Low-voltage communication systems in next-generation data transmission networks connect smart meters, feeder controllers, EV chargers, and distributed energy resources; however, the dense topological structure they have and the limited abilities of their endpoints make the direct deployment on quantum hardware be not practical. In order to solve this restriction, this article puts forward a Hybrid Quantum Encryption Scheme for Low-Voltage Systems (HQES-LV), which keeps quantum key distribution on backbone and gateway layers, uses a post-quantum authenticated control plane, and gives lightweight session protection to edge devices by means of risk-adaptive key renewal. A literature-calibrated digital twin is constructed to simulate mixed control, telemetry, and maintenance traffic, along with replay attacks, man-in-the-middle probing, quantum channel degradation, and gateway outages. Result data indicate that in the pressure condition, the HQES-LV can cut control waiting time down to 6.1 ms, hold the possibility of secret information leakage to 0.4%, and make the time of getting back to normal shorter to 6.7 s. Under a 1.2 p.u. load, it maintains 7.3 ms latency and 98.4% session establishment success. When QBER rises to 5.5%, the proposed scheme still preserves 58.9% effective key availability and 96.7% packet delivery. These findings indicate that practical quantum security for low-voltage systems should be realized through hierarchical orchestration rather than endpoint quantumization, and that the combination of QKD backbone supply, post-quantum fallback, and the adaptive session arrangement can provide a path that is more ready for deployment for future electric power communication networks.
