90% NORTH LINK EMI PREDICTION REPORT
F. Ross Holmstrom, Ph.D.
September 2012
1.
INTRODUCTION AND SUMMARY
This report includes updates incorporated from the 60% North Link EMI Predication
Report. All 60% review comments have been reviewed, incorporated or responded too
accordingly. Reference 5 is the complete list of review comments and responses.
There have been no other modifications to the 60% North Link EMI Predication Report.
The 60% report brought up-to-date the analysis of predicted B-field levels at critical UW
labs due to North Link and U-Link train operations through the UW campus. It updates
calculated B-field values predicted to be achieved by implementation of mitigation
design concepts covered in Ref. 1 released in 2006; by implementation of specific
signal and power system designs presented in Ref. 2; and by adoption of additional
design implementations and changes since the 2008 release of Ref. 2 that are
discussed in this report. The critical UW labs comprise two groups. The UW has
established Requested Threshold B-field levels at the eleven labs in Group 1. Meeting
the Group 1 threshold levels is mandatory. The UW also has established Requested
Threshold B-field levels for the four labs in Group 2. Meeting the Group 2 Requested
Threshold B-field levels is not mandatory; however, exceeding the ST Baseline
predicted B-field levels at the Group 2 labs will require negotiations between ST and
UW. The Group 1 and 2 labs are:
Group 1 Labs
Bagley Hall
Chemistry Bldg.
Electrical Engineering/Computer Science
Physics/Astronomy
Johnson Hall
CHDD
Health Sciences Imaging Center
Surgery Pavilion
Fisheries Center
Marine Sciences
Group 2 Labs
Fluke Hall
Mechanical Engineering & Annex
Roberts Hall
Wilcox Hall
UW Requested
Threshold (mG)
0.1
0.1
5.0
0.5
5.0
0.3
5.0
1.0
0.1
1.0
UW Requested
Threshold (mG)
0.3
0.2
0.1
0.1
ST Baseline
Prediction (mG)
0.26
1.63
0.32
0.85
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 2
A number of changes have been made in the location of the North Link right-of-way
(ROW) in the period since April 2006, the last change taking place since 2008. Since
2008 the planned ROW has been moved westward in the vicinity of Roberts and Wilcox
Halls, the Mechanical Engineering Building & Annex and Fluke Hall. This move has
decreased predicted B-fields at Fluke Hall. However, at Roberts, Wilcox and the ME
Bldg. & Annex, where the 2006 predicted B-fields levels already were above those
requested by UW, the presently predicted B-field levels are still higher. Sound Transit
will have to discuss these increases with the UW. Sound Transit is currently evaluating
the tunnel shielding concept suggested by the UW. As far as we know, the proposed
application of shielding technology to a segmented tunnel liner has not been attempted
before.
Changes have been made as well in some of the computational routines used for
calculating propulsion and perturbation B-fields. Greater use has been made of three
dimensional models of the ROW that allow for curved, rising and falling models of the
ROW. In addition to these refinements in the model analysis, we also revisited whether
or not adding a mid-campus TPSS or otherwise reducing distances between TPSS to
the propulsion system would reduce EMI at the sensitive receivers. The answer is no,
the substations spacing has already been studied and are determined at optimal
locations. We also considered whether gains were possible in lowering magnetic fields
by reducing the riser spacing in the mitigation design. Again, this had already been
review at great detail and no additional gains were realized.
This report examines B-field levels in depth at four Group 1 buildings: Bagley Hall,
Chemistry Bldg., Surgery Pavilion (also known as the Ambulatory Care Facility) and the
Fisheries Center. B-field levels also are examined in depth at Fluke Hall on the Group 2
list. It has been found that because of their locations and their Requested Thresholds,
if the UW Requested Thresholds are met at these labs then they will be met at all other
Group 1 labs as well. In this sense these five labs are salient.
At all five salient labs and at all other Group 1 labs as well, the new calculations show
that B-field levels are predicted to be below the UW Requested Thresholds by a
sufficient margin.
90% North Link EMI Prediction Report – Holmstrom – September 2012
2.
pg. 3
MAGNETIC FIELD SOURCES
At the Group 1 & 2 UW lab locations magnetic fields (B-fields) were calculated
separately for currents in the following B-field sources shown in map of the North Link
ROW from Capitol Hill Station to Roosevelt Station in Figure 1:
Source No. 1 – Rail and OCS currents and geomagnetic perturbations due to trains
operating in the B-field mitigated region stretching from Stationing NB 1189+90, 419
meters (1375 ft) south of the center of the crossover just south of UW Station, to NB
1253+30 near the corner of NE 42nd St. and University Way, with current supplied by
the UW TPSS,
Source No. 2 – Rail and OCS currents in the non-B-field mitigated region from NB
1253+30 to just south of NE 45th St. at the northern end of Brooklyn Station (the
“Brooklyn Stub”); with current supplied by the Brooklyn TPSS,
Source No. 3 – Rail and OCS currents between Brooklyn and Roosevelt Stations,
Source No. 4 – Rail and OCS currents between the southern end of B-field
mitigation at NB 1189+90 and Capitol Hill Station, i.e., South of Montlake (SOM),
currents provided by the Montlake rectifier bank at the UW TPSS and the Capitol Hill
and/or Pine Street TPSS,
Source No. 5 – Propulsion currents in the cables and rectifiers at the UW TPSS, and
Source No. 6 – Rail and OCS currents in the crossover and adjacent tracks when
the crossover is occupied by a train crossing over.
For increased accuracy and decreased reliance on approximations, new calculations of
propulsion current B-fields (Bprop) were performed for the sections of curved ROW in
the South of Montlake and B-field mitigated regions using physical circuit models that
describe the shape of the curving, rising and falling ROW in three dimensions.
Proximity of the Group 1 & 2 UW labs to the above sources can be visualized by
referring to Figure 2.1 on pg. 5 of Ref. 1.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 4
Figure 1. The North Link right-of-way from Capitol Hill Station to Roosevelt Station showing
the sources of B-fields analyzed in this report.
90% North Link EMI Prediction Report – Holmstrom – September 2012
3.
pg. 5
MAGNETIC FIELDS FROM SOURCE No. 1 – MITIGATED REGION & SOURCE
No. 2 – BROOKLYN STUB
Table 1 shows total B-field due to propulsion currents in OCS and rails in Source No. 1
– B-field mitigated region and Source No. 2 – Brooklyn Stub.
Table 1
B-field due to propulsion currents in OCS and rails in the
B-field mitigated region and the Brooklyn Stub.
Sources
SB Btot
1+2
(mG)
NB+SB
Btot (mG)
EMF
Site
NB ΔX
(m)
SB ΔX
NB Btot
ΔY (m)
(m)
(mG)
Bagley Hall
1
303.6
291.6
33.0
0.013
0.011
0.024
Chemistry Bldg.
2
305.3
293.3
34.4
0.012
0.010
0.022
EE/CS
3
100.5
88.5
32.6
0.146
0.093
0.239
Physics/Astronomy
4
378.3
366.3
8.4
0.012
0.012
0.024
Johnson Hall
6
216.1
204.1
22.7
0.027
0.021
0.047
Fluke Hall
7
113.0
125.0
26.9
0.100
0.041
0.141
ME Bldg.
11a
30.1
18.1
37.4
0.670
0.550
1.220
ME Annex
11c
22.0
10.0
36.8
0.824
0.665
1.489
Roberts Hall
12
76.9
64.9
33.7
0.215
0.159
0.374
Wilcox Hall
13
34.9
22.9
34.6
0.630
0.551
1.181
CHDD
8
237.4
225.4
19.0
0.010
0.011
0.021
Diagnostic Imaging
9
303.4
291.4
29.1
0.008
0.009
0.017
Surgery Pavilion* - 1st Fl.
10a
94.9
82.9
29.0
0.115
0.149
0.264
Surgery Pavilion* - Pking
10b
94.9
82.9
19.9
0.121
0.159
0.280
Fisheries Center (FIS)
14
386.0
374.0
16.7
0.004
0.004
0.008
Marine Sciences
15
673.0
661.0
11.7
0.025
0.006
0.031
EMF Sensitive Site
*Also called the Ambulatory Care Facility
Comparison of the B-field values above with those in Table 3.3 of the 2006 North Link
Hi-Lo Mitigation EMI Report [Ref. 1] shows that some Btot values have increased and
some have decreased. Increases in Btot values for Roberts, Wilcox, ME, ME Room 135
and the ME Annex are due to the movement to the west of the ROW in the vicinity of
these buildings. Westward movement of the ROW in that area also has caused the
Fluke Hall Btot value to decrease.
