Research on mechanical fault diagnoses methodology of a circuit breaker based on the voltage and current during its operation
The performance of a circuit breaker during its operation has great impact to the power system security and is of great concern to the operation and management department of power grid. This paper presents a new method to acquire the performance information of the circuit breaker during its connecting/disconnecting operation through the voltage and current waveforms‥ Due to capacitance effects between dynamic and static contact, the voltage and current parameters in the process of connecting/disconnecting can be decomposed into two parts by orthogonal transformation method. The two parts are active and reactive power. The reactive component is generated by the capacitance effects. When the circuit breaker mechanical failure, particularly in velocity of contact anomalies, the capacitance effects will naturally be affected, that is, the reactive component will contain abnormal part inevitably. This method can effectively suppress interference, highlight the major characteristic quantities of the circuit breaker, and evaluate its mechanical performance.
Event timing and shape analysis of vibration bursts from power circuit breakers
Noninvasive vibration diagnostic techniques are implemented to assess the mechanical condition of power circuit breakers. A diagnostic system, the prototype commercial portable diagnostic system (PCPDS) has been developed Hardware of the PCPDS includes a portable computer, and a data acquisition unit and computer communication cards. Signal processing techniques include the discrete energy statistics envelope, short-time power spectrum, timing extraction algorithm and chi-square based shape test. Decision-making is carried out via a voter program, to which individual results from the timing and shape analysis programs are passed. Statistical and empirical thresholds have been established, that classify the circuit breaker as being in normal-transitional-abnormal (green-yellow-red) condition.
New approach to vision-based BGA package inspection
Ball grid array (BGA) techniques have developed very fast due to the advantages of more I/O ports, small size, and so on. In this paper, a vision-based algorithm for BGA package inspection is proposed to accurately estimate center and diameters of solder-balls of BGA packages, so that defects of BGA packages, such as missing or extra balls, oversize or undersize balls, over-height or under-height balls, and pitch can be detected for ensuring the quality of BGA packages.