PLC Planning Guide p3 2 x 11 05

PowerLink Equipment Manual

Chapter 8: Planning guide

Transmission range 3

Planning examples 8

PL_power_calc Program 14

Planning guide PowerLink Equipment Manual

Page - 2 Edition p3_2_x 11/05 © SIEMENS AG 2005

Table of contents:

The transmission range ................................................................................................................................................ 3 General information.................................................................................................................................................... 3 HF Bandwidth of the PowerLink................................................................................................................................ 3

Definition of the adjacent mode.............................................................................................................................. 4 Frequency order using adjacent Tx and Rx bands .................................................................................................. 5

Power amplifier .......................................................................................................................................................... 5 Services transmitted in the PowerLink ....................................................................................................................... 5 Power line attenuation ................................................................................................................................................ 6 Coupling units............................................................................................................................................................. 6 The noise level............................................................................................................................................................ 6

Signal-to-noise ratio................................................................................................................................................ 7 Formulas for the calculation of the transmission range and the SNR......................................................................... 7

Planning examples ........................................................................................................................................................ 8 PowerLink with datapump.......................................................................................................................................... 8

Power level ............................................................................................................................................................. 8 Coupling loss .......................................................................................................................................................... 8 The max. possible transmission rate ....................................................................................................................... 9

PowerLink with analog services ............................................................................................................................... 10 Service configuration............................................................................................................................................ 10 Output level .......................................................................................................................................................... 11 Receive level......................................................................................................................................................... 12 Calculating the SNR ............................................................................................................................................. 12

Program PL_Power_calc.xls...................................................................................................................................... 14 Introduction .............................................................................................................................................................. 14 Input of the PowerLink services ............................................................................................................................... 15 Max. possible line attenuation .................................................................................................................................. 16

Using the datapump .............................................................................................................................................. 16 Planning examples with PL_Power_calc.................................................................................................................. 17

Example 1 datapump ............................................................................................................................................ 17 Example 2 PowerLink with analog services ......................................................................................................... 19

Index directory............................................................................................................................................................ 21 Appendix ..................................................................................................................................................................... 22

List of figures............................................................................................................................................................ 22 List of tables ............................................................................................................................................................. 22

PowerLink Equipment Manual Planning guide

© SIEMENS AG 2005 Edition p3_2_x 11/05 Page - 3

The transmission range

General information

The maximum transmission range of the PowerLink is the difference between the transmit level PTX and the lowest possible receive level PRXmin and must be more than the attenuation of the transmission path.

Output Power - Power Line attenuation = Receive Power Figure 1: The PLC transmission path

The lowest possible receive level PRXmin depends on the noise level of the high voltage line PNoise and the required signal to noise ratio SNR for the transmitted services. For determining the trans-mission range the following information has to be taken into consideration:

The used HF bandwidth and frequencies of the PowerLink

The power amplifier (20W, 40W or 80W)

The services which have to be transmitted

The attenuation of the high voltage line

The expected noise level

HF Bandwidth of the PowerLink

The utilizable frequency range for the carrier transmission over high voltage lines (PLC) is be-tween 28 and 500 kHz. In many countries due to various conditions, certain frequency ranges are reserved for air traffic control, shipping radio service etc.

The frequency range is subdivided in frequency spaces with gross bandwidth B of 2,5 kHz or 4 kHz. At the occupancy of frequency spaces only gross bandwidth of 2,5 resp. 4 kHz or multiple of that may be used.



In the PowerLink system the following HF bandwidth can be adjusted:

Figure 2: The adjustable HF-Bandwidth in the PowerLink

The frequency order of the transmit resp. receive band is regular or inversed adjustable. Depend-ing on the frequency gap between the Tx and Rx frequency band this is considered as adjacent or non-adjacent transmission. The following table shows the definition of adjacent resp. non-adjacent frequency bands:

Definition of the adjacent mode

Table 1: Definition of adjacent mode

HF-Bandwidth Gap between transmit- and receive band Adjacent mode: Activate AXC when the gap is

