INDUCTIVE COORDINATION STUDY OF A
POWER DISTRIBUTION LINE AND
RAILROAD SIGNALED GRADE CROSSING
Marvin Frazier
Corr Comp Co.
870 E. Higgins Rd. STE 129
Schaumburg, IL 60173
877-300-2003
David W. McCord, P.E.
McCord Engineering, Inc.
13616 “W” Street
Omaha, NE 68137-2948
402-895-1989
James G. LeVere
BNSF Railway Company
2600 Lou Menk Dr.
Fort Worth, TX 76131-2830
817-352-1916
David Oswald
Empire District Electric Co.
931 E. 4th
St.
Joplin, MO 64801
417-625-6540
word count 7015 ( 4265 words +11 figures x 250)
© 2012 AREMA
ABSTRACT
Power system distribution harmonics are often “blamed” for rail signaling issues, but tracking
down the source and deciding how to mitigate the problem can be difficult. The procedures and
methods described in this presentation of a real world study may be useful to signal engineers for
evaluating similar problems in other possibly incompatible shared corridors.
This study investigated an electromagnetic compatibility problem between a BNSF at-grade
crossing and a parallel Empire District Electric (EDE) 12 kV distribution line. Power-frequency
harmonic voltage that was coupled to the rail system caused frequent false activation of a
signaled grade crossing and personnel safety issues. The goal of the investigation was to identify
the source of the harmonic interference and to investigate possible methods of mitigation
The study blended both field measurements and computer modeling to produce a compatible
solution. A computer model of the two systems was structured to include the location and rating
of the distribution transformers and their harmonic generation, which varied as a function of
power customer load demand. The model was then used to evaluate the harmonic coupling to
the rail system and the effectiveness of practical power system changes that could reduce the
predicted harmonics coupled into the rail system. The model provided reasonable agreement
with measured load flow and harmonic current data. The model showed that the harmonic
coupling could be effectively eliminated by either of two mitigation options. After completion
of the study, one of the mitigation options was implemented by the power company. No
subsequent compatibility issues have been noted for this exposure.
© 2012 AREMA
The paper presents the step-by-step process used to investigate the problem and develop
alternative compatible solutions. It also contains a description of the model and shows graphs of
recorded data that were used to zero in on the cause of the induced voltage problem.
BACKGROUND AND INTRODUCTION
Signal system malfunctions have occurred on a single-track BNSF rail line, principally
associated with a signaled grade crossing at a busy street, Railroad Milepost 325.25. An Empire
District Electric (EDE) 12kV distribution line that is overbuilt by a 69kV transmission line
shares the right-of-way (ROW) for approximately 3.5 miles east of the affected grade crossing
location, see Figure 1. The grade crossing signals are controlled by a PMD motion detector.
Track insulated joints (IJ’s) exist for an intermediate block signal at MP 324.8 that is within, but
near the end of, the east approach termination for the grade crossing. These insulated joints were
originally bypassed with tuned insulated-joint bypass couplers (TJC) to extend the grade crossing
approach beyond the insulated joint location. However, the tuned joint couplers malfunctioned
or were damaged on several occasions, apparently by power-frequency voltage that was
developed across the rail insulated joints.
© 2012 AREMA
Strait St.
Substation
MP 325.25
TJC's RemovedIJ's @ MP 324.8
IJ's @ MP322.2Track
Power Line
Not to Scale
N
Original Approach 2640'
790'
NBS OriginalNBS New
Figure 1. Sketch of Railroad and Power System near Interference-Affected Crossing.
The BNSF subsequently removed the tuned joint couplers and shortened the east approach length
of the crossing by placing a tuned shunt (at the PMD frequency) rail-to-rail on the west side of
the insulated joints. That procedure eliminated the prior tuned-joint coupler problem, but
necessitated a slower speed for west-bound trains to maintain adequate warning time for the
grade crossing due to the shortened east approach length. The restriction of train speed is
detrimental to the operation of the rail system.
Empire District Electric (EDE) performed initial investigations of the reported rail-system
voltage to assess if the voltage might be related to the distribution line that shares the railroad
ROW east of the Strait St. crossing. These test results all indicated that the observed power-
system related rail voltage is likely caused by the parallel distribution line.
