GROUND VOLTAGE MONITOR SYSTEM
Assigned PE# 0462
GVMon from Balfour Beatty Rail continuously scans a realtime analog input that indicates the ground-to-negative
rail voltage of the traction system. GVMon allows negative
excursions (earth ground more negative than the rail) of
any magnitude, but will fire a SCR to connect the rail to
earth ground if the earth ground becomes positive with
respect to the rail by an amount that equals or exceeds the
preset (adjustable) threshold voltage.
Features
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Digital meter reads rail voltage and number
of operations
Adjustable pick-up voltage for ground SCR
Adjustable trip time to prevent tripping due to rail drop
during train start
Sensitive current detection provides detection and lock
out on a feeder with a catenary to earth leakage of
50 ohms
Built in diagnostics description
The unit consists of a voltage detector, a current detector,
an eight bit micro controller, output relay board, and an LCD
display. The unit is housed in a metal enclosure with two
(2) power supplies to convert 125VDC input control power
to isolated low voltage (5V) for micro controller power and
SCR gate drive. Output contacts are provided for breaker
tripping and annunciation display.
The display is mounted on the enclosure door and digitally
displays negative to ground voltage. A pushbutton converts
the display to an operations counter when pressed.
Specifications
The unit monitors the voltage from negative to ground and
displays this voltage on a
digital display. When the
voltage exceeds the setting
level (typically -50 volts)
for a short time (typically
50mS), the micro controller
triggers an SCR providing a
current path from ground
to negative. The condition described commonly is the
result of a catenary to earth (ground) fault such that the
current return path is through earth to rail. A current
sensor consisting of a diode with parallel resistors is set for
approximately 10 amps. GV Monitor will close the breakers
back if the negative to ground voltage disappears in a set
time. It will lock out specific breakers which have a constant
Negative to Ground voltage.
1205 W. Dewey St., Goldsboro, NC 27530 • Tel: 919.432.1470 • Fax: 919.800.3834 • Web: www.bbiius.com • E-mail: rail@bbiius.com