When conducting ultrasonic partial discharge detection, it is necessary to strictly follow the corresponding national standards, industry standards, and relevant regulations to ensure the standardization of the detection operation and the comparability of the detection results.
I. Main International Standards
IEC 62478:2016 “High-voltage test techniques – Measurement of partial discharges by electromagnetic and acoustic methods” (High-voltage Test Techniques – Measurement of Partial Discharges by Electromagnetic and Acoustic Methods), is the core international standard for detecting partial discharges using electromagnetic and acoustic methods, providing the core technical framework and guidance basis for ultrasonic partial discharge detection.
II. Main Chinese Standards
GB/T 7354-2018 “High-voltage test techniques – Partial discharge measurement”, this standard is equivalent to IEC 60270, although it is mainly targeted at electrical method partial discharge measurement, the definitions and basic concepts of partial discharge in it are also applicable to ultrasonic detection methods.
DL/T 1250-2013 “Local discharge detection methods and application guidelines for power cable lines”, clearly specifies various detection methods including ultrasonic methods, and the specific application requirements in the detection of local discharge in power cable lines.
DL/T 1630-2016 “Technical guidelines for on-line detection of partial discharge in gas-insulated metal-enclosed switchgear”, specifically stipulates the corresponding technical requirements, detection methods, and result judgment criteria for ultrasonic partial discharge detection in GIS equipment.
Q/GDW 11059.1-2013 “On-line testing technology for local discharge in switchgear – Field application guidelines, Part 1: Ultrasonic method”, makes specific and detailed regulations on the ultrasonic local discharge detection method, detection cycle, signal analysis method, and fault diagnosis key points for switch cabinets.
Q/GDW 1168-2013 “State maintenance test procedures for power transmission and transformation equipment”, as a core maintenance test procedure, clearly lists ultrasonic partial discharge detection as a recommended or required on-line detection project for switch cabinets, GIS, etc.
JB/T 10785-2007 “Ultrasonic partial discharge detector”, specifically formulates technical conditions, performance parameters, and testing methods for the detector itself.
III. Detection Process and Judgement Basis
When conducting the detection, the core is to control the entire process of the detection operation and the scientific basis for result judgment. The specific contents are as follows:
Preparation before detection: Review the basic information of the equipment to be detected, such as its operation history and current operating status, and take all necessary safety protection measures to ensure the safe conduct of the detection operation.
Background noise measurement: Measure the environmental background noise in an area far from the equipment to be detected or at a location where the equipment has been confirmed to have no partial discharge, providing a reference benchmark for subsequent signal analysis.
Detection strategy: Use a combination of “zone scanning + key measurement” to conduct comprehensive and targeted detection of key parts such as equipment joints, busbar connections, insulators, etc.
Signal analysis: Core observation of dB values (or µV values), 50Hz/100Hz power frequency correlation, phase distribution patterns (PRPD spectrogram), etc., as the core basis for result judgment.
Judgment method
Threshold method: Compare the detected signals with the background noise. If the signal amplitude is significantly higher than the background noise (such as a difference greater than 5-10 dB), it is suspected that the equipment has a partial discharge problem. Horizontal comparison method: Compare and analyze the detection signals of the same structure and type of equipment within the same substation. Equipment with significantly larger signal amplitudes is more likely to have local discharge defects.
Trend analysis method: Conduct regular and continuous detection on the same equipment, track and observe the changes in signal amplitudes, phase patterns, etc. If the indicators show a continuous growth trend, it indicates that the internal defect of the equipment may be in an deteriorating stage.
Diagnosis and report: Based on the amplitude, frequency characteristics, phase patterns, and sound properties of ultrasonic signals, combined with the equipment’s own structure and operation history, form a comprehensive diagnostic conclusion. At the same time, strictly follow the regulations to issue the detection report, clearly record the detection process, data, and diagnostic results.
Four. Typical Defect Detection Characteristics
The ultrasonic partial discharge detection technology can effectively identify various partial discharge defects of equipment. The occurrence scenarios and corresponding ultrasonic characteristics of different defects are as follows:
Surface discharge (electrical marks): Occurs more frequently in scenarios where insulators are dirty, damp, or have conductive contaminants; the ultrasonic characteristics are accompanied by continuous “buzzing” or “sizzling” sounds, with stable signal performance.
Electrical discharge: Commonly occurs at sharp electrode edges such as knife switch contacts and busbar burrs, and is more likely to occur in air media; the ultrasonic characteristics are regular “crackling” sounds, which can be detected in both positive and negative half-wave periods of the power frequency cycle.
Internal discharge: Caused by problems such as bubbles, voids, and stratification in solid or liquid insulating materials; the ultrasonic characteristics are characterized by a dull sound, with signal intensity related to the position and depth of the defect inside the equipment, and the defect location is relatively difficult to determine.
Floating potential discharge: Occurs when the shielding cover of the equipment is loose or screws are missing, and metal components not grounded due to capacitance coupling form floating potential; the ultrasonic characteristics are high signal strength and poor stability, accompanied by intense “crackling” or “dashing” sounds, belonging to a relatively dangerous type of partial discharge.
Arc discharge: Caused by direct short circuit between conductors or short circuit formed by contaminants; the ultrasonic characteristics are high signal energy, accompanied by loud and harsh sounds, indicating that the equipment failure is already at a relatively serious stage.
Five. Typical Application Scenarios
Daily inspection and condition monitoring: Incorporate ultrasonic partial discharge detection into the equipment’s preventive test system, conduct regular surveys of equipment such as switch cabinets and transformers, establish baseline data of equipment operation status, and promptly detect potential defects.
Fault location and diagnosis: When equipment emits abnormal sounds or the online monitoring system alarms, use the ultrasonic partial discharge detection instrument for precise detection to locate the fault point and diagnose the fault type.
Installation/after maintenance acceptance: Before new equipment is put into operation or after major maintenance of existing equipment, use ultrasonic detection to check for problems such as busbar burrs and poor component contact caused by improper installation or maintenance operations, ensuring the safety of equipment operation and resumption.
Detection in harsh environments: In on-site environments such as substations with strong electromagnetic interference, ultrasonic detection technology has unique application advantages due to its excellent anti-electromagnetic interference characteristics, compared to other detection methods, and can ensure the accuracy of detection results.
Post time: Jan-26-2026