Intelligent Undergrounding at San Diego Gas & Electric

Intelligent Undergrounding at San Diego Gas & ElectricICC Educational Program – October 23, 2019 – Scottsdale, AZ by Jon Erickson San Diego Gas & Electric

© 2015 San Diego Gas & Electric Company. All copyright and trademark rights reserved.

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Service Territory

– 4100 square miles

– ~1.4 million electric customers

– ~10,700 circuit miles of underground distribution primary cable

– ~ 62% underground

– 1052 electric distribution circuits ( 831 – 12 kV, 221 – 4 kV) 2

Topics

• Cable System Expansion

• Overhead to Underground Conversion

• Proactive Cable Replacement

• Substructure Water Removal

• Infrared Inspection

• 600 Amp Load Break Connector

• System Control and Data Acquisition (SCADA)

• Conclusions

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Cable System Expansion

• Subdivision and commercial development

– City of San Diego and other cities in service territory required underground service

• Overhead to underground conversion

– Developed in 1969 by the California Public Utilities Commission (CPUC)

– Called Rule 20

– Five different rules

• 20 A – Funded by utility customers

– Cities and county allotted money each year based on number of meters served by the OH electric system

– Cities and county determine areas to convert

– Areas converted must provide a benefit to general public

• 20 B – Smaller projects

– Funded by rates or private funds – funded by customers primarily

– Areas converted must be along public streets

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Cable System Expansion (cont.)

– Rule 20 (cont.)

• 20 C

– Smaller conversion projects funded by property owners

• 20 D

– Approved in 2014 by the CPUC

– Projects are exclusively for fire hardening

– The County of San Diego is primary recipient of allocations

– Only primary voltage conductor is converted – excludes secondaries

and services

– Uses ratepayer funds

– City of San Diego developed a program to convert all overhead lines to underground

• This program is funded 100% by customers residing within the City of San

Diego – a surcharge is collected

• Began in 2003

• Complete conversion in about 50 years

• City converts about 12 circuit miles per year

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Examples of Overhead to Underground Conversion

Before After

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Proactive Cable Replacement

• Unjacketed polyethylene cable installed beginning in 1963

– HMWPE installed from 1963 to 1979

• 1963 – 1979 - Copper conductor - 220 mil insulation

• 1974 – 1976 – Aluminum conductor – 175 mil insulation

– XLPE installed from 1968 to 1985

• Mainly 175 mil insulation – small amount of 220 mil insulation

– More than 99% of this cable installed in conduit

– Cable began failing at an increasing rate in the late 1980’s and early 1990’s

– Proactive cable replacement capital budget program established in 1994

– Extensive cable failure database established in the 1990’s – continues today

• Cable vintage

• Manufacturer

• Insulation type

• Cable length7

Cable Failure Rates

• Database used to establish failure rates for each cable vintage

– Rates determined for HMWPE feeder and lateral

– Rates determined for XLPE feeder and lateral

– Poor performing vintages were determined

• Oldest cable is not worst performing

– Worst performing cable is 1977 – 1983 XLPE

Feeder cable Lateral Cable

500 kCMIL copper #4 AWG copper

4/0 AWG copper #2 AWG copper

750 kCMIL aluminum #2 solid AWG aluminum

1000 kCMIL aluminum 2/0 AWG aluminum

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Cable Failure Rates

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Proactive Cable Replacement

• Between 1994 and 2016 the utility has replaced and average of

– 12.4 circuit miles of feeder cable each year

– 35 circuit miles of lateral cable each year

• Remaining unjacketed cable

– ~ 74 circuit miles of feeder cable

– ~ 1418 circuit miles of lateral cable

• Proactive cable replacement impact on cable failures

– Projected cable failures with no proactive replacement

– Projected cable failures with proactive replacement

– Possibly an additional 100 to 150 failures per year at the peak year without proactive replacement

– Reduction in annual SAIDI to the 65 minute range

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Impact on Cable Failures With Proactive Cable Replacement

Projected cable failures without

proactive cable replacement

Cable failures with proactive

cable replacement

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Substructure Water Removal

• Cities have restrictions on water being pumped from manholes and other substructures into gutters and storm drains

• Extended outage time waiting for pumper trucks

• Additional operating cost to the utility and its customers

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Automated Sump Pump Filters

• Filters sediment and hydrocarbon discharges

to surface water

• Polymers and filters prevent passage of

sediment and hydrocarbons providing

secondary containment in the event of a major oil release

• Filter media can be changed to target specific pollutants/constituents

• Maintains low water levels in substructures

• Approved by local water quality authority

• 25 Automated, filtered sump pumps installed in locations with

switches in support of quicker service restoration

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Dewatering Trailers

• Crews can begin dewatering versus waiting

for HazMat tanker trucks

• 500 gallon tank capacity – solids and

liquids

• 80 gallons of water storage

• Pressure unit with spray gun attached

• Can be used in conjunction with a filter

sock to discharge directly to a storm

drain

• Supports quicker troubleshooting and

service restoration

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Infrared Inspection

• A major safety concern of any personnel entering manholes or other subsurface structures with energized cable and connections is the integrity of the connections.

• Inspection with an infrared camera is the best way to check connections

Substructure with 600 amp and 200 amp connections

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Infrared Inspection Operating Practice

• Several years ago the utility implemented an operating practice to use an infrared camera to check all cable connections in a manhole/substructure prior to entering for any reason.

