By: Wayne Foster, Head of Technical & Innnovation, Valen Utilities
As electrical engineers, we often face the critical task of designing standalone power systems (SAPS) that comply with AS/NZS 3000 standards while ensuring reliable, safe, and efficient operation. One key aspect of this process is sizing the system to meet the connection service capacity requirements—particularly for residential and commercial installations where the main switch circuit breaker on the customer board is often rated at 63A.
Let’s dive into the two fundamental considerations: ensuring timely disconnection during fault conditions and properly sizing the inverter and battery system to achieve this.
Timely Disconnection During Faults: Why it Matters
Ensuring protective devices disconnect fault currents quickly is critical for:
- Arc Flash Mitigation: Rapid disconnection minimizes the risk of arc flash incidents, protecting both personnel and equipment.
- Discrimination: Ensuring that only the faulty circuit is isolated prevents unnecessary disruption to the rest of the system.
- Avoiding Nuisance Tripping: Proper coordination ensures the system can handle short-term current surges without unnecessary disconnection.
Many design practices use 400 milliseconds as a benchmark for disconnection time during fault conditions, particularly to avoid dangerous touch voltages and ensure safe operation.
To achieve this, the SAPS must be capable of delivering sufficient fault current to trip the 63A circuit breaker rapidly. This is where the choice of inverter becomes crucial.
At Valen Utilities, our inverters are designed to excel in this area. For example, our inverter can deliver a surge current of up to 640A for up to 1 second, providing ample fault current to ensure rapid breaker operation (Different sizing available to meet your specific needs). This performance is critical for compliance and operational reliability, making our inverter a top choice for SAPS installations.
Sizing the Batteries: Feeding the Beast
- Peak Current Demand: The batteries must be capable of delivering the inverter’s maximum surge current (e.g., 640A) without significant voltage drop.
- Energy Capacity: Beyond surge currents, the batteries need sufficient energy capacity to support ongoing loads and recharge cycles.
- Generator: Is a genset compulsory? If not, to reduce TCO it is worth considering using a battery with a lower peak discharge rate and having increased modules/ storage/ days of autonomy.
At Valen Utilities, we recommend working closely with your supplier to calculate and verify the battery bank’s discharge capabilities under real-world conditions. Different batteries have different peak discharge rates. This ensures the system’s performance aligns with both the inverter’s requirements and the installation’s demands.
Designing SAPS that comply with AS/NZS 3000 and meet connection service capacity requirements demands a comprehensive approach. By carefully selecting inverters capable of delivering high surge currents and properly sizing the battery system to support these demands, you can create systems that are both compliant and reliable.
At Valen Utilites, we’re proud to offer solutions that simplify this process. With our inverter’s ability to deliver 640A for up to 1 second and our commitment to supporting engineers in optimizing their designs, we’re here to help you achieve SAPS excellence.
If you’d like to discuss your next project or learn more about our solutions, feel free to reach out or connect with us here on LinkedIn.
Let’s power the future—together.
