4.5
Date Code 20170814
Instruction Manual
SEL-700G Relay
Protection and Logic Functions
Group Settings (SET Command)
Figure 4.1
Phase Rotation Setting
The X_CUR_IN setting is available only in SEL-700G1 relays. For most
applications where the X-side CTs are located on the neutral side of the
generator (see Figure 2.23), set X_CUR_IN := NEUT. However, if the CTs
are connected on the terminal side of the generator, set the X_CUR_IN to
TERM. The SEL-700G0 and SEL-700GT+ relays use X_CUR_IN := TERM
automatically and cannot be changed. The relays use this setting to configure
Ground Differential (see Figure 4.16) and Restricted Earth Fault (see
Figure 4.17) elements for proper operations.
The CT ratio settings configure the relay to accurately scale measured values
and report the primary quantities. Calculate the phase and neutral CT ratios by
dividing the primary rating by the secondary rating.
EXAMPLE 4.1
Phase CT Ratio Setting Calculation
Consider an application where the phase CT rating is 100:5 A.
Set CTR := 100/5 := 20.
Set the INOM setting to nominal machine current by using the following
equation:
The relay negative-sequence overcurrent and differential elements use the
INOM setting.
The X-side phase CTs must always be connected in WYE. The CTCONY
setting (Y-side phase CT connection) is used to appropriately configure
differential protection. This setting is available only in the SEL-700G1 relays.
Set the DELTAY_X setting to define whether relay ac potentials are supplied
by three-wire (for example, open-delta) or four-wire wye connected generator
voltage transformers. Similarly, set the DELTAY_Y for the Y side. See
Figure 2.16 for the voltage connection examples and appropriate setting.
The PTRX, PTRY, PTRS, and PTRN settings configure the relay voltage
inputs to measure and scale the voltage signals correctly. Set the PTRs equal
to their respective VT ratio. The synchronism check and neutral voltage inputs
(VS and VN) are optional single-phase voltage inputs. See Example 4.2 for
sample calculations to set the PTRX setting.
where
MVA
= the generator-rated output
kV
= generator-rated phase-to-phase voltage
CTRX
= the phase current transformer ratio to one
B
C
A
C
PHROT = ABC
A
PHROT = ACB
B
INOM
MVA
1000
1.73
kV
--------------------------------
CTRX
--------------------------------------
A
=
Содержание SEL-700G Series
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