medium voltage energy transmission system

CELLULES CEP14/15 MEDIUM VOLTAGE

950 V—3200 V—5500 V—6600 V

Thoughts on the distribution of electrical energy

3

CONTENTS

GENERAL :

The receivers………………………………………………………………………………. p. 4

Network transformer in a pit or compact substation………………………………………. p. 4

The LV sub network………………………………………………………………………..p. 5

The TIT transportation network…………………………………………………………… p. 6

Earthing scheme…………………………………………………………………………… p. 7

Pipes calculation……………………………………………………….……….…………..p. 9

Transformer substation…………………………………………………………………..…p. 10

Dimmer……………………………………………………………………………………. p. 10

TIT network control ………………………………………………………………..………p. 10

TOOLS :……………………………………………………………………………………. p. 11

APPLICATION EXAMPLE :…………………………………………………..………… p. 12

APPENDIX :

Number of lamps per TIT / LV network transformer………………………….…………….. p. 18

Choice of the LV cable section………………………………….…………………………… p. 19

Dimensions of prefab concrete pits………………………………………….……………….. p. 20

Choice of MV cable section…………………………………………………………………. p. 21

Appearing impedance of MV and LV cables…………………………………………….….. p. 23

Voltage drop calculation……………………………………………………………………... p. 24

Choice guide of transportation voltage level to supply an end of line load………………….. p. 26

Choice of 950 V cable section………………………………………………………………... p. 29

GLOSSARY

LV : Low Voltage.

MLV : Maximum Low Voltage.

HCP : High Cutting Power.

MV : Medium Voltage.

NP : Nominal Power.

TIT : Gathers MLV and MV Voltages

Standards : NFC 17-200 from March 2007, NFC 52-410 from 1978

This document is not an exhaustive study, but is merely a collection of observations and advice aimed at aiding

specialists.

Augier takes no responsibility for use of advice on all previous and future installations.

4

TIT Installation Conception

GENERAL :

The Receiver :

The types of power receivers can be very varied. The parameters below are used to characterize them. Some are

directly associated with the type of power receiver and so do not need to be recorded.

The type of receiver.

Power supply voltage and tolerances.

Phase system (single or three phase).

Power rating, start-up characteristics (overcurrent, cycle and duration).

The type of use: continuous, cyclic or occasional.

The conditions for simultaneous operation and simultaneous start-up of several power receivers, if

necessary, both in steady state and at start-up.

The degree of continuous operation requirement.

NETWORK TRANSFORMER IN A PIT OR COMPACT SUBSTATION:

In the chapter below, the transformers of network or mini substation will be called "step down sub-station ".

The step down sub-station is used to supply a power receiver or group of power receivers.

The locations of the step down sub-stations and the configuration of the power receivers are determined according

to conditions in the field, relating to installation of these stations and laying of LV lines, by an economic optimization

calculation that takes into account the costs of the stations and LV cables, as well as the installation costs.

The step down station’s power rating is determined by adding together the power of the supplied power receivers. In

addition the following factors will be taken into account :

Power efficiencies and factors, accessory power consumption, and possibly an incrementation factor, to

determine the theoretical current.

Permissible limits for power supply voltage when operating in steady state and at start-up.

Ambient temperature conditions.

The current/voltage characteristics of the power consumers, the predictable deterioration in electrical

efficiency due to ageing, the possible extensions, to determine a working current.

The start-up characteristics to define a start-up current, possibly after application of an incrementation

factor.

The coupling of the step down transformer will be single or three phase, depending on the design of the LV

sub-network (see below).

5

There are two possible types of step down sub-station, depending on its power and installation conditions :

Either a TED step down station, normally installed as infrastructure in an inspection pit (power limited

to 160 kVA). This is an operational complete unit, equipped with two plug-in TIT terminals to ensure

line continuity to the downstream sub-station, comprising the TIT/LV transformer, the TIT and LV pro-

tection, and the LV output which can be either a 6 meters cable or a plug-in terminal.

Pits of watertight transformers must offer an inside volume at least equal to four times the transformer volume. In

addition, they must allow cable inputs and their connection with respect to curving radius values indicated by the

cable constructor.

Transformers’ pits can be prefab. They must be composed of a grill equipped with a locking device by a special

screw, which forbids the access to the transformer until the TIT input is not opened at the installation origin, put

in circuit breaker and on earth (according to NF C 17 200 standard for road lighting installations).

Or a compact internal or external station, depending on the installation conditions, comprising a dry varnish

impregnated transformer.

Outdoor type compact substations are designed to be installed on a concrete base, with cable output and input

from the ground, under plastic wrapping.

The step down sub-stations are equipped with the following electrical protection :

MV side : one or more fuses whose rating is/are determined according to the character istics of the step

down transformer.

However this protection will only be installed when there are several TIT/LV sub-stations linked to a step up

station, because otherwise it is impossible to ensure selectivity with the step up transformer’s TIT protection.

LV side : The LV circuit breaker whose rating must be greater than the working current of the supplied power

receivers.

In the transformer : thermal probes connected to the LV circuit breaker.

THE LV SUB-NETWORK

Its layout depends on the terrain’s characteristics, the road layout, the possibilities for underground crossings, the

locations of natural or man-made obstacles.

A ground scheme must be chosen in accordance with current legislation and the continuous operation

requirements. A certain number of rules will be defined as a result of this choice.