Other change in calculated Btot values from 2006 to present are due to what is
presumed to be better accuracy of the new curved-ROW model.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 6
Still other changes in predicted B-field levels are due to changes in the model of the
ROW that took place when the propulsion circuit design was completed. As shown in
Figure 2 in the 2006 model it was presumed that propulsion currents were applied to
Source No. 1 – the B-field mitigated region – at its southern end, and the current in each
track flowed in a single continuous loop that passed all the Group 1 & 2 UW labs and
extended clear to Brooklyn Station.
As shown in Ref. 2 the loop for each track has been cut into three loops. The
propulsion feed point for the mitigated region has been moved to the north-south
midpoint of the crossover just south of UW Station, and labs in the UW Medical Center
area are subjected to B-fields either from the short southern loop or from the southern
end of the main central loop, but not from both simultaneously.
Additionally, B-fields from the Brooklyn Stub are handled differently than in 2006 and
2008. In the 2006-2008 models, trains running past the northern end of B-field
mitigation clear up to the Brooklyn Station drew currents from the UW TPSS. In the
present model trains only draw current from the UW TPSS up to the beginning of the
stub. Trains in the Brooklyn Stub draw current from the Brooklyn TPSS. Assuming that
at most one train northbound and one train southbound operate between UW and
Brooklyn Stations, calculation of Bprop is made separately for currents in the mitigated
region and in the stub itself; then the larger of the two Bprop values is used. Only in the
case of Physics/Astronomy was Bprop from the Brooklyn Stub larger than Bprop from the
B-field mitigated region.
For this report an updated method of calculating Bptb at labs far from the ROW was
used. While measured Bptb values near a light rail train have been found to obey the
relation (Ref. 1)
Bptb = 2000/r
2.2
mG for r small.
It is known that at distances far away from a ferrous object of limited size, B ptb
3
decreases as 1/r with increasing distance r away from the object. Therefore for
distances greater than the approx. 110 meter (360 ft) train length the relation used was
3
Bptb = 85930/r mG for r ≥ 110 meters.
That fact was used to calculate Bptb values at distances from the ROW greater than the
110 meter (360 ft) train length, resulting in smaller calculated Bptb values for the labs at
a greater distance.
The two equations above yield the same value of Bptb = 0.065 mG at r = 110 meters.
90% North Link EMI Prediction Report – Holmstrom – September 2012
Figure 2.
pg. 7
Propulsion circuit design in 2006 and early 2012.
90% North Link EMI Prediction Report – Holmstrom – September 2012
4.
pg. 8
MAGNETIC FIELDS FROM SOURCE NO. 3 – THE BROOKLYN-TOROOSEVELT ROW
To calculate worst-case Bprop fields from the Brooklyn-to-Roosevelt segment of the
ROW it was assumed that one northbound and one southbound train each drew 2800 A
over the entire segment in the same direction, as might occur for instance if the
Brooklyn TPSS were out of service and two trains were accelerating out of Brooklyn
Station simultaneously, both drawing their current from the Roosevelt TPSS. This
configuration is shown in Figure 3. The resulting calculated Bprop values at the Group 1
& 2 UW labs are given in Table 2.
The XYZ coordinate system in Table 2 has its origin at the center of the crossover just
south of UW Station, at sea level. X is measured west, Z north, and Y up from that
point. For these calculations it was assumed that the rails were at a constant elevation
of Y = 33.5 meters (110 ft) from Brooklyn to Roosevelt.
The Bprop values in Table 2 are very close to those in Table 4.1 of Ref. 1. The slight
differences probably are due to the fact that the model used to calculate these new
values took account of the differences in elevation of the ROW and buildings.
90% North Link EMI Prediction Report – Holmstrom – September 2012
Figure 3.
pg. 9
Train configuration leading to greatest B-field contribution from
Source No. 3 – Brooklyn-to-Roosevelt.
90% North Link EMI Prediction Report – Holmstrom – September 2012
Table 2
pg. 10
B-field due to propulsion currents in OCS and rails in the
Brooklyn Station to Roosevelt Station portion of the ROW.
EMF
Site
X (m)
Y (m)
Z (m)
Source 3
NB+SB
Btot (mG)
Bagley Hall
1
360.0
35.7
564.0
0.024
Chemistry Bldg.
2
304.8
29.0
477.6
0.020
EE/CS
3
104.9
26.8
518.4
0.019
Physics/Astronomy
4
513.6
22.9
546.0
0.025
Johnson Hall
6
372.0
30.2
674.4
0.030
Fluke Hall
7
-36.0
23.8
729.6
0.022
ME Bldg.
11a
50.4
31.4
576.0
0.020
ME Annex
11c
41.0
31.4
571.2
0.019
Roberts Hall
12
70.3
26.5
362.4
0.015
Wilcox Hall
13
28.8
27.1
326.4
0.014
CHDD
8
230.4
7.3
-96.0
0.010
Diagnostic Imaging
9
295.2
19.8
106.8
0.012
Surgery Pavilion* - 1st Fl.
10a
88.8
18.9
-2.4
0.010
Surgery Pavilion* - Pking
10b
88.8
9.8
-2.4
0.010
Fisheries Center (FIS)
14
379.2
6.4
-21.6
0.011
Marine Sciences
15
666.0
1.4
78.4
0.013
EMF Sensitive Site
* Also known as the Ambulatory Care Facility
90% North Link EMI Prediction Report – Holmstrom – September 2012
5.
pg. 11
MAGNETIC FIELDS FROM SOURCE No. 4 – THE SOUTH-OF-MONTLAKE
ROW
Analysis of Bprop fields from the SOM ROW is more complicated than from the Brooklyn
to Roosevelt ROW because of its length, because of the cross bond located approx. 1/3
of the way from the southern end of B-field mitigation to the Capitol Hill Station, and
because of the long steep grade from the southern end of mitigation to Capitol Hill that
makes the occurrence of regenerative braking very likely. Details of the ROW in this
region are shown in Figure 4.
The single cross bond noted above adds complexity to the task of determining currents
in the rails between Montlake and Capitol Hill and their resulting B-field contributions. It
also causes rail current patterns that lead to slightly higher levels of B-field than would
occur if it were absent. However, its presence in the rail circuit is required to assure
sufficiently low values of train-to-substation rail resistance. Absent the requirements to
minimize B-field levels many more cross bonds would have been used between
Montlake and Capitol Hill. Because of the requirement to minimize B-field the number
of cross bonds was reduced to the barest minimum that the power considerations would
allow. Fortunately, the resulting rail circuit design with the single cross bond resulted in
prediction of acceptable B-field levels.
Because of its proximity to the southern limit of B-field mitigation and its 0.1 mG UW
spec B-field level the Fisheries Center is the test case for Bprop levels arising from this
section of ROW. If Bprop levels from SOM currents do not impact the Fisheries Center
too badly all other Group 1 & 2 labs will be safe as well.
It was assumed that trains could produce a maximum of 3500 A current in regeneration
and that a regenerating train could always find a receptive load. Regen current not
accepted by a train in the vicinity drawing current would then have to flow back through
both NB and SB OCSs to Capitol Hill.
It was assumed that a train under forward power could draw a maximum of 2800 A.
It was found that a single regenerating train heading northbound just south of the B-field
mitigated region and producing 3500 A would give rise to a 0.04 mG B-field at the
Fisheries Center. However, this level of regeneration would cause several hundred
volts of IR drop from the train to Capitol Hill, and unless the Capitol Hill TPSS were
heavily enough loaded to decrease its output voltage by several hundred volts the regen
train would exceed its maximum regen voltage limit.
One train accelerating while drawing 2800 A and one train in regen producing 2800 A
with the trains near each other in the north-south direction also produced approx. 0.04
mG B-field at Fisheries when they were in the vicinity of the cross bond, and they
produced slightly less B-field if they were located north or south of the cross bond.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 12
A single train accelerating southbound while drawing 2800 A produced a peak Fisheries
Center B-field of 0.03 mG when the train was near the cross bond and lower values
when north or south of that point.
If the assumption is made that the Montlake rectifier is off-line and two trains are
accelerating with each drawing 2800 A, with the southbound train just starting up the
northern side of Capitol Hill and the northbound train just north of the grade minimum
south of the B-field mitigated region, for instance maintaining its speed prior to braking
for UW Station, so that both trains are drawing their current from Capitol Hill, then the Bfield at the Fisheries Center is 0.073 mG. This 0.073 mG level is 0.033 mG or 83%
above the predicted worst-case level of 0.04 mG achieved with the Montlake rectifier
on-line, a fact that indicates the importance of maintaining it or a replacement in service
at all times to assure normal North Link operation. Operation of the University Station
TPSS will be conducted to assure presence of such a rectifier except under the most
extreme circumstances.
Capitol Hill and Pine Street rectifiers will never be off-line simultaneously except under
the most extreme circumstances. Therefore the Capitol Hill to Montlake tracks always
will be driven from both ends except in the most extreme circumstances, thus assuring
optimum B-field performance. When a train is operating between rectifiers it tends to
receive the greater current from the nearest rectifier, thus minimizing the length of the
current loop. Additionally, the current in the OCW-rail loop ahead of the train will flow
around the loop in opposite sense to current in the loop behind the train, causing the Bfields from the loops to partially cancel.
