Basler BE1-11g Instruction Manual page 136

124
Parameter Description
Tapn Restraint winding
MVA MVA base
kVn kV base for CT input n
CTRn CT ratio for CT input n
Phase compensation
COMPn adjustment factor for
CT input n
The input currents can be tap adjusted up to a spread ratio of 10:1. If the ratio between TAP1 and TAP2
is greater than ten, it will be necessary to adjust the CT ratios to bring the tap factors closer together.
When the auto-tap calculation feature is used, the BE1-11g will give an error message if the spread ratio
is greater than ten.
If one of the calculated taps is outside the acceptable range (2 to 20 for 5 ampere units or 0.4 to 4 for 1
ampere units), the auto-tap calculation feature will select the nearest acceptable tap and calculate the
other tap (two at a time) so that the correct spread ratio is maintained. If the user is manually calculating
the taps, the same adjustment should be made.
BESTCOMSPlus is used to provide auto tap calculation by filling in the appropriate fields on the
Transformer Setup screen and pressing the calculate button or manual tap values can be entered.
Operational Settings
The settings for restrained minimum pickup and unrestrained trip are set in multiples of tap. If the ideal
taps calculated by Equation 21 fell within the acceptable range, the sensitivity settings will be in Per Unit
on the MVA Base used in the equation. For example, a 100 MVA, 115 kV transformer has a full load
(1 per unit) current of 500 amperes. A pickup setting of 10 times tap for the unrestrained output pickup
(URO) element is equivalent to 5,000 primary amperes of differential current.
If the taps had to be adjusted upwards or downwards to fit within the acceptable range, the sensitivity
settings for these protective elements should be adjusted as well. Equation 22 gives the adjustment
factor. The definitions for the variables in Equation 22 are the same as those for Equation 21. For
example, the ideal taps (TAPn
They had to be adjusted upwards so that the actual taps (TAPn
0.8. It is desired that the minimum pickup of the restrained element be 0.35 per unit on the circuit base.
The actual setting should be 0.35 ∗ 0.8 = 0.28 to achieve the same sensitivity.
The pickup settings in Times Tap can be related to primary amps by Equation 23. Minpu is the minimum
pickup setting in Times Tap. The definitions for the remaining variables in Equation 23 are the same as
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those for Equation 21.
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Equation 22. Tab Adjustment Equation
% of Maximum - The maximum of the compensated input currents is used. For example, the restraint
current for phase A would be
% of Average - The average of the compensated input currents is used. For example, the restraint
current for phase A would be given by Equation 24.
Equation 24. Calculate Restraint Current for Phase A, % of Average
Phase Current Differential (87) Protection
Table 44. MVA and kVn Base Parameters
The BE1-11g has 2 restraint windings (2 taps).
Full load MVA or top rating of the protected equipment.
L-L Voltage in kV for each CT input circuit.
Actual ratio not effective ratio.
√3 if CTs are connected in Delta (CTcon = DAB or DAC).
1 in all other cases.
See the Configuration chapter.
) were calculated using Equation 22 and Equation 23 to be 1.6 and 5.0.
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Explanation
) are 2.0 and 6.25. Per Equation 22, X =
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Equation 23. Calculate Primary Amps
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where x = 2 for two current inputs.
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BE1-11g