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4.58
SEL-787 Relay
Instruction Manual
Date Code 20081022
Protection and Logic Functions
Voltage-Based Protection
Figure 4.36
Volts/Hertz Inverse-Time Characteristic, 24IC = 2
Power Elements
You can enable up to two independent three-phase power elements in the
SEL-787 relay. Each enabled element can be set to detect real power or
reactive power. When voltage inputs to the relay are from delta connected PTs
or when single voltage input is used, the relay cannot account for unbalance in
the voltages in calculating the power. Take this into consideration in applying
the power elements.
With
SEL
OGIC
control equations, the power elements provide a wide variety of
protection and control applications. Typical applications are:
➤
Overpower and/or underpower protection/control
➤
Reverse power protection/control
➤
VAR control for capacitor banks
24ITD = 5.0
24ITD = 7.5
24ITD = 1.0
24ITD = 0.1
100
120
140
160
180
200
0.01
0.1
1
10
100
1000
10000
24C2T Operating Time
(seconds)
Volts/Hertz (%)
(24IP = 100%)
24ITD = 10.0
24ITD = 0.5
t
p
24 ITD
3
V
sec
PTR
•
•
freq
-----------------------------------------
FNOM
VNOM 10
3
⋅
--------------------------------
•
24 IP
100%
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Содержание SEL-787
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