IEEE C62.55-2017 pdf free.IEEE Guide for Surge Protection of DC Power Feeds to Remote Radio Heads.
Antennas at tower tops are predominately fed by coax from radio equipment at the base of the tower. To reduce transmission losses and mechanical loading on the tower, RRHs are placed at the top of the tower next to the antenna. Fiber-optic cables carrying the signal information arc run up to the RRH equipment, where the optical signals arc converted into RF power to drive the antennas. The RRH is generally powered by a low voltage dc line (typically 48 V) run up to the equipment from a power supply at the base of the tower. Towers can be over 610 m (2000 II) tall, and the lightning surges to these towers can have very high j2g (the lightning action integral). Consequently, the potential for RRH damage due to surges on the power feed is high and surge protection is important to protect the RRH from possible damage. Thus, the problem considered is the nature of the surge on a dc power feed due to a lightning strike to the tower and how that impacts the design or selection of a protector.
5. Lightning characteristics
5.1 General
There arc basically four types of lightning as shown in 1- igure . The important parwncrs ul L*icsc Lyp
the manner in which the flash is initiated and the polarity of the flash.
5.2 Type (a)
Type (a) flashes have a downward leader and negative charge polarity [see Figure 1(a)]. About 90% of all lightning is this type. It characterizes ground flashes and flashes to short towers. Most of the existing data is for this type of lightning; most equipment will he subject to it (unless the equipment is on a higher tower). The characteristics of type (a) lightning are described in Table 3.5 OfCKJRE TB 549 (2013).
Type (c) flashes have a downward leader but positivc charge polarity [see Figure 1(c)]. About 10% of all lightning is this type. It characterizes ground flashes and flashes to short towers. There is less data fbr this kind of lightning. but it still needs to be considered, especially for the protection of equipment on low towers. The characteristics of typc(c) lightning were discussed in the 2012 ATIS Protection Engineers Group (PEG) Conference (Martin 111121). Based on the 2005 data in Martin [B12]. these characteristics are shown in Table 1.
5.4 Types (b) and (d)
Type (h) hashes have negative charge polarity, hut an upward leader [see Figure 1(b)]. This type of lightning occurs only to relatively tall towers. It is infrequent and the database for it is small, most of it going back to the Berger et al. 1975 paper [B I]. For tall towers, protection design should be based on the data (however meager) for this type of lightning.
Type (d) flashes have positive charge polarity and an upward leader [see Figure 1(d)], This type of lightning occurs only to relatively tall towers. It rarely occurs, but the effects can be large when it does. Because there is so little data on types (b) and (d) lightning, data for both are combined in one table in Table 7.3 of CIGRE TB 549 (2013).IEEE C62.55 pdf free download.