Schweitzer Engineering Laboratories SEL-700G Series, Instruction Manual

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4.168
SEL-700G Relay Instruction Manual Date Code 20170814
Protection and Logic Functions
Group Settings (SET Command)
how many degrees VS constantly lags VABY. In this application, voltage input
VAY-VBY
has to be connected and has to meet the “healthy voltage” criteria
(settings 25VHIY and 25VLOY—see Figure 4.112). For situations where VS
cannot be in phase with VABY, VBCY, or VCAY, the angle setting choices (0,
30, …, 300, or 330 degrees) are referenced to VABY.
See Figure 4.107 for examples of wye and delta-connected voltages and
associated SYNCP and 25RCF for both X and Y sides.
Synchronism-Check Elements Voltage Inputs
The two synchronism-check elements are single-phase elements, with single-
phase voltage inputs
VPY
and
VS
used for both elements:
➤
VPY Phase input voltage (
VAY
,
VBY
, or
VCY • 25RCFY
for
DELTAY_Y := WYE;
VABY
,
VBCY
, or
VCAY • 25RCFY
for
DELTAY_Y:= DELTA), designated by setting SYNCPY (If
SYNCPY is set to one of the angle settings, then
VPY =
VAY • 25RCFY
or
VABY • 25RCFY,
depending on the
DELTAY_Y setting.)
➤
VS Synchronism-check voltage, from SEL-700G rear-panel
voltage input
VS
For example, if the rear-panel voltage input
VS-NS
is connected to BC phase-
to-phase, then set SYNCPY := VBCY . The voltage across terminals VBY-VCY is
synchronism checked with the voltage across terminals
VS-NS
(see
Figure 4.107 (c).
System Frequencies Determined From Voltages V1Y and VS.
To
determine slip frequency, first determine the system frequencies on both sides
of the circuit breaker. Voltage VS determines the frequency on one side.
Voltage V1Y (positive-sequence utility tie voltage) determines the frequency
on the other side.
Synchronism-Check Elements Operation
Refer to Figure 4.112 and Figure 4.113.
Voltage Window.
Refer to Figure 4.112. Single-phase voltage inputs
VPY
and
VS
are compared to a voltage window, to verify that the voltages are “healthy”
and lie within settable voltage limits 25VLOY and 25VHIY. If both voltages
are within the voltage window, the following Relay Word bits assert:
59VPY indicates that voltage VPY is within voltage window setting
limits 25VLOY and 25VHIY
59VSY indicates that voltage VS is within voltage window setting limits
25VLOY and 25VHIY
Other Uses for Voltage Window Elements.
If voltage limits 25VLOY and
25VHIY are applicable to other control schemes, you can use Relay Word bits
59VPY and 59VSY in other logic at the same time you use them in the
synchronism-check logic.
If synchronism check is not being used, Relay Word bits 59VPY and 59VSY can
still be used in other logic, with the voltage limit settings 25VLOY and 25VHIY set
as necessary. Enable the synchronism-check logic (setting E25Y := Y) and make
settings 25VLOY, 25VHIY, and 25RCFY. Use SEL
OGIC
control equations to
apply Relay Word bits 59VPY and 59VSY to your logic scheme. Even though
synchronism-check logic is enabled, the synchronism-check logic outputs
(Relay Word bits SFY, 25AY1, and 25AY2) do not need to be used.
NOTE:
Settings SYNCPY := 0 and
SYNCPY := VABY are effectively the
same (voltage VS is directly
synchronism checked with voltage
VABY; VS does not lag VABY). The
relay displays the setting entered
(SYNCPY := VABY or SYNCPY := 0).