the covers are removed. These also
should be grounded before being
handled.
should be grounded before being
handled.
Induced voltages from nearby energized
lines can cause serious accidents if they
are not handled properly. Employees
should be constantly reminded of the
possibility of induced charges and the
dangers Involved.
lines can cause serious accidents if they
are not handled properly. Employees
should be constantly reminded of the
possibility of induced charges and the
dangers Involved.
Induced voltages of steady-state nature
are often encountered when the
deenergized circuit closely parallels
another energized circuit. In such
instances, protective grounds should be
applied to the circuit at the bushings to be
inspected. If electrical tests are to be
conducted, the grounded leads may be
removed which would prevent such tests.
Refer to FIST Volume 1-1.
are often encountered when the
deenergized circuit closely parallels
another energized circuit. In such
instances, protective grounds should be
applied to the circuit at the bushings to be
inspected. If electrical tests are to be
conducted, the grounded leads may be
removed which would prevent such tests.
Refer to FIST Volume 1-1.
C. Field Testing.- Field testing generally
requires work in the proximity of
energized equipment. A hazard analysis
should be performed and a short safety
meeting on the site should be conducted
prior to beginning field tests on bushings.
requires work in the proximity of
energized equipment. A hazard analysis
should be performed and a short safety
meeting on the site should be conducted
prior to beginning field tests on bushings.
Adjacent high-voltage equipment which
may be hazardous to workmen shall be
marked off with visible warning devices,
such as tape, rope, or portable fence
sections. Signs reading "DANGER - DO
NOT PASS THIS BARRIER, -- DANGER
- HIGH VOLTAGE," or similar notice
shall be placed along the barriers facing
the working area.
may be hazardous to workmen shall be
marked off with visible warning devices,
such as tape, rope, or portable fence
sections. Signs reading "DANGER - DO
NOT PASS THIS BARRIER, -- DANGER
- HIGH VOLTAGE," or similar notice
shall be placed along the barriers facing
the working area.
IV. Maintenance, Inspection,
and Testing
and Testing
A. General.- All high-voltage bushings
should be inspected periodically to
intervals of not over 3-5 years. The
inspections should include power-factor
tests for all bushings rated above 115 kV.
Lower voltage bushings should also be
tested if there is reason to suspect they
may be deteriorated. Bushings showing
signs of deterioration should be tested at
intervals of 6 months to 1 year and
should be inspected periodically to
intervals of not over 3-5 years. The
inspections should include power-factor
tests for all bushings rated above 115 kV.
Lower voltage bushings should also be
tested if there is reason to suspect they
may be deteriorated. Bushings showing
signs of deterioration should be tested at
intervals of 6 months to 1 year and
removed from service if the tests show a
dangerous condition.
dangerous condition.
1. Terminal caps end connectors.
Check for tightness to avoid poor contact
and resultant heating.
Check for tightness to avoid poor contact
and resultant heating.
2. Capacitance taps and power-factor
test electrodes.- Check to determine
proper grounding for bushings with a
grounded capacitance tap and for power-
factor test electrodes. Examine for proper
gasketing to prevent entrance of mois-
ture.
test electrodes.- Check to determine
proper grounding for bushings with a
grounded capacitance tap and for power-
factor test electrodes. Examine for proper
gasketing to prevent entrance of mois-
ture.
3. Cement.- Check for crumbling or
chipped and repair as required.
chipped and repair as required.
4. Gaskets.- Check gaskets for
deterioration, looseness, and leaking.
Loose gaskets should be replaced or
painted with General Electric lacquer or
other suitable oil-proof sealer, and
tightened. Finding a loose gasket or seal
may mean that moisture has entered the
bushing, and checks should be made to
determine if moisture is present. The
bushing should be dried out if necessary.
deterioration, looseness, and leaking.
Loose gaskets should be replaced or
painted with General Electric lacquer or
other suitable oil-proof sealer, and
tightened. Finding a loose gasket or seal
may mean that moisture has entered the
bushing, and checks should be made to
determine if moisture is present. The
bushing should be dried out if necessary.
5. Metal pads.- Check and paint as nec-
essary. Examine structural parts, such as
clamping rings and washers, for cracks or
breaks.
essary. Examine structural parts, such as
clamping rings and washers, for cracks or
breaks.
6. Solder seals.- Check for cracks and
leaks and repair as necessary.
leaks and repair as necessary.
B. Visual Inspection Annually with
Binoculars.- The visual inspection should
include the following items:
Binoculars.- The visual inspection should
include the following items:
1. Porcelain.- Check for chips, cracks,
and contamination. Minor chips may be
painted with an insulating varnish to ob-
tain a glossy finish which will shed dirt
and moisture. Superficial cracks that do
not affect the mechanical or electrical
strength of the bushing may be sealed
with insulating varnish or epoxy. Bush-
ings with major chips or cracks which
appreciably decrease the creepage dis-
tance should be replaced. The surface of
the porcelain should be cleaned as
and contamination. Minor chips may be
painted with an insulating varnish to ob-
tain a glossy finish which will shed dirt
and moisture. Superficial cracks that do
not affect the mechanical or electrical
strength of the bushing may be sealed
with insulating varnish or epoxy. Bush-
ings with major chips or cracks which
appreciably decrease the creepage dis-
tance should be replaced. The surface of
the porcelain should be cleaned as
3
(FIST 3-2 11/91)