A close look at arc flash risk in hyperscale data centres

Schneider Electric has released a study that provides guidance on assessing and managing arc flash risk in 800 VDC power architectures.

Based on deployment scenarios informed by hyperscale data centre design patterns, the analysis compares two emerging 800 VDC architectures with varying configurations. Its findings have demonstrated that arc flash outcomes depend strongly on architecture, capacitor placement and fault-clearing behaviour.

Schneider’s analysis comes at a time when 800 VDC architectures are being adopted to support denser racks in AI data centres. Led by NVIDIA, the transition to 800 VDC data centre power infrastructure will enable large-scale data centre and AI factories to support 400 kW IT racks and beyond.

While 800 VDC distribution has emerged as the practical path to power megawatt-scale racks efficiently, higher operating voltages require a deeper understanding of fault behaviour, protection coordination and safe work practices. The research indicates that even under the most demanding capacitor-dominated assumptions, arc flash risk in 800 VDC systems can be managed, and in many cases, is comparable to typical AC systems. Additionally, better modelling using advanced software and digital twins can help accurately portray arc flash risk.

“800 VDC power distribution represents a significant shift in data centre design, but it also introduces safety considerations that need to be studied extensively,” said Manish Kumar, EVP Secure Power & Data Centres, Schneider Electric.

“Our work with some of the world’s leading hyperscalers provides engineers and safety professionals with one of the first practical frameworks for evaluating arc flash risks, providing a structured approach to understanding fault behaviour, establishing safe work practices and designing effective protection schemes.

“Our goal is to help the industry move toward higher-voltage architectures with confidence and safety.”

Assessing two distinct 800 VDC architectures

Schneider Electric performed practical arc flash analysis of rack-level and facility-level 800 VDC architectures, reflecting the major implementation paths emerging across the industry. The analysis evaluates standards-based methods, transient simulation, and system-level modelling. Findings demonstrated that existing arc flash frameworks can be applied to 800 VDC systems when used in an architecture-aware, time-dependent way, and that design choices impact outcomes:

Rack-level 800 VDC architectures

In a sidecar (also called power rack) case study using conservative methods and assumptions, results showed incident energy well below the referenced 1.2 cal/cm² PPE threshold, even without protection devices.

Centralised 800 VDC architectures

The facility-level case study shows potential for slightly higher incident energy than rack-level designs when, again, considering a conservative, less realistic architecture with no overcurrent protection. The analysis also assesses the effect of system topology and demonstrates how fault locations both upstream and downstream of reverse-blocking diodes influence back-feed, peak current and arc flash outcomes.

When fault contribution is time-limited with standard protection devices, arc flash energy is reduced to appropriate levels for the work environments and generally aligned with common AC architectures.

Importance of design and protection strategies

The study shows that overall risks of arc flash in 800 VDC systems remain low, and in many cases are comparable to typical AC distribution. Even with time standard protection devices, incident energy can remain below key thresholds. The research also established that:

• Transient behaviour matters: In 800 VDC systems, arc flash is driven by time-dependent fault currents, with capacitor discharge dominating the first milliseconds of an event.
   
• Simulation improves accuracy: Software (such as transient simulation and power system analysis tools) shows that simplified arc flash analysis methods for DC systems often overestimate arc flash risk in capacitor-dominated systems. Operators can significantly reduce arc flash risk by informing their protection strategy with advanced software and digital twins like ETAP.
   
• Design choices reduce risk: Arc flash outcomes depend on architecture and system configuration, not on DC distribution alone, where capacitor placement, reverse-blocking devices and millisecond-scale protection are key levers for safe 800 VDC deployments.
   

“Industry standards remain essential for arc flash and electrical safety, but traditional methods can be overly conservative because they do not fully reflect how complex DC systems operate,” said Tanuj Khandelwal, CEO of ETAP.

“To understand real risk, engineers must evaluate system topology, fault behaviour, protection coordination, converter response, switching logic, and active protection schemes.

“ETAP enables teams to model and validate 800 VDC systems as they perform, helping move from conservative assumptions to more accurate, AI augmented, physics-based safety and operational decisions.”

Schneider Electric said this recent research builds on its decades-long history of arc flash safety testing and bolsters a commitment to supporting the industry’s transition to 800 VDC power architectures. The company has also performed extensive testing on live swap power capabilities in 800 VDC systems to enable safe maintenance.

The findings are available in a white paper titled ‘DC Arc Flash Analysis: A Practical Study on 800 VDC in Data Centers’.

Image credit: iStock.com/XH4D