Section VII. MAINTENANCE OF LOW VOLTAGE SECTION

Section VII. MAINTENANCE OF LOW VOLTAGE SECTION

3-13. General

(load break switch) and control sources

Instructions contained in this section are for operator's

have been disconnected. See paragraph 2-

information and guidance in maintenance of the low

13 c.

voltage switchgear section.

3-15. Circuit Breakers (Main and Feeder)

WARNING

a. Inspection of the circuit breaker is recom-

Before any covers are removed or doors

mended at least once a year. More frequent in-

opened which permit access to the primary

spections are recommended if severe load conditions,

or secondary circuits it is essential that the

dust, moisture or other unfavorable conditions exist. If

the breaker remains open or closed for a period of six

circuits be de-energized. See paragraph 2-

months it is recommended to open and close it several

13.

times in succession, preferably under load. A complete

inspection of the breaker including contacts and are

3-14. Enclosure

quenchers should always be made after the breaker has

a. Check and inspect all devices, doors, latches

interrupted a short circuit. It should be operated slowly

and hinged panels to see that they are functioning

manually to observe the contact alignment and to make

properly. Check mounting of devices and see that all

sure all mechanical parts move freely without binding or

electrical connections are tight.

excessive friction.

Check mechanical indicating devices and

b. The breakers are furnished with a drawout

interlocks.

mechanism which facilitates the inserting and with-

drawing of the breaker from its enclosure. It provides a

c. Check that all bus mounting bolts and splice

suitable means of forcing the breaker through each part

connection bolts are tight.

of the inserting and withdrawal operations. The drawout

mechanism is equipped with a drawout trip interlock

d. Wipe and vacuum clean the busses and

which prevents a racking operation from being

supports.

performed when the breaker is closed. To withdraw a

breaker perform the following steps.

e. Inspect all main cable connections for signs of

overheating. and tighten all connections.

(1) Trip the breaker (push trip button) to release

the positive racking interlock.

f. Check that all 120 volt wiring connections are

tight and intact.

(2) Lifting the racking handle (view E fig. 3- 10)

as far as it will go. (This operation will re- engage the

g. Check the ground bus connections and

trip interlock to hold the breaker trip- free for the

mounting bolts for tightness and clean ground bus.

remainder of the withdrawal racking operation.

h. Check to see that all anchor bolts and other

(3) Reset the handle to its lowered position and

structural bolts are tight.

lift it again. This operation must be performed 5 times

to completely disengage the racking cams (view A) from

i. Thoroughly clean interior of compartments. Use

their racking pins in the compartment. After the fifth

a vacuum cleaner and clean rags only. Do not use

lifting stroke (view I) let the handle drop to its connected

steel wool or oxide papers. Blowing with compressed air

position, (View G).

is not recommended.

(4) Pull the breaker out of its compartment until

j. Clean and inspect all painted surfaces and

the test position stop (view C) engages to hold the

retouch where necessary.

breaker in "test position".

k. Clean air filters as described in preceding

(5) Depress the test position stop handle (view

paragraph 3-9 k.

D) and pull the breaker out of its compartment as far as

WARNING

the drawout tray will travel.

Before inspection or any maintenance work

is done be sure the breaker is in the open

position. All electrical power both primary

3-16