D2837-12
02-26-03
H
2
H
1
H
3
X
2
X
1
X
0
X
3
I
CD
I
C
=I
CD
-I
AD
I
c
=-I
cy
I
cy
I
b
=-I
by
I
by
I
a
=-I
ay
I
ay
I
BD
I
B
=I
BD
-I
CD
I
AD
I
A
=I
AD
-I
BD
X
0
B
C
A
H
3
H
2
H
1
X
1
X
2
X
3
I
Differential
I
a
I
A
I
a
lags I
A
by 180°+30°=210°
I
b
I
c
I
a
I
BD
I
CD
I
AD
-I
BD
I
A
=I
AD
-I
BD
Illustration A
Illustration B
Illustration C
Ib=Low side, phase B line current
I
BD
=Phase B, delta winding current
I
A
=High side, phase A line current
Ia=Low side, phase A line current
I
B
=High side, phase B line current
IC=High side, phase C line current
I
AD
=Phase A, delta winding current
I
CD
=Phase C, delta winding current
Ic=Low side, phase C line current
Ia
Y
=Phase A, wye winding current
Ib
Y
=Phase B, wye winding current
Ic
Y
=Phase C, wye winding current
Figure 1-4. Delta/Wye Transformer Circuits
BE1-CDS240 Solution
The input currents must be combined to mimic the way they are combined in the protected power
transformer so that the currents presented to the differential protection are made up of the same
components. Traditionally, this has been done by special connection of the CTs. Figure 1-5 shows the
transformer from Figure 1-4 with the CTs connected. The wye-side CTs can be connected in delta such
that the differential protection is summing IA with Ia-Ib. The resulting two currents being seen by the
differential relay are now made up of the same components but exactly 180 out of phase with each other.
They will always sum to zero (after tap adjust for magnitude mismatch) under all conditions of balance or
unbalance except when there is a fault inside the zone of protection.
9365200990 Rev F
BE1-CDS240 General Information
1-11
Summary of Contents for BE1-CDS240
Page 2: ......
Page 8: ...vi BE1 CDS240 Introduction 9365200990 Rev F This page intentionally left blank ...
Page 38: ...1 28 BE1 CDS240 General Information 9365200990 Rev F This page intentionally left blank ...
Page 40: ...ii BE1 CDS240 Quick Start 9365200990 Rev F This page intentionally left blank ...
Page 152: ...ii BE1 CDS240 Metering 9365200990 Rev F This page intentionally left blank ...
Page 226: ...iv BE1 CDS240 Application 9365200990 Rev F This page intentionally left blank ...
Page 286: ...ii BE1 CDS240 Security 9365200990 Rev F This page intentionally left blank ...
Page 290: ...9 4 BE1 CDS240 Security 9365200990 Rev F This page intentionally left blank ...
Page 292: ...ii BE1 CDS240 Human Machine Interface 9365200990 Rev F This page intentionally left blank ...
Page 306: ...10 14 BE1 CDS240 Human Machine Interface 9365200990 Rev F This page intentionally left blank ...
Page 308: ...ii BE1 CDS240 ASCII Command Interface 9365200990 Rev F This page intentionally left blank ...
Page 342: ...11 34 BE1 CDS240 ASCII Command Interface 9365200990 Rev F This page intentionally left blank ...
Page 349: ...Figure 12 5 Horizontal Rack Mount Front View 9365200990 Rev F BE1 CDS240 Installation 12 5 ...
Page 361: ...Figure 12 17 Typical DC Connection Diagrams 9365200990 Rev F BE1 CDS240 Installation 12 17 ...
Page 372: ...12 28 BE1 CDS240 Installation 9365200990 Rev F This page intentionally left blank ...
Page 468: ...13 92 BE1 CDS240 Testing and Maintenance 9365200990 Rev F This page intentionally left blank ...
Page 512: ...14 42 BE1 CDS240 BESTCOMS Software 9365200990 Rev F This page intentionally left blank ...
Page 544: ...ii BE1 CDS240 Terminal Communication 9365200990 Rev F This page intentionally left blank ...
Page 550: ...ii BE1 CDS240 Settings Calculations 9365200990 Rev F This page intentionally left blank ...
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