Schweitzer Engineering Laboratories SEL-787-2 Manual page 30

30
SEL-787-2E Rear and Side Panels
(A) Rear-Panel Layout
Figure 44 SEL-787-2E With Single Ethernet, EIA-232/EIA-485 Communications, and RTD Option
Applications
The SEL-787 is designed to provide differential and
overcurrent protection for power transformers, generator
step-up transformers, and autotransformers with as many
as four windings/terminals. In addition, the SEL-787
contains advanced integration and control features that
will allow its application in a wide variety of automation
and control schemes. Refer to Section 2: Installation and
Section 4: Protection and Logic Functions of the instruc-
tion manual for more details.
Figure 45 shows the application of an SEL-787-4X
Relay for protection of a three-winding transformer. You
can configure Windings 1, 2, and 4 on the relay for
differential protection, and you can apply the 50/51
elements associated with each winding towards
overcurrent protection. You can configure A-phase and
B-phase of Winding 3 on the relay for REF protection for
Windings 1 and 2, respectively. You can configure
C-phase of Winding 3, along with the RTD thermal
elements, to provide fan bank control and protection. Use
additional RTD thermal elements to monitor LTC tank
SEL-787-2, -3, -4 Data Sheet
(B) Side-Panel Layout
temperatures and SEL
OGIC
temperature differential alarms between transformer and
LTC tank temperatures.
Figure 46 shows an SEL-787-3E Relay protecting an
autotransformer with three terminals. You can configure
Windings 1, 2, and 3 on the relay for differential
protection, and you can apply the 50/51 elements
associated with each winding towards overcurrent
protection. You can configure Channel IN on the relay
for REF protection. You can use the three-phase voltage
inputs for V/Hz, over- and undervoltage, over- and
underfrequency, and directional power protection.
Apply the transformer through-fault monitoring of the
SEL-787 to keep track of accumulated through-fault I
values. Monitor the number of through faults,
2
accumulated I t, and fault duration times to determine
the frequency (through-fault events per day, week,
month, or year) and impact of external faults on the
transformer.
Schweitzer Engineering Laboratories, Inc.
programming to indicate
2
t