These rules will determine whether or not it is necessary to install differential protection or insulation monitoring

devices on the step down station, and to determine the cross-section of the LV cables, called LV feeders.

These rules are defined in a general way in the standard NF C 15-100 and when appropriate also in specialized

standards such as C 17200 or the C 17-205 guide for public lighting.

They guarantee :

Feeder protection against excess current

Personnel protection against indirect contacts

6

Concerning short circuit protection, as described in standard NF C 15-100 (art. 435-1 and 533-3 comments), the LV

circuit breaker of the step down sub-station that ensures overcharge protection is also considered to provide short

circuit protection at the same time.

For road lighting installations, the C 17-205 practical guide nevertheless recommends that the minimum short-circuit

rule should be satisfied, and suggests possible reductions in the line cross-section without any additional protection

device.

The LV sub-network of a step down sub-station as we have designed it does not comprise any reduction in

cross-section, and so the case described in guide C 17-205 does not concern us.

Let us consider for a moment the possibility that a short-circuit is not detected by the magnetothermal tripping

device, therefore creating a continuous fault.

In such a case the thermal probe protection installed in our TIT/LV sub-stations is capable of eliminating the fault,

regardless of whether or not it is dangerous for the LV feeders.

Given these considerations, it is not necessary to satisfy the minimum short-circuit rule, concerning LV networks

supplied via TED type or compact type step down transformers.

THE TIT TRANSPORTATION NETWORK

The number of outputs, their layout :

They are determined according to the planned locations for the different TIT/LV substations, the possibilities

offered by the terrain for trench excavation, road crossings and civil engineering works.

As far as possible we will make every effort to achieve balanced outputs, and when appropriate we will consider the

possibility of looping-in 2 outputs together, for repair purposes.

Any given output can be implemented as a single antenna, or with T branches or in a cross.

The TIT transmission network obtained in this way can also be linear type, star, loop or meshed, or a combination of

these different types.

The general output characteristics :

The output phase system must be three phase, in order to power the three phase TIT/LV sub-stations.

In this case, the preferred TIT voltage will be 6600 V, 5500 V or 950 V.

It should be noted that single phase TIT/LV sub-stations can however be installed on this type of output. The

transformers corresponding to this configuration comprise a phase selector making it possible to balance the output

charge distribution on the three phases.

If the TIT/LV sub-stations are all single phase, the output can be single phase or three phase.

In most cases, the single phase solution with a preferential voltage of 3200 V or 950 V is the most economic and the

easiest to implement. However, when the outputs are of a considerable length, the three phase solution with single

phase TIT/LV sub-stations can be selected, to reduce line drop and generally satisfy all the rules stipulated in the

standards.

7

Earthing scheme :

The scheme will be chosen from the TNRC or TNRS schemes, that in general are the most suitable (defined in con-

formity with standard UTE D17 200). The neutral TIT is linked directly to ground at the installation origin.

When the outputs are single phase either scheme can be selected, and the only difference is that in the TNRC

scheme the TIT neutral is grounded at each TIT/LV substation, and in the TNRS scheme it is not.

If the outputs are three phase the ground scheme has to be TNRS, since the neutral is not distributed.

The earth connections must be made :

Individual earth connections.

Connection to a bare copper conductor with à minimum cross section of 25 mm² which serves as both the earth

connection and an equipotential link between the poles.

Common earth point with the poles connected by insulated cables.

The second solution, the earth network for bonding the equipment earths comprises a bare copper conductor with a

minimum cross sectional area of 25 mm² buried directly in the ground corresponding to the TIT line, is the one we

recommend because it allows to obtain better resistance to earth values.

Since the 1st of October 2003, the NC C 17 200 standard imposes this second solution for road lighting.

The earthing circuit this way will enable to connect :

The earth point of the TIT/LV transformer.

The neutral of TIT winding in a generalised earth scheme (TNR-C).

The safety grid in the transformer housing.

One point of the low voltage.

The conducting parts of any equipment that can be accessed at the same time as that of the road lighting

system.

For the substation, the earth connection must be a bare conductor 25 mm² made of copper buried at about 50 cm

from substation.

This conductor will be depth of about 40 cm, the iron framework of the station concrete pedestal being, in that case,

linked to this conductor.

The transformer neutral must be connected to the earth connection to realise a TN scheme.

The substation earth bonding must be connected to the earth connection :

The earths of all circuits in the substation.

The screens of the cable.

The transformer tank.

The switching devices.

The metal pipework and ducting.

However, the doors of the building and the metal ventilation slots should not intentionally be bonded.

9

CALCULATION OF FEEDER CROSS SECTION :

This calculation will be determined by the maximum authorized voltage drop, by adding together the values from

the TIT and LV voltage drops. The total voltage drop must not exceed 6% for a road lighting installation, and 8%

in other cases.

However it will be necessary to check that the protection fuse located at the circuit origin (at the step up station)

makes it possible to satisfy the stipulated rules, i.e.:

Protection against indirect contacts.

Protection against over charges.

Protection against excess current.

If necessary a differential relay can be installed, if a TNRS scheme is used, to make it easier to satisfy the rules

mentioned above.

10

THE SUBSTATION :

The substation will be step up or step down type.

Implementation :

As far as possible, the substation will be installed in the center of the installation. However, installation off-center

is perfectly acceptable when an TIT transmission voltage is used.

