BECKWITH ELECTRIC M-3425A, Инструкция

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4–83
System Setup and Setpoints – 4
59 Phase Overvoltage
The Phase
Overvoltage function (59) may be used
to provide overvoltage protection for the generator.
The relay provides overvoltage protection functions
with three voltage levels and three definite-time
setpoints, any one or more of which can be
programmed to trip the unit or send an alarm. This
is a true 3-phase function in that each phase has
an independent timing element.
The 59 function can be programmed to use phase
voltage (any one of the three phases) or positive
sequence voltage as input.
Positive and negative sequence voltages are
calculated in terms of line-to-line voltage when Line
to Line is selected for V.T. Configuration.
V
1
= 1/3

(V
ab
+aV
bc
+ a
2
V
ca
)
V
2
= 1/3

(V
ab
+a 2
V
bc
+ aV
ca
)
Magnitude measurement depends on the 59/27
Magnitude Select setting (See Section 4.2 Setup
System). When the RMS option is selected, the
magnitude calculation is accurate over a wide
frequency range (10 to 80 Hz) and the accuracy
of the time delay is +20 cycles. If DFT option is
selected, the magnitude calculation is accurate near
50 or 60 Hz, and the timer accuracy is +1 cycle.
When the input voltage select is set to positive
sequence voltage, the 59 functions uses DFT to
measure the positive sequence voltage, irrespective
of DFT/RMS selection. Ranges and increments are
presented in Figure 4-62.
Generator capability is generally 105% of rated voltage.
59 #2 and 59 #3 screens are identical to 59 #1.
59 #1 INPUT VOLTAGE SEL.
phase_volt pos_seq_volt
59 #1 PICKUP
Volts
59 #1 DELAY
Cycles