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Distance Protection Settings in Electrical Railway Systems with Positive and

Negative Feeder

Conference Paper · July 2006

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Reza Ganjavi Rainer Krebs

Siemens AG, Germany Siemens
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 Distance Protection Settings in Electrical Railway Systems
with Positive and Negative Feeder

M. R. Ganjavi, Dr.-Ing R. Krebs Prof. Dr.-Ing. habil. Z. Styczynski

SIEMENS AG, PTD SE PT5 OTTO-VON-GUERICKE-UNIVERSITY MAGDEBURG
P.O.Box: 3220, D-91050 Erlangen Faculty of Electrical & Information Technology
Germany Universitätsplatz 2, D-39106 Magdeburg
rainer.krebs@siemens.com, Germany
mohammad-reza.ganjavi@siemens.com Zbigniew.Styczynski@E-Technik.Uni-Magdeburg.DE

Abstract: - Electric railway systems have complex configurations of overhead lines, protected by distance
relays. The protection philosophy for this system considers low cost maintenance, control and protection in
autotransformer stations and advanced control and protection in supply stations.
The paper discusses some heuristic rules for settings of distance relays in railway systems with positive and
negative feeder configurations. The experience is formulated as a set of rules (if condition then effect) and stored
in an expert system for fast access.

Key-Words: - Expert System, Traction Supply, Catenary Protection

1 Introduction Negative Feeder: The negative feeder operates with

Negative and positive feeder arrangement is an voltage -Vs via the autotransformers according to the
overhead contact line system [2] for energizing trains Fig. 1. Most of the current feeding the train will
with AC voltage (see Fig. 1). In this system, there are return to the supply station by the negative feeder and
two traction supply station at the beginning and end not by the tracks.
of each track and there are several autotransformer
stations between supply stations. There are two or Return Circuit: The return circuit is the total
more main railway tracks between supply stations interconnected system consists of the track,
and sometimes there are local tracks at each earth-system conductor, earth grid and earth itself.
autotransformer station. Supply stations provide
single-phase a.c. medium voltage to positive and 2 Electric Railway System Protection
negative feeders with 180 degree phase difference. The electric railway system consists of positive,
At each autotransformer station all positive feeders, negative and return circuit will be protected by
all negative feeders and all railway tracks are distance relays in supply stations.
connected to an autotransformer via positive busbar, The trip command is connected to the double phase
negative busbar and earth busbar respectively. In circuit breaker, which disconnects both of the
addition positive feeders are designed to provide positive and negative feeders.
enough energy to trains but negative feeders are The measuring quantities for the distance protection
designed to compensate voltage drop of positive relays installed in each supply station are as follows:
feeder via autotransformer stations. Therefore, the
current flows in positive and negative feeders are not a) Voltage: positive busbar voltage according to the
balanced during and after acceleration of trains. Fig. 1.
As mentioned, in this system three sets of conductors b) Current: Sum of the positive and negative feeder
per railway track exist. currents. The measured current will be summed
by secondary connection of the corresponding
Positive Feeder: The positive feeder is the total current transformers. The relay current is as
interconnected system consists of contact or catenary follows:
wire and mechanical tension wires. Ii is directly
feeding the train via the contacted pantographs. It I relay = I pos + I neg (Eq. 1)
operates with a voltage Vs for example 25kV and
50Hz. An example for an electric railway system with two
main tracks (Track 1 and Track 2) and two side tracks
 Fig. 1. Simplified Overhead Contact Line system with negative feeder arrangement

Fig. 2. Two traction supply stations and six autotransformer stations for energizing two railway tracks
Amper
TSS1

