The technical principle of the ultra-high frequency partial discharge detector is based on electromagnetic field theory and modern signal processing technology. It can be clearly dissected into three aspects: physical mechanism, signal processing flow, and positioning method.
I. Physical Principle: From Insulation Defects to Electromagnetic Radiation
The physical basis of ultra-high frequency partial discharge detection is that when there is a local discharge inside a high-voltage equipment, it will generate ultra-high frequency electromagnetic waves.
When there are defects such as bubbles, cracks, or metal impurities in the insulation material of the equipment, under the action of a strong electric field, the defect location will undergo non-through local discharge. Each discharge will be accompanied by a very short (less than 1 nanosecond) steep current pulse. According to Maxwell’s electromagnetic field theory, this transient current pulse will radiate broadband electromagnetic waves to the surrounding space, with frequencies covering the ultra-high frequency band from 300 MHz to 3 GHz and above. The core function of the ultra-high frequency partial discharge detector is to capture and analyze the electromagnetic wave signals of this specific frequency band.
II. Signal Processing Flow: From Antenna Capture to Intelligent Diagnosis
After capturing the weak ultra-high frequency signals, a complete signal processing flow is required to convert them into effective information for equipment diagnosis.
Signal Acquisition
Electromagnetic waves are captured through built-in or external ultra-high frequency sensors (antennas). External sensors are generally installed in the gaps of the equipment or the pot insulator position to achieve non-contact detection. Signal conditioning
Using a filter to initially remove low-frequency interference, and then adjusting the gain of the programmable amplifier based on the signal strength to ensure measurement accuracy.
Digital-to-Analog Conversion and Processing
The equipment uses FPGA (Field Programmable Gate Array) to complete digital down-conversion, FFT, and other front-end processing, effectively reducing the load on the main processor.
Data Analysis and Diagnosis
Generate PRPD/PRPS graphs, compare them with the database through pattern recognition or machine learning algorithms, and automatically identify discharge types such as suspended potential and metal particles.
Three. Precise Positioning: Time Difference Method and Acoustic-Electric Combined Positioning
After detecting the discharge signal, accurately locating the defect position is the key goal. The main methods used are as follows.
Time Difference Positioning Method
As a common positioning method, multiple sensors are arranged to measure the time difference of the same discharge signal reaching different sensors. Combining the characteristic that electromagnetic waves propagate in the medium at the speed of light, the solution of the hyperbola equation can be used to calculate the location of the discharge source. The current system can achieve decimeter-level positioning accuracy.
Acoustic-Electric Combined Positioning Method
Combining the ultra-high frequency method with ultrasonic wave method, the propagation speed of the ultra-high frequency signal is close to the speed of light, and the propagation speed of the ultrasonic wave is approximately 340 meters per second. By measuring the time difference of the two signals reaching the same sensor, the distance between the discharge point and the sensor can be more accurately estimated, which is suitable for positioning detection of enclosed equipment such as GIS.
Four. Technical Advantages and Limitations Core advantage
High sensitivity: Capable of detecting weak discharge signals as low as 0.1 picocoulombs (pC) or even 5 pC. The detection capability is superior to traditional methods.
Strong anti-interference: The working frequency band is higher than common noises such as corona discharge and radio broadcasts, resulting in high signal-to-noise ratio.
Electrostatic detection: Non-invasive detection can be achieved, and the equipment does not require power outage during the detection process.
Limitations
Signal attenuation: When ultra-high frequency signals propagate within the equipment cavity, they are prone to attenuation and distortion when encountering insulators, bends, etc.
Detection blind zone: Some slowly developing discharge defects cannot generate sufficient high-frequency components, resulting in the possibility of missed detection.
Calibration difficulty: It is difficult to conduct precise calibration of discharge quantity (in picocoulombs) and is mostly used for qualitative analysis and operation trend judgment.
Post time: Apr-01-2026