Basler BE1-CDS220, Instruction Manual

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BE1-CDS220 Protection and Control 4-13
Tap Compensation Settings for Phase Differential
As discussed in Section 1, General Information, Differential Protection Application Considerations, the
measured currents must be tap adjusted to eliminate magnitude mismatch prior to being used by the 87
phase differential protection function. The tap adjust factors can be manually calculated per Equation 4-1.
Or, the user can enter the MVA and KV base parameters (Table 4-5) and the relay will calculate the tap
adjust factors using CTR and Compensation Factor parameters from the current measurement input
function settings. See Section 3, Input and Output Functions, Input Current, for more details on these
settings. For a transformer application, the mismatch will be at a minimum if the actual transformer
voltage ratings are used taking the no-load tap changer into consideration. If the transformer has a load
tap changer, the voltage rating at the middle of the adjustment range should be used. This is generally at
neutral. Table 4-6 lists the tap compensation settings for Phase Differential.
Equation 4-1. Calculate Tap Adjust Factors
Table 4-5. MVA and KVn Base Parameters
Parameter Description Explanation
TAPn Restraint winding CDS220 has 2 restraint windings (2 taps).
MVA MVA base Full load MVA or top rating of the protected equipment.
KVn KV base for CT input n L-L Voltage in KV for each CT input circuit.
CTRn CT ratio for CT input n Actual ratio not effective ratio.
COMPn
Phase compensation
adjustment factor for
CT input n
√
3 if CTs are connected in Delta (CTcon = DAB or DAC).
1 in all other cases.
See Section 3, Input and Output Functions.
Table 4-6. Tap Compensation Settings for Phase Differential
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 relay will give an error message if the spread ratio is
greater than ten.
If one of the calculated taps is outside the acceptable range (2.0 to 20 for 5 ampere units or 0.4 to 4.0 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.
Range
Setting
5A 1A
Increment
Unit of
Measure
Default
Auto-tap MVA base
Manual = auto-
tap disabled
0.5 to 9999
Manual = auto-
tap disabled
0.5 to 9999
0.1
N/A
MVA
Manual
Tap CT Input 1 or
Auto-tap KV base
2.0 to 20.0 or
0.01 to 1000.0
0.40 to 4.00 or
0.01 to 1000
0.01 for 2.00 to 9.99
0.1 for 10.0 to 20.0 or
0.01
Sec. amps or
Primary KV
2
Tap CT Input 2 or
Auto-tap KV base
2.0 to 20.0 or
0.01 to 1000.0
0.40 to 4.00 or
0.01 to 1000
0.01 for 2.00 to 9.99
0.1 for 10.0 to 20.0 or
0.01
Sec. amps or
Primary KV
2
CTRn * KV1,2 * 3
COMPn * 1000 * MVA
TAP1,2
=