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M-0329B Instruction Book
1.1
Introduction
Defective tapchanger controls can create either
too high or too low a voltage along the line, possibly
damaging customer's motors, computers or
televisions. Even when the control is operating
properly, customers close to the transformer may
receive dangerously high voltage as the line drop
compensator attempts to maintain a constant
voltage under heavy load at a central point on the
distribution line. The Beckwith M-0329B LTC
Backup Control can be installed as a solution to
both of these problems.
Designed to replace the Beckwith M-0029 LTC
Control Backup Relay as well as the M-0145 First
Customer Protector, the single-phase, solid-state
M-0329B has three main functions:
1.
Prevent a defective LTC tapchanger
control from running the voltage outside
the upper and lower voltage limits.
2.
Prevent the line drop compensator from
raising the voltage too high under full
load or overload conditions.
3.
Lower the voltage if the regulated voltage
goes above the Block Raise setpoint by
a fixed bandwidth, as shown in Figure 1.
The Block Raise and Block Lower voltage levels
are set by accurately calibrated dials, labeled
BANDCENTER
and
BANDWIDTH
, similar to those
found on LTC transformer controls.
The amount of Deadband between the Block Raise
and the Lower levels can be selected by the
customer, using a switch on the side of the unit.
The
BANDCENTER
dial has settings from 100 V
rms to 140 V rms that allow the relay to match any
transformer control.
Above the Block Raise level, the relay will detect
voltage above the Lower setpoint. This point is at a
fixed level above the Block Raise, and will initiate a
lower tapchange operation if exceeded for an
adjustable amount of time (1 to 30 sec) as set on
the
TIME DELAY
control.
Blocking contacts on the M-0329B will operate
within 0.2 seconds after a voltage excursion to
prevent the defective transformer control from
causing another tapchange. After a fixed 3 minute
time delay, if the voltage excursion is still present,
the
ALARM
contact is activated to indicate control
failure.
Under full or overload conditions, the M-0329B
automatically takes over as an upper voltage limit
control, not affected by load current, to prevent
damage to equipment close to the transformer.
While the Block Raise contact prevents a raise
operation, a Lower contact forces the tapchanger
down if the primary voltage should subsequently
rise.
FIXED DEADBAND
LOWER
BLOCK RAISE
BLOCK LOWER
V
BL
V
BR
VC
BANDCENTER
1/2 BW
1/2 BW
ADJUSTABLE
BANDWIDTH
Figure 1
Setpoint Voltage Levels