Episode 35 ~2:10 Power Safety EN · العربية

Arc flash on Saudi projects: specify the clearing time, not just the suit

We found no incident energy figure in the Saudi regulations we searched to 9 October 2026; they set general employer duties. A third-party copy of Saudi Aramco's Safety Handbook sets levels, and other contracts import NFPA 70E and IEEE 1584. Before any PPE comes an electrically safe work condition. Where energized work is justified, the 2018 model shows one input leading in our example: how long the protection takes to clear the arc.

Arc-rated clothing beside a closed switchboard
NLC Academy · Episode 35
Arc flash on Saudi projects: specify the clearing time, not just the suit
~2:10
Animated explainer, press play to watch the concepts now; the filmed cut publishes once production wraps.
Key Takeaways

What you'll walk away with

Four decisions to carry into the next switchgear specification or arc flash study you review.

01

We found no cal/cm² value in Saudi rules; contracts carry one.

Labour Law Articles 121 to 123 and the MHRSD OSH regulation set general duties: protect, inform, provide PPE, train. NCOSH's high-risk occupations regulation lists panel assemblers and names the hazard as shock. We found no arc-flash entry in the SBC 401-2024 contents. A third-party copy of Saudi Aramco's Safety Handbook sets levels: A up to 1.2, B above 1.2 up to 12, C above 12 up to 40 cal/cm², no energized work above 40. Searched to 9 October 2026; absence is not proof of no duty.

02

De-energize first; then clearing time is the lever.

NFPA 70E-2024 110.2 makes an electrically safe work condition the default; energized work needs a justification and a permit, and PPE is the last control. Where it is justified, energy is linear in arc duration. On the illustrative 380 V, 35 kA board, 0.5 s gives 17.7 cal/cm² at 610 mm and a 3.3 m boundary; 70 ms gives 2.5 and 0.96 m. Doubling the fault current at the same time raised it 1.48 times here.

03

Ask for both arcing currents, in every fault scenario.

IEEE 1584-2018 reruns each fault at a reduced arcing current and keeps the worse. On an illustrative breaker with a 20 kA instantaneous pickup the reduced current waits 300 ms instead of 50: 1.8 becomes 9.3 cal/cm². A minimum network fault is a separate scenario with its own bolted current; ask the network for minimum as well as maximum fault data.

04

PPE is an ensemble, and the label shows one method.

With the incident energy method, NFPA 70E Table 130.5(G) pairs clothing rated at least E with face and head, hand, hearing and foot protection; shock protection is a separate assessment. 130.5 allows the energy method or the category table, never both on one piece of equipment. IEEE 1584 requires no label; NEC 110.16 and NFPA 70E 130.5(H) do.

The Saudi layer first
Saudi rules set duties; we found no cal/cm² value in them
Labour Law 121-123, MHRSD OSH regulationemployer duties: protect, inform, PPE, trainingNCOSH high-risk occupations regulationlists panel assemblers; names the hazard as shockSBC 401-2024, an IEC 60364 based codeno arc-flash entry in the contents we readSAIS, formerly HCIS, Decision 327names NFPA 70; NFPA 70E not found in itSaudi Arabian Grid Code, May 2024maximum and minimum fault data owed to usersSaudi Aramco Safety Handbook (copy)contract: cal/cm² levels, third-party copyno value foundsupplies an inputcontract value
Searched to 2026-10-09: not finding a value is not proof that no duty applies. The general duties bind every employer. The cal/cm² figures we found come from contracts: Saudi Aramco documents, or a specification that imports NFPA 70E and IEEE 1584.
What Aramco writes
Aramco's handbook copy uses energy levels, not categories
Saudi Aramco levels, third-party handbook copyABCDangerNFPA 70E Table 130.5(G): clothing rated ≥ E, plusshield + balaclavaarc flash suit hoodNFPA 70E categories: minimum clothing ratings12340.5 s: 17.7with ZSI: 2.50.51.248122540100200incident energy, cal/cm², log scale
Not a controlled copy: no revision date is printed, and which level owns exactly 1.2, 12 or 40 is not confirmed. G.I. 2.721, which it cites, was not available. Use the client's current controlled revision.
Who owns what
Four documents, four jobs, none of them Saudi
NEC 110.16installation code2023: label ≥ 1000 A2026: content listedNFPA 70E 130.5employer's standardone method, not boththe label's contentIEEE 1584-2018a Guide: the sumsenergy and boundaryno PPE advice at allIEEE 1584.1-2022the study's scopewhat a study delivers1584.2: data checklistsSaudi project: applies where the contract names it
IEEE 1584 calculates; it does not require a label.
Before any ppe
De-energize first. PPE is the last control
1Electrically safe work conditionthe default: NFPA 70E-2024 110.22Energized work only if justifiedinfeasible, or de-energizing adds hazard3Permit, qualified persons, safe practicesenergized electrical work permit, 130.24Two assessments: shock and arc flash130.4 and 130.5, each on its own5PPE last, by one method130.7: clothing, face, hands, hearing, feetHaving PPE never justifies energized work
Energized work needs its own justification, a permit and qualified persons. PPE limits burn injury at the working distance; it does not stop blast, fragments or noise.
Arc-rated clothing beside a closed switchboard
Reference