90% North Link EMI Prediction Report – Holmstrom – September 2012
Figure 4.
pg. 13
Current flow details in the South-of-Montlake region. As an example
a southbound train is shown accelerating up the northern side of
Capitol Hill while a regenerating northbound train descends.
Presence of cross bond leads to SB and NB rails all conducting
during any train move.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 14
It is assumed that with the Montlake rectifier on-line northbound trains having
descended Capitol Hill in regen or dynamic braking would only draw current on the
upgrade into UW Station through a very short current loop until they got to the B-field
mitigated region and any B-fields resulting from current flow in this short loop have been
neglected.
Table 3
B-field due to propulsion currents in OCS and rails in the
South of Montlake portion of the ROW.
EMF Sensitive Site
EMF
som X (m)
Site
Y (m)
som Z (m)
Source 4
NB+SB
Btot
(mG)
Bagley Hall
Chemistry Bldg.
1
2
318.0
262.8
35.7
29.0
983.0
896.6
0.008
0.010
EE/CS
Physics/Astronomy
3
4
62.9
471.6
26.8
22.9
937.4
965.0
0.010
0.008
Johnson Hall
Fluke Hall
6
7
330.0
-78.0
30.2
23.8
1093.4
1148.6
0.007
0.007
ME Bldg.
ME Annex
Roberts Hall
11a
11c
12
8.4
19-41
28.3
31.4
31.4
26.5
995.0
990.2
781.4
0.009
0.009
0.014
Wilcox Hall
CHDD
13
8
-13.2
188.4
27.1
7.3
745.4
323.0
0.015
0.064
Diagnostic Imaging
Surgery Pavilion* - 1st Floor
9
10a
253.2
46.8
19.8
18.9
525.8
416.6
0.026
0.048
Surgery Pavilion* - Pkng
Fisheries Center (FIS)
Marine Sciences
10b
14
15
46.8
337.2
624.2
9.8
6.4
1.4
416.6
397.4
497.4
0.048
0.040
0.018
*Also known as the Ambulatory Care Facility
The XYZ coordinate system used in the calculations for Table 3 has its origin displaced
42 meters (138 ft) west in the X-direction and 419 meters (1375 ft) south in the -Z
direction from the origin of coordinates used in Table 2.
Note that the SOM B-fields are greater at the CHDD and Surgery Pavilion than they are
at Fisheries. However, CHDD’s 0.3 mG UW spec B-field level is three times higher than
the 0.1 mG level at Fisheries, and the 1 mG level at Surgery Pavilion is ten times
higher. Therefore, if the B-field level at Fisheries is OK, the B-field levels at CHDD and
the Surgery Pavilion will be OK too.
90% North Link EMI Prediction Report – Holmstrom – September 2012
6.
pg. 15
MAGNETIC FIELDS FROM SOURCE No. 5 – PROPULSION CABLES AND
RECTIFIERS IN THE UW TPSS
The cables in the UW TPSS carrying DC propulsion current from the rectifiers to the
tracks are predicted to contribute significantly to B-field levels at nearby Group 1 & 2
UW labs. There are three rectifiers, and the cables immediately adjacent to and
connected to those rectifiers each will form large loops with areas estimated to be
2
2
between 12 and 18 m (130-195 ft ). The axis of each loop will be aimed almost
directly at the UW Medical School Surgery Pavilion some 95 meters (312 ft) away.
3
B-fields arising from a conducting loop fall off as 1/r with increasing distance r away
from the loop. Therefore, it is expected that the greatest effect of B-fields due to the
loops will be at the Surgery Pavilion since the other Group 1 & 2 UW labs are very
nearly three times as far away from the UW TPSS.
Much smaller loops are expected to arise from some but not all propulsion cable
groups. Cables from the Montlake rectifier to the tracks have been designed to produce
essentially zero B-field, with each positive feed cable placed between a pair of balanced
negative feed cables connected to the same track. In the case of cables running from
the UW NB and SB rectifiers to their respective tracks the small cable separations and
short lengths of runs leads to conducting loops with minimal areas compared to the big
loops. Additionally, the design calls for cables to be placed so that under maximum
load conditions B-fields from the cables will cancel. Because of these aspects of cable
layout design the B-fields arising from cables between the big loops and tracks have
been neglected.
Detailed calculations have been performed to estimate the anticipated overall B-field
levels at the Group 1 & 2 UW labs including fields generated by UW TPSS cables. The
results of these calculations predict that under the most extreme LRV traffic conditions,
anticipated total B-fields due to LRV operation will come up very close to – but will not
exceed – UW Requested Thresholds. However, under these traffic conditions the
previously predicted B-field margins will be nearly reduced to zero at the Surgery
Pavilion and at the Fisheries Center.
The UW TPSS will be equipped with three traction power rectifiers. The Montlake
rectifier will provide power to both NB and SB tracks extending from the S end of the Bfield mitigated region to Capitol Hill. The UW NB and SB rectifiers will power the NB
and SB tracks respectively from the S end to the N end of the B-field mitigated region.
The Montlake rectifier will furnish current through separate feeds to the NB and SB
Montlake tracks. The UW NB rectifier will furnish current through separate feeds to the
NB track north of and south of the section break located at the N-S midpoint of the
crossover. The UW SB rectifier will do the same for the SB track through the UW
campus.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 16
Predicted B-field levels were calculated for five operating conditions:

Normal University Link operation with 2-car trains - Maximum B-field generation
occurs when one train drawing 700 A max occupies the crossover, one 1400 A
max train is on the SB Montlake track and one 1400 A max train is on the NB
Montlake track.

Special Events University Link operation with 4-car trains - Three trains located
as above, each with corresponding currents doubled.

Normal North Link operation (4-car trains) - One NB and one SB Montlake train;
one NB and one SB UW train. Both UW trains are modeled as being powered by
the UW NB rectifier (with the largest loop) to simulate service with one rectifier
down. All trains draw 2800 A.

North Link Extreme Service A operation (4-car trains) - One NB and one SB
Montlake train. Two NB UW trains (one south and one north of station) both
powered by UW NB TPSS, and two SB UW trains (ditto) both powered by UW
SB TPSS. All trains draw 2800 A.

North Link Extreme Service B operation (4 car trains) - As immediately above
except all four UW trains are powered by UW NB TPSS with its max-sized loop.
Table 4 gives the total B-field values for the five cases listed above. Note that in all of
the columns in Table 4 the Btpss values are far larger at the Surgery Pavilion
(Ambulatory Care Facility) than at any other lab.
In assessing the impact of UW TPSS B-fields at specific labs what is important is how
much B-field margin exists at each lab from all other B-field sources and how much of
that margin is used up or exceeded when the TPSS B-fields are added. Also of
importance is the consideration of what large contributors to B-fields can be active at
the same time. For instance, the TPSS B-fields and the crossover B-fields yet to be
discussed are practically mutually exclusive B-field contributors. There cannot be a
great deal of traffic when a train is using the crossover, and when there is a great deal
of traffic the crossover will not be in use.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 17
Table 4. B-field contributions from UW TPSS cables for various
modes of University Link and North Link operation.
UW
Threshold
Level
B mG
University
Link 2-car
trains
Typical
Service
Btpss mG
Bagley Hall
0.1
0.000
0.001
0.001
0.002
0.002
Chemistry Bldg.
0.1
0.000
0.001
0.002
0.002
0.002
EE-CS
5.0
0.001
0.001
0.002
0.003
0.003
Physics-Astronomy
0.5
0.000
0.000
0.001
0.001
0.001
Johnson Hall
5.0
0.000
0.000
0.001
0.001
0.001
Fluke Hall
0.3
0.000
0.000
0.000
0.001
0.001
ME Bldg. & Annex
0.2
0.000
0.001
0.002
0.002
0.003
Roberts Hall
0.1
0.001
0.003
0.005
0.007
0.008
Wilcox Hall
0.1
0.002
0.004
0.007
0.011
0.012
CHDD
0.3
0.005
0.009
0.016
0.022
0.024
Diagnostic Imaging
5.0
0.003
0.006
0.010
0.014
0.015
Surgery Pavilion* - 1st fl.
