General Description; Figure - Megger OTS 60PB Guide De L'utilisateur

General Description

The OTS 60PB is a 0 – 60 kV, battery powered portable dielectric strength oil test set. Its size and weight
make it suitable for on-site assessment of insulating oil quality. The dielectric strength test it performs is an
important deciding factor in knowing whether to retain or replace the oil. Breakdown voltage is measured,
averaged and displayed under the control of built-in programme sequences. Go/no-go testing is available.
The OTS 60PB is self contained in an ever-ready carry bag complete with its accessories; four vessels with
lids, a mains powered battery charger, a 12 V vehicle lead set and a gap gauge for electrode spacing.
Spherical electrodes of 12.7mm diameter are fitted as standard with options for mushroom or cylindrical
electrodes.
The instrument is housed within a metal case which forms an equipotential enclosure for the high and low
voltage circuits. An access door allows loading of the oil sample to be tested and is safety interlocked with
two forced break switches to BS 5304.
The action of pulling down the access door to the horizontal position raises the test electrodes and stirrer
to allow, easy, slide in loading of the filled oil vessel.
The oil vessels are transparent and heat resistant to 180 °C. An optional close fitting lid is available to
prevent contaminants from entering the vessel after cleaning and filling. See 'Accessories'.
The working surfaces in the oil testing area are all easily wiped clean from oil spills or contamination.
The OTS 60PB is fully portable with its own rechargeable battery built-in. The display carries a reminder
to top up the battery charge every six months. The nominal running time for continuous testing is 12 hours
which means the set can be used for many weeks without recharging in normal intermittent use.
The high voltage testing electrodes are of the type and dimensions found in most national specifications.
Adjustment of the electrode gap and cleaning the electrodes is simple and convenient. Alternative
electrode shapes needed for some national specifications are easily available and fitted.
Where the specification requires the oil sample to be stirred a small plastic paddle is rotated in the oil to
effectively remove carbon produced by the discharge at oil breakdown.
Two methods of oil breakdown detection are used and are sensitive enough to remove the need to
manually watch for transient sparkover as mentioned in some specifications.
The control panel has an on/off button and three softkey function buttons for all test selections. A rear
switch disconnects the battery for storage periods over six months.
Choice of language and choice of national and user proof tests as well as pass/fail de-skilled tests are all
selected and started from a user friendly menu on the l.c.d. display. Reminders are included to fit the
vessel, use the appropriate electrodes and set the necessary gap.
The instrument automatically shuts down around 25 minutes after completion of a test sequence in order
to maximise battery life. The last results may be recovered from the non-volatile memory after this
shutdown.
At the end of each automatic test the individual test results from the sequence are averaged, and the
standard deviation is calculated, and displayed. The individual breakdown values may be reviewed if
required.
OTS 60PB follows the oil testing sequences described in many national and other specifications among
which are: British BS 148, BS 5730a (automatic proof testing), BS 5874; International IEC 156, American
ASTM D877 ASTM D1816, German VDE 0370, French NFC 27, Spanish UNE 21, Italian CEI 10-1,
Russian Γ OCT 6581, South African SABS 555, Australian AS 1767 and Institute of Petroleum IP 295.
Two types of withstand (proof) testing of an oil sample are available. The principle with these tests is to
subject the oil sample to a specified voltage for a defined length of time (1 minute) to see if it will withstand
that voltage. In one of the tests the voltage is removed after a minute, in the other test, the voltage
continues to rise after the minute until breakdown or the maximum value is reached. Withstand (proof) tests
can be set up to the user's own requirements, and then repeatedly called up to quickly test oil under known
fixed conditions.
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