Abstract: Partial discharge (PD) is a critical indicator reflecting the insulation status of electrical equipment. Timely and accurate detection of PD is of great significance for ensuring the safe and stable operation of power systems. Q/GDW 11304.5-2015, as a key technical specification in China’s power industry, specifically regulates the technical requirements, test methods, and application criteria for high-frequency (HF) partial discharge energized test devices. This article systematically elaborates on the core content of Q/GDW 11304.5-2015, including the scope of application, detection principle, structural composition of the instrument, technical parameters, test requirements, and on-site application precautions. It aims to provide a comprehensive technical reference for engineers and researchers engaged in the design, production, procurement, and on-site detection of electrical equipment PD detection instruments.

Keywords: Q/GDW 11304.5-2015; high-frequency partial discharge; energized detection; technical specification; electrical equipment insulation

1. Introduction

With the continuous expansion of the scale of power systems and the increasing complexity of electrical equipment, the requirements for the reliability of power supply are constantly improving. Partial discharge, which refers to the electrical discharge that partially breaks down the insulation system of equipment, is an important precursor to insulation degradation and failure of electrical equipment <superscript>2. If not detected and handled in a timely manner, it may lead to serious accidents such as insulation breakdown, equipment damage, and even power outages. Energized test, which uses portable detection equipment to conduct on-site detection of equipment state quantities during operation, has become an important means of condition-based maintenance for electrical equipment due to its advantage of not requiring equipment shutdown <superscript>2.

Q/GDW 11304.5-2015 “Technical Specification for Energized Test Device of Electrical Equipment – Part 5: Technical Specification for High-Frequency Partial Discharge Detector” is an important part of the Q/GDW 11304 series of standards. It was formulated to standardize the technical indicators and application requirements of high-frequency partial discharge energized detection instruments, ensuring the accuracy, reliability, and consistency of detection results. This standard plays a vital guiding role in promoting the standardized development of the high-frequency partial discharge detection technology in China’s power industry. This article will conduct an in-depth interpretation of the key technical content of this standard.

2. Scope and Fundamental Definitions

2.1 Scope of Application

Q/GDW 11304.5-2015 specifies the detection principle, structural composition, technical requirements, test items and requirements, inspection rules, marking, packaging, transportation, and storage of high-frequency partial discharge energized detection instruments <superscript>1. This standard is applicable to the design, production, procurement, and inspection of high-frequency partial discharge energized detection instruments, providing a unified technical basis for all links of the instrument’s life cycle.

2.2 Fundamental Definitions

To ensure the accurate understanding and application of the standard, Q/GDW 11304.5-2015 defines key terms involved in high-frequency partial discharge detection <superscript>2:

• Partial Discharge (PD): Electrical discharge that partially breaks down the insulation system of equipment, which can occur near conductors (electrodes) or other positions.
• Energized Test: On-site detection of equipment state quantities using portable detection equipment during operation, which is short-term detection and different from long-term continuous online monitoring.
• High-Frequency Partial Discharge Detection: Detection technology that uses a frequency range of 3 MHz to 30 MHz to capture partial discharge signals.
• Phase Resolved Partial Discharge Pattern (PRPD): A two-dimensional or three-dimensional spectrum that statistically describes the amplitude, frequency, and phase relationship of partial discharge signals over a period of time.

3. Detection Principle and Instrument Structure

3.1 Detection Principle

The core principle of high-frequency partial discharge detection specified in Q/GDW 11304.5-2015 is based on the detection of high-frequency pulse current signals <superscript>2. When partial discharge occurs in electrical equipment, high-frequency pulse current will be generated on its ground down conductor or other ground potential connection lines. By installing a high-frequency current sensor on the ground down conductor or other ground potential connection lines, the high-frequency pulse current signals caused by partial discharge can be captured, thereby realizing the detection of partial discharge of electrical equipment <superscript>4. This detection method is non-intrusive because there is no direct electrical connection between the measurement circuit of the sensor and the measured equipment, so it does not affect the normal operation of the equipment <superscript>4.