1.0
0.091
0.182
0.293
0.422
0.443
Surgery Pavilion* - pkng
1.0
0.096
0.191
0.308
0.443
0.465
Fisheries Center
0.1
0.001
0.003
0.005
0.007
0.008
Marine Sciences
1.0
0.000
0.001
0.001
0.001
0.002
UW Lab
*Also called the Ambulatory Care Facility
University
North Link North Link North Link
Link 4-car
4-car trains 4-car trains 4-car trains
trains
Typical
Extreme
Extreme
Special
Service
Svc. A
Svc. B
Events
Btpss mG Btpss mG Btpss mG
Btpss mG
90% North Link EMI Prediction Report – Holmstrom – September 2012
7.
pg. 18
MAGNETIC FIELDS FROM SOURCE No. 6 – RAIL AND OCS CURRENTS
WHEN A TRAIN IS CROSSING OVER IN THE CROSSOVER
Table 5 gives B-fields arising at Group 1 & 2 UW labs when a train is crossing over from
one track to the other in the crossover located just south of UW Station. When a train is
crossing over its wheels, axles and car body provide shorting paths around the
insulated joints that normally electrically isolate the northbound and southbound rails,
creating large current loops that provide multiple paths for propulsion current. These
current loops are composed of rails and OCWs in the crossover.
Table 5
Magnetic fields at Group 1 & 2 UW labs caused
by trains in the crossover.
Labs
Bprop
Bptb
Bxover
EMF from train from train
total
site in Xover in Xover
(mG)
(mG)
(mG)
Bagley Hall
1
0.0008
0.0005
0.0013
Chem Bldg.
2
0.0007
0.0007
0.0014
EE/CS
3
0.0037
0.0010
0.0047
Physics/Astronomy
4
0.0001
0.0002
0.0003
Johnson Hall
6
0.0007
0.0003
0.0010
Fluke Hall
7
0.0012
0.0003
0.0015
ME Bldg. & Annex
11
0.0039
0.0009
0.0048
Roberts Hall
12
0.0124
0.0037
0.0161
Wilcox Hall
13
0.0140
0.0039
0.0179
CHDD
8
0.0275
0.0051
0.0326
Diagn Imaging
9
0.0150
0.0033
0.0183
Surgery Pavilion* - 1st floor
10a
0.5780
0.0914
0.6694
Surgery Pavilion* - Parking
10b
0.6468
0.0969
0.7437
Fisheries Center (FIS)
14
0.0095
0.0016
0.0111
Marine Sciences
15
0.0017
0.0003
0.002
*Also called the Ambulatory Care Facility
The Bxover values were calculated assuming that while the crossover was occupied by
a crossing train no other train would draw currents that would flow into or through the
crossover. Additionally it was assumed that a train crossing over would be restricted to
a maximum speed of 10 mph and therefore could draw at most 350 A per car or 1400
A for a 4-car train, half the normal maximum current.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 19
When occupied, currents in the crossover can flow in large loops. However, at
3
distances greater than loop cross sections the resulting B-fields fall off as 1/r as
distance r away from the loops increases. Therefore it is not surprising that the
crossover B-fields in Table 5 above are far greater at the nearby Ambulatory Care
Facility than at any other lab.
Recent calculations showed that there is very little difference in Btpss values whether or
not the gaps in the added crossover OCW sections were bridging or non-bridging.
Therefore bridging gaps can be used to avoid loss of current to pantographs of cars
crossing these gaps. OCS design has been updated by putting a jumper cable from
the powered adjacent OCS to the center part of the crossover which was designed
unpowered since 2008.
One key fact about B-fields due to the crossover is that when trains are crossing over it
can be expected that other train movements in the area will be greatly curtailed.
Therefore, in spite of the 0.74 mG of Bxover at the Surgery Pavilion there is little
likelihood of additional B-field from other sources pushing the total B-field there over
the 1 mG UW Requested Threshold.
90% North Link EMI Prediction Report – Holmstrom – September 2012
8.
pg. 20
ADDITIVE MAGNETIC FIELDS AT THE SALIENT LABS AND ALL LABS DUE
TO B-FIELDS FROM ALL SOURCES
Some of the Group 1 & 2 UW labs are on the front line of impact from transit-caused Bfields. If UW Requested Thresholds for transit-caused B-fields are met at these salient
labs, then with the exception of Wilcox and Roberts Halls and the ME Building and
Annex they will be met at all other sites. Wilcox and Roberts Halls and the ME Building
and Annex are so close to the ROW that their transit-caused B-fields surely will fall
above the UW Requested Thresholds.
The salient buildings are ones with low Requested Thresholds or proximity to major Bfield sources or both. These buildings and their Requested Thresholds are:

Bagley Hall (Group 1)
0.1 mG

Chemistry Bldg.(Group 1)
0.1 mG

Surgery Pavilion (Group 1)
1.0 mG

Fisheries Center (Group 1)
0.1 mG

Fluke Hall (Group 2)
0.3 mG
Bagley Hall (Group 1)
Bagley Hall is one of the three labs with a 0.1 mG Requested Threshold. It benefits
from its location relatively far from the ROW in general, the UW TPSS, the crossover
and the southern end of the B-field mitigated region. It served as one determinant in
placing the northern end of the B-field mitigated region in its presently chosen location.
Adding up the Bagley Hall B-field values in the right-hand column of Tables 1-5 yields:
Sources 1 & 2 – Mitig. region + Brooklyn stub
0.024 mG
Source 3 – Brooklyn-Roosevelt
0.024
Source 4 – South-of Montlake
0.008
Source 5 – UW TPSS propulsion currents
0.002
Source 6 – Crossover propulsion currents
0.001
Total
0.059 mG
The 0.059 mG total is well under the 0.1 mG UW Requested Threshold, and the
number would shrink to 0.058 mG by eliminating the crossover B-field whose
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 21
presence means that operational conditions would cause the other numbers to
shrink.
Chemistry Building (Group 1)
Adding up the same numbers for Chemistry as was done for Bagley Hall yields:
Sources 1 & 2 – Mitig. region + Brooklyn stub
0.022 mG
Source 3 – Brooklyn-Roosevelt
0.020
Source 4 – South-of Montlake
0.010
Source 5 – UW TPSS propulsion currents
0.002
Source 6 – Crossover propulsion currents
0.001
Total
0.055 mG
This total also is well under the 0.1 mG UW Requested Threshold, and would shrink to
0.054 mG without the crossover B-field component, repeating the argument used for
Bagley Hall.
Surgery Pavilion (Group 1) (Ambulatory Care Facility) – First Floor
For Surgery Pavilion-1st Floor B-fields we will have to recognize that if the crossover is
occupied then minimal other train operation will be taking place. It is conceivable that in
addition to the train in the crossover the UW TPSS might be powering one other
accelerating train, possibly going up Capitol Hill. There likely would be no other train
current delivered to the B-field mitigated or Brooklyn-to-Roosevelt regions. Therefore,
the maximum value of Btpss would be (1.5/4)x0.443 = 0.166 mG, the 0.443 figure
coming from the last column in Table 4. And the B-field contributions would add up as
follows:
Sources 1 & 2 – Mitig. region + Brooklyn stub
0.000 mG
Source 3 – Brooklyn-Roosevelt
0.000
Source 4 – South-of Montlake
0.048
Source 5 – UW TPSS propulsion currents
0.166
Source 6 – Crossover propulsion currents
0.669
Total
0.883 mG
This value is below the 1 mG UW spec B-field limit for the Surgery Pavilion – 1st Floor.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 22
Fisheries Center (Group 1)
Sources 1 & 2 – Mitig. region + Brooklyn stub
0.008 mG
Source 3 – Brooklyn-Roosevelt
0.011
Source 4 – South-of Montlake
0.040
Source 5 – UW TPSS propulsion currents
0.008
Source 6 – Crossover propulsion currents
0.011
Total
0.078 mG
This B-field level is below the 0.1 mG UW spec level, and it would decrease further if
the same arguments regarding crossover B-fields were made as for the Chemistry Bldg.
and Bagley Hall. Maintaining the 0.078 mG level requires that the Montlake tracks be
driven by a rectifier at the UW end to provide power to trains maintaining their speed
from the bottom of the grade under the Montlake Cut until they enter the B-field
mitigated region.
Fluke Hall (Group 2)
Fluke Hall benefits from the fact that the ROW has been moved farther away. And the
magnitude of calculated B-fields benefit from the adoption of a three-dimensional model
of the ROW that is believed to more accurately calculate propulsion B-fields at Fluke
Hall’s location outside of the curve of the ROW.
The B-field numbers at Fluke Hall are as follows:
Source 1 & 2 – Mitig. region + Brooklyn stub
0.141 mG
Source 3 – Brooklyn-Roosevelt
0.022
Source 4 – South-of Montlake
0.007
Source 5 – UW TPSS propulsion currents
0.001
Source 6 – Crossover propulsion currents
0.002
Total
0.173 mG
This total is well below the 0.3 mG UW Requested Threshold for Fluke Hall.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 23
Mechanical Engineering Building & Annex, Wilcox Hall, Roberts Hall and
Fluke Hall (the Group 2 buildings)
The ME Building & Annex and Wilcox and Roberts Halls are located closer to the North
Link ROW than any other Group 1 & 2 UW labs, and these are locations where B-field
levels from North Link operations are predicted to exceed the UW Requested
Thresholds. Final design of the ROW alignment has moved the ROW still closer to
these buildings causing predicted B-field levels to rise. In the new ROW alignment the
southbound track actually passes directly under a corner of the M.E. Annex. Table 6
below compares the distances from the ROW to the nearest labs in 2006 and 2012.
