Everything about measurement in electrical installations
Insulation resistance is one of the central parameters for the safety and functionality of electrical installations. Reliable insulation protects against short circuits, leakage currents, and extends the service life of electrical equipment. In this article, we explain what insulation resistance is, how it is measured, and which standards apply.
GOBA supplies insulation materials with defined insulation resistance values for motors, transformers and switchgear.
What is insulation resistance and why does it matter?
Definition of insulation resistance
Insulation resistance describes the ability of an insulating material to prevent current flow between electrical conductors. A high resistance value indicates that the insulation is intact and no leakage currents occur.
Significance in electrical installations
Sound insulation protects:
- Against electrical accidents, for example through leakage currents
- Electrical devices from damage
- Installations from failures due to insulation faults
Consequences of low insulation resistance
- Short circuits and fire risk
- Accelerated ageing of equipment
- Potential personal injury from electric shock
How does the measurement of insulation resistance work?
Use of a measuring instrument for insulation measurement
A measuring instrument, such as an insulation tester, measures the resistance between conductors or between conductors and earth. A test voltage is applied, usually 500 V or 1000 V DC.
Influence of test voltage and DC voltage
Direct current (DC) prevents capacitive effects that could distort the result. The higher the test voltage, the more accurate the measurement.
Standards such as VDE and DIN for measurement
The quality of the insulation material and the cleanliness of the conductor surface have a direct influence on the insulation resistance.
Which test instruments are used for insulation measurement?
Types of measuring instruments
- Handheld insulation testers: compact and ideal for on-site measurements
- Stationary test instruments: for comprehensive tests in industrial applications
- Multimeters with insulation function: for basic resistance measurements
How to select a suitable test instrument
- Verify that the instrument complies with DIN VDE standards
- Ensure that the test voltage suits your application (for example 500 V DC)
- Look for features such as automatic no-load voltage detection and measurement data storage
Influence of insulating materials and conductors
The quality of the insulation material and the cleanliness of the conductor surface have a direct influence on the insulation resistance.
How is insulation resistance calculated?
Insulation resistance is calculated according to Ohm's law, where U is the applied test voltage and I is the measured leakage current.
R = U / I
Which standards and limit values apply to insulation resistance?
Overview of limit values according to DIN VDE
- For electrical installations: at least 1 MΩ at 500 V DC
- For Class I equipment: at least 2 MΩ
- For Class II equipment: at least 7 MΩ
Differences in electrical installations
Typical values depending on the application area:
- Household appliances: 2 to 10 MΩ
- Industrial installations: 10 to 100 MΩ or more
- High-voltage systems: above 1 GΩ
Regular insulation resistance testing
Testing should be carried out regularly to ensure compliance with standards and to detect potential faults at an early stage.
GOBA Takeaway
Insulation resistance is a key parameter for ensuring the safety and efficiency of electrical installations. Through regular measurements and compliance with standards such as DIN VDE, potential hazards can be identified and eliminated before they cause serious consequences.