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DESIGN OF 25 KV OVERHEAD EQUIPMENT (OHE) SYSTEM FOR ELEVATED
LINES AND POWER SUPPLY & SCADA
FOR BOTH UNDERGROUND AND ELEVATED LINES INCLUDING CHECKING OF
DESIGN OF
RECEIVING SUBSTATION
AND DESIGN VALIDATION OF DELHI MRTS PHASE III PROJECT LOT I
25 KV TRACTION EQUIPMENT SIZING
CALCULATIONS
January, 18th 2013
.
25 KV Traction Equipment Sizing Calculations
CONTENTS
1. INTRODUCTION ..................................................................................................................... 4
1.1. Reference documentation ................................................................................................ 4
1.2. Abbreviations ................................................................................................................... 5
2. TRACTION TRANSFORMERS .............................................................................................. 6
2.1. Power consumption of TSSs ........................................................................................... 6
2.1.1. Normal operation (5 traction substations working) .................................................... 6
2.1.2. Failure cases .............................................................................................................. 7
2.2. Voltage in pantograph .................................................................................................... 11
2.2.1. Normal operation (5 traction substations working) .................................................. 11
2.2.2. Failure cases ............................................................................................................ 12
2.3. Conclusions .................................................................................................................... 13
3. BOOSTER TRANSFORMERS ............................................................................................. 15
4. 25 KV FEEDERS .................................................................................................................. 19
4.1. Rated current calculation (In) ......................................................................................... 19
4.1.1. Main track ................................................................................................................. 19
4.1.2. Depot Calculation ..................................................................................................... 20
4.2. Calculation with current in case of nominal overload of the transformer (Io) ................. 21
4.3. Voltage drop ................................................................................................................... 23
4.4. Short circuit criteria ........................................................................................................ 23
4.4.1. Simply Single Line Scheme ..................................................................................... 25
4.4.2. Equivalent Single Line Scheme ............................................................................... 25
4.4.3. Impedance Calculations ........................................................................................... 26
4.4.4. Calculation of the continuous current of short circuit (Isc) ....................................... 28
4.4.5. Calculation of the Maximum Current Asymmetric Short-Circuit (Is) ........................ 28
4.4.6. Rupture capacity and connection ............................................................................. 29
4.5. Conductor sizing ............................................................................................................ 29
4.5.1. Type of Conductor .................................................................................................... 29
4.5.2. Size of Conductor ..................................................................................................... 30
5. RETURN CABLES................................................................................................................ 35
5.1. Return cables ................................................................................................................. 35
5.2. Return conductor ............................................................................................................ 35
5.2.1. Rated current calculation (In) ................................................................................... 35
5.2.2. Voltage drop ............................................................................................................. 36
5.2.3. Short circuit criteria .................................................................................................. 36
6. INDUCED VOLTAGE CALCULATION ................................................................................ 36
7. CIRCUIT BREAKERS RATING ............................................................................................ 38
.
25 KV Traction Equipment Sizing Calculations
8. INTERRUPTERS RATING ................................................................................................... 39
9. CURRENT TRANSFORMERS RATING .............................................................................. 40
Annex 1. Technical data of 26/45 kV XLPE insulated copper cable used for
calculation.
Annex 2. Guide for calculation of cable capacity under short time operation
currents.
Annex 3. Technical data of aluminium cables used for calculation.
Annex 4. Rolling stock data used for calculation
25 KV Traction Equipment Sizing Calculations 4
1. Introduction
The present document aims to determine the rating of the equipment foreseen for the 25 kV
traction network in the scope of the design of 25 kV Overhead Equipment (OHE) system for
the Mukundpur Gokulpuri Shiv Vihar section (Line 7) including Mukundpur and Vinod
Nagar Depots.
1.1. Reference documentation
Comparative Study of various Schemes of underground ASS & Recommendations
for DMRC Phase-III.
DMRD. Edition Nov 2011.
Ardanuy-Barsyl. Edition of 17/08/2012
DMRC Project Line 7. Detail Design Consultant. CCDD-1. Traction simulation sizing
study
Ardanuy-Barsyl. Edition of 17/08/2012
25 KV Traction Equipment Sizing Calculations 5
1.2. Abbreviations
DMRC Delhi Metro Rail Corporation Limited
UG Underground (Package, Station or Section)
ELV Elevated (Package, Station or Section)
DPT Depot
ASS Auxiliary Substation
RSS Receiving Substation
TSS Traction Substation
PD Propriety Development
TVF Tunnel Ventilation Fan
TEF Tunnel Emergency Fan
ECS Environment Control System
S&T Signal & Telecommunication
TR Transformer
DG Diesel Generator
CCB Coupling Circuit Breaker
VDE Association of German Electrical Engineers
25 KV Traction Equipment Sizing Calculations 6
2. Traction Transformers
The Traction Simulation Study for the Line 7 extension has been performed by M/s Ardanuy
using RailPower software.
In this chapter the results and main conclusions obtained from the study are included.
2.1. Power consumption of TSSs
Different alternatives have been simulated to get the power consumptions in transformers of
the Tractions Substations. The values have been obtained taking into account these
assumptions:
Total Trip: Mukundpur Shiv Vihar, 57.705 km, 37 stations.
Rolling Stock with 6 coach compositions (DM-T-M-M-T-DM) and full loaded (1,800
people). Total weight of Rolling Stock is 371.25 Tons (Tare weight is 252 Tons, 42
Tons/car).
It is assumed that up to 75% of the power generated by train braking is able to be
regenerated in electrical power by the motors of the train (Regenerative braking
performance will be 0.75).
Braking force will be supplied by the train motor brakes until the maximum engine
brake force for each speed is given. If it is necessary more braking force than the
motor is able to generate, it will be provided by pneumatic brake.
By default, it is considered a value of train power factor of 1.
Auxiliary Power Consumption of trains (according to values provided by DMRC): 33
kVA/car (198 kVA whole train)
Headway of 135 seconds between trains in same direction (what means 68 trains at
same time in the system)
2.1.1. Normal operation (5 traction substations working)
Maximum, average and RMS (maximum RMS value for integration period of 1 hour) power
values for Traction Substations during the peak hour are shown in the following table.
25 KV Traction Equipment Sizing Calculations 7
SIMULATED VALUES OF POWER CONSUMPTION IN TSS
MKPR (KVA)
DH-KN INA VN-NG YMVH
(KVA) (KVA) (KVA) (KVA)
TRF1 TRF1 TRF1 TRF1 TRF1
MAX 19.630 37.103 24.233 32.028 19.422
RMS 12.114 17.219 16.388 17.006 12.625
AVG15 min. 11.146 13.556 15.625 14.875 10.773
AVG5 min. 11.478 14.640 16.072 15.431 11.067
Table 1. Simulated values of power consumption in TSS. Normal operation
According to these values, transformers with nominal power of 40/50 MVA are plenty
dimensioned to feed the whole line present.
The overload conditions that each transformer should be complied are:
Overloads above 150% of nominal power (40 MVA) during less than 15 minutes in a
3 hour cycle.
Overloads above 200% of nominal power (40 MVA) during less than 5 minutes in a 3
hour cycle.
It can be seen the worst case (transformer more loaded) for this simulation is transformer of
Dhaula Kuan TSS. There is not any instant in the simulation when the power is higher than
150% of nominal power (40x1,5 = 60 MVA), therefore both conditions of overloading are
complied.
