The forward and reverse sectors are defined separately. The forward operation area is limited with the Min forward angle and Max forward angle settings. The reverse operation area is limited with the Min reverse angle and Max reverse angle settings.
In the forward operation area, the Max forward angle setting gives the counterclockwise sector and the Min forward angle setting gives the corresponding clockwise sector, measured from the Characteristic angle setting.
In the backward operation area, the Max reverse angle setting gives the counterclockwise sector and the Min reverse angle setting gives the corresponding clockwise sector, a measurement from the Characteristic angle setting that has been rotated 180 degrees.
Relay characteristic angle (RCA) is set positive if the operating current lags the polarizing quantity and negative if the operating current leads the polarizing quantity.
| Criterion for per phase direction information | The value for DIR_A/_B/_C |
|---|---|
| The ANGLE_X is not in any of the defined sectors, or the direction cannot be defined due too low amplitude | 0 = unknown |
| The ANGLE_X is in the forward sector | 1 = forward |
| The ANGLE_X is in the reverse sector | 2 = backward |
| (The ANGLE_X is in both forward and reverse sectors, that is, when the sectors are overlapping) | -1 = both |
| Criterion for phase combined direction information | The value for DIRECTION |
|---|---|
| The direction information (DIR_X) for all phases is unknown | 0 = unknown |
| The direction information (DIR_X) for at least one phase is forward, none being in reverse | 1 = forward |
| The direction information (DIR_X) for at least one phase is reverse, none being in forward | 2 = backward |
| The direction information (DIR_X) for some phase is forward and for some phase is reverse | 3 = both |
Self-polarizing as polarizing method
| Faulted phases | Used fault current | Used polarizing voltage | Angle difference |
|---|---|---|---|
| A |
I A |
U A |
|
| B |
I B |
U B |
|
| C |
I C |
U C |
|
| A - B | I A-IB |
U AB |
|
| B - C | I B-IC |
U BC |
|
| C - A | I C-IA |
U CA |
|
In an example case of the phasors in a single-phase earth fault where the faulted phase is phase A, the angle difference between the polarizing quantity U A and operating quantity I A is marked as φ. In the self-polarization method, there is no need to rotate the polarizing quantity.
In an example case of a two-phase short-circuit failure where the fault is between phases B and C, the angle difference is measured between the polarizing quantity U BC and operating quantity IB - IC in the self-polarizing method.
Cross-polarizing as polarizing quantity
| Faulted phases | Used fault current | Used polarizing voltage | Angle difference |
|---|---|---|---|
| A | I A | U BC |
|
| B | I B | U CA |
|
| C | I C | U AB |
|
| A - B | I A-IB | U BC-UCA |
|
| B - C | I B-IC | U CA-UAB |
|
| C - A | I C-IA | U AB-UBC |
|
The angle difference between the polarizing quantity U BC and operating quantity I A is marked as φ in an example of the phasors in a single-phase earth fault where the faulted phase is phase A. The polarizing quantity is rotated with 90 degrees. The characteristic angle is assumed to be ~ 0 degrees.
In an example of the phasors in a two-phase short-circuit failure where the fault is between the phases B and C, the angle difference is measured between the polarizing quantity UAB and operating quantity IB - IC marked as φ.
Negative sequence voltage as polarizing quantity
When the negative voltage is used as the polarizing quantity, the angle difference between the operating and polarizing quantity is calculated with the same formula for all fault types:
This means that the actuating polarizing quantity is - U2.
Positive sequence voltage as polarizing quantity
| Faulted phases | Used fault current | Used polarizing voltage | Angle difference |
|---|---|---|---|
| A | I A | U 1 |
|
| B | I B | U 1 |
|
| C | I C | U 1 |
|
| A - B | I A-IB | U 1 |
|
| B - C | I B-IC | U 1 |
|
| C - A | I C-IA | U 1 |
|
Network rotation direction
Typically, the network rotating direction is counter-clockwise and defined as "ABC". If the network rotating direction is reversed, meaning clockwise, that is, "ACB", the equations for calculating the angle difference needs to be changed. The network rotating direction is defined with a system parameter Phase rotation. The change in the network rotating direction affects the phase-to-phase voltages polarization method where the calculated angle difference needs to be rotated 180 degrees. Also, when the sequence components are used, which are, the positive sequence voltage or negative sequence voltage components, the calculation of the components are affected but the angle difference calculation remains the same. When the phase-to-ground voltages are used as the polarizing method, the network rotating direction change has no effect on the direction calculation.