Motor And Generator Protection - Siemens 7UT51 Instruction Manual

3
Application Examples
If the reactors are part of a three-phase, oil immersed
type bank, CTs may be provided at each end of the
winding and in the grounded neutral, as shown in
Figure 3.6. If so, the differential elements (87, 87HS,
87N) can provide primary protection, while backup
protection is provided by one of the thermal overload
elements (49), the internal overcurrent elements (not
shown), or external overcurrent elements (as shown in
Figure 3.6).
7SJ600
50
3
52
3
1
Figure 3.6 Reactor Protection for Three
Immersed Type Reactor Bank
3.3 Motor and Generator
Protection
A 7UT51 relay can protect a single motor or generator
as shown in Figure 3.7), or a system comprised of a
generator and main power transformer connected as a
unit (as shown in Figure 3.8). The protection afforded
in the single machine scheme is straightforward and
consists only of primary (87) protection. For smaller,
simpler generators (without elaborate cooling
systems) and for most motors, one or both of the
thermal overload elements could be employed in the
protection scheme. In addition, the backup overcurrent
elements could be configured but would be set to
protect the machine from fault contributions from the
system rather than to protect the system from fault
34
51
7U T 513
W 1
49
W 1
W 2
87
8 7
H S
N
87N
-
Phase, Oil
contributions from the machine. This is due primarily
to the short duration of (induction) motor contributions
to faults and to the dynamics which characterize fault
contributions from a generator to external faults
(X" X' X trajectory).
d d s
52
3
G /M
3
Figure 3.7 Generator or Motor Protection
For the unit-connected generator-transformer system
shown in Figure 3.8, a 7UT513 model is required. The
protection in this scheme is essentially identical to that
shown in Figure 3.2. Primary protection (87, 87HS) is
provided for the generator and transformer along with
the section of buswork connecting to the unit auxiliary
transformer breaker. Thermal overload protection is
provided for the main power transformer wye winding
(49-1), and thermal overload (49-2) and backup
overcurrent protection (50,51) are provided for the unit
auxiliary transformer. As with the other 7UT513
applications, the independently configurable trip
contacts provide flexible tripping schemes.
7UT51 v3
o th er
7U T 512
W 1
W 2
87
o th er
PRIM-2330C