Seg HighTECH MRG3 - Indication of Measuring Values; Measuring Indication for Mains Decoupling; Storage of Min.;Max. Values

Manual MRG3 SEG Electronics GmbH
DOK-TD-MRG3, Rev. D 55
5.10 Indication of measuring values
5.10.1 Measuring indication for mains decoupling
In normal operation the following measuring values for mains decoupling can be displayed:
In star connection:
 Voltage in phase L1 LED: U + L1
 Voltage in phase L2 LED: U + L2
 Voltage in phase L3 LED: U + L3
or, if delta connection was parameterized
 Voltage in phase L1/L2 LED: U + L1 + L2
 Voltage in phase L2/L3 LED: U + L2 + L3
 Voltage in phase L3/L1 LED: U + L3 + L1
 Frequency LED f
 Lowest frequency, measured before last reset LED: f + min
 Highest frequency, measured before last reset LED: f + max
 Vector surge in phase L1(L1/L2) LED: /df + L1
 Vector surge in phase L2(L2/L3) LED: /df + L2
 Vector surge in phase L3(L3/L1) LED: /df + L3
 Lowest vector surge, measured before last reset LED: /df + min
or, if df/dt-function was activated
 Frequency gradient LED: /df
 Lowest frequency gradient, measured before last reset LED: /df + min
 Highest frequency gradient, measured before last reset LED: /df + max
5.10.2 Storage of min./max. values
The MRG3 offers each one minimum and one maximum storage values measured for frequency,
vector surge and frequency gradient. These min./max. values are mainly used to appraise the net-
work system’s quality. Always the highest and lowest values of each cycle are measured and
stored until the next reset (refer to chapter “Reset” 5.10.9).
Min.-/max.- frequency measuring:
The MRG3 ascertains the actual frequency from each cycle of the system voltage. These measur-
ing values are entered into the min./max. storage. The latest entered min./max. values replace the
previously stored values. Dependent on the adjustment of dt and tripping delay, it is possible that
the stored min./max. values are considerably higher than the tripping threshold without causing a
trip. The reason for this is the storage of instantaneous values.
Min./Max. measuring of the frequency gradient
The procedure described above applies also to the storage of min./max. values of df/dt measure-
ment. Since each instantaneous df/dt value is stored, high values can occur which, however, do not
cause any tripping.
This can for instance happen during switching procedures where high positive and negative df/dt
values occur, but do not cause any tripping due to the special measuring method.
Min./max. measuring of the vector surge
The procedure described above applies also to storage of min./max. values of vector surge meas-
uring. Since each instantaneous  value is stored, also here high values are possible which,
however, do not cause any tripping.
These min./max. measurements are of great advantage for long-time analysis of the grid quality.