Power equipment is an important hub and channel in the transmission and distribution grid. During use, equipment may experience aging, disrepair, and potential faults. However, these situations cannot all be ruled out by human eyes or the experience of the staff. Specialized instruments and equipment must be used for testing to detect these safety hazards and promptly eliminate them.

 

In the operation of electricity, power safety has always been a string that electricity professionals tighten. Power equipment testing can play a role in preventing and discovering hidden dangers, so power equipment testing (including preventive testing and handover testing) is crucial.

 

Preventive testing of power equipment refers to the regular inspection or testing of equipment that has been put into operation according to specified testing conditions (such as specified testing equipment, environmental conditions, testing methods, and testing voltages), testing items, and testing cycles, in order to discover hidden dangers in the operation of power equipment, prevent accidents or damage to power equipment, and is an important measure to determine whether the equipment can continue to be put into operation and ensure safety.

 

With the rapid development of the social economy and the rapid advancement of science and technology, the scope, equipment, and technology of power equipment testing are also keeping pace with the times. The "health index" of a set of equipment consists of two parts: its electrical characteristics and mechanical characteristics; The problem of not being able to obtain the "health values" of the electrical characteristics of power equipment during power on operation has been troubling power users for many years. The emergence of new state monitoring technology has solved this problem. Not only does it expand the concept of power equipment detection, but it also fills the blind spots in the field of power equipment detection. Conventional power outage detection technology and status monitoring technology complement each other, providing comprehensive data support for the reliable operation of power equipment.

 

Accurately summarize the concept of power equipment testing. The detection of power equipment consists of two parts: status monitoring and power outage detection. State monitoring provides electrical characteristic data of power equipment during power on operation, while power outage detection provides partial electrical and mechanical characteristic data of power equipment during power outage. Both detection techniques are indispensable and complementary to each other. The data provided by the two detection techniques constitute the complete "health index" of power equipment.

 

The detection of power equipment under the new concept is an advanced detection management mode, a new and more effective detection strategy, which is a preventive operation executed based on the equipment status. It can effectively overcome the problem of equipment over repair or disrepair caused by regular maintenance, transition from "mandatory upon expiration" to "mandatory upon repair", and improve the availability, safety, and reliability of equipment. It is one of the effective ways for enterprises to achieve modern management and improve comprehensive strength, as well as an important part of building a first-class power supply enterprise. It is a concrete manifestation of management innovation and technological innovation. Power equipment testing should select different maintenance methods scientifically and reasonably based on the importance, controllability, and maintainability of different equipment, forming an optimized comprehensive maintenance method that integrates fault maintenance, regular maintenance, status maintenance, and improvement maintenance, improving equipment reliability and reducing power supply costs.

 

The routine power outage detection of electrical equipment can be carried out through the following aspects:

 

1. Measure insulation resistance

 

It is the most commonly used and simplest experimental method, usually measured using a megohmmeter. Based on the measured insulation resistance of the test sample at 1 minute, it is possible to detect whether there are concentrated defects, overall moisture, or through moisture in the insulation.

 

2. Measure leakage current

 

It is basically the same principle as measuring insulation resistance, and the nature of detecting defects is also roughly the same. However, due to the fact that the power supply used in leakage current measurement is generally provided by high-voltage rectification equipment, and the leakage current is directly read using a microampere meter. It has a test voltage that can be adjusted freely; High sensitivity and good measurement repeatability; Convert the insulation resistance value; The absorption ratio can be measured to determine characteristics such as insulation defects.

 

3. Measure the loss angle of the medium

 

It is a highly sensitive test project that can detect overall moisture, deterioration, and deterioration of electrical equipment insulation, as well as local defects in small volume tested equipment that are connected or not connected. But when the volume of the test sample is large and the volume occupied by the defect is small, it is difficult to detect using this method. It is widely used in electrical manufacturing, electrical equipment handover, and preventive testing.

 

4. AC voltage withstand test

 

It is a type of destructive testing that can further diagnose insulation defects in electrical equipment. The AC withstand voltage test is the most rigorous, effective, and direct test method for evaluating the insulation strength of electrical equipment. It can detect the weakest point of insulation during normal operation and plays a decisive role in determining whether electrical equipment can continue to be put into operation.

 

5. DC withstand voltage test

 

It not only detects moisture and deterioration in equipment insulation, but also plays a special role in identifying certain local defects in insulation. The DC withstand voltage test can detect certain defects that cannot be detected by the AC withstand voltage test. The AC and DC withstand voltage tests cannot replace each other and must be applied simultaneously in preventive testing, especially for motors, cables, etc. DC withstand voltage tests should be conducted.

 

The inspection item of state monitoring technology: State monitoring, also known as live detection, is actually a detection of the operating status of power equipment without power outage. It can greatly improve the authenticity and sensitivity of experiments, and detect insulation defects in a timely manner. Live detection does not affect the normal operation of equipment and does not require power outages, making up for the shortcomings of conventional detection.

 

The common methods of live detection currently include:

 

A. Status detection of power transmission and transformation equipment:

 

1) Transformer: Oil chromatography analysis, oil quality analysis, corrosive sulfur analysis in oil, winding deformation, partial discharge detection, infrared thermal imaging detection, etc.

 

2) GIS: SF6 gas analysis, ultra-high frequency partial discharge detection, ultrasonic detection, infrared thermal imaging, etc.

 

3) Transmission cables: Partial discharge detection, fiber optic temperature measurement, infrared thermal imaging, etc.

 

B. Distribution network equipment status detection (live detection)

 

1) Distribution cables: oscillation wave partial discharge testing, etc.

 

The OWTS cable partial discharge detection and positioning system can effectively detect the local level of 10kV distribution cables and accurately locate them, especially for cables before operation and old cables that have been running for a long time. It can promote the improvement of installation technology and avoid the occurrence of sudden accidents caused by the gradual deterioration of cables due to long-term operation. It is worth further promoting and applying.

 

2) Switchgear: Ground wave partial discharge detection, ultrasonic detection, infrared thermal imaging, etc.

 

The geoelectric partial discharge detection technology uses capacitive sensor probes to detect transient pulse voltages on the surface of the cabinet, in order to discover and locate partial discharge defects inside the switchgear.

 

Ultrasonic testing technology is mainly suitable for discharge detection in the air. In practical applications, defects that cannot be detected by technical means such as ground waves or even ultra-high frequencies can be detected. When defects at a certain stage are mainly reflected as vibration signals, ultrasonic detection methods have advantages in discovering defects.

 

Infrared thermal imaging technology can scan the temperature on the surface or inside of switchgear, which can directly observe the temperature distribution. By comprehensively analyzing the influence of factors such as current and ventilation on temperature distribution, overheating of equipment can be detected early.

 

3) Distribution transformer: Ground wave partial discharge detection, ultrasonic detection, infrared thermal imaging, etc.

 

The functions of the three technologies are the same as above. In practical applications, the three technologies are generally applied simultaneously and comprehensively analyzed and judged.

 

In summary, the detection of power equipment cannot be ignored and is an important means to maintain the safe operation of power equipment.

 

Conventional power outage detection and live detection complement each other, using different technical methods to detect and analyze various indicators of power equipment and draw conclusions.

 

Electricity is no small matter, and eliminating potential electricity hazards through "detection" should be prioritized. Whether it is routine testing or live testing, we hope that all electricity departments will give sufficient attention.