Basler BE1-CDS240, Instruction Manual, Page: 556 / 580

NOTE:

3 FACTOR
When calculating the tap adjust settings for the BE1-87T, the

3 COMPn factor had to be included
rega ing the CTs in delta or by using rdless of whether phase compensation was done by connect
internal delta compensation. The BE1-CDS240 relay does not magnify the secondary current when
performing the phase compensation internally. (For more information, see the
Internal
Compensation Chart under the SG-CT command in Section 3.) The COMP factor is 1 unless the
CTs are connected in Delta. The BE1-CDS240 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.
Step 2. Calculate ideal tap values. Since all CTs are wye connected, COMP1, COMP2 and COMP3 are 1
ors being reset, it would be safer to use the system nominal values
per Table D-2. Ideally, the actual transformer voltage ratings at the in-use tap position are used
for the KV Base. However, if the taps in the protected transformer could be changed without the
BE1-CDS240 tap adjust fact
and account for the additional mismatch in the slope setting.
D-6 BE1-CDS240 Settings Calculations 9365200990 Rev F
39 4
160 230 3
1 1000 280
1 P .
* *
* *
 
TA 69 . 4
300 * 115 * 3
1 * 1000 * 280
2
 
TAP
6 14
1 1000 280
3 TAP
.
* *
 
800 8 13 3
* . *
Step 3.
types
Step 4. Calculate to
TAP3
and
TAP1
to
TAP3
. If
greater ratios to bring the tap ratios to less than 10
winding relative to the main winding,
this typically will the lower rated winding to reduce the CT's normal
Step 5 If tap ratios are less than 10, but one of the taps is beyond the range of 2 to 20, the taps may be
s a whole linearly in a direction that maintains the original tap ratios but brings all taps
to within acceptable limits. For instance, if
TAP3
had been calculated to some value above 20,
sensitivity of the relay. In non-numerical relays
.g., Basler Electric BE1-87T), the minpu was fixed at a typical value of 0.35 of the relay tap. In the BE1-
DS240 relay, the user can choose lower or higher values to optimize the protection in each particular
pplication. Selecting a lower minpu setting will tend to raise the slope setting needed to maintain a given
haracteristic. (For more information, see the Calculate
lope later in this section.) Conversely, it is sometimes necessary to accommodate unmonitored loads in
the differential zone. In that case, the minpu setting may be higher. A setting of 0.25 per unit of
transfor
If the calculated TAP1, TAP2 and TAP3 are in range (2.00 - 20.0 for 5 ampere sensing input
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.
spread ratio. Determine the ratio of
TAP1
to
TAP2
,
TAP2
than 10:1 (or conversely, 1:10), adjust the CT
(or greater than 0.1). In transformers with a lower MVA rated
mean raising the CT ratio of
current under full load conditions to a fairly low level.
adjusted a
then reset TAP3 to 20 and reset TAP1 and TAP2 to a lower value using the equation:
Calculate Minpu
The minimum pickup restraint setting (minpu) adjusts the






 






 
3 TAP Old
20
2 TAP Old 2 TAP New
3 TAP Old
20
1 TAP Old 1 TAP New
(e
C
a
margin at the knee-point of the differential tripping c
S
mer full load (
FA
) rating (i,e., top MVA) is recommended for typical installations whe
ored load needs to be considered. This value is well above the magnetizing current and pr
argin at the knee point of the slope characteristic. If un
re no
unmonit ovides
a safe m monitored loads such as station service or
small capacitor banks are connected in the differential zone, the minpu must be increased by the
magnitude of the unmonitored current in multiples of tap.