The implementation will be determined according to the possibilities for installation offered by the site.

Nominal Power :

Nominal power is determined by the sum of step-down sub-station powers, taking into account the extension

possibility or non-project and by retaining a standardized transformer power.

Step-up stations will be used for powers from 5 to 160 kVA for easy projects, with most often, only one TIT net-

work departure.

Step-down stations will be used for powers from 160 to 1250 kVA which intensities are compatible with the circuit

breaking bearing of pluggable terminals of step-down watertight transformers.

For service continuity reasons, it is possible to retain a transformation station equipped with two identical power

transformers. One transformer supplies the whole installation in case of the failure of one of the transformers.

Coupling:

The type of step-up transformer coupling depends on which phase system is selected for the TIT outputs.

In the case of three phase outputs, it will be three phase.

In the case of single phase outputs, it can be three phase, three/two phase, three/single phase or single phase:

Three phase can be selected if there are three outputs or a multiple of three. These outputs must be virtu-

ally balanced.

Three/two phase will be selected if there are two outputs or a multiple of two. These outputs must be

virtually balanced.

Three/single phase is the only coupling that corresponds to all the possible situations and that allows

looping of 2 outputs for repair. It implies that the primary currents will not be balanced.

TIT networks control :

For networks only composed with lamps, inputs will be temporary, off during the day, controlled by a photo

electrical cell doubled with an astronomical clock. The control will also be realizable by current carrier using the

STEP II system.

For networks supplying receivers different from lamps, inputs will be permanent.

For mixt networks, inputs will be permanent the lighting control will be made by current carrier.

Dimmer :

It is better to put, in the transformer station, a dimmer regulator to reduce the power of lamps during weak traffic

hours. The dimmer regulator allows, during hours when reduction happens, consumption savings.

11

TOOLS :

In the appendix, you will find all the documentation to help you with the realization of a quick TIT study :

Case of the supplying of receiver units at a line end :

The guide for the choice of the voltage level transportation to supply the end of line load.

Case of the supplying of receivers uniformly spread, road lighting case :

Annex : number of lamps for each TIT/LV lighting transformer.

Choice of the LV cable section downstream of the step-down watertight transformer.

Concrete prefab pits best dimensions for step-down transformers installation.

Choice of the MV cable section for single-phase and three-phase networks, for a 2 or 3 % voltage drop.

Choice of the MLV cable section for single-phase and three-phase networks, uniformly spread load at the end of

the line.

Calculation formula enabling to control the choices with the annex usage and AUGIER.

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APPLICATION EXAMPLE :

SUPPLY FOR A ROAD LIGHTING « LV/TIT » INSTALLATION

PROJECT :

In the following section, by means of an example we show how to determine rapidly the main sections constituting

a preliminary study for a road lighting project using TIT transmission voltage.

We draw the reader’s attention to the need to check or further specify the results obtained using the method set out

below. This is because, apart from the approximate nature of this example, it is not intended to provide an answer

for every situation or for every special case that may arise.

The aim of the project we have used in this example is to define the power supply for road lighting of a road.

Determination of the basis for calculation :

The calculations are to be performed on the basis of the information to be supplied below :

Number of power consumers and type : the installation comprises one lighting pole every 35 m, each

fitted with two 250W high pressure sodium lamps.

Installation of the lighting poles : The lighting poles are set up in the central reservation.

Network length : The total length of the installation is 4 km.

Station location : The station is located in the middle of the installation.

Supplied voltage level : Three phase 400 V

Installation conditions : Maximum ambient temperature 40°C

Altitude less than 1000 meters

Internal installation

Operating principle :

This substation will be supplied from a low voltage three phase 400 V power source, via the mains

network, and will transform this voltage into a transmission voltage to be determined.

STEP 1 : Determination of the network’s rating power :

Determination of number of the lamps :

The installation’s power is determined by the number and type of the lamps used, whose mean characteristics

are described in guide C 17 205.

Application :

Number of lamps : 230

Type and power : 250 W HPS

Determination of the road lighting transformers’ power :

Their power depends on the number of lamps powered by the network transformer.

The transformers are used in conformity with standard NFC 52-410, which limits their use to 0.8x NP where

NP is the nominal power.

13

As a rule we will use transformers with :

3 kVA in exchangers where the lamps will be distributed in all directions.

5 kVA for the current sections.

10 kVA for the pole power supplies.

Other power supplies available according to use.

The number of lamps supplied by a transformer is given in our table « Number of lamps by transformers TIT/LV »

LAMPS TYPE HPS LAMPS

Power (W) 70 100 150 250 400 600 1000 2000

Power (VA) 104 138 196 322 506 713 1242 2310

TRANSFORMER POWER RATING NUMBER OF LAMPS BY TRANSFORMER

Nominal power Using power

400 VA 320 VA 3 2 1 1

630 VA 500 VA 5 3 2 1 1

1 kVA 0,8 kVA 8 5 4 2 1 1

2 kVA 1,6 kVA 16 11 8 5 3 2 1

3 kVA 2,4 kVA 24 17 12 7 4 3 2 1

5 kVA 4 kVA 40 29 20 12 8 5 3 1

10 kVA 8 kVA 25 16 11 6 3

Application :

5 kVA with a maximum of 12 lamps HPS 250 W

35 m

Substation

TIT/LV 5 kVA

12 x HPS 250 W

Substation

TIT/LV 5 kVA

TIT NETWORK

Determination of the network’s total power :

The total power depends on the number of network transformers

Application :

20 network step-down transformers 5 kVA, total power = 100 kVA.

