has
c
a high peak that is non-sinusoidal. The relay extracts the fundamental component of the operate
urrent for use by the unrestrained element to greatly reduce its sensitivity to this non-sinusoidal inrush
current. In addition, the high initial peak generally decays quickly to a lower value. The slight inverseness
f the unrestraint tripping char cteristic (refer to Section 1,
General Inform tion
) provides additional
ecurity from unrestrained trippin on inrush with a sensitive setting.
o
a
a
s
g
Since the
tap values are based upon the forced cooled rating
and adjusted if necessary by the factor
X calculated in
Calculate Minpu,
Step 1, Equation D-8, the pickup can be calculated:
D-8
BE1-CDS240 Settings Calculations
9365200990 Rev F
cooled
forced
MVA
X
URO
*
*
6
cooled
self
MVA
2
.
3
280
150
*
1
*
6
URO
6
.
3
URO
This
(3.2 is rounded up to 4.0; rounding down should not be done in this application) is the
URO
value
inrush. The next step will determine the value required to avoid
ipping for the maximum external ult under worst case CT saturation.
tep 1. Calculate the maximum external fault (IE) in multiples of tap. Use these two equations:
For wye connected CT’s
For delta connected CT’s (See Setting Note 2)
minimum setting to avoid tripping during
tr
fa
Check Maximum External Fault Saturation Effects
S
Tap
Fault
Maximum
IE
Tap
phase
Fault
Maximum
IE
3
*
3
HIGH
LOW TERTIARY
8
.
9
39
.
4
160
16900
IE
3
.
6
69
.
4
300
8900
1
.
2
64
.
14
800
24600
IE
IE
Step 2. The transient monitor function provides security from tripping for external through faults by
doubling the u
s detected. Calculate the
unrestrained pic
greater than 70% of the
nrestrained unit pickup setting when saturation i
kup such that
2 times the unrestrained pickup is
maximum external through fault
in times tap. This calculation assumes that the CTs carrying
the maximum fault saturate severely, yielding only 30% of the expected ratio current. This leaves
70% of the fault current as false differential current.
43
.
3
2
8
.
9
*
7
.
0
URO
21
.
2
2
3
.
6
*
7
.
0
URO
74
.
0
2
1
.
2
*
7
.
0
URO
As previously noted when examining the CT performance and Saturation Factor
SF
, a more complete
analysis of the unrestrained pickup setting would include applying these calculations to every CT that
sees current during the external fault. For brevity, this check is not done in these calculations.
Step 3. Select the unrestrained pickup setting. Choose the larger of the unrestrained pickup values
calculated in the above equations on this page and round it up to the next integ
is
results in a setting of
URO = 4 times tap
for this example.
Step 4. Convert pickup setting to primary amperes.
, convert the unrestrained pickup sensitivity to high side and low side primary amperes.
er value. Th
As a reality check
The equation to do so is similar to the last equation on page D-7. Ignore energization from the tertiary as
it will never be done in actual practice.
A
Ipri
810
,
2
160
*
39
.
4
*
4
@ 230 kV
A
Ipri
69
.
5
*
4
628
,
5
1
300
*
@ 115 kV
1
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 ...
Page 578: ...D 28 BE1 CDS240 Settings Calculations 9365200990 Rev F This page intentionally left blank ...
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