The primary goal of the Corr Comp investigation was to identify approaches for reducing the
harmonic excitation of the track system by the power line.
© 2012 AREMA
FIELD DATA COLLECTION
Field data was collected to obtain a simultaneous logging of relevant information on the power
distribution line and the railroad, with the intent of using the information to structure a computer
model of the two systems.
Monitoring of Distribution Line
Figure 2 shows a sketch of the distribution system near the region of parallel of the two systems.
The segment of the distribution line that parallels the rail line has no built-in provision for
measuring the line current. Therefore, instrumentation was sought that could measure the
current in the distribution line conductors, including harmonics.
SubstationTra
ck
IJ MP324.8
IJ MP322.2
Switched Cap
Not to Scale
Line 375-1Line 375-2
Fixed Cap
Regio
n 1
Regio
n 2
Region 3
MDP3 Location 1
MDP3 Location 2
MDP3 Location 3
North
Racine
Figure 2. Sketch of Distribution System Near Substation
Distribution Y
© 2012 AREMA
The Megger Distribution Profiler (MDP3) was chosen to obtain the distribution line parameters
for this project. The MDP3 is designed to be clipped to each phase of a distribution line and to
log electrical parameters of interest, including:
RMS Current
Power (kW,kVAR, kVA & PF)
Waveforms
Total Harmonic Distortion (THD)
Harmonics (1-32)
Figure 2 shows the three locations on the distribution line where MDP3 units were placed to
monitor distribution line parameters. Location 1 was just east of a Y in the distribution line near
the substation (the west end of the railroad parallel exposure). Location 2 was at the east end of
the railroad parallel exposure, and Location 3 was just north of a fixed three-phase capacitor
bank location.
Figure 3 shows the MDP3 units being placed on the distribution line. Also shown in the figure is
the overbuilt 69-kV transmission line and the overhead neutral, which also has an installed
MDP3. One limitation of the MDP3 units is that the lowest current that can be logged is 10
amperes. That restriction prevented the use of the MDP3 units to monitor specific load drops
and limited the extent of useful information on the current in the neutral.
© 2012 AREMA
Figure 3. MDP Monitors Being Placed on Distribution Line.
The MDP3’s, as described above, provided the primary characterization of the distribution line
for this investigation. In addition, the bus voltage at the substation, as provided by a Schweitzer
SEL-351 at the substation and the voltage on one phase of the distribution line at the switched
capacitor bank in Racine were monitored for modeling and analysis.
Monitoring of Track
Monitoring equipment was installed on the track at three locations; the grade crossing site (RR
MP 325.25), and the IJ’s at MP 322.2 and MP 324.8 those milepost locations are shown in
Figure 1.
© 2012 AREMA
Two types of logging equipment were installed to monitor the track signal system:
Dranetz 4400 power quality analyzers were used to monitor induced rail voltage. These
were mounted in the signal bungalows. The four rail-to-ground voltages at each of the
two IJ locations were logged at 10-minute intervals. In addition, a Dranetz 4400 logged
the rail-to-ground and the rail-to-rail induced voltages at the crossing.
The ElectroCode (EC) voltage and current was logged at each end of the track circuit
between MP 322.2 and MP 324.8 during the testing period. Using the transmitted and
received EC voltage and current at each end of the signal block, an average value for the
track circuit ballast can be calculated. An industrial data logger, DATAQ Model 718B,
at each end of the signal circuit logged the rail-to-rail ElectroCode voltage and output
current for approximately 3-seconds every 15 minutes.
© 2012 AREMA
FIELD DATA AND ANALYSIS
The only data available on the fundamental frequency performance of the distribution system
was the data from the MDP3 units. Those data were only available at three locations and no
information for discrete loads or for branch lines feeding several loads (load cluster data) could
be obtained. Therefore it was necessary to make numerous assumptions and approximations in
the development of a model of the distribution system.
Figure 2 shows the locations of the three groups of MDP3 logging devices. We defined three
related load regions, Region 1, Region 2, and Region 3 that are also shown on Figure 2.
Load Region 1 is bounded by MDP3 Locations 1 and 2.
Load Region 2 is bounded by MDP3 Locations 2 and 3
Load Region 3 is all the distribution system that is north and east of MDP3 Location 3.
