What Is Stateful Inspection?

Status Detection: Integrate professional non-destructive testing technologies such as partial discharge online detection, X-ray flaw detection, infrared temperature measurement, oil analysis, three-dimensional field (electric field, magnetic field, thermal field) analysis, and power system analysis. A comprehensive subject that diagnoses latent faults such as operating conditions, insulation aging, and process defects of power equipment, and performs fault diagnosis on power equipment.

State detection

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Chinese name: State detection
Foreign name: Status Detection

Types of: Comprehensive subject
Purpose: Troubleshooting power equipment

The third-party testing objects of power equipment include: transformers, GIS, switch cabinets, cables, generators, motors, etc.

· Partial discharge detection

· Infrared detection

· X-ray inspection

·Power System Analysis

· 3D field (electric, magnetic and thermal) analysis

· DGA

Moisture in oil

·Dielectric loss

· Winding resistance

Leakage resistance / reactance

· Conversion ratio

· Insulation resistance

Degree of polymerization

-Preventive online testing methods to discover potential defects and failures of equipment

-On-line PD test is a non-destructive test that does not require power outages and does not cause any damage to the insulation

-Improve equipment reliability, reduce unnecessary overhaul and maintenance of equipment, and extend equipment life

-Latent insulation defects of new equipment found during the warranty period

-Evaluate equipment maintenance quality through online PD detection comparison before and after pre-test

-Ability to detect and find equipment holes, cracks and process defects, reducing maintenance costs

Application of State Detection, Motor Instrument, Acoustic and Electricity Partial Discharge Detection Technology in Substation

1. Basic concepts of partial discharge

In the insulation system of power equipment, discharge occurs only in some areas, and does not penetrate between the applied voltage conductors, that is, has not yet broken down. This phenomenon is called partial discharge. it is

Due to local electric field distortion and local field strength concentration, gas discharge or breakdown in the local area of the insulating medium is caused. It can occur on the edge of a conductor or on the surface or inside an insulator. Partial discharges in the insulator can even corrode the insulating material and eventually lead to insulation breakdown. Therefore, conducting partial discharge detection to prevent insulation accidents is of great significance for maintaining equipment safety and stable operation of the power system.

Partial discharge is a pulsed discharge, which will produce a series of physical phenomena and chemical changes such as light, sound, electrical and mechanical vibrations in and around the power equipment. These various physical and chemical changes accompanied by partial discharge can provide detection signals for monitoring the internal insulation status of power equipment.

2. Principles of UHF , AE , HFCT method

2.1 Principle of UHF method

Insulation strength and breakdown field strength in power equipment insulators are very high. When a partial discharge occurs in a small range, the breakdown process is fast, and a steep pulse current will be generated. Its rise time is less than 1ns and the excitation frequency Electromagnetic waves up to several GHz. The basic principle of the partial discharge detection ultra-high frequency (UHF) method is to detect the ultra-high frequency electromagnetic wave (300MHz f 3GHz) signals generated by a partial discharge in a power device through a UHF sensor, so as to obtain relevant information about partial discharge and realize partial Discharge monitoring. Depending on the situation of the field equipment, built-in UHF sensors and external UHF sensors can be used. Because the halo interference in the field is mainly concentrated below the 300MHz frequency band, the UHF method can effectively avoid the on-site interference such as corona, has high sensitivity and anti-interference ability, and can realize the advantages of partial discharge live detection, positioning, and defect type identification. .

2.2 Principle of AE method

When a partial discharge signal is generated inside a power device, shock vibration and sound are generated. Ultrasonic method

(AE, also known as acoustic emission method) measures the partial discharge signal by installing an ultrasonic sensor on the outer wall of the device cavity. The characteristic of this method is that the sensor has no connection with the electrical circuit of the power equipment and is not affected by electrical interference. However, it is susceptible to the surrounding environmental noise or mechanical vibration of the equipment when it is used in the field. Due to the large attenuation of ultrasonic signals in insulating materials commonly used in power equipment, the detection range of the ultrasonic detection method is limited, but it has the advantage of high positioning accuracy.

