ISO 18095:2018

Overview

ISO 18095:2018 - Condition monitoring and diagnostics of power transformers - provides practical guidelines for selecting and applying monitoring techniques when setting up a transformer condition monitoring programme. The standard applies to single‑phase AC power transformers ≥ 1 kVA and three‑phase AC power transformers ≥ 5 kVA and includes references to associated standards needed to implement a coherent, condition‑based maintenance regime (for example, in line with ISO 17359). It covers oil‑filled, dry‑type and gas‑insulated transformers and focuses on techniques that support early fault detection, life assessment and maintenance prioritization.

Key Topics and Technical Scope

ISO 18095:2018 organizes guidance around component failure modes, detection techniques and programme design. Key technical topics include:

• Transformer types: oil‑filled, dry‑type, gas‑insulated (GITs) and their monitoring implications.
• Failure mode analysis: component breakdown, dielectric, thermal, mechanical and external failure categories and influences on failure progression (loading, environment, design, maintenance, protection).
• Range of monitoring techniques: mains current/voltage/load monitoring, visual inspection, oil condition and dissolved gas analysis (DGA), partial discharge (PD) detection, thermography/temperature monitoring, ultrasound, vibration, acoustic/noise analysis, power factor/tan‑delta, resistance, dielectric frequency response (DFR/PDC/RVM), frequency response analysis (FRA), bushing capacitance, and novel/model‑based techniques.
• Programme establishment: guidance on selecting techniques individually and in combination, and choosing monitoring frequencies based on risk and asset criticality.
• Informative annexes on factors influencing paper‑based insulation life and example condition monitoring programmes.

Practical Applications

ISO 18095:2018 is used to design, implement and optimize transformer condition monitoring and condition‑based maintenance strategies. Typical applications include:

• Early detection of dielectric faults, thermal hotspots, mechanical deformation and PD activity.
• Prioritizing maintenance, scheduling interventions and extending asset life through targeted diagnostics.
• Integrating multiple monitoring methods (e.g., DGA + thermography + FRA) to improve diagnostic confidence.
• Defining monitoring frequency and data‑collection scope for on‑line and off‑line testing.

Who Should Use This Standard

• Utility and grid asset managers
• Power transformer maintenance and reliability engineers
• OEMs and transformer manufacturers
• Condition monitoring service providers and consultants
• Plant operators responsible for lifecycle cost and risk management

Related Standards

ISO 18095:2018 is intended to be used alongside other normative documents for transformer monitoring and maintenance practices, notably ISO 17359 for condition monitoring programme frameworks, plus the relevant industry standards referenced within ISO 18095 for specific test methods.