The recorded real and reactive power flow at those three locations tends to be cyclical on a daily
basis for the whole month-long monitoring period. Figure 4 (Location 1), Figure 5 (Location 2),
and Figure 6 (Location 3) show the real power (kW) and reactive power (kVAR) for a two-day
period that encompasses representative ‘high-load’ and ‘low-load’ periods measured by the
MDP3’s.
© 2012 AREMA
Figure 4.Measured kW & kVAR at Location 1.
Figure 5. Measured kW & kVAR at Location 2.
© 2012 AREMA
Figure 6. Measured kW & kVAR at Location 3.
The following two figures show the fundamental and third harmonic current logged for the same
two-day period by the MDP3 units at Location 3, which is just downstream of the fixed capacitor
bank, Figure 7 shows the fundamental currents in each phase conductor, while Figure 8 shows
the third-harmonic current in each phase conductor. The plots in these figures only span the
period of July 26 and July 27, which are the days chosen for representative ‘high and low’
loading as previously noted.
© 2012 AREMA
Figure 7. Phase Current at MDP3 Location 3 - Two Day Period.
Figure 8. Third harmonic (180 Hz) Line Current at MDP3 Location 3 - Two Day Period
© 2012 AREMA
Comparison of Figure 7 and Figure 8 shows that when the fundamental currents are at a relative
maximum, such as the 1500 hour of July 26, the third harmonic current is a relative minimum.
Conversely, when the fundamental current is a relative minimum, such as during the 0300 hour
of July 27, the third harmonic is a relative maximum. This current pattern is exhibited in all the
recorded data on the distribution line for a one-month period.
Figure 9 is an output from the Dranetz monitor of the third harmonic rail to ground voltages on
the east side of the MP 324.8 IJ’s for the same two-day period shown above for the power line
data. It is seen that the relative maximum and minimum rail harmonic voltage occurs at the same
times as the relative maximum and minimum harmonic distribution line current in Figure 8.
Thus, the measured field data tend to be consistent with the maximum harmonic line current and
induced rail voltage occurring when the fundamental line current tends to be a minimum, and
vice versa.
Figure 9. Measured Third Harmonic Rail-Ground Voltage at MP 3248 IJ.
© 2012 AREMA
POSSIBLE CAUSE OF THE HARMONICS
The vast majority of the literature that discusses distribution line harmonics describes the
harmonics as resulting from the non-linear loads to which the distribution line must supply
power. The literature suggests that as the load current increases, the harmonic current that is
caused by the non-linear load should also increase.1 However, that is not the condition that
occurs on this distribution line. For this distribution line, the harmonic currents increased as the
load decreased and vice versa.
Another possible source of harmonic current on a distribution system is the load transformers
used to step down the voltage to the customer. The transformers on this system step the voltage
down from nominally 7200 volts (line-to-neutral) to 120 volts. Review of the literature showed
that some citations discuss distribution transformers as possible sources of harmonic current.
However, only one paper was found that provided quantitative values that appeared suitable for
use in modeling. That citation reported the results of testing 123 transformers having ratings of
15, 25, and 50 kVA for total harmonic distortion as a function of applied voltage up to 110% of
rated voltage.2 It is also noted elsewhere in the literature that transformer manufacturers force
the devices to operate at very close to the knee of the magnetizing curve at rated voltage.
MODEL DEVELOPMENT APPROACH AND RESULTS
1 An Investigation of Harmonics Attenuation and Diversity Among Distributed Single-Phase Power Electronic Loads, A. Mansoor,
et al, IEEE Transactions on Power Delivery, Vol. 10, No. 1, January 1995 2 Lynnda K. Ell and M. Earl Council, “Distribution Transformer Excitation Harmonics”, Electric Power Systems Research, 17
(1989) pp 13-19.
© 2012 AREMA
The benefit of developing a model of the power distribution and rail systems is that once
reasonable agreement is shown between the model and available measured data, then the model
can be used to evaluate conditions for which data does not exist, such as for evaluating possible
mitigation approaches. The model used the power system and rail measurements described
above to help identify the source of harmonics and to evaluate mitigation alternatives. The
model considered the fundamental frequency performance and the harmonic characteristics of
the distribution system as well as the coupling to the railroad system.
