Stabilized And Instantaneous Differential Protection For Machines Mpdif - ABB RELION 620 Series Technical Manual

Protection and control

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Protection functions

Stabilized and instantaneous differential protection for

machines MPDIF

Identification

Function description

Stabilized and instantaneous differ-

ential protection for machines

Function block

Figure 256: Function block

Functionality

The stabilized and instantaneous differential protection for machines function

MPDIF is a unit protection function. The possibility of internal failures of the

machine is relatively low. However, the consequences in terms of cost and

production loss are often serious, which makes the differential protection an

important protection function.

The stability of the differential protection is enhanced by a DC restraint feature.

This feature decreases the sensitivity of the differential protection optionally for

a temporary time period to avoid an unnecessary disconnection of the machine

during the external faults that have a fault current with high DC currents. MPDIF

also includes a CT saturation-based blocking which prevents unnecessary tripping

in case of the detection of the magnetizing inrush currents which can be present at

the switching operations, overvoltages or external faults.

Operation principle

The function can be enabled and disabled with the

corresponding parameter values are "On" and "Off".

The operation of MPDIF can be described using a module diagram. All the modules

in the diagram are explained in the next sections.

identification

Operation setting. The

1MRS757644 H

ANSI/IEEE C37.2

device number

Technical Manual