ABB RELION Series Technical Manual page 286

Section 4
Protection functions
280
The operation of (F)DEFxPDEF can be described using a module diagram. All the
modules in the diagram are explained in the next sections.
A070438 V3 EN
Figure 142: Functional module diagram
Level detector
The magnitude of the operating quantity is compared to the set Start value and the
magnitude of the polarizing quantity is compared to the set Voltage start value. If both
the limits are exceeded, the level detector sends an enabling signal to the timer
module. When the Enable voltage limit setting is set to "False", Voltage start value has
no effect and the level detection is purely based on the operating quantity. If the
ENA_MULT input is active, the Start value setting is multiplied by the Start value Mult
setting.
The operating quantity (residual current) can be selected with the setting Io signal
Sel. The options are "Measured Io" and "Calculated Io". If "Measured Io" is selected,
the current ratio for Io-channel is given in Configuration/Analog inputs/Current
(Io,CT). If "Calculated Io" is selected, the current ratio is obtained from the phase-
current channels given in Configuration/Analog inputs/Current (3I,CT).
The operating quantity (residual voltage) can be selected with the setting Uo signal
Sel. The options are "Measured Uo" and "Calculated Uo". If "Measured Uo" is
selected, the voltage ratio for Uo-channel is given in Configuration/Analog inputs/
Voltage (Uo,VT). If "Calculated Uo" is selected, the voltage ratio is obtained from the
phase-voltage channels given in Configuration/Analog inputs/Voltage (3U,VT).
Example 1: Io is measured with cable core CT (100/1 A) and Uo is measured from
open-delta connected VTs (20/sqrt(3) kV : 100/sqrt(3) V : 100/3 V). In this case,
"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.
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