Ⅰ.Purpose of testing

In accordance with the Technical Specifications for Live Testing of Power Equipment (Trial) and the State Grid Corporation of China Substation Testing Management Regulations (Trial) (State Grid [Operation and Inspection 3] 829-2017), the power industry conducts routine inspections and patrols to monitor, test, and diagnose the operational status of substations, transmission lines, and other electrical equipment without the need for power outages. This ensures the safe and stable operation of electrical equipment and allows for timely and efficient maintenance planning.

Since equipment defects may be accompanied by various physical phenomena such as heat generation, mechanical vibration, electromagnetic waves, and sound waves, multi-dimensional and comprehensive testing is performed during inspections using a variety of sensors. This approach helps accurately identify and locate potential faults.

Ⅱ.Background of the Inspection

The tested line is located in a densely populated residential area and is characterized by long service duration, high electrical load, and numerous branch lines. Despite 5 to 6 rounds of routine inspections using standard methods such as infrared thermography, binocular observation, and drone patrols, the operation and maintenance personnel from the power supply company were unable to identify any obvious hidden risks.

On August 5th, technicians from Xiangheng International, in coordination with the power company’s personnel, used an acoustic imaging device and successfully located three partial discharge points within four hours. On August 6th, the power company carried out a planned outage to inspect the identified locations. It was confirmed that all three insulators at the discharge points showed clear signs of partial discharge damage.

III.Detection Methods

Currently, infrared detection is the primary method used for line inspection in the power industry. However, some fault points may exhibit significant discharge activity without generating noticeable heat. Therefore, combining infrared detection with partial discharge detection has become a more comprehensive and effective inspection approach.

IV.Equipment Used in This Inspection

The MiniCAM acoustic Imager device utilizes time delay and sound field reconstruction to locate sound sources and generate composite images, enabling precise imaging and localization of sound emissions such as ultrasonic and acoustic signals caused by discharges.

Compact and portable, the device is equipped with 128 microphone sensors and a 7-inch full-color touchscreen. Weighing approximately 1.3 kg, it is easy to operate and enables rapid detection. It can identify abnormal sounds or discharge points from a distance, without physical contact and without the need for power outages—making it ideal for live-line inspection, defect warning, and targeted maintenance.

An external infrared module is also available, allowing simultaneous display of partial discharge and infrared imaging on the same screen.

V. Defect Analysis Report

01. Severe discharge detected on the outer-phase insulator of Pole No. 13 on Line 04 of the 10kV [15] Line.

Analysis of test results:

On the 10kV [15] Line, Pole No. 13 on Line 04, an acoustic imaging inspection of the outer-phase insulator at approximately 13 meters showed a discharge with an amplitude of 34.6dB. There was minimal interference on-site, and no discharge sound was audible to the human ear. The initial judgment is that the damage may have been caused by issues with the top binding line process, or by discharge occurring due to a gap between the fastening components. The exact cause needs to be confirmed through pole climbing or live-line work inspection.

Recommended Solution: 

Replace the insulator and wrap the binding line and conductor damage with insulating material. Inspect the enlarged image of the insulator at the defect location.

02. Severe discharge on the top outer-phase insulator of Pole No. 4 in Section 13 of the 10kV [15] Line.

Analysis of test results

On the 10kV [15] Line, Pole No. 4 in Section 13, the acoustic imaging inspection of the top outer-phase insulator at approximately 10 meters showed a discharge with an amplitude of 38.2dB. There was minimal interference on-site, and a faint discharge sound could be heard on the ground. The initial judgment is that the damage may have been caused by issues with the top binding line process, or by discharge occurring due to a gap between the fastening components. The exact cause needs to be confirmed through pole climbing or live-line work inspection.

Recommended Solution

Replace the insulator and wrap the binding line and conductor damage with insulating material. Inspect the enlarged image of the insulator at the defect location.

03. Moderate discharge on the middle-phase insulator of Pole No. 7, Section 13 of the 10kV xxLine (User).

Analysis of test results

On the 10kV xx Line, Pole No. 7, Section 13 (User), the acoustic imaging inspection of the middle-phase insulator at approximately 9 meters showed a discharge with an amplitude of 28.3dB. There was minimal interference on-site, and no discharge sound was audible to the human ear. The initial judgment is that the damage may have been caused by issues with the top binding line process, or by discharge occurring due to a gap between the fastening components. The exact cause needs to be confirmed through pole climbing or live-line work inspection.

Recommended Solution

Replace the insulator and wrap the binding line and conductor damage with insulating material. Inspect the enlarged image of the insulator at the defect location.