ABB RELION 670 Series Technical Manual page 592

Section 8
Current protection
8.18 Generator rotor overload protection, GRPTTR (49R)
8.18.1 Identification
Function description
Generator rotor overload protection
8.18.2 Functionality
The generator overload function, GRPTTR (49R) is used to protect the rotor winding against
excessive temperature as a result of overcurrents. The functions operating characteristic is
designed in accordance with the American standard IEEE-C50.13.
If internal generator components exceed its design temperature limit, damage can be the result.
Damage to generator insulation can range from minor loss of life to complete failure, depending
on the severity and duration of the temperature excursion. Excess temperature can also cause
mechanical damage due to thermal expansion. Rotor components such as bars and end rings are
vulnerable to this damage. Since temperature increases with current, it is logical to apply
overcurrent elements with inverse time characteristics.
For its operation the function either measures the true RMS current of the excitation transformer
or calculates the DC current in the rotor winding. The rotor winding DC current can be calculated
from the AC currents measured on either high voltage side (HV) or low voltage side (LV) side of the
excitation transformer. For the HV side measurement ratings of the excitation transformer shall
be given. The use of the DC current is default (i.e. recommended) measurement for generators
with static excitation system. When the DC current is used, the function can provide a DC current
ripple alarm, due to possible problem with the static excitation equipment. The rotor DC current
can be also sent to the plant supervisory system via communication channel or displayed on the
IED built-in HMI.
The function can also detect undercurrent condition in the rotor winding which indicates either
under-excitation or loss of excitation condition of the generator.
The function is designed to work on 50/60 Hz systems.
586
IEC 61850 IEC 60617
identification identification
GRPTTR
SYMBOL-MM V1 EN-US
1MRK 502 066-UUS B
GUID-2EF7010A-F585-4C53-879F-F7908CF58DE9 v1
GUID-2FB631FB-E6F7-4FAC-A350-BEB2867C7E9E v2
ANSI/IEEE C37.2
device number
49R
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GUID-E3AE6200-DB8D-4C49-A740-09366A333B4F v4
Technical manual