TSS1

Relay Input
Currents

Feeder E Feeder G

AT 1a

AT1b
AT 2a
Feeder G, H
AT 3a
Feeder E,F AT 4a AT 5a

AT1b

TSS1
Feeder H
Feeder J, N Feeder J, N

Feeder F Fig.3. Distance relays measured currents for faults on the Track 2 in Fig. 2.
(The result is generated by SITRAS® SIDYTRAC program.)
(Track 3 and Track 4) with two supply station (TSS 1 the autotransformer stations. This leads to decrease in
and TSS 2) and six autotransformer station (AT 1a to the measured impedance by these relays. (see Fig. 4)
AT 5a and AT 1b) is shown in Fig. 2.
TSS 1 Feeders G and H supplies the Track 1 and In addition, Fig. 3 shows that the measured fault
Track 2 toward right side of the TSS 1 station. These current of Feeder J and N becomes zero for a fault
feeders are equipped with negative feeders. location on the Track 2. Therefore the relays
TSS 1 Feeders E and F supplies the Track 1 and measures very high impedance and will not pickup to
Track 2 toward left side of the TSS 1 station. These clear the fault.
feeders are equipped with negative feeders.
TSS1 Feeders J and N supplies the side tracks Trak 3 During normal operation the measured current by the
and Track 4 toward left side of the TSS 1. relay is equal to the train load current. And during
The supply station TSS 1 is normally in operation. short-circuit between positive or negative feeder to
The supply station TSS 2 comes into operation for ground, the relay current is equal to the short-circuit
emergency situation alone or in parallel with TSS 1. current.
During normal operation, if a short-circuit between However the relay measured impedance is not
Track 2 and positive feeder happens then all distance directly proportional to the distance-to-fault caused
relays at Feeder E, F, G, H, J and N measures by following facts [3]:
abnormal currents as all positive feeders, all negative
feeders, along with all autotransformers are in a) The current injection effect and impedance of
parallel. Fig. 3 shows the measured current of Feeder autotransformers along the tracks.
E, F, G, H, J, N as the short-circuit location moves b) Parallel connection of positive feeders of all
along the track 2. parallel tracks.
The correct setting of distance relay should trip the c) Parallel connection of negative feeders of all
fault selectively with Zone 1 or Zone 2 of the distance parallel tracks.
relays at relevant feeders according to the following c) Back-infeed effect of autotransformers located
scheme: behind the regarded supply station.
d) Additional infeed effect of supply systems behind
For example for a fault on main track (Track 2) or front of the regarded supply station.
between supply station TSS 1 and TSS 2 the distance e) Different impedances per line length for positive
relay at Feeder G should trip with Zone 1 or Zone 2. and negative feeders.
The distance relay at Feeder H should trip with Zone f) Side tracks with lower priority are not equipped
2. In this way, the TSS 2 and autotransformer with negative feeders. Therefore, the fault current
stations AT 1a to AT 5a are de-energized. Then measured by side track relays becomes zero for
undervoltage relay in these stations will disconnect specific short-circuits located on the main track.
these stations from positive and negative feeders in ZONE 2 Reach
around 2.0 seconds. Later, the autoreclose function in 12
AT 5a
440
TSS 1 reenergizes the Feeder G and H. Now feeder G AT 5a
440 km

feeds only the Track 2 and feeder H feeds only the 10 km

TSS 2
Track 1. If the fault still exists on the Track 2 then the AT 4a
435.89 Safety
431
km
Feeder G trips again with Zone 1 or Zone 2 and 8 km Margin

remains open. In addition all connection between AT 3a

autotransformer stations and Track 2 remains open. O hm 6 424.24
km

The connection between Track 1 and autotransformer AT 2a

418.80 Safety TSS 2
stations is closed by system operator so that Track 1 AT 1a
4
km Margin 431
412.89 km
returns to normal operation. km

Same scheme should be realized if a fault on a side 2

ZONE 1 Reach

track (Track 3 or Track 4) between TSS 1 and TSS 1

407.4
autotransformer station AT 1b happens. km
0
0 0. 5 1 1. 5 2 2. 5 3 3. 5 4 4. 5 5

O hm

Realization of this scheme confronted with following

difficulties: a) Wi t hout A ut ot r ansf or mer s b) Wi t h A ut ot r ansf or mer s

As Fig. 3 shows the measured fault current of Feeder Fig.4. Proper selection of Zone 1 and Zone 2 for distance
E, F, G, H increases when the fault location is near to relays at feeder G in Fig. 2 considering the effect of
parallel tracks and autotransformers current injection.
 Fig 5. Measured impedance of distance relays at feeder J and N in Fig. 2 considering the absence of negative feeders