STEP 2 : Determination of the low voltage cable cross-section : In general, the TN ground scheme will be used.

The cable cross-section depends on :

The length of the low voltage sub-network seen from the transformer side, for a transformer placed in the

middle.

On the protector block rating (LV circuit breaker).

14

The cable section is shown in the « Low voltage cross section determination »

Maximum length (m) for one side of the transformer Protected against indirect contacts with 1 extr. MALT Rating power

(kVA) Cross section (mm²)

4 6 10 16 25

0,4 552 774 1143 1561 2000

0,63 552 774 1143 1561 2000

1 552 774 1143 1561 2000

2 345 484 714 976 1250

3 276 387 571 780 1000

4 221 310 457 624 800

5 172 242 357 488 625

6 138 194 286 390 500

8 155 229 312 400

10 181 248 317

35 m

Substaion TIT/LV

5 kVA

12 x HPS 250 W

LV Câble 2x 4mm²

Substation TIT/LV

5 kVA

TIT Network

102,5m

Application :

Length of the LV sub-network on one side of the transformer : 87.5 meters + 5 meters vertical section per pole.

Total length = 102.5 meters. The cable cross section is 2 x 4 mm².

STEP 3 : Determination of the distribution type and level of transmission voltage :

The distribution may be :

Three phase 5500 V for long charged networks, or networks that comprise three phase power receivers.

Single phase 3200 V for power values up to 100 kVA, for installations that only have one output.

Two phase 3200 V for power values up to 100 kVA, for installations with two balanced outputs (2 x 50 kVA).

Application :

The substation is placed in the center of the application with 50 kVA to supply on each side. Two phase 3200 V

distribution.

STEP 4 : Determination and selection of Road lighting Transformers :

The transformers are determined according to :

The transformer coupling.

The type of distribution network (single phase or three phase) .

The type of cable used.

15

Cross section (mm²) Power Rating

(kVA) 6 10 16 25

30 1750 2890 4580 7260

40 1310 2170 3435 5445

50 1050 1735 2750 4355

60 875 1445 2290 3630

70 750 1240 1960 3110

80 655 1080 1720 2720

Application :

Single phase transformer for single phase network, using two pole concentric cable TER MM, TED MMX or

Modulo BI type.

Please refer to the transformer documentation available.

STEP 5 : Determination of the MV cable cross-section

The choice of cable cross-section depends on the power and length of the network.

The length is basically limited by the line drop.

Protection is ensured by choosing a protection.

The cross-section is given in appendix « MV cable cross section determination », which takes into account a

maximum MV line drop of 2%, compatible with the total limit of 6% for MV and LV.

Application :

The 3200 V cable cross section for supply 50 kVA per output on the Length 2000 meters is 16 + 16 mm².

35 m

TED MMX 5 KVA

3200 V/230 V

12 x HPS 250 W

LV Cable 2x4 mm²

Two pole concentric cable 16 +16 mm²

TED MMX 5 KVA

3200 V/230 V

Single phase network 3200 V

Step 6 : Determination of the substation :

Determination of the substation power :

The main transformer’s power must be at least equal to the sum of the nominal powers of the road lighting

transformers, supplied downstream (NFC 17-200).

We will choose a standard power, chosen in the range : 25, 50, 63, 80, 100, 125, or 160 kVA

Application :

In order to have an extension possibility, the retained power is 125 kVA.

16

The substation will be equipped with :

A LV counting table.

A step-up set protection and control table.

A power transformer, three-two phases, 400 V/3200 V with a 125 kVA power rating.

The different features that constitute the protection table are determined depending on the transformer’s

characteristics and dimensioned during the definitive study.

Conclusion :

This fore-study enables to difine the heights conforming to NFC 17-200 et NFC 52-410 standards with respect to a

global voltage drop of 6% maximum.

All the features of the fore-study, will have to be confirmed by a more precise calculation, in order to also precise and

confirm the values obtained.

Indeed, for our application, the 3200 V cable section retained would be 10+10 mm².

17

APPENDIX

18

NUMBER OF LAMPS FOR EACH TIT/LV NETWORK TRANSFORMER :

Determination of the maximum number of lamps to use depending on the transformers power, conforming to the

standard recommendations NFC 17-200, NFC 52-410 and C 17-205 guide.

