NEUTRON Combiner and RMU Scope for the Al Henakiyah 1.1 GW Solar Plant

1. Site and scale

A 1.1 GW interior site means high ambient temperature and dust, plus a very large string count. The design priority is a coordinated protection chain that scales cleanly across the whole plant.

2. Combiner and DC protection

• PV combiner boxes rated to 1500 V DC with individual gPV fuse protection.
• DC disconnect switches and Type 2 DC SPDs staged to the 1500 V envelope.
• DC MCBs for auxiliary and monitoring circuits.

3. RMU and substation coordination

At the plant substation the AC collection feeders terminate in NEUTRON low-voltage switchgear, and a ring main unit provides the controlled interface to the step-up transformer and grid connection. Selective coordination lets a downstream fault isolate locally without dropping the whole array.

4. Desert derating

• Current-carrying parts derated for sustained 45 deg C+ ambient and solar gain.
• Enclosure specified to IP65 with a corrosion class for inland dust.
• Ventilation path validated so protection devices stay within rated temperature.

5. Commissioning

Combiner boxes were inspected for torque, polarity and insulation resistance before energisation. String-level monitoring at the output supports early fault detection across the plant.

6. Outcome

The protection scope performed to specification through the first hot season, with no combiner-level nuisance trips attributable to the design. Coordinating combiner, switchgear and RMU as one system was the key lesson.