Vacuum Interrupter Integrity Test; Contact Erosion And Wipe - Eaton DHP VR + Series Instruction Book

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DHP-VR
+
VR-Series Replacement Circuit Breaker

6.3 VACUUM INTERRUPTER INTEGRITY TEST

Vacuum interrupters used in Type VR-Series + circuit breakers are
highly reliable interrupting components. Satisfactory performance
of these devices is dependent upon the integrity of the vacuum in
the interrupter and the internal dielectric strength. Both of these
parameters can be readily checked by a one minute ac high potential
test. (See Table 6.1 for appropriate test voltage.) During this test, the
following warnings must be observed:
m WARNING
APPLYING ABNORMALLY HIGH VOLTAGE ACROSS A PAIR OF CONTACTS
IN VACUUM MAY PRODUCE X-RADIATION. THE RADIATION MAY
INCREASE WITH THE INCREASE IN VOLTAGE AND/OR DECREASE IN
CONTACT SPACING. X-RADIATION PRODUCED DURING THIS TEST
WITH RECOMMENDED VOLTAGE AND NORMAL CONTACT SPACING
IS EXTREMELY LOW AND WELL BELOW MAXIMUM PERMITTED BY
STANDARDS. HOWEVER, AS A PRECAUTIONARY MEASURE AGAINST
POSSIBILITY OF APPLICATION OF HIGHER THAN RECOMMENDED VOLTAGE
AND/OR BELOW NORMAL CONTACT SPACING, IT IS RECOMMENDED THAT
ALL OPERATING PERSONNEL STAND AT LEAST ONE METER AWAY IN
FRONT OF THE CIRCUIT BREAKER.
m WARNING
DC HI-POTENTIAL TESTS ARE NOT RECOMMENDED BY EATON. DO NOT
APPLY DC AT ANY LEVEL TO VR-SERIES + POWER CIRCUIT BREAKERS
With the circuit breaker open and securely sitting on the floor,
connect all top/front primary studs (bars) together and the high
potential machine lead. Connect all bottom/rear studs together and
the high potential return lead. Do not ground them to the circuit
breaker frame. Start the machine at zero potential, increase to
appropriate test voltage and maintain for one minute.
Successful withstand indicates that all interrupters have satisfactory
vacuum level. If there is a breakdown, the defective interrupter or
interrupters should be identified by an individual test and replaced
before placing the circuit breaker in service.
After the high potential is removed, discharge any electrical charge
that may be retained, particularly from the center shield of vacuum
interrupters. To avoid any ambiguity in the ac high potential test due
to leakage or displacement (capacitive) current, the test unit should
have sufficient volt-ampere capacity. It is recommended that the
equipment be capable of delivering 25 milliamperes for one minute.
The current delivery capability of 25 mA ac applies when all three
vacuum interrupters are tested in parallel. If individual vacuum
interrupters are tested, current capability may be one third of this
value.
Tablt 6.1. Vacuum Inttrrupttr Inttgrity Ttst Voltagt
Circuit Breaker Rated
Maximum Voltage
Up to and including 15.0 kV

6.4 CONTACT EROSION AND WIPE

Since the contacts are contained inside the interrupter, they remain
clean and require no maintenance. However, during high current
interruptions, or high numbers of operations, it is possible for
a minimal amount of erosion on the contact surfaces. It is also
possible for further compaction of the conductor electrodes that has
been known to reduce the amount of contact wipe. The VR-Series +
vacuum interrupter assembly incorporates both the original vacuum
interrupter erosion indicator and the contact-spring wipe into one
all-encompassing indicator. The adequacy of the remaining contact
erosion and wipe can easily be determined by observing the vacuum
interrupter side of the operating rod assembly on a closed circuit
breaker. The procedure to determine the adequacy of the "T" cutout
on the vacuum interrupter assembly is depicted in Figures 6.1 and
6.2. Some configurations may require the use of a small mirror and
32 Instruction Book
Vacuum Interrupter Integrity Test Voltage
ac 60Hz
27 kV
IB182917EN September 2018 www.eaton.com
flashlight to clearly see the "T" cutout. As long as any part of the
"T" cutout is visible on each pole unit, the contact surfaces and
spring pressure are adequate for the circuit breaker to interrupt
its full rated nameplate short circuit and carry continuous current
without over-heating. If the wipe is inadequate (no part of the "T"
cutout is visible) then the vacuum interrupter assembly must be
replaced. Field adjustment is not possible.
m WARNING
FAILURE TO REPLACE A VACUUM INTERRUPTER ASSEMBLY WHEN THE
"T" CUTOUT IS NOT VISIBLE WILL CAUSE THE CIRCUIT BREAKER TO FAIL
TO INTERRUPT AND THEREBY CAUSE PROPERTY DAMAGE OR PERSONAL
INJURY.
Figurt 6.1. Tht Arrow Shows Tht "T" Contact Wipt Indicator -
(If tht "T" or any portion of its visiblt as shown with tht circuit
brtaktr clostd, tht wipt is satisfactory)(Stt ntxt figurt for
graphic of all possibilitits)
Figurt 6.2. Wipt Indication Proctdurt
(Ptrformtd Only With Circuit Brtaktr Clostd)
Blut Contact Springs
Any part of "T" Cutout Visible - "Wipe" Satisfactory
"T" Cutout Not Visible - "Wipe" Unsatisfactory