Download Loop Sectionalization Automation Scheme

Loop-Sectionalizing
Automation Scheme
Colin Hawthorne
4/26/2016
CNP Automation Scheme History

Prior to 2010, the only automated switching
devices installed on CNP’s grid were SCADA
controlled pole-top switches and a mix of
SCADA controlled and non SCADA controlled
reclosers.

In most cases, after a lock out event, our
dispatch team would remotely operate these
devices to restore power to the unaffected
sections. This manual process requires
diligent coordination with the truck crews and
is ultimately very time consuming.

Aside from protecting overhead equipment,
these devices were installed to segment
feeders that were performing poorly, splitting
their customers and load in halves, thirds or
quarters.

With this in mind, our goal was to develop an
automated scheme to improve restoration
time.
Remote Controlled Pole-Top Switch
(PTS)
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Department of Energy Project

From 2010 to 2013, the Department of Energy (DOE) Smart Grid
Investment Grant (SGIG) contributed to an initiative to install newer
types of reclosers as an attempt to further automate the grid.

CNP strategically deployed over 500 of these newer reclosers
throughout our service territory, initially concentrating on the urban
portion of the service area, and then expanding to the poor
performing and heavily populated circuits.

Using these newer reclosers, we developed a more intelligent and
secure device.
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Intelligent Grid Switching Devices
•
•
IGSD is a term used for a recloser that can be programmed to operate
as 2 of the following functionalities, which can be remotely toggled:
•
Recloser
•
Sectionalizer
•
Remote Controlled Switch
The Loop-Sectionalizing Scheme (LSS) is a supplement to these
functionalities. LSS is used in overhead distribution circuits to automate
the power restoration of the unaffected sections of a circuit after a
protection device has locked-out.
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What is Loop Sectionalizing?

The underlying logic of the LSS scheme is, by using IGSDs, a circuit can be
automatically sectionalized, which is followed by closing the N.O. tie IGSD to
restore power to the unaffected sections. This logic relies on the loss-of-voltage
sensing capability and countdown timer of each IGSD.

Enabling LSS on an IGSD will allow it to automatically operate a Close or Trip,
depending on it’s normal configuration, after it sense a loss-of-voltage for a set
amount of time.

Normally closed IGSDs with LSS are usually set to operate a trip usually after 30
seconds. Normally open IGSDs with LSS are usually set to operate a close after
40 seconds.
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Loop-Sectionalizing Scheme
Simulation
HOW DOES THE LOOP SECTIONALIZING
SCHEME WORK?
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LSS Fault Scenario 1: First Zone
L.O.V.
TIMER
(sec)
BACK UP
CKT #3
BACK UP
CKT #1
Locked
Out
BACK UP
CKT #2
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LSS Fault Scenario 2: Second Zone
L.O.V.
TIMER
(sec)
BACK UP
CKT #3
BACK UP
CKT #1
Locked
Out
BACK UP
CKT #2
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LSS Fault Scenario 3: Third Zone
L.O.V.
TIMER
(sec)
BACK UP
CKT #3
BACK UP
CKT #1
Locked
Out
BACK UP
CKT #2
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LSS Fault Scenario 4: Last Zone
L.O.V.
TIMER
(sec)
BACK UP
CKT #3
BACK UP
CKT #1
Locked
Out
BACK UP
CKT #2
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Benefits
Benefit metrics are based on outages where Loop-Sectionalizing was
used.
Full LSS Substation Benefits of Automation
2013
2014
2015
3,996,714
5,908,751
3,162,487
1.64
2.37
1.32
150.4
207.4
113.6
Sustained Customers Saved
41,927
45,362
27,272
System SAIFI Saved
0.0172
0.0181
0.0113
Substation SAIFI Saved
1.5776
1.5926
0.9799
Customer Minutes Saved
System SAIDI Saved
Substation SAIDI Saved
Note these metrics are based on opportunities for savings, i.e., the more
outages, the more opportunities to save.
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Constraints

The LSS devices operate independently.
– Devices are time coordinated.
– Close in on fault, then open and lockout immediately (normal business)

Does not factor in temporary switching.
– LSS needs to be disabled by our dispatchers when the circuits are
temporarily switched.
– Need to remember to re-enable LSS afterward.

Necessary to wait for faults to investigate and test.

Not applicable across entire system.
–
Shorter circuits
–
Fewer customers
–
Circuits that perform well
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Lessons Learned: Example 1
For bi-directional open reclosers, issues can arise if both circuits have
fault within a few seconds of each other.
L.O.V.
On
N.O. recloser closed
too early
40 sec
L.O.V.
Off
Fault
on Ckt 2
0.1 sec
Close
Closed
and held
21 sec
21 sec
20 sec
Trip
0.1 sec
Fault
on Ckt 1
Time
Lockout
Breaker 1
Breaker 2
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Lessons Learned: Example 2
1.
A 3 phase fault occurred in Zone 1 of Circuit A.
2.
The L.O.V. timers on all IGSDs, except IGSD 3, started counting once the
fault occurred, and not after the breaker locked out.
3.
30 seconds pass, then IGSD 1 and IGSD 2 opened before the breaker
locked out.
4.
Another 10 seconds pass, then all 3 open-tie IGSDs closed, also before
the breaker locked out.
5.
This resulted in a parallel tie established between two neighboring circuits
in zone 3 and 4 of Circuit A.
Question 1: Why did the L.O.V. timers start counting before the breaker
operated?
Question 2: Why did the L.O.V. timer not start on IGSD 3?
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Lessons Learned: Example 2
Question 1: Why did the L.O.V. timers start counting before the breaker operated?
Answer: The under-voltage pickup values for the L.O.V. timers were set too high, so the timers
started counting when the 3 phase fault occurred, as oppose to when the breaker is opened.
Normal
IGSD U.V.
Setting
Voltage
Voltage
during
3 ph fault
Question 2: Why did the L.O.V. timer not start on IGSD 3?
Answer: The under-voltage pickup for the L.O.V. timer on IGSD 3 was too low, different than the other
IGSDs on Circuit A, so the timer never started counting.
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Lessons Learned: Example 2
L.O.V.
TIMER
(sec)
BACK UP
CKT #3
BACK UP
CKT #1
Going
Through
Locked
Reclosing
Out Cycles
BACK UP
CKT #2
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Lessons Learned

Through our trials, we
have had to revise the
device settings to account
for various uncommon
scenarios.

Majority of failed LSS
attempts have been due
to temporary switching.
This is corrected by
turning off LSS when
temporary switching is
needed.
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Next Steps

Continue to test and analyze results

Expand to other feeders and substations

ADMS solution

Peer to peer communications
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Summary

The Loop-Sectionalizing Scheme (LSS) is used to
automate the power restoration of the unaffected
sections of a distribution circuit after a protection device
has locked-out.

Have seen benefits of up to 5.9 million customer minutes
saved.

Loop-Sectionalizing is a scheme where:
– Devices operate independently
– Devices are time coordinated
– It’s assumed that circuits involved are switched normally
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Questions?
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