The April 2006, June 2008 and recently predicted B-field levels from trains directly
passing the Group 2 buildings are given in Table 7. The April 2006 values are from Ref.
1, Table 3.3, pg. 39. The June 2008 levels are from Ref. 3, Table B.1, Appendix B.
Three levels are seen to have increased. The ME Annex level has decreased because
at very close distances the maximum B-field points lie a short distance to either side of
the ROW and the bottom of the trough between the maxima has been moved under the
M.E. Annex.
Table 8 compares April 2006, June 2008 and presently predicted B-field levels at the
four labs from all sources. B-field contributions from the crossover have been omitted
because if a train is in the crossover other contributions are diminished.
Note especially that the B-field values in the April 2006 column in Table 8, when
rounded to two decimal places, yield the ST Baseline Prediction values for Fluke Hall,
ME Bldg. & Annex, Roberts Hall and Wilcox Hall stated in Exhibit B.2 of the UW-ST
Master Implementation Agreement.
The predicted total B-field levels at three of these labs are seen to have increased,
largely because of the increase in contributions from the B-field mitigated region due to
the ROW alignment moving closer to the labs. According to the UW-Sound Transit
Master Implementation Agreement these increases will have to be discussed with UW.
90% North Link EMI Prediction Report – Holmstrom – September 2012
Table 6
Shifts in ROW to lab distances for the closest Group
1 & 2 UW labs – 2006 to 2012
2006
EMF Sensitive Site
Fluke Hall
ΔH = ΔV =
EMF Horiz. Vert.
Site Dist.
Dist.
(m)
(m)
pg. 24
2012
2008
r=
ΔH =
slant Horiz.
dist
Dist.
(m)
(m)
ΔV =
Vert.
Dist.
(m)
r=
ΔH =
slant Horiz.
dist
Dist.
(m)
(m)
2006 to 2012
2008 to 2012
ΔV =
Vert.
Dist.
(m)
r=
slant
dist
(m)
Δr
2006
to
2012
(m)
Δr %
2006
to
2012
Δr
2008
to
2012
(m)
Δr %
2008
to
2012
7
102
26
105
99
27
103
113
27
116
11
10
14
13
ME Bldg & Annex
11c
3
38
38
3
38
38
0
37
37
-1
-7
-1
-4
Roberts Hall
12
78
38
87
80
38
89
65
34
73
-14
-15
-15
-17
Wilcox Hall
13
34
38
51
34
38
51
23
35
41
-9
-22
-9
-19
Surgery Pav.-1st Fl.
10a
88
33
94
83
30
88
83
29
88
-6
-5
0
0
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 25
Magnetic field levels from Sources No’s 1 & 2 for the
Group 2 buildings – B-field mitigated region and Brooklyn
Stub; from Ref’s 1 & 3 and from Table 1 of this report.
Table 7
Sources 1 + 2 B,mitig
(mG)
lab
April
2006
June
2008
Jan.
2012
M.E. Building
0.875
0.753
1.220
M.E. Annex
1.598
1.505
1.489
Roberts Hall
0.284
0.259
0.374
Wilcox Hall
0.810
0.773
1.181
Fluke Hall
0.223
0.208
0.163
Table 8
April 2006, June 2008 and January 2012
Magnetic field levels from Sources 1-5 for the
Group 2 buildings; from Ref’s 1 & 3 and from
Table 1 of this report.
Jan. 2012 B-field levels (mG) from Sources 1-5
lab
Sources Source
1+2
3
Source
4
Source
5
Jan. '12 June '08 Apr. '06
B,tot
B,tot
B,tot
(mG)
(mG)
(mG)
M.E. Bldg.
1.220
0.020
0.024
0.003
1.267
0.785
0.907
M.E. Annex
1.489
0.019
0.024
0.003
1.535
1.537
1.630
Roberts Hall
0.374
0.015
0.036
0.008
0.433
0.294
0.319
Wilcox Hall
1.181
0.014
0.039
0.012
1.246
0.809
0.846
0.163
0.007
0.001
0.002
0.173
0.241
0.256
Fluke Hall
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 26
Predicted Magnetic Field Levels at All Labs – 2006 and early 2012
Table 9. Summary of B-field levels predicted in early 2012 and in 2006 for all critical UW labs. The 2006
levels are from Ref. 1, Table 4.1. Group 2 labs with B-field levels exceeding ST Baseline
Predictions are shown in bold.
UW
2012
2012
2012
2012
2012
2012
Req. Sources
EMF Sensitive Site
Source 3 Source 4 Source 5 Source 6
Btot (mG)
T'hold
1+2
(mG)
(mG)
(mG)
(mG)
(mG)
(mG)
Bagley Hall
0.1
0.024
0.024
0.008
0.002
0.001
0.059
Chemistry Bldg.
0.1
0.022
0.020
0.010
0.002
0.001
0.055
EE/CS
5.0
0.239
0.019
0.010
0.003
0.005
0.275
Physics/Astronomy
0.5
0.024
0.025
0.008
0.001
0.000
0.059
Johnson Hall
5.0
0.047
0.030
0.007
0.001
0.001
0.087
Fluke Hall
0.3
0.141
0.022
0.007
0.001
0.001
0.173
0.2
1.489
0.019
0.009
0.003
0.005
ME Bldg. & Annex
1.525
0.1
0.374
0.015
0.014
0.008
0.016
Roberts Hall
0.427
0.1
1.181
0.014
0.015
0.012
0.018
Wilcox Hall
1.240
CHDD
0.3
0.021
0.010
0.064
0.024
0.033
0.151
Diagnostic Imaging
5.0
0.017
0.012
0.026
0.015
0.018
0.089
Surgery Pavilion* - 1st Fl.
1.0
0.264
0.010
0.048
0.443
0.669
0.883
Surgery Pavilion* - Pking
1.0
0.280
0.010
0.048
0.465
0.744
0.966
Fisheries Center (FIS)
0.1
0.008
0.011
0.040
0.008
0.011
0.078
Marine Sciences
1.0
0.031
0.013
0.018
0.002
0.002
0.065
* Also called the Ambulatory Care Facility. At Surgery Pav. max Source 5 and Source 6
B-fields cannot be present simultaneously.
**From Table 4.1 in Ref. 1
Source 1 - B-field mitigated region rails & cables
Source 4 - South-of-Montlake rails & cables
Source 2 - Brooklyn stub
Source 5 - UW TPSS propulsion currents
Source 3 - Brooklyn-Roosevelt rails & cables
Source 6 - Crossover propulsion currents
2006
Btot
(mG)**
0.076
0.066
0.217
0.070
0.110
0.256
1.630
0.319
0.846
0.183
0.087
0.471
0.093
0.045
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 27
Examination of Table 9 shows that the only critical UW labs at which the 2012 predicted
B-fields exceed the UW Requested Thresholds are the three at which the 2006
predicted B-fields also exceeded the UW Requested Thresholds, namely the three
Group 2 labs ME Bldg. & Annex, Wilcox Hall and Roberts Hall. As noted previously in
this report, since the 2012 levels at two of these labs, namely Wilcox and Roberts Halls,
also exceed the 2006 levels that constituted the ST Baseline Predictions, this matter will
have to be discussed by the UW and ST.
9.
MAINTENANCE OF B-FIELD MITIGATION DURING A UW TPSS RECTIFIER
SHUTDOWN
There are a number of B-field mitigation circuit designs that have been implemented at
other transit systems. [Ref. 3] The design being implemented at the UW campus was
chosen because it meets the need for sectionalizing the propulsion power system while
avoiding rail cross bonds with series switches and NB-to-SB OCS jumpers with series
switches at the northern and southern ends of the B-field mitigation region – positions in
the tunnels remote from stations.
To guarantee proper operation of the U-Link/North Link B-field mitigation propulsion
circuitry in the mitigated region electrical isolation of the B-field mitigated region from the
non-mitigated regions north and south must be maintained at all times, except when
trains short across the rail insulated joints at the corners of the mitigated region in
prescribed fashion.
The analysis of B-field levels undertaken for this report led to the conclusion that
additionally, to minimize the maximum length of rectifier-to-train current loops in the
South-of-Montlake region, which is important for meeting the UW spec B-field levels at
certain labs, the South-of-Montlake tracks must have power fed from both the northern
and southern ends at all times.
It is envisioned that occasionally the single rectifier at the Capitol Hill TPSS or one of
the three rectifiers at the UW TPSS will be taken out of service for maintenance or
repair. To allow this while simultaneously meeting the operating conditions noted above
modifications [Ref. 4] have been made to the design of the UW TPSS outlined in Ref. 2.
