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. 2 Remote Controlled Pole-Top Switch (PTS)

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. 3

Intelligent Grid Switching Devices 4 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.

What is Loop Sectionalizing? 5 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.

Loop-Sectionalizing Scheme Simulation HOW DOES THE LOOP SECTIONALIZING SCHEME WORK? 6

LSS Fault Scenario 1: First Zone 7 LockedOut BACK UPBACK UP CKT #1CKT #1 BACK UPBACK UP CKT #3CKT #3 BACK UPBACK UP CKT #2CKT #2 L.O.V.TIMER(sec)

LSS Fault Scenario 2: Second Zone 8 LockedOut L.O.V.TIMER(sec) BACK UPBACK UP CKT #1CKT #1 BACK UPBACK UP CKT #3CKT #3 BACK UPBACK UP CKT #2CKT #2

LSS Fault Scenario 3: Third Zone 9 LockedOut L.O.V.TIMER(sec) BACK UPBACK UP CKT #1CKT #1 BACK UPBACK UP CKT #3CKT #3 BACK UPBACK UP CKT #2CKT #2

LSS Fault Scenario 4: Last Zone 10 LockedOut L.O.V.TIMER(sec) BACK UPBACK UP CKT #1CKT #1 BACK UPBACK UP CKT #3CKT #3 BACK UPBACK UP CKT #2CKT #2

Benefits Benefit metrics are based on outages where Loop-Sectionalizing was used. 11 Note these metrics are based on opportunities for savings, i.e., the more outages, the more opportunities to save.

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 12

Lessons Learned: Example 1 For bi-directional open reclosers, issues can arise if both circuits have fault within a few seconds of each other. 13 Time Trip Close Fault on Ckt 1 Lockout Fault on Ckt 2 Closed and held L.O.V. Off L.O.V. On Breaker 1 Breaker 2 40 sec 0.1 sec 21 sec 20 sec 21 sec N.O. recloser closed too early

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 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? 14

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. 15 Normal IGSD U.V. Setting Voltage during 3 ph fault Voltage 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.

Lessons Learned: Example 2 16 LockedOut BACK UPBACK UP CKT #1CKT #1 BACK UPBACK UP CKT #3CKT #3 BACK UPBACK UP CKT #2CKT #2 L.O.V.TIMER(sec) Going ThroughGoing Through Reclosing CyclesReclosing Cycles

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. 17

Next Steps Continue to test and analyze results Expand to other feeders and substations ADMS solution Peer to peer communications 18

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 19

Questions? 20