ABB Relion 670 series - Page 394

7.12.1 Identification
SEMOD158930-2 v3
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Loss of excitation LEXPDIS
<
SYMBOL-MM V1 EN-US
40
7.12.2 Functionality
SEMOD151269-4 v8
There are limits for the under-excited operation of a synchronous machine. A reduction of the
excitation current weakens the coupling between the rotor and the stator. The machine may lose
the synchronism and start to operate like an induction machine. Then, the reactive power
consumption will increase. Even if the machine does not loose synchronism it may not be
acceptable to operate in this state for a long time. Reduction of excitation increases the
generation of heat in the end region of the synchronous machine. The local heating may damage
the insulation of the stator winding and the iron core.
To prevent damages to the generator it should be tripped when excitation is lost.
7.12.3 Function block
SEMOD172764-4 v2
ANSI0700031-1-en.vsd
LEXPDIS (40)
I3P*
V3P*
BLOCK
BLKTRZ1
BLKTRZ2
TRIP
TRZ1
TRZ2
PICKUP
PU_Z1
PU_Z2
XOHM
XPERCENT
ROHM
RPERCENT
ANSI0700031 V1 EN-US
Figure 208: LEXPDIS (40) function block
7.12.4 Signals
PID-3665-INPUTSIGNALS v5
Table 171: LEXPDIS (40) Input signals
Name Type Default Description
I3P GROUP
SIGNAL
- Current group connection
V3P GROUP
SIGNAL
- Voltage group connection
BLOCK BOOLEAN 0 Block of function
BLKTRZ1 BOOLEAN 0 Block trip of zone Z1
BLKTRZ2 BOOLEAN 0 Block trip of zone Z2
Section 7 1MRK 502 066-UUS B
Impedance protection
388
Technical manual