How to Perform AC & DC Arc Flash Methods for Renewable Energy Systems Outside the Voltage Limits of IEEE 1584-2018 Standard

I want to show the ETAP model and explain how this particular setting was initially given to us, what steps ETAP took to resolve this condition, and how the incident energy was evaluated according to the equipment ratings and the data provided by the manufacturer. So, based on the initial ETAP model that was provided to us with the corresponding protective device settings, we had the substation feeding into all 34.5 kV switchgears.
By Mr. Raghu VeeraRaghavan, Sr. Electrical Engineer and Arc Flash Division Manager, ETAP

This case study addresses 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.

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

Challenges

  • Verifying the reliability and safety of the grid and microgrid after adding renewable energy sources to the existing facility. The client wanted to add sixty-three photovoltaic arrays and inverters associated with them to the working electrical system, served by a 34.5 kV substation. The rating of each PV array was up to 2.8 MW.
  • Preparing all the required studies, such as short circuit analysis, protection and coordination settings, and arc flash studies on every level of voltage LV, MV, and DC PV (1.5kVDC). Considering the worst scenarios.
  • Creating a new, up-to-date electrical model, including equipment and settings sent by the customer. The model creation should use submittal data, the initial ETAP project with the client data, and the initial arc flash input parameters provided by the client.
  • Delivering trustworthy results by accessible national standards. Parameters, such as working distance, must be sufficient despite the voltage limit outside the IEEE 1584-2018 standard.
  • The main objective was to ensure safe operation for people. Incident energies should be decreased, and research should find solutions to avoid accidents.
  • Research different hardware configurations and equipment settings and report them understandably.
  • Checking the probability and prediction of events related mainly to the high incident arc flash energy.

Which solutions did they choose?

Selected applications

They chose the ETAP Digital-Twin modeling software, which includes Power System Analysis, Short Circuit, Arc Flash Analysis, Load Flow, and other features, to reliably model the distributed grid and microgrid and calculate all protections. 

ETAP ensured compliance with all needed electrical standards for designing and calculating the protection of the photovoltaic system. The primary standard used is the IEEE 1584-2018 Standard for performing Arc-Flash Hazard Calculations.

Why do they use ETAP?

Main Customer Benefits

  • A highly accurate power system model was created in ETAP based on the ETAP model delivered by the client. This new model has incorporated detailed data provided by the client and is used in the microgrid with all new equipment, PV arrays, inverters, and medium-voltage switchgear.
  • They can run the studies and research in one ETAP workspace, where all electrical calculations are integrated. Engineers can see dependencies between short-circuit settings, protection coordination, and arc flash mitigation settings.
  • Electrical equipment and its settings can be easily changed in the virtual model, managing different scenarios. The user could test the worst scenarios: the first was for arc flash with the inverter fed by all PV arrays, and the second was for each PV array where the disconnect fuse is locked. The researcher focused on the worst-case incident energy.
  • They found equipment provoking high incident energy: fuses with a clearing time of 0.79 sec and inverters with a trip time of 0.166 sec. The only solution was to use working distance mitigation techniques because nobody could decide to change fuses on the 34.5 kV side of the existing grid.
  • Using the ETAP Power Calculator tool, they declared the best-estimated dimension of the gap between conductors in the switchboard. They also found the enclosure dimensions and location to keep the incident energy conservative.
  • They used the 2-second rule to determine the incident energy and got the values at 46 calories per centimeter square using the 2-second rule.
  • Thanks to the "What if?" scenario tool, many scenarios were created to recommend settings for incident energy mitigation.

What do they think about ETAP?

 Opinions

We used our ETAP tools to predict or explain to the client how much the incident energy would differ based on the working distance mitigation technique. To evaluate different "What if" scenario tools without running ETAP every time, we used the Arc Flash Power Calculator tool, which is available on the Arc Flash page of the base editor.
By Mr. Raghu VeeraRaghavan, Sr. Electrical Engineer and Arc Flash Division Manager, ETAP

The 1584, 2018 method was selected in the ETAP Arc Flash Study Case, with variation applied. Although the protection was solid regarding the short circuit current, the nonlinearity of the arcing current reduced the arc current and changed the trip time of that particular fuse, resulting in a very high incident energy.
By Mr. Raghu VeeraRaghavan, Sr. Electrical Engineer and Arc Flash Division Manager, ETAP



Videos

AC and DC Arc Flash Methods for Renewable Energy Systems

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.


Solutions


Packages/Products