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HIGH VOLTAGE CABLE ACCESSORIES- Application, Design, Installation, Testing -

Ivan JovanovicG&W Electric Company

First detachable porcelain pothead for 4 kV systems

Year 1905

Terminations and joints from 5kV up to 345 kV for all cable types

Year 2015

ShanghaiDelhi

Toronto

San Luis Potosi

Chicago

Salvador

Any sections of Transmission and Distribution lines may be underground

Application of Underground Cables

Examples of cable installation

Directly buried or in conduits in trenches

Examples of cable installation

Laid on trays in tunnels

Examples of cable installation

Laid on trays under bridges

Examples of cable installation

Laid on sea floor or river bed – Submarine cables

Cable accessories

HV Power Cable

Outdoor termination Equipment

mount termination

Joint

Distribution of electrical stress in power cable

Conductor Conductor screenscreen

Insulation screenInsulation screen

scrODcondODinsODins

VscrEins

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2.•

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Cable Endinside termination

Cab

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ctor

Cab

le in

sula

tion

Cable end in accessory– how does it work?

Cab

le c

ondu

ctor

Cab

le in

sula

tion

Cab

le in

sula

tion

scre

en

Cable End withoutInsulation screen stripped back

Stress cone ground electrode

High stress at conductor High stress at insulation screen Stress evenly distributed

Cable End withInsulation screen stripped back

Cab

le c

ondu

ctor

Cab

le in

sula

tion

Stress cone insulation

Edge of cable insulation screen

Extruded Cable

Conductor

Screen

Insulation

MetallicSheath

ScreenWires

Jacket

Screen

OUTDOOR TERMINATIONS

GIS & Oil Immersed TERMINATIONS

JOINTS

Use of outdoor terminations

• Cable terminations connects power cable to other electrical components:– Overhead lines– Station buses

Structure-mount outdoor terminations in substation

Termination

Pole mount outdoor terminations on transmission Pole mount outdoor terminations on transmission line poleline pole

Termination

Typical design of outdoor termination

Distribution of electrical stress in the critical areas

Deflector radius

Deflector angle

Interface between stress cone and cable insulation

Outdoor Termination

Silicone Rubber Stress Cone

Insulating Rubber

Conductive Rubber (Deflector)Oil seal

Sleeve

Use of equipment mount cable termination

GIS cable termination connects the cable to the gas insulated switchgear (GIS) Oil-immersed termination connects the

cable to power transformer

GIS terminationsGIS terminations

GIS Housing

GIS Termination

Typical design of dry type GIS termination

Cable support

Compression spring assembly

Clamping ring

Stress cone

Epoxy insulator

Connector

Corona shield

Cable

Contact pad

Entrance housing

GIS interface plate

Design considerations

Per international and domestic standards it is required that terminations and GIS gear are interchangeable regardless of who made them. G&W GIS terminations meet that requirement.

Joint Design - General

HV electrode

Joint outer screen

Ground electrode (deflector)

Shield Break

Cable semi-con screen

Design - Electrical

Electrical stress inside the joint

Design - ElectricalMagnitude of electrical stress in the critical areas

Deflector angle

Deflector top

Corona shield

Use of Joint in Cable Bonding

• Cable bonding functions:– Limit cable metallic screen voltages– Reduce or eliminate the screen losses– Maintain a continuous ground path to permit

fault-current return and adequate lightning and switching surge protection.

Multiple Point Bonding

• Lower load rating of cable system

• Zero voltage at both cable ends (no safety hazard)

Induced current in screenInduced current in screenLoad currentLoad current

Cable metallic Cable metallic screenscreen

Single Point Bonding

• Induced voltage at open cable end (safety hazard)

• Higher load rating of cable system

Indu

ced

Volta

geIn

duce

d Vo

ltage

in sc

reen

in sc

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Cable lengthCable length

Voltage at open end Voltage at open end (In US 100(In US 100--200V Max)200V Max)

Cross Bonding – use of shield break joints

• No induced voltage at open cable end (no safety hazard)

• Higher load rating of cable system

Location of shieldLocation of shield--break jointsbreak joints

Paper Cables

PIPE

OIL orGAS

PAPER CABLES

OUTDOOR TERMINATIONS EQUIPMENT TERMINATIONS

Straight Joints

Stress in paper cables

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DcDiLn

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DcCable conductor

Cable insulation

Joint insulation

Stress cone(L-L profile) Formula for axial

component of electrical field at the stress cone

Di

Oil-impregnated paper cable

Relevant forconnector design

Relevant forStress cone design

• Retrofit of the old termination with new one

HV Transition Joints•Definition: Device for connecting HV oil-impregnated paper cable to solid dielectric cable•Typical application:

•To expand existing UG transmission network•To replace ailing section of old oil-impregnated paper cable with new extruded cable

