Basler BE1-CDS220, Instruction Manual

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D-4 Settings Calculations BE1-CDS220
DETERMINE TAP SETTINGS
Calculate Ideal Taps
Step 1: Use Equations D-1 and D-2 to calculate ideal taps. Parameters for these equations are in
Table D-2. For more information refer to Section 4, Protection and Control, 87-Phase
Differential Function.
1 1 3
1 1000
1
CTR KV
COMP MVA
TAP
∗ ∗
∗ ∗
=
Equation D-1
2 2 3
2 1000
2
CTR KV
COMP MVA
TAP
∗ ∗
∗ ∗
=
Equation D-2
Table D-2. Parameters for Equations D-1 and D-2
Parameter Description Explanation
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 CT’s are connected in Delta (ctcon = DAB or DAC). 1
in all other cases. See Section 3, Input and Output
Functions, Table 3-2 and Figure 3-3.
Step 2: Calculate ideal tap values. Use the top (e.g. FA) MVA rating of the transformer when making
the calculations. Since both CTs are wye connected, COMP1 and COMP2 are 1 per Table D-
2. If the actual power transformer ratings at the no load tap position are used for the KV
Base, the tap adjust factor calculation can completely cancel this source of mismatch.
However, if the no load taps in the protected transformer could be changed without the BE1-
CDS220 tap adjust factors being reset, it would be safer to use the system nominal values
and account for the additional mismatch in the slope setting.
79 . 2
60 69 3
1 1000 20
1
=
∗ ∗
∗ ∗
=
TAP
Equation D-3
79 . 5
160 47 . 12 3
1 1000 20
2
=
∗ ∗
∗ ∗
=
TAP
Equation D-4
Step 3: If the calculated TAP1 and TAP2 are in range, (2.00 - 20.0 for 5 ampere sensing input types
or 0.40 - 4.00 for 1 ampere sensing input types) proceed to Calculate Minpu. If they are not in
range, proceed with Step 4.
Step 4: Calculate spread ratio. Determine the ratio of TAP1 to TAP2. If greater than 10:1, adjust the
CT ratios to bring them closer together.
NOTE
When calculating the tap adjust settings for the BE1-87T, the
√
3 COMPn factor
had to be included regardless of whether phase compensation was done by
connecting the CTs in delta or by using internal delta compensation. The BE1-
CDS220 relay does not magnify the secondary current when performing the
phase compensation internally. The COMP factor is 1 unless the CTs are
connected in Delta. The BE1-CDS220 automatically takes the
√
3 factor into
account prior to the tap adjustment when internal phase compensation is applied
to a set of CT input currents.