REPORT SC B1 Insulated Cables 2010b1.cigre.org/content/download/61382/2778548/version/1/...Transmission.Itisfocused mainly on HV and EHV applications but MV cable applicationsare also

EELLEECCTTRRAA N° 253 - Décembre 201016

SC ANNUALREPORT

2010

SC ANNUALREPORT

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SC B1The first Study Committee dealing with power cables was founded in 1927

under the designation of SC2. It became SC 21 in 1967 and SC B1 in 2002, as

one of the five Study Committees dealing with subsystems (SC “B”).

During most part of its history, SC B1 (21) had focused its activities on

technical work and issued a large number of documents, including recommen-

dations to prepare IEC standardization, for example the IEC 62067, which was

urgently needed by Utilities to specify tests for qualification of 400 kV cable

systems. Following CIGRE new orientation towards enhanced satisfaction of

needs of target groups, SC B1 has extended its work to economical, environ-

mental and social aspects to better accompany the evolution of the EPI.

The field of activity of SC B1 is the development and operation of all types

of AC and DC insulated cable systems for Land and Submarine Power

Transmission. It is focused mainly on HV and EHV applications but MV cable

applications are also considered.

The scope of work of SCB1 covers theory, design, applications, manufac-

ture, installation, testing, operation, maintenance and diagnostics techniques

of insulated cables.

As already outlined in Electra magazine (April 2010), the future of power

systems is shaped by some important factors:

� the need to serve a growing demand of electricity

� the climate change and the development of carbon free generation

� the dearth and cost of energy

� the acceptability of power infrastructure.

The Activities of Study Committee B1 for the ten coming years will align

with four Technical Directions:

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SC B1

� Prepare the Power System of the future which will rely on a number of new

techniques,UHV,HVDC, Superconductors and embarkmore intelligence

� Make the best use of the existing equipment and system (upgrading)

� Preserve Environment (Life Cycle Assessment and Environmental Impact

Assessment)

� Develop Technical information (Publications and Tutorials)

Transmission power cables have a service life duration of several tens of

years, which is much higher than the time interval of the expected changes

towards Power Systems of the Future. Consequently, to fulfill the basic needs of

customers towards the supply of electric power with a high level of availability,

reliability, flexibility, quality and cost, the activities of SC B1 should perma-

nently address all the major steps of the service life of cable systems : design

(for new and future systems but also to upgrade or uprate existing ones), con-

struction and installation (with the goal to reduce costs and improve environ-

mental impact), testing and monitoring, operation (with reduced losses),

removal and end of life.

The design phase is the very first step towards a new cable system, where

the design engineer, from the input data given by the customer, can propose a

comprehensive system, which comprises components (cables and accessories),

construction and laying, accessory installation.

This design phase follows a step-by-step approach, which takes into

account both technical and environmental issues as described in Technical

Brochure 250 “Technical and Environmental Issues regarding the Integration

of a New HV Cable System in the Network”

The same approach has to be adopted when upgrading or uprating an

existing cable system as recommended by WG B1.11 (Upgrading and Uprating

of Existing Cable Systems) in a coming Technical Brochure expected for 2011.

In the system design approach, cable design, accessory design and installa-

tion design are interdependent.

For various reasons, to reduce the cost of a cable system, it is common

practice to try to reduce the number of joints and to increase the lengths of

cable that can be shipped on drums. That can be done by reducing the diame-

ter and/or the weight of the cable (reduction of thicknesses).

One option towards longer shipping lengths is to change the design of the

metallic water barrier/shield of the cable, for example by replacing “heavy”

designs using lead sheath by much“lighter” ones based on laminate coverings. In

this prospect, the publication of WG 21.14 “Guidelines for tests on high voltage

cables with extruded insulation and laminate protective coverings” dated 1992

has been recently updated by WG B1.25 which has prepared a new Technical

Brochure “Advanced design of metal laminated coverings: recommendation for

tests, guide to use, operational feed back“ which will be published early 2011.

This document includes a guide for non-technical readers.



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2010

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SC B1

Upgrading of existing lines may lead to connect cables of different types.

In this case, Transition Joints may be needed. Several designs are now available

depending on voltage, cables types, etc. The design of this equipment has to be

validated by appropriate testing procedure. In this prospect, WG B1.24 has

published in 2009 a Technical Brochure 415 “Test Procedures for HV

Transition Joints for Rated Voltages 30kV up to 500kV”.

The interface between cable terminations and GIS is currently ruled by

existing IEC Standards ; JWG B1.B3.33 will examine and evaluate the technical

issues of a common, dry type interface for GIS and power cables of 52 kV and

above.

From a utility perspective, the cable rating is one of the most important

requirements for a power cable. Therefore, utilities often focus on this subject

during the design and engineering phase. Later on, during the operation phase

of power cables, cables often become increasingly loaded and the attention is

also focused on cable rating. In these situations, it is becoming very important

to know the exact limitations regarding the cable rating.

These reasons lead to the need to establish an accurate cable rating for each

power cable system. IEC 60287 and IEC 60853 are dealing with the current rat-

ing of power cables in a stationary and a quasi-dynamic way. These standards

prescribe how the current rating can be calculated in several different cases but

lacks have been identified and WB B1.35 “Guide for rating calculations” has

been launched to recommend improvements in this field. Results are expected

in 2013.

In parallel, the impact of EMF on current ratings and on cable systems is

being studied by WGB1.23. Final report will be delivered in 2011 in a Technical

Brochure and some elements will be published earlier, during a CIGRE

Colloquium in Paris in March 2011 and during Jicable in June 2011.