HV Transition Joints•Relatively small usage, expected to grow significantly•Up to 161 kV class, many different designs in operation•At 230 kV most designs are “back-to-back”•Limited use and availability at 345 kV•High pressure vs. Low pressure (in regard to insulating fluid at paper cable side)

Back-to-Back with two Insulators(CIGRE TB 415)

Equipment type terminationfor paper cable

Gas or liquid

Connector Corona shields

Housing

Extruded cable Paper cable

Equipment type terminationfor extruded cable

Back-to-Back with one Insulator

GIS or Transformertype terminationGas or insulating

liquid

Connector

Corona shield Housing

Conductor Seal

Stress cone

Extruded cable Paper cable

Composite design

Epoxy insulator with built-in HV electrode

Paper cable

Stress cone

Paper cable stress cone

Housing Gas or liquid

SpringsConnector

Extruded cable

Tinned Cu housing

Stainless steel housing

Extruded cable

Paper cable

Connector clamp

Stress cone(paper roll)

Insulating fluid

Dry-Type Termination

Single-core Transition Joint for SCFF Cable

Back-to-Back with One Insulator

Stress cone installation with perforated Paper Roll

Paper is torn along factory cut perforations

Stress cone slope

Paper roll(stress cone)

Finalizing the stress cone

Copper mesh is applied over the slope

Copper band

Field Installation

Final installation step: Oil filling of the single core 138 kV LPOF to XLPE transition joints in the field

Three-core Transition Joint

Telescoping housing suitable for short manholes

Oil breach assembly

3-C Paper

cable

Spider assemblyreinforced to prevent TMB

Paper roll and crepe paper tape build-up

Dry-type GIS terminations

Installation of 3/C Transition Joint

Bushing of the dry-type termination

Design Tests per IEEE 404138 kV HPFF Transition Joint

Pipe-type cable

Extruded cable in conduitHPFF transition joint

HPFF transition joint

Accumulator

Extruded cable

Number of samples: 2AC voltage: 1min and 24hImpulse voltageIonization factorLoad Cycling

Installation of Cable Accessories

Excerpt from International study on world-wide usage of HV cable systems

(CIGRE TB 177, Section 3 “Worldwide Usage of Accessories for HV Extruded Cables”, Page 29)

“The assembly of the accessories is the most vulnerable part of a project involving the manufacture and installation of a new cable circuit.”

Parts

Hot-melt tape

Connector

Semi-con tape, 25mm wide

Self-fusing Aqua-Seal tape

Self-fusing insulating tape

Tinned Cu grounding mesh

Semi-con tape, 50 mm wide

Sand paper #150 to #600 grit

String solder#18AWG Cu wire

Joint body expended onto spiral core tube

Gloves

B/M and installation instructionsHeat

shrinkable tubing

PVC tape

Installation Steps1. Cable preparation / Preparacion del cable2. Connector crimp / Ponchado del conector3. Connector tape fill / Encintado con cinta

semicontora sobre el conector4. Shrinking of the joint body / Contraccion del

empalme5. Taping and grounding / Encintado y Aterrizado6. Outer joint protection / Colocacion de la manga

termocontractil y (si es necesario) la cubierta de cobre

Cable preparation• Prepare cable ends per installation

instructions / Preparacion del cable de acuerdo a instruccines de instalacion

Connector crimp

• Slide the connector onto cable conductor

Connector crimp• Butt the conductors into the connector

Connector crimp

Connector crimp

Shrinking of the joint body

• Clean cable insulation and apply grease

Shrinking of the joint body

• Position the joint and start pulling the cord

Shrinking of the joint body

Shrinking of the joint body• Check the position of the joint relative to the positioning

marks

Taping and grounding

• Apply semi-con tape and insulating tapes over the joint per instructions

Taping and grounding• Apply copper mesh over the semi-con

tape and solder to cable metallic sheath

Outer joint protection

• Heat shrink tube• Copper housing and / or fiberglass coffin

are optional

Outer joint protection• Position heat shrink tube over the joint

Outer joint protection• Apply heat uniformly to shrink down the tube

Mechanical Shrink Installation Method for Stress Cones and Joints

for Extruded Cables•Main drivers:

•Minimizes chances for field errors and damage•Reduces required space, installation time and cost

Mechanical Shrink Installation Method for Stress Cones and Joints

for Extruded Cables

Scone sliding.avi GW Mechanical Shrink Accessories-live demonstration.MPG

Cable prep: Accommodates for slip on the parking side, requires re-jacketing

Typically no need for additional re-jacketing

SLIP-ON

MECHANICAL SHRINK

Parking: Joint body is pushed onto the cable; requires special tool and extra time and space