TYPE OF LAMPS HIGH PRESSURE SODIUM LAMPS MERCURY LAMPS

Power Rating (W) 70 100 150 250 400 600 1000 2000 125 250 400 700

Power Rating (VA) 104 138 196 322 506 713 1242 2310 161 310 495 886

TRANSFORMER

POWER RATING NUMBER OF LAMPS PER TRANSFORMER

Nominal Power Useful Load

400 VA 320 VA 3 2 1 1 2 1

630 VA 500 VA 5 3 2 1 1 3 1 1

1 KVA 0,8 kVA 8 5 4 2 1 1 5 2 1

2 KVA 1,6 kVA 16 11 8 5 3 2 1 10 5 3 1

3 KVA 2,4 kVA 24 17 12 7 4 3 2 1 15 7 5 2

5 KVA 4 kVA 40 29 20 12 8 5 3 1 25 13 8 4

10 KVA 8 kVA 25 16 11 6 3 25 16 9

TYPE OF LAMPS LOW PRESSURE SODIUM LAMPS METALLIC IODIZED LAMPS

Power Rating (W) 26 35 55 91 131 250 400 1000 2000

Power Rating (VA) 37 51 78 113 152 322 506 1242 2369

TRANSFORMER

POWER RATING

NUMBER OF LAMPS PER TRANSFORMER

P. Nominale P. utile

400 VA 320 VA 8 6 4 2 2 1

630 VA 500 VA 13 9 6 4 3 1 1

1 KVA 0,8 kVA 21 15 10 7 5 2 1

2 KVA 1,6 kVA 43 31 20 14 10 5 3 1

3 KVA 2,4 kVA 30 21 15 7 4 2 1

5 KVA 4 kVA 35 26 12 8 3 1

10 KVA 8 kVA 25 16 6 3

For information :

Lamps lifespan is about 8 000 to 10 000 hours.

The lighting functioning time, in France, is 4 085 hours.

19

DETERMINATION OF THE LOW VOLTAGE CABLE CROSS SECTION :

Single-phase network transformer

Maximum lengths in meters of the pipes, single-phase 230 V, TN scheme, with the windings edge linked to the

earth, protected against indirect contacts and overloads. Case of single-phase transformers protected by a circuit-

breaker associated with a thermal probe.

Calculations established with a protection conductor of 1 x 25 mm².

Power

Rating

(kVA)

Intensity (A) Under 230 V

Protection rating Low

voltage

Maximum length (m) one side of the transformer

Protected against indirect contacts with an earthing plug edge

Section (mm²)

4 6 10 16 25

0.4 1.74 C60 N - 10 A (B) 552 774 1143 1561 2000

0.63 2.74 C60 N - 10 A (B) 552 774 1143 1561 2000

1 4.35 C60 N - 10 A (B) 552 774 1143 1561 2000

2 8.70 C60 N - 16 A (B) 345 484 714 976 1250

3 13.04 C60 N - 20 A (B) 276 387 571 780 1000

4 17.39 C60 N - 25 A (B) 221 310 457 624 800

5 21.74 C60 N - 32 A (B) 172 242 357 488 625

6 26.09 C60 N - 40 A (B) 138 194 286 390 500

8 34.78 C60 N - 50 A (B) 155 229 312 400

10 43.48 181 248 317 C60 N - 63 A (B)

Non standard section

Maximum lengths (in meters) of single-phase pipes in scheme TN, protected against indirect contacts :

L = k U S / (R (1+m)Ind With : k = 0,8

U = 230 V

S = LV cable section

R = 0,023

m = S / 25

Ind = 5 x circuit-breaker rating

Maximum lengths (in meters) of single-phase pipes in scheme TN, protected against circuit breakings :

In the case of transformers protected by a circuit-breaker associated to a thermal probe, rule not to be verified.

L = K U S / (2 Rcc ind) With : K = 0,8

Rcc = 0,023 (Protection by circuit-breaker)

Ind = 5 x circuit-breaker rating

20

DIMENSIONS OF CONCRETE PITS Depending on the existing pit, for TER, TED and MODULOBLOC

Transformer Power

Rating

Dimensions (inside) concrete pits (mm) Approx.

Weight (kg) Models

L l H

TED MMX 0,4 à 6 kVA 800 800 887 900 EP 80

Modulobloc bi or tri jusqu’à 6 kVA

TER MM ou MT 1 à 10 kVA

1000 800 887 1100 EP 100 TED MMX 8 et 10 kVA

TED MTT 2 à 10 kVA

Modulobloc bi or tri 8 et 10 kVA

Every TED type 16 à 32

kVA 1790 880 1200 3000 L5T With elbow terminals

or modulobloc

INDICATIVE DIMENSIONS OF CONCRETE PITS Minimum dimensions (with a 3x25 mm² cable) for TED > 10 kVA and TEH

Transformer Power

Rating

Concrete pits dimensions (mm)

L W H (b. straight) H (b. elbowed)

TED MMX 16 kVA 1300 750 1300 1050

TED TTT 5 - 10 kVA

TED MMX 25 kVA

1450 800 1350 1150 TED MTT 16 - 25 kVA

TED TTT 16 kVA

TED MMX 25 kVA

1700 900 1500 1300 TED MTT 50 kVA

TED TTT 25 - 32 kVA

TEH TTT 50 kVA 1700 900 1600 1400

TEH TTT 80 - 100 kVA 1900 1000 1700 1500

21

DETERMINATION OF THE MV CABLE CROSS SECTION

3200 V single-phase network

Compatible with a 2 % voltage drop : Uniformly spread power rating, maximum network departure lengths in meters.

Power Rating

(kVA)

Cross Section (mm²)

6 10 16 25

Impedance at 85 °C

3.9 2.36 1.49 0.94

20 2626 4339 6872 10894

30 1750 2893 4582 7262

40 1313 2169 3436 5447

50 1050 1736 2749 4357

60 875 1446 2291 3631

70 750 1240 1964 3112

80 656 1085 1718 2723

90 583 964 1527 2421

100 525 868 1374 2179

110 477 789 1250 1981

120 438 723 1145 1816

130 404 668 1057 1676

140 620 982 1556

150 579 916 1452

160 542 859 1362

170 510 809 1282

180 482 764 1210

190 457 723 1147

200 434 687 1089

210 655 1037

220 625 990

230 598 947

240 573 908

Compatible with a 3 % voltage drop : Uniformly spread power rating, maximum network departure lengths in meters.

