Trip time
Fault resistance
R
Trip
R
Alarm
IEC11000002-1-en.vsd
IEC11000002 V1 EN
Figure 131: Trip time characteristic as function of fault resistance
A third high level step for the detection of excitation system earth faults on the AC side
of the excitation rectifier is available. This step uses the network frequency (50 or 60
Hz) for the evaluation. If an earth fault occurs at the AC side of the excitation system
rectifier, there is a fundamental frequency component at the measured voltage and
current injection points.
The third high level step is not applicable if mixed signals are used, that is when the
REX060 is used for both rotor and stator earth fault protection and only two, instead
of four, analog inputs on the IED are used.
7.8.10 Technical data
Table 132: ROTIPHIZ technical data
Function
Range or value Accuracy
Fault resistance sensitivity Can be reached at
steady state operating
condition of the
machine
500 kΩ
Typically 20 - 50 kΩ
Injection frequency (75.000 - 250.000) Hz ±0.1 Hz
Trip limit of fault resistance (100 - 100000)Ω 5% of 1 kΩ at R
f
≤ 1 kΩ
5% of set value at 1 kΩ < R
f
≤ 20 kΩ
10% of set value at R
f
> 20 kΩ
Table continues on next page
Section 7 1MRK502052-UEN B
Impedance protection
292
Technical manual
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