Structure of Larger-Scale Solar Generators

In order to avoid unnecessarily long wiring runs, larger solar generators (as from 10 to 30 strings) are subdivided into arrays (see Figures 4.34 and 4.88) and the strings of these arrays are wired together using array junction boxes (TGAK) whose wires lead to a generator junction box where they are parallel connected to the solar generator as a whole. The main DC cable (DC-HL) leads from this generator

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PV Array Grounded in the Middle

 

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Figure 4.88 Layout of a relatively large solar generator. The array strings are wired in parallel in the array junction box (TGAK). The array wiring (TGK) leading from this junction box is connected to the solar generator via these generator junction boxes (GAK) and for larger generators should always be fused, preferably via circuit breakers (see Figure 4.34). In cases where numerous array conductors are wired in parallel in generator junction boxes, each of these conductors should be protected against reverse current from the solar generator. The ideal lightning protection solution in such cases is the use of metal raceways for bilaterally grounded shielded cables for array wiring and main DC cables (DC-HL) with a shield gauge of >10 mm2 Cu

junction box to the DC appliance (normally a large grid-connected inverter). To achieve effective lightning protection, it is essential that: (a) thermally monitored varistors are integrated into both the array and generator junction boxes; (b) the equalization bonding conductor (PAL) has a sufficiently large gauge (>10mm2 Cu, [4.13]) and is in close proximity to the relevant array wire or main DC cable. This equalization bonding conductor is attached to the module’s metal frame or to a metal rack and is grounded to the inverter.

In the interest of clarity, Figure 4.88 displays only the main elements. For more on PV system lightning protection, see Section 6.9.

Updated: August 7, 2015 — 11:35 pm