Power System Studies

Insulation Coordination Study

Lightning impulse, switching surge analysis, and surge arrester sizing.

Lightning strike to the incoming line. Capacitor bank switching transient. Restrike on circuit breaker opening. Each generates an overvoltage waveform that the BIL of your transformers and busbars must withstand. We simulate it in EMTP / PSCAD, size the surge arresters, and verify the protection margin · before the next monsoon.

Why this matters

Why transformer failures attributed to lightning are usually arrester sizing failures

Every monsoon brings a wave of transformer and switchgear failures attributed to lightning. In the post-mortem, the lightning event is real · but the actual failure mode is usually inadequate surge arrester sizing, arrester ageing, or surge arrester location not optimised. An insulation coordination study simulates lightning and switching surges, verifies the protection margin between the arrester protective level and the equipment BIL, and lets you specify a coordinated arrester scheme that actually does its job · plus a 5-year arrester inspection programme tied to your AMC.

Method

How we deliver Insulation Coordination Study

CEng MIE India-signed deliverables · LiDAR-powered where applicable · digital twin handover ready · routes to the Power System Studies practice lead within 24 hours.

Equipment BIL inventory

Lightning Impulse Withstand Level (BIL) and Switching Impulse Withstand Level (SIL) for every transformer, busbar, breaker, and CT/PT captured from nameplates and routine test reports.

Lightning + switching surge modelling

EMTP-RV or PSCAD model. Standard lightning waveshape (1.2/50 µs), standard switching surge (250/2500 µs), realistic stroke currents per IEC 60071-2 statistical method.

Arrester sizing

MCOV (Maximum Continuous Operating Voltage), TOV (Temporary Overvoltage) capability, energy class, and protective level computed. Distance-to-protected-equipment analysed.

Protection margin verification

Margin between arrester protective level and equipment BIL computed per IEC 60071-2 / IEEE 1313.2 deterministic or statistical method. Inadequate margins flagged.

Recommendations + sign-off

Arrester make/model/location specified per substation. Existing arrester replacement programme prioritised by margin shortfall. CEng MIE-signed.

Standards + compliance

Built to the standards your auditors quote

Reports reference the international and national standards your regulators, F500 audit teams, and corporate process safety leads cite. Every deliverable signed by a Chartered Engineer (CEng MIE India).

IEC 60071-1 / 60071-2 · Insulation Coordination
IEEE 1313.1 / 1313.2 · Insulation Coordination Definitions + Application Guide
IEC 60099-4 · Metal-oxide surge arresters without gaps for AC systems
IEEE C62.11 · Metal-Oxide Surge Arresters for AC Power Circuits
IS 3070 / IS 2026 · Surge arresters + transformer specifications (India)

Anonymous case anchors

What this looks like in production

Three landmark engagements from our verified roster · quantified outcomes, no client names disclosed without written permission.

Power plant, India · 220 kV substation

Two transformer failures in 18 months attributed to lightning. Insulation coordination study found arrester protective level inadequate margin. Re-spec arrester scheme. No further failures in next 4 monsoons.

LNG terminal, Qatar · GIS substation

Switching surge from VCB closure exceeded GIS bushing SIL margin. Designed pre-insertion resistor + surge capacitor solution.

Mine, Australia · long incoming transmission

20 km incoming line with multiple strike points. Statistical analysis sized arresters at line entry + transformer. Failure rate dropped from 2/year to 0.

Frequently asked

Insulation Coordination Study · the practical questions

Is insulation coordination needed for indoor MV switchgear?

Reduced scope · indoor MV substations are largely shielded from lightning, but switching surge analysis is still required for capacitor banks, motor switching, and breaker restrike scenarios. Full lightning analysis applies to outdoor substations.

Deterministic or statistical method?

Deterministic for typical industrial substations (margin × arrester protective level vs equipment BIL). Statistical for critical assets (large generator step-up transformers, high-risk locations) where probability of failure is justifiably analysed.

Do you specify exact arrester make / model?

We specify protective level, MCOV, energy class, and rating. Make / model selection follows from your procurement preference (ABB, Siemens, tier-1 platform, Hubbell). We have shortlists for each region.

Can you supervise commissioning?

Yes · arrester counter installation and grounding verification supervised by our field engineers. Common defect: arrester ground lead too long, defeats the protective function. We catch this on site.

How does this tie into your safety AMC?

Arrester inspection is part of our 5-year Safety AMC scope · annual visual + thermographic + counter readout. Failing arresters identified before they fail to protect.

Scope your Insulation Coordination Study engagement.

Tell us your plant, region, and scope · a named Chartered Engineer responds within 24 hours.

4 fields. No phone interview to start.
Per-discipline routing to the Power System Studies practice lead.
Anonymous case anchors sent with first reply.
Same-day callback for deadline-driven enquiries.

Power System Study Scoping

ETAP/DigSILENT/PSCAD-led · routes to Practice Lead PSS · 24-hour response.