3.2 Instrument Structure

According to Q/GDW 11304.5-2015, the high-frequency partial discharge detection system is generally composed of four core units: high-frequency current sensor, power frequency phase unit, signal acquisition unit, and signal processing and analysis unit <superscript>2:

1. High-Frequency Current Sensor: Responsible for receiving partial discharge signals. Generally, a Rogowski coil-type high-frequency current sensor is used. The high-frequency alternating magnetic field caused by the high-frequency current passing through the center of the magnetic core will generate an induced voltage on the coil, realizing the conversion of current signals to voltage signals <superscript>4.
2. Power Frequency Phase Unit: Used to obtain the power frequency reference phase, which provides a phase reference for the subsequent analysis of partial discharge signals (such as PRPD spectrum analysis) and helps to identify the type of partial discharge.
3. Signal Acquisition Unit: Conducts conditioning (such as amplification, filtering) on the analog signals of partial discharge and power frequency phase, and converts them into digital signals that can be processed by the computer.
4. Signal Processing and Analysis Unit: Completes the processing, analysis, display of partial discharge signals and human-computer interaction. It can generate various characteristic spectra (such as PRPD spectrum, PRPS spectrum) to help operators judge the amplitude, frequency, type, and severity of partial discharge <superscript>4.

4. Key Technical Requirements

Q/GDW 11304.5-2015 puts forward detailed technical requirements for high-frequency partial discharge detection instruments, covering performance indicators, environmental adaptability, and electromagnetic compatibility, to ensure the stability and reliability of the instruments in complex on-site environments.

4.1 Performance Indicators

The performance indicators of the instrument are the core of ensuring detection accuracy. The standard specifies key performance requirements such as frequency response range, sensitivity, and phase resolution of the instrument:

• Frequency Response Range: The effective frequency response range of the instrument should cover 3 MHz to 30 MHz, ensuring that partial discharge signals in this frequency band can be effectively captured.
• Sensitivity: The minimum detectable partial discharge signal amplitude of the instrument should meet the relevant requirements, ensuring that weak partial discharge signals can be detected.
• Phase Resolution: The instrument should have high phase resolution to accurately describe the phase relationship between partial discharge signals and power frequency voltage, which is crucial for identifying partial discharge types (such as corona discharge, internal discharge, surface discharge).

In addition, the standard classifies high-frequency partial discharge detectors into inspection type and diagnostic type according to their application scenarios <superscript>2. The inspection type is mainly used for equipment inspection, with the characteristics of portability and quick detection; the diagnostic type is mainly used for diagnostic tests and in-depth analysis, requiring more comprehensive signal processing and analysis functions, such as discharge type identification, partial discharge source location, etc.

4.2 Environmental Adaptability

The on-site environment of power equipment is complex, and the instrument needs to have good environmental adaptability. Q/GDW 11304.5-2015 refers to relevant national and industrial standards and specifies the environmental adaptability requirements of the instrument, including temperature, humidity, atmospheric pressure, and other aspects <superscript>3:

• Temperature Range: The working temperature range of the instrument should be -25℃ to +70℃, and the storage temperature range should be wider to adapt to the temperature changes in different regions and seasons.
• Humidity Range: It should be able to work normally in the relative humidity range of 5% to 95%, and there should be no condensation or freezing inside the product.
• Atmospheric Pressure: The working atmospheric pressure range is 80 kPa to 110 kPa, adapting to the altitude differences in different regions.

4.3 Electromagnetic Compatibility

The power system on-site has complex electromagnetic interference (such as radio frequency interference, electrostatic interference). The instrument must have good electromagnetic compatibility to ensure that its performance is not affected by external interference. The standard specifies the electromagnetic compatibility requirements of the instrument, including electrostatic discharge immunity, radio frequency electromagnetic field radiation immunity, electrical fast transient burst immunity, etc. <superscript>3. For example, the instrument should be able to withstand the electrostatic discharge interference of severity level 4 specified in DL/T 1432.1 and the radio frequency electromagnetic field radiation interference of severity level 3.

