Insulation Coordination Study
Overview
Insulation coordination is the systematic process of selecting insulation levels for electrical equipment so that they withstand overvoltages that arise during lightning strikes, switching operations, and temporary power frequency overvoltages. A properly executed insulation coordination study prevents equipment failures, reduces outage risk, and optimises capital expenditure on surge protection.
What the Study Covers
Comprehensive overvoltage stress quantification
Using PSCAD transient simulations, we model the propagation of overvoltage surges through the network and assess the protective margin available at each equipment location. The study delivers a comprehensive insulation coordination plan covering:
Overvoltage Stresses
Classification and quantification of overvoltage stresses: lightning (impulsive), switching, and temporary (TOV)
Surge Arrester Strategy
Selection and placement of surge arresters (metal oxide varistors) across the network
Withstand Verification
Verification of withstand capability: Basic Insulation Level (BIL) and Switching Impulse Level (SIL)
Protective Margins
Protective margin calculations for transformers, cables, GIS, and switchgear
Shielding Effectiveness
Evaluation of shielding effectiveness for overhead lines and substations
Earthing Arrangements
Assessment of cable screen earthing and bonding arrangements
Applicable Standards
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01
IEC 60071
Insulation coordination for equipment within AC systems — procedures and principles
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02
IEEE C62 Series
IEEE Guide for the Application of Metal-Oxide Surge Arresters
Typical Applications
Insulation coordination studies are essential for substations at all voltage levels, GIS installations, cable-overhead line interfaces, transformer terminals, and wind/solar plant collector systems.
Benefits
Prevents premature equipment failure caused by inadequately specified insulation
Optimises surge arrester specification, avoiding both over- and under-protection
Reduces insurance premiums and lifecycle maintenance costs
Produces an audit-ready insulation coordination schedule for regulatory submission
Why We Are the Best for Insulation
Coordination Studies in India
India's high-voltage network — spanning 765 kV UHV lines, 400 kV interstate corridors, and dense urban GIS substations — presents a uniquely challenging insulation environment. The combination of high isokeraunic levels in many regions, mixed cable-overhead line topologies, and the rapid proliferation of GIS technology means that insulation coordination errors carry severe financial consequences.
Our engineers bring specific expertise in IEC 60071 methodology applied to Indian network conditions, including accurate lightning ground flash density (GFD) mapping, soil resistivity data integration, and arrester energy absorption analysis for long cable sections. We do not use conservative generic assumptions — every model parameter is justified against site-specific data.
- Advanced PSCAD surge propagation modelling with frequency-dependent transmission line models
- Site-specific lightning threat assessment using Indian Meteorological Department (IMD) isokeraunic data
- Arrester energy duty calculations validated against manufacturer EMTP characterisation data
- Expertise in both AIS and GIS substation insulation coordination, including mixed technology installations
- Studies accepted by major EPC contractors, transformer OEMs, and independent engineers for project financing