What each document actually requires

Saudi documents first, then the documents a contract imports. Every row names its source; a Saudi row reports what we found in the text we read, searched to 9 October 2026, not proof that no duty exists.

Requirement Value Source
Before any PPEelectrically safe work condition first; energized work only if justified, with a permit and qualified personsNFPA 70E-2024 110.2, 110.3(H)(3), 130.2
Saudi statutory arc-flash valuenone found in the texts searched; general duties: protect, inform, PPE, trainingLabour Law Arts. 121-123; MHRSD OSH Regulation; NCOSH 2025
Saudi electrical codeIEC 60364 based; no arc-flash entry in the contents listSBC 401-CR-2024, table of contents
Saudi Aramco PPE levelsA up to 1.2; B above 1.2 up to 12; C above 12 up to 40 cal/cm²; no energized work above 40Safety Handbook, 5th ed., third-party copy, not controlled
Saudi Aramco isolationdisconnect, test and ground at 480 V and aboveSafety Handbook, 5th ed., third-party copy, not controlled
Fault data at the connectionmaximum and minimum, supplied by the networkSaudi Arabian Grid Code, May 2024, Schedule 12
Calculation model208 V to 15 kV, three-phase, 50 or 60 Hz; 0.5 to 106 kA at 208 to 600 V, 0.2 to 65 kA at 601 V to 15 kVIEEE 1584-2018, as quoted in PCIC EUR24_17
Minimum working distance305 mm (12 in); nearer is outside the model's rangeIEEE 1584-2018, as quoted in PCIC EUR24_17
Arc flash boundarywhere energy falls to 1.2 cal/cm² (5 J/cm²)NFPA 70E 130.5; IEEE 1584-2018
PPE selectionenergy method or category table, not bothNFPA 70E 130.5
Category clothing ratings4, 8, 25 and 40 cal/cm², categories 1 to 4NFPA 70E Table 130.7(C)(15)(c)
Label contentvoltage, boundary, and one method's resultNFPA 70E 130.5(H)
Review intervalat least every 5 years, and after any change that affects itNFPA 70E 130.5
Installation marking2026 text: voltage, boundary, energy or PPE level, dateNFPA 70 (NEC) 110.16
Arc-resistant MV gearcontains an internal arc only as tested and installed, in the rated door configuration; no PPE waiver by itselfIEC 62271-200; IEEE C37.20.7-2017 and 2024
PPE with the energy methodclothing rated at least E, plus face and head, hand, hearing and foot protection; shock assessed separatelyNFPA 70E-2024 Table 130.5(G); 130.4
Distance
Working distance is an input. The boundary is an output
1310301.2 cal/cm²: the boundary0.5 s: 17.7 at 610 mm3.29 m70 ms, ZSI: 2.5 at 610 mm0.96 m305610100020005000working distance, mm; energy, cal/cm²; log axes
Cut the clearing time to 70 ms and the boundary moves from 3.3 m to 0.96 m. Set the working distance from the task; read the boundary from the model.
Arcing current
The arc draws less than the bolted fault current
20%40%60%80%VCB, averageVCB, reduced by VarCfHCB, averageat 35 kA bolted: 21.2 kA arcing, VCB520406080100bolted fault current, kA, at 380 V
Ask for both arcing currents per bus, each with its own clearing time.
What moves the number
On this board, clearing time moved the energy most
baseline, 0.5 s17.7clearing time 50 ms1.8working distance 455 mm28.4fault current doubled26.2fault current halved9.3horizontal bus, HCB31.5
SEC's public awareness page calls the clearing time the one variable that can be positively controlled.
The low-current trap
Less current, 5.3 times the energy
503001000average 21.2 kA: 50 msreduced 18.5 kA: 300 ms5102050arcing current, kA; clearing time, ms1.8 cal/cm²at the average current9.3 cal/cm²at the reduced current
Assess each fault scenario at both arcing currents, with the clearing time read at each.
Deep Dive

Six things that decide the number on the label

From the Saudi paperwork to the clearing time, in the order a design review meets them.

