intended for use in applications where the zero sequence voltage can be too small to be
used as the polarizing quantity, and there is no zero sequence polarizing current
(transformer neutral current) available. The zero sequence voltage is “boosted” by a
portion of the measured line zero sequence current to form the polarizing quantity. This
method requires that a significant difference must exist in the magnitudes of the zero
sequence currents for close-up forward and reverse faults, that is, it is a requirement that |
V0| >> |k · I0| for reverse faults, otherwise there is a risk that reverse faults can be seen as
forward.
AngleRCA
0 0
V k I e- + × ×
EQUATION1638-ANSI V2 EN (Equation 223)
The negative-sequence voltage polarization with negative-sequence current
compensation (-U2Comp) compares correspondingly I
2
with (see equation 224), and
similarly it must be ensured that |V
2
| >> |k · I
2
| for reverse faults.
AngleRCA
2 2
V k I e- + × ×
EQUATION1639-ANSI V2 EN (Equation 224)
8.7 Mho impedance supervision logic ZSMGAPC
8.7.1 Identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Mho Impedance supervision logic ZSMGAPC - -
8.7.2 Application
The Mho impedance supervision logic (ZSMGAPC) includes features for fault inception
detection and high SIR detection. It also includes the functionality for loss of potential
logic as well as for the pilot channel blocking scheme.
One part of ZSMGAPC function identifies a loss of phase potential that is the result of a
long term (steady state) condition such as a blown fuse or an open voltage transformer
winding or connection. This will block all trips by the distance protection since they are
based on voltage measurement.
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 303
Application manual
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