DIN 51111:2024-02
Electrical properties of fresh and used oils from electric drives in vehicles - Measurement of the specific electrical conductivity, the relative permittivity (<epsilon><(Index)r>) and the dielectric dissipation factor (tan <delta>)

Standard No.

DIN 51111:2024-02

Release Date

2024

Published By

German Institute for Standardization  DE  /  DIN

Latest

DIN 51111:2024-02

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Introduction

Analysis of the core content of the standard

DIN 51111:2024 proposes a standardized method for testing the electrical properties of fresh oil and used oil in electric vehicle drive systems. The main measurement parameters include:

Test parameters	Measurement range	Key equipment	Typical temperature points
Conductivity (σ)	nS/m level	Impedance meter	50°C/100°C/150°C
Relative permittivity (εr)	1.8-2.5	Cylindrical measuring cell	Same as left
Dielectric loss factor (tanδ)	10-4-10-1	Temperature control unit	Same as left

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Technological Evolution Comparison

Compared with the DIN EN 60247 standard, the main improvements of the new version are reflected in:

• Extended measuring range: The lower limit of conductivity measurement is extended to the nS/m level (the old standard was μS/m level)
• Temperature adaptability: A new 150°C high-temperature test point has been added to better reflect the operating conditions of electric vehicles.
• Measurement principle: Low-frequency AC voltage (20Hz) is used to avoid electrode polarization effects.

Typical application case

Measured at 150°C for an electric vehicle transmission oil:

• Conductivity: 125±15nS/m
• Dielectric loss factor: 0.08±0.01
• Relative dielectric constant: 2.12±0.03

These data indicate that the oil still maintains good insulation properties (the standard requires tanδ<0.1)

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Key implementation points

1.

The standard strictly stipulates the cleaning process:

1. Preliminary cleaning with hydrocarbon solvents
2. Immerse in acetone for 15 minutes
3. Dry with compressed air (pre-filtration required)

2. Temperature Control

Temperature fluctuation is required to be ≤±0.1°C. It is recommended to use:

• External heating bath
• Electric heating block thermostat
• Built-in heating device for the measuring cell

3. Error Control

Main error sources:

Error type	Influencing parameters	Control measures
Bubble interference	εr measurement	Oil filling at 45° angle
Residual contamination	σ measurement	Operation with gloves
Temperature drift	tanδ	Complete measurement within 10 minutes

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Recommendations for standard implementation

1. Equipment selection: Prioritize an impedance analyzer that supports automatic measurement in three temperature zones
2. Quality control: Calibrate the equipment monthly using n-Decan (see Table 1 for standard values)
3. Data interpretation: The 50°C data reflects the influence of moisture, and the 150°C data represents the characteristics of the base oil
4. Result report: The measurement temperature, equipment model, and cleaning records must be included

DIN 51111:2024-02 history

• 2024 DIN 51111:2024-02 Electrical properties of fresh and used oils from electric drives in vehicles - Measurement of the specific electrical conductivity, the relative permittivity (<epsilon><(Index)r>) and the dielectric dissipation factor (tan <delta>)
• 2024 DIN 51111:2024 Electrical properties of fresh and used oils from electric drives in vehicles - Measurement of the specific electrical conductivity, the relative permittivity (?<(Index)r>) and the dielectric dissipation factor (tan ?)
• 2023 DIN 51111:2023-04 Electrical properties of fresh and used oils from electric drives in vehicles - Measurement of the specific electrical conductivity, the relative permittivity (<epsilon><(Index)r>) and the dielectric dissipation factor (tan <delta>) /...
• 2023 DIN 51111 E:2023 Draft Document - Electrical properties of fresh and used oils from electric drives in vehicles - Measurement of the specific electrical conductivity, the relative permittivity (?<(Index)r>) and the dielectric dissipation factor (tan ?)

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