Sanwa mg5000, Инструкция по эксплуатации, Страница: 15 / 28

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5-5 DAR/PI Measurement
This function is used to check the increase over time of the insulation
resistance after application of voltage to the object measured.
It automatically calculates and displays the DAR (Dielectric
Absorption Ratio), which is one of the insulation judgment criteria,
as well as the PI (Polarization Index).
As the increase over time of the leak current of an insulator is
affected by absorption of moisture, it is important for diagnosing
insulation of cables. The time periods used to obtain the results
are different between the DAR and PI.
5-5-1 DAR : Dielectric Absorption Ratio
The DAR refers to the ratio between the resistance values at 60
seconds and 30 or 15 seconds after the start of measurement. It
is expressed with the following formula.
DAR = (Resistance at 60 sec. after voltage application)/
(Resistance at 30 or 15 sec. after voltage application)
Changing between the 30 and 15 sec. settings
* The default period set at the factory is 15 sec.
1) With the power/function switch set to OFF, press and hold the
DISPLAY button while turn the power/function switch to ON.
The display shows “DAR” and “00:30” or “00:15” in the timer
area at the bottom left of the panel.
2) Each press of the DISPLAY button alternates “00:30” and
“00:15”.
3) The time period displayed at the moment the power switch is
set to OFF again is saved.
The current setting can be checked with the operation in step 1).
5-5-2 PI : Polarization Index
The PI refers to the ratio between the resistance values at 10 minutes
and 1 minute after the start of measurement. It is expressed with the
following formula.
PI = (Resistance at 10 min. after voltage application)/(Resistance
at 1 min. after voltage application)