H‑Infinity

Short circuit analysis is essential for safety, reliability, and equipment protection. High fault currents can release devastating energy through insulation failures — we help you quantify these risks, size your equipment appropriately, and coordinate protection systems to respond correctly.

01What is a Short Circuit Study

A short circuit study calculates the magnitude of fault currents that could flow at every point in your electrical system during different types of faults — three-phase, line-to-ground, line-to-line, and line-to-line-to-ground. These currents can reach enormous levels, releasing destructive energy through insulation failures in fractions of a second.

The study determines whether your existing equipment — circuit breakers, fuses, transformers, cables, busbars, and switchgear — has adequate interrupting and withstand ratings to safely handle these fault currents. It also provides the data needed to coordinate protective devices so that only the nearest device to a fault operates, isolating the minimum possible section of the system.

02Why It Matters

Fault currents carry immense energy that, if not properly managed, can cause:

⚠ Safety Hazards

Arc flash explosions, equipment rupture, fire — all direct threats to personnel working in or near electrical installations.

⚠ Equipment Damage

Thermal and mechanical stress from fault currents can destroy transformers, melt busbars, and destroy switchgear beyond repair.

⚠ Unplanned Downtime

Incorrect protection coordination causes unnecessary trips, spreading outages across sections that should remain operational.

⚠ Regulatory Non-Compliance

Electrical installations must comply with short circuit rating requirements — failure can result in prosecution and invalidated insurance.

03When to Conduct Short Circuit Studies

We recommend conducting short circuit studies:

▸Initially — As part of the design phase for new installations, to verify equipment ratings and ensure adequate fault levels from the outset.
▸Periodically — Ideally every 5 years, as grid strength and system configuration evolve, potentially altering fault levels at your point of connection.
▸After any system modification — Following the addition of new generators, cable upgrades, transformer replacements, or network reconfiguration.
▸Following a fault incident — When a fault has occurred and protection behaviour was uncertain, to investigate and prevent recurrence.

04Our Approach

1. System Data Collection

Utility fault contribution at the point of common coupling, transformer impedances, cable lengths and sizes, generator subtransient reactances, motor contributions, and protective device settings.

2. Fault Calculation

Symmetrical and asymmetrical fault currents at all critical buses for all fault types, including contribution from rotating machinery and utility source.

3. Equipment Rating Verification

Compare calculated fault currents against the interrupting and withstand ratings of all protective devices, switchgear, and conductors.

4. Protection Coordination

Develop time-current curves (TCC) for all protective devices to verify selective coordination and minimised fault clearance zones.

05Standards & Compliance

✓ANSI/IEEE C37 series

✓IEC 60909 — Short Circuit in AC Systems

✓IEC 61363 — Offshore & Mobile Installations

✓NFPA 70E — Electrical Safety

06Why H-Infinity

Our team has undertaken short circuit and protection studies for many large and complex installations across the UK. We understand the real-world implications of fault current calculations — not just the numbers, but what they mean for your equipment, your people, and your operational continuity.

Every study includes clear, prioritised findings with specific recommendations — whether that means upgrading circuit breakers, adjusting protection settings, or implementing fault current limiting solutions.

Short Circuit Study