Liu Y.,Tianjin University |
Du B.,Tianjin University |
Liu H.,State Grid Corporation of China |
Wang R.,Tianjin High Voltage Power Supply Company
Gaodianya Jishu/High Voltage Engineering | Year: 2012
With wide application of outdoor insulators in the transmission lines, the operation performance becomes one of the prominent factors affecting the stability and reliability of power system. The phase angle characteristics of leakage current can be used to evaluate the performance under typical contamination-humidity environments. For monitoring the insulator performance in such conditions, we established an artificial fog chamber and employed an ultrasonic vibration salt-fog generator filled with saline solutions to simulate different contamination-humidity environments. Silicone rubber outdoor insulators were used as specimens. And the test conditions were controlled to be the relative humidity from 70% to 100%, the contamination level from 1.0 mS/cm to 5.0 mS/cm at the temperature from 25°C to 40°C. AC voltage of 30 kV at 50 Hz was employed as the test voltage and the leakage current was measured by using a high-speed A/D converter with the sampling frequency of 22.05 kHz. The phase angle characteristics of the leakage current and the applied voltage were obtained by adopting the fast Fourier transform (FFT) spectral analysis method. By analyzing the variation of phase angle in relation to the surface performance, we established the relationship among the phase angle values, the relative humidity, the environmental temperature and the contamination level. It is found that the decrease in the phase angle values can increase the relative humidity, the environmental temperature and the contamination level, in which the phase angle shows the notable decrease at the relative humidity of 100%. Accordingly, it is considered that the phase angle characterization of leakage current can be utilized to identify and monitor the insulator performance, which is helpful to enhancing the running reliability and veracity of outdoor insulator.
Liu Y.,Tianjin University |
Du B.X.,Tianjin University |
Chen N.,Tianjin High Voltage Power Supply Company |
Yin Z.,Tianjin High Voltage Power Supply Company
ICHVE 2012 - 2012 International Conference on High Voltage Engineering and Application | Year: 2012
Based on the present investigation of leakage current for evaluating and monitoring outdoor insulators, the multiscale nonlinear technique is proposed to analyze the dynamic characteristics of leakage current through the artificial contamination experiments. Contamination tests were conducted in a laboratory by employing heavy salt fog without the deposition of non-soluble contamination. Based on the corresponding relationship between the leakage current and the behavior in heavy-fog conditions, the temporal series of leakage current are extended to two phase space by using a phase-space reconstructed method. In accordance with the dynamic behaviors on the insulator surface, the multiscale entropy of leakage current is obtained to investigate the underlying nonlinear characteristics in relation with the variation of contamination degree, ambient temperature and relative humidity. Associated with the quantitative analysis of mutiscale technique, the results can be helpful to improve the accuracy of insulator monitoring for reducing the accidents. © 2012 IEEE.
Gao Y.,Tianjin University |
Du B.X.,Tianjin University |
Shen F.,Tianjin High Voltage Power Supply Company |
Ma Z.L.,Tianjin University |
Han T.,Tianjin University
Polymer Degradation and Stability | Year: 2011
Polymer insulating materials used in radioactive environments are subjected to a risk of surface degradation caused by tracking. The tracking behavior becomes more complex with the presence of magnetic field. This paper presents investigation of tracking failure of gamma-ray irradiated polybutylene naphthalate (PBN) and polybutylene terephthalate (PBT) under magnetic field. The samples were irradiated in air up to 100 kGy and then up to 1000 kGy with dose rate of 10 kGy/h by using a 60Co gamma-source. Magnetic field (B→) with flux density of 250 mT was assembled perpendicularly to electric field (E→), which gave rise to relative angle between E→×B→ and surface normal vector (n→) of 0°, 90° and 180°, respectively. The experiment was carried out by applying a negative dc pulse voltage between a pair of brass needle-semicircle plate electrodes, the time to tracking failure and the discharge quantity were measured. Obtained results show the dependence of the tracking characteristics upon the radiation dose as well as the direction of E→×B→. It is suggested that the tracking behavior is in related to the thermal durability of the material and the surface discharge manner which are altered by the radiation induced chemical reactions and the combined electric-magnetic force, respectively. © 2010 Elsevier Ltd. All rights reserved.
Zhang Y.-W.,Tianjin High Voltage Power Supply Company |
Xie S.-G.,Tianjin High Voltage Power Supply Company |
Ren Y.,Tianjin High Voltage Power Supply Company |
Yu S.-G.,Tianjin High Voltage Power Supply Company |
Gao H.-X.,Tianjin Binhai Power Supply Company
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011
Bus protection and breaker failure protection of old substations can't meet the configuration requirements. A new microprocessor-based protection which contains bus protection and breaker failure protection is proposed to solve the problem. Two retrofit options are discussed: (1) cancel the original breaker protection of each interval, and start failure protection directly by contacts of line protection; (2) retain the original circuit breaker protection of each interval, and start failure protection by contacts of breaker protection. By comparing with each other in such aspects as characteristics, scope of application, etc, the second option with the minimum reformation scope is chosen. And for this option, a method to calculate the current setting is put forward, which means that failure current settings of breaker protection and failure protection have the same value. This program has been applied to a 500 kV substation of Tianjin Electric Power Corporation with good running status and no malfunction.
He C.,Tianjin High Voltage Power Supply Company |
Li X.,Tianjin Vocational Institute
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010
In this paper, the characteristics of transformer breaker failure protection are discussed first. Based on it, a perfect solving scheme is detailedly presented which includes the start-up circuits, the lockout release circuits, and the tripping circuits about both main transformer and bypassing transformer. By the way, the use of CT to transformer including bushing CT and external CT is analyzed in different locations in the vicinity of the short-circuit fault.