8 kHz < 8 kHz ≤ 6 kHz 7.5 kHz < 7,5 kHz ≤ 6.25 kHz 5 kHz < 5 kHz ≤ 3.75 kHz 4 kHz ≤ 4 kHz ≤ 4 kHz 3.75 kHz ≤ 4 kHz ≤ 3.75 kHz 2.5 kHz ≤ 4 kHz ≤ 3.75 kHz

All larger frequency gaps are non-adjacent mode. The frequency order for adjacent modes is shown in the next table:

4 kHz grid

2,5 kHz grid



Frequency order using adjacent Tx and Rx bands

In case of adjacent Tx and Rx bands or activated AXC function the following rules have to be observed:

Table 2: Frequency order for adjacent Tx- and Rx bands

Service

F6 Modulation

HF Bandwidth Frequency order lower / upper frequency band

DP only all regular / inversed DP and AMP only coded / uncoded all regular / inversed DP with F2/F3/F6 coded / uncoded all inversed / regular F2 / F3 / F6 (AMP/MP) coded / uncoded all regular / inversed F6 SP Mode 1 uncoded 2 kHz only inversed / regular F6 SP Mode 1 uncoded all (except 2,0 kHz) regular / inversed F6 SP Mode 1 coded all (except 2,0 kHz) inversed / regular F6 SP Mode 2, 3, 4 uncoded all regular / inversed F6 SP Mode 5A uncoded all inversed / regular F6 SP Mode 2, 3a, 3b, 4 coded all inversed / regular

DP Data pump AMP Alternate multi purpose operation MP Multi purpose operation SP Single purpose operation

Power amplifier

For the PowerLink equipment, transmit amplifiers with 20/40 W and 80 W peak power ratings are available.

The necessary power rate depends on the number and type of services and the min. required re-ceive level. This again depends on the noise level PNoise and the required signal to noise ratio SNR for the transmitted services.

Each additional service which is transmitted reduces the output power of the PLC system. At the end of this chapter you’ll find the description of the PowerLink_powercalc.xls program available on the manual CD. This calculates the max. acceptable line attenuation after the services to be trans-mitted, the power amplifier and the expected noise level is entered.

Services transmitted in the PowerLink

The max. number of services which can be transmitted in the PowerLink is four. The available transmitter power is automatically allocated to the different types of signal. The allocation is deter-mined by the noise-bandwidth and the required signal-to-noise ratio of the services.

The output level of the CSP module and the system for each service is shown in the PowerSys form <PowerLink Information Services>.

Figure 3: Example for the display of the voice and pilot level from a PowerLink system



Power line attenuation

For planning PowerLink connections a careful calculation of the line attenuation is essential. For a correct calculation of the power line a number of different values are necessary:

Data of the high voltage line like: Tower, voltage range, length of the line, type of conductors, the sag, transpositions etc.

The PLC frequencies used for transmission and receiving

The type of the coupling unit: Phase-to-Ground, Phase-to-Phase or Inter-System coupling.

The conductors used for coupling

Using a computer program is as accurately as possible. The program also helps to determine the useful conductor(s) for connecting the coupling unit(s).

Coupling units

A phase-to-ground coupling is often used for reasons of cost. This is generally adequate from an engineering viewpoint unless extra-high-voltage lines with a high noise level or long distances are involved. In most line protection applications, however, it is recommended to use a phase-to-phase coupling or inter-system coupling regardless of the higher cost.

Table 3: Comparison of the different coupling types

Coupling type Financial outlay Attenuation Transmission

1 Phase-to-ground coupling

minimal greater than for 2 not guaranteed if a cou-pled conductor breaks

2 Phase-to-phase coupling

twice as high as 1 smaller than for 1 possible if a coupled con-ductor breaks

3 Inter-system coupling twice as high as 1 smaller than for 1 also possible in case of short circuit or grounding of a system on the line

The noise level

The noise level should be taken according IEC resp IEEE recommendations for adverse weather, because the transmission line has to be available throughout the whole year.

The noise level depends on the voltage level, the construction of the overhead line and the used frequency. Typical corona noise power levels on 220kV transmission lines as in IEC 60663 refer-ring to a 4 kHz bandwidth is:

-20 dBm to -10 dBm

The values are given for a 4 kHz bandwidth. For a different bandwidth (BW) of the service a cor-rection Pcor has to be added to this level.

