BECKWITH ELECTRIC M-2601, Инструкция

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Applications – 4
4–3
RAILS AND LIMITS
Lower Voltage Limit
If the value of the regulated voltage is below the
Lower
Voltage Limit, the control will not time
towards a lower tapchange.
Upper Voltage Limit
If the value of the regulated voltage exceeds the
Over Voltage Limit, the control will not time towards
a raise tapchange. If the value of the regulated
voltage exceeds the overvoltage limit plus a 2 volt
Deadband, the control will issue a lower command
in one second until the regulated voltage falls, at
minimum, back into the deadband.
Tap Position Limits
The control is programmable to prevent automatic
tapchanges that will allow excursions beyond the
set values of minimum and maximum tap positions.
This function does not have priority over any values
of Voltage Limits programmed into the control.
4.2 Voltage Regulation
Standard Control Settings
With the Level 1 password implemented, the
following setpoints are adjustable: BandCenter,
Line Drop Compensation, Upper Voltage Limit,
Lower Voltage Limit, and VRQF. The History
sample period is also adjustable. Alarm Enables
and Resets are settable, and VAr management
can be enabled or disabled. See Table 4-1 for
the ranges. All other setpoints and configuration
choices require level 2 password clearance.
Password Applicability
Metering panel and list can be read under all
circumstances.
No Password: Setpoint screen can be read, but
not changed. Config screen cannot be read.
Level 1 Password: Setpoint screen can be read,
but only bandcenter, limits, alarms, LDC, VRQF
and history sampling can be changed. Ratio Corr,
multipliers, CT phasing, counters, and clock cannot
be changed. Config screen cannot be read.
Level 2 Password: All parameters in Setpoint
screen can be changed. Config screen can be
read and changed.
The control will send commands to the tapchanger
to change taps as needed to hold the voltage within
the bandwidth setting, as modified by the line drop
compensation settings.
The control will only respond to an out-of-band
voltage excursion after the timer has reached the
Autodaptive
®
time delay which is set by the
algorithms. The algorithm functions as an
integrating timer dependent on the VRQF, which
increments during time out-of-band and decrements
during time in band, but not below zero. The further
the voltage is away from the setpoint, the shorter
the time delay between tapchanges and vice versa.
Bandcenter
The center of the voltage band is adjustable from
90 to 135 V ac in 0.1 volt increments.
Voltage Regulation Without LDC
When the control is only used to regulate the
voltage on the transformer or regulator low-side
bus, the only input required is voltage from a line-
to-line or line-to-ground VT with a nominal 120 V
ac secondary.
Voltage Regulation with LDC
When it is desirable to regulate the voltage at
some distance from the transformer or voltage
regulator, the Line Drop Compensation (LDC)
feature is used.
The bandcenter function is set the same as if LDC
were not used, and still represents the desired
voltage at the remote location.
A classical approach can be used to determine
the settings for the LDC, however this assumes
a load center point and is usually not applicable
to the typical distribution feeder. For more
information, contact Beckwith Electric for
Application Note #17.
A simpler method is recommended which will work
for most applications. This involves analyzing the
feeders leaving the station and estimating the
reactance/resistance (X/R) ratio. The reactive and
resistive line drop compensation setpoints should
then be entered in this same X/R ratio.