4.42
SEL-700G Relay
Instruction Manual
Date Code 20170814
Protection and Logic Functions
Group Settings (SET Command)
The following procedure assumes WYE connected PTs (DELTAY_X :=
WYE) at the terminals. If DELTAY_X := DELTA and EXT3V0_X := VS, then
replace PTRX by PTRS in the following procedure.
NOTE:
Perform the procedure when
the relay is first installed, but after the
generator being protected is
connected to its step-up transformer
or bus. Remove the 64G2T Relay Word
bit from the relay tripping SEL
OGIC
control equations. Use 64G1P := 5 V
during the test. Set the balance of
tripping functions according to the
requirements of the particular
generator. Leave these tripping
functions in service to protect the
generator in the event that a fault
occurs during the test sequence.
To simplify the following calculations, you can use the Microsoft Excel
spreadsheet, 64G Element Setting Worksheet, which is available on the SEL
product webpage at selinc.com or by contacting the factory.
Step 1. Operate the generator at no load. Use the SEL-700G METER
command and record the values of terminal and neutral third-
harmonic voltage.
VP3_NL := VPX3/PTRX := ______ Third-harmonic terminal
voltage, no load, V secondary
VN3_NL := VN3/PTRN := ______Third-harmonic neutral
voltage, no load, V secondary
Step 2. Increase the generator loading to 100 percent. Record the
values of terminal and neutral third-harmonic voltage. Shut
down the generator; the rest of this procedure does not require
that the generator be in service.
VP3_FL := VPX3/PTRX := _____Third-harmonic terminal
voltage, full load, V secondary
VN3_FL := VN3/PTRN := _____Third-harmonic neutral
voltage, full load, V secondary.
NOTE:
A more elaborate procedure
using the third harmonic
measurements at several load outputs
can be found in the SEL Application
Guide AG2005-08, Setting 100%
Stator Ground Fault Detection
Elements in the SEL-300G Relay. This
guide is written for the SEL-300G, but
it can be easily adapted for the
SEL-700G. The steps in this manual
are the minimum required to set the
element. Using additional load and
third-harmonic data, as discussed in
the application guide, results in a
more secure setting and is
recommended.
Step 3. Calculate the 64RAT setting by using the following equation:
Step 4. Calculate the minimum secure 64G2P setting by using the
following equation:
Step 5. Calculate 64G2Pmin for each load point that third harmonic
voltage data are available, where:
➢
VP3x := third harmonic terminal voltage, VPX3, for
the given load point
➢
VN3x := third harmonic neutral voltage, VN3, for the
given load point
Step 6. Select the largest of the calculated values as 64G2P
Min
.
Step 7. Select the relay setting 64G2P as a value greater than or equal
to 64G2P
Min
. Higher values for 64G2P generally increase the
security of the element. Use Step 8 and Step 9 to verify that
adequate overlap between 64G1 and 64G2 can be maintained
with the selected value of 64G2P.
This equation accounts for the maximum expected element
error, and it adds an additional 5 percent measuring error to
account for possible potential transformer errors.
Step 8. Use the following equation to calculate the low-winding
coverage these settings offer when you operate the machine at
no load:
64RAT
VN3_FL
VN3_NL
+
VP3_FL
VP3_NL
+
-------------------------------------------------------
=
64RAT
___________________
=
64G2P
M in
1.1
0.1
64RAT
VP3x
VN3x
–
+
volts
=
64G2P
M in
__________________ volts
=
Содержание SEL-700G Series
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