"The Neural Hub of PV Grid Connection: Deep Dive into RMU Collection and Protection Logic"

In photovoltaic (PV) power systems, the Ring Main Unit (RMU) serves as the critical hub connecting the collection lines to the grid interconnection point. It functions not only as a power aggregator but also as a "firewall" protecting the PV array from grid-side disturbances.

Below is the system logic architecture in English:

Core Functions of the RMU in PV Systems

1. Power Aggregation (Collection) Large-scale PV plants consist of hundreds of generation units. The MV output of each unit's transformer is connected to an RMU. Through incoming and outgoing units, multiple RMUs can aggregate the current from various units—much like small streams joining a large river—into a single main collection line.
2. Fault Sectionalizing & Isolation PV power output fluctuates significantly with weather, making the system sensitive to grid faults. RMUs equipped with Circuit Breakers or Load Break Switch + Fuse combinations can isolate a faulty branch in milliseconds. This ensures that a failure in one PV array or transformer does not cause the entire collection line to trip.
3. Enhanced Operational Reliability (Ring Topology) The defining feature of an RMU is its support for a "Ring" configuration. This provides two potential paths for power output. If one section of the collection cable fails, switching operations within the RMUs can isolate the fault while allowing the remaining units to export power via the alternative path. This is vital for reducing the "curtailment rate" of the plant.
4. Anti-Islanding & Smart Monitoring If the main grid loses power during maintenance, the PV system must stop exporting power immediately to protect maintenance personnel (Anti-Islanding). Integrated protection relays within the RMU monitor frequency and voltage changes, triggering a mandatory trip to ensure absolute safety.

Expert Insight: Specialized Requirements for PV RMUs

• Environmental Resilience: PV plants are often located in deserts or high-altitude regions with extreme temperature swings and heavy dust. Consequently, PV RMUs are usually fully sealed and insulated (using SF6 gas or ROCKWILL’s advanced APG solid insulation) to withstand harsh salt-spray and sandstorms.
• Smart Integration: Modern PV plants are typically unattended. RMUs are equipped with DTUs (Distribution Terminal Units), enabling real-time transmission of power data and equipment status to the central control room via fiber optics.

In short, the RMU is the "traffic hub" and "safety gate" of the PV plant, ensuring that green energy is delivered to the grid safely and efficiently.

Edited From：Dyson