5. Test Items and Inspection Rules

5.1 Test Items

To verify whether the instrument meets the technical requirements specified in the standard, Q/GDW 11304.5-2015 specifies a series of test items, including performance tests, environmental adaptability tests, electromagnetic compatibility tests, and mechanical performance tests <superscript>3:

• Performance Tests: Including frequency response test, sensitivity test, phase resolution test, signal-to-noise ratio test, etc., to verify the core performance indicators of the instrument.
• Environmental Adaptability Tests: Including high and low temperature tests, humidity tests, vibration tests, impact tests, etc., to verify the adaptability of the instrument to harsh environments.
• Electromagnetic Compatibility Tests: Including electrostatic discharge test, radio frequency electromagnetic field radiation test, electrical fast transient burst test, surge test, etc., to verify the anti-interference ability of the instrument.
• Mechanical Performance Tests: Including drop test, packaging transportation test, etc., to verify the mechanical strength and reliability of the instrument during transportation and use.

5.2 Inspection Rules

The standard specifies the inspection rules for the instrument, including type inspection, factory inspection, and re-inspection:

• Type Inspection: Conducted when the instrument is newly designed, modified, or when there are major changes in materials and processes. All test items specified in the standard should be carried out.
• Factory Inspection: Conducted on each batch of products leaving the factory. The test items include key performance indicators and appearance inspection to ensure that the products leaving the factory meet the basic requirements of the standard.
• Re-inspection: Conducted when the instrument is stored for a long time (exceeding the specified storage period) or when quality problems are found during use. The re-inspection items are determined according to the actual situation.

6. On-Site Application Precautions

In addition to the technical requirements for the instrument itself, Q/GDW 11304.5-2015 also puts forward relevant requirements for on-site detection, including personnel requirements, safety requirements, and detection condition requirements <superscript>2:

6.1 Personnel Requirements

Operators engaged in on-site detection should be familiar with the technical parameters and performance of the instrument, master the operation procedures and use methods of the high-frequency partial discharge detector, and pass the relevant professional training and assessment.

6.2 Safety Requirements

On-site detection must strictly abide by the relevant safety standards and regulations of the power industry (such as Q/GDW 1799.1-2013). Operators should wear personal protective equipment as required, and ensure that the detection equipment and sensors are well insulated from the live parts of the equipment. At the same time, measures should be taken to prevent electric shock, falling, and other accidents.

6.3 Detection Condition Requirements

To ensure the accuracy of detection results, the following conditions should be met during on-site detection:

• There should be no other operations on the tested electrical equipment to avoid interference with the detection results.
• Try to avoid the influence of other interference sources (such as bias magnetic current) during the detection process.
• The metal shell and ground lead of the tested electrical equipment should be reliably grounded, and insulated well from the detection instrument and sensor.
• The detection should be carried out under appropriate environmental conditions, avoiding detection in harsh environments such as heavy rain, strong wind, and extreme temperature.

Q/GDW 11304.5-2015 “Technical Specification for Energized Test Device of Electrical Equipment – Part 5: Technical Specification for High-Frequency Partial Discharge Detector” provides a comprehensive and systematic technical basis for the high-frequency partial discharge energized detection technology in China’s power industry. By standardizing the detection principle, instrument structure, technical requirements, test items, and on-site application precautions of high-frequency partial discharge detection instruments, this standard effectively ensures the accuracy, reliability, and consistency of detection results, and plays an important role in promoting the condition-based maintenance of electrical equipment and improving the safe and stable operation level of power systems.

With the continuous development of power system technology, the requirements for partial discharge detection technology will continue to improve. It is expected that on the basis of Q/GDW 11304.5-2015, relevant standards will be continuously revised and improved to adapt to the development needs of new technologies and new equipment, and better serve the safe and efficient operation of the power industry.

References

[1] Q/GDW 11304.5-2015, Technical Specification for Energized Test Device of Electrical Equipment – Part 5: Technical Specification for High-Frequency Partial Discharge Detector[S].

[2] Guidelines for On-Site Application of High-Frequency Partial Discharge Energized Detection Technology for Electrical Equipment[S].

[3] Specification for Comprehensive Monitoring and Early Warning Device of Power Transformer (Reactor)[S].

[4] HDPD-SC50 Multifunctional Partial Discharge Tester Product Manual[Z].