2.1.2. Failure cases
Feed extensions cases have been simulated, for failures of 1, 2, 3 and 4 TSS. The worst
case for each type of operation (N-1, N-2, N-3 and N-4) has been simulated.
The following list shows the worst case simulated for each operation mode (the worst case
for each operation mode is the case where the electrical sector fed by 1 TSS is the longest):
N-1 Case. Failure of TSS3 (INA): Dhaula Kuan will feed from Neutral Section in K.P
9+200 to Neutral Section in 34+935.
N-2 Case. Failure of TSS1 (Mukund Pur) and TSS2 (Dhaula Kuan): INA will feed
from dead end of the line (Mukund Pur Station) to K.P. 34+845.
25 KV Traction Equipment Sizing Calculations 8
N-3 Case. Failure of TSS1 (Mukund Pur), TSS2 (Dhaula Kuan) and TSS3 (INA):
Vinod Nagar will feed from dead end of the line (Mukund Pur Station) to K.P. 48,685.
N-4 Case. Failure of TSS2 (Dhaula Kuan), TSS3 (INA), TSS4 (Vinod Nagar) and
TSS5 (Yamuna Vihar): Mukund Pur will feed the whole line
Simulations for feed extension cases have been realized taking into account the following
headways:
Case Headway.
Case N-1 135 seconds
Case N-2 240 seconds
Case N-3 480 seconds
Case N-4 1,200 seconds
Table 2. Headway for failure cases
CASE N-1: FAILURE OF TSS3 (INA)
In this case, Dhaula Kuan will be feeding from Neutral Section in K.P 9+200 to Neutral
Section in 34+935. The rest of the line will be fed as normal operation case.
FAILURE OF INA TSS
-0+680 MKPR
TSS
9+200 SP
17+045 DH-KN
TSS
34+935 SP
42+140VN-NG
TSS
48+775 SP
54+000YMVH
TSS
Figure 1 Case N-1. Failure of TSS3 (INA)
SIMULATED VALUES OF POWER CONSUMPTION IN TSS
MKPR (KVA)
DH-KN (KVA)
VN-NG (KVA)
YMVH (KVA)
TRF1 TRF1 TRF1 TRF1
MAX 19.630 54.085 32.028 19.422
RMS 12.114 31.826 17.006 12.625
AVG15 min. 11.146 28.252 14.875 10.773
AVG5 min. 11.478 29.627 15.431 11.067
Table 3. Simulated values of power consumption in TSS. Case N-1
25 KV Traction Equipment Sizing Calculations 9
The worst case for this simulation is the transformer of Dhaula Kuan TSS. In order to comply
with criteria of overload above 150% during less than 15 minutes in a 3 hours cycle, the
nominal power of this transformer will be dimensioned for 40 MVA.
CASE N-2: Failure of TSS1 (Mukund Pur) and TSS2 (Dhaula Kuan)
In this case, headway of 4 minutes has been taken into account. INA will be feeding from
dead end of the line (Mukund Pur Station) to K.P. 34+845. The rest of the line will be fed as
normal operation case.
FAILURE OF MUKUND PUR AND DHAULA KUAN TSS
25+400 INA
TSS
34+935 SP
42+140VN-NG
TSS
48+775 SP
54+000YMVH
TSS
Figure 2. Case N-2. Failure of TSS1 (Mukundpur) and TSS2 (Dhaula Kuan)
SIMULATED VALUES OF POWER CONSUMPTION IN TSS
INA VN-NG YMVH
(KVA) (KVA) (KVA)
TRF1 TRF1 TRF1
MAX 52.217 15.360 16.613
RMS 26.356 11.453 8.412
AVG15 min. 23.080 9.207 6.581
AVG5 min. 25.082 10.494 7.366
Table 4. Simulated values of power consumption in TSS. Case N-2
The worst case for this simulation is the transformer of INA TSS. In order to comply with
criteria of overload above 150% during less than 15 minutes in a 3 hours cycle, the nominal
power of this transformer will be dimensioned for 40 MVA.
CASE N-3: Failure of TSS1 (Mukund Pur), TSS2 (Dhaula Kuan) and TSS3 (INA)
In this case, headway of 8 minutes has been taken into account. Vinod Nagar will be feeding
from dead end of the line (Mukund Pur Station) to K.P. 48,685. The rest of the line will be fed
as normal operation case.
25 KV Traction Equipment Sizing Calculations 10
FAILURE OF MUKUND PUR AND DHAULA KUAN AND INA TSS
42+140VN-NG
TSS
48+775 SP
54+000YMVH
TSS
Figure 3. Case N-3. Failure of TSS1 (Mukundpur), TSS2 (Dhaula Kuan) and TSS3 (INA)
SIMULATED VALUES OF POWER CONSUMPTION IN TSS
VN-NG YMVH
(KVA) (KVA)
TRF1 TRF1
MAX 34.550 10.473
RMS 19.605 4.864
AVG15 min. 16.523 3.668
AVG5 min. 17.910 4.201
Table 5. Simulated values of power consumption in TSS. Case N-3
The worst case for this simulation is the transformer of Vinod Nagar TSS. In order to comply
with criteria of overload above 150% during less than 15 minutes in a 3 hours cycle, the
nominal power of this transformer will be dimensioned for 40 MVA.
CASE N-4: Failure of TSS2 (Dhaula Kuan), TSS3 (INA), TSS4 (Vinod Nagar) and TSS5
(Yamuna Vihar)
In this case, headway of 20 minutes has been taken into account. Mukund Pur will be
feeding the entire line.
FAILURE OF DHAULA KUAN, INA, VINOD NAGAR AND YAMUNA VIHAR TSS
-0+680 MKPR
TSS
Figure 4. Case N-4. Feeding from TSS1 (Mukundpur)
25 KV Traction Equipment Sizing Calculations 11
POWER CONSUMPTION IN TSS
MKPR (KVA)
TRF1
MAX 22.458
RMS 10.910
AVG15 min. 8.854
AVG5 min. 9.768
Table 6. Simulated values of power consumption in TSS. Case N-4
In order to comply with criteria of overload above 150% during less than 15 minutes in a 3
hours cycle, the nominal power of the Mukumpur SST transformer will be dimensioned for 40
MVA.
2.2. Voltage in pantograph
2.2.1. Normal operation (5 traction substations working)
Voltage in the train pantographs have been calculated considering Normal Operation of
electrification system (5 Traction Substations working at same time).
For this calculation the following has been taken into account:
Value of lump impedance of the catenary system
25 kV feeding cable impedance
Exit voltage at the electrical traction substations
Exit current at the substations
Current consumed by each train, which will correspond to the results of the
simulations
Location of the substations and neutral sections
The voltages presented below are the maximum and minimum that can be produced on the
pantograph with the foreseeable circulation graph (headway of 135 seconds).
25 KV Traction Equipment Sizing Calculations 12
VOLTAGE IN TRAIN PANTOGRAPH
DIRECTION MIN
(V)
MAX
(V)
AVG
(V)
MUKUNDPUR SHIV VIHAR 26,563 27,939 27,332
SHIV VIHAR - MUKUNDPUR 26,517 28,150 27,341
Table 7. Voltage in train pantograph. Normal operation
For normal operation, minimum voltage in the line is 26,517 V, over the threshold
established in the normative EN 50163 Railway applications - Supply voltages of traction
systems, for traction systems of AC 25 kV (Umin1 = 19,000 V).