Pcor = 10* log (BW [kHz] / 4[kHz])

In case of transmitting via datapump the service program PowerSys offers a bit rate estimation which shows the max. bit rate for a given bandwidth and noise level.



Signal-to-noise ratio

The signal-to-noise ratio (SNR) is calculated with:

SNR = Receive level – noise level

SNRnoise

aL

PL PRPT

aC

PT = Transmit level at the output of the PLC PL = Transmit level at the coupling point of the line PR = Receive level ac = Coupling loss aL = Line attenuation

Figure 4: The calculation of the SNR

Formulas for the calculation of the transmission range and the SNR

Receive level: PR = PT – aC – aL

Signal to noise ratio: SNR = PR – PNoise

Minimum receive level: PRmin = PNoise + SNRrequired

Subsequently you’ll find calculation examples for using the datapump resp. for voice and data transmission in the PowerLink.



Planning examples

PowerLink with datapump

In the following example the PowerLink configuration is a datapump with 7,5 kHz bandwidth, and 80 W power amplifier. The required bit rate is 42000 bps. The line attenuation is 12 dB and the noise level for 7, 5 kHz bandwidth is assumed with -10,3 dBm.

The figure below shows the output level for the DP signal generator at the CSP module:

Figure 5: HF output for a PowerLink system with datapump

When using a PLC line equipment (PLE) with an 80 W power amplifier, it results in a transmit volt-age-level at the HF output (75 Ohm) from:

-17,4 dB + 55 dB = 37,6 dB.

The QAM signal of the datapump has to be calculated 10 dB less and results in 27,6 dB

The maximum obtainable transmission rate of a datapump connection depends on the available bandwidth and the signal-noise-ratio (SNR). For planning this connection the voltage level must be converted into a power level because the noise levels are also given in power levels.

Power level

Conversion of the voltage level to a power level:

The power level (reference to 1 mW at 600 Ohm) results from

Voltage level at 75 Ohm: + 9 dB

Voltage level at 150 Ohm: + 6 dB

This results in a power level for the:

QAM-signal: +36,6 dBm

Coupling loss

According IEC 60663 an overall loss of 5 dB can be calculated. This results in a power level for the QAM signal at the coupling point of the overhead line from 31,6 dBm.



The max. possible transmission rate

To determine the max. possible transmission rate the signal-to-noise ratio (SNR) must be known. Subsequently the calculation for this example: QAM signal level at the coupling point: 32 dBm.

In the next step an exact calculation of the line attenuation is necessary! In this example a line at-tenuation of 12 dB is assumed. This results in a receive level from:

Transmit level minus line attenuation = 32 dBm – 12 dB = 20 dBm for the DP

In the following table noise levels for different DP bandwidth, voltage levels and carrier frequen-cies (CF) with adverse weather conditions are shown.

Table 4: Noise levels (adverse weather acc. IEEE 643) for different DP Bandwidth

High voltage in kV

CF kHz

DP Bandwidth in kHz adjustable in the PowerLink

7,5 7 6,5 5,5 5 4,7 4,5 4 3,7 3,5 110 75 -14,3 -14,6 -14,9 -15,6 -16,0 -16,3 -16,5 -17 -17,3 -17,6110 250 -20,3 -20,6 -20,9 -21,6 -22,0 -22,3 -22,5 -23 -23,3 -23,6110 500 -22,3 -22,6 -22,9 -23,6 -24,0 -24,3 -24,5 -25 -25,3 -25,6230 75 -10,3 -10,6 -10,9 -11,6 -12,0 -12,3 -12,5 -13 -13,3 -13,6230 250 -15,3 -15,6 -15,9 -16,6 -17,0 -17,3 -17,5 -18 -18,3 -18,6230 500 -17,3 -17,6 -17,9 -18,6 -19,0 -19,3 -19,5 -20 -20,3 -20,6400 75 -5,3 -5,6 -5,9 -6,6 -7,0 -7,3 -7,5 -8 -8,3 -8,6400 250 -10,3 -10,6 -10,9 -11,6 -12,0 -12,3 -12,5 -13 -13,3 -13,6400 500 -12,3 -12,6 -12,9 -13,6 -14,0 -14,3 -14,5 -15 -15,3 -15,6

