BSG method: safe micro-ohm measurement in high-voltage installations

What is the BSG method?

The BSG method lets you measure while both sides of the test object stay connected to ground. This matters for circuit breakers, disconnectors, or busbar connections in substations, where strong electromagnetic fields can occur.

By keeping both sides grounded:

• the test object stays at a safe potential during the entire measurement,

• the risk of dangerous voltage differences is reduced,

• and both operator and instrument stay protected.

How does it work in practice?

During a BSG test, an auxiliary current clamp is connected to the grounding of the test object. It measures the return current to earth, so the instrument can compensate for it and still give accurate readings. The test object stays grounded throughout.

The procedure:

1. Connect the test leads as described in the manual.

2. Place the auxiliary clamp on the ground connection of the object.

3. Activate BSG mode in the menu.

4. Start the test. Both sides remain grounded, while the instrument displays resistance and ground current.

Why is this important?

In substations and industrial environments, induction from nearby high-voltage lines can create hazardous potential differences. Without BSG mode, one side of the test object would have to be disconnected from ground, which adds risk.

With the BSG method:

• safety procedures stay intact,

• measurements align with utility guidelines,

• and micro-ohm results stay reliable.

Applications

The BSG method is useful for:

• High-voltage circuit breakers

• Disconnectors and busbar systems

• Maintenance testing in substations

• Environments with strong electromagnetic fields

With the BSG method, you can keep the test object grounded and still measure accurately, instead of choosing between the two.

The Megabras MPK215R micro-ohmmeter supports the BSG method as standard. Contact IONIO for advice on using it in your substation maintenance or FAT/SAT testing.

Read the complete guide to micro-ohm measurement.