ABB Relion 670 Series Applications Manual page 508

Section 17
Monitoring
Settings for transformer withstand capability calculation
Four different protection curves are given in the IEEE C57.109.1993 standard for different
categories of transformer which are covered by IEEE C57.12.00-1993 standard. These curves are
based on the historical evolution of the short circuit withstand requirements and these should be
applicable to transformers built beginning in the early 1970s.
According to IEEE C57.109.1993 standard, single phase transformers above 10 MVA and three
phase transformers above 30 MVA come under category IV transformers. The recommended
protection curve for category IV transformer is given in
a protection curve for all faults, frequent and in-frequent. The curve is dependents upon the
transformer short circuit impedance for fault currents above 50% of the maximum possible and it
leads to worst case mechanical duty with maximum fault current for 2s. The damage intensity
from through faults depends on the current magnitude, fault duration, and the total number of
fault occurrences. Refer to
corresponding to the given transformer.
Table 65: Transformer nameplate data
Parameter
Frequency
Rated Power
Voltage ratio
Winding 1 rated current
Winding 2 rated current
Winding 3 rated current
Tap changer
Connection Type YNyn0d1
Cooling
% Impedance
According to the IEEE standard and
calculated with respect to transformer % impedance 12. In this case,
on the maximum allowable fault current 800 % of rated current for 2s duration. Also, if the
transformer manufacturer indicates that 10 such through faults can be withstand over the life
time of the transformer, then the cumulative
Table 66: PTRSTHR (51TF) setting parameters
Setting parameter
W1 I pickup
W2 I pickup
W3 I pickup
t_MinTripDelay
Table continues on next page
502
For transformers built prior to the early 1970s, consult the manufacturer for short
circuit withstand capabilities as a precaution.
Table 65 for the through fault monitoring function settings values
Figure
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Figure 222. This curve should be applied as
Value
50 Hz
500 MVA / 500 MVA / 20 MVA
415 kV / 230 kV / 20 kV
696 A
1255 A
577 A
±9; 1.67% of 230 kV
YNyn0d1
ONAF
12 @ Base 500 MVA
222, the given transformer withstand capability can be
2
I t limits can be set accordingly.
Select value
350 % IBaseW1
350 % IBaseW2
350 % IBaseW3
0.2 s
1MRK 511 401-UUS F
GUID-DC24F8F5-C65A-4C6D-A892-F5605CAAA49A v1
2
I t limits are calculated based
Bay control REC670
Application manual