Instruction Manual
Table Of Contents
- Major Features and Benefits
- Functional Overview
- System Overview
- Application Examples
- Collect Fault Information From Remote Branches
- Improve Fuse Coordination
- Fuse-Blowing Scheme Shortcomings
- Improve Fuse-Blowing Schemes With the Fault Transmitter and Receiver System
- Fuse-Saving Combined With Fuse-Blowing Schemes
- Improve Feeder Cable First-Span Protection
- Implement a Low-Cost Fast Bus-Tripping Scheme
- Tripping the Right Recloser Faster
- Safety Information
- Network Deployment Overview
- Device Installation
- Dimensions
- Specifications
- Appendix A: Manual Versions
- Appendix B: Two-Branch Application
- Appendix C: Link Budget Analysis
- Appendix D: SEL-RP50 Fault Repeater Detailed Implementation
- Technical Support
50
SEL-FT50/SEL-FR12 Fault Transmitter and Receiver System Instruction Manual Date Code 20210405
Appendix C: Link Budget Analysis
radius of 4.96 m (16.27 ft). For a distance of 16 km (10 mi) between antennas, the
Fresnel zone radius is 36.21 m (118.8 ft). Table 21 provides the Fresnel zone
radius for some typical path distances.
Equation 4
When you have a clear line of sight, with no obstructions within the first Fresnel
zone of the radio link, no obstruction loss value is needed in the link budget cal-
culation. Anything within the Fresnel zone (the ground, buildings, vegetation,
etc.) will add obstruction loss to the link budget calculation. When more than
80 percent of the Fresnel zone radius is free of obstructions, 0–3 dB of loss can
be added to the link budget to account for obstruction loss. When 50–80 percent
of the Fresnel zone radius is free from obstructions, 6–12 dB of obstruction loss
can be added to the link budget. When less than 50 percent of the Fresnel zone is
free from obstruction, 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 to be added to
the link budget.
Unlike other radios, which are often installed at base stations on mountain tops,
the SEL-FT50 and SEL-FR12 usually need to be positioned locally on a line at
the transmitter side and near a relay or recloser on the receiver side. Because of
this, you will often have obstructions, or the ground itself, in the Fresnel zone,
especially for longer links. You must keep in mind the above principles when
planning your links. The best rule of thumb is that if you can see the SEL-FT50
from the SEL-FR12 antenna, the link is likely to work.
Figure 32 Fresnel Zone
where:
b = radius of the Fresnel zone in meters
d = distance between transmitter and receiver in kilometers
f = frequency transmitted in MHz
Table 21 915 MHz Fresnel Zone Radius
Distance Between Antennas (d) Fresnel Zone Radius (b)
a
a
The Fresnel zone will be slightly larger for radios in the 860 MHz band.
300.0 m (984.3 ft) 5.0 m (16.4 ft)
1.6 km (1.0 mi) 11.5 m (37.7 ft)
6.4 km (4.0 mi) 22.9 m (75.1 ft)
d
b
d2
d1
b 547.7
d
4f
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