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48

SEL-FT50/SEL-FR12 Fault Transmitter and Receiver System

Instruction Manual

Date Code 20210405

Appendix C: Link Budget Analysis

Appendix C: Link Budget Analysis

Overview

A radio link budget accounts for all losses and gains in a radio link from the 
transmitter to the receiver. Link budget calculations are used to determine the 
amount of link margin available for a given radio link. The link budget includes 
five components: radio transmit power, antenna gains, cable and path losses, 
interference margin, and radio receiver sensitivity. For a reliable link, the receive 
power must be greater than the effective receive sensitivity. The link margin is the 
difference between received power and effective receive sensitivity. The goal of 
link budget calculation is to account for all of the system and path gains and 
losses to determine if an adequate link margin is available (see 

Figure 31

).

                    

Transmitted and Radiated Power Requirements

FCC and IC regulations for 900 MHz ISM (industrial, scientific, and medical) 
band radios such as those used by the SEL-FT50 place limits of +30 dBm on 
maximum radio transmit power and +36 dBm on maximum Effective Isotropic 
Radiated Power (EIRP). EIRP is a measure of the amount of power radiated from 
the main lobe of the transmitter antenna, and is calculated by using 

Equation 1

.

                    

Equation 1

The specified transmit power for radio embedded in the SEL-FT50 includes the 
antenna gain. Because there is no method of connecting an SEL-FT50 to an 
external antenna, you do not need to be concerned with violating EIRP require-
ments if you do not modify the device.

                    

Figure 31

Sample Link Budget

EIRP

TX Power

Cable Loss

Attenuation

Antenna

Gain

Free-Space Path Loss

Clutter/Obstruction Loss

Polarization Mismatch

Fading Loss

Antenna

Gain

Cable Loss

Attenuation

RX Power

Interference

Margin

Link Margin

Effective

RX Sensitivity

Specified

RX Sensitivity

Signal

Power
(dBm)

Component

Radio

Radio

Feed

Feed

Antenna

Antenna

Path Loss

EIRP (dBm)

TX Power (dBm)

Line Loss (dB)

Attenuation (dB)

–

Antenna Gain (dBi)

+

–

=

Содержание SEL-FR12

Страница 1: ...Identify the faulted line segment with fault detection and low latency communication while a fault is still active for use in protection schemes Enhanced Protection Make real time changes to the prot...

Страница 2: ...rview Easy Installation Install the SEL FT50 and SEL RP50 on live lines by using familiar line tools and techniques Flexible Integration Install the SEL FT50 SEL FR12 system in an existing relay prote...

Страница 3: ...to the SEL FR12 The SEL FR12 transfers the received signal to the recloser control or relay via MIRRORED BITS communications in as little as 6 ms The recloser control uses the fault information to ma...

Страница 4: ...es and achieve the benefits shown in Figure 2 Figure 3 depicts the key components of the FT50 0001 FT50 0003 FT50 0005 FT50 0006 models The other product variants FT50 0004 FT50 0007 have identical in...

Страница 5: ...r SEL RP50s and mounted on the same electrical phase Like the SEL FT50 for three phase systems the SEL RP50s will normally be installed in groups of three Up to five SEL RP50 sites may be used for eac...

Страница 6: ...ally off when the SEL FR12 is turned on or after it receives a clear link status command via MIRRORED BITS LINK LEDs illuminate when the SEL FR12 receives consecutive Link messages or one Fault messag...

Страница 7: ...recloser Each SEL FT50 label in Figure 7 represents three SEL FT50 Fault Transmitters one per phase Table 1 Target and Status LED Definitionsa a The FAULT and LINK LED operation changes during RSSI m...

Страница 8: ...L 651R recloser control or other SEL protective relay by using MIRRORED BITS communications The SEL FT50 SEL FR12 system allows the protective relay or recloser control to make intelligent decisions b...

Страница 9: ...th the highest rated fuse size pres ent on the system which is shown in green An intentional coordination margin allows for prefault load and variances in fuse construction For faults on sections of t...

Страница 10: ...xample fault shown in Figure 10 the recloser control enables the recloser control fast curve see Figure 8 Compare this to when a fault is on the same unfused line section but the recloser control does...

Страница 11: ...g working safety These feeder cables radiate from a substation continuing for a few feet to one mile These cables are usually terminated on a riser pole and then connected to the overhead conductors T...

Страница 12: ...12 shows a substation one line diagram with a recloser on each feeder Retrofitting a traditional fast bus tripping scheme to this type of substation might be expensive Instead of installing wiring or...

Страница 13: ...reclosers are set to delay their tripping Figure 13 shows a fault in Zone R1 In a conventional protection design assum ing the reclosers use a fuse blowing scheme R1 clears this fault but only after...

Страница 14: ...interfer ncias Canada DANGER Install fault transmitters and sensors in accordance with normal safe operating procedures These instructions are not intended to replace or supersede existing safety or o...

