Functionality - ABB 615 series Technical Manual

Section 4
Protection functions
4.5.3.3
4.5.3.4
628

Functionality

The residual overvoltage protection function 59N, 59G is used in distribution networks
where the residual overvoltage can reach non-acceptable levels in, for example, high
impedance grounding.
The function picks up when the residual voltage exceeds the set limit. 59N, 59G operates
with the definite time (DT) characteristic.
The function contains a blocking functionality. It is possible to block function outputs, the
definite timer or the function itself, if desired.
Operation principle
The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are "Enable" and "Disable".
The operation of 59N, 59G can be described by using a module diagram. All the modules
in the diagram are explained in the next sections.
GUID-852F56DB-266E-4CB8-BC58-01D4BA605FD0-ANSI V1 EN
Figure 314: Functional module diagram
Level detector
The residual voltage is compared to the set Pickup value. If the value exceeds the set
Pickup value, the level detector sends an enable signal to the timer. The residual voltage
can be selected with the VG/V0 Select setting. The options are "Measured VG" and
"Calculated V0". If "Measured VG" is selected, the voltage ratio for VG-channel is given
in the global setting Configuration/Analog inputs/Voltage (VG,VT). If "Calculated
V0" is selected, the voltage ratio is obtained from phase-voltage channels given in the
global setting Configuration/Analog inputs/Voltage (3V,VT).
Example 1: VG is measured from the open-delta connected VTs (20/sqrt(3) kV : 100/
sqrt(3) V : 100/3 V). In this case, "Measured VG" is selected. The nominal values for
residual voltage is obtained from the VT ratios entered in Residual voltage VG:
Configuration/Analog inputs/Voltage (VG,VT): 11.547 kV:100 V. The residual
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615 series ANSI
Technical Manual