– Performed after proper venting of substructure for at least 10 minutes

• If water covers the connections process below is followed

– Pump water level below connection

– Take infrared reading

– Subsequent readings are taken every 5 minutes for 15 minutes to see if significant temperature rise has occurred

• Operating practice established several years ago for response time to correct an elevated temperature issue

– Based on connector temperature compared to temperature rise above cable temperature

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Temperature Response Guidelines –Premolded Connectors

• Utility response guidelines for premolded connectors

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Temperature Response Guidelines – Hand-Taped Splices

• Utility response guidelines for hand taped splices

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Examples of “Hot” 600 Amp Tee Connections

Adjacent Connector

used as reference –

temperature in °F

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Connecting plug

with elevated

temperature - °F

Examples of “Hot” 600 Amp Tee Connections

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Connecting plug with

elevated temperature - °F

Cable temperature about

80°F

Connecting plug with

elevated temperature - °F

Cable temperature about

90°F

600 Load break Connector

• 600 amp tees are very common in the utilities underground electric distribution system

– Total number installed in substructures – ~ 106,400

– Number installed in manholes - ~ 36,700

– Number installed in handholes - ~ 67,600

– Number installed in vaults ~ 2,100

• Tee failures result in potentially a large

number of customers being impacted

for an extended period of time

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Typical 600 amp tee installation

600 Amp Tee Installation (cont.)

• Manhole Examples

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600 Amp Tee Installation (cont.)

• Handhole Examples

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600 Amp Load Break Connector Types

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600 Amp Load Break Connector Utility Operating Practice and Operating Advantages

• Do not operate as a load break device

• Faster isolation of underground cable system compared to 600 amp tees.

• Provides a test, ground, and isolation point for 600 amp tees

• Can energize system up to one side of the connector to restore service more quickly than a 600 amp tee

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Installation History

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• Developed Construction Standard in July 2016 for rectangular design

– Revisions in June and October 2017

• Developed Construction Standard in March 2018 for square design

• Developed operating guidelines in August 2016

• First installation in October 2017

• Have installed 600 amp load break connectors in 148 manholes

• Since the installation of the 600 amp load break connector is classified as system betterment the cost can be capitalized

Application Guidelines

• Install in manhole or walk in vault only

• Consider circuits where a tee failure will impact a high number of customers

• Consider the age of the tees

• Do not install in a manhole that has a switch in the manhole or a connection to a pad mount switch

• May be able to be installed in handhole if switch is being replaced

• Install 600 amp load break connectors when 600 amp tees fail

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Field Installations

• Manhole – rectangular design

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Field Installations (cont.)

• Manhole – square design

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Field Installations (cont.)

• Handhole – rectangular design

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Other Applications

• 600 Amp Live Front Terminator Conversion to Dead Front

– Minimize the pad footprint for dead front equipment when converting existing live front to dead front

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System Control and Data Acquisition (SCADA)

• What is SCADA

– SCADA Control - The ability to monitor and control equipment remotely via radio communication

– Data Acquisition - The retrieval of information or data from the equipment being controlled and monitored

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SCADA Features

• Data Acquisition & Archiving

• Alarms & Events

• Graphical Operator Interface

• Real-time Control

• Database and Log Files

• Reports and Information Sharing

• View only access available

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SCADA Benefits

• Greater visibility of system

• Wider range of control

• Immediate response to events

• Data is readily available

• Easy to operate

• Time efficiency

• Reduced operational costs

• Forecasting & Trending

• Enables other technologies

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SCADA Disadvantages

• Complex to configure

• Human errors can have serious consequences

• Security risks

• False Alarms

• Data overload

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Utility SCADA

• The utility has greatly increased the use of the SCADA system throughout the overhead and underground electric distribution system in the past 30 years

• Allows operators to remotely operate switching devices to restore service faster

• SCADA is now being utilized with

– Substation circuit breakers

– Overhead and padmount/underground switches

– Overhead and padmount capacitors

– Line reclosers

– Line regulators

• First 3 substations were done in the mid 1980’s

• Deployment in downtown San Diego occurred in early 1990’s

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Utility SCADA

• 79% of the distribution circuits at the utility are SCADA controlled.

– 835 electric circuits

• 91% of the customers are electrically supplied from automated circuitry.

• 96% of the applicable distribution load curtailment circuits are SCADA controlled.

• 2 Separate SCADA Systems:

– Transmission

– Distribution

• 98/136 12 kV Substations on SCADA

• 2100+ SCADA Controlled Devices

• 41 different device types are connected to the SCADA system

• Utilizes 900 MHz encrypted radio system + Fiber + LTE for communication

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Available SCADA Data

• Voltage

• Phase and neutral current

• Watts

• Vars

• Battery voltage

• Fault indication for equipment installed from mid-1980’s until early 2000’s

• Fault targets for equipment installed after early 2000’s until now

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SCADA Deployment Guidelines

• Substation

• Circuit midpoint – based on 50% of the customer count

• Circuit tie switches

• Circuits with large number of customers

• Consider circuit outage history

• Consider urgent/critical customers on a circuit

• Installation at key meteorological boundaries based on wind speed history and the need to interrupt electric service in extreme fire risk weather

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Fault Location, Isolation and Service Restoration (FLISR)

• Self-healing grid

• Configured to either manual or automatic

• Circuit requirements:

– SCADA at breaker with fault targets

– SCADA at mid-point sectionalizing device with fault targets

– SCADA tie-switch

• Currently 441 circuits throughout the utilities service territory are in the manual mode that generates switching plans for operators

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Examples of Padmount & Vault SCADA Equipment

5 way padmount

4 way padmount5 way vault

4 way vault

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Examples of Polemount SCADA Equipment

Capacitor

Recloser Recloser

Switch

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Conclusions

• Utilization of these various procedures and programs have resulted in a very reliable electric system

• The utility has been named as the most reliable utility in the western United States for 13 years in a row

• Co-winner of the National Reliability award in 2018

• The utility will continue to look for ways to improve reliability in the underground electric distribution system as it expands

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Questions