Страница 15: ...ce can cause electrical shock resulting in injury or death DANGER D brancher tous les raccordements externes avant d ouvrir cet appa reil Tout contact avec des tensions ou courants internes l appareil...

Страница 16: ...e between the SEL FR12 and each trio of collocated SEL FT50 devices the link between SEL FT50s and corresponding SEL RP50s between sequential SEL RP50 installations and between the SEL RP50 and SEL F...

Страница 17: ...see the SEL FT50 from the SEL FR12 antenna If you cannot see the SEL FT50 from the SEL FR12 antenna perform an area study to determine if the link will work properly Perform an area study starting at...

Страница 18: ...SEL FT50 installation site to check for local obstructions between the SEL FT50 and SEL FR12 If an obstruction does exist consider whether the SEL FT50 location could be moved to a nearby span to avo...

Страница 19: ...devices On Site Testing SEL FR12 Installation Install the network SEL FR12 at the identified site or set of sites and enable the radio before installing any SEL FT50 devices Follow the procedures in...

Страница 20: ...er than 5 A and the LINK LED does not assert after waiting the expected time the SEL RP50 Unit ID Network ID or Repeater ID setting might be incorrectly configured Path or area study modeling of groun...

Страница 21: ...h the ground symbol to a rack frame ground or main station ground for proper safety and performance Use 4 mm2 12 AWG or heavier wire of less than 2 meters 6 6 feet for this connec tion Make the ground...

Страница 22: ...existing mast 235 0233 9 15 dBi Gain Omnidirectional Antenna 902 928 MHz N Female Connector 2476 5 mm 97 5 in 33 3 mm 1 3 in 240 0106 for mounting to existing mast 235 0257 5 15 dBi Gain Omnidirection...

Страница 23: ...transmitter and fault receiver systems to operate in close proximity both the SEL FT50 and SEL FR12 feature a Network ID selection 1 16 See Figure 17 for an example of two networks Each SEL FT50 cont...

Страница 24: ...etect a fault the Unit ID assignments for those SEL FT50 Fault Transmitters should be unique This avoids situations in which SEL FT50 Fault Transmitters with a shared Unit ID broadcast fault messages...

Страница 25: ...L FT50 set Control Switches 11 14 to the Low Gain position and use the RSSI feature see Receive Signal Strength Indicator on page 26 to measure the receive signal strength for each trio If the receive...

Страница 26: ...1 illuminates to indicate that you are reading the RSSI for the link between the SEL FR12 and the SEL FT50 with Unit ID 1 Press the TARGET RESET pushbutton to sequence through Unit IDs 1 12 The LINK...

Страница 27: ...page 30 for details and then for two sec onds longer to get back to Normal mode The SEL FR12 will default to Normal mode automatically after 30 minutes Connecting the SEL FR12 to Other SEL Devices The...

Страница 28: ...FR12 supports two additional MIRRORED BITS com mand sets The command sets listed in Table 9 and Table 10 provide conditional responses Program the SEL 651R logic to evaluate the expression RMB1 OR RM...

Страница 29: ...e SEL FR12 receives a fault message from the SEL FT50 and deasserts thereafter this bit is not latched this differs from the SEL FR12 FAULT LEDs which are latched until reset Trio 1 FAULT Logical OR o...

Страница 30: ...lows you to see the switch positions of the device To enter Read Settings mode press and hold the TARGET RESET pushbutton two times the first press cycles through RSSI mode The control DIP switch sett...

Страница 31: ...sage each SEL FT50 transmits a Unit ID field as part of the message the Unit ID is a number from 1 to 12 The following lists the requirements when planning the Unit IDs to use in a sys tem Unit IDs ca...

Страница 32: ...xpressed in primary amperes Because the SEL FT50 measurement accuracy is not as accurate as a relay take care when choosing your fault pickup settings The measurement accuracy for each trip threshold...

Страница 33: ...configure the Unit ID Network ID and the Repeater ID The SEL RP50 only reads settings during startup changing settings while the unit is turned on has no effect Changing settings requires removal of...

Страница 34: ...50s is installed and SEL RP50s are needed for the other trios they too must be set to Unit IDs that match the SEL FT50 Unit IDs and mounted on the same electrical phase See Appendix D SEL RP50 Fault R...

Страница 35: ...R12 it is permissible to use Repeater IDs 2 4 and 5 but not 2 5 4 See Appendix D SEL RP50 Fault Repeater Detailed Implementation on page 54 for more examples of settings the Repeater ID Do not use the...

Страница 36: ...until the device is secured around the line as shown in Figure 25 Step 4 Use the shotgun stick to adjust the transmitter orientation so that it is directly vertical This is important to ensure the be...

Страница 37: ...ansmitter and Receiver System Dimensions Dimensions Figure 26 SEL FT50 Dimensions for FT50 0001 FT50 0003 FT50 0005 FT50 0006 U S A Canada Peru Australia New Zealand and Brazil SEL FT50 i9373a LEGEND...

