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The project involved integrating 63 large-scale PV arrays - each rated up to 2.8 MW - into an existing facility supplied by a 34.5 kV substation. ETAP was used to perform short-circuit studies, evaluate protection selectivity, and carry out both AC and DC arc-flash analyses, including cases operating outside the voltage limits of IEEE 1584-2018.
Blue Oak Energy is an American full-service photovoltaic system design, engineering, and consulting firm. The company engineers commercial and utility solar photovoltaic energy systems in the United States and abroad. Their team consists of licensed engineers, designers, and project managers. In 2022, the TRC Companies organization announced the acquisition of Blue Oak Energy. With direction-setting perspectives and partnerships, their 8,000+ tested practitioners in advisory, consulting, construction, engineering, and management services deliver unique resolutions that answer any built or natural imperative.
Location: Sacramento, California, United States
Year: 2022
Ensuring the safe operation of the photovoltaic electrical facilities according to the IEEE 1584 and NFPA standards
1. Managing complex behaviour of PV inverters in arc-flash studies. The inverter LV terminals feed transformer secondaries, resulting in long clearing times under reduced arcing current. Initial incident-energy values exceeded 40 cal/cm², with no mitigation settings provided.
2. Handling non-linear arcing currents as defined in IEEE 1584-2018. Lower arcing current increased fuse clearing time to 0.79 s, driving IE far above acceptable thresholds.
3. Selecting correct AC arc-flash methodology above 15 kV. The client requested IEEE 1584-2018 at 34.5 kV, even though the standard's scope ends at 15 kV. The Li method produced unrealistic values (>4000 cal/cm²).
4. Performing DC arc-flash calculations at 1500 VDC. Choosing the correct method (Stokes & Oppenlander) and estimating the conductor gap required iterative modelling.
Which solutions did they choose?
Why do they use ETAP?
Accurate modelling of inverter behaviour and auto-trip characteristics
The inverter’s voltage ride-through threshold (<50% nominal) was included, enabling the inverter auto-trip function. This reduced incident energy from extremely high values to ~62 cal/cm² - a major improvement, though still above 40.
Clear explanation of why incident energy was initially so high
ETAP demonstrated how reduced arcing current slowed fuse operation, increasing clearing time and thus drastically raising incident energy.
Rapid mitigation evaluation using ETAP Arc Flash Calculator
Correct method selection above 15 kV
Switchgear at 34.5 kV required changing from the Li method to the EPRI Arc Fault Method, creating realistic values compatible with PPE selection. Instantaneous relay settings (“maintenance mode”) further reduced IE to ~5.7 cal/cm².
DC Arc Flash: robust method & gap optimisation
What do they think about ETAP?
We applied the inverter auto-trip feature in ETAP and reduced incident energy significantly. Even with long fuse clearing times, ETAP allowed us to identify working-distance mitigation to stay under 40 cal/cm².
Selecting the correct AC method above 15 kV and using ETAP’s scenario tools minimized man-hours and delivered reliable results across all PV locations.
By Mr. Raghu VeeraRaghavan, Sr. Electrical Engineer and Arc Flash Division Manager, ETAP
This presentation will address the difficulties and lessons learnt on performing arc flash analysis using available methods (outside the voltage limits of IEEE 1584-2018 standard) on a 2.3 MW PV generation facility. The analysis includes system modeling, short-circuit, arc flash (both AC and DC) using various applicable calculation methods that best fit this application along with available tools in ETAP and generating worst-case arc flash deliverables.
Arcflash
ETAP Digital Twin
Arc Flash Analysis
Power Systems Analysis
Load Management System
ArcSafety™ - AC Arc Flash