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Recloser operation
HAZARDOUS VOLTAGE. OPEN CT SECONDARIES CAN GENERATE
HIGH VOLTAGES. CONTACT WITH CT PINS OF THE DISCONNECTED
CABLE CAN CAUSE ELECTRIC SHOCK AND MAY RESULT IN
PERSONAL INJURY. OPEN RECLOSER CONTACTS AND OPEN
DISCONNECT SWITCHES BEFORE DISCONNECTING CONTROL
CABLE. FAILURE TO COMPLY COULD CAUSE DEATH OR SEVERE
PERSONAL INJURY.
HAZARDOUS VOLTAGE. DO NOT TOUCH THE PINS INSIDE THE
CONTROL CABLE CONNECTOR. PINS COULD BE ENERGIZED IF A
TRIP OR CLOSE SIGNAL IS ISSUED. FAILURE TO COMPLY COULD
CAUSE SEVERE INJURY OR DEATH.
6. Remove the control AC sensing and power connections
from the control using a separate disconnect switch.
7. Disconnect the control cable from the recloser.
N
ote:
Do not disconnect the recloser control cable from
the recloser unless all of the above steps have been
completed. The Form 7 control in single-phase trip/
three-phase lockout mode or three-phase trip/
three-phase lockout mode will lock out all three
reclosers if one control cable is disconnected.
8. Follow standard utility procedures regarding removal of
recloser from service.
Eaton recommends transporting NOVA NX-STS
•
reclosers in the closed position to maximize the
operational performance of the unit
Recloser operation
THIS EQUIPMENT IS NOT INTENDED TO PROTECT HUMAN LIFE.
FOLLOW ALL LOCALLY APPROVED PROCEDURES AND SAFETY
PRACTICES WHEN INSTALLING OR OPERATING THIS EQUIPMENT.
FAILURE TO COMPLY CAN RESULT IN DEATH, SEVERE PERSONAL
INJURY, AND EQUIPMENT DAMAGE.
HAZARDOUS VOLTAGE. DO NOT RELY ON THE OPEN POSITION OF
THE YELLOW OPERATING HANDLE OR THE CONTACT POSITION
INDICATOR; IT DOES NOT ENSURE THAT THE LINE HAS BEEN
DE-ENERGIZED. ALWAYS ESTABLISH A VISIBLE DISCONNECT.
FAILURE TO FOLLOW PROPER SAFETY PRACTICES CAN RESULT IN
CONTACT WITH HIGH VOLTAGE, WHICH WILL CAUSE DEATH OR
SEVERE PERSONAL INJURY.
10
INSTALLATION AND OPERATION INSTRUCTIONS MN280103EN March 2023 www.eaton.com
WARNING
WARNING
WARNING
WARNING
A current transformer senses line current from each phase
of the NOVA NX-STS recloser and inputs this information
to the Form 7 recloser control. The recloser responds to
trip and close commands from the control, per the settings
programmed in the control. Refer to Service Information
MN280095EN Form 7 Microprocessor Based Pole Mount
Recloser Control Installation and Operation Instructions for
control operation information.
Vacuum interrupter
Arc interruption takes place within the sealed vacuum
interrupter. Eaton's vacuum interrupters employ axial-
magnetic field contacts. Slots are machined into the contact
support structure, producing a magnetic field along the axis
of the interrupter. This axial-magnetic field keeps the arc in
an easier-to-interrupt diffuse mode, resulting in less power
in the arc that needs to be dissipated, resulting in extended
operating duty.
Mechanism tripping and closing
The NOVA NX-STS recloser is comprised of three single-
phase recloser mechanisms in a single tank. Each recloser
utilizes a magnetic actuator for fast, efficient latching. A rare-
earth neodymium magnet provides latching forces in excess
of 240 pounds, eliminating the need for mechanical latches.
While in the closed position, the magnetic field established
by the magnet is coupled with the iron assembly to provide a
latching force for the movable plunger. The magnetic force is
concentrated at the plunger-assembly interface and provides
the latching force required to keep the mechanism closed.
The assembly also houses a single coil (used for trip or close)
that provides the energy to operate the mechanism.
To open the main contacts, the coil is pulsed with electrical
current, which cancels the magnetic field. A compression
spring in the center of the coil moves the plunger assembly
to the open position. As the plunger moves, the magnetic
field strength decreases as the air gap increases, due to the
difference in the relative permeability of free space and the
ferrous plunger. Once in the open position, the compression
spring keeps the unit open.
Trip/close capacitors (in the control) store the necessary
energy for operating the recloser. The capacitors have been
sized to ensure trip energy is available following any close
operation. The charging of these capacitors occurs within
the control—no capacitors are present in the recloser.
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