GE MiCOM MMLG 01, 02, 03, 04 Test Blocks


Simple access for injection testing, all within a compact block design

Test blocks offer monitoring and secondary injection testing facilities for any power system protection scheme, when used with the multi-fingered test plug type MMLB 01.
The MMLG test block carries 14 circuits, each of which is brought out to separate pairs of terminals at the rear of the case.
Each circuit comprises a pair of internal contacts which are normally sprung together to complete the circuit link through the block when the associated protective equipment is in normal service.

Key Benefits

 Test blocks can be mounted adjacent to 4U rack height relays and systems
 Test blocks eliminate the need to disturb protective system wiring for testing
 Monitoring, isolation and secondary injection testing are simplified and quickly performed.

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Models Available
 MMLG 01 Standard test block
 MMLG 02 Special test block designed for use in busbar protection schemes
 MMLG 03 Horizontal version of MMLG 01
 MMLG 04 Horizontal version of MMLG 02
 MMLB 01 Multi-finger test plug

The MMLG cover, when in place, provides protection from electric shock hazards. Access to internal circuits for testing purposes can be gained by removing the front cover. A metallic probe secured to the inside face of the MMLG 01 cover is automatically withdrawn when the cover is removed, thus interrupting the circuit between terminals 13 and 14. By routing the main DC auxiliary supply to the protection scheme or relay through this circuit, the removal of the test block cover will prevent inadvertent tripping of the protection during the ensuing tests.

This link is not provided on the MMLG 02 because the contacts between terminals 13 and 14 are normally closed.
Note: These two terminals on MMLG 01/02 must not be used for CT connections since this will create a safety hazard. The reason for this is that the associated MMLB 01 test plug contact finger is shorter than the others. This would result in an open circuit path on the MMLG 02. Removal of the cover also reveals an orange coloured strip on the block front plate which gives a clear visual indication that the scheme is out of service.

Connections to other equipment (e.g. CTs, VTs and DC supplies) should be made to odd numbered terminals on the test block. This ensures that when the test plug MMLB is used, the sockets in the white half of the plug are the isolated relay circuits while the sockets in the orange half are connected to the potentially live supplies.

MMLB 01 test plug:

The test plug carries 28 x 4mm sockets. Each socket is identified by a number which corresponds to the numbered case terminal to which the socket is connected when the plug is inserted.

The test plug inserts securely into test sockets of the MMLG test block and can be retained by two knurled screws. Each of the 28 test sockets of the MMLB test plug accepts a test cable with 4mm retractable shrouded plugs.

Accessories provided with each MMLB 01 test plug:
6 shorting plug links, each comprising of two 4 mm stackable plugs with retractable shrouds joined by 150 mm cable.

Download the brochure here:

Download Tech Data sheet here:

Download the brochure here:

Download Tech Data sheet here:

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