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, Power System Inputs,
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.
CTRn
COMPn
*
KV1,2,3,4
*
3
*
1000
*
MVA
TAP1,2,3,4
Equation 4-1. Calculate Tap Adjust Factors
Table 4-5. MVA and KVn Base Parameters
Parameter Description
Explanation
Tapn
Restraint winding
CDS240 has up to 4 restraint windings (4 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
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
Tap CT Input 3
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 4
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
The input currents can be tap adjusted up to a spread ratio of 10:1. If the ratio between TAP1, and TAP2,
3, or 4 is greater than ten, it will be necessary to adjust the CT ratios to bring the tap factors closer
9365200990 Rev F
BE1-CDS240 Protection and Control
4-13
Summary of Contents for BE1-CDS240
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