ABB 615 series Technical Manual page 379

1MAC059074-MB A
615 series ANSI
Technical Manual
To ensure a sufficient accuracy for the IG and VG measurements, it is required that the
residual voltage exceeds the value set by Min trip voltage. If the admittance calculation
mode is "Delta", the minimum change in the residual voltage due to a fault must be 0.01
× Vn to enable the operation. Similarly, the residual current must exceed the value set by
Min trip current.
The polarity of the polarizing quantity VG can be changed, that is, rotated
by 180 degrees, by setting the Pol reversal parameter to "True" or by
switching the polarity of the residual voltage measurement wires.
As an alternative for the internal residual overvoltage-based pickup condition, the neutral
admittance protection can also be externally released by utilizing the RELEASE input.
When Admittance Clc mode is set to "Delta", the external logic used must be able to give
RELEASE in less than 0.1 s from fault initiation. Otherwise the collected pre-fault values
are overwritten with fault time values. If it is slower, Admittance Clc mode must be set to
"Normal".
Neutral admittance is calculated as the quotient between the residual current and residual
voltage (polarity reversed) fundamental frequency phasors. The Admittance Clc mode
setting defines the calculation mode.
Admittance Clc mode = "Normal"
IG
fault
Yo
=
VG
−
fault
GUID-A831002F-5145-4700-8D9A-C80FBF6757AF V1 EN
Admittance Clc mode = "Delta"
IG IG
−
fault prefault
Yo
=
( VG VG )
− −
fault prefault
GUID-3AD86A5A-52E7-421E-96CC-C69838CB026C V1 EN
Yo Calculated neutral admittance [Siemens]
IG Residual current during the fault [Amperes]
fault
VG Residual voltage during the fault [Volts]
fault
IG Prefault residual current [Amperes]
prefault
VG Prefault residual voltage [Volts]
prefault
ΔIG Change in the residual current due to fault [Amperes]
ΔVG Change in the residual voltage due to fault [Volts]
IG
∆
=
VG
− ∆
Section 4
Protection functions
(Equation 24)
(Equation 25)
373