clears only the damaged element, while SOPs redistribute power to maintain supply to all customers. In extreme cases, such as the loss of an entire 110 kV substation, the SOP bypass function allows the healthy side to pick up the full load of the affected side.
Technical specifications are meticulously detailed: 400 mm² copper cables, 480 A continuous current rating, 8.3 MW per dual-feeder loop, and a 2 MW cap per ring main unit or switchgear bus section. These values reflect a balance between thermal capacity, fault current management, and practical urban planning constraints.
The broader significance of this work lies in its systemic coherence. Every layer—from 220 kV down to 10 kV—is redesigned not in isolation, but as an integrated whole. The result is a distribution grid that is simultaneously more robust (able to withstand multiple failures), more elastic (able to adapt to changing generation and load patterns), and more efficient (minimizing unnecessary power transfers). It provides the physical and control infrastructure necessary for advanced applications like transactive energy, virtual power plants, and real-time grid-edge orchestration.
Critically, the authors ground their vision in engineering reality. They address short-circuit current limits, transformer impedance selection, reactive power compensation needs, and voltage deviation tolerances—all with concrete calculations and equipment recommendations. This is not speculative futurism; it is a practical roadmap for grid modernization that utilities can implement incrementally.
As the world races toward net-zero emissions, the distribution grid is emerging as the critical battleground. Transmission systems may move bulk power over long distances, but it is at the distribution level that the energy transition is lived—where solar panels feed homes, EVs charge overnight, and factories run on green electrons. The architecture proposed by Gong and his colleagues offers a compelling answer to the central challenge of this era: how to build a grid that is not just cleaner, but smarter, tougher, and more responsive to the needs of a dynamic energy ecosystem.
By replacing fragility with redundancy, passivity with intelligence, and isolation with interconnection, this new paradigm could well define the backbone of the 21st-century power system. And while the initial deployment may be in Shandong Province, the principles are universally applicable—offering a template for grid operators worldwide grappling with the same disruptive forces of decentralization and decarbonization.
Authors: Gong Junxiang, Xu Youlin, Zhang Jing, Xu Chunhua
Affiliation: State Grid Weihai Power Supply Company, Weihai 264200, China
Journal: Shandong Electric Power, Vol. 51, No. 1, 2024
DOI: 10.20097/j.cnki.issn1007-9904.2024.01.005