Switches have been added and wiring modified to allow the following operation:
As detailed in Ref. 2, during normal operation the Montlake, NB UW and SB UW
rectifiers all will be electrically isolated from each other. Electrical isolation of the NB
and SB UW rectifiers will allow suppression of unwanted return current paths provided
no more than three of the IJ pairs at the four corners of the B-field mitigated region are
shorted by trains crossing them at once.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 28
Also as detailed in Ref. 2, during shut-down of either the NB or SB UW rectifier the
remaining UW rectifier will power both NB and SB UW tracks. Under this operating
condition suppression of unwanted return current paths will require that only one of the
IJ pairs at the northern end of the B-field mitigated region may be shorted by trains
crossing at once; and the same constraint exists at the southern end.
However, during shut-down of the Montlake rectifier the modified propulsion circuitry
[Ref.4] will allow the SB UW rectifier to serve in its place, electrically isolated from the
NB unit. The NB unit will then power both the SB and NB UW tracks in the B-field
mitigated region. The operating constraints imposed to suppress unwanted return
current paths will be the same as when the NB or SB rectifier is out of service as
described above.
These constraints on train movement described above will be addressed by
contingency train operating procedures.
Under conditions of multiple rectifier outages it may not be possible to guarantee B-field
mitigation. Safety of passengers and equipment will have to be given priority.
90% North Link EMI Prediction Report – Holmstrom – September 2012
pg. 29
REFERENCES
1.
North Link Hi-Lo Mitigation EMI Report, F. Ross Holmstrom & LTK Engineering
Services, Document No. LTK.ST.0406.001, April 2006.
2.
ST Link Light Rail Project, 100% EMI Prediction and Mitigation Design Report, LTK
Engineering Services, Document No. LTK.ST.1108.002, November 2008.
3.
ST Link Light Rail Project, 90% EMI Prediction and Mitigation Design Report, LTK
Engineering Services, Document No. LTK ST.0608.002, June 2008. Appendix C,
“Configuration of UW TPSS for U-Link”, pg. 3, Description of Options. (Attached)
4.
U830 Contract Plan L10-JT502 REV 1, LTK Engineering Services, 01/10/12.
(Attached)
5.
N-Link 60% EMI UW Comments - Complete (Attached)
Reference. 3
Appendix C
“Configuration of UW TPSS for U-Link”
LTK Memo
November 2007
90% EMI Prediction
and Mitigation Design Report
Appendix C
June 11, 2008
Reference. 3
LTK Engineering Services
ST Link Project Office
MEMORANDUM
To:
George Hodges
From:
Denny Porter, Ming Li , Ed Rowe
Date:
November 16, 2007
Subject:
Configuration of UW TPSS for U-Link
File:
Doc:
3632-2.430
IMK-004
Background and Purpose
The purpose of this memo is to recommend the number of traction power rectifiers
located in the substations at the University of Washington (UW) passenger station, and
how these rectifiers should be configured to connect to the overhead distribution system
and the running rails on Sound Transit’s University Link extension.
Due to predicted EMI magnetic field levels generated from operating Sound Transit (ST)
light rail vehicles, the North Link light rail alignment has been designed with special
mitigation features to limit the influence of these magnetic fields. The rail alignment will
pass under the UW campus where sensitive instruments and experiments are located in
several nearby UW buildings. Sound Transit’s design will protect these instruments and
experiments. The primary component of LTK’s conceptual design, known as the “hi-lo”
mitigation design, involves substantial changes to the normal overhead contact system
(OCS) design. The basic concept of this hi-lo design uses a buried DC cable with a large
cross sectional area to carry the majority of the positive traction current. The messenger
wire will be used to provide only mechanical support for the contact wire. Closely spaced
risers will connect the buried cable to the contact wire. This DC cable will be placed
beneath the centerline of the two parallel running rails which serve as the return path of
the traction power current. As a result, the magnetic fields generated by the currents
flowing through the buried cable and the running rails will largely cancel each other to
achieve the mitigation of the EMI. This basic design concept is similar to that which has
been placed into service and tested in St. Louis and previously to that in Bielefeld,
Germany.
The configuration of the traction power substation (TPSS) at UW Station has also been
considered a component of the EMI mitigation concept for some time. North Link
Preliminary Engineering (PE) work suggested the mitigation section be electrically
isolated from the rest of the traction power system and be independently fed by a single
Reference.
To:
George3
Hodges
Page 2 of 10
November 16, 2007
From: Denny Porter, Ming Li, Ed Rowe
TPSS with two separate rectifier units; one to feed only the northbound (NB) track and
the other to feed only the southbound (SB) track. It was also suggested that the Montlake
TPSS, which feeds the section south of the mitigation section, be used as back-up to feed
the mitigation section in the event that the UW TPSS loses power. Thus, the two TPSS
would have a total of four rectifiers.
Since this mitigation design is a relatively new concept, it has taken some time to
evaluate and determine how the design of the traction power substations will contribute
to the mitigation of EMI. LTK is concentrating on the traction power overall design to
determine how the design could be optimized by reducing the number of transformer
rectifier units from four units to three, or even two units. This discussion is further
presented herein.
To progress the design of the traction power system for U-link and the civil work of the
UW Station, a timely conclusion of the TPSS configuration for the UW Station is
required. This report summarizes previously proposed UW TPSS designs, reviews
design options and recommends a final design configuration.
Overview of Options
In the UW passenger station box, there will be two traction power substations; Montlake
(ML) TPSS which will feed the Capitol Hill to UW section (South of EMI mitigation
section), and UW TPSS, which will feed the EMI mitigation section. Due to space
limitations of the alignment, ML TPSS will be located several hundred feet away from its
preferred location at the south end of the EMI mitigation section. Geographically, ML
TPSS will share the space with UW TPSS, in UW passenger station (See Figure 1)
The Power Supply Configuration of EMI Region
Capitol Hill
Passenger station
UW
Passenger station
Capitol Hill
TPSS
Mont Lake
TPSS
Non-Mitigation Section
UW TPSS
EMI Mitigation Section
Figure 1
UW TPSS will feed the EMI mitigation section singly without the double end-fed
application (a feed from two substations at opposite ends) of normal traction power
Reference.
To:
George3
Hodges
From: Denny Porter, Ming Li, Ed Rowe
Page 3 of 10
November 16, 2007
system design. The design also considers a single TPSS outage situation which could
occur to either UW TPSS or ML TPSS.
Disconnect switches will be used to link UW TPSS and ML TPSS to provide back-ups
for these substations should either fail. Except for the single line diagram design of
arranging the switching devices, the capacities of the transformer rectifier units also need
to be taken into consideration for emergency situations.
LTK commenced preliminary TPSS design a few years ago to provide a basic overall
EMI mitigation design. There were several options for the TPSS designs at early project
stages. LTK chose the most conservative (and highest cost) option to be presented in the
EMI mitigation report during the PE phase.
As additional data recently became available from St. Louis Metro Cross County EMI
design, LTK discovered that some of the St. Louis design concepts could be utilized on
our U-link design. LTK recently reviewed the St. Louis EMI mitigation test report and
found that the design provides a very high level of EMI mitigation. Those findings have
encouraged us to further study the St. Louis case. Currently, LTK has developed a new
design which combines the advantages of both our original design and the St. Louis
design.
Description of Options
Four options have been developed, as follows:
Option 1
Bielefeld style
Option 2
St Louis style
Option 3
Single rectifier Seattle style
Option 4
Hybrid style
The following outlines the basic concepts of each option.
Reference.
To:
George3
Hodges
From: Denny Porter, Ming Li, Ed Rowe
Page 4 of 10
November 16, 2007
Option 1 – Bielefeld Style
Note: OCW Equals Overhead Contact Wire
Description of the Circuit: This design incorporates a total of 4 rectifier units.
SB and NB tracks are electrically isolated from each other and from the
unmitigated regions. Traction current paths to any train are simple and direct. The
avoidance of sneak current paths imposes limitations on simultaneous bridging of
IJ’s of sections and in crossovers.
Advantages: Highest immunity from ground currents arising outside of the
mitigated region. Constraints on simultaneous bridging of IJ’s at the end of each
section and in the crossover are less severe than for the one-rectifier Seattle-style
circuit.
Disadvantages: Requires two rectifiers dedicated to the mitigated region. There
are constraints on simultaneous bridging of IJ’s at the end of each section and in
the crossover.
Systemwide Electrical Consideration: To assure ML TPSS is able to back up
UW TPSS 100 percent during an emergency, the same design is applied on ML
TPSS. On the 26kV side, four 26kV feeders will provide energy to the four rectifier
units as shown on the 26kV single line diagram.