2.2.2. Failure cases
Except in the case of N-1, the headway between trains should increase as shown below to
assure that the voltage drop in the pantograph trains complies with the values established in
norm EN 50163 (where Umin1 = 19,000 V):
Case Headway.
Case N-2 4 minutes
Case N-3 8 minutes
Case N-4 20 minutes
Table 8. Headway for N-2, N-3 and N-4 failure cases.
In the following table, values of voltage in the train pantographs are shown for the different
cases of feed extensions.
VOLTAGE IN TRAIN PANTOGRAPH
CASE DIRECTION MIN (V) MAX (V) AVG (V)
CASE N-1: FAILURE TSS3
FEED FROM TSS2
DW LINE 25,550 27,939 27,138
UP LINE 25,681 28,150 27,134
CASE N-2: FAILURE TSS1 AND TSS2
FEED FROM TSS3
DW LINE 19,737 28,054 26,979
UP LINE 22,859 28,333 27,084
25 KV Traction Equipment Sizing Calculations 13
VOLTAGE IN TRAIN PANTOGRAPH
CASE DIRECTION MIN (V) MAX (V) AVG (V)
CASE N-3: FAILURE TSS1,TSS2 AND TSS3
FEED FROM TSS4
DW LINE 20,159 28,082 26,691
UP LINE 23,337 28,130 26,800
CASEN N-4: FAILURE TSS2, TSS3, TSS4 AND
TSS5
FEED FROM TSS1
DW LINE 20,478 28,535 26,668
UP LINE 21,027 28,420 26,615
Table 9. Voltage in train pantograph. Failure cases
In N-1 situation, the minimum value of voltage in train pantograph is 25,550 V. This value is
over the threshold established in the normative EN 50163 (where Umin1 = 19,000 V)
In N-2 situation, the minimum value of voltage in train pantograph is 19,737 V. This value is
over the threshold established in the normative EN 50163 (where Umin1 = 19,000 V)
In N-3 situation, the minimum value of voltage in train pantograph is 20,159 V. This value is
over the threshold established in the normative EN 50163 (where Umin1 = 19,000 V)
In N-4 situation, the minimum value of voltage in train pantograph is 20,478 V. This value is
over the threshold established in the normative EN 50163 (where Umin1 = 19,000 V)
2.3. Conclusions
Main conclusions obtained for the study are summarized below:
From electrical simulations, it can be deduced that 40/50 MVA transformers are
sufficiently dimensioned to support headway of 135 seconds with the model of train
considered and the 5 substations working at normal operation.
There are no overloads exceeding 50% in any of the transformers of 40/50 MVA
(nominal power value).
From the simulations of failure of one of the Traction Substations (feed extensions
cases) it can be deduced for the worst case will be failure of INA TSS. In this case
the transformers of 40/50 MVA (Dhaula Kuan TSS) comply with the criteria of
overload.
With respect to drop voltage along the line, for cases simulated the voltages in train
pantographs are over the threshold established in the normative EN 50163 Railway
applications - Supply voltages of traction systems (where Umin1 = 19,000 V)
25 KV Traction Equipment Sizing Calculations 14
From the simulations of failure of more than 1 Traction Substation (feed extension N-
2, N-3 and N-4) headway must be increased in order to reduce the number of trains
and therefore maximum drop voltage along the OCS will be reduced complying with
the values established in norm EN 50163 (where Umin1 = 19,000 V).
With these operation conditions and headways, it can be deduced that for the worst
cases that all transformers will be plenty dimensioned for 40/50 MVA.
25 KV Traction Equipment Sizing Calculations 15
3. Booster Transformers
Currently, in existing lines of DMRC there are two kinds of Booster Transformers, with the
following characteristics:
Nominal Rating 150 kVA 280 kVA
Rated Current and
voltage
366 A at 409 V 500 A at 560 V
Overload rating (15 ms) 550 A 750 A
Impedance at full load at
75 Centigrade
0.15 ohm (Max) 0.15 ohm (Max)
Guaranteed max no load
losses
225 W 350 W
Guaranteed max load
losses
4000 W 6500 W
Table 10. Booster transformers used in DMRC
The maximum current calculated for outgoing feeders for the main line in Line 7 is 439.58 A
according to the electrical dimensioning of the Line 7 simulated with RailPower. This value
of current is the RMS value corresponding to n-2 failure situation (Mukundpur TSS and
Dhaula Kuan TSS failure) for the feeder cable to Down Line at Mukundpur side.
Capacity of booster transformers will be calculated with the expression:
BTRCBT UIS
Where:
SBT = Capacity of the booster transformer (VA).
UBT = Voltage in the booster transformer (V).
IRC = Return current which cross the booster transformer (A)
= Performance of the Booster transformer
25 KV Traction Equipment Sizing Calculations 16
Figure 5. Scheme of operation with Booster transformers
Considering that the voltage of the return conductor in the connection with rails is zero, the
voltage of the booster transformer can be calculated according to the expression:
)( BTRCRCRCBT zLzIU
Where:
UBT = Voltage in the booster transformer (V).
IRC = Return current which cross the booster transformer (A)
ZRC = Impedance per km of the return conductor (ohm/km)
LRC = Length of return conductor between the adjacent connections of RC with the
rail (km).
ZBT = Impedance of the booster transformer (ohm)
Calculating these parameters:
IRC (A) 439.58 From electrical dimensioning of the Line 7
(Maximum RMS value of case N-2)
0.85 Typical value
ZRC (ohm/km) 0.119+j0.402 Calculated from catalogue
LRC (km) 2.6 Maximum distance between two adjacent RC to rail
connections
ZBT (ohm/km) 0.016+j0.078 According calculated in annex 2 of Traction
Simulation Sizing Study
UBT (V) 514.12 Calculated with previous data
Sa (kVA) 265.92 Calculated with previous data
Table 11. Sizing of BT
Therefore, the Booster transformer of 280 kVA can be selected for the worst case.
Nevertheless, taking into account the location of every BT along the line (distance to TSS)
and the distances between adjacent BTs, and considering that every TSS feed the line with
25 KV Traction Equipment Sizing Calculations 17
this value maximum of current, these parameters can be calculated for every booster
transformer and therefore, accurate sizing of every booster transformer can be done.