EDE provided the location and kilovolt ampere product (kVA) rating of each transformer fed by
the distribution line. For simplicity, we grouped the transformer load taps into clusters, which is
a group of loads (transformers) that is connected to the distribution line within a limited distance.
For each load cluster, we determined the percent of the total rated kVA by region and phase.
Thus, for example a given load cluster may have 3% of the rated kVA for the phase and region
that it is a member.
For simplicity in model development, we considered a representative high-load period and a
representative low-load period. We used the measurements at a time of interest to estimate the
actual load kVA for each phase and region, which is less than the rated value. We then used the
percentage rated kVA of each load cluster to apportion the actual delivered kVA. That is, for a
given load cluster, if it was 3% of the rated kVA in a region, then 3% of the delivered kVA for
that region (estimated from the measurements) was assigned to that cluster. By that procedure,
© 2012 AREMA
we were able to estimate the fundamental frequency line current along the distribution line and
the line voltage at each cluster location, using the model.
We chose a representative ‘high-load’ period of time (the 1500 hour on 7-26-10) and a
representative ‘low-load’ period (the 0300 hour on 7-27-10) for use in developing the model.
The model also used the substation bus voltage as measured by the Schweitzer SEL-351 at those
times as the drive for the distribution line. The model loading was iteratively adjusted to give a
reasonable agreement to the measured kW and kVA for the three regions measured by the
MDP3’s. The measured kW and kVA data of Figure 4 through Figure 6 show heavier colored
bars for the 1500 hour on 7-26-10 and the 0300 hour on 7-27-10, which are values calculated by
the model. Similarly, the measured distribution fundamental currents of Figure 7 show heavier
colored bars for these same time periods, which were calculated by the model.
The above results suggest that the basic fundamental frequency (60-Hz) model of the distribution
line is reasonable. Thus, we might expect the modeled distribution line fundamental current and
voltage to be a reasonable approximation to the field values for those times, although we really
don’t know how the actual load is distributed among the various load clusters within each region.
The next consideration is how to include the distribution system transformer nonlinearities into
the model to compare with harmonic voltages that were measured on the track.
Figure 10 shows our plotting of relevant data of citation (2). Two straight-line approximations
are shown in the figure. The top ‘red’ line is derived from the citation (2) results by averaging
their 25 kVA and 50 kVA transformer data for units with similar voltage to the EDE distribution
© 2012 AREMA
line. (The third harmonic source current is expressed as a percentage of the transformer primary
side base fundamental current in Figure 10. Referencing a ‘base’ value is a common
normalization procedure in power engineering. The base fundamental current is directly
proportional to the rated kVA for a given system voltage). When we used the red curve in our
model, the resulting third-harmonic current was higher than was recorded by the MDP3 units.
Therefore, we lessened the harmonic current for a given voltage on the transformer to the
characteristic shown by the lower ‘black’ curve, which resulted in third harmonic distribution
line current that better approximated our measured values.
These data suggest that for a cluster of transformers, the total third harmonic source current is the
same as for one transformer having a kVA rating which is the sum of the cluster kVA rating.
Therefore for a given modeled load condition, we calculated the harmonic current supplied to the
distribution line due to all of the load clusters by the following steps:
The distribution line voltage at each load-cluster location was calculated using the
fundamental-frequency model, based on the MDP3 kW and kVAR measurements.
The calculated line voltage at each load-cluster was compared to the rated line voltage to
form a Percent Rated Voltage as in Figure 10.
The base fundamental current for each cluster was calculated, based on the rated kVA of
the cluster.
The trend line curve equation of Figure 10 was used to calculate the third harmonic
source current as a percentage of the base current for each load cluster.
An ideal harmonic current source value was calculated for each cluster and was
connected at the cluster impedance location in the model.
© 2012 AREMA
The model was exercised at the third harmonic frequency to calculate the harmonic
current flow all along the distribution line.
The harmonic current from all the cluster locations tends to flow toward the relatively low
impedance of the substation transformer. The harmonic current flow is influenced by:
The load impedance of each load cluster, which provides a parallel path for the harmonic
current, so all the harmonic current does not flow toward the substation.
