The function can be blocked in the following ways:
•
activating of input
BLOCK
blocks the whole function
•
activating of the input
BLKZ
(fuse failure) blocks all output signals
•
activating of the input
BLKZMTD
blocks the delta based time domain algorithm
•
activating of the input
BLKHSIR
blocks the instantaneous part of the algorithm
for high SIR values
•
activating of the input
BLKTRIP
blocks all output signals
•
activating the input
BLKPE
blocks the phase-to-earth fault loop outputs
•
activating the input
BLKPP
blocks the phase-to-phase fault loop outputs
The activation of input signal
BLKZ
can be made by external fuse failure function or
from the loss of voltage check in the Mho supervision logic (ZSMGAPC). In both
cases the output
BLKZ
in the Mho supervision logic shall be connected to the input
BLKZ
in the Mho distance function block (ZMHPDIS)
The input signal
BLKZMTD
is activated during some ms after fault has been detected
by ZSMGAPC to avoid unwanted operations due to transients. It shall be connected
to the
BLKZMTD
output signal of ZSMGAPC function.
At SIR values >10, the use of electronic CVT might cause overreach due to the built-
in resonance circuit in the CVT, which reduce the secondary voltage for a while. The
input
BLKHSIR
is connected to the output signal
HSIR
on ZSMGAPC for increasing
of the filtering and high SIR values. This is valid only when permissive underreach
scheme is selected by setting
ReachMode
=Underreach.
7.1.6.4
Theory of operation
The mho algorithm is based on the phase comparison of an operating phasor and a
polarizing phasor. When the operating phasor leads the reference polarizing phasor by
90 degrees or more, the function operates and gives a trip output.
Phase-to-phase fault
Mho
The plain Mho circle has the characteristic as in Figure
. The condition for deriving
the angle β is according to equation
.
EQUATION1789 V2 EN
(Equation 37)
Section 7
1MRK502052-UEN B
Impedance protection
184
Technical manual
Summary of Contents for Relion REG670
Page 1: ...Relion 670 series Generator protection REG670 2 0 IEC Technical manual ...
Page 2: ......
Page 44: ...38 ...
Page 58: ...52 ...
Page 80: ...74 ...
Page 106: ...100 ...
Page 482: ...476 ...
Page 548: ...542 ...
Page 570: ...564 ...
Page 600: ...594 ...
Page 608: ...602 ...
Page 630: ...624 ...
Page 862: ...856 ...
Page 1094: ...1088 ...
Page 1226: ...1220 ...
Page 1250: ...1244 ...
Page 1297: ...1291 ...