ABB RELION 620 Series Technical Manual page 380

Section 4
Protection functions
374
"Measured Io" and "Measured Uo" are selected. The nominal values for residual
current and residual voltage are obtained from CT and VT ratios entered in Residual
current Io: Configuration/Analog inputs/Current (Io,CT): 100 A : 1 A. The
Residual voltage Uo: Configuration/Analog inputs/Voltage (Uo,VT): 11.547 kV :
100 V. The Start value of 1.0 × In corresponds to 1.0 * 100 A = 100 A in the primary.
The Voltage start value of 1.0 × Un corresponds to 1.0 * 11.547 kV = 11.547 kV in the
primary.
Example 2: Both Io and Uo are calculated from the phase quantities. Phase CT-ratio
is 100 : 1 A and phase VT-ratio is 20/sqrt(3) kV : 100/sqrt(3) V. In this case,
"Calculated Io" and "Calculated Uo" are selected. The nominal values for residual
current and residual voltage are obtained from CT and VT ratios entered in Residual
current Io: Configuration/Analog inputs/Current (3I,CT): 100 A : 1 A. The
residual voltage Uo: Configuration/Analog inputs/Voltage (3U,VT): 20.000 kV :
100 V. The Start value of 1.0 × In corresponds to 1.0 * 100 A = 100 A in the primary.
The Voltage start value of 1.0 × Un corresponds to 1.0 * 20.000 kV = 20.000 kV in the
primary.
If "Calculated Uo" is selected, the residual voltage nominal value is
always phase-to-phase voltage. Thus, the valid maximum setting for
residual Voltage start value is 0.577 x Un. The calculated Uo requires
that all the three phase-to-earth voltages are connected to the
protection relay. Uo cannot be calculated from the phase-to-phase
voltages.
If the Enable voltage limit setting is set to "True", the magnitude of the
polarizing quantity is checked even if the Directional mode was set to
"Non-directional" or Allow Non Dir to "True". The protection relay
does not accept the Start value or Start value Mult setting if the
product of these settings exceeds the Start value setting range.
Typically, the ENA_MULT input is connected to the inrush detection function
INRHPAR. In case of inrush, INRPHAR activates the ENA_MULT input, which
multiplies Start value by the Start value Mult setting.
Directional calculation
The directional calculation module monitors the angle between the polarizing
quantity and operating quantity. Depending on the Pol quantity setting, the polarizing
quantity can be the residual voltage (measured or calculated) or the negative sequence
voltage. When the angle is in the operation sector, the module sends the enabling
signal to the timer module.
The minimum signal level which allows the directional operation can be set with the
Min operate current and Min operate voltage settings.
If Pol quantity is set to "Zero. seq. volt", the residual current and residual voltage are
used for directional calculation.
1MRS757644 F
620 series
Technical Manual