Cross Section (mm²) Power Rating

kVA 6 10 16 25

20 3938 6508 10309 16340

30 2626 4339 6872 10894

40 1969 3254 5154 8170

50 1575 2603 4123 6536

60 1313 2169 3436 5447

70 1125 1860 2945 4669

80 985 1627 2577 4085

90 875 1446 2291 3631 100 788 1302 2062 3268

110 716 1183 1874 2971

120 656 1085 1718 2723

130 606 1001 1586 2514

140 563 930 1473 2334

150 525 868 1374 2179

160 492 814 1289 2043

170 463 766 1213 1922

180 438 723 1145 1816

190 415 685 1085 1720

200 651 1031 1634

210 620 982 1556

220 592 937 1485

230 566 896 1421

240 542 859 1362

22

Compatible with a 4 % voltage drop : Uniformly spread power rating, maximum input lengths in meters.

Power Rating

(kVA)


6 10 16 25

Impedance at 85 °C

3.9 2.36 1.49 0.94

20 5251 8678 13745 21787

30 3501 5785 9163 14525

40 2626 4339 6872 10894

50 2101 3471 5498 8715

60 1750 2893 4582 7262

70 1500 2479 3927 6225

80 1313 2169 3436 5447

90 1167 1928 3054 4842

100 1050 1736 2749 4357

110 955 1578 2499 3961

120 875 1446 2291 3631

130 808 1335 2115 3352

140 750 1240 1964 3112

150 700 1157 1833 2905

160 656 1085 1718 2723

170 618 1021 1617 2563

180 583 964 1527 2421

190 553 913 1447 2293

200 868 1374 2179

210 826 1309 2075

220 789 1250 1981

230 755 1195 1895

240 723 1145 1816

Power Rating

(kVA)


6 10 16 25 35 50

Impedance at 85 °C

3.9 2.36 1.49 0.94 0.66 0.46

50 6205 10254 16242 25745

100 3103 5127 8121 12872 18333 26304

120 2585 4273 6767 10727 15278 21920

140 2216 3662 5801 9195 13095 18789

160 1939 3204 5076 8045 11458 16440

180 1724 2848 4512 7151 10185 14614

200 1551 2564 4060 6436 9167 13152

220 1410 2331 3691 5851 8333 11957

240 1293 2136 3384 5363 7639 10960

260 1193 1972 3123 4951 7051 10117

280 1108 1831 2900 4597 6548 9394

300 1034 1709 2707 4291 6111 8768

320 1602 2538 4023 5729 8220

340 1508 2388 3786 5392 7737

360 1424 2256 3576 5093 7307

380 1349 2137 3387 4825 6922

400 1282 2030 3218 4583 6576

420 1221 1934 3065 4365 6263

440 1165 1846 2926 4167 5978

460 1115 1765 2798 3986 5718

480 1692 2682 3819 5480

500 1624 2574 3667 5261

630 1289 2043 2910 4175

Three-phase 5500 V network, compatible with a 2% voltage drop

23



Power Rating

(kVA)


6 10 16 25 35 50

Impedance at 85 °C

3,9 2,36 1,49 0,94 0,66 0,46

50 9308 15381 24362 38617

100 4654 7691 12181 19309

120 3878 6409 10151 16090 22917 32880

140 3324 5493 8701 13792 19643 28183

160 2909 4807 7613 12068 17188 24660

180 2585 4273 6767 10727 15278 21920

200 2327 3845 6091 9654 13750 19728

220 2115 3496 5537 8777 12500 17935

240 1939 3204 5076 8045 11458 16440

260 1790 2958 4685 7426 10577 15176

280 1662 2747 4350 6896 9821 14092

300 1551 2564 4060 6436 9167 13152

320 1454 2403 3807 6034 8594 12330

340 1369 2262 3583 5679 8088 11605

360 1293 2136 3384 5363 7639 10960

380 1225 2024 3206 5081 7237 10383

400 1163 1923 3045 4827 6875 9864

420 1108 1831 2900 4597 6548 9394

440 1058 1748 2768 4388 6250 8967

460 1672 2648 4198 5978 8578

480 1602 2538 4023 5729 8220

500 1538 2436 3862 5500 7891

630 1221 1934 3065 4365 6263

Power Rating

(kVA)


6 10 16 25 35 50

Impedance at 85 °C

3,9 2,36 1,49 0,94 0,66 0,46

50 12410 20508 32483 51489

100 6205 10254 16242 25745

120 5171 8545 13535 21454 30556

140 4432 7324 11601 18389 26190

160 3878 6409 10151 16090 22917 32880

180 3447 5697 9023 14303 20370 29227

200 3103 5127 8121 12872 18333 26304

220 2821 4661 7383 11702 16667 23913

240 2585 4273 6767 10727 15278 21920

260 2387 3944 6247 9902 14103 20234

280 2216 3662 5801 9195 13095 18789

300 2068 3418 5414 8582 12222 17536

320 1939 3204 5076 8045 11458 16440

340 1825 3016 4777 7572 10784 15473

360 1724 2848 4512 7151 10185 14614

380 1633 2698 4274 6775 9649 13844

400 1551 2564 4060 6436 9167 13152

420 1477 2441 3867 6130 8730 12526

440 1410 2331 3691 5851 8333 11957

460 2229 3531 5597 7971 11437

480 2136 3384 5363 7639 10960

500 2051 3248 5149 7333 10522

630 1628 2578 4086 5820 8351

24

LV AND MV CABLES APPEARING IMPEDANCE

MV cables :

Table valid for concentric bipolar and tripolar cables.