The signal-to-noise ratio (SNR) is calculated with: SNR = receive level minus noise level. In this example a noise level of -10,3 dBm is calculated. This results in a SNR from:

20 dBm – (-10,3 dBm) = 30,3 dBm

The max. possible transmission rate for a SNR from 30 dBm is shown in the drawing below. The required bit rate needs an SNR of approx. 27 dB when using non-adjacent Tx and Rx bands resp. 29 dB when using adjacent Tx and Rx bands

10 15 20 25 30 35 40

9

8

7

6

5

4

3

2

DP non adjacent bandsDP adjacent bands

B

kbps

64

56

48

40

32

24

16

7,5kHz7 kHz 5 kHz

kbps

45

40

35

30

25

20

15

10

R

SNR

kbps

64

56

48

40

32

24

16

3,5 kHz

kbps

28

24

16

12

8

14

31,5

28,8

B

Figure 6: Derivation of the DP bit rate from the bandwidth and the information density



PowerLink with analog services

The next example shows a PowerLink with the service voice (F2), data transmission (F3) using FSK channels, RM channel and protection signaling in the AMP mode with the service F2. The sys-tem has a 40W amplifier, the line impedance is 75 Ohm.

Service configuration

The service configuration of the PowerLink is shown in the figure below:

Figure 7: Example PowerLink with F2, protection AMP and 3 FSK data channels

The required SNR is: 25 dB for voice and 15 dB for data

The total line attenuation including the coupling loss: 17 dB

Noise level for 4 kHz bandwidth: -20 dBm.



Output level

The transmit levels for voice, pilot and protection are shown in the figure below:

Due to the coded tripping variant the trip frequencies have the same level like voice and pilot

Figure 8: The HF level CSP for voice, pilot and protection

The transmit levels for the FSK channels are shown in the figure below:

Figure 9: The HF level CSP for the FSK channels 600 Bd resp. 200 Bd



For calculation of the HF output level 52 dB (in this example 40W /75 Ohm) have to be added to the displayed CSP level. For the conversion from voltage to power level 9 dB have to be added. The HF output levels are shown in the table below.

Table 5: HF output levels

Service

HF output voltage level dB HF output power level dBm

F2 27,3 36,3 Sys Pilot 27,3 36,3 Protection trip tone 27,3 36,3 FSK 600 Bd 10,3 19,3 FSK 200 Bd 7,3 16,3 RM (50 Bd) 1,3 10,3

Receive level

For calculating the receive level for the services a total line attenuation of 17 dB is assumed. The receive levels are shown in the table below.

Table 6: Receive levels

Service

Receive level in dBm

F2 19,3 Sys Pilot 19,3 Protection trip tone 19,3 FSK 600 Bd 2,3 FSK 200 Bd -0,7 RM (50 Bd) -6,7

Calculating the SNR

The noise level of -20 dBm is given for a bandwidth of 4 kHz. For a different bandwidth (BW) of the service a correction Pcor has to be added to this level.

Pcor = 10* log (BW[kHz] / 4[kHz])

SNR voice:

Correction for the voice BW = 2,1 kHz:

Pcor = 10*log (2,1/4) = -2,8 dB

Noise level for voice = -20dBm + (-2,8) = -22,8 dBm

SNR voice = Rx level – noise level = 19,3 dB – (-22,8 dB) = 42,1 dB



When calculating the SNR for the FSK channels the following bandwidths have to be considered: Table 7: Definition of the FSK channel bandwidth

No. System Nominal Bitrate

max. Bitrate Grid distance Hz

Bandwidth Hz

FM deviation

Hz

Nominal channel level

dBr 1 FM 120 50 85 120 100 ±30 -22,5 2 FM 240 100 170 240 200 ±60 -19,5 3 FM 480 200 340 480 400 ±120 -16,5 4 50 Bd NB 50 60 90 75 ±22,5 -24,5 5 100 Bd NB 100 120 180 150 ±45 -21,5 6 200 Bd NB 200 240 360 300 ±90 -18,5 7 600 Bd 600 880 1140 1000 ±200 -13,5 8 1200 Bd 1200 1300 1710 1440 ±400 -10,5 9 2400 Bd 2400 2500 3400 2720 ±800 -7,5

SNR data 600 Bd:

Correction for the 600 Bd data BW =1 kHz:

Pcor = 10*log (1/4) = -6 dB

Noise level for data = -20 dBm + (-6) = -26 dBm

SNR data 600 = Rx level – noise level = 2,3 dB – (-26 dB) = 28,3 dB

Conclusion: The transmission with the required SNR can be observed.



