Checking The Correct Polarity Of The Strings; Checking Of Leakage To Ground Of The Photovoltaic Generator - ABB UNO-DM-TL-PLUS-US Product Manual

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hecking the correct polarity of the strings
Using a voltmeter, check that the voltage of each string has the correct
polarity and falls within the input voltage limits of the inverter (see techni-
cal data).
Polarity inversion can cause serious damage.
If the open circuit voltage of the string is near the maximum value ac-
cepted by the inverter, consider that low ambient temperatures cause
an increase in the string voltage (different according to the photovoltaic
module used). In this case it is necessary to carry out a check of the
sizing of the system and/or a check on the connections of the modules
of the system (e.g.: number of modules in series higher than the design
number).
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hecking of leakage to ground of the photovoltaic generator
Measure the voltage present between the positive and negative pole of
each string with respect to ground.
If a voltage is measured between an input pole and ground, it may be that
there is a low insulation resistance of the photovoltaic generator and the
installer will have to carry out a check to solve the problem.
Do not connect the strings if a leakage to ground has been detected, as the inverter might
not connect to the grid.
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5 - Installation