Analysis of Transient Voltage Protection in an 11 kV Protection Scheme: TVS Diode-Based Detection Technique

Transient overvoltages are primary cause of insulation stress, nuisance trips, misoperation of protective relays, and accelerated aging in medium-voltage (MV) networks. Analysis of transient voltage phenomena in an 11 kV distribution environment and development of a TVS (Transient Voltage Suppressor) diode-based detection technique that complements standard surge protection (e.g., metal-oxide varistors, gas discharge tubes) and conventional protection schemes (overcurrent, earth fault, distance, differential) is covered in this paper. The proposed approach uses a high-impedance, galvanically isolated measurement path and TVS diodes in a low-energy, secondary detection channel to reliably flag fast-rising transients (e.g., lightning-induced surges, switching events) without imposing additional stress on primary equipment insulation. The architecture integrates three cascaded domains: transformer‑based galvanic isolation, signal conditioning with transient voltage suppression (TVS) clamping, and asynchronous comparator thresholding. Simulation results confirm that the SMBJ6.0A TVS diode enters avalanche breakdown within picoseconds, while the TLV2372D comparator produces sharp digital transitions with sub‑microsecond propagation delay. Although theoretical hardware contributions yield a response latency of ~1.5 µs, system‑level simulations demonstrate a measured response time of 9 μs, dominated by transformer and rectifier dynamics. When interfaced with microcontroller hardware interrupts, the additional MCU latency of 0.5 μs is negligible, resulting in a total trip time of 9.5 μs. These findings validate the superiority of hardware‑driven detection over software polling, offering deterministic, ultra‑fast protection suitable for breaker trip signaling in high‑voltage substations.