Three-Phase Non-Directional Long Time Overcurrent Protection 51Lt158; Identification; Function Block; Functionality - ABB RELION 620 Series Technical Manual

Section 4
Protection functions
4.1.2
4.1.2.1
4.1.2.2
4.1.2.3
4.1.2.4
158
Three-phase non-directional long time overcurrent protection
51LT

Identification

Function description
Three-phase non-directional long time
overcurrent protection

Function block

GUID-64BF56CE-B585-46A5-AD6D-5DE762D107A9 V1 EN
Figure 67: Function block

Functionality

The three-phase long-time overcurrent protection 51LT is used as one-phase, two-phase
or three-phase non-directional overcurrent and short-circuit protection for feeders.
The operation of this function is very similar to the 51P function except that inverse curves
operating times are 10 times that of 51P.
The function also contains a blocking functionality. It is possible to block function
outputs, timers or the function itself, if desired.

Operation principle

The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are "Enable" and "Disable".
The operation of three-phase long-time overcurrent protection can be described by using
a module diagram. All the modules in the diagram are explained in the next sections.
IEC 61850 IEC 60617
identification identification
PHLTPTOC 3I>
1MAC504801-IB E
ANSI/IEEE C37.2
device number
51LT
620 series ANSI
Technical Manual