Protective Elements
Commissioning: Overvoltage Protection [59]
Object to be tested
Test of the overvoltage protection elements, 3 x single-phase and 1 x three-phase (for each element)
Through testing the overvoltage protection stages, it can also be ensured
that the wiring from the switchboard input terminals is correct. Wiring
errors at the voltage measuring inputs might result in:
False tripping of the directional current protection
Example: Device suddenly trips in reverse direction but it
does not trip in forward direction.
Wrong or no power factor indication
Errors with regard to power directions etc.
Necessary means
3-phase AC voltage source
Timer for measuring of the tripping time
Voltmeter
Procedure
(3 x single-phase, 1 x three-phase, for each element
)
Testing the threshold values
For testing the threshold value
s and fallback values, the test
voltage has to be increased until the relay is
activated. When comparing the displayed values with those of the voltmeter, the deviation must be within the per-
missible tolerances.
Testing the trip delay
For testing the trip delay, a timer is to be connected to the contact of the associated trip relay.
The timer is started when the limiting value of the tripping voltage is exceeded and it is stopped when the relay trips.
Testing the fallback ratio
Reduce the measuring quantity to less than (e.g.) 97% of the trip value. The relay must only fall back at 97% of the
trip value at the earliest.
Successful test result
The measured threshold values, trip delays and fallback ratios comply with those specified in the adjustment list.
Permissible deviations/tolerances can be taken from the Technical Data.
Commissioning: Undervoltage Protection [27]
This test can be carried out similar to the test for overvoltage protection (by using the related undervoltage values).
Please consider the following deviations:
For testing the threshold values the test voltage has to be decreased until the relay is activated.
For detection of the fallback value, the measuring quantity has to be increased so to achieve more than
(e.g.) 103% of the trip value. At 103% of the trip value the relay is to fall back at the earliest.
390
MRU4
DOK-HB-MRU4-2E
