Overview
The “Low impedance restricted earth fault protection” function can be used on all directly or low-impedance earthed windings. The REFPDIF function provides high sensitivity and high speed tripping as it protects each winding separately and thus does not need inrush stabilization. It is a percentage biased function with an additional zero sequence current directional comparison criterion.
For more detailed information on “Low impedance restricted earth fault protection” function, refer to ABB, Relion 670 Series manuals.
To see other supported functions, click here.
Function Identification
| Function description | IEC 61850 identification |
IEC 60617 identification |
ANSI/IEEE C37.2 device number |
| Restricted earth fault protection, low impedance | REFPDIF | IdN/I | 87N |
Signals & Setting Parameters
REFPDIF function block
REFPDIF Input signals
| REFPDIF Input signals | |||
| Name | Type | Default | Description |
| I3P | GROUP SIGNAL | – | Group signal for neutral current input |
| I3PW1CT1 | GROUP SIGNAL | – | Group signal for primary CT1 current input |
| I3PW1CT2 | GROUP SIGNAL | – | Group signal for primary CT2 current input |
| I3PW2CT1 | GROUP SIGNAL | – | Group signal for secondary CT1 current input |
| I3PW2CT2 | GROUP SIGNAL | – | Group signal for secondary CT2 current input |
| BLOCK | BOOLEAN | 0 | Block of function |
REFPDIF Output signals
| REFPDIF Output signals | |||
| Name | Type | Description | |
| TRIP | BOOLEAN | Trip by restricted earth fault protection function | |
| START | BOOLEAN | Start by restricted earth fault protection function | |
| DIROK | BOOLEAN | Directional Criteria has operated for internal fault | |
| BLK2H | BOOLEAN | Block due to 2-nd harmonic | |
| IRES | REAL | Magnitude of fund. freq. residual current | |
| IN | REAL | Magnitude of fund. freq. neutral current | |
| IBIAS | REAL | Magnitude of the bias current | |
| IDIFF | REAL | Magnitude of fund. freq. differential current | |
| ANGLE | REAL | Direction angle from zerosequence feature | |
| I2RATIO | REAL | Second harmonic ratio | |
REFPDIF Non group settings (basic)
| REFPDIF Non group settings (basic) | |||||
| Name | Values (Range) | Unit | Step | Default | Description |
| GlobalBaseSel | 1 – 12 | – | 1 | 1 | Selection of one of the Global Base Value groups |
REFPDIF Group settings (basic)
| REFPDIF Group settings (basic) | |||||
| Name | Values (Range) | Unit | Step | Default | Description |
| Operation | Off On |
– | – | Off | Operation Off / On |
| IdMin | 4.0 – 100.0 | %IB | 0.1 | 10.0 | Maximum sensitivity in % of IBase |
| CTFactorPri1 | 1.0 – 10.0 | – | 0.1 | 1.0 | CT factor for HV side CT1 (CT1rated/ HVrated current) |
| CTFactorPri2 | 1.0 – 10.0 | – | 0.1 | 1.0 | CT factor for HV side CT2 (CT2rated/ HVrated current) |
| CTFactorSec1 | 1.0 – 10.0 | – | 0.1 | 1.0 | CT factor for MV side CT1 (CT1rated/ MVrated current) |
| CTFactorSec2 | 1.0 – 10.0 | – | 0.1 | 1.0 | CT factor for MV side CT2 (CT2rated/ MVrated current) |
REFPDIF Group settings (advanced)
| REFPDIF Group settings (advanced) | |||||
| Name | Values (Range) | Unit | Step | Default | Description |
| ROA | 60 – 119 | deg | 1 | 60 | Relay operate angle for zero sequence directional feature if protected winding neutral point is grounded via resistor increase ROA to 115 degrees |
REFPDIF Monitored data
| REFPDIF Monitored data | ||||
| Name | Type | Values (Range) | Unit | Description |
| IRES | REAL | – | A | Magnitude of fund. freq. residual current |
| IN | REAL | – | A | Magnitude of fund. freq. neutral current |
| IBIAS | REAL | – | A | Magnitude of the bias current |
| IDIFF | REAL | – | A | Magnitude of fund. freq. differential current |
| ANGLE | REAL | – | deg | Direction angle from zerosequence feature |
| I2RATIO | REAL | – | – | Second harmonic ratio |
Logics & highlights
Examples of applications of the REFPDIF
Zero sequence currents at an external earth fault
Zero sequence currents at an internal earth fault
Representation of Operate-bias characteristics at different IdMin setting values
Calculation of operate bias characteristic
Setting range of IdMin, end zones and slopes
Calculation of differential current and bias current
