Megger MJOLNER 600 Microhmmeter

Megger MJOLNER 600 Micro-Ohmmeter

The Megger MJOLNER 600 is a 600 A micro-ohmmeter built for precision low-resistance measurements on circuit breaker contacts, busbar joints, earthing connections, and other high-current paths. The product has been designed with safety and DualGround testing in mind, so substation engineers and electrical contractors in Ireland can measure a low resistance value with high accuracy without having to lift the second earth from the breaker under test.

Where you have a high-current conductor, you have a contact resistance that should not be drifting upward. The MJOLNER 600 is the test set you reach for when a few microhms of contact wear is the early warning of overheating, joint failure, or a breaker that will not deliver its rated interrupting performance the next time it is asked to.

What the MJOLNER 600 measures and why it matters

• Contact resistance of circuit breakers: detect contact wear and erosion before it becomes a thermal problem.
• Busbar joints and connections: verify that bolted connections in switchgear and busbar runs are tight, clean, and within specification.
• Earthing and bonding: confirm that high-current earthing paths are doing their job.
• Welded and bolted contact elements in bus-bars: pinpoint loose or oxidised connections that show up as a higher resistance reading.
• Cable joints and terminations: trend resistance values over time as part of a condition-based maintenance programme.

The point of low-resistance testing is not the absolute value, it is the trend. A reading taken today, compared with the commissioning baseline and the last maintenance reading, tells you whether a connection is healthy, drifting, or about to cause a real problem. The MJOLNER 600 gives you the accuracy and repeatability that makes that trending meaningful.

DualGround testing and operator safety

DualGround means that both sides of the breaker can be earthed throughout the test. That removes the induced-voltage hazard you would otherwise have to manage on a live substation, and it removes the need to lift one earth and rely on procedure alone to keep the operator safe. The MJOLNER 600 is designed around DualGround, which is why it has become a substation-favourite micro-ohmmeter in Irish utility and industrial sites.

Specifications: what to confirm before you order

Target users and applications

• Utilities and DNOs running substation maintenance and outage testing
• Electrical engineers commissioning new switchgear and verifying contact resistance against factory data
• Electrical contractors carrying out planned preventative maintenance on industrial switchgear
• Renewable power operators testing interconnection switchgear, collector busbars, and BESS connections

Typical applications include circuit breaker maintenance, busbar joint verification, switchgear commissioning, fault-finding after a thermal event, and benchmarking new equipment against its factory test sheet.

As authorised Megger distributor in Ireland, Powerpoint Engineering supports the MJOLNER 600 with in-house calibration and repair, accessory supply, and operator training for substation low-resistance testing.

FAQs

Why use a 600 A micro-ohmmeter instead of a lower-current meter?

Higher test current overcomes contact film and oxidation that can give false-low readings on small instruments, and it is closer to the conditions the contact will see in service. For circuit breaker and busbar resistance measurements, a 600 A micro-ohmmeter is the appropriate tool.

What does DualGround mean and why does it matter?

DualGround testing keeps both sides of the breaker earthed for the duration of the test. It removes the induced-voltage hazard that comes with a single-grounded approach and is now mandated by many utility safe-systems-of-work procedures.

Does the MJOLNER 600 need recalibration?

Yes. Like any precision test instrument, the MJOLNER 600 should be recalibrated periodically to remain trusted. Powerpoint Engineering's calibration laboratory recalibrates Megger micro-ohmmeters in-house and supplies a traceable certificate.

To match the MJOLNER 600 to your breaker fleet, busbar geometry, and test workflow, request a quote or speak to our team for compatibility advice.