Phase angle characteristic
The operation criterion phase angle is selected with the Operation mode setting using the value "Phase angle".
When the phase angle criterion is used, the DIRECTION monitored data indicates on which operating sector the operating quantity is measured. The FAULT_DIR monitored data indicates in which operation sector the fault current is measured. The monitored data is operational once the function is started.
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 clockwise sector and the Min forward angle setting correspondingly the counterclockwise sector, measured from the Characteristic angle setting.
In the reverse operation area, the Max reverse angle setting gives the clockwise sector and the Min reverse angle setting correspondingly the counterclockwise sector, measured from the complement of the Characteristic angle setting (180 degrees phase shift) .
The relay characteristic angle (RCA) is set to positive if the operating current lags the polarizing quantity. It is set to negative if it leads the polarizing quantity.
| Fault direction | The value for DIRECTION |
|---|---|
| Angle between the polarizing and operating quantity is not in any of the defined sectors. | 0 = unknown |
| Angle between the polarizing and operating quantity is in the forward sector. | 1= forward |
| Angle between the polarizing and operating quantity is in the reverse sector. | 2 = backward |
| Angle between the polarizing and operating quantity is in both the forward and the reverse sectors, that is, the sectors are overlapping. | 3 = both |
If the Allow Non Dir setting is "False", the directional operation (forward, reverse) is not allowed when the measured polarizing or operating quantities are invalid, that is, their magnitude is below the set minimum values. The minimum values can be defined with the settings Min operate current and Min operate voltage. In case of low magnitudes, the FAULT_DIR and DIRECTION monitored data are set to 0 = unknown, except when the Allow Non Dir setting is "True". In that case, the function is allowed to operate in the directional mode as non-directional, since the directional information is invalid.
Iosin(φ) and Iocos(φ) criteria
A more modern approach to directional protection is the active or reactive current measurement. The operating characteristic of the directional operation depends on the earthing principle of the network. The Iosin(φ) characteristics is used in an isolated network, measuring the reactive component of the fault current caused by the earth capacitance. The Iocos(φ) characteristics is used in a compensated network, measuring the active component of the fault current.
The operation criteria Iosin(φ) and Iocos(φ) are selected with the Operation mode setting using the values "IoSin" or "IoCos" respectively.
The angle correction setting can be used to improve selectivity. The setting decreases the operation sector. The correction can only be used with the Iosin(φ) or Iocos(φ) criterion. The RCA_CTL input is used to change the Io characteristic:
| Operation mode: | RCA_CTL = "False" | RCA_CTL = "True" |
|---|---|---|
| IoSin | Actual operation criterion: Iosin(φ) | Actual operation criterion: Iocos(φ) |
| IoCos | Actual operation criterion: Iocos(φ) | Actual operation criterion: Iosin(φ) |
When the Iosin(φ) or Iocos(φ) criterion is used, the component indicates a forward- or reverse-type fault through the FAULT_DIR and DIRECTION monitored data, in which 1 equals a forward fault and 2 equals a reverse fault. Directional operation is not allowed (the Allow Non Dir setting is "False") when the measured polarizing or operating quantities are not valid, that is, when their magnitude is below the set minimum values. The minimum values can be defined with the Min operate current and Min operate voltage settings. In case of low magnitude, the FAULT_DIR and DIRECTION monitored data are set to 0 = unknown, except when the Allow Non Dir setting is "True". In that case, the function is allowed to operate in the directional mode as non-directional, since the directional information is invalid.
The calculated Iosin(φ) or Iocos(φ) current used in direction determination can be read through the I_OPER monitored data. The value can be passed directly to a decisive element, which provides the final start and operate signals.
The I_OPER monitored data gives an absolute value of the calculated current.
The following examples show the characteristics of the different operation criteria:
Example 1.
Iosin(φ) criterion selected, forward-type fault
=> FAULT_DIR = 1
The operating sector is limited by angle correction, that is, the operating sector is 180 degrees - 2*(angle correction).
Example 2.
Iosin(φ) criterion selected, reverse-type fault
=> FAULT_DIR = 2
Example 3.
Iocos(φ) criterion selected, forward-type fault
=> FAULT_DIR = 1
Example 4.
Iocos(φ) criterion selected, reverse-type fault
=> FAULT_DIR = 2
Phase angle 80
The operation criterion phase angle 80 is selected with the Operation mode setting by using the value "Phase angle 80".
- The Max forward angle and Max reverse angle settings cannot be set but they have a fixed value of 80 degrees
- The sector limits of the fixed sectors are rounded.
Phase angle 88
The operation criterion phase angle 88 is selected with the Operation mode setting using the value "Phase angle 88".
- The Max forward angle and Max reverse angle settings cannot be set but they have a fixed value of 88 degrees
- The sector limits of the fixed sectors are rounded.
- If the current amplitude is between 1...20 percent of the nominal current, the sector limit increases linearly from 73 degrees to 85 degrees
- If the current amplitude is between 20...100 percent of the nominal current, the sector limit increases linearly from 85 degrees to 88 degrees
- If the current amplitude is more than 100 percent of the nominal current, the sector limit is 88 degrees.