Given values for cables calculated at an average temperature of 50 °C.

Cross Section (mm²) Impedance ( / km)

6 3.41

10 2.03

16 1.28

25 0.81

35 0.58

50 0.41

LV Cables :

Table valid for armed LV bipolar and tripolar cables.

Given values for cables calculated at an average temperature of 65 °C.

Impedance ( / km) Cross Section (mm²)

4 4.4

6 2.96

10 1.78

16 1.15

25 0.743

35 0.551

50 0.421

70 0.309

25

VOLTAGE DROP CALCULATION

1/ LV Side Voltage Drop : ULV

1/a) LV Single Phase Network :

ULV = 2 L i (n (n + 1) / 2) Z

ULV % = U / 230 (V)

i (A) : rated current of one pole i.e. = P(VA) * q / 230 (V) with q : number of lamps per pole

and P : power of one lamp

L (km) : inter-distance length between each lighting pole, plus 5 meters cable to reach the pole.

n : Number of poles on the side of the network transformer.

Z ( / km) : LV cable impedance.

1/b) LV Three-phase Network :

ULV = 3 L3 (i*3) (n3 (n3 + 1 ) / 2) Z

ULV % = U / 400 (V)

i (A) : Rated current of one pole i.e. = P (VA) * q / 230 (V) with q : number of lamps per pole

and P : power of one lamp.

L3 : Inter-distance between groups of three poles => for example l3 = 3*L + 0,005.

n3 : Number of poles in group of three.

26

2/ MV Network Voltage Drop : Umv

2/a) TER or TED Type transformers (MV/LV) are regularly distributed in the network

A-TER MM or TED MMX :

Umv = L I (n(n+1)/2) Z

Umv %= Umv / 3200 (V)

I(A) : Intensity for a transformer calculated on its nominal power in kVA : I=P / 3200 (V).

L (km) : Interdistance between each transformer.

n : Number of transformer.

Z (Ω / km) : MV cable impedance.

B– TER MT or TED MTT :

Umv = 3 (3 * L) (3 * I) (n3 (n3 + 1) / 2) Z

Umv %= Umv / 5500 (V)

I (A) : Current of one transformer according to P (VA) calculated as I = P / 5500 (V).

L (km) : Inter-distance length between each transformer.

n3 : Number of transformers in group of 3.

Z ( / km) : IHV cable impedance.

C– TER TT or TED TTT :

Umv = 3 L I (n (n + 1) / 2) Z

Umv %= Umv / 5500 (V)

I (A) : Current of one transformer according to P(VA) calculated as : I = P / (5500 * 3). L (km) : Inter-distance length between each transformer.

n : Number of transformers.

Z ( / km) : MV cable impedance.

2/b) Deliver of power to a distance of L (km) three-phase network :

Umv = 3 L I Z

Umv % = Umv / 5500 (V)

I (A) : Current of the network I = P / (5500* 3).

Z ( / km) : MV cable impedance.

L (km) : Distance between the supplier and the receiver.

Please note :

The power rating mentioned is the sum of the network transformers power rating. In the case of the

network transformers load is reduced , we can use the sum of the power rating of the supplied lamps

counting a coefficient of around 15 %.

27

Way of using the power supply range graph.

These graphs help you to find quickly the right solution for the supply of a single load.

The graph inputs are the distances of the load and its power.

With these parameters, you obtain the voltage level to use and the wire section.

Example :

We have several receptors to supply at 3480 meters far. Their power are respectively 10,20,30 and 50 kVA.

You have to report on the graph the cross between the 10 kVA line and the 3480 meters line. It is in the area for

mono 3200V with a wire section of 6 mm². This is the best solution. You can also notice that it is under the

non-continuous line for mono 950V 35mm² wire section. It means this solution is technically working but

economically less profitable than medium voltage. It will be use only if we absolutely want to use low voltage. As

for the 20 kVA receptors, the only solution is 3200V wire section 6 mm². Then for 30 kVA, we use 10 mm² as wire

section and 16 mm² for the 50 kVA receiver.

Comment on the graphs.

The drawing represent the technical limit for each kind of solution to respect a maximal voltage drop of %.

All the area under the drawing respect this condition.

The colored areas correspond to domain were the use of a solution is the more accurate.

For distance shorter than 500m the graph are not valid.

The non-continuous drawing represent the limit for a technically working solution but not profitable.

28

End of line single-phase loads

29

End of line three-phase loads

30

DETERMINATION OF THE 950 V CABLE SECTION

950 V single-phase network uniformly spread power :

Compatible with a 2% voltage drop :

Maximum input length in meters.

