Sandbox

Build a bus, sweep the scenario.

Two widgets, both editable. The first composes a short-circuit calculator above an arc-flash calculator — build a bus, the PPE category for that bus is computed live. The second is the TCC-bridge — drag the upstream LVPCB's settings and watch the arc-flash energy track its clearing time.

Educational tool only. Implements the IEEE 1584-2002 LV regression with simplified per-unit fault math. Outputs are not suitable for arc-flash labels, PPE selection, breaker rating, or any safety-critical engineering decision. Use a licensed production tool and consult a qualified protection engineer for any real-world arc-flash or coordination study.

1 · Scenario preset → topology → arc-flash label

Pick a named scenario to seed the one-line and arc-flash math, then pick a topology, pick the active bus, and see the short-circuit and arc-flash labels respond. On the double-ended diagram, the tie breaker is interactive — closing it parallels the two transformers and roughly doubles Isc at either bus, which the PPE category below tracks immediately.

Scenario preset

Pass 4's canonical scenario: 500 MVA utility, 1500 kVA / 5.75 % transformer, 480 V switchgear at 24 in working distance, 200 ms clearing.

Topology

One-line diagram — preset: Default — 480 V commercial

Linked — arc-flash inputs below are driven by the short-circuit output above.

Ibf 29.8 kA

Arc-flash label (driven by linked Ibf above)

Incident energy 5.8 cal/cm²

Arc-flash boundary 70 in (1783 mm)

PPE Category 2

Arc-rated clothing min 8 cal/cm² — shirt + pants or coverall, hood, balaclava, gloves.

Arcing current

13.5 kA

≈ 54% of Ibf

Bolted Isc

25.0 kA

Clearing time

200 ms

Model

IEEE 1584-2002

System

Voltage 480 V

Grounding

IEEE 1584 model 1584-2002

Toggle pending — see the lesson note in L4.

Bolted fault current Ibf kA

Geometry

Electrode config Vertical in box (switchgear)

Gap between conductors 32 mm

Working distance 24 in

Clearing time t ms (12.0 cyc @ 60 Hz)

Includes device opening time. A 5-cycle breaker tripping instantaneously at 60 Hz ≈ 83 ms.

2 · Short-circuit → arc-flash label (no topology overhead)

Same linkage as above, just without the topology picker — useful when the bus shape is fixed and you only want to sweep the source impedance. Uncheck the link if you want to compare a what-if scenario without changing the bus.

Linked — arc-flash inputs below are driven by the short-circuit output above.

Ibf 29.8 kA

Arc-flash label (live from above)

Incident energy 5.8 cal/cm²

Arc-flash boundary 70 in (1783 mm)

PPE Category 2

Arc-rated clothing min 8 cal/cm² — shirt + pants or coverall, hood, balaclava, gloves.

Arcing current

13.5 kA

≈ 54% of Ibf

Bolted Isc

25.0 kA

Clearing time

200 ms

Model

IEEE 1584-2002

System

Voltage 480 V

Grounding

IEEE 1584 model 1584-2002

Toggle pending — see the lesson note in L4.

Bolted fault current Ibf kA

Geometry

Electrode config Vertical in box (switchgear)

Gap between conductors 32 mm

Working distance 24 in

Clearing time t ms (12.0 cyc @ 60 Hz)

Includes device opening time. A 5-cycle breaker tripping instantaneously at 60 Hz ≈ 83 ms.

3 · TCC bridge — clearing time linked to a real protective device

The upstream LVPCB's curve drives the clearing time on the arc-flash calc below. Drag the device's I pickup or S delay, watch the IE label move. Move the bus Isc slider to see how the same device behaves at different fault levels.

Bus available fault current (Isc) kA

The vertical line on the plot marks the fault current. The upstream device's curve at that current sets the clearing time below.

1600 A main LVPCB Sensor rating A

Long-time (L)

L pickup × (1440 A) L delay (@ 6× pickup) s

Short-time (S)

S pickup × (8000 A) S delay s S I²t in (sloped band)

Instantaneous (I)

I pickup × (OFF)

Resulting arc-flash label

Incident energy 5.8 cal/cm²

Arc-flash boundary 70 in (1783 mm)

PPE Category 2

Arc-rated clothing min 8 cal/cm² — shirt + pants or coverall, hood, balaclava, gloves.

Arcing current

13.5 kA

≈ 54% of Ibf

Bolted Isc

25.0 kA

linked

Clearing time

200 ms

linked

Model

IEEE 1584-2002

System

Voltage 480 V

Grounding

IEEE 1584 model 1584-2002

Toggle pending — see the lesson note in L4.

Bolted fault current

Driven externally: 25.0 kA

Geometry

Electrode config Vertical in box (switchgear)

Gap between conductors 32 mm

Working distance 24 in

Clearing time

Driven externally: 200 ms

Things to try

Sweep transformer %Z in widget 1. As you raise %Z from 5.75 % to 7.5 %, Ibf falls and the PPE category steps down with it — both panels update together because the link is on by default.
Toggle the link off in widget 1 to compare a what-if Ibf against the actual bus Ibf. Useful for stress-testing "what if my AIC margin shrinks 20 %?" without changing the source path.
Sweep the clearing time in widget 1 — start at 50 ms (fast device with INST on) and walk up to 1 s. The PPE category climbs from Cat 1 up to Cat 4.
Compare grounded vs ungrounded systems in widget 1. The grounding K2 factor adds about 30 % to incident energy for ungrounded (10^0.113 ≈ 1.3×) — modest but real.
Walk the LVPCB in widget 2 from "no INST" to "INST at 5×." The clearing time at 25 kA drops from ~200 ms to one cycle. Cat 2 drops to Cat 1.
Increase the bus Isc in widget 2 to 50 kA. With INST off, the IE label grows nearly linearly with Isc. With INST on, the LVPCB still clears in a cycle and IE stays well below Cat 2.

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