The voltage on the line, which controls the sources of current as in Figure 10.
The capacitor banks which tend to form a resonant tuned circuit with the distribution line
conductor impedance and the substation impedance.
Figure 9 is an output from the Dranetz monitor of the third harmonic rail voltages at MP 324.8.
The figure also shows the model-calculated voltages on the east side of the IJ for the 1500 hour
of 7-26-10 and the 0300 hour on 7-27-10 as green bars. The calculated relative “minimum“
third-harmonic frequency rail voltage is somewhat higher than measured, but the relative
“maximum” value compares well to the measured values.
The basic trends of the model tend to correlate well with the measurements, such that the model
was used to investigate the effects of making mitigative changes to the systems.
© 2012 AREMA
Figure 10. Estimated Distribution Transformer Primary Third Harmonic Current Source
vs. Voltage
ALTERNATIVE MITIGATION METHODS
Mitigation with Tuning Reactor
The major portion of the load and harmonic sources are located east of the parallel with the track,
that is east and north of the three MDP3 locations. We have labeled that as Region 3 earlier in
the discussion. The current from those sources flows through the region of the distribution line
that parallels the track, with the substation as a sink for the current because of its low impedance
relative to other impedances along the line. The harmonic current flow through the region in
parallel with the track is enhanced by the presence of the two capacitor banks, one of which is
© 2012 AREMA
also in Region 3, which tends to form a resonance with the line impedance on the substation side
of the capacitors.
It was reasoned that the harmonic currents from Region 3 might be prevented from flowing
through the region parallel to the track if a low harmonic impedance was to be placed east of the
parallel exposure region. The fixed capacitor bank that is east of the parallel exposure can be
tuned with an inductor to provide a low-impedance to ground for the third harmonic. Figure 11
is a sketch of an arrangement of a tuning reactor that is connected between the common leg of
the capacitor bank and neutral to form a low impedance series resonant circuit at the third
harmonic frequency for all three phases.
A reactor was added at the fixed capacitor location in the model (see Figure 2 for the fixed
capacitor location), which resulted in a significantly lower calculated third harmonic frequency
current in the exposure region.
© 2012 AREMA
Phase
A B C
N
Figure 11. Sketch of Reactor and Capacitor Bank.
The calculated rail-ground V on the east side of the MP 324.8 insulated joint, with the tuning
reactor included in the model, is less than 0.25 volts compared to the calculated value of
approximately 16 volts without the tuning reactor, as was shown in Figure 9. Thus, the use of a
tuning reactor at the fixed capacitor bank location is expected to provide an effective mitigation
of the third harmonic currents developed in the distribution line. The reactor has no effect on the
fundamental line voltage profile. The calculated fundamental current through the reactor is
small, approximately 1 ampere.
Empire District Feed to Region 3 - Revision
Empire District was considering system modifications that would feed the region north of the
fixed capacitor bank (Region 3 as described in this paper, see Figure 2) from Joplin rather than
from the existing substation south of the exposure in Figure 2. We modeled that arrangement by
breaking each phase conductor just north of the fixed capacitor bank to isolate Region 3 from the
region of parallel. The distribution line conductors at the far north end of the model were
© 2012 AREMA
supplied by a set of fundamental source voltages to simulate the feed from the North. The
neutral was made common between the North (Region 3), and the original substation. The
resultant model was exercised to calculate the third harmonic current flow along the distribution
line for the ‘worst-case’ loading condition. The worst case loading condition for the distribution
line for generation of harmonics is expected to be for light load, with the capacitor banks “in”.
The automatic voltage control of the switched capacitor bank would probably remove that
capacitor bank for very light loading conditions. However, for worst-case harmonic modeling
purposes we have included both capacitor banks for this analysis. The light load results in
higher line voltage,
less resistive loading in parallel with the capacitor banks, that is, less alternative paths for
the harmonic current sources, and
less positive VARS to subtract from the capacitive VARS, resulting in more net
capacitive VARS, which is expected to reduce the resonant frequency to be closer to the
third harmonic frequency
The calculated third harmonic rail to ground voltage on the East side of the MP 324.8 IJ is
approximately 1 volt (for 30 ohm ballast) and is 1.3 volts for 100-ohm ballast for the modeled
‘worst-case’ loading. Although not analyzed, we expect that the induced harmonic track voltage
would be less for more realistic loading conditions.