In the following table these calculations are shown:
BT Ch. imp. Return
feeder (ohm/km)
imp. BT (ohm)
distance connection
rail-RC (km)
RC current
(A)
RC Voltage
(V) (BT
Voltage)
BT Power (kVA)
BT Power (kVA)
BT701 0+214 0.119+0.402i 0.016+0.078i 0.797 369.55 152.82 66.44 150
BT703 6+855 0.119+0.402i 0.016+0.078i 1.465 74.08 51.36 4.48 150
BT705 8+570 0.119+0.402i 0.016+0.078i 1.428 58.28 39.51 2.71 150
BT707 9+710 0.119+0.402i 0.016+0.078i 1.793 28.58 23.74 0.80 150
BT709 12+155 0.119+0.402i 0.016+0.078i 1.909 165.58 145.66 28.37 150
BT711 16+790 0.119+0.402i 0.016+0.078i 1.835 425.29 360.84 180.55 280
BT713 19+289 0.119+0.402i 0.016+0.078i 1.822 240.18 202.48 57.21 150
BT715 20+433 0.119+0.402i 0.016+0.078i 1.352 138.53 89.49 14.58 150
BT717 34+127 0.119+0.402i 0.016+0.078i 1.425 38.01 25.72 1.15 150
BT719 36+700 0.119+0.402i 0.016+0.078i 2.287 107.68 111.77 14.16 150
BT721 38+700 0.119+0.402i 0.016+0.078i 2.270 229.70 236.83 64.00 150
BT723 41+240 0.119+0.402i 0.016+0.078i 2.475 384.67 429.67 194.45 280
BT725 43+650 0.119+0.402i 0.016+0.078i 2.158 339.54 334.06 133.45 150
BT727 45+555 0.119+0.402i 0.016+0.078i 2.084 213.33 203.32 51.03 150
BT729 47+818 0.119+0.402i 0.016+0.078i 2.273 63.40 65.44 4.88 150
BT731 50+100 0.119+0.402i 0.016+0.078i 2.066 111.47 105.40 13.82 150
BT733 51+950 0.119+0.402i 0.016+0.078i 2.103 267.11 256.65 80.65 150
BT735 54+305 0.119+0.402i 0.016+0.078i 2.453 403.94 447.38 212.61 280
BT737 56+855 0.119+0.402i 0.016+0.078i 1.729 105.98 85.21 10.62 150
Table 12. Detailed calculation of Line 7 BTs (Up line)
25 KV Traction Equipment Sizing Calculations 18
According to these calculations it can be sized the booster transformers:
Up line Dn line
Booster
Transformer Capacity (kVA)
Booster
Transformer Capacity (kVA)
BT701 150 BT702 150
BT703 150 BT704 150
BT705 150 BT706 150
BT707 150 BT708 150
BT709 150 BT710 150
BT711 280 BT712 280
BT713 150 BT714 150
BT715 150 BT716 150
BT717 150 BT718 150
BT719 150 BT720 150
BT721 150 BT722 150
BT723 280 BT724 280
BT725 150 BT726 150
BT727 150 BT728 150
BT729 150 BT730 150
BT731 150 BT732 150
BT733 150 BT734 150
BT735 280 BT736 280
BT737 150 BT738 150
Table 13. Line 7 BTs (Up and down lines)
25 KV Traction Equipment Sizing Calculations 19
4. 25 kV Feeders
Dimensioning of 25 kV feeders has been developed according to the worst criterion of
following ones:
Maximum admissible current for conductors will be taken into account in order to
select the cable according to the maximum calculated current in normal conditions.
Voltage drop will be calculated in order to maintain minimum voltage above the
minimum voltage required for operation, which is 19 kV, according to EN.
Conductors must withstand mechanical and thermal loads during a short circuit.
Firstly, the value of currents foreseen in all of these cases is calculated. With all of these
values of currents, the size of the conductors which compose the feeders are checked.
4.1. Rated current calculation (In)
4.1.1. Main track
The maximum current calculated for feeding of the main line in Line 7 can be obtained from
Power Consumption Assessment for the electrical dimensioning of the Line 7: Mukundpur
Shiv Vihar. According to results given by the software, the worst case regarding currents is
when Mukundpur TSS and Dhaula Kuan TSS fail. In such case, INA TSS must feed the
section fed by these two substations in normal operation.
FAILURE OF MUKUND PUR AND DHAULA KUAN TSS
25+400 INA
TSS
34+935 SP
42+140VN-NG
TSS
48+775 SP
54+000YMVH
TSS
Figure 6. Worst case from the current values point of view. Case N-2.
In this case, according to the results given by the software, the currents in each outgoing
feeder from Mukundpur substation are:
Case F1 DOWN LINE F1 UP LINE F2 DOWN LINE F2 UP LINE
AVG 353.69 339.30 162.07 86.84
RMS 439.58 384.58 192.75 160.73
MAX 1152.14 774.55 364.55 349.99
Table 14. Current in feeder cables obtained in Traction Simulation Study in case N-2
25 KV Traction Equipment Sizing Calculations 20
Where F1 are the feeders which feed the Mukundpur side and F2 are the feeders which feed
the Shiv Vihar side of OHE.
Therefore, the feeders must be sized for an In of 439.58 A.
In the chapter 4.5 the conductors of feeders are sized according to this value of
current.
4.1.2. Depot Calculation
For Depot, the following cases have been considered:
Starting up of one train.
Several trains in stabling tracks consuming auxiliary power (33% of trains stabled in
depot).
The maximum current obtained between these two situations will be considered for sizing
the feeder cables from TSS to Depot.
Current in the starting up
For the starting up of the trains, the maximum current consumed by one train is 240 A
according to rolling stock data received (annex 4). It is considered that only one train is
starting up at depot at the same time.
Current because of auxiliary power consumption
The power required by auxiliaries of the rolling stock (6 cars) is 198 kVA.
In Mukundpur Depot there are 18 stabling track with capacity for 36 trains formed by 6 cars.
Considering that 33 % of the trains will be consuming maximum power at the same time, the
current through the feeder will be:
minn
a
nU
SnI
Where:
n = number of trains consuming auxiliary power at the same time
Sa = apparent power of auxiliaries of the rolling stock (6 cars) in kVA.
Unmin = minimum admissible voltage in kV.
25 KV Traction Equipment Sizing Calculations 21
Unmin (kV) 19 Minimum admissible voltage
n 12 33% of total capacity of stabling tracks
Sa (kVA) 198 According to Rolling Stock data
In (A) 125.05 Calculated with previous data
Table 15. Current in feeder cable in Mukundpur Depot.
Case of 12 trains with auxiliary power consumption
In Vinod Nagar Depot there are 45 stabling track with capacity for 45 trains formed by 6 cars.
Considering that 33 % of the trains will be consuming maximum power at the same time, the
current through the feeder will be:
minn
a
nU
SnI
Where:
n = number of trains consuming auxiliary power at the same time
Sa = apparent power of auxiliaries of the rolling stock (6 cars) in kVA.
Unmin = minimum admissible voltage in kV.
Unmin (kV) 19 Minimum admissible voltage
n 15 33% of total capacity of stabling tracks
Sa (kVA) 198 According to Rolling Stock data
In (A) 156.31 Calculated with previous data
Table 16. Current in feeder cable in Vinod Nagar Depot.
Case of 15 trains with auxiliary power consumption
Therefore the maximum current considered to size the feeder cable to Mukundpur and to
Vinod Nagar Depot will be given by the starting up of train case.
In the chapter 4.5 the conductors of feeders are sized according to these values of
current.
4.2. Calculation with current in case of nominal overload of the transformer (Io)
In the previous chapter, the nominal current in the worst case of overload has been
determined according to results given by Power Consumption Assessment.
However, traction transformers must have an overloading capacity of traction transformer of
50%loading for 15 minutes and 100% overloading for 5 minutes, after the transformer has
attained steady temperature on continuous operation at full load, with interval between two
successive overloading of 3 hours.
25 KV Traction Equipment Sizing Calculations 22
Therefore, in case of the maximum overload of the transformer, the current will be bigger
than obtained by calculations, because the transformer capacity has been selected in order
to fulfill this overloading requirement.
Taking this into account, the capacity of the transformer considered for calculations must be
of 40 MVA.
The maximum current given by the transformer in overload situation can be obtained by:
n
oo
U
SI
With:
So = apparent power in kVA in 50% and 100% overload.
Un = nominal voltage in kV.
