Low Impedance Restricted Earth Fault Protection Refpdif (87N); Identification; Functionality - ABB RELION 670 Series Technical Manual

Section 6
Differential protection
Function
Impulse margin time unrestrained
function
Trip time at 0 to 5 x IMinNegSeq
Negative sequence unrestrained
function
Reset time at 5 x IMinNegSeq to 0
Negative sequence unrestrained
function
6.4 Low impedance restricted earth fault protection REFPDIF
(87N)
6.4.1

Identification

Function description
Restricted earth-fault protection,
low impedance
6.4.2

Functionality

Restricted fault protection, low-impedance function REFPDIF (87N) can be used on all solidly or
low-impedance grounded windings. The REFPDIF (87N) function provides high sensitivity and high
speed tripping as it protects each winding separately and thus does not need inrush stabilization.
The REFPDIF function is a percentage biased function with an additional zero sequence current
directional comparison criterion. This gives excellent sensitivity and stability during through
faults.
REFPDIF can also protect autotransformers. Five currents are measured at the most complicated
configuration as shown in Figure 62.
166
Range or value
10 ms typically
Min. = 25 ms
Max. = 35 ms
Min. = 30 ms
Max. = 45 ms
IEC 61850 IEC 60617
identification identification
REFPDIF
IdN/I
SYMBOL-AA V1 EN-US
1MRK 502 066-UUS B
Accuracy
-
-
-
ANSI/IEEE C37.2
device number
87N
Technical manual
IP14640-1 v6
M14843-1 v5
IP12418-1 v2
M13047-3 v18