High-altitude low-pressure environments are widely distributed across China’s Qinghai-Tibet Plateau, Yunnan-Guizhou Plateau and other plateau regions, as well as in aerospace, plateau scientific research, mountain wind power, plateau rail transit, plateau power transmission and transformation, and plateau mining machinery applications. As altitude increases, atmospheric pressure and air density decrease significantly, accompanied by a sharp drop in air insulation breakdown strength. For every 1,000 meters rise in altitude, atmospheric pressure decreases by approximately 12 kPa and air insulation breakdown strength drops by 8%–10%. At 5,000 meters, air breakdown strength is only about 50% of sea‑level values, and at 8,000 meters it falls to roughly 35%. High‑voltage power supplies serve as core power components for industrial equipment, power facilities, aerospace systems and scientific instruments in plateau areas. Operating at hundreds to tens of thousands of volts, they are highly prone to corona discharge, partial discharge, insulation breakdown and arcing under low pressure. These phenomena accelerate insulation aging, degrade performance, increase failure rates and may cause permanent damage or fires. The insulation design level and corona suppression capability directly determine operational stability, service life and safety reliability of high‑voltage power supplies at high altitudes. High‑altitude low‑pressure conditions impose extreme technical requirements distinct from sea‑level applications. First, severe insulation challenges caused by reduced breakdown strength. Longer mean free paths enable easier impact ionization, lowering both bulk breakdown and surface flashover voltages. Traditional sea‑level insulation designs suffer insufficient margin at altitude, leading to flashover and breakdown. Insulation must accommodate altitudes up to 5,000 meters and even 8,000 meters with ample safety margin under minimum operating pressure. Second, strict suppression of corona and partial discharge. Corona inception voltage decreases sharply at low pressure. High‑voltage electrodes, terminals, wiring and transformer windings that remain corona‑free at sea level generate intense corona at altitude, producing ozone and nitrogen oxides that degrade insulation while introducing electromagnetic interference. Long‑term corona ultimately destroys insulation. Designs must eliminate visible corona at maximum voltage and minimum pressure, with partial discharge controlled within specified limits. Third, thermal design difficulties due to weakened convection cooling. At 5,000 meters, convective heat dissipation falls to roughly 50% of sea‑level performance. Accumulated heat increases component temperatures, accelerates insulation aging and degrades semiconductors, capacitors and magnetic materials, risking thermal runaway. Thermal solutions must maintain component temperature rises within rated limits even at maximum altitude. Fourth, comprehensive environmental adaptability including wide temperature ranges, strong ultraviolet radiation and low humidity. Plateau regions experience extreme diurnal temperature swings exceeding 30 ℃, with winter lows below −40 ℃ and summer highs above +50 ℃. Intense UV radiation, dry air, sandstorms and frequent lightning degrade insulation materials, causing embrittlement, cracking and performance decline. Materials and structures must maintain stable insulation over long exposure. Fifth, precise design of clearances and creepage distances complying with GB/T 3859.1 and GB/T 16935.1. Above 2,000 meters, clearances and creepage distances require altitude correction. Simple proportional enlargement results in oversized equipment unable to meet miniaturization demands. Optimized calculations based on altitude, voltage class, pollution degree and insulation material achieve compact designs while ensuring safety. Sixth, long‑term reliability and service life requirements. Plateau facilities are remotely located with difficult and costly maintenance. High‑voltage power supplies must achieve an MTBF ≥ 1×10⁵ hours and a design life ≥ 10 years with comprehensive protection against insulation degradation, lightning surges and grid fluctuations. Seventh, enhanced electromagnetic compatibility and lightning protection. Frequent lightning at high altitudes increases induced overvoltages, while corona generates strong electromagnetic interference, threatening both internal circuits and surrounding sensitive equipment. Robust lightning shielding and EMC measures are mandatory. This methodology establishes a complete technical framework covering low‑pressure insulation architecture, precise altitude correction for clearances and creepage distances, full‑chain corona and partial discharge suppression, high‑altitude thermal optimization, multi‑environmental protection and long‑term reliability engineering. Suitable for high‑voltage equipment up to 8,000 meters altitude, it provides standardized design guidelines for plateau power supply development and deployment. Addressing core difficulties including reduced insulation strength, severe corona and poor cooling, the framework adopts an integrated approach: graded insulation media design + altitude correction for clearances/creepage distances + full electric‑field corona suppression + altitude‑adaptive thermal management, supported by multi‑physics simulation and environmental protection. This eliminates traditional limitations of excessive size, weak corona suppression and poor reliability. Eight core design principles are defined: 1. Graded insulation media optimization for low pressure. A multi‑layer system prioritizes solid insulation supplemented by sealed gas and composite structures. Key high‑voltage components such as transformers, reactors, capacitors and busbars adopt high‑strength solid insulation (epoxy, polyimide, PTFE, alumina ceramic, mica) with breakdown strength ≥20 kV/mm. Vacuum epoxy potting eliminates internal voids to prevent partial discharge. Where air gaps remain, sealed SF₆ or dry nitrogen chambers maintain near atmospheric pressure internally, leveraging SF₆’s 2.5× higher insulation strength to reduce size. Surface insulation employs field grading electrodes and high CTI materials (CTI ≥600 V). Graded insulation thickness from high to low voltage homogenizes electric fields. Selected materials withstand −40 ℃ to +125 ℃ with excellent corona resistance, UV stability and low moisture absorption. 