3 Distance relays zone 1 settings

In case of fault on main tracks, for example Track 2, And also for following operation conditions:
in Fig. 2 with fault location between TSS 1 and TSS
2, the fault should be cleared by distance relay Zone 1 - All autotransformer are disconnected.
of Feeder G. Curve (a) in Fig. 4 shows the Feeder G - Track 1 and Track are not parallel.
relay measured impedance when a all - All autotransformer are connected.
autotransformers are disconnected, positive and - Supply station TSS1 is in operation
negative feeders of the Track 1 and Track 2 are not - Supply station TSS2 is in operation
parallel to each other. Curve (b) in Fig. 4 shows the
measured impedance in normal operation when the In order to have a selective protection for the distance
Track 1 and the Track 2 are parallel and relay at Feeder G in Fig. 2, its Zone 1 reach should be
autotransformers are in operation. smaller than the supply station TSS2 impedance
As shown in Fig. 4, the observed impedance for a reach measured by the relay.
given fault location in case (b) is approximately half Therefore all of the created R-X planes should be
of the case (a) while the Track 1 and 2 are in parallel. analyzed for finding the minimum impedance reach
In addition, the current injection at each of the autotransformer station AT 4a after the
autotransformer station results a saw-shape drop in saw-shape impedance drop as shown in Fig. 4.
the impedance locus. A safety margin of 10% to 20% can be applied to
have a safe value for Zone 1 reach.
The measured relay impedance in the R-X plane like
Fig. 4, should be created for the following fault Finding the Zone 1 reach for Feeder G distance relay
scenarios by simulation methods (like SITRAS® in Fig. 2, according to the above method, needs vast
SIDYTRAC program or [1]): amount of simulation for creation of R_X phase
plane diagram. During these analyses we have found
- Fault between catenary to running rail the following rule:
- Fault between negative feeder and running rail
- Fault between catenary and negative feeder Zone −1reach = k × Z TSS − remote (Eq. 2)
- No fault but maximum load conditions
 Where: then the distance relays at feeder J trips with Zone 1.
Z TSS −remote Therefore the suggested rule in Eq. 3 remains valid.
: Impedance of one catenary between the
two supply stations (For example between TSS1 and
TSS2 in Fig. 2). 6 Conclusions
The configuration of electric railway systems,
k : The reduction factor between 70±10%. It especially if they are supplied with autotransformers
between positive and negative feeders, is very
considers the autotransformers injection effect and complex.
parallel impedances of positive feeders or negative The used and well known protection principle
feeders between parallel tracks. “distance protection” is facing problems which could
lead to relay malfunction. The nonlinearity between
The Zone 1 needs no delay to send the trip command distance-to-fault and impedance-to-fault is described
to circuit breakers. in the paper. Rules for optimization of distance
Same rule is valid for adjusting distance relay at protection Zone 1 and Zone 2 are proposed.
Feeder H, E, F, J, N in Fig. 2 when a fault on the main For future relay settings calculations, these rules will
tracks or on the side tracks of the left side of TSS 1 be implemented in an existing expert system for
happens. protection coordination.

5 Distance relays zone 2 settings References:

In order to have a selective protection for the distance [1] E. Pilo, L. Rouco, A. Fernandez, and A.
relay at Feeder G in Fig. 2, its Zone 2 reach should be Hernandez, A simulation tool for the design of
higher than the supply station TSS2 impedance reach electrical supply system of high-speed railway
observed by the relay. lines, presented at IEEE PES Summer meeting
The advanced analysis method mentioned in section 2000, Seattle, USA.
four is applicable. However finding the Zone 2 [2] G. Varju, A comparison of the booster
reach, according to the above method, needs vast transformer and auto transformer railway
amount of simulation for creation of R_X phase feeding systems, feeding features and induction to
plane diagram. During these analyses we have found telecom lines, presented at EMC York 2004,
the following simple rule: York, UK.
[3] Ganjavi M.R.; Krebs R.: Catenary’s distance
Zone − 2 reach = k × Z TSS − remote protection in traction supply systems with
(Eq. 3)
negative feeder arrangement, 14th International
Where: Conference on Power System Protection (PSP
2004), pp. 201-210, Bled, Slovenia, September
2004
Z TSS −remote : Impedance of one catenary between the
two supply stations. (For example TSS1 and TSS2 in
Fig. 2)

k : A factor between 170±20%

The Zone 2 should send the trip command to circuit

breakers with 0.4 to 1.0 second delay.
In practice some side tracks parallel to main track has
no negative feeders. Track 3 and 4 in Fig. 2 and 3 are
an example of such tracks.
As Fig. 3 shows, for a given fault location on main
Track 2, the distance relay on Track 3 observes zero
current or infinite impedance. Fig. 5 shows the
corresponding impedance locus of the distance relay
located at feeder J in Fig. 2.
In such a situation distance relays at feeder J will not
pick up. But the distance protection on the main track
at Feeder E and F trips with Zone 1 or 2 correctly and

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