Station Space and Capital Cost Consideration: Approximately 2800 square feet
of space is required to accommodate all the TPSS equipment in the Station. The
related civil work estimate is 2.8 million dollars (cost estimate is provided by
Chudgar Engineering Company). The cost of TPSS equipment and related
electrical is 4.1 million dollars (including both Montlake and UW TPSS). The total
cost is 6.9 million dollars.
Reference.
To:
George3
Hodges
From: Denny Porter, Ming Li, Ed Rowe
Page 5 of 10
November 16, 2007
Option 2 – St. Louis Style
Note: OCW Equals Overhead Contact Wire
Description of the Circuit: This design uses a total of 2 rectifier units installed.
No insulated joints separate the mitigated region from the nearby un-mitigated
regions. Heavy cross-bonding of running rails, buried cables, and overhead contact
wires are installed at each end of the mitigated region. Cross-bonding of running
rails and/or OCS’s can be used outside the mitigated region. Circuit symmetry
causes the rail return current pattern, for currents from a train anywhere in the
mitigated region back to the TPSS, to exactly match the positive current pattern for
currents to the train. Either one of the two rectifiers may be eliminated provided the
remaining rectifier can handle the traction load.
Advantages: Simplicity, only one rectifier unit is needed.
Disadvantages: Potential for ground currents originating anywhere in North Link
to disrupt current balance conditions in the mitigated region.
Systemwide Electrical Consideration: To assure ML TPSS is able to back up
UW TPSS 100 percent during an emergency. The same design is applied on ML
TPSS. On the 26kV side, two 26kV feeders will provide energy to the two rectifier
units as shown on the 26kV single line diagram.
Tunnel Space and Capital Cost Consideration: Approximately 1500 square feet
of space is required to accommodate all the TPSS equipment in the Station. The
related civil work estimate is 1.5 million dollars (cost estimate is provided by
Chudgar Engineering Company). The cost of TPSS equipment and related
electrical equipment is 3 million dollars (including both Montlake TPSS and UW
TPSS). The total cost is 4.5 million dollars.
Reference.
To:
George3
Hodges
From: Denny Porter, Ming Li, Ed Rowe
Page 6 of 10
November 16, 2007
Option 3 - Single rectifier Seattle style
Note: OCW Equals Overhead Contact Wire
Description of the Circuit:This design uses a total of 2 rectifier units. SB and NB
tracks are completely electrically isolated from each other and from the
unmitigated regions. Current paths to any train are simple and direct.
Advantages: Only one rectifier unit is needed. This design can maintain high a
resistance to the potential effects of ground currents that originate outside the
mitigated region.
Disadvantages: Avoidance of sneak paths generate severe constraints due to
simultaneous bridging of the IJ’s at the ends of each section and in the crossover
with a two-rectifier circuit.
Systemwide Electrical Consideration: To assure ML TPSS is able to back up
UW TPSS 100 percent during an emergency. The same design is applied on ML
TPSS. On the 26kV side, two 26kV feeders will provide energy to the two rectifier
units as shown on the 26kV single line diagram.
Tunnel Space and Capital Cost Consideration: Approximately 1500 square feet
of space in the Station is required to accommodate all the TPSS equipment. The
related civil work estimate is 1.5 million dollars (cost estimate is provided by
Chudgar Engineering Company). The cost of TPSS equipment and related
electrical equipment is 3 million dollars (including both Montlake TPSS and UW
TPSS). The total cost is 4.5 million dollars.
Reference.
To:
George3
Hodges
From: Denny Porter, Ming Li, Ed Rowe
Page 7 of 10
November 16, 2007
Option 4 – Hybrid style
Note: OCW Equals Overhead Contact Wire
Description of The Circuit: This design uses a total of two rectifier units. SB and
NB tracks in mitigation region are electrically isolated from tracks in the adjacent
non-mitigated regions by insulated joints and breaks in OCS’s, thus mitigating any
spurious currents entering the mitigated region. St. Louis-style cross bonding is
used at the ends of the mitigated region and at the rectifier feed point, to achieve a
balanced positive and negative current flow to a train located anywhere in the
mitigated region. Analysis of St. Louis test data indicates that a circuit with cross
bonding at the ends of the mitigation region is highly effective in balancing current
flow. No limitations exist on simultaneous bridging of insulated joints at the end of
each section. Acceptable current distribution is guaranteed by circuit symmetry.
Advantages: Only one rectifier unit is needed. This circuit has the advantage of the
Seattle-style mitigated-region circuit isolation and the St. Louis-style
accommodation of multiple IJ bridgings at the end of sections.
Systemwide Electrical Consideration: In 26kV side, two 26kV feeders will
provide energy to the two rectifier units as shown on the 26kV single line diagram.
Space needs to be reserved for the second construction stage, if required.
Tunnel Space and Capital Cost Consideration: Approximately 2200 square feet
of space is required to accommodate all the TPSS equipment in the Station, which
includes the equipment for the second stage. The related civil work estimate is 2.2
million dollars (cost estimate is provided by Chudgar Engineering Company). The
cost of TPSS equipment and related electrical engineering is 3 million dollars
(including both Montlake and UW TPSS). The total cost is 5.2 million dollars.
Reference.
To:
George3
Hodges
From: Denny Porter, Ming Li, Ed Rowe
Page 8 of 10
November 16, 2007
Rectifier Unit Considerations in Abnormal Situations
The previous discussion focuses on rectifier configurations for normal operations, i.e.
with all TPSS in service, while this section deals with rectifier configurations in
abnormal situations, specifically when either the UW TPSS or ML TPSS is out of
service, for whatever reason, including failure, maintenance, troubleshooting, upgrade,
test, loss of ac, LRV-generated trips, etc.
Typically, Sound Transit TPSSs utilize only a single rectifier unit because each section of
OCS between any two adjacent TPSSs is fed by both TPSSs, i.e double-end feeding.
Thus, loss of one TPSS, in most cases, does not results in loss of power to the OCS
sections fed by the problem TPSS. However, for EMI mitigation purposes, it has been
recommended that EMI mitigation section be fed independently by only the UW TPSS.
Analysis has suggested that, even with the substantial measures to be taken by Sound
Transit to reduce stray current, particularly in the EMI mitigation section, there is still
some likelihood of stray current propagation, and this likelihood is moderately increased
in the event one TPSS feeds both the EMI mitigation section and the non mitigation
section. Further, the levels of stray current, while relatively small in corrosion terms,
appear to be significant enough to produce B-field levels that could be problematic and
require additional mitigation. Stray current and propulsion current have different
relationships to B-fields. B-fields levels fall off significantly faster with increasing
distance for propulsion current compared to stray current. Thus, smaller stray current
values have larger B-field effects. For example, only 2.5 amperes of stray current would
result in B-fields of 0.1 mG at 50 meters distance, i.e. even a small amount of stray
current can produce B-fields that can affect UW labs.
Option 1 provides this independent feed with two rectifier units while Options 3 and 4
utilize one rectifier unit. Regardless of the configuration, clearly some back-up must be
provided if the UW TPSS goes out of service. Furthermore, a back-up requirement is
needed if ML TPSS goes out of service. In this case, the section between Capitol Hill
station and the south end of the EMI mitigation section is double end fed by the Capitol
Hill TPSS and ML TPSS. Typically Capitol Hill TPSS and the next TPSS north of ML
TPSS would feed the section if ML TPSS goes out of service. However, the next TPSS
north of ML TPSS is the UW TPSS. In this abnormal situation, either the UW TPSS must
be configured to feed both the EMI mitigation section and the non-mitigation section to
the south or the non mitigation section is fed only by Capitol Hill TPSS. The former
negates the benefits of independent feed to the EMI mitigation section and raises the
potential for increased stray current, while load flow analysis shows that under high
service levels, approaching 4 car trains at 2 minute headways, OCS voltages are
compromised in the latter.
Given this situation, a reasonable response is to provide a second rectifier unit at the UW
TPSS which would have the capability to back-up either the original UW TPSS rectifier
unit or the ML TPSS unit. In effect, this second unit is a spare to be called to service in
case of problems with either TPSS. While some of the cost savings with Option 4 would
be reduced, the overall reliability of the traction power system will be improved.
Reference.
To:
George3
Hodges
Page 9 of 10
November 16, 2007
From: Denny Porter, Ming Li, Ed Rowe
Single Line Diagram Description:
The following simplified single line diagram represents LTK’s recommendation for
proceeding with the final traction system at the UW station.
Single Line Diagram of ML & UW TPSS
Back-Up Rectifier
UNIT
ML Rectifier
UNIT
26kV AC
UW Rectifier
UNIT
26kV AC
1500 DC
26kV AC
1500 DC
1500 DC
1
4
2
NR
3
SB NB
Feeding Non-Mitigation Section
Feeding Mitigation Section
Figure 2
Installation of all three rectifier units is recommended as part of the U-Link project.
