| Switchgear cabinet is one of indispensable(essential) equipment in electric power distribution system. The defects of Its insulation could lead to the occurrence of partial discharges and directly affects the distribution network of power supply stability. At present the partial discharges detection methods, such as conventional pulse current method can not achieve its efficients on the on-line switch cabinet without an embedded measurement;as well as ultra high frequency (UHF) method can not get because its severe high frequency attenuation, can't get good measurement effect and also; ultrasonic interference can not performe on this type of detection. The switch cabinet waves (TEV) detection method is the best one to ensure the stable operation of the switch cabinet has a certain engineering significance.In order to understand the nature operation of TEV, through theoretical analysis in this paper, we could get more informatiion on TEV formation in electric power equipment..As definition TEV is partial discharge through the switch gear cabinet at a certain point of the equivalent current and the equivalent impedance productof the instantaneous potential. Solid switchgear cabinet model simulation analysis by XFdtd, gives the processes of propagation of TEV, where TEV signal will be subject to the shielding effect of the metal shell,. TEV is generated by switchgear discontinuities overflow and formed on the surface of the metal casing of the instantaneous voltage. In addition, the amplitude of TEV signal is linear with the intensity of the discharge.Aiming at the problems of the current shortage of TEV detection means, this paper introduces the application of TEV sensor for partial discharge detection in switchgear cabinet,. A sensor is composed of an insulating casing, an induction electrode, metal shell, BNC connectors, and other, the high voltage arm capacitor 21pf, low voltage arm 200pf capacitor, partial pressure than 9.5:1. Through measurement of the TEV sensor, the sensor characteristic band is relatively smooth period is about 5 kHz to 20 MHz,3dB limit cut-off frequency about 2kHzfor TEV detection method in the switchgear cabinet using effective problem. In this paper, the design of the switchgear cabinet of TEV test platform, design of the needle plate, air gap and suspended three typical insulation defects,are designed for conventional pulse current method for reference and TEV detection results are compared and found that TEV dispersion diagram and conventional pulse current scatter diagram are similar to that of TEV method which can be effectively applied to partial discharge detection in switchgear cabinet. Subsequently, the comparison of the three kinds of typical defects of the discharge difference, It is found that the needle plate model focused on 75 to 100 degrees, between 250 to 300 degrees, the positive half cycle is in the shape of a rabbit earand negative half cycle is rectangular, the maximum value appeared in near 50 degrees,and the positive half cycle amplitude is greater than the negative half cycle. Air gap model of 45 degrees-200 DEG to 300 DEG, is in the shape of a mountainand had a maximum value at 60 degrees, near 240 degree, positive and negative half cycle symmetry distribution. Suspension model is concentrated in the 20-50 degrees, between 200 to 270 degrees, is a triangle and the maximum value appeared at 50 degrees, near 250 degrees, positive and negative half cycle are symmetry distribution. |
PDF Full Text Request