Low Impedance Restricted Earth Fault Protection Refpdif; Identification; Application - ABB RELION 670 Series Applications Manual

1MRK 504 152-UEN B
IEC05000749 V1 EN-US
Figure 48: Current voltage characteristics for the non-linear resistors, in the range 10-200 V, the
average range of current is: 0.01–10 mA
6.3 Low impedance restricted earth fault protection
REFPDIF
6.3.1

Identification

Function description
Restricted earth-fault protection,
low impedance
6.3.2

Application

A breakdown of the insulation between a transformer winding and the core or the tank may
result in a large fault current which causes severe damage to the windings and the transformer
core. A high gas pressure may develop, damaging the transformer tank.
Fast and sensitive detection of earth faults in a power transformer winding can be obtained in
solidly earthed or low impedance earthed networks by the restricted earth-fault protection.
The only requirement is that the power transformer winding is connected to earth in the star
point (in case of star-connected windings) or through a separate earthing transformer (in case
of delta-connected windings).
The low impedance restricted earth-fault protection REFPDIF is a winding protection function.
It protects the power transformer winding against faults involving earth. Observe that single
phase-to-earth faults are the most common fault types in transformers. A sensitive earth-fault
protection is therefore desirable.
Application manual
IEC 61850 IEC 60617
identification identification
REFPDIF
IdN/I
SYMBOL-AA V1 EN-US
Section 6
Differential protection
ANSI/IEEE C37.2
device number
87N
IP14640-1 v6
M14843-1 v5
IP14941-1 v1
M13940-3 v11
135