10
S&C Instruction Sheet 663-590
Table 3
Table 3. Inspection and Maintenance Procedures for the Enclosure and for
Components in High-Voltage Compartments
①
WARNING
When access to high-voltage compartments is required,
it should be restricted to qualified persons who observe
the following procedures:
1 . Adhere to prescribed safety rules at all times .
2 . Be certain fuses, Mini-Rupter Switches, their
mechanisms, and any other devices are disconnected
from all power sources and are grounded before that
device is inspected, serviced, or repaired .
3 . Discharge all stored-energy switch operators by using
the manual operating handle .
4 . Always assume both sets of terminals on any Mini-
Rupter Switch or fuse are energized unless proven
otherwise by test, by visual evidence of open-circuit
conditions on both terminal ends, or by grounding .
5 . All voltage sensors must be disconnected when
external voltage is used to test any secondary-side
wiring or devices to avoid energizing the high-voltage
conductors through the voltage sensors . To disconnect
the voltage sensors, transfer the input plug from the
input receptacle to the shorting receptacle .
6 . Test for voltage . Qualified persons should be certain
they have and know how to operate the correct test
equipment for determining the voltage on both sets of
terminals on any fuse or interrupter switch .
7 . After the gear has been completely disconnected from
all sources of power and tested, properly connect
suitable grounding leads to both sides of the
equipment, that is, to the incoming and outgoing
phases of the equipment to be maintained .
8 . Install dual-purpose front barriers, if furnished, in the
“slide-in” position .
■
If a contact on either side of a
barrier is energized, do not leave the barrier in the
“slide-in” position for longer than one week . These
barriers are intended for temporary use only to isolate
the blades of the switch from the main contacts while
work is being performed . If the barriers are left in the
“slide-in” position for extended periods of time, there
is the possibility of corona discharge to the barriers .
Prolonged exposure to corona discharge may damage
the barriers and result in a flashover .
9 . When the equipment to be inspected is not of S&C
manufacture, follow instructions supplied by the
manufacturer of the equipment .
10 . Make certain the enclosure is properly grounded to
the station or facility ground . No equipment should be
returned to service unless such grounds are properly
made .
Note: Occasionally, low-voltage components may
require maintenance . The maintenance of low-voltage
components isolated from high-voltage compartments
may be performed under the safety rules for equipment
rated 600 Volts or less . If maintenance is to be performed
on devices connected to the secondary of a voltage
sensor, short-circuit the secondary connections . A sepa-
rate drawing will be provided with any replacement part
explaining how to properly short-circuit the secondary
connections .
When returning the equipment to service, the following
procedures should be observed:
1 .
Withdraw any dual-purpose front barriers, if fur-
nished, from the “slide-in” position and return them
to their normal, suspended position .
2 . Make sure that fuses (or switch blades instead of
fuses) are closed and securely latched .
3 . Make sure any grounding means are removed before
energizing the associated Mini-Rupter Switch or
fuse .
4 . Close each door permitting access to high voltage
and make sure that the associated door latching
mechanisms are securely latched before energizing
the circuit or operating any switching device .
5 . Make certain the input plug is in the input receptacle .
6 . Make certain the Mini-Rupter Switches are in the cor-
rect positions (Open or Closed) as dictated by the
electric power system design .
7 . Padlock all doors before leaving the installation site,
even momentarily . Observe this procedure even in
those cases where the gear is accessible only to
qualified persons .
■
Dual-purpose front barriers for switches and fuses are
optional on units shipped before September 1994 . They
became standard after September 1994 .
