Transcript ftp.so-ups.ru

Updated Transmission Line
Protection Communications
Roy Moxley, Ken Fodero, and Héctor J. Altuve
Schweitzer Engineering Laboratories, Inc.
Copyright © SEL 2008
Critical Clearing Times Never Seem to
Increase Because Generation Is
Remote From Loads
Reduce the Times You Control
Communications-Assisted Protection
Blocking Zone / Zone 3
Differential Zone
Zone 1
Relay 1
Zone 2
Relay 2
Communications
Scheme and Media Must Match
Transmit Permission
POTT Logic
Zone 2
Trip Permission
Received
AND
Zone 3 (Reverse)
DCB Logic
AND
Trip
Transmit Block
PU
Zone 2
DO
Block Received
AND
Trip
Can We Transmit Through a Fault?
Photo courtesy of Niagara Mohawk,
a National Grid Company

Signal attenuation
problems

Arc noise interference

Common mode failures
Power Line Carrier


Strengths

Protection owned

Single function

High signal-to-noise ratio
Weaknesses

Must transmit through fault

Only transmits single bit
Optical Fiber


Strengths

Unaffected by arcs or
ground potential rise

Wide bandwidth
Weaknesses – shared
resource
Spread-Spectrum Radio

Strengths

Weaknesses

Low cost

Line of sight required

No licensing required

Interference possible
Licensed Radio


Strengths

Exclusive ownership of frequency

Independent of line path
Weaknesses

License required

Line of sight required
Let’s Look at Relay Reports

POTT


Multiplexed fiber

Digital communication

Contact inputs
Spread-spectrum radio

DCB – power line carrier

Line current differential – licensed radio
Key to
Receive:
1.5 cycles
Contact input
over multiplexed
fiber with
DTT card
Key
Receive
Key to
Receive:
0.375 cycles
Receive
Key
Digital input over
multiplexed fiber
with low-speed
data card
Digital Is Faster Than Contact
1.5
cycles

0.375
cycles
Contact
Digital

Contact

Contact time

Input time

Debounce time
Digital

Integral error checking

Direct input to logic
POTT Over Spread-Spectrum Radio
CFE Mexico Experience

Transmission time: < 0.5 cycles

Correct trips: 12 of 12

Correct nontrips: 27 of 27
DCB Time
Coordination
Is Critical
Received
block just
in time
Received
block
too late
2.0 ms
between block
and unintended
operation
Get a Clock!!

Hours spent
correlating
event reports

Settings need to
be coordinated
with accuracy

Troubleshooting
improved after
questionable
operation
FAQ: Can We Put Line Current
Differential Over Radio?

Requires 56/64 Kbps channel

Needs to be secure and reliable
ISM Band
Tested Radio System

Licensed 900 MHz radios

Interleaving removed – much faster, no errors

Nonrecommended semiparabolic antenna
worked great

Radio and relay from different manufacturers
Choose Correct Antenna for Application
3 miles
Snowfall on June 10th
Good Test of Current Differential Over Radio
Licensed Radio Current Differential Test
Was a Big Success
No
failures
No lost
packets
2 ms
transmission
Conclusions
Fiber Is Great for Most Applications

Cost and availability is a drawback

Digital data is faster than contacts
Spread Spectrum Is Proven

Subcycle transmission times

Reliable and secure performance

Reasonable cost and installation
Licensed Radio Is Reliable and Fast for
Line Current Differential

License attainment is not difficult if frequency
is available

Transmission is fast (2 ms)

Protection is secure and reliable with care
Considerations

Ensure communication is appropriate to
scheme and vice versa

Test and monitor communications

Verify performance with clocks
Thank You!