Program PL_Power_calc.xls

Introduction

When the expected noise level is known, the PL_power_calc.xls program is calculating the max. line attenuation for the desired PowerLink connection. The program is available on the CD ROM in the PowerLink manual and described subsequently.

Figure 10: The PL_power_calc program

Power_calc should be used when the equipment configuration is already completed with the Pow-erConf program. This ensures, that the system is working and can be ordered.

Note:

In the PL_power_calc.xls no plausibility check of the service adjust-ments and no bandwidth calculation is performed!

The program calculates the max. permissible line attenuation for this equipment configuration. This must be more than the attenuation calculated for the customer’s high voltage line.

If it is less, either the PowerLink amplifier must be increased, or if not possible the services have to be reduced since the noise level and the transmission line can’t be changed.

Input of the Power-Link services

Link to IEEE noise levels



Input of the PowerLink services

The figure below shows the section for selecting the required PowerLink services. For the input only the dark yellow fields can be used. The other fields i.e. for the F2 or DP Pilot are completed automatically.

Figure 11: Selecting the services with the yellow marked fields

With click on a service an arrow appears for selecting the available input. For speech and analog data (F3) the bandwidth has to be selected. In case of using FSK channels the baud rate (50 up to 2400 Bd) appears.

Protection signaling (F6) is possible in the single purpose (SP), multi purpose (MP) resp. in the al-ternate multi purpose (AMP) mode. The AMP mode is possible with a speech channel or datapump (DP). If both services are activated in the configuration, the AMP should be used with the speech channel because an interrupt of the DP is causing always the loss of several services.

The service DP is activated with the selection of the used bandwidth (3500 – 7500 Hz).

After selecting the power amplifier (20/40W or 80W) the expected noise level for a bandwidth of 4 kHz has to be entered.

Figure 12: Example for the input of the expected noise level



Max. possible line attenuation

The program calculates the max. possible line attenuation observing that the required SNR for the service with the lowest receive level is obtained. According IEC 60663 the required SNR for speech channels is 25 dB and for data channels 15 dB.

Figure 13: Display of the max possible line attenuation

Using the datapump

When using the service datapump, the necessary SNR depends on the required bit rate. This is requested from the program as soon as a DP bandwidth is adjusted:

Figure 14: Additional inputs for the DP

Bit rate calculation for iMUX The program offers additional a bit rate calculation when the iMUX is activated. In this case the bit rate for the iMUX channels 1 – 4 has to be entered with the corresponding UART. The required DP bit rate appears below. It is less than the aggregate bit rate of the channels 1 – 4 and depends on the UART, because only the data bits are transmitted.



Planning examples with PL_Power_calc

Subsequently the previous planning examples will be shown using the PL_power_calc program.

Example 1 datapump

The PowerLink configuration (ref. to page 8) was a datapump with 7,5 kHz bandwidth, and 80 W power amplifier. The required bit rate was 42000 bps. For the line attenuation 12 dB and for the coupling loss 5 dB were assumed. The noise level for the DP bandwidth 7,5 kHz was assumed with -10,3 dB. The figure below shows the inputs for the PL_power_calc program:

Figure 15: Inputs from example 1 in the PL_power_calc program

The input of the expected noise level must be entered now for the band-width 4 kHz! The corresponding conversion into the noise level of the used DP bandwidth is executed automatically from the program.



The output of the PL_power_calc program for the example 1 is shown in the next figure:

Figure 16: Output of the PL_power_calc program for the bit rate 42000 bps

The result of example 1 was a SNR from 30,3 dBm for a total line attenuation of 17 dB. The re-quired bit rate of 42000 bps needs a SNR of approx 27 dB (3 dB spare).

