Under Impedance Protection For Generators And Transformers Zgvpdis - ABB RELION RET670 Applications Manual

1MRK 504 163-UUS A
8.21
8.21.1
8.21.2
Transformer protection RET670 2.2 ANSI
Application manual
Under impedance protection for generators and
transformers ZGVPDIS
Identification
Function description
Under impedance function for
generators and transformers
Application
Under impedance protection for generator is generally used as back up protection for
faults on generator, transformer and transmission lines. Zone 1 can be used to provide
high speed protection for phase faults in the generator, bus ducts or cables and part of
the generator transformer. Zone 2 can be used to cover generator transformer and
power plant's substation bus-bar. Zone 3 can be used to cover power system faults.
The under impedance protection is provided with undervoltage detection feature in
order to provide the seal-in for the impedance based trip. Additionally, it is provided
with load encroachment feature in order to avoid tripping of the protection during
heavy load conditions. The load encroachment functionality is based on the positive
sequence components of voltage and current.
Characteristics of backup impedance protection
Characteristics of zone 1, zone 2 and zone 3 are shown in figure 253. All zones have
offset mho characteristics with adjustable reach in forward and reverse direction. The
characteristic angle for all three zones is common and adjustable. A load encroachment
blinder feature is provided for zone 2 and zone 3.
Protection designed to operate for below types of faults
Faults in the generator, generator terminal connections to the step-up transformer and
in the low voltage (LV) side of the generator step-up transformer are:
Impedance protection
IEC 61850 IEC 60617
identification identification
ZGVPDIS
S00346 V1 EN-US
Section 8
GUID-1A3A4890-5CFA-417B-BDA4-EA001502AA60 v2
GUID-752C21F4-972E-4E97-AB15-075FF720527F v2
ANSI/
IEEEidentification
21G
GUID-ACC76B44-C071-4034-AB9D-880A77E12E66 v2
501