On‑line partial discharge (PD) monitoring serves as a core technical guarantee for the safe operation of power transmission and transformation equipment. Widely deployed on transformers, GIS, switchgears, power cables, instrument transformers and capacitors, it detects subtle insulation defects in real time, predicts insulation degradation and latent faults, and prevents catastrophic breakdown accidents. It is the fundamental support for condition‑based maintenance and intelligent asset management. The dedicated high‑voltage excitation power supply is the key core component of PD monitoring systems. It provides ultra‑low‑noise DC high voltage to establish stable electric fields inside insulation, enabling latent defects to generate measurable partial discharge signals. Its noise floor, ripple suppression, long‑term stability and anti‑interference performance directly determine detection sensitivity, signal‑to‑noise ratio (SNR), and the accuracy of defect early warning. PD monitoring imposes extreme requirements far beyond conventional high‑voltage power supplies.
Eight core technical challenges: 1.Ultra‑low noise & ultra‑low ripple output: PD signals are extremely weak (pC/nC level), corresponding to nano‑ampere micro pulses easily submerged by power supply noise. Peak‑to‑peak ripple ≤ 0.001% (10 ppm), noise density ≤ 1 μV/√Hz; no spurious narrowband interference within 10 kHz–100 MHz detection bandwidth. Ensures SNR ≥ 60 dB and detection sensitivity down to 0.1 pC. 2.Extreme stability & ultra‑low temperature drift: PD inception/extinction voltages are highly sensitive to excitation fluctuations. Long‑term stability ≤ ±0.01%/8 h, short‑term stability ≤ ±0.005%, temperature coefficient ≤ ±1 ppm/°C, maintaining precision across −30 °C to +70 °C field environments. 3.High isolation & supreme EMC immunity: Withstands severe substation interference including power‑frequency fields, pulsed electromagnetic fields, lightning surges and fast transients. Input–output isolation ≥ twice maximum output voltage; impulse withstand ≥ three times rated voltage; common‑mode rejection ratio ≥ 160 dB; immunity to ±50 kV/μs fast common‑mode interference. 4.Wide adjustable output & full load adaptability: Continuously adjustable 0–500 kV with resolution ≤ 0.01% FS. Compatible with capacitive loads from tens of pF to several μF. Load regulation ≤ ±0.005%, line regulation ≤ ±0.002%. 5.Long‑term continuous reliability: 365/24 unattended operation; MTBF ≥ 1×10⁵ h; 15‑year design life with full lifecycle maintenance‑free performance and auto fault recovery. 6.Multi‑level safety & explosion‑proof design: Full non‑bypass protection including overvoltage, overcurrent, short circuit, over‑temperature, arc and earth fault protection. Zero‑voltage startup, soft shutdown and automatic residual charge release. Explosion‑proof models comply with GB 3836 for oil‑filled substations and underground applications. 7.Intelligent linkage & automatic PD testing: Seamless communication with PD detectors and upper monitoring platforms; programmable voltage ramping, automatic PDIV/PDEV measurement, synchronized signal acquisition and adaptive voltage adjustment. 8.Metrology traceability & standard compliance: Fully traceable to national standards in accordance with JJG 313, JJG 755, GB/T 7354 and IEC 60270, ensuring legal validity of insulation diagnosis results.
This methodology establishes a full‑process design framework covering ultra‑low‑noise topology, full‑link ripple suppression, low‑drift precision control, strong EMC shielding and metrology compliance. The universal core architecture adopted is:Front‑stage LLC resonant soft‑switch regulation + rear‑stage multi‑series linear regulation + fully digital low‑drift closed‑loop control, supplemented by all‑fiber isolation and full shielding. It eliminates traditional drawbacks such as high switching noise, poor stability and insufficient sensitivity for pC‑level PD detection. The two‑stage principle achieves high‑efficiency isolated boosting and coarse stabilization via LLC soft switching, fundamentally reducing switching noise. Multi‑stage high‑voltage linear regulation thoroughly eliminates residual ripple, realizing ppm‑level ultra‑quiet output. Precision digital closed‑loop control guarantees extreme temperature stability and long‑term drift suppression.
1.Ultra‑low‑noise & high‑stability topological design: •Full‑bridge LLC resonant soft‑switch front stage realizes ZVS/ZCS across full input (85–265 VAC) and full load range, minimizing dv/dt, di/dt and switching spikes. Dual power‑frequency + high‑frequency isolation enhances insulation safety while providing clean pre‑regulated HV input for linear post stages. Peak efficiency ≥ 93%. •2–4 series high‑voltage linear regulation stages achieve ripple attenuation ≥ 120 dB per stage, total suppression ≥ 240 dB. Delivers final ripple ≤ 10 ppm and noise density ≤ 1 μV/√Hz. 24‑bit high‑precision DAC enables continuous 0–full‑scale adjustment with resolution ≤ 0.01% FS. •Dual closed‑loop digital control adopts 24‑bit Σ‑Δ ADC sampling at ≥ 1 MSPS with low‑noise instrumentation amplifiers. Optimized DSP PID ensures long‑term stability ≤ ±0.01%/8 h and outstanding line/load regulation performance. Synchronized reference sampling eliminates drift errors from benchmark sources.