Therefore, the currents will be:
Un (kV) 25 25
Sn (kVA) 60000 80000
In (A) 2400 3200
Table 17. Currents given by traction transformer in overload cases
These currents will pass through 4 feeders existing in the substation (up and down,
Mukundpur and Shiv Vihar sides). The quantity of the total current which goes for every
feeder will not be the same. To make the calculation, the same percentages which have
been obtained in the Power Consumption Assessment calculation have been considered. In
the case of failure n-2, these percentages are:
RMS %
F1 DN 439.58 37%
F1 UP 384.58 33%
F2 DN 192.75 16%
F2 UP 160.73 14%
Table 18. RMS values of current in every feeder cable of INA TSS. N-2 case
Taking these percentages into account, the most loaded feeder in the overload situation will
take the 37% of the total current. Therefore, the feeder must be dimensioned for withstand
888 A during 15 minutes and 1184 A for 5 minutes.
25 KV Traction Equipment Sizing Calculations 23
In the chapter 4.5 the conductors of feeders are sized according to these values of
current.
4.3. Voltage drop
Voltage drop calculated in Traction Simulation Study for Line 7 has already into account the
length of the feeders which feed main tracks from TSSs. Therefore, they are suitable
according to this criterion.
Regarding feeder to Depots, voltage drop must be calculated according to expression:
XjRILU
Where:
L = Length of the conductor (km)
I = Current of the conductor (A)
R = conductor resistance ( /km)
X = conductor reactance ( /km)
The voltage drop will be:
Feeder Mukundpur Depot Vinod Nagar Depot
L (km) 1.2 1.7 Distance from drawings
I (A) 240 240 From chapter 4.2
R (/km) 0.0754 0.0754 Calculated from catalogue
X (/km) 0.115 0.115 Calculated from catalogue
U (V) 39.60 56.10 Calculated with previous data
Table 19. Voltage drop calculation for feeder cables in depots
4.4. Short circuit criteria
When sizing and selecting equipment, and electrical components must be taken into account
in accordance with VDE (Association of German Electrical Engineers) determinations, not
only due to permanent loads the current and voltage, but surges caused by short circuits.
Short-circuit currents are usually several times higher than nominal therefore cause high
dynamic and thermal overloads. The short circuit currents traversing land can also be the
cause of contact stresses and unacceptable interference. Short circuits can cause the
destruction of equipment and components or cause damage to people if the design does not
take into account the maximum short-circuit currents.
25 KV Traction Equipment Sizing Calculations 24
For calculation of short circuit currents will follow the guidelines VDE 0102, and 2/11.75
1/11.71 parts.
Two methods exist to perform the calculation, one, the absolute impedance calculation, and
the other, the dimensionless impedance calculation or per unit. It has been selected the
calculation per unit method for this design.
The per unit method simplifies the calculation when there are two or more levels of voltage
and interest the effective value. It also presents other advantages:
Manufacturers specify the impedances in percent of the nominal values given in the
plates.
The impedances per unit of the same type of apparatus are very close values,
although their ohmic values are very different. If you do not know the impedance of a
device, you can select from tabulated data that provide reasonably accurate values.
The impedance of a transformer unit is equal in the primary than in the secondary
and is not dependent on the type of connection of the windings.
To follow the method per unit must establish two arbitrary values, such condition all others.
Normally the base values chosen are:
A [MVA] power for the entire circuit
B [kV] to a voltage level
For a different voltage level, the voltage value of the base has to be multiplied by the
transformation ratio of the transformer which separates the two levels.
In calculating circuit currents requires knowledge of the temporal variations since the short
circuit occurs until it reaches the permanent short-circuit current. As in practice as quickly as
possible short circuit current by circuit breakers or other devices, knowledge of temporal
variations of the short-circuit current is only necessary to select and size the equipment and
components in some cases.
The parameters involved in the calculation of the short circuit currents are:
I"k: is the rms value of the symmetrical short-circuits current, is the moment when the
short circuit occurs. From this value the following currents are determined.
Is: Maximum current asymmetric short, is the maximum instantaneous value of the
current, which occurs after the short circuit occurs. Also known as peak value or
impulse current. This value may know electrodynamics forces.
25 KV Traction Equipment Sizing Calculations 25
Isc: Permanent Short Circuit Current, is the rms value of the symmetrical short-circuit
current, which endures after completion of all transients. Used to determine the
thermal stress on machinery.
Ia: balanced current court, is the rms symmetrical short-circuit current flowing through
a switch on the instant you start separating contacts. Used to determine the
performance characteristics of the switch off apparatus.
This design will be carried out calculations phase short circuits, and these, short circuit away
from the generator. Thus one must take into account that VDE 0102 values permanent short
circuit current (Icc) and cutting the symmetrical current (Ia) coincide with the current value of
the symmetric initial short circuit current (I"k).
4.4.1. Simply Single Line Scheme
The following diagram shows only those different voltage levels, and the status of power
transformers and substation different outputs, in order to perform the calculation of short
circuit currents:
CIT
TT220 kV/25 kV40 MVAUcc=13.8%
TSS
OHE
FEEDER TOUP LINE
FEEDER TODN LINE
FEEDER TOUP LINE
FEEDER TODN LINE
Figure 7. Simply Single Line Scheme.
4.4.2. Equivalent Single Line Scheme
To obtain the equivalent circuit simply replace the transformer by its respective impedance.
The short circuit in the feeder cables will have its maximum value just outside of the
substation, as the absence lead length the short circuit effect is not reduced by the line
25 KV Traction Equipment Sizing Calculations 26
impedance. The impedances for conductors and switchgear are negligible and will not be
included in the schemes or calculations.
The equivalent circuit is reflected in the figure below. The figure also marked the possible
points where it can happens different electrical short circuits.
Figure 8. Equivalent circuit.
4.4.3. Impedance Calculations
To perform the calculation method impedances adapted per unit it has to be fixed, first,
arbitrary baseline values. These values determined for each element in intensity per unit.
Values are taken as basis:
SB = 20 MVA
UB = 220 kV
The table shows the values per unit based on an equal basis for all power system
substations.
UB (kV) 220 25
SB (MVA) 20 20
IB (A) 90,9 800
Table 20. Short circuit current per unit based calculation
Observations of the table:
SB = Apparent power kVA basis for the entire system, arbitrary value.
25 KV Traction Equipment Sizing Calculations 27
UB = Voltage basis for each kV voltage level is obtained by multiplying the
transformation ratio between two voltage levels.
IB = current per unit A for each voltage level is obtained from the equation:
U
SI
1000
Values in percent transformers having its reference voltage circuit (Ucc).
The short-circuit impedance (ZCC) approximately matches the value shorted reagent (Xcc), so
the error made by omitting the resistance is minimal and does not affect the final results ZCC
Xcc
With the results of the baseline values for each voltage level it is possible to calculate the
impedance by referring to the power unit base. The generic equation for this calculation is:
N
Bcc
S
SZpuZ
100)(
where:
Zcc impedance circuit is in percent.
SB is the power base.
Sn is the rated power of the electrical machine.
The equivalent impedance of the network is obtained as follows: cc
Bnet
S
SZ
where:
SB is the power base.
SCC is the short-circuit power of the network (given by electrical company).
The results are shown in the following table:
Component Characteristics Impedance per unit
referred to SB = 20 MVA
NET Scc = 8800 MVA ZN = 0,0023 pu
RT Sn = 40 MVA
Zcc = 13.8% ZRT = 0,069 pu
Table 21. Impedance per unit calculation
25 KV Traction Equipment Sizing Calculations 28
4.4.4. Calculation of the continuous current of short circuit (Isc)
As mentioned above permanent short circuit current (Icc) is equal to the symmetrical initial
current (I"k) and cutting the symmetrical current (Ia). akcc III"
The calculation uses the equation of the Laws Ohm using values per unit: eq
ccz
ui
Where u = 1 when calculating per unit, and zeq the calculated value in the table above for
each point.