2. Precise altitude correction for clearances and creepage distances. Based on Paschen’s Law and national/IEC standards, clearance correction factor Kd = e^(0.000115×altitude in meters). For voltages >1 kV, breakdown voltages at reduced pressure are calculated to ensure clearance withstand ≥1.5× maximum operating voltage. Creepage distances increase by 0.5% per 100 meters above 2,000 meters, further boosted by 20% for DC applications. Rounded electrodes, contoured surfaces and shed structures improve field uniformity and extend creepage within compact dimensions. Finite‑element electric‑field simulation verifies margin and eliminates local overstress. 3. Full‑chain corona and partial discharge suppression. All high‑voltage parts feature large radii ≥5 mm to eliminate sharp corners and concentrated fields. Vacuum impregnation and void‑free potting eradicate internal air gaps. Grading rings, shielding electrodes and spherical corona shields homogenize terminal fields. Strict manufacturing controls remove burrs and defects. Factory testing ensures partial discharge ≤10 pC at 1.1× rated voltage under minimum pressure. Built‑in online partial discharge monitoring provides early warning and automatic voltage reduction or shutdown to prevent progressive insulation failure. 4. High‑altitude thermal design optimization. Heat transfer prioritizes conduction supplemented by radiation, with optimized convection where fans are used. Heat‑generating components bond via high‑thermal‑conductivity interfaces to integrated aluminum heat sinks and enclosure structures. Exterior high‑emissivity coatings (emissivity ≥0.85) enhance radiative cooling. For forced air cooling, high‑static‑pressure fans are derated with ≥2× airflow margin at 5,000 meters, with intelligent speed control. Power components apply thermal derating ≥0.7 at 5,000 meters, keeping junction temperatures below 70% of ratings. Thermal simulation eliminates hotspots. Liquid cooling is adopted for high‑power units to fully decouple from atmospheric convection limits. 5. Multi‑environmental protection for plateau conditions. Wide‑temperature components operate reliably from −40 ℃ to +85 ℃ with cold startup assistance and high‑temperature derating. Metal enclosures and UV‑resistant coatings prevent solar aging; nonmetallic parts use PTFE and silicone rubber. Outdoor units achieve IP65 sealing against sand, dust and moisture with conformal coating and sealed connectors. Multi‑stage lightning surge protection combining arresters, varistors, gas discharge tubes and TVS devices provides low‑impedance grounding paths for lightning energy. 6. Long‑term reliability and lifetime engineering. Aggressive electrical, thermal and insulation derating extends service life. Redundant designs apply to power stages, control power, drivers, sampling and cooling with seamless switchover; N+1 modularity enables maintenance without shutdown. Components undergo strict temperature cycling, burn‑in and vibration screening. Final products complete low‑pressure chamber testing, climate trials and aging validation. Integrated health monitoring tracks voltage, current, temperature, partial discharge and ambient pressure to predict insulation degradation and issue proactive alerts. 7. Electromagnetic compatibility and enhanced protection. Corona suppression at the source reduces EMI. Fully shielded metal enclosures achieve shielding effectiveness ≥60 dB with multi‑stage input/output EMI filtering. Comprehensive hardware‑software dual protection including over/under voltage, overcurrent, short circuit, overtemperature, arcing and partial discharge alarms responds within<1 μs. Continuous insulation monitoring tracks insulation resistance, leakage current and partial discharge to estimate remaining lifespan. 8. Hierarchical testing and verification system. Material‑level low‑pressure, UV and corona aging tests qualify insulation selections. Component‑level electric‑field simulation and low‑pressure chamber trials verify transformer, busbar and terminal performance. System‑level full altitude simulation validates insulation withstand, corona immunity, temperature rise stability and long‑term operation, supplemented by official environmental, EMC and lightning compliance certification. This methodology resolves classic high‑altitude issues such as insufficient insulation margin, poor corona suppression, excessive size and low reliability. Graded solid/gas composite insulation dramatically improves low‑pressure breakdown strength; accurate altitude correction balances safety and compactness; full‑chain electric‑field control eliminates corona; altitude‑optimized thermal design overcomes poor convection cooling. Widely applicable to plateau wind converters, photovoltaic inverters, industrial high‑voltage supplies, power transmission equipment, aerospace power systems and research instruments, it delivers critical technical support for stable high‑voltage operation in extreme high‑altitude low‑pressure environments.