2.Full‑chain ripple & noise suppression system: •Noise source suppression: LLC soft switching eliminates hard‑switch interference; driving waveform optimization suppresses spikes; switching frequencies are placed outside the 10 kHz–100 MHz PD band with frequency spreading to disperse narrowband peak energy. •Multi‑cascaded filtering: Multi‑stage π, LC and RC filtering networks form a ten‑level suppression system with total attenuation ≥ 200 dB. Low‑ESR, low‑acoustic, low‑drift film/NP0 capacitors avoid piezoelectric noise. HV coaxial shielded output cables further isolate external interference. •Ultra‑low‑noise component selection: Calibration‑grade references (TC ≤ ±0.2 ppm/°C), metal‑foil sampling resistors (TC ≤ ±0.1 ppm/°C), 24‑bit low‑drift converters and ultra‑low‑noise op‑amps (input noise ≤ 1 nV/√Hz) minimize inherent system noise. Differential layout reduces common‑mode coupling. •Three‑layer full shielding structure: Inner permalloy magnetic shielding, intermediate copper electric shielding, outer steel enclosure (shielding efficiency ≥ 120 dB). Independent shielded cavities for power, regulation, control and reference circuits prevent internal crosstalk. Critical analog circuits adopt localized micro magnetic shielding.
3.Extreme low temperature drift & full‑range thermal stability: •Military/calibration‑grade low‑drift components applied throughout reference, sampling, amplification and conversion circuits to minimize native temperature dependency. •Factory full‑range multi‑point calibration covering ≥30 temperature points (−30 °C to +70 °C) and full voltage scales establishes a 3D temperature–voltage correction model stored in FRAM, ensuring overall error ≤ ±0.005% across the full temperature range. •Real‑time adaptive temperature compensation employs high‑resolution thermal sensors to dynamically correct control parameters, maintaining output fluctuation ≤ ±0.003% in extreme ambient conditions. •Long‑term aging stabilization: Core components undergo thousands of hours of high‑temperature burn‑in and thermal cycling; finished units complete extended continuous aging followed by recalibration, ensuring annual drift ≤ ±0.005%.
4.High isolation & severe EMC protection: •All‑fiber communication & control completely decouples primary and secondary circuits; common‑mode rejection ≥ 160 dB withstands ±50 kV/μs fast transients without control malfunction. Isolated battery power for control systems eliminates conducted grid interference. •Reinforced ultra‑high‑voltage insulation: Double isolation structure with vacuum epoxy potting for HV transformers; optimized electric field design ensures power supply self‑PD ≤ 1 pC at 1.1× rated voltage, avoiding false detection signals. •Three‑level surge protection on all ports absorbs lightning and switching surges; multi‑stage EMI filtering provides ≥120 dB suppression for 150 kHz–100 MHz interference. •Independent star‑point earthing separates power, analog, digital and shielding grounds strictly; low resistance ≤ 0.5 Ω prevents ground potential rise interference in substation environments.
5.Wide output range & full load compatibility: •Fully continuous linear adjustable output from 0–500 kV with no dead zone; segmented multi‑range design covers all voltage classes for transformers, GIS, cables and switchgears. Soft zero‑voltage startup avoids impulse‑induced false PD. •Advanced load compensation ensures excellent stability from no‑load to 120% overload; perfectly compatible with capacitive loads from 10 pF to 10 μF without loop oscillation. Switchable CV/CC modes support both routine PD monitoring and aging withstand tests. •Full factory non‑PD design for all high‑voltage components eliminates internal discharge; dedicated pulse isolation at output blocks noise coupling into PD detection loops, improving overall SNR.
6.Full‑lifecycle high reliability & long‑life engineering: •Extreme component derating following GJB military standards significantly reduces operational stress, ensuring MTBF ≥ 1×10⁵ h and 15‑year service life. •All‑solid‑state maintenance‑free construction: No fans, relays, electrolytic capacitors or moving parts; long‑life film/ceramic capacitors adopted throughout; natural cooling eliminates mechanical failure risks. •Redundant design for control power, driving, sampling and protection realizes seamless fault switching; multi watchdog systems prevent controller crash and ensure uninterrupted monitoring. •Strict environmental stress screening including thermal shock, vibration and prolonged burn‑in eliminates early failures and guarantees stable long‑term field performance.
7.PD linkage & intelligent monitoring integration: •Full automatic testing software enables programmable voltage ramping and automatic PDIV/PDEV characterization for standardized insulation diagnosis. Multi‑level user permission ensures operational safety. •Synchronized hardware & software interfaces support seamless connection with mainstream UHF, ultrasonic and high‑frequency PD detectors, achieving phase alignment between excitation voltage and discharge pulses to improve defect recognition accuracy. •Embedded full lifecycle health management uploads operational data to substation IoT platforms for remote diagnosis, early aging warning and traceable data storage exceeding 15 years.
8.Metrology compliance & full‑scenario adaptability: •Fully compliant with GB/T 7354, IEC 60270, JJG 1021 and relevant high‑voltage test standards; complete traceability chain ensures official calibration validity for insulation evaluation reports. •Adaptable to transformers, GIS, switchgears, cables, reactors and capacitors for on‑line monitoring, off‑line inspection and factory type tests. Customizable for indoor substations, outdoor switchyards, offshore wind farms and explosion‑proof underground mining environments per GB 3836.
Summary: This integrated technical framework solves critical bottlenecks of conventional HV power supplies for PD monitoring: high noise, poor stability, weak EMC and insufficient pC‑level detection capability. It realizes ppm‑level ripple, ultra‑low temperature drift, 500 kV wide adjustable output, self non‑PD performance and full metrology traceability. It provides core independent technology for domestic high‑precision partial discharge monitoring equipment, supporting intelligent insulation health management across the entire power grid.