Then the resulting values are multiplied by the base value of current, as the voltage level,
obtaining the absolute value of the constant intensity at each point shorting: Bcccc IiI
Short-
circuit
Point
Equivalent
Impedance
[pu]
Short-circuit
current [pu] Base current [A]
Permanent
short-circuit
current [A]
A ZeqA = 0,0023 iccA = 434,78 IB = 90,9 IccA = 39521,74
B ZeqB = 0,069 iccB = 14,49 IB = 800 IccB = 11592
Table 22. Short circuit continuous current calculation
4.4.5. Calculation of the Maximum Current Asymmetric Short-Circuit (Is)
Also called surge current is the maximum value and its value is given by the equation:
ccS IxI 2
Where x is a factor which depends on the relationship between the effective resistance and
the reactance of the circuit impedance. As the resistive value is unknown, take x = 1.8 which
is an accepted value for these cases.
Thus, following the above equation using a value x = 1.8, the impulse current in each short-
circuit point will be the value shown in the following table:
25 KV Traction Equipment Sizing Calculations 29
Short-circuit
point
Permanent SC
current (kA)
Maximum Current
Asymmetric SC
(kA)
A IscA = 39.52 IsA = 100.60
B IscB = 11.59 IsB = 29.50
Table 23. Maximum Short-Circuit Asymmetric Current calculation
4.4.6. Rupture capacity and connection
For the election of the switches are fundamental two variables:
Breaking capacity (or power off). Is defined by cutting symmetrical current (Ia). It is
expressed in MVA
anr IUS
Connection capacity (or power connection). Is defined by the maximum asymmetric
short circuit current (IS). It is expressed in MVA
snc IUS
Electric
Point
Cutting
Symmetrical
Current (kA)
Breaking Capacity
(MVA)
Surge Current
(kA)
Connection
Capacity
(MVA)
A IaA = 39.52 SrA = 8694.4 IsA = 100.60 ScA = 22132
B IaB = 11.59 SrB = 289.75 IsB = 29.5 ScB = 737.5
Table 24. Breaking and connection capacity calculation
4.5. Conductor sizing
4.5.1. Type of Conductor
Medium Voltage Cables are manufactured with XLPE insulation. It is very remarkable
features cables, both losses in the dielectric, thermal and electrical resistivity and dielectric
strength.
25 KV Traction Equipment Sizing Calculations 30
Being able to work at a service temperature of 90C, these cables have the possibility of
transmitting more power than any current wire section. In addition, its smaller size makes it
more manageable cable, easier to install, lighter and easier to transport.
Type Single pole
Simple Nominal Voltage 26 kV
Nominal voltage
between phases 45 kV
Maximum voltage
between phases 52 kV
Voltage pulses 250 kV
Maximum permanent
temperature allowable in
the conductor
90C
Screen Copper
Isolation Polyethylene (XLPE)
Envelope Polyvinil Chloride (PVC)
Table 25. Conductor characteristics
4.5.2. Size of Conductor
The feeders will be installed into canalization from the TSS to the viaduct. On the viaduct
they will be installed on the parapet, supported by brackets. In case of the feeders of Depots,
they will be into canalization from the TSS to the depot FP and from the FP to OHE.
Therefore, the lower admissible current will occur when the cables are laid down buried into
canalization. According to suppliers information, the admissible nominal current for an
underground copper cable 1x240 mm2 is 501 A (see annex 1), when it is buried at 1.2 m
depth, with ground temperature of 25C and a ground thermal resistivity of 1 Km/W.
Considering that in the worst case, the groud temperature will reach the 40C it will be
needed to consider a deration factor of 0.88. Therefore, the maximum nominal current of
1x240 mm2 copper cable will be 440 A.
4.5.2.1. Permanent current
In case of main tracks, maximum average current will be 439.58 A per feeder, so 219.79 A
per each 240 mm2 cable in permanent operation. Therefore this 240 mm2 cable is valid with
a safety factor of 2.
25 KV Traction Equipment Sizing Calculations 31
In case of Depots, maximum nominal current will be 240 A, so one copper cable of 240 mm2
can withstand this current with a safety factor of 1.8.
4.5.2.2. Short time operation current
Regarding short time operation currents caused by overloading of the transformer, the
capacity of one conductor is given by expression:
kBZKB fII (annex 2, chapter 18.6.5, expression 18.122)
Where:
- IKB is the admissible current for short time operation
- Iz is the admissible current for permanent operation
- fkB is overloading factor, given by
b
b
t
t
Z
n
KB
e
eI
I
f
1
1
2
(annex 2, chapter 18.6.5, expression 18.126)
Where:
- In is the initial current before the overload (nominal current)
- tb is the duration of the overload
- is time constant of the cable (1/5 of the time taken from the curve to almost reach
the permissible final temperature). It is given by the expression:
2
ZI
qB (annex 2, chapter 18.6.2, expression 18.117)
Where:
- q is the cross section of the conductor
- B is a constant related with the conductor properties, environment temperature and
the maximum temperature admissible for the cable permanent operation. It is given
by the expression:
201 20
200
c
c cB (annex 2, chapter 18.6.2, expression 18.118)
25 KV Traction Equipment Sizing Calculations 32
Where:
- c is the final temperature in the cable by overload current
- 0 is the initial temperature in the cable before the overload
- 20 is the conductivity of the conductor. For copper 56106 1/m
- c is the specific heat of the material. For copper 3.45106 J/Km3
- 20 is the heat transferring factor. For copper 0.00393 K-1
Therefore, the admissible currents for100% and for 50% of overload in the cable will be:
100% overload 50% overload Source of data
c (C) 90 90 Admissible temperature for un XLPE cable
0 (C) 50 50 Initial temperature in the cable before the overload
20 (1/m) 5,60E+07 5,60E+07 From Annex2 table 18.37 20 (1/K) 0,00393 0,00393 From Annex2 table 18.37 c (J/Km3) 3,45E+06 3,45E+06 From Annex2 table 18.37
q (mm2) 240 240 Cross section of the cable
Iz (A) 440 440 Chapter 4.5.2 of this document
In (A) 219.8 219.8 Nominal current in each cable of feeder (Half of RMS value 439.58A, obtained from Traction simulation study)
tb (s) 300 900 Duration of overload: 5 minutes (300s) and 15 min (900s) for 100% and 50% of overload.
B (A2s/m4) 6,06E+15 6,06E+15 Calculated with previous data
1803,18 1803,18 Calculated with previous data fkB 2.268 1.469 Calculated with previous data
IkB (A) 998.12 646.58 Calculated with previous data
Table 26. Short time operation capacity calculation for 240 sqmm copper cable
Therefore, one 240 mm2 cable is able to withstand 998.12 A for 5 minutes and 646.58
during 15 minutes.
According to calculated in chapter 4.2 of this document, the feeder cable (2 cables of 240
mm2) must be dimensioned for withstand 888 A during 15 minutes and 1184 A for 5
minutes, so each cable of 240 mm2 should be able of withstand 444 A during 15 minutes
and 592 A for 5 minutes.
Therefore, 240 mm2 cables are able to withstand the overload currents with safety factors of
1.45 and 1.68.
