4-10
Close Logic
Date Code 20010731
SEL-352-1, -2 Instruction Manual
Staggered Close Timer Pickups (RCApu, RCBpu, RCCpu)–Scheme 1
Range:
0–16383 cycles in 1/4-cycle steps
Three timers provide staggered closing of the individual poles. You can set these timers
independently. You must decide the following information about your system to determine
appropriate timer settings:
Which pole should close first?
How long can the system accept a single-pole open/close condition?
How long do the transient conditions persist?
Assuming that you selected A-phase as the first pole to close with a system that can accept a 3-
cycle single-pole condition. In this case, voltage transients exist for less than 1 cycle, and the
timer settings would be as follows:
Set RCApu = 0 to close A-phase instantaneously after the close input is received. Set RCBpu =
1.33 cycles to close one cycle later plus the 120° phase shift of B-phase. Set RCCpu = 2.67
cycles to close one more cycle later plus a second 120° phase shift. All timer settings are from
the instant the close input is received. These settings would close all three phases at the same
point on the corresponding voltage waveform. A single-pole condition would exist from the
time A-phase physically closed to the time C-phase physically closes. This period is 2.67 cycles,
assuming each pole takes the same amount of time to close after close coil energization. This
2.67 cycles is less than the 3-cycle requirement for the system and, in this case, the voltage
transients decay in 1 cycle, which is less than the stagger times of 1.33 cycles between phases.
Maximum Slip Frequency for Control Close (25SC)–Scheme 2
Range:
0.005–0.500 Hz in 0.001-Hz steps
Two synchronizing elements provide separate automatic and manual close operation control. Set
25SC to the maximum allowable slip frequency for automatic close conditions (CLOSE input).
The slip frequency is set in hertz (cycles/second). For timing considerations, a slip of 0.1 Hz is
equivalent to 0.6° per power system cycle. An acceptable slip is dependent on the application.
For synchronizing two parts of the same system, the slip will be very close to zero. Set 25SC in
this case to 0.03 Hz.
The slip frequency setting determines the minimum angle setting allowed for 25AC, so do not
set 25SC to its highest value just to desensitize the synchronism supervision. If 25SC equals 0.5,
the minimum angle for 25AC is 16°.
Maximum Control Close Angle (25AC)–Scheme 2
Range:
32•25SC to 90° (min = 1) in 0.1° steps
Two synchronizing elements provide separate automatic and manual close operation control. Set
25AC to the maximum allowable angle difference for automatic close conditions (CLOSE
input). The SEL-352 Relay will close an output contact based on the slip frequency and breaker
close time so that the two systems are somewhere within the window. If the two systems are
slipping by at a consistent rate, the SEL-352 Relay will initiate the close so that the breaker
Содержание SEL-352-1
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