Length (m)

Power Rating

(kVA)

Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I(A)

10 10,53 566 941 1456 2256 3034

16 16,84 354 588 910 1410 1896

25 26,32 226 376 582 903 1213

32 33,68 177 294 455 705 948

50 52,63 113 188 291 451 607

63 66,32 90 149 231 358 482

80 84,21 71 118 182 282 379

100 105,26 57 94 146 226 303



Length (m)

Power Rating

(kVA)

Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I(A)

10 10,53 849 1411 2183 3384 4550

16 16,84 530 882 1365 2115 2844

25 26,32 339 564 873 1354 1820

32 33,68 265 441 682 1058 1422

50 52,63 170 282 437 677 910

63 66,32 135 224 347 537 722

80 84,21 106 176 273 423 569

100 105,26 85 141 218 338 455

Length (m)

Power Rating

(kVA)

Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I(A)

10 10,53 1132 1881 2911 4513 6067

16 16,84 707 1176 1820 2820 3792

25 26,32 453 752 1165 1805 2427

32 33,68 354 588 910 1410 1896

50 52,63 226 376 582 903 1213

63 66,32 180 299 462 716 963

80 84,21 141 235 364 564 758

100 105,26 113 188 291 451 607



31

950 V three-phase network uniformly spread power :



Length (m)

Power Rating

(kVA)

Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I (A)

10 6,08 1132 1881 2911 4513 6067

16 9,72 707 1176 1820 2820 3792

25 15,19 453 752 1165 1805 2427

32 19,45 354 588 910 1410 1896

50 30,39 226 376 582 903 1213

63 38,29 180 299 462 716 963

80 48,62 141 235 364 564 758

100 60,78 113 188 291 451 607



Length (m)

Power Rating

(kVA)

Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I (A)

10 6,08 1697 2822 4367 6769 9101

16 9,72 1061 1764 2729 4230 5688

25 15,19 679 1129 1747 2708 3640

32 19,45 530 882 1365 2115 2844

50 30,39 339 564 873 1354 1820

63 38,29 269 448 693 1074 1445

80 48,62 212 353 546 846 1138

100 60,78 170 282 437 677 910



Length (m)

Power Rating

(kVA) Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I (A)

10 6,08 2263 3762 5823 9025 12134

16 9,72 1415 2351 3639 5641 7584

25 15,19 905 1505 2329 3610 4854

32 19,45 707 1176 1820 2820 3792

50 30,39 453 752 1165 1805 2427

63 38,29 359 597 924 1433 1926

80 48,62 283 470 728 1128 1517

100 60,78 226 376 582 903 1213

32

End of line 950 V single-phase network load :


Maximum input lengths in meters :

Length (m)

Power Rating

(kVA) Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I(A)

5 5,26 849 1411 2183 3384 4550

10 10,53 424 705 1092 1692 2275

16 16,84 265 441 682 1058 1422

25 26,32 170 282 437 677 910

32 33,68 133 220 341 529 711

50 52,63 85 141 218 338 455

63 66,32 67 112 173 269 361

80 84,21 53 88 136 212 284

100 105,26 42 71 109 169 228



Length (m)

Power Rating

(kVA)

Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I(A)

5 5,26 1132 1881 2911 4513 6067

10 10,53 566 941 1456 2256 3034

16 16,84 354 588 910 1410 1896

25 26,32 226 376 582 903 1213

32 33,68 177 294 455 705 948

50 52,63 113 188 291 451 607

63 66,32 90 149 231 358 482

80 84,21 71 118 182 282 379

100 105,26 57 94 146 226 303



Length (m)

Power Rating

(kVA)

Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I(A)

5 5,26 1415 2351 3639 5641 7584

10 10,53 707 1176 1820 2820 3792

16 16,84 442 735 1137 1763 2370

25 26,32 283 470 728 1128 1517

32 33,68 221 367 569 881 1185

50 52,63 141 235 364 564 758

63 66,32 112 187 289 448 602

80 84,21 88 147 227 353 474

100 105,26 71 118 182 282 379

33

End of line 950 V three-phase network load : Compatible with a 3% voltage drop :


Length (m)

Power Rating

(kVA) Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I (A)

5 3,04 1697 2822 4367 6769 9101

10 6,08 849 1411 2183 3384 4550

16 9,72 530 882 1365 2115 2844

25 15,19 339 564 873 1354 1820

32 19,45 265 441 682 1058 1422

50 30,39 170 282 437 677 910

63 38,29 135 224 347 537 722

80 48,62 106 176 273 423 569

100 60,78 85 141 218 338 455



Length (m)

Power Rating

(kVA)

Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I (A)

5 3,04 2829 4703 7278 11281 15168

10 6,08 1415 2351 3639 5641 7584

16 9,72 884 1470 2274 3525 4740

25 15,19 566 941 1456 2256 3034

32 19,45 442 735 1137 1763 2370

50 30,39 283 470 728 1128 1517

63 38,29 225 373 578 895 1204

80 48,62 177 294 455 705 948

100 60,78 141 235 364 564 758

Length (m)

Power Rating

(kVA) Cross Section

(mm²) 6 10 16 25 35

Z (85°) 3,19 1,919 1,24 0,8 0,595

I (A)

5 3,04 2263 3762 5823 9025 12134

10 6,08 1132 1881 2911 4513 6067

16 9,72 707 1176 1820 2820 3792

25 15,19 453 752 1165 1805 2427

32 19,45 354 588 910 1410 1896

50 30,39 226 376 582 903 1213

63 38,29 180 299 462 716 963

80 48,62 141 235 364 564 758

100 60,78 113 188 291 451 607



34

PERSONAL NOTES

35

PERSONAL NOTES

36

AUGIER IS CERTIFIED ISO 9001 SINCE 1995

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medium voltage energy transmission system

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