25 KV Traction Equipment Sizing Calculations 33
4.5.2.3. Short circuit current
Regarding of the maximum short circuit current supported by the cable, it can be obtained as
it is shown in the following figure.
As it can be seen in this figure, short circuit current considering duration of fault of 3 s is 19
kA, higher to short circuit current calculated in chapter 4.4.4.
Therefore, copper conductor of 240 mm2 selected is valid for this application.
25 KV Traction Equipment Sizing Calculations 34
Section o
f con
ducto
r (m
m2)
Curr
ent
(kA
)
Duration (s)
Figure 9. Short circuit capacity of 240 sqmm copper cable
25 KV Traction Equipment Sizing Calculations 35
5. Return Cables
5.1. Return cables
In front of substations, rails will be connected to substation by means of 3.3 kV cables. Their
aim is to carry the return traction current from rails to substation, so they must withstand the
same current than 25 kV feeders. Therefore they will be made up of the same number of
cables and cross section, as the 25 KV feeders.
5.2. Return conductor
One all aluminium conductor with a nominal cross section of 233 sq.mm and a copper
equivalent of 140 sq.mm will be used as Return Conductor. Dimensioning of this return
conductor has been developed according to the worst criterion of following ones:
Maximum admissible current for conductors will be taken into account in order to
select the cable according to the maximum calculated current in normal conditions.
Voltage drop will be calculated in order to maintain minimum voltage above the
minimum voltage required for operation, which is 19 kV, according to EN.
Conductors must withstand mechanical and thermal loads during a short circuit.
5.2.1. Rated current calculation (In)
In the Return current system foreseen, the return conductor must carry the same current as
catenary. Therefore it must be dimensioned for carrying the same current calculated in the
chapter 4.1.1., (439.58 A).
The maximum admissible current for one all aluminium conductor (AAC) with a nominal
cross section of 233 sq.mm is 584 A in the following conditions (annex 3):
Environmental temperature: 40C
Solar radiation 900 W/m2.
Wind: 0.6 m/s
Maximum conductor temperature: 80C
Frequency: 50Hz
Applying a deration factor of 0.9 to take into account the solar radiation and other deration
factor of 0.89 to take into account that the worst environmental temperature will be 50C, the
maximum admissible current will be 467.78 A, so the conductor selected is valid for the
nominal current.
25 KV Traction Equipment Sizing Calculations 36
In stations, return conductor will be made by means a 233 sq.mm stranded aluminium
conductor, with insulated sleeve. It will be laid under platforms.
5.2.2. Voltage drop
Voltage drop calculated in Traction Simulation Study for Line 7 has already into account the
characteristics of return conductors, so it is not needed any additional calculation.
5.2.3. Short circuit criteria
Regarding of the maximum short circuit current supported by the Return conductor, it can be
obtained by means of following expression:
Where:
I: Short circuit current (A)
t: Short circuit duration (s)
K: parameter which depends of kind of conductor (Cu or Al) and of its isolation. In
present case with aluminium conductors, K = 94 will be assumed (jump of
temperature from steady temperature to short circuit temperature minimum), so worst
scenario has been assumed.
S: cross section of the conductor (mm2)
Therefore, the minimum section required to withstand the short circuit current calculated in
chapter 4.4.4 will be:
I (A) 11600 Calculated in chapter 4.4.4 of this document
t (s) 0.25 Short circuit duration (estimated as
conservative value)
K 94 Value for aluminium conductor
S (mm2) 61.7 Calculated with previous data
Table 27. Return conductor sizing under short circuit current criteria
Therefore, aluminium conductor of 233 mm2 selected is valid as return conductor.
6. Induced Voltage Calculation
According to IEC 60287-1-3:2002, induced voltage per unit length in a conductor can be
determined by the following expression:
25 KV Traction Equipment Sizing Calculations 37
km
VIMfE 3102
Where:
f: is the frequency of the nominal voltage waveform
I: is the maximum permanent current main conductor
M: is the mutual inductance between two conductors arranged in parallel given by the
expression:
km
mH
D
DM
p
m2log46,0
where:
Dm: is the distance between the two conductors 2
'dDDm
Dp: is the equivalent diameter of conductor induced S
D p4
For cable 26/45kV XLPE, Cu 240 Sqmm the characteristics are:
d = 18.3 mm
d' = 20.1 mm
D = 38.5 mm
Screen = 16 mm2
Figure 10. Cross section of XLPE insulated cable
The maximum drop voltage in case of the end of the cable being earthed is given by the
expression:
25 KV Traction Equipment Sizing Calculations 38
LEV
where:
E: induced voltage per unit length in a conductor
L: Length of conductor
According to this length in each case, the drop of voltage will be obtained per each feeder:
Mukundpur Dhaula
Kuan INA
Vinod
Nagar Maujpur
Rajouri
Garden
Kashemere
Gate
f (Hz) 50 50 50 50 50 50 50
I (A) 219.79 219.79 219.79 219.79 219.79 219.79 219.79
Dm (mm) 8 8 8 8 8 8 8
Dp (mm) 4.514 4.514 4.514 4.514 4.514 4.514 4.514
M (mH/km) 0.252 0.252 0.252 0.252 0.252 0.252 0.252
E(V/km) 17.46 17.46 17.46 17.46 17.46 17.46 17.46
L (km) 1.5 1.5* 1.2 0.7 2.1 1.1* 2.75*
V (V) 26.19 26.19 20.94 12.22 36.65 45.41 48.01
(*) Length obtained earthing the sheath cable in it center point
Table 28. Induced Voltage Calculation
Therefore, in all cases the voltage in the sheath can be lower than touch voltage by earthing
the cables in one end or in their center point and no sheath voltage limiters will be required.
7. Circuit Breakers rating
Circuit breakers are foreseen in the outgoing feeders in traction substations (TSSs), and in
depots Feeding posts, installed in the incoming feeder from TSS and in the incoming feeder
from main tracks.
In any case, circuit breakers must be able to actuate in short circuit conditions. Therefore, for
the election of the circuit breakers are fundamental two variables:
Breaking capacity (or power off). Is defined by cutting symmetrical current (Ia). It is
expressed in MVA
Connection capacity (or power connection). Is defined by the maximum asymmetric
short circuit current (IS). It is expressed in MVA
25 KV Traction Equipment Sizing Calculations 39
These variables have been calculated in the chapter 4.4.6 of these documents, and,
regarding 25 kV circuit breakers they are:
Cutting Symmetrical Current: Ia = 11.59 kA
Breaking Capacity: Sr = 289.75 MVA
Surge Current: Is = 29.5 kA
Connection Capacity: Sc = 737.5 MVA
Regarding voltage, they must able to withstand nominal values foreseen in the traction
system:
Rated voltage: 25 kV
Maximum service voltage (permanent): 27.5 kV
Therefore, the characteristics required for the circuit breakers foreseen in Mukundpur and
Vinod Nagar Depot Feeding posts, as well in feeders of Rajouri Garden FP, Dhaula Kuan FP
and Welcome FP will be:
Rated voltage kV 25
Maximum service voltage (permanent) kV 27.5
Service frequency Hz 50
Number of phases 1
Erection Outdoor
Rated current A 2000
3 sec. Short time current kA 25
Symmetrical breaking capacity kA 25
Rated peak withstand current kA 40
Table 29. Circuit Breakers characteristics
8. Interrupters rating
Interrupters foreseen in the OHE have to be able to operate under load conditions.
According to calculations shown in the chapter 4.1 the maximum nominal current through
each feeder is 439.58 A.
