تعاریف و اصطلاحات در گیر با اسکیم اتو ریکلوزر به شرح زیر قابل بیان است. Choice of Dead Time The dead time setting on a high-speed autoreclosing relay used on transmission lines should be long enough to allow complete arc de-ionization. When using high-speed reclosing with modern fast circuit breakers, it is important to know that at some point the de-ionization time requirement will be longer than the dead time imposed by the circuit breaker. (See Figure 10.) Times shown are typical for high-speed HV breakers. Arc deionizing time is shown as variable and depends primarily on the voltage level. At the point where arc-deionizing time is longer than the dead time imposed by the circuit breaker, dead time must be introduced outside of the breaker. This is done with a dead time or reclose time setting in the autoreclosing relay. (See Figure 11.)
Choice of Reset Time The reset time of autoreclosing relays on transmission lines must be long enough to allow the protective relays to operate when reclosing onto a permanent fault. Times from 3 to 10 seconds are common. Also, note that the reset time of the protective relay should be short enough so it is completely reset prior to the circuit breaker closing on a reclose operation. In this way, the protective relay will be prepared to operate if the reclose operation is not successful.
Number of Reclose Attempts High-speed reclosing on transmission and subtransmission systems where stability is a concern is invariably single shot. Repeated attempts of reclosing with high fault levels would have serious effects on system stability. Furthermore, the incidence of semi-permanent faults that could be cleared by repeated reclosures is to be less likely than on distribution systems. The Auto reclosing shall be coordinated with various equipment as indicated in Figure below.
AR – Auto-recloser BFR – Breaker failure relay COM – Communication COND – CB condition DLC SC – Dead line check and synchronism check LP – Line protection MAN – Manual CB control PD – Pole discordance relay When using step distance relaying on lines with high-speed reclosing, attempting to perform simultaneous tripping presents some difficulties. Because of the errors involved in determining the ohmic setting of distance relays, it is difficult, if not impossible, to accurately set a distance relay to cover 100% of the line with high-speed relaying. It is common to allow for these errors by setting the relay to cover 80-90% of the line length in the first or instantaneous zone. Figure 13 illustrates a typical three-zone distance scheme covering two transmission lines. Thus, there is a zone near the end of each line in which the faults are cleared by sequential tripping. These end zones represent 20-40% of the line length. The remaining 60-80% between the end zones is cleared simultaneously by the breakers at both ends. Therefore, a fault occurring in an end zone would be cleared in the zone 1 time, or instantaneously, by the protection at one end of the line, and in the zone 2 time (0.3-0.4 seconds) by the protection at the other end. High-speed reclosing used on the circuit breakers at each end of the line could result in a dead time insufficient to allow for de-ionization of the fault arc. A transient fault could, therefore, be reclosed on and seen as a permanent fault, resulting in the locking out of both breakers. There are two methods available for overcoming this problem. The first, where there is no pilot channel, is an extension of the zone 1 reach to apply instantaneous tripping over the entire line. The second is the use of a signaling channel to send a tripping signal to the remote end when a local zone 1 trip occurs.