S260-20-8
5
Figure 6.
Typical connection diagram for three-wire control with
holding switch.
Figure 7.
Typical connection diagram for two-wire control.
Manual Operation
The switch may be manually opened and closed by operating
the yellow handle under the sleet hood.
NOTE: Manual operation does not affect the status of the electrically
operated actuator. To electrically close a switch which has been manu-
ally opened, the electrical open circuit must be first activated to
change the status of the selector switch for a close operation.
OlL CONDITlON
Oil plays an important role in the proper functioning of the
switch. It provides the internal insulating barrier from phase to
ground, and acts as an arc quencher. Switching operations
cause reductions of some of the oil into chemical compounds,
free carbon and gases. Some of these compounds form water-
absorbing particles which reduce the dielectric strength of the
oil. For effective switch operation the oil must be replaced
before it deteriorates below a safe level. Oil that has been con-
taminated with carbon sludge or has a dielectric strength of
less than 22 kV should be replaced.
Used oil must be reconditioned before using. Filtering may
remove absorbed and free water, and other contaminants to
raise the dielectric strength to an acceptable level. However, it
does not always remove water-absorbing contaminants. Thus,
the dielectric strength of the oil may fall rapidly after the switch
is returned to service. Therefore the switch should be filled
with new oil or oil that has been restored to like-new condition.
oil used in these switches conforms to ASTM Standard
D3487, Type 2; its property limits are listed in Reference Data
R280-90-1, “Oil Specifications and Tests.”
New oil should always be filtered before using even though
it is obtained from an approved source. Passing oil through a
blotter press will remove free water and solid contaminants
such as rust, dirt, and lint. When filtering the oil, aeration
should be kept to a minimum to prevent moisture in the air
from condensing in the oil and lowering its dielectric strength.
INSULATlON LEVEL WITHSTAND TESTS
High-potential withstand tests provide information regarding the
dielectric condition of the switch. Testing is performed at 75% of
the rated low-frequency withstand voltage (See Table 3).
Table 3
Test Voltages for Insulation Level Withstand Test
Switch
BIL
Test
Type
(kV)
Voltage
(kV)
NR
95
26.25
NR*
125
31.5
NRV
125
45.
TEST 1: Proceed as follows:
1. Close the switch.
2. Ground switch tank and head.
3. Apply proper test voltage to one of the bushing terminals.
• The switch should withstand the test voltage for 60 seconds.
TEST 2: Proceed as follows:
1. Open the switch.
2. Ground switch tank and head.
3. Ground the bushing on one side of the switch.
4. Apply proper test voltage to the ungrounded bushing.
• The switch should withstand the test voltage for 60 seconds.
5. Reverse the test and ground connections to the bushings.
6. Again apply proper test voltage to the ungrounded bushing.
• The switch should withstand the test voltage for 60 seconds.
*Accessory 125-kV BIL version