Страница 38: ...38 SEL FT50 SEL FR12 Fault Transmitter and Receiver System Instruction Manual Date Code 20210405 Dimensions Figure 27 SEL FT50 Dimensions for FT50 0004 FT50 0007 Europe and Mexico i9358a...

Страница 39: ...al SEL FT50 SEL FR12 Fault Transmitter and Receiver System Dimensions Figure 28 SEL RP50 Dimensions for RP50 0001 U S A Canada need updated drawing SEL FT50 i9373a LEGEND in mm BOTTOM FRONT RIGHT REAR...

Страница 40: ...40 SEL FT50 SEL FR12 Fault Transmitter and Receiver System Instruction Manual Date Code 20210405 Dimensions Figure 29 SEL FR12 Dimensions...

Страница 41: ...Overvoltage Category III SEL FT50 and SEL FR12 Insulation Class SEL FT50 SEL RP50 Class III SEL FR12 Class I System Power System Frequency Range 45 65 Hz Current Pickup Level rms Note Units are indiv...

Страница 42: ...6 km 1 mile line of sight RP50 0001 to RP50 0001 As far as 0 8 km 0 5 miles line of sight RP50 0001 to FR12 0001 As far as 0 8 km 0 5 miles line of sight Communications Port EIA 232 One rear Port Dat...

Страница 43: ...an Union CE Mark Australia and New Zealand FT50 0005 ACMA RCM Brazil FT50 0006 Anatel 05386 20 12987 Mexico FT50 0007 IFETEL RCPSCSE17 1114 A1 Table 14 Frequency Mapping by Country Unit ID Frequency M...

Страница 44: ...r Brazil in Safety Information Added FT50 0006 Brazil to Table 11 Fault Pickup Accuracy Considerations for FT50 0001 FT50 0003 FT50 0006 U S A Canada Peru and Brazil Updated Figure 23 SEL FT50 Dimensi...

Страница 45: ...adio Interference From Adjacent Networks Receive Signal Strength Indicator and Read Settings to SEL FR12 in System Installation Updated General and Radio System in Specifications Added Peru Australia...

Страница 46: ...set above 200 percent of the load current In this example the fuse size is 140 T the SEL 651R 51 element pickup is 550 A and the settings from Table 16 apply D switch is in the DOWN or OFF position U...

Страница 47: ...this instruction manual See SEL application guide Using the SEL FT50 SEL FR12 System to Selectively Permit Accelerated Tripping in the SEL 651R Recloser AG2017 30 available at selinc com Table 17 Set...

Страница 48: ...diated Power Requirements FCC and IC regulations for 900 MHz ISM industrial scientific and medical band radios such as those used by the SEL FT50 place limits of 30 dBm on maximum radio transmit power...

Страница 49: ...n 3 Table 20 shows the 915 MHz FSPL for some typical path distances Equation 3 Obstruction Loss Path loss caused by obstructions needs to be factored into link budget calcula tions when there are obst...

Страница 50: ...12 20 dB of obstruction loss can be added to the link bud get When obstructions occur on the direct path between the transmitting and receiving antennas more than 20 dB of obstruction loss may need t...

Страница 51: ...e of nearby reflective surfaces When a direct line of sight path does not exist between the transmitter and receiver multi path fading can cause 20 dB or more of signal loss Interference Margin The SE...

Страница 52: ...R12 Antenna 7 15 dBi 3 05 m 10 ft of LMR 400 Coaxial Cable 0 39 dB Radio Surge Protector SEL part number 200 2004 0 25 dB Path Obstruction Loss 5 dB Polarization Loss 0 dB Fading Loss 6 dB Interferenc...

Страница 53: ...tion D 6 Effective RX Sensitivity dBm 97 dBm 6 dB Effective RX Sensitivity dBm 91 dBm Link Margin Equation D 7 Link Margin dB 84 3 dBm 91 dBm Link Margin dB 6 7 dB A link margin of 6 7 dB is likely to...

Страница 54: ...three SEL RP50s installed on the same branch in a location with a good line of sight to both the SEL FT50s and the SEL FR12 antenna will enable the signals from this SEL FT50 trio to get around the ob...

Страница 55: ...Only one SEL RP50 can be used with any SEL FT50 manufactured before May 2021 use he repeater ID Legacy setting Refer to Figure 34 for a settings example for simple SEL FT50 SEL RP50 and SEL FR12 syst...

Страница 56: ...ons energy harvest ing still occurs From the Off state and the Sleep state a power system fault will wake up the SEL RP50 almost instantly and it will be listening for a fault message from the SEL FT5...

Страница 57: ...eless receiver is on all of the time If the load current later drops below the level needed to remain in the Awake state the SEL RP50 will remember the synchronization and should be able to keep trans...

Страница 58: ...ng Laboratories Inc reserves all rights and benefits afforded under federal and international copyright and patent laws in its products including without limitation software firmware and documentation...

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