SIST EN 60156:1997

Overview

EN 60156:1995 - Insulating liquids - Determination of the breakdown voltage at power frequency - Test method (published by CLC; identical to IEC 156:1995) specifies an empirical laboratory test to assess the dielectric strength (breakdown voltage) of insulating liquids. The procedure is intended to indicate the presence of contaminants such as water and solid suspended matter, and to help determine whether drying or filtration treatment is advisable. The standard emphasizes the need for standardized testing procedures and equipment to ensure unambiguous interpretation of results.

Key Topics

• Scope and purpose: Defines the objective of the power-frequency breakdown voltage test as a diagnostic for contamination and oil condition.
• Test principle: Empirical method to measure breakdown under power-frequency stress; result used as an indicator of insulating liquid quality.
• Sampling and sample handling: Guidance on obtaining representative samples and avoiding contamination during transport and preparation.
• Test equipment and electrode configuration: Requirements for standardized test cells and electrodes to ensure repeatable measurements.
• Test procedure and reporting: Sequence of steps, number of breakdown measurements, and how to record and report results for consistency.
• Interpretation and action: Using breakdown voltage values to infer contamination (e.g., free or dissolved water, particulate matter) and to decide on remedial actions such as drying or filtration.
• Quality assurance: Importance of calibration, operator competence, and controlled test conditions to achieve reliable, comparable results.

Applications

• Routine transformer oil testing and acceptance testing of insulating liquids in power equipment.
• Condition monitoring by utilities and asset owners to detect contamination early and plan maintenance (drying, filtration).
• Quality control in manufacturing of insulating fluids and components containing dielectric liquids.
• Independent test laboratories performing dielectric strength and breakdown voltage testing for compliance, procurement, and failure investigation.
• Use in maintenance decision-making for electrical equipment such as transformers, switchgear, and bushings.

Who Uses This Standard

• Power utilities and transmission operators
• Transformer manufacturers and service companies
• Accredited test laboratories and quality-control teams
• Maintenance and reliability engineers
• Standards and regulatory bodies referencing dielectric testing methods

Related Standards

• Harmonized with IEC 156:1995 (same test method).
• Often used alongside other insulating-liquid standards and specifications for oil purity, moisture content, and component testing (refer to current IEC/EN series on insulating fluids for complementary methods).

Keywords: EN 60156, insulating liquids, breakdown voltage, power frequency, dielectric strength, transformer oil testing, IEC 156, oil testing, contamination detection.