INDUCTIVE COORDINATION STUDY OF A POWER DISTRIBUTION … · 2017-05-08 · INDUCTIVE COORDINATION...

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



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



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



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



Arrangement – Power & Track

Substation Track Circ

uit

2.6 m

ile

Not to Scale

Crossing

© 2012 AREMA



Induced Voltage increases proporQonal to exposure length. Rail-‐ground volts highest at ends of the track circuit.

© 2012 AREMA



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



60 HZ INDUCTION FROM 3 PHASES TEND TO CANCEL EACH OTHER IF DISTANCE AND CURRENT ARE NEARLY EQUAL

RESULTANT (UNCANCELLED) INDUCTION

© 2012 AREMA



THIRD HARMONIC INDUCTION IN ALL WIRES WILL ADD TOGETHER

RESULTANT INDUCTION

© 2012 AREMA



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



A LASER RANGE FINDER WAS USED TO MEASURE WIRE HEIGHT AND DISTANCE FROM TRACK.

© 2012 AREMA



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



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



PRELIMINARY CALCULATIONS USED EMI MEASURED WITH A FREQUENCY

SELECTIVE VOLTMETER

© 2012 AREMA



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



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



Track Data Logging at 2 IJ Locations

– DATAQ Model 718B Data Loggers with sample interval timer

– Dranetz 4400 Power Quality Meter

© 2012 AREMA



Ballast Resistivity from EC Pulses Measured with DATAQ Recorder

Output

Input

EMI HARMONICS

© 2012 AREMA



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



HANGING MDP-‐3 RECORDER USING A “HOT STICK”

© 2012 AREMA



ONE MDP-‐3 RECORDER PER PHASE AND NEUTRAL

© 2012 AREMA



Log Power and Track Parameters


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



MDP-LOCATION 1 60-Hz Current

1 DAY

© 2012 AREMA



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

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Distribution Line Currents – 2Day Fundamental Current (60 Hz)

Third Harmonic Current (180 Hz)

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Measurements Showed

Day Night

Fundamental Line Currents

Third Harmonic Line Currents

Induced Rail Harmonic Voltage

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Analysis & Modeling Objectives

•  Compare to Measurements •  Evaluate Harmonic Sources •  Evaluate Mitigation Options

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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

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Model

•  Transformers (Loads) Located Along Each Phase Realistically

•  Nearby Transformers Grouped into Clusters

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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



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



TWO MITIGATION OPTIONS ANALYZED

OBJECTIVE – REDUCE HARMONIC CURRENT IN PARALLEL REGION 1.  “Tune” Capacitor Bank to Low

Impedance 2.  Alternative Power Feed Arrangement

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2. ALTERNATIVE POWER FEED ARRANGEMENT


uit

2.6 m

ile

Not to Scale

Crossing

New Power Feed to Region

Switch

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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



Results

•  Power Company : –  Implemented Option #2

•  Railroad: – Moved IJ to End of Crossing Approach

•  No Grade Crossing Problems Reported Since Modifications

© 2012 AREMA

INDUCTIVE COORDINATION STUDY OF A POWER DISTRIBUTION … · 2017-05-08 · INDUCTIVE COORDINATION...

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