Megger’s 5-kV and 10-kV Insulation Resistance Testers

The new range of insulation resistance testers consists of three models: two 5 kV units (MIT515 and MIT525) and a 10 kV unit (MIT1025). Resistance measurement is available up to 10 T? for the 5 kV models and 20 T? for the 10 kV model. The new instruments are smaller and lighter than previous models yet offer advanced features and rapid charge capability.

A key productivity feature is the ability to take measurements when connected to line power/mains with a dead battery. Intelligent battery charging ensures the optimum charge rate as a function of battery level, resulting in minimum charge times.

The rugged, unique dual case design provides the ultimate protection for a portable instrument and a clip-on lead pouch ensures that leads remain with the instrument at all times. The case lid is removable for improved terminal access. IP rating is IP65 with the case closed preventing water/dust ingress. High reliability and safety are built in; all models are safety rated to CATIV 600 V and are double insulated.

Five preset voltage ranges are provided in insulation test mode, plus a user settable lock voltage range. Any selectable test voltage may be locked and restored via the selector switch, thereby increasing efficiency of commissioning and repetitive tests. Preconfigured diagnostic tests include Polarization Index (PI), Dielectric Absorption Ratio (DAR), dielectric discharge (DD), Step Voltage (SV) and ramp test.

The ramp function gradually increases voltage up to a selected level while graphing current vs. voltage (graph downloadable). Graphs can be compared to example curves in IEEE 95-2002 to reveal a variety of faults difficult to detect otherwise. Small defects can be easily detected without risking the sudden large voltage increments produced by a Step Voltage test. Monitoring the developing graph during test enables the operator to terminate prior to breakdown, thereby reducing the possibility of damage to already flawed insulation. These units are particularly informative on polyester, asphalt and epoxy-mica insulations. They can also test voltage suppression devices.

Simplicity of operation is achieved with two rotary switches and the large backlit display enables multiple results to be displayed simultaneously.

Advanced memory storage includes time/date stamping of results, logging of data and recall of results to screen. A fully isolated USB device interface (type B) is used for safe transfer of data to Megger’s PowerDB asset management software.

Applications

The units are designed for testing the insulation of high-voltage electric equipment. Their wide voltage range also allows applications for low-voltage equipment. Generators, motors, transformers, cables and switchgear all require effective maintenance. The test techniques on the instruments provide valuable diagnostic information.
They are ideal for:

• Electrical contractors
• Testing and service companies
• Wind farm and solar generation operators
• Power generation and distribution companies
• Industrial companies
• Rail companies

All three instruments test the insulation resistance of:

• High-voltage power cables and high-voltage buses
• Large motor/generator windings
• Line and substation transformers

The MIT525 and MIT1025 also perform spot tests, stepvoltage tests, dielectric discharge tests, ramp tests, and dielectric absorption tests for the following applications:

• Acceptance testing at installation to check conformance to specifications.
• Routine preventive/predictive maintenance testing after installation.
• QA testing as part of the manufacturing process
• Diagnostic testing to isolate faulty components for repair.

With its higher voltage testing capability, the MIT1025 is the perfect everyday work tool for manufacturers, users and maintainers of rotating machinery. Designed in accordance with the requirements of IEEE43:2000, the MIT1025 is ideal for measuring the insulation resistance of armature and field windings in rotating machines rated 1hp (750 W) or greater. The standard applies to synchronous, induction and dc machines as well as synchronous condensers.

What’s Included

• USB cable (MIT525, MIT1025 only)
• PowerDB Lite software
• 3 m leadset x 3, medium insulated clips
• 3 m leadset x 3, large insulated clips (MIT1025 only)
• Power lead