Ferroresonance
Study (PSCAD)
Overview
Ferro resonance is a nonlinear resonance phenomenon that arises from the interaction between the nonlinear magnetic inductance of a transformer core and system capacitance. It can produce sustained overvoltage’s several times the normal operating voltage, causing insulation breakdown, protection maloperation, equipment damage, and, in extreme cases, transformer destruction.
What the Study Covers
Nonlinear magnetic characterisation
Ferro resonance is notoriously difficult to predict using conventional linear analysis methods. PSCAD electromagnetic transient simulation is the accepted industry tool for its assessment. Our study covers:
Network Identification
Identification of network configurations susceptible to ferro resonance (isolated neutrals, single-phase switching, cable-fed transformers)
Magnetic Saturation
Modelling of transformer magnetic saturation characteristics using the Jiles-Atherton or piece-wise linear hysteresis model
Parametric Mapping
Systematic PSCAD simulation across the parametric space of capacitance and transformer loading to map ferro resonance zones
Overvoltage Quantification
Overvoltage magnitude and duration quantification for affected busbars and equipment
Mitigation Evaluation
Evaluation of mitigation measures: damping resistors, neutral earthing resistors, surge arresters, and altered switching sequences
Residual Flux Analysis
Residual flux sensitivity analysis for worst-case initial conditions
Applicable Standards
-
01
IEC 60071
Insulation coordination — referenced for overvoltage classification and mitigation principles
-
02
CIGRE Guidelines
Technical Brochure 569 and related working group publications on transformer ferro resonance
Typical Applications
Ferro resonance studies are particularly important for cable-fed transformer configurations, voltage transformer circuits, isolated neutral systems, and wind/solar plant collector network transformers during single-phase switching or islanded operation.
Benefits
Prevents high-value transformer failures and costly unplanned outages
Identifies and eliminates ferro resonance risk before energisation, not after damage occurs
Supports the engineering justification for switching procedure design and interlock logic
Provides defensible technical evidence for equipment warranty and insurance purposes
Why We Are the Best for Ferroresonance
Studies in India
Ferro resonance is one of the most under-assessed risks in India's rapidly expanding renewable energy sector. As solar and wind project developers push for cost reduction by using long MV cable feeders and lightly loaded step-up transformers during partial generation, the conditions for ferro resonance become increasingly common — yet the phenomenon remains poorly understood and frequently overlooked during design review.
Our team is among the very few in India with genuine PSCAD expertise in ferroresonance analysis. We do not treat this as a theoretical checklist exercise. We build detailed nonlinear transformer models using actual core saturation data, incorporate the exact cable capacitance from the project's cable schedule, and simulate hundreds of switching scenarios to fully characterise the ferroresonance risk space — including sensitivity to residual flux, the most commonly neglected variable.
- → One of India's most experienced teams for PSCAD-based nonlinear ferroresonance simulation
- → Transformer hysteresis modelling using manufacturer-supplied saturation curves, not generic library data
- → Systematic parametric studies covering all credible switching scenarios, not just the nominal design case
- → Practical mitigation design: damping resistor sizing, neutral earthing equipment specification, and safe switching procedure definition
- → Post-incident investigation capability: if ferroresonance has already caused damage, we reconstruct the event and identify root cause
