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The module calculates the start duration value
START_DUR, which indicates the
percentage ratio of the start time and the set operating time. The value is available
in the monitored data view.
Timer 2
Once activated, the alarm timer is activated. The time characteristics are according
to DT. When the alarm timer reaches the value set by
Alarm delay time, the
ALARM
output is activated. If the fault disappears before the module generates an
ALARM
signal, the reset timer is activated. If the reset timer reaches the value set by
Reset
delay time, the alarm timer resets. The activation of the
BLOCK
signal resets the
Timer 2 and deactivates the
ALARM
output.
4.1.12.6
Application
In order to prevent the generator shaft from getting electrically charged the
shaft is grounded. Different types of generators have different ways for shaft
grounding. With hydro-generators, the water acts as a grounding point, and with
turbogenerators the shaft can be grounded with a slip ring. However, the leakage
current can still occur if the bearing pedestal, which is isolated from the ground,
becomes grounded. This imposes shaft voltage on the oil-film of the bearing. The
current can break the insulation that the oil-film provides and thus it can cause
pitting and abrasion on the bearing face.
The measured shaft current is fed to the protection relay. The function compares
the current signal to the set alarm and operate levels. Operate time characteristics
are according to definite time.
Measurement device options
There are two different applicable shaft current measurement devices, the
Rogowski coil and the current transformer (CT). Both devices are installed around
the generator shaft. For both devices it is necessary to amplify the voltage signal.
The recommended measurement principles are depicted in
.
I
Resistance
Amplifier
Protection relay
CT
I>
Figure 250: Current transformer measurement arrangement
1MRS759142 F
Protection functions
REX640
Technical Manual
437
Содержание RELION REX640
Страница 1: ... RELION PROTECTION AND CONTROL REX640 Technical Manual ...
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Страница 3: ...Document ID 1MRS759142 Issued 2023 02 07 Revision F Copyright 2023 ABB All rights reserved ...
Страница 167: ...Figure 62 Signal outputs in power supply module 1MRS759142 F Basic functions REX640 Technical Manual 167 ...
Страница 184: ...Figure 84 mA channels working as mA outputs Basic functions 1MRS759142 F 184 REX640 Technical Manual ...
Страница 1868: ...Figure 989 ANSI extremely inverse time characteristics General function block features 1MRS759142 F 1868 REX640 Technical Manual ...
Страница 1869: ...Figure 990 ANSI very inverse time characteristics 1MRS759142 F General function block features REX640 Technical Manual 1869 ...
Страница 1870: ...Figure 991 ANSI normal inverse time characteristics General function block features 1MRS759142 F 1870 REX640 Technical Manual ...
Страница 1874: ...Figure 995 ANSI long time inverse time characteristics General function block features 1MRS759142 F 1874 REX640 Technical Manual ...
Страница 1875: ...Figure 996 IEC normal inverse time characteristics 1MRS759142 F General function block features REX640 Technical Manual 1875 ...
Страница 1876: ...Figure 997 IEC very inverse time characteristics General function block features 1MRS759142 F 1876 REX640 Technical Manual ...
Страница 1877: ...Figure 998 IEC inverse time characteristics 1MRS759142 F General function block features REX640 Technical Manual 1877 ...
Страница 1878: ...Figure 999 IEC extremely inverse time characteristics General function block features 1MRS759142 F 1878 REX640 Technical Manual ...
Страница 1882: ...Figure 1002 RI type inverse time characteristics General function block features 1MRS759142 F 1882 REX640 Technical Manual ...
Страница 1885: ...Figure 1004 UK rectifier inverse time characteristic 1MRS759142 F General function block features REX640 Technical Manual 1885 ...
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