Operation Principle - ABB RELION Series Technical Manual

Section 4
Protection functions
4.2.4.4
326

Operation principle

The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of EFPADM can be described using a module diagram. All the modules
in the diagram are explained in the next sections.
Io
Neutral
admittance
calculation
Uo
RELEASE
BLOCK
GUID-BAD34871-A440-433D-8101-022E1E245A0D V1 EN
Figure 166: Functional module diagram
Neutral admittance calculation
The residual current can be selected from the Io signal Sel setting. The setting 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 phase-current channels
given in Configuration/Analog inputs/Current (3I,CT).
Respectively, the residual voltage can be selected from the Uo signal Sel setting. The
setting 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 phase-
voltage channels given in Configuration/Analog inputs/Voltage (3U,VT).
Example 1: Uo is measured from open-delta connected VTs (20/sqrt(3) kV : 100/
sqrt(3) V:100/3 V). In this case, "Measured Uo" is selected. The nominal values for
residual voltage is obtained from the VT ratios entered in Residual voltage Uo :
Configuration/Analog inputs/Voltage (Uo,VT): 11.547 kV : 100 V. The residual
voltage start value of 1.0 × Un corresponds to 1.0 × 11.547 kV = 11.547 kV in the
primary.
Example 2: Uo is calculated from phase quantities. The phase VT-ratio is 20/sqrt(3)
kV : 100/sqrt(3) V. In this case, "Calculated Uo" is selected. The nominal value for
residual voltage is obtained from the VT ratios entered in Residual voltage Uo :
Configuration/Analog inputs/Voltage (3U,VT) : 20.000kV : 100V. The residual
voltage start value of 1.0 × Un corresponds to 1.0 × 20.000 kV = 20.000 kV in the
primary.
In case, 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 × Un. The calculated
Timer
Operation
t
characteristics
Blocking
logic
1MRS758755 A
OPERATE
START
REC615 and RER615
Technical Manual