Operation Principle - ABB 615 series Technical Manual

1MAC059074-MB A
4.2.7.4
615 series ANSI
Technical Manual
• Differential of the third harmonic component measured both at generator neutral and
terminal side
• Neutral side third harmonic undervoltage
27/59THN operates with the definite time DT characteristics.
The function contains a blocking functionality. Blocking deactivates all outputs and reset
timers.

Operation principle

The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are "Enable" and "Disable".
The operation of 27/59THN can be described using a module diagram. All the modules in
the diagram are explained in the next sections.
V_3H_A
rd
3
V_3H_B
harmonic
V_3H_C
calculation
V_3H_RES
V_3H_N
GCB_CLOSED
BLOCK
GUID-705CF2E6-CD84-4DA4-8370-5B894BFD1789 V1 EN
Figure 205: Functional module diagram
3rd harmonic calculation (terminal side)
3rd harmonic calculation calculates the magnitude and phase angle of the third harmonic
voltage at the generator terminal
depends on the availability of terminal side voltage and is specified by the Voltage
selection setting.
• Voltage selection setting is set to "No voltage" if phase-to-ground voltages are not
available at the terminal side. Even in a situation where only phase-to-phase voltages
are available, Voltage selection is set to "No Voltage" because phase-to-phase
voltages do not contain a third harmonic component. With Voltage selection set to
"No Voltage", third harmonic-based ground-fault protection is based on third
harmonic neutral side undervoltage protection.
• Voltage selection setting is set to "Measured VG" if the terminal side voltage is fed
from an open delta voltage connection of the voltage transformer. In this case, the
terminal side third harmonic voltage
Differential Level
calculation detector
Bias
calculation
. Calculation of the third harmonic voltage
V
3H T _
is same as the measured open delta
V
3H T _
Section 4
Protection functions
Timer
TRIP
t
PICKUP
INT_BLKD
425