What we found in Saudi rules, and what we did not.

Labour Law Article 123 makes the employer inform workers of their job's hazards, provide suitable PPE and train them in it; Article 121 leaves technical detail to ministerial decision. The MHRSD OSH Management Regulation sets a management system with PPE as the last control, and NCOSH's Regulation on the Organization of Work in High-Risk Occupations lists electrical distribution panel assemblers (code 821204) and building electricians among the occupations that need a permit, training and medical checks; its electrical hazard is defined as shock. We found no arc-flash entry in the SBC 401-2024 contents list, and no mention of NFPA 70E in SAIS Decision 327, which names NFPA 70. That is the result of the documents we searched to 9 October 2026, not proof that no Saudi duty applies: the general duties to assess and control hazards bind every employer. The cal/cm² figures we found came from contracts.

What a copy of Saudi Aramco's handbook says.

A third-party copy of the Saudi Aramco Safety Handbook, 5th edition, sets arc-rated PPE as shown on each equipment label, in levels: A up to 1.2 cal/cm², B above 1.2 up to 12, C above 12 up to 40, and Danger above 40 with no energized work. It lists remote switching, remote racking and the energy-reducing maintenance switch where available, and isolation with test and grounding at 480 V and above. NFPA 70E itself says only, in an informational note, that above 40 cal/cm² de-energizing deserves greater emphasis; the ban is in the handbook copy. That copy is not controlled: no revision date is printed, and which level owns exactly 1.2, 12 or 40 is not confirmed. G.I. 2.721, which it cites, was not available. On Aramco work, use the current controlled revision the client issues.

The model, its range, and what it leaves out.

IEEE 1584-2018 is a Guide: eight inputs per location plus the clearing time, three-phase AC from 208 V to 15 kV at 50 or 60 Hz. Its tested ranges are two, not one: 0.5 to 106 kA bolted and a 6.35 to 76.2 mm gap at 208 to 600 V; 0.2 to 65 kA and 19.05 to 254 mm at 601 V to 15 kV. Enclosure height and width go up to 1244.6 mm, the opening up to 1.549 m², the width more than four times the gap, and the working distance at least 305 mm (these limits as quoted by the IEEE 1584 vice-chair's PCIC paper; the standard's text is licensed and was not read). No input for ambient temperature, altitude, grounding or X/R. Our Python code implements the IEEE 1584-2018 equations and checks itself on every build against 15 rows of a published export of the IEEE 1584-2018 spreadsheet, at both arcing currents and for the boundary, to 0.1%; it is not a certified tool. SEC's public arc-flash page, as archived in 2019 and 2023, still repeats the 125 kVA screen the 2018 edition deleted.

Two currents per scenario, and more than one scenario.

The arc carries less than the bolted fault: 21.2 of 35 kA at 380 V. The 2018 model then reruns the same fault at a current reduced by its VarCf factor, here 18.5 kA; the study reads the clearing time at both and keeps the higher energy. Below an instantaneous pickup, the lower current can wait six times longer. That is variation within one bolted-fault scenario. A minimum network condition, with fewer sources or a generator supply, is a separate scenario with its own bolted current, and it needs its own pair of arcing currents. The Saudi Arabian Grid Code makes the transmission operator supply maximum and minimum short-circuit data at the connection point; ask for the minimum in writing. The Saudi Distribution Code, which governs most building connections, could not be retrieved for this episode.

De-energize first; engineering controls before the suit.

NFPA 70E-2024 110.2 makes hazard elimination the first priority and requires an electrically safe work condition before work within the limited approach boundary or where arc flash likelihood is raised; energized work is permitted only where de-energizing is infeasible or adds hazard, and then under a permit (130.2) by qualified persons. Its hierarchy (110.3(H)(3)) runs elimination, substitution, engineering controls, awareness, administrative controls, and PPE last. Where energized work is justified, on the example board zone-selective interlocking at 70 ms gives 2.5 cal/cm², an arc-flash relay with a 3-cycle breaker about 55 ms and 2.0, and a 30 ms maintenance setting 1.1. NEC 240.87 asks for an energy-reduction method at 1200 A and above, performance-tested when first installed. Saudi codes we read do not, so write the verification into the tender: sensing, logic, trip path, indication and total clearing time.