The PL_power_calc program calculates the maximum line attenuation always for the desired bit rate. Related to the example 1 the program shows the 3 dB spare plus the 17 dB line attenuation. The result is a maximum line attenuation of 20,3 dB.

The maximum line attenuation for the bit rate 42000 bps is calculated with 20,3 dB



Example 2 PowerLink with analog services

The configuration of the PowerLink was set with the service voice (F2), data transmission (F3) us-ing FSK channels, RM channel and protection signaling in the AMP mode with the service F2. The system had a 40W amplifier, the line impedance was 75 Ohm.

The assumed line attenuation including the coupling loss was 17 dB. The noise level for a band-width of 4 kHz was assumed with -20 dB.

The figure below shows the inputs from the configuration in example 2 (ref. to page 10):

Figure 17: Input of the configuration from example 2



The result from example 2 assuming a line attenuation of 17 dB was a SNR for the voice channel of:

SNR voice = 42,1 dB (considering the required SNR of 25 dB this is 17,1 dB spare)

The SNR for the 600 Bd data channel was:

SNR data 600 = 28,3 dB (considering the required SNR of 15 dB this is 13,3 dB spare)

As described before the PL_power_calc program calculates the max. possible line attenuation observing that the required SNR for the service with the lowest receive level is obtained. The result is shown in the figure below.

Figure 18: The result of example 2 displayed in the PL_power_calc program

Related to the example 2 the program shows the 17 dB line attenuation plus the 13,3 dB spare from the data channel.



Index directory

A

adjacent 4

C

Coupling units 6

F

formulars 7 frequency order 4, 5

H

HF bandwidth 3

L

line attenuation 6

N

noise level 3, 6

non-adjacent 4

P

PL_Power_calc.xls 14 planning examples

analog services 10 data pump 8

power amplifier 5

R

RXmin 3

S

services 5 SNR 3

calculation 7

T

transmission range 3



Appendix

List of figures Figure 1: The PLC transmission path......................................................................................................................... 3 Figure 2: The adjustable HF-Bandwidth in the PowerLink........................................................................................ 4 Figure 3: Example for the display of the voice and pilot level from a PowerLink system.......................................... 5 Figure 4: The calculation of the SNR ......................................................................................................................... 7 Figure 5: HF output for a PowerLink system with datapump .................................................................................... 8 Figure 6: Derivation of the DP bit rate from the bandwidth and the information density ......................................... 9 Figure 7: Example PowerLink with F2, protection AMP and 3 FSK data channels ................................................ 10 Figure 8: The HF level CSP for voice, pilot and protection ..................................................................................... 11 Figure 9: The HF level CSP for the FSK channels 600 Bd resp. 200 Bd ................................................................. 11 Figure 10: The PL_power_calc program ................................................................................................................... 14 Figure 11: Selecting the services with the yellow marked fields................................................................................. 15 Figure 12: Example for the input of the expected noise level ..................................................................................... 15 Figure 13: Display of the max possible line attenuation ............................................................................................ 16 Figure 14: Additional inputs for the DP..................................................................................................................... 16 Figure 15: Inputs from example 1 in the PL_power_calc program............................................................................ 17 Figure 16: Output of the PL_power_calc program for the bit rate 42000 bps........................................................... 18 Figure 17: Input of the configuration from example 2................................................................................................ 19 Figure 18: The result of example 2 displayed in the PL_power_calc program.......................................................... 20

List of tables Table 1: Definition of adjacent mode............................................................................................................................ 4 Table 2: Frequency order for adjacent Tx- and Rx bands ............................................................................................ 5 Table 3: Comparison of the different coupling types .................................................................................................... 6 Table 4: Noise levels (adverse weather acc. IEEE 643) for different DP Bandwidth................................................... 9 Table 5: HF output levels............................................................................................................................................ 12 Table 6: Receive levels................................................................................................................................................ 12 Table 7: Definition of the FSK channel bandwidth..................................................................................................... 13

PLC Planning Guide p3 2 x 11 05

Documents

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adverse weather acc

yellow marked fields

coupled conductor breaks

required bit rate

powerlink equipment manual

dp bit rate

total line attenuation