© 2012 AREMA
CONCLUSIONS
The principal purpose of the investigation was to identify the source of the high level of power-
system harmonic-frequency interference that was observed on a BNSF track and to investigate
possible methods of mitigation including remedial measures for the EDE distribution line that
parallels the track.
In pursuit of those goals, relevant measurements were made on both the track and power system
using data logging instrumentation. The measured data strongly suggested that the primary
source of harmonic coupling to the track was the non-linear characteristics of the distribution line
transformers. The measured data were used to develop a computer model of relevant portions of
both the power and railroad systems, which provided calculated parameters that are substantially
in agreement with measured values over a range of system operating conditions. The model used
transformer non-linear test data from the literature to calculate equivalent harmonic source
current values at the location of clusters of transformers along the distribution line.
The model was used to evaluate system parameters for modified system conditions including
possible mitigative measures. Use of the model to evaluate possible mitigative measures shows:
The use of a tuning reactor at one of the existing capacitor banks is calculated to reduce
the third harmonic induced rail voltage by more than 95% for a range of power-system
loading conditions, including the ‘worst-case’ light loading condition.
© 2012 AREMA
System modifications being contemplated by EDE for other purposes were modeled and
result in a calculated reduction of the third harmonic induced rail voltage by
approximately 95%.
EDE modified the distribution line feed to the region as described above, in mid-2011. The
BNSF also relocated the MP 324.8 signal and IJ’s approximately 800 ft to the north, beyond the
normal extent of the crossing approach. No additional service disruptions to the railroad
operation have been reported since those modifications.
Figure Titles
Figure 1. Sketch of Railroad and Power System near Interference-Affected Crossing. ................................................
Figure 2. Sketch of Distribution System Near Substation ...............................................................................................
Figure 3. MDP Monitors Being Placed on Distribution Line. ........................................................................................
Figure 4.Measured kW & kVAR at Location 1. ..............................................................................................................
Figure 5. Measured kW & kVAR at Location 2. .............................................................................................................
Figure 6. Measured kW & kVAR at Location 3. .............................................................................................................
Figure 7. Phase Current at MDP3 Location 3 - Two Day Period. ...................................................................................
Figure 8. Third harmonic (180 Hz) Line Current at MDP3 Location 3 - Two Day Period .............................................
Figure 9. Measured Third Harmonic Rail-Ground Voltage at MP 3248 IJ. ....................................................................
Figure 10. Estimated Distribution Transformer Primary Third Harmonic Current Source vs. Voltage ............. Figure 11. Sketch of Reactor and Capacitor Bank. ..........................................................................................................
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
INDUCTIVE COORDINATION OF A POWER DISTRIBUTION LINE AND RAILROAD SIGNALED GRADE
CROSSING
Marvin Frazier - Corr Comp Co. David W. McCord - McCord Engineering
James G. LeVere - BNSF Railway Company David Oswald - Empire District Electric Co
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
1850' 790'
PMD-3 267 HZ
SUBSTATION
30' NOMINAL
POWERLINE
RAILROAD
STRAITST.
CROSSING
SIGNALSWITH IJ'S,
180 HZ SHUNT & TJC'S
NARROWBAND JOINT COUPLERS AROUND IJ’S AT A SIGNAL IN APPROACH ARE FAILING PREMATURELY
HARMONICS OF 60 HZ (PRINCIPALLY 180 HZ) ON THE RAILS APPEAR TO BE CAUSING SPORADIC FALSE ACTIVATIONS OF PMD-‐3R PREDICTOR DEVICE AT CROSSING.
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
WHEN EMI IS PRESENT, IT IS OFTEN ERRONEOUSLY BLAMED
FOR PROBLEMS. TROUBLESHOOTING FOR OTHER CAUSES MUST BE DONE PRIOR TO STARTING AN EMI STUDY.
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
TO ACCURATELY MODEL AND ANALYZE THE EMI, THE FOLLOWING MUST BE KNOWN:
1. PHYSICAL LAYOUT OF RAILROAD AND POWER LINE
2. POWERLINE CHARACTERISTICS
3. AFFECTED RR EQUIPMENT CHARACTERISTICS
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Arrangement – Power & Track
Substation Track Circ
uit
2.6 m
ile
Not to Scale
Crossing
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Induced Voltage increases proporQonal to exposure length. Rail-‐ground volts highest at ends of the track circuit.