25 KV Traction Equipment Sizing Calculations 40
Catenaries for up and down tracks are paralleled in SSPs along the track. Therefore, the
interrupters will be dimensioned for the total current of the two tracks:
In= 439.58 + 384.58 = 824.16 A.
Regarding voltage, they must able to withstand nominal values foreseen in the traction
system:
Rated voltage: 25 kV
Maximum service voltage (permanent): 27.5 kV
Therefore, the characteristics required for the interrupters foreseen in the switching posts of
Line 7 will be:
Rated voltage kV 25
Maximum service voltage (permanent) kV 27.5
Service frequency Hz 50
Number of phases 1
Erection Outdoor
Rated current A 2000
Table 30. Interrupters characteristics
9. Current Transformers rating
Current transformers will be used in depots Feeding post for current measuring and
protection. Therefore, they must be rated for the nominal current foreseen in depots which is
240 A according to calculations included in chapter 4.1.2.
In addition, current transformers will be used in feeders in:
Rajouri Garden FP
Dhaula Kuan FP
Welcome FP
Regarding voltage, they must able to withstand nominal values foreseen in the traction
system:
Rated voltage: 25 kV
Maximum service voltage (permanent): 27.5 kV
25 KV Traction Equipment Sizing Calculations 41
Therefore, the characteristics required for the current transformers in OHE part will be:
Voltage / earth insulation kV 27.5
Frequency Hz 50
Erection Outdoor
Insulation withstand voltage (permanent) kV 36
Secondary Core
Core 1 600/1, 5P10, 20VA
Protection class
Core 2 600/1, 5P10, 15VA
Protection class
Withstand Over-current (1s /peaks) kA 20 / 40
Table 31. Current transformers characteristics
25 KV Traction Equipment Sizing Calculations
ANNEX 1. TECHNICAL DATA OF 26/45 KV XLPE
INSULATED COPPER CABLE USED FOR CALCULATION.
media tensin anexo b
DATOS TCNICOS DEL CABLE VOLTALENE H 26/45 kV (conductor de cobre)RHZ1
26/45 kV1x35/161x50/161x70/161x95/161x120/161x150/161x185/161x240/161x300/161x400/161x500/161x630/161x800/161x1000/16
1712022482973383814315015656447318249211007
17420725831436141147255864074386098411321269
0,5240,3870,2680,1930,1530,1240,09910,07540,06010,0470,03660,02830,02210,0176
0,1590,1520,1440,1360,1320,1250,1210,1150,1120,1060,1020,0980,0950,090
0,1350,1440,1610,1750,1860,2090,2260,2490,2750,3410,3750,4110,4600,546
1 x seccinconductor
(Cu)/seccinpantalla (Cu)
(mm2)
Cdigo conductor(mm)
aislamiento(mm)
pantalla (mm) cable (mm) Peso (kg/km)
Radio decurvaturaesttico
(posicin final)(mm)
Radio decurvaturadinmico
(durante tendido)(mm)
26/45 kV1x35/161x50/161x70/161x95/161x120/161x150/161x185/161x240/161x300/161x400/161x500/161x630/161x800/161x1000/16
2011786120117862201178633701133520052424209923402001378720084553200017422011786437011342201065692011786520117866
78
9,711,412,614,115,918,320,523,126,329,634,138,7
24,925,827,629,230,530,932,735,137,838,942
45,449,953,5
26,929,231
32,633,934,336,138,541,242,345,448,853,356,9
34,435,437,238,740
40,442,244,647,348,451,554,960
63,6
132014601720201022902520291035004180491060207410949011550
5505665956196406466757147577748248789601018
6887087447748008088448929469681030109812001272
*Condiciones de instalacin: una terna de cables directamente enterrada o bajo tubo a 1,2 m de profundidad, temperatura de terreno 25 C y resisitividad trmica 1 Km/W.**Condiciones de instalacin: una terna de cables al aire (a la sombra) a 40 C.
NOTA: valores obtenidos para una terna de cables al tresbolillo y en contacto. Para el clculo de la reactancia inductiva con los conductores en cualquier disposicin aplicar la frmula(A) de la pgina 214.
IMPORTANTE: Para los valores concretos de intensidades mximas segn los conexionados de pantalla se ruega contactar con Prysmian.
CARACTERSTICAS DIMENSIONALES (Valores aproximados)
(Valores aproximados)
1 x seccin conductor(Cu)/seccin pantalla
(Cu) (mm2)
Intensidad mximaadmisible enterrado*
(A)
Intensidad mximaadmisible
al aire** (A)
Resistencia delconductor a 20 C
(/km)
Reactancia inductiva(/km)
Capacidad(F/km)
CARACTERSTICAS ELCTRICAS
Tensin nominal simple, Uo (kV)Tensin nominal entre fases, U (kV)Tensin mxima entre fases, Um (kV)Tensin a impulsos, Up (kV)Temperatura mxima admisible en el conductor en servicio permanente (C)Temperatura mxima admisible en el conductor en rgimen de cortocircuito (C)
26455225090250
26/45 kV
201
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25 KV Traction Equipment Sizing Calculations
ANNEX 2. GUIDE FOR CALCULATION OF CABLE
CAPACITY UNDER SHORT TIME OPERATION CURRENTS.
25 KV Traction Equipment Sizing Calculations
ANNEX 3. TECHNICAL DATA OF ALUMINIUM CABLES
USED FOR CALCULATION.
(1) Para conductor expuesto a una radiacin solar de 900 W/m, considerando una emisividad de 0,6, al nivel del mar y viento de 0,6 m/seg, temperatura ambiente de 40 C, temperatura mxima admisible de 80C y una frecuencia de 50 Hz.
31
Seccin nominal
Formacin Dimetro
exterior
aprox.
Masa
aprox.
Carga de rotu-ra calculada
Resistencia
elctrica mxima
a 20oC y
c. c.
Intensidad
de corriente
admisible (1)
mm2 N x mm mm kg/km kg ohm/km A
10 7 x 1,35 4,1 27 195 2,7842 78
16 7 x 1,70 5,1 43 302 1,7558 104
25 7 x 2,15 6,5 70 457 1,0977 139
35 7 x 2,52 7,6 95 594 0,7990 171
50 7 x 3,02 9,1 135 827 0,5563 215
70 19 x 2,15 10,8 190 1242 0,4025 265
95 19 x 2,52 12,6 260 1611 0,2930 324
120 19 x 2,85 14,3 335 2061 0,2291 380
150 37 x 2,25 15,8 405 2648 0,1877 431
185 37 x 2,52 17,7 510 3137 0,1496 498
240 37 x 2,85 20,0 650 4013 0,1170 584
300 61 x 2,52 22,7 840 5172 0,0907 687
400 61 x 2,85 25,7 1075 6615 0,0709 804
500 61 x 3,23 29,1 1381 8247 0,0552 942
625 91 x 2,96 32,6 1732 10645 0,0439 1087
800 91 x 3,35 36,9 2218 13234 0,0343 1266
1000 91 x 3,74 41,1 2764 15995 0,0275 1445
1265 91 x 4,21 46,3 3503 20268 0,0217 1657
Caractersticas Tcnicas
Bobinas de
madera
Acondicionamientos:
Cables segn norma IRAM 63003
Prysal Aluminio
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25 KV Traction Equipment Sizing Calculations
ANNEX 4. ROLLING STOCK DATA USED FOR
CALCULATION