Electrical Close And Trip Check ( Control Power Required); Checks Of The Spring Charging Motor ( 8 8); Vacuum Interrupters; Vacuum Integrity Check ( U Sing Mechanical Test) (Figure 18) - Siemens 3AH Series Instructions Manual

Maintenance

Electrical Close and Trip Check ( Control Power Required)

A check of the circuit breaker control circu its shall be
performed . This check is made with the circuit breaker
energ ized by control power either from the switchgear or an
external control power source.
1. Once the circuit breaker springs are charged, move the
switchgear Close/Trip switch to the Close position. Verify
by both the sound of the circuit breaker closing and by
the main contact status indicator that th e circuit breaker
contacts are closed.
2. As soon as the circuit breaker has closed, the automatic
spring charging process is repeated.
3. After a satisfactory close operation is verified, move the
switchgear Close/Tri p switch to the Tri p position. Verify
by both the sound of the circuit breaker o pening and by
the maih contact status indicator that the circuit breaker
contacts are open.
4. After a satisfactory open operation is verified, h old the
circuit breaker manual Trip button and apply and main­
tain an electrical close signal. The circuit breaker should
close, immediately trip, the close spring should charge,
and the circuit breaker should not attempt to close.
Completion of these checks demonstrates satisfactory
operation of auxiliary switches, internal relays a n d open a n d
close coils.
Checks of the Spring Charging Motor
No additional checks of the spring charging motor are neces­
sary.

Vacuum Interrupters

The l ife expectancy of vacuum interru pters is a function of
the n umber of interruptions a n d magnitude of current inter­
17).
rupted (Table 3 and Figure
They must also be replaced before certain amount of
mech a n ical operations (Table 2) or wh en the contacts have
been eroded beyond a l l owed limits. Vacuum interrupter
replacement proce d u res a re detailed in the following main­
tenance instructions.
The vacu um interrupter contact l ife curves F
fered as a guide to life expectancy.
Vacuum Integrity Check
( using MechanicaiTest) ( Figure
Before putting the circuit breaker into service, or if a vacuum
interrupter is suspected of leaki n g as a result of mechanica l
damage, check t h e vacu u m either mechan ically as described
in this section or alternatively electrically using a high poten­
tial test set as described in the next section.
Open and isolate the circuit breaker and detach the insulat­
ing coupler (48) from lever (48.6) (Figure
The atmospheric pressure will force the moving contact of a
hermetically sealed vacu u m interrupter into the " Closed" po­
sition, causing lever (48.6) to move into the position shown
18.
in Figure
(88)
a re of­
u e 17
ig
r
18)
18).
A vacuum interrupter may be assumed to be intact if it
shows the following cha racteristics:
An appreciable closing force has to be overcome when lever
(48. 6) is moved to the "Open" position by h a n d ( Figure
When th e lever is released, it must automatically return to
the "Closed" position with an audible soun d as the contacts
touch.
After checking the vacuum, reconnect the lever (48.6) to the
insulati ng coupler (48) ( Figure
High-Potentia l Tests
The next series of tests (Vacuum Integrity Test a n d Insulation
Tests) involve use of high voltage test equipment. The circuit
breaker u n der test should be inside a suitable test barrier
equipped with warning lights.
Vacuum Integrity Check ( using Dielectric Test)
A high potentia l test is used to verify the vacuum integrity
of the circuit breaker. The test is conducted on the circ u it
breaker with its primary contacts in the Open position.
Hazardous voltages used in high potential
tests.
Will cause severe personal injury and death.
Follow safe procedures, exclude u n n ecessary
personnel and use safety barriers. Keep away
from the circuit breaker during application of
test voltages.
Disconnect the plug j u m per from between the
circuit breaker and switch gear before conduct-
ing high pote ntial tests.
After test completion, grou nd both ends and
the middle portion of the vac u u m i nterrupter
to dissipate any static charges.
A
Vacuum interrupters may emit X-ray radiation.
Can cause personal injury.
Keep personnel more tha n six (6) feet away fro
a circuit breaker under test.

High Potential Test Voltages

The voltages for h i g h potential tests are shown in Table 4.
Table 4. High PotentiaiTest Voltages
Max AC rms
Equipment kV
Rating
1 4kV
4.76kV
8.25kV 27kV
1 5kV 27kV
38kV 60kV
18).
18).
A DANGER
WARNING
Max DC Avg
20kV
38kV
38kV
85kV
25