Joint body is parked onto the cable, no tool required

MECHANICAL SHRINK

SLIP-ON

Final positioning: Joint body is pushed back the cable; requires special tool, creates mechanical stress

Joint body is positioned and cord is removed, no tool is required

SLIP-ON

MECHANICAL SHRINK

SLIP-ON

MECHANICAL SHRINK

Process and Tooling design

• Molding process – Parameters– Flow rate– Temperature– Pressure

• Molding process – Variations– Material (properties, quality issues)– Operators (degree of process automation, skill

set, training)– Equipment variations

• Need to build process robust enough to compensate for the variations

Comparison of

Different Specifications for Cable

Accessories and Cable Systems

Cable, Accessory & System StandardsGoverning

BodyStandard Current

EditionICEA ICEA S-108-720 Standard for Extruded Insulation Power

Cables Rated Above 46 through 345 kV2012

IEC IEC 60840 Power cables with extruded insulation and their accessories for rated voltages above 30 kV (Um = 36 kV) up to 150 kV (Um = 170 kV) - Test methods and requirements

2011

IEC IEC 62067 Power cables with extruded insulation and their accessories for rated voltages above 150 kV (Um = 170 kV) up to 500 kV (Um = 550 kV) – Test methods and requirements

2011

AEIC AEIC CS9 Specification for Extruded Insulation Power Cables and Their Accessories Rated Above 46kV through 345 kV AC

2006 /(2013)

IEEE IEEE 48 IEEE Standard for Test Procedures and Requirements for Alternating-Current Cable Terminations Used on Shielded Cables Having Laminated Insulation Rated 2.5 kV through 765 kV or Extruded Insulation Rated 2.5 kV through 500 kV

2009

IEEE IEEE 404 IEEE Standard for Extruded and Laminated Dielectric Shielded Cable Joints Rated 2.5 kV to 500 kV

2012

Tests Requirements for Individual Components

IEC 60840, Section for cables

IEC 60840, Section for cable accessories

ICEA S-108-720 for cables

IEEE 48 (US accessory makers and users) for terminations

IEEE 404 (US accessory makers and users) for Joints

Tests Requirements for System IEC 60840 (International) section for cable systems

IEC 62067 (International) section for cable systems

AEIC CS9 (US utilities) for cable systems

Definitions• Design Test – Used in IEEE 48 and 404 to describe test

sequences to qualify termination or joint for use on any cable with same or lower size / stress level. Equivalent to “Type tests” in IEC.

• Type Test – Used in IEC standards for a component test (cable, termination or joint) or cable system test in order to qualify component or a system.

• Qualification Test on Complete Cable System – Used in AEIC specification to describe a Type Test (as described in IEC).

• Prequalification Test – Used in IEC and AEIC standards for a long term cable system test including different installation conditions (flexible and rigid, direct burial, tunnel and conduit) to demonstrate performance of a system.

Industry Standards – New Developments in IEEE

•IEEE 48 “Standard for Test Procedures and Requirements for AC Cable Terminations Used on Shielded Cables Having Laminated Insulation Rated 2.5 kV through 765 kV or Extruded Insulation Rated 2.5 kV through 500 kV” Rev 2009

•IEEE 404 “Standard for Extruded and Laminated Dielectric Shielded Cable Joints Rated 2.5 kV to 500 kV” Rev 2012

•IEEE 48 and 404 will be combined:•IEEE 48/404 for Distribution (up to 46 kV)•IEEE 48/404 for Transmission (69 kV and up)

Industry Standards – New Developments in IEEE

•New split – combines accessories, splits voltage levels:

•Combine Terminations and Joints into one document•Split Distribution and Transmission•Two new IEEE standards

•Two new DGs were approved; First session @ ICC Fall meeting 2015

Design and Type tests

LOOP #1Initial tests per IEEE 48 (terminations)Very tough requirements, up to 4Uo

LOOP #2Type tests per IEC (system test)Type tests per AEIC (system test)Type test per ICEA (cables) Remaining type El. tests per IEEE 48El. Type test per IEEE 404 (joints)

- Outdoor with composite insulator- Outdoor with porcelain insulator- Two Oil filled GIS- Two Dry Type GIS- Two Cable types

The same loop plus four joints:Two without shield break in waterTwo with shield break in airTotal ten accessories, two cable types

IEEE 48 and 404 Test Loop

G&W HV Lab

G&W HV Lab

PQ test field

Conclusions• HV Cable Accessories – Terminations and Joints – are the

critical link in any modern cable system• There are many different designs that can work with any

modern cable designs that follow latest cable standards• Oil-filled cables (OF) are still dominant technology that has

been field proven over the years• Transition joints are becoming increasingly important as

new solid dielectric cables are being utilized• Installation of is tying together cables and accessories and

highly qualified jointers are a must!• New developments in standardization are critical for further

successful applications of cables and their accessories