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Step 15—Arcing Horn Installation
Arcing horns consist of a movable straight horn
and a stationary horn. Arcing horns for 242kV
switches are essentially the same except that the
stationary horn contacts the movable horn at the
surface between the end of the blade and the small
corona ball affixed at the end of the movable horn.
If arcing horns have been supplied, install and
adjust them after mounting the switches on the
structure.
To install the movable straight horn:
1.
Screw the straight horn into the blade end.
2.
Tighten the locking nut seat securely against
the end of the blade.
To install the stationary horn:
1.
Bolt the stationary horn on the jaw with the
saddle clamp.
2.
Adjust or slightly bend the stationary horn to
apply light contact pressure between the two
horns over the entire length of the stationary
horn.
Step 16—Installation of Corona Rings and Balls
The 242kV switches use corona rings at the jaw
end and a small ball on each end of the blade.
(Switches rated at 169kV and below do not require
corona rings and balls.)
If corona rings and balls have been supplied,
install these components as shown on the single
pole drawings.
Important: Prepare areas where ring supports
contact switch parts as per instructions for
aluminum-to-aluminum connections on this page.
Step17—Final Checks
The completed 3-pole installation should be
checked for the following:
1.
In the open position, the blades should be
between 90° to 93°.
2.
In closing, blades should make central entry
into their jaws at approximately the same time.
3.
In the closed position, all blades must be in
full contact and horizontal within tolerances,
see page 4.
4.
All jaw mounting bolts are tightened with
switch in close position.
5.
In opening, the blades should rotate to relieve
the jaw contact pressure.
6.
Tighten all lock nuts and pierce bolts.
7.
For swing handle operating mechanisms:
a.
Operate the switch and move the
adjustable lock castings until they exert
pressure against the handle in both the
open and closed positions of the switch.
This provides a slight torsional wind-up
in the operating pipe.
b.
Tighten the two piercing set screws on
the handle clamp until holes are punched
in pipe and continue until the screws are
firmly seated.
8.
For worm gear operating mechanisms:
If all stops at switch elevation have been set,
including the offset bearing, then it is safe to
reinstall the position indicators on the worm
gear mechanism. These indicators should not
quite touch the raised boss on the worm gear
housing in either the open or closed positions.
There is a possibility of damage to the
indicators or the coupling if this is not observed
Terminal Connections
The aluminum surface of the terminal connection
provides for easy current transfer.
Notice: In cases where a copper conductor is used,
bolt a tinned terminal clamp (if available) to the
aluminum switch terminal pad.
If a non-tinned terminal clamp is used, apply a
liberal amount of electrical joint grease at the joint
and all over the pad of the fitting.
To connect aluminum-to-aluminum terminals:
1.
Clean all contact surfaces of conductors and
fittings using a stiff wire brush to remove heavy
oxide coatings until the aluminum finish is
visible and restored.
2.
Coat these now clean contact areas with a
liberal amount of corrosion inhibitor such as
NO-OX-ID”A Special” or No. 2 EJC.
3.
Abrade the contact surface through the
corrosion inhibitor again using the stiff wire
brush.
Notice: Do not remove the compound
.
4.
Connect the terminals and torque the bolts as
per Table 1.