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
PHASE A
PHASE B
PHASE C
NEUTRAL
MAJORITY OFRETURN
CURRENT IN NEUTRAL
Y-‐CONNECTED 3 PHASE TRANSFORMER AT STATION
SINGLE PHASE LOADS WITH NEUTRAL RETURN
FIXED CAPACITOR
BANK
SWITCHED CAPACITOR
BANK
CAPACITOR BANKS ARE ADDED TO IMPROVE PHASE ANGLE BY BALANCING INDUCTIVE LOADS
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
60 HZ INDUCTION FROM 3 PHASES TEND TO CANCEL EACH OTHER IF DISTANCE AND CURRENT ARE NEARLY EQUAL
RESULTANT (UNCANCELLED) INDUCTION
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
THIRD HARMONIC INDUCTION IN ALL WIRES WILL ADD TOGETHER
RESULTANT INDUCTION
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
69 KV 3 PHASE OVERBUILD TRANSMISSION LINE LINE
SUSPECT 12 KV UTILITY LINE
FIXED CAPACITOR
BANK
TYPICAL POLE WITH ADDED SERVICE TRANSFORMER AND CAPACITOR BANK.
GROUNDED NEUTRAL LINE
SINGLE PHASE SERVICE STEP-‐DOWN TRANSFORMER
CAPACITOR BANK WITH CUTOUT SWITCHES (1 CAPACITOR AND SWITCH FOR EACH PHASE)
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
A LASER RANGE FINDER WAS USED TO MEASURE WIRE HEIGHT AND DISTANCE FROM TRACK.
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
CROSSING DETECTOR IS A 267 HZ PMD-‐3R WITH 8 KHZ ISLAND
1850' 790'
PMD-3 267 HZ
SUBSTATION
30' NOMINAL
POWERLINE
RAILROAD
STRAITST.
CROSSING
SIGNALSWITH IJ'S,
180 HZ SHUNT & TJC'S
HIGH EMI DUE TO LONG EXPOSURE
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
TEMPORARY FIX: SHORTEN APPROACH TO ISOLATE HIGH INDUCTION AREA
(REDUCE TRAIN SPEED)
1850'
PMD-3 267 HZ
SUBSTATION
30' NOMINAL
POWERLINE
RAILROAD
STRAITST.
CROSSING
REMOVETJC'S
MOVE TUNED SHUNT
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
PRELIMINARY CALCULATIONS USED EMI MEASURED WITH A FREQUENCY
SELECTIVE VOLTMETER
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
TO ACCURATELY MODEL AND ANALYZE THE SOURCE AND POSSIBLE MITIGATION OF EMI, WE NEED TO KNOW: • THE BALLAST RESISTANCE • GROUND CONDUCTIVITY • EMI FROM THE LINE
• RAIL-TO-GROUND AND RAIL-TO-RAIL VOLTAGES • CURRENT AND HARMONICS IN EACH PHASE OF THE LINE WHILE RAIL VOLTAGES ARE MEASURED
VARIABLES SHOULD BE RECORDED OVER A TIME PERIOD
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Track Data Logging at IJ’S on Each End of Track Circuit
• Induced Rail to Ground Voltage – Dranetz 4400 Power Quality Meters
• Ballast Resistance Estimate – ElectroCode Voltage & Current – DATAQ Model 718B Data Loggers
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Track Data Logging at 2 IJ Locations
– DATAQ Model 718B Data Loggers with sample interval timer
– Dranetz 4400 Power Quality Meter
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Ballast Resistivity from EC Pulses Measured with DATAQ Recorder
Output
Input
EMI HARMONICS
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
POWER LINE Data Logging
• RMS Current • Power (kW,kVAR, kVA & PF) • Waveforms • Total Harmonic Distortion (THD) • Harmonics (1-32)
MPD-3 RECORDERS WERE HUNG ON POWER WIRES AT THREE LOCATIONS. MPD-3’S HAVE INTERNAL BATTERY AND DOWNLOADABLE DATA STORAGE. THEY RECORD:
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
HANGING MDP-‐3 RECORDER USING A “HOT STICK”
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
ONE MDP-‐3 RECORDER PER PHASE AND NEUTRAL
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Log Power and Track Parameters
Substation Track Circ
uit
2.6 m
ile
Switched Cap
Not to ScaleFixed Cap
MDP3 Location 1
MDP3 Location 2
MDP3 Location 3
CrossingLog Rail Voltage at IJ Locations
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
MDP-LOCATION 1 60-Hz Current
1 DAY
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Compare Harmonic Line Current & Rail Voltage
Rail 3 180 Hz Voltage
20 15 10 5 0
20 15 10 5 0
Line 180 Hz Current
C phase
B phase
A phase