2.3 Principles of the HFCT method

When a partial discharge occurs inside the power equipment, high-frequency discharge current will propagate to the ground along the ground line. The high-frequency current sensor (HFCT) method implements partial discharge detection by installing HFCT on a ground wire to detect high-frequency current signals. HFCT generally uses the Rogowski coil method. A multi-turn conductive coil is surrounded on a ring-shaped core material. A high-frequency alternating electromagnetic field caused by high-frequency current passing through the center of the core will generate an induced voltage on the coil. Because there is no direct electrical connection between the measurement circuit of the HFCT sensor and the cable under test, it is a non-intrusive detection method, and the device under test does not need to be shut down. 3. Characteristics of combined acoustic-electrical partial discharge test for substation equipment 3.1 Test principle According to the structural characteristics of the power equipment operating on-site in the substation, the UHF method, HFCT method, and ultrasonic combined test method (sound-electricity combined method) are used to perform partial discharge online for power equipment monitor. The combined acoustic-electrical method simultaneously extracts UHF information, high-frequency current information, and ultrasound information of partial discharge signals. By comparing and analyzing the three signals, it can more effectively eliminate field interference, improve the accuracy of partial discharge positioning and the accuracy of defect type identification It is beneficial to find and determine insulation defects and realize the safe operation of substation equipment. The combined acoustic-electrical partial discharge detection method uses GIS equipment as an example. The external UHF sensor is placed near the insulator, the ultrasonic sensor is placed on the GIS cylinder shell, and the HFCT is installed on the ground wire of the GIS cable terminal. The partial discharge signals detected by each sensor are transmitted to the partial discharge detection system or high-speed oscilloscope positioning system for processing, to realize partial discharge positioning analysis, pattern recognition and insulation level diagnosis. 3.2 Technical Features 1. Adopt combined sound-electricity detection technology. Depending on the equipment, one or more partial discharge test technologies can be used to perform live partial discharge test of the equipment. At the same time, by comparing and analyzing multiple signals, field interference can be more effectively eliminated , Improve the accuracy of defect type identification, help to find and determine insulation defects, and ensure the safe operation of substation equipment. 2. Acoustic-electrical joint positioning technology is used to effectively combine the characteristics of UHF rapid positioning method and ultrasonic precise positioning to improve the accuracy of partial discharge positioning and greatly improve the maintenance efficiency of substation equipment. 3. Partial discharge detection system has strong anti-interference technology. UHF sensors are available in multiple frequency bands. The sensor can also be designated as an interference reference sensor, and it provides multiple analysis and processing methods and digital filtering to suppress interference technology. 4. Applicable to live partial discharge testing and positioning of GIS, transformers, power cables and switch cabinets in substations, and provide credible maintenance recommendations. 4. Application of combined acoustic-electrical partial discharge test in GIS, transformer, cable and switchgear 4.1. GIS detection application During the online inspection test of GIS equipment of a 220kV power station of Shanghai Electric Power Company, it was found that there are multiple amplitudes in 35kVGIS in the station For large UHF signals, after preliminary positioning analysis of UHF, multiple ultrasonic sensors are arranged in the area of the suspected GIS, and combined acoustic and electrical monitoring is performed to further determine the type and location of partial discharge. At this time, the detection signals and characteristic maps of the ultrasonic sensors and ultra-high frequency sensors are shown in Figure 1. The detection system judges that the insulation defect is a floating potential discharge, and the positioning accuracy reaches cm.

Condition testing and laboratory insulation testing services

· Comprehensive detection and analysis technology

· Insulating oil and gaseous insulating medium

· Analysis of liquid and solid insulation media

· Precise quantitative analysis

· Professional data analysis

Laboratory testing services

· Physicochemical properties of lubricants

· Special physical and chemical properties of lubricants

Complete set of diagnostic testing solutions to meet various testing needs

· Dissolved gas analysis in oil

· Insulation oil quality inspection and diagnosis

-Moisture Content

-Interfacial Tension

-Acid Number

-Color Number

-Visual / Sediment Exam

-Corrosive Sulfur

-Power Factor Dielectric Loss

-Dielectric Breakdown

-Particle Count

-Metals Analysis Metal Content in Oil

-Oxidation Inhibitor

-Resistivity Resistivity

-FuranicCompounds furfural content

-Microscopy Analysis

-Carbonyls hydroxyl content

Engineering Services

l Power equipment technical services

OEM and Equipment End User Engineering Designand Specification Analysis

Equipment engineering design and specification analysis for power equipment manufacturers and equipment users

2D and 3D Electromagnetic studies for AC and HVDC transformers, rectifiers, switchgear, surge arresters, etc.

Two-dimensional and three-dimensional analysis of electromagnetic fields in power equipment such as high-voltage AC, high-voltage DC converter transformers, rectifier transformers, circuit breakers, arresters

Failure analysis

Equipment failure analysis

l Condition detection

Our customers can rely on our: The value-added services we provide to our customers include:

· Extensive and up to date knowledge of ourexperts about industrial (up to 100kA), power transformers (up to 1000kV AC, 800kV DC) and network studies

· Professional simulation analysis of large-scale power transmission and transformation equipment, such as industrial equipment (current to 100kA), power transformers (voltage level to 1000kV AC and 800kV DC), and power grid analysis;

· Solid organization with very advanced simulation tools and laboratories

· Using advanced finite element simulation software and high pressure laboratory

· Independent third party organization

Third-party independent engineering analysis agency