Patrol type Partial Discharge Detecting Tester For Live XLPE cable And Power Transformer

1. Product introduction:

Due to manufacturing or installation defects, discharge occurs in the insulated portion of the live cable end (joint) until insulation breakdown damage occurs, and even a fire or explosion at uncertain defects may occur. Therefore, how to find the hidden troubles before the accident is the key to solve the problem, which makes the discharge detection necessary for live cable.

The model PPD8209A is a kind of high-frequency partial discharge inspection instrument which adopts the high-frequency current and ultrasonic detection methods for PD inspection and detecting to live MV/HV cable and transformer through HFCT (high-frequency current transformer) or Ultrasonic transducer. It has the feature of small volume, excellent performance and easy operation.

The PD tester adopts modern electronic and computer integrated technology to realize signal amplification (analog, electronic, digital), filtering, data acquisition, data processing, graphic display, test report automatic generation, thus completing the measurement and analysis of partial discharge.

2. Reference Standard

GB 7354 Partial discharge measurement

DLT 417 Guideline for local measurement of partial discharge of electric equipment

GBT 16927.1 High voltage test technology Part 1: General test requirements

GBT 16927.2 High voltage test techniques Part 2: Measuring system

GB T 16927.3 High voltage test techniques Part 3: Definition and requirements of field test

3.Main Components:

4. Detecting principle and method:

4.1 High-frequency current sensor measurement principle

The high-frequency current sensor is mainly used for partial discharge detection of high-voltage electrical equipment, and adopts the principle of pulse current. Since most high-voltage electrical equipment has distributed capacitance on its high and low voltage side or grounded part, when a high electric field strength area discharge takes place, the discharge signal is coupled to the grounding part and enters the earth through the grounding line. The HFCT sensor is clamped on the ground line and detects the pulse current signal generated by the PD, thereby obtaining partial discharge information of the device during test. It is mainly used for partial discharge signal detection of medium and high voltage equipment such as cables, transformers, reactors, GIS, switch-gear.

4.1.1 High frequency current detection for XLPE Cable

Due to manufacturing or installation defects, discharge occurs in the insulated portion of the cable end joint until insulation breakdown damage occurs, and even a fire or explosion may occur. Therefore, how to find the hidden troubles before the accident is the key to solve the problem, which makes the charge detection necessary.

In high-voltage cables, the wires and the metal sheath shield are separated by an insulating material to form a distributed capacitance, which is about several hundred pF, forming a path for high-frequency signals. Therefore, the high-frequency partial discharge signal is transmitted by the distributed capacitance to the ground lead. When the internal discharge occurs, a high-frequency pulse current is generated, and the high-frequency pulse current flows through the distributed capacitance between the core and the metal sheath , from the high-potential core to the low-level metal shield. On the sleeve , and enter the ground through the cable intermediate connector or the ground wire at the terminal. Therefore, a high-frequency current transformer sensor is connected to the grounding wire at the intermediate joint or terminal to couple the high-frequency pulse partial discharge current into the sensor and pass through the test cable between the sensor and the patrol instrument. The PPD8209A inspection tester performs signal acquisition and analysis.

The indication figure for live cable or live cable joint is as following :

4.2. Ultrasonic (US) measurement principle

When a partial discharge signal is generated inside the power equipment, vibration and sound of the impact are generated. Ultrasonic methods measure partial discharge signals by mounting an ultrasonic sensor on the outer wall of the device chamber. The method is characterized in that the sensor has no connection with the electrical circuit of the geographical equipment, and is not interfered by the electrical appliance, but is susceptible to the surrounding environment noise or the mechanical vibration of outside equipment when used in the field. Since the ultrasonic signal has a large attenuation in the commonly used insulating materials of the power equipment, the detection range of the ultrasonic detecting method is limited, but has the advantage of high PD positioning accuracy.

4.2.2 Ultrasonic detecting PD for live cable

For live high voltage cables, in many cases, due to the poor quality of the cable itself or cable accessories, external force damage and mechanical damage, corrosion and moisture, cable joint construction quality problems, accessories aging and other reasons, the cable joint is prone to partial discharge. Therefore, it is necessary to perform partial discharge detection on high voltage cables.

The PPD8609A tester is a device for detecting a discharge fault of a high voltage cable or cable joint .The detector of the tester adopts an acoustic-electric three-dimensional spatial positioning sensor, and can realize the three-dimensional spatial position and the discharge strength of the discharge point under a condition of not contacting the cable under test. Therefore, the insulation condition of the measured cable point will be judged, and the occurrence of the accident is prevented in advance. This detecting method usually can be applied to on-line detection and positioning of partial discharge of cable ends and cable distribution boxes.

5.General Technical data: