Insulation; Insulation Integrity Check; Primary Circuit Resistance Check; Mechanism Check - Eaton VCP-W Series Instructions For Installation/Operation/Maintenance/Servicing

Instructions for installation,
operation, and maintenance of type
VCP-W vacuum circuit breakers

6.6 Insulation

Type VCP-W circuit breaker insulation maintenance primarily consists
of keeping all insulating surfaces clean. This can be done by wiping
off all insulating surfaces with a dry lint free cloth or dry paper towel.
In case there is any tightly adhering dirt that will not come off by
wiping, it can be removed with mild solvent or distilled water. Be
sure that the surfaces are dry before placing the circuit breaker in
service. If a solvent is required to cut dirt, use Stoddard's Solvent
Eaton 55812CA or commercial equivalent. Secondary control wiring
also requires inspection for insulation damage.

6.7 Insulation integrity check

Primary circuit:
The integrity of primary insulation may be checked by the 60 Hz AC
high potential test. The test voltage depends upon the maximum
rated voltage of the breaker. For the breaker elements rated 4.76 kV,
8.25 kV, 15 kV, and 27 kV, the test voltages are 15 kV, 27 kV, 27 kV,
and 45 kV RMS respectively. Conduct the test as follows.
Close the breaker. Connect the high potential lead of the test
machine to one of the poles of the breaker. Connect the remaining
poles and breaker frame to ground. Start the machine with output
potential at zero and increase to the test voltage. Maintain the test
volt-age for one minute. Repeat for the remaining poles. Successful
withstand indicates satisfactory insulation strength of the primary
circuit.
If a DC high potential machine is used, make certain that the peak
voltage does not exceed the peak of the corresponding AC RMS test
voltage.
Secondary circuit:
Isolate the motor by pulling apart the two insulated quick discon-
necting terminals in the two motor leads provided for this purpose,
or remove the two motor wires from the ring tongue terminals
(Figure 5). Connect all points of the secondary disconnect pins with
shooting wire. Connect this wire to the high potential lead of the
test machine. Ground the circuit breaker frame. Starting with zero,
increase the voltage to 1125 Vac RMS, 60 Hz. Maintain the voltage
for one minute. Successful withstand indicates satisfactory insula-
tion strength of the secondary control circuit. Remove the shooting
wire and reconnect motor leads.

6.8 Primary circuit resistance check

Since the main contacts are inside the vacuum chamber, they
remain clean and require no maintenance at any time. Unlike many
typical circuit breaker designs, VCP-W breakers do not have sliding
contacts at the moving stem either. Instead they use a highly reli-
able and unique flexible clamp design that eliminates the need for
lubrication and inspection for wear.
If desired, the DC resistance of the primary circuit may be measured
as follows:
Close the circuit breaker, pass at least 100 amps DC current
•
through the circuit breaker. With a low resistance instrument,
measure resistance across the studs on the circuit breaker side of
the disconnects for each pole.
The resistance should not exceed the values shown in Table 25.

Table 25. Typical resistance measurements.

Rated continuous current
(amperes)
1200
2000
3000
Resistance
(microohms)
60
40
20
Instruction Booklet IB131006EN

6.9 Mechanism check

Make a careful visual inspection of the mechanism for any loose
parts such as bolts, nuts, pins, and rings. Check for excessive wear
or damage to the circuit breaker components. Operate the circuit
breaker several times manually and electrically. Check the closing
and opening times to verify that they are in accordance with the
limits in Table 22.
6.9.1 CloSure™ test
Introduction
The CloSure test is a simple yet extremely effective means to deter-
mine and monitor the ability of the mechanism to close the breaker
contacts fully. It provides a quantitative measure of the extra
energy available in terms of over travel in inches to close the breaker
contacts to their full extent. It maybe used periodically to monitor
the health of the mechanism.
At times, circuit breakers are called upon to operate mechanism
operated cell (MOC) switches that place extra load upon the closing
mechanism of the circuit breaker. If this load is excessive, it can
prevent the circuit breaker from closing fully. In such a case, it is
important to determine that the circuit breaker will close fully. The
CloSure test provides this assurance.
General information
The CloSure test can be per-formed on the VCP-W, VCP-WR, VCPW-
ND, DHP-VR, W-VACR, and W-VAC lines of vacuum circuit breakers.
Refer to Table 26 a for list of circuit breakers. If the CloSure travel
obtained is as specified, the mechanism performance is satisfactory.
If the CloSure travel does not conform as shown in Figure 36, con-
tact Eaton for further information (see Step 13).
m WARNING
DO NOT ATTEMPT TO INSTALL OR PERFORM MAINTENANCE OR TESTS ON
THE EQUIPMENT WHILE IT IS ENERGIZED. NEVER PUT YOUR HANDS NEAR
THE MECHANISM WHEN THE CIRCUIT BREAKER IS IN THE CHARGED OR
CLOSED POSITION. DEATH OR SEVERE PERSONAL INJURY CAN RESULT
FROM CONTACT WITH ENERGIZED EQUIPMENT. ALWAYS VERIFY THAT NO
VOLTAGE IS PRESENT BEFORE PROCEEDING WITH THE TASK AND ALWAYS
FOLLOW GENERALLY ACCEPTED SAFETY PROCEDURES.

6.10 Megger and power factor testing

Both the megger and power factor type testing of high voltage
insulation are not recognized by IEEE as a design, production, or
conformance test for determining product acceptance during initial
commissioning. If an end user wishes to use these tests for trend-
ing purposes, then they should record the initial readings during
commissioning along with temperature and humidity during the
testing. The trend of the test results should be tracked over the life
of the product and any abnormalities should be investigated.
Safety precautions
Read and understand these instructions before attempting any main-
tenance, repair, or testing on the breaker. The user is cautioned to
observe all recommendations, warnings, and cautions relating to the
safety of personnel and equipment.
The recommendations and information contained herein are based
on Eaton experience and judgment, but should not be considered to
be all-inclusive or covering every application or circumstance which
may arise. If further information is required, you should consult
Eaton.
Effective March 2019
EATON www.eaton.com
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