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Distribution Line Currents – 2Day Fundamental Current (60 Hz)
Third Harmonic Current (180 Hz)
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Measurements Showed
Day Night
Fundamental Line Currents
Third Harmonic Line Currents
Induced Rail Harmonic Voltage
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Analysis & Modeling Objectives
• Compare to Measurements • Evaluate Harmonic Sources • Evaluate Mitigation Options
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Measurement Results Suggest
• Harmonics not Caused by Loads – Load Harmonic Values Increase with Load
• Harmonics Higher for Light Loads • Light Loads Result in Higher Line
Voltage • Higher Line Voltage Causes Higher
Transformer Harmonic Current • Nonlinear Transformer Model Needed
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Transformer Third Harmonic – Ell et al Tests
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
223 Transformers on Line
Region 1 Region 3
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Model
• Transformers (Loads) Located Along Each Phase Realistically
• Nearby Transformers Grouped into Clusters
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Transformer Load Model
• Circuit at Transformer Locations
• Element Values by Measured KW & KVA
• Solve for Line Voltage at Each Location
• Harmonic Current Source Value set by Line Voltage
Line
Harmonic Current Source
Neutral
R
L
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
MODELING STEPS –at Two Time Periods
1. Power ( real & reactive) in 3 Regions – From MPD-3 Data – All Loads Same Power Factor & Percent
of Transformer Rating
2. Calculate Voltage Along Line 3. Voltage-Dependent Third Harmonic
Current Sources 4. Calculate Rail-Induced Harmonic
Voltage
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
MPD-3 LOCATION 1 kW & kVAR Measured and Model
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
MPD-3 LOCATION 2 kW & kVAR Measured and Model
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Phase Current – Measured and Model at MDP Location 2
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Calculated Line Voltage Profile 7-26-10 @ 1500 hr. - High Load
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Calculated Line Voltage Profile 7-27-10 @ 0300 hr. – Low Load
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
THIRD HARMONIC LINE CURRENT
RR Parallel
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
HARMONIC CURRENT TO SUBSTATION
SubstationImpedance
LineImpedance
QI
wQ = L/R
Source Current I
3
3
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Third Harmonic Track Voltage
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
TWO MITIGATION OPTIONS ANALYZED
OBJECTIVE – REDUCE HARMONIC CURRENT IN PARALLEL REGION 1. “Tune” Capacitor Bank to Low
Impedance 2. Alternative Power Feed Arrangement
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
1. TUNED CAPACITOR BANK
Source Current I
SubstationImpedance
LineImpedance
IL<I
3
3
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
THREE PHASE CAP BANK TUNING
PhaseA B C
N
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
TUNED CAPACITOR BANK CALCULATED HARMONIC CURRENTS
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
2. ALTERNATIVE POWER FEED ARRANGEMENT
Substation Track Circ
uit
2.6 m
ile
Not to Scale
Crossing
New Power Feed to Region
Switch
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
1. “Tune” Capacitor Bank to Low Impedance
2. Alternative Power Feed Arrangement
• Calculated Rail Voltage Reduction – Over 90% Either Option
TWO MITIGATION OPTIONS ANALYZED
© 2012 AREMA
September 16-19, 2012 Chicago, IL
2012 Annual Conference & Exposition
Results
• Power Company : – Implemented Option #2
• Railroad: – Moved IJ to End of Crossing Approach
• No Grade Crossing Problems Reported Since Modifications
© 2012 AREMA