Date Code 20020215
Overcurrent, Voltage, Synchronism Check, and Frequency Elements
3-33
SEL-351R Instruction Manual
Figure 3.23: Channel VS Voltage Elements
Accuracy
Pickup: ±1 V and ±5% of setting
Transient Overreach:
±5% of setting
Voltage Element Operation
Note that the voltage elements in Table 3.8, Figure 3.21, and Figure 3.22 are a combination of
“undervoltage” (Device 27) and “overvoltage” (Device 59) type elements. Undervoltage
elements (Device 27) assert when the operating voltage goes below the corresponding pickup
setting. Overvoltage elements (Device 59) assert when the operating voltage goes above the
corresponding pickup setting.
Undervoltage Element Operation Example
Refer to Figure 3.21 (top of the figure).
Pickup setting 27P1P is compared to the magnitudes of the individual phase voltages V
A
, V
B
, and
V
C
. The logic outputs in Figure 3.21 are the following Relay Word bits:
27A1 = 1 (logical 1), if V
A
< pickup setting 27P1P
= 0 (logical 0), if V
A
≥
pickup setting 27P1P
27B1 = 1 (logical 1), if VB < pickup setting 27P1P
= 0 (logical 0), if VB
≥
pickup setting 27P1P
27C1 = 1 (logical 1), if VC < pickup setting 27P1P
= 0 (logical 0), if VC
≥
pickup setting 27P1P
3P27 = 1 (logical 1), if all three Relay Word bits 27A1, 27B1, and 27C1 are asserted
(27A1 = 1, 27B1 = 1, and 27C1 = 1)
= 0 (logical 0), if at least one of the Relay Word bits 27A1, 27B1, or 27C1 is
deasserted (e.g., 27A1 = 0)
Содержание SEL-351R
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