Normal operation will require switches 1 and 4 to be normally closed, and 2 and 3
normally open. In the case that either Capitol Hill or ML TPSS goes out of service, the
capacity of the back-up rectifier unit is adequate to meet the traction power requirements.
If the UW rectifier unit goes out of service, switch 4 must be opened, and switch 3 must
be closed. If the ML rectifier unit goes out of service, switch 1 must be opened, and
switch 2 must be closed.
Reference.
To:
George3
Hodges
From: Denny Porter, Ming Li, Ed Rowe
Page 10 of 10
November 16, 2007
Conclusions and Recommendations:
By comparison of all 4 options, the One Rectifier Hybrid Style Propulsion Circuit
(Option 4) displays several advantages over the other designs for normal operations:
1. The Northbound (NB) and Southbound (SB) tracks in the EMI mitigation section
are intentionally short circuited together by crossbonding at several locations.
Thus, the sneak path current issue caused by the intentional electrical isolation
between NB and SB tracks is avoided to the maximum extent. The separation of
the running rails and OCS in the double crossover section is avoided as well with
this design.
2. This circuit maintains a relatively high resistance to effects of ground current
(stray current) from adjacent section.
3. The multiple crossbonding in mitigation section reduces the impedance of the
current return path, thus reducing the voltage rise which is the major cause of
ground current (stray current).
4. The underground equipment space is saved by applying the single rectifier unit.
The related engineering cost of civil work and electrical systems is also reduced.
5. Due to the simplicity of the propulsion circuit, the reliability, availability and
maintainability (RAM) are assumed to be relatively high.
Based on foregoing analysis, it is recommended that the one rectifier hybrid style
propulsion circuit is the most suitable configuration for the U-Link traction power supply
for normal operations.
However, considering the stray current situation and the investment that Sound Transit
will have in EMI mitigation, it is further recommended that option 4 be modified to
incorporate a third rectifier unit to serve as back-up to either ML TPSS or UW TPSS.
DLP:ML:EJR:jjd
cc:
Steve Procter
Ethan Kim
Ross Holmstrom
Dick Eacker
Akio Ueno
Reference. 4
Reference. 5
NORTH LINK DESIGN REVIEW COMMENT FORM
Reviewer:
Document Title:
Comments Submitted to:
Item
No.
Reviewer
Responder:
Date:
1
David Fugate
Reviewer
Organization
UW
Sec-Sheet No
Para- Disciplin
Dwg No
e
Comment
Organization
Responder
Code
Response
2
David Fugate
UW
EMI
Also for Section 5, report discusses the scenario with all power LTK
from Capitol Hill TPSS; was the scenario with 2 trains
drawing all power from the UW TPSS side modeled (Capitol
Hill offline)?
Holmstrom
1
3
David Fugate
UW
EMI
LTK
Holmstrom
1
4
David Fugate
UW
EMI
LTK
Holmstrom
1
A list of Group 1 and Group 2 labs was added to the Introduction so that reference to the various labs
could be made more smoothly in the rest of the report.
5
David Fugate
UW
EMI
LTK
Holmstrom
1
All typos have been corrected.
6
Andy Casillas
UW
EMI
Pg. 13 Next to last paragraph, sentence says UW TPSS feeds
all the way to Brooklyn, but I thought new design has UW feed
stopping at north end of mitigation and the stub fed back from
Brooklyn?
Section 8, pg. 16, second sentence is confusing with the
parenthetical “all Group 2 labs”. Also source numbering is not
consistent with previous sections of new source 1 in this
section).
full report with listing of typos attached.
ERMReview_of_Jan2012_60%Norhtlink_EMI_report
Per MIA 4.1.2 "In the event that the recalculated Predictions
exceed Baseline Predictions in Exhibits A-2 and B-2 at each
percentile achievement, Sound Transit shall take such steps as
may be necessary so that the recalculated Predictions are
below or at Baseline Predictions in Exhibits A-2 and B-2
unless otherwise agreed to by the University." The University
has not agreed to these predictions.
LTK
Holmstrom
4
The MIA calls for agreement by the UW to any breaches of the 2006 ST Baseline Predictions at Group
2 labs. The 2012 B-field calculations predict that such breaches will occur at two labs, which appears
to indicate that this issue will have to be addressed by ST and UW in a manner that is beyond the
scope of this report. The increases in predicted B-field levels have occurred based on the changes in
the ROW alignment both laterally and vertically that have been made as indicated. These changes
were made by Civil design efforts to address constructability as related to the construction of the
tunnels and the ultimate operation of the trains.
EMI
In Section 5 discussion of South of Montlake ROW on page
LTK
10, it was not clear why the cross-bond is implemented as part
of the design 1/3 of the way along this section. Figure 4 shows
the cross-bond only for the rails and thus the question: Will the
NB and SB source currents be different from NB and SB rail
currents (because the return currents have an additional return
path via cross-bond) and how much of an impact does this
have on magnetic fields at the north end of this section?
Holmstrom
1
The single cross bond noted adds complexity to the task of determining currents in the rails between
Montlake and Capitol Hill and their resulting B-field contributions. It also causes rail current patterns
that lead to slightly higher levels of B-field than would occur if it were absent. However, its presence in
the rail circuit is required to assure sufficiently low values of train-to-substation rail resistance. Absent
the requirements to minimize B-field levels many more cross bonds would have been used between
Montlake and Capitol Hill. Because of the requirement to minimize B-field the number of cross bonds
was reduced to the barest minimum that the power considerations would allow. Fortunately, the
resulting rail circuit design with the single cross bond resulted in prediction of acceptable B-field levels.
The following paragraph was added near the middle of Sec. 5:
Capitol Hill and Pine Street rectifiers will never be off-line simultaneously except under the most
extreme circumstances. Therefore the Capitol Hill to Montlake tracks always will be driven from both
ends except in the most extreme circumstances, thus assuring optimum B-field performance. When a
train is operating between rectifiers it tends to receive the greater current from the nearest rectifier,
thus minimizing the length of the current loop. Additionally, the current in the OCW-rail loop ahead of
the train will flow around the loop in opposite sense to current in the loop behind the train, causing the
B-fields from the loops to partially cancel.
Correction was made in the text.
RESPONSE CODES:
1. = Will comply, incorporation planned. 2. = Clarification required. 3. = N/A 4. = No action required. 5. = Input required by others.
STATUS CODES:
I - In work C = Complete N/A = Not applicable
Page 1 of 2
Reference. 5
Document Title:
Comments Submitted to:
Item
No.
Reviewer
Date:
7
Andy Casillas
Reviewer
Organization
UW
8
Andy Casillas
UW
Sec-Sheet No
Para- Disciplin
Dwg No
e
Comment
Organization
Responder
Code
Response
EMI
What is the error band on EMI predictions
LTK
Holmstrom
4
The issue of error statistics for the U-Link and North Link B-field calculations is a very good one to
bring up. There are so few operational rail transit systems where B-field mitigation has been
employed that not enough data exists to perform a statistical analysis of predicted vs. actual B-field
levels.
This author has had the opportunity to visit two such systems to observe operational testing of their Bfield mitigation systems – the light rail line running by the University of Bielefeld in northern Germany
that has been operational since 1998, and the more recent line running by the main campus of
Washington University in St. Louis, MO. In each case the observed B-field levels were generally
reasonably close to predicted levels.
In 2003 we made measurements of the perturbation B-field levels due to passage of Portland light rail
cars very much like the Seattle cars and found results that were consistent from run to run, and with Bfield vs. distance behavior very close to theory, so the presumption is that perturbation B-fields can be
predicted fairly accurately. We also measured B-fields generated by a train drawing known current
through a substation-to-train loop of known height and the predicted and observed B-fields agreed
quite well.
The question of how well the B-field cancellation in the mitigated region will work is a big one to ask.
As indicated above, it seems to work well enough in Bielefeld and St. Louis. And, the analysis in Sec.
4 of Ref. 1 indicates that the B-field cancellation does not have to be perfect for the UW specs to be
met. Sec. 5 of Ref. 1 shows that some reasonably coarse tolerances can be applied.
Practically all the B-field calculations performed for this project have been worst-case calculations. All
currents have been assumed to be max-level and B-field contributions from different sources, for
instance geomagnetic perturbations and currents, have been assumed to all point in the same
direction.
EMI
EMI predictions and cumulative ranges must be shown for all
B.1 and B2 buildings comparing MIA thresholds to
predictions.
LTK
Holmstrom
1
A new Table 9 has been included giving the 2012 and 2006 predicted B-field levels at all critical UW
labs alongside the UW spec levels.
9
10
11
12
13
RESPONSE CODES:
1. = Will comply, incorporation planned. 2. = Clarification required. 3. = N/A 4. = No action required. 5. = Input required by others.
STATUS CODES:
I - In work C = Complete N/A = Not applicable
Page 2 of 2