Measuring The Protection Level Of Overvoltage Protection Devices (Varistors) - Unitest Telaris 0751 Instruction Manual

Measuring the Protection Level of Overvoltage Protection Devices (varistors)

6.5 Measuring the Protection Level of
Overvoltage Protection Devices (varistors)
6.5.1 General Information for Measuring
the Protection Level
The protection level or the response voltage of over-
voltage protection devices can be measured using
the TELARIS 0751 (Cat. No. 9091).
This is a method to check and measure overvoltage
protection devices at the UUT mains input, which
have generated a measurement result too low dur-
ing insulation measurement.
The measurement is performed using a DC
voltage, to obtain a overvoltage protection de-
vices response. The DC value displayed during
the measurement corresponds to the actually
measured DC voltage.
The AC voltage value may be displayed during
the measurement using the key "Display" (17).
This value corresponds to the AC voltage value
to which the checked overvoltage protection
devices may be connected.
When calculating the maximum AC voltage, a safe-
ty factor of approx. 14 % will be considered, result-
ing into the following formula: UAC = UDC/1,6.
This measurement may only be performed on
UUTs which are not connected to live voltage!
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6.5.2 Measuring the Protection Level
Carrying out measurement:
Connect the UNITEST TELARIS 0751 via the
mains plug (1) to a functional and correct wired
and grounded mains socket.
Turn the 'Measurement function" selection
switch (15) to position VProt level".
When dealing with UUTs at which the overvolt-
age protection devices are connected between
L and N, connect the phase (L) of the mains
input to the red "L/N" socket (4) and the neu-
tral conductor (N) to the blue socket (5), please
refer to Figure 6.12.
When dealing with UUTs with the overvoltage
protection devices between L towards PE or N
towards PE, connect the blue socket (5) with
the PE and the red socket (4) to L or N of the
UUT, please refer to Figure 6.13.
If the overvoltage protection devices is in-
stalled after the mains switch, you must switch
on the UUT.
Press the key "Start" (9). The unit symbol
which is blinking on the display is an indication
for the active measurement procedure.
Read the measurement value from the LC dis-
play (6). The appliance displays the DC voltage
value of the response voltage.
The key "Display" (17) is used to display the AC
voltage value during the active measurement.
The measurement results can be saved by
pressing the key "Store" (10). For references
regarding the saving of measurement values,
please refer to section 7.1 and 7.2.