• Low (EFLPTOC)
• High (EFHPTOC)
• Instantaneous (EFIPTOC).
EFLPTOC contains several types of time-delay characteristics. EFHPTOC and
EFIPTOC are used for fast clearance of serious earth faults.
5.2.2 Directional earth-fault protection DEFxPDEF
5.2.2.1 Identification
Table 62: Function identification
Different stages: Low stage High stage
IEC 61850 identification: DEFLPDEF DEFHPDEF
IEC 60617 identification: I
0
>-> I
0
>>->
ANSI/IEEE C37.2 device number: 67N-1 67N-2
5.2.2.2 Functionality
The earth-fault function DEFxPDEF is used as directional earth-fault protection for
feeders.
The function starts and operates when the residual current and residual voltage (-
U
0
) exceed the set limits and the angle between them is inside the set operating sector.
The operate time characteristic for low stage (DEFLPDEF) and high stage
(DEFHPDEF) can be selected to be either definite time (DT) or inverse definite
minimum time (IDMT).
In the DT mode, the function operates after a predefined operate time and resets when
the fault current disappears. The IDMT mode provides current-dependent timer
characteristics.
The function contains a blocking functionality. It is possible to block function outputs,
timers or the function itself, if desired.
5.2.2.3 Directional earth-fault principles
In many cases it is difficult to achieve selective earth-fault protection based on the
magnitude of residual current only. To obtain a selective earth-fault protection
scheme, it is necessary to take the phase angle of I
0
into account. This is done by
comparing the phase angle of I
0
to that of the residual voltage (-U
0
).
Relay characteristic angle
The Characteristic angle, also known as Relay Characteristic Angle (RCA), Relay
Base Angle or Maximum Torque Angle (MTA), is used in the "Phase angle" mode
Section 5 1MRS756378 D
Protection functions
146 REF615
Application Manual
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