Megger TTR20, Инструкция по эксплуатации

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M
AVTMTTR20 Rev 4 Dec 2015
2
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External optional printer records test data.
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Three automatically selected excitation test voltages: 8 V, 1.5 V, and 0.5 V.
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Testing to ANSI standards.
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Leads marked to ANSI standards.
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Large, easy-to-read LCD shows alphanumeric data
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Meets the requirements of both the European EMC and Low Voltage Directives
(CE mark).
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Trouble-free operation in switchyards under electrostatic and magnetic
interference conditions.
Electrical Theory and Practice
How the TTR20 Works
The TTR20 test set provides the excitation voltage to the input of the transformer.
It accurately measures both the H-side and X-side voltages to calculate turns
ratio. The TTR also measures phase displacement (polarity) between primary
and secondary windings of a transformer, and transformer excitation current.
Transformer Turns Ratio
Transformer Turns Ratio is the ratio of the number of turns in the high voltage
winding to that in the low voltage winding. Transformer ratio can change due to
several factors, including physical damage from faults, deteriorated insulation,
contamination and shipping damage.
A Transformer Turns Ratio Test Set such as the TTR20 can directly measure the
turns ratio of single-phase transformers as well as three-phase transformers.
Deviations in these measurements will quickly indicate problems in transformer
windings and in the magnetic core circuits. If a transformer ratio deviates more
than 0.5 percent from the rated voltage ratio, it may not operate reliably. To
measure small ratio changes such as this, the accuracy of a Megger TTR20 is
needed.
Excitation Current
The TTR20 is capable of measuring exciting current by applying voltage to one of
the transformer’s windings. An accurate measurement of exciting current can
provide information about the condition of a transformer’s core. Unwanted
circulating currents, unintentional grounds or even an incipient short circuit can
affect the exciting current and indicate a problem.
Transformer Polarity
Polarity of a distribution transformer becomes of interest in order to determine its
proper connection within a power network. The Megger TTR20 will identify
normal (in phase) and reverse polarity of the single-phase transformers
.