Mitigation of Arc Flash hazard by using protection solution
This paper gives an introduction to the problematic phenomena of arc flashing. For protection engineers important terms and facts in the NFPA 70E standard and the IEEE 1584 standard will be presented. The importance of the fault clearing time will be discussed in detail. Protection schemes which achieve fast fault clearing times for bus faults and feeder faults will be reviewed. In this paper an application will be introduced which is based on the reverse interlocking scheme. Additionally it offers a new solution that achieves a fast fault clearing time for bus faults and close in faults. This is normally the area within a substation, where arc flashing can cause a potential hazard for operators. This application will eliminate the problem of longer fault clearing times for faults close to the bus due to the co-ordination with radial feeders relays. This paper will discuss the necessary settings considerations and will show the limits of this application
"Applications and Advantages for Protection schemes using IEC 61850 Standard"
Modern substations which are being built today use sophisticated microprocessor based relays. These relays have drastically reduced the cost of substations by combining multiple protection elements into one device. Additional enhanced functionality has also eliminated the need for separate devices such as measurement transducers, sequence of event recorders, large point count RTU's (remote terminal units) and, transient fault recorders. Until now complicated control schemes, such as, an auto transfer scheme or a throw over scheme for main-tie-main switchgear, or reverse interlocking bus protection, still required copper wires, auxiliary and lockout relays to achieve high speed reliable functionality. Implementation of the new IEC 61850 (International Electrotechnical Commission) standard will allow this to change
Pig Vocalizations Under Selected Husbandry Practices
Acoustical characteristics of vocalizations of sows, piglets, and nursery pigs under selected husbandry practices were analyzed with a digital signal processing system. The duration (D) and major energy-resonance frequency (P) for each call were determined as follows: a) processing of piglets (D = 0.81 s and f* = 3 700 Hz); b) food anticipation of breeding-gest ation sows (2.50 s and 3 000 Hz); c) isolation of piglet (0.34 s and 500, 3 500 Hz); d) startling of nursery pigs (0.29 s and 900 Hz); e) sows in heat (3.07 s and 1 375 Hz); f) farrowing (0.10 s and 3 000 Hz); g) sow nursing (0.15 s and 1 000 Hz); and h) mate greeting of sow (0.13 s and 1 000 Hz). Calls a) to d) are responses to human generated stressors, and calls e) through h) responses to social and physiological states of the pigs. Thus, vocalizations can be segmented for different pig production situations.