Containment, distance, the ensemble, and heat.

Arc-resistant switchgear contains an internal arc only within its tested rating and as installed: the rated accessibility type, doors and covers in the configuration the rating names, vents, ducts or plenum, current and duration. IEEE C37.20.7 Type 2B keeps the rating with the identified low-voltage control or instrument compartment doors open, for people 4 in or more from the opening; a power compartment door (breaker, bus, cable) open is outside the rating. No rating lowers the incident energy or by itself removes the risk assessment and the PPE it sets. Remote racking leaves the energy alone; the added distance reduces exposure, so run it from outside the verified 3.3 m boundary wherever practicable. Fitting the device, or opening a door to reach the breaker, inside the boundary is a task of its own: assess it and wear the PPE it needs. PPE is an ensemble: with the energy method, NFPA 70E Table 130.5(G) adds face and head, hand, hearing and foot protection to clothing rated at least E, and shock protection is assessed separately. An arc rating is a median, not a ceiling: at exactly its rating, clothing gives a 50% chance of a second-degree burn. And because the model has no temperature term, a Gulf switchroom gets the same cal/cm² as a cool one; the heat shows up as stress inside a 40 cal/cm² suit.

An input read on site
Same board, same current, 3.9 times the energy
VOA, vertical in open air3.3HOA, horizontal in open air5.8VCB, vertical in a box7.1VCBB, box with a barrier9.6HCB, horizontal in a box12.6
Assume VCB on a board whose bus is horizontal and this example understates the energy by 44%.
Design it down
Take time off the clock, not cloth off the shelf
short-time delay, 0.5 s17.7zone interlocking, 70 ms2.5arc-flash relay, 55 ms2.0maintenance setting, 30 ms1.1remote rackingsame energy; operate outside the 3.3 m boundaryarc-resistant gearsame energy; protects only in its tested door set-up
Remote racking adds distance, cutting exposure: run it from outside the verified boundary wherever practicable. Fitting it or opening a door inside the boundary is a separate task: assess it and its PPE.
The label
Two label rules: NEC marking, NFPA 70E content
WARNING: arc flashnominal voltage380 Varc flash boundary3.3 menergy at 610 mm17.7 cal/cm²assessment datedd/mm/yyyyone method: compliantWARNING: arc flashnominal voltage380 Varc flash boundary3.3 menergy at 610 mm17.7 cal/cm²assessment datedd/mm/yyyyplus PPE category 3both: not permitted
Review the assessment after any change that affects it, and at least every 5 years. Print one method's result, never an energy and a category together.
Write this instead

The clause to write

Five lines, each naming a document, a quantity or a test, so a tender can check them.

a. Arc flash risk assessment to NFPA 70E (edition stated), energy by IEEE 1584-2018, study scope to IEEE 1584.1-2022, for equipment likely to be worked on energized.

b. Per location: voltage, electrode configuration, gap, enclosure and working distance as built; maximum and minimum fault data from the network operator in writing.

c. Both arcing currents for each fault scenario, each with the clearing time read from the device curve and settings.

d. PPE by the incident energy method only: clothing, face and head, hands, hearing, feet; labels dated, reviewed after any change and within 5 years.

e. Each energy-reducing scheme functionally verified at commissioning: sensing, logic, trip path, indication and total clearing time, by manufacturer-approved procedures.

None of it permits energized work: that needs its own justification and permit.

From the Academy to the Field

Build the clearing time into the gear, then keep proving it.

NLC assembles Schneider-licensed low and medium voltage boards: MV switchgear published as IAC-AFLR, Form 4b motor control centres, and main distribution boards with optional arc-flash protection and detection. Its maintenance contracts include secondary-injection relay testing and breaker timing, which is how you confirm the clearing time a study assumed still holds. NLC does not publish arc flash studies; bring the study, and the switchgear can be built to its clearing times.

See the solution
Next Episode

Harmonics & THD

Watch next

Get the next episode by email

Practical lighting know-how from NLC Academy. No spam, unsubscribe anytime.

By subscribing you agree to receive NLC emails.

Sources

Sources & further reading

The clause, the edition, and what each document does not say.

Shareable

Forward the carousel to a colleague

An 18-slide explainer, ready to post straight to LinkedIn as an image carousel. Same content, faster reading.

Slide 1
Slide 9
Slide 16
Download 18 PNGs or grab the PDF