Schweitzer Engineering Laboratories SEL-700G Series, Instruction Manual

Page: 83 / 824

2.31
Date Code 20170814 Instruction Manual SEL-700G Relay
Installation
SEL-700G1+ Generator Relay Application Example 2
SEL-700G1+ Generator Relay Application Example 2
Illustrating the 67N
Element
This example shows an SEL-700G1+ Relay application with full generator
protection. The application involves several high-impedance grounded
generators connected to the same bus. This application calls for a sensitive
neutral directional overcurrent element (67N) looking into the generator. A
core-balance CT is installed to achieve greater sensitivity. The output of the
core-balance CT is connected to the
IN
input on the relay. The terminal PTs in
this application are connected in open-delta, but the 67N element requires
zero-sequence voltage (3V0) for polarization. In this application, by setting
EXT3V0_X := VS, connect external 3V0 to
VS-NS
input for use with 67N
element. When external 3V0 is connected to the
VS-NS
input, the relay disables the
synchronism-check (25X) and autosynchronism functions. Likewise, external
3V0 can also be connected to the
VN-NN
input (set EXT3V0_X := VN) for use
with the 67N element, in which case the relay disables the 64G function.
The generator protection for this application includes the following elements:
➤
Phase differential element (87)
➤
Field ground element (64F)—requires SEL-2664 Field Ground
Module
➤
100% Stator Ground Protection (64G elements)
➤
RTD inputs—requires SEL-2600 RTD Module or RTD input
card in Slot D
➤
Zero-Sequence Voltage-Polarized Directional Element for
High-Impedance Grounded System (67N)
When the voltage inputs
VS-NS
or
VN-NN
are unused in the corresponding
models (SEL-700G0+, SEL-700G1+ or SEL-700GT+) and the setting
DELTAY_X := DELTA, then you can use one of the available voltage inputs to
connect an external zero-sequence voltage. In such an application, the setting
EXT3V0_X must also be set accordingly. External 3V0 is neither required nor
allowed if the terminal PTs are wye connected (DELTAY_X := WYE). You
can use the external 3V0 with the following elements. Refer to Section 4:
Protection and Logic Functions for more details.
➤
100% Stator Ground Protection Elements (64G1, 64G2; refer
to Section 4: Protection and Logic Functions, 100% Stator
Ground Protection Elements)
➤
Ground Overvoltage Elements (59GX1, 59GX2; refer to
Section 4: Protection and Logic Functions, Over- and
Undervoltage Elements)
➤
Zero-Sequence Voltage-Polarized Directional Element With IG
as Operate Quantity (67G; refer to Section 4: Protection and
Logic Functions, Overcurrent Elements on page 4.87 and
Directional Elements on page 4.101)
➤
Zero-Sequence Voltage-Polarized Directional Element With IN
as Operate Quantity (67N; refer to Section 4: Protection and
Logic Functions, Overcurrent Elements on page 4.87 and
Directional Elements on page 4.101)
Note that the 67G element listed previously could be achieved by setting the 50G
element with the appropriate directional control setting. Similarly, the 67N element
listed previously could be achieved by setting the 50N element with the appropriate