Jun Hao Li

Investigation of a comprehensive identification method used in acoustic detection system for GIS

Nowadays, the acoustic detection is widely used for defect diagnosis of gas insulated substations (GIS) in normal operation and factory tests. In this paper in order to develop a data analyzer for acoustic detection system to make an assistant diagnosis, the characteristic of acoustic signals generated by different artificial defects such as protrusions, floating shield, void in spacer and bouncing particles are investigated. Some meaningful parameters behind the detected acoustic signals are extracted and discussed, which are used to distinguish background noise, partial discharge (PD) phenomena or bouncing particles. Based on those works, a comprehensive identification method realized by processing the acoustic pulse sequences qi, ( Δ ti, qi) and (ti, qi) is introduced, which gives a recognition result with noise, PD type or bouncing particles. For the sequence (ti, qi), the backpropagation artificial neural network optimized by genetic algorithm (GA-BPANN) is used as a classifier based on the fingerprint consisting of 24 operators, which are derivate from typical 2D histograms of phase-resolved partial discharge (PRPD). And with considering the trigger source may having a phase difference from the working voltage, identification with phase compensation (IPC) is used as a try to deal with the challenge. Experimental results show that the comprehensive identification method is practical and effective.

The Research and Establishment of GIS Fault Simulation Test System

Abstract. In order to accurately analyze the field test results of the partial discharge in GIS and study on the partial discharge characteristics of typical insulation defects in GIS, this paper constructs a set of failure simulation test system which is based on the entity 363kV GIS which contains all the Main equipments. These system has artificial defect setting units and can applied voltage and current at the same time, it also can manually set a variety of GIS typical insulation defects at the defect setting units. The partial discharge detection and analysis in the case of the applied voltage and current can simulate actual field operating conditions of GIS.

The Partial Discharge Characteristics Study of the Insulated Copper Busbar Joint Metal Metal Protrusion Defect

Insulated copper busbar is widely used as a new type of electrical equipment in recent years. The joint of the busbar is linked with soft connection copper belt in the field. So, it is very easily lead to the metal protrusion defect at the joint. The metal protrusion detect at joint with entity insulated copper busbar is builded in lab. The partial discharge characteristics of this defect is studied under different applied voltage and the results show that such defect has apparent polarity effect, the discharge always appears in the negative half cycle. The discharge amplitude will not be increased very much with increasing of applied voltage but the discharge frequency will be increased significantly. The results provide the basis of laboratory studies for the field testing of insulated copper busbar.

The Study of Oscillating Lightning Impulse Voltage Generator for a 110kV GIS Field Test

The impulse voltage test for power equipment such as GIS is not performed in the field for the impulse voltage generator huge and difficult to operate. The oscillating impulse voltage that proposed by IEC60060-3 is a higher generation efficiency impulse waveform and suitable used in field. The oscillating lightning impulse voltage generator for a 110kV GIS field test is studied in this paper. The generator structure is described and the waveform parameter computer formula is derivate. Simulation and test shown the generator can produce impulse voltage that meet IEC60060-3 requirement.

The Measurement System of Partial Discharge under Impulse Voltage

Partial discharge (PD) is the important detection parameter for power equipment, with the development of high voltage test technology, PD detection under impulse voltage is more attention. In order to detect the partial discharge signal under the impulse voltage, this paper designs a high-frequency current sensor and broadband measurement impedance. A set of partial discharge measurement system under impulse voltage is built up. The frequency characteristics of current sensor and measurement impedance are detected. In order to test the measurement system, the PD signals of a needle defect under impulse voltage is detected, the test results show that the PD measurement system can detect the PD signals effectively.

The Simulation Study of Electromagnetic Wave Propagation Characteristics in Closed GIS Tank

Partial discharge (PD) detection using UHF signal is a well known advanced detecting method in GIS and has been actively studied. Numerical simulation using finite difference time domain (FDTD) algorithm is performed to investigate the transmission characteristics of W-M waves excited by partial discharge through straight closed tank of a GIS bus in. The time domain decaying characteristics and frequency domain resonance characteristics is studied in this paper. The simulation results shown that for the closed tank, E-M waves attenuate little during transmission and distribute oscillating in the tank. The distributions are symmetrical at 0 degree and 180 degrees and the energy at the two types of degrees is the same.

PD Characteristics in Transformer Oil under AC Condition

Partial discharge (PD) detection is a technique widely used for high voltage equipment insulation condition assessment. The metal protrusion is a situation that often appear in transformer. Metal protrusion will cause the electric field concentration and lead to partial discharge. In this paper, PD characteristics in transformer oils are examined under AC conditions, using a needle-to-plane electrode system. The PD activity in transformer oil is confirmed as appearing in pulse burst form and the PD number and amplitude will increase with the applied voltage increase. The PRPD pattern display behavior typical of corona PD in oil.

The Simulation Study of Transformer Inductive Oscillating Switching Impulse Voltage Generation

According to IEC60060-1, IEC60060-2 requirements, the large transformer should take impulse voltage test in site. However, this test is not performed in the field for the impulse voltage generator huge and difficult to operate. To solve this problem, IEC60060-3 propose using oscillating impulse voltage for equipment on-site impulse withstand voltage test. Oscillating impulse voltage has higher generation efficiency and close to the actual voltage waveform that electrical equipment bear. For the transformer, the oscillating impulse voltage can generated through inductive method. In order to study the generation of oscillating impulse voltage through inductive method for transformer, the simulation circuit is established using ATP soft and the oscillating switching impulse voltage characteristics is studied in this paper. The result show that the oscillating switching impulse voltage waveform that accordance with IEC requirements can be generated through inductive method for transformer.

The Study of Vibration Diagnosis Method for GIS

Gas insulated switchgear (GIS) will generate vibration during normal operation for the electromagnetic force. There will be generate abnormal vibration when the contacts are undesirable, the guide rod stressed unevenness. Therefore, it can be effective in fault diagnosis of this machineries through the vibration test of GIS in field. The vibration detection method of GIS equipment in field is studied in this paper, the composition of the vibration detection system is described. The field test has been done using vibration detection system and the test results show that through the vibration signal detected from the GIS equipment, the vibration characteristics of GIS can be clarified and make the fault diagnosis effectively.

The PD Pattern Characteristics of Typical Defects in GIS Based on Acoustic Detection

Gas insulated switchgear (GIS) is the most important equipment in the power system. The partial discharge (PD) is the main detection method for the insulation failure. Especially, for insulation condition assessment, the pattern recognition technology of partial discharge in GIS is the most important. Acoustic detection of GIS PD is the effective method and it has long application history. The acoustic detection method is very suitable for defects detection in GIS, for it has the advantages of on-line detection and easy realization of locating the defects.The PD pattern characteristic is the key factor for the analysis of defect type. The PD pattern characteristics of four typical defects in GIS based on acoustic detection are studied in this paper. The results provide a test basis for the recognition of PD types and a deeper study of the mechanism of PD.