It is well known that underground cables have significantly different elec-

trical characteristics than overhead lines, and that these differences should be

taken into account during cable system planning, design, and operation.

Reliable input data are necessary and accurate impedance calculations are of

the highest importance.WG B1.30 “Cable Systems Electrical Characteristics”

is in charge of investigating this field .The work is done with good cooperation

with WG C4.502 “Power Systems technical performance issues related to

application of long HVAC cables”.

Another major aspect of the design of cable system is the consideration

of the Environmental Impact of the system during its Life Cycle. Different

High Voltage Cable types as well as their associated civil works and installa-

tion techniques will not impact the environment in the same way. In order

to minimize such impact, it is important to develop the necessary tools that

would enable the engineers and the decision makers to compare the Global

Environmental Impact (GEI) of different High Voltage underground cable

systems over their life cycle. A preparatory TF B1.36 “Life Cycle Assessment

and Environmental Impact of Underground Cable Systems” is investigating

in this field.


The State of the Art has been published in Technical Brochure 194

“Construction, Laying and Installation for extruded ands Self Contained

Fluid Filled cable systems”. The special case of shared structures has been stud-

ied by WG B1.08 and published in Technical Brochure 403 “Cable Systems in

multipurpose or shared Structures”.

The peculiar issue of large conductor cross section cables and resulting

mechanical forces is currently being considered by WG B1.34 “Mechanical

forces in large cross section cable systems. The final report will be issued in

2013.

For many reasons, the trend will be to reduce the insulation wall thickness of

cables, and to increase the electrical stresses in cables and at the cable/accessory

interface. Quality of jointing is becoming of higher and higher importance for

the system’s reliability. State of the Art has been described and performance

issues have been addressed by WG B1.22 which has produced a Technical

Brochure “Cable Accessories Workmanship”which will be published in 2011.

Test procedures and requirements for new and installed cable systems are

of crucial importance and of highest common interest for suppliers and pur-

chasers. This has always been a central field of activity of SC B1 to prepare,

often on request of IEC, test recommendations.

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After several years of highly satisfactory practical application of IEC 62067

and IEC 60840 the question was raised whether or not the full set of long-term

prequalification tests need to be repeated when limited changes are brought to

prequalified cable systems.WG B1.06 has published CIGRE SC B1 recommen-

dations in TB 303: “Revision of Qualification Procedures for extruded HVAC

Underground Cable Systems”.

These recommendations have been considered by IEC TC 20/WG 16 in

revisions of respective IEC cable test specifications and new editions of the

respective standards will be issued in 2011.

Similarly, SC B1 had produced recommendations for testing extruded DC

cables in TB 219 “Testing of DC Extruded Cable Systems for Power

Transmissions up to 250 kV”. As voltages of extruded HVDC lines are increas-

ing, a new Working Group B1.32 has been launched to prepare an extension to

voltages up to 500 kV. The final report is expected in 2011.

After introduction of AC instead of DC tests for commissioning of extruded

land cable systems the question was raised how to test long extruded submarine

cables. WG B1.27 is preparing “Test Recommendations for XLPE AC

Submarine Cables from 170 kV to 500 kV”. The final report is expected in 2011.

Superconducting cable systems are currently at the development stage.

Some pilot installations have been put in service and the issue of their testing

has been raised. On request of IEC,WG B1.31 is preparing recommendations

which will be available in 2012.

Availability, reliability and optimal utilisation of an existing cable line is of

prime interest for the system operator. After successful commissioning state of

the art cable systems generally promise trouble-free service performance for

very long time, typically in the range of thirty to forty years, even longer.

However, such outstanding lifetime can only be expected when the system is

consistently safeguarded from detrimental external impact, e.g. overheating,

mechanical damage, chemical aggression or water ingress. Supporting means

for safe operational management and efficient utilisation of existing assets are

structured maintenance, monitoring of crucial system data and diagnostics of

potential weak points. Based on such information the operator shall be able to

estimate the system’s condition, its probable availability and reliability and

even its remaining life. Eventually he can draw conclusions whether or not

investments for refurbishment or replacement should be considered.

Comprehensive and unbiased information on reliability and service expe-

rience is considered essential to the cable industry as a whole as a reflection of

the actual situation throughout the cable world. In this prospect,WGB1.10 has

published an “Update of Service Experience of HV Cable Systems” in TB 379.

This survey reports the overall good behaviour of cable accessories.WG B1.29

will make a review of HV cable Accessories performance. Nevertheless, some

issues regarding integrity of accessories have been reported. WG B1.29 will

publish in a 2013report giving “Guidelines for maintaining the integrity of

XLPE transmission cable accessories”.


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2010

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SC B1


Different kinds of maintenance are practiced today by cable system owners

with the objective to keep the system’s operational availability as high as possi-

ble. Guidelines for structured maintenance, tailored to different types of

cable/accessory were described in TB 279 “Maintenance of HV AC

Underground Cable and Accessories”.

Fluid-Filled cables are very reliable and their service life must be extended

as long as possible. Cable suppliers are leaving this field of activity, and the

transfer of knowledge is becoming an important issue.WG B1.37 will produce

within three years a “Guide Operation of Fluid Filled Cable Systems”.

Third Party Damages on Underground and Submarine Cables are a very

serious problem in terms of systems availability and cost. Guidance has been

published by WG B1.21 to avoid or at least mitigate such damages (Technical

Brochure 398).

Monitoring and diagnostics are sources for condition assessment and thus

for optimal utilization of cable systems. The application of discrete or dis-

tributed thermal monitoring devices is a means for safely operating a cable link

within its admissible thermal limits. Based on real time data about thermal

bottle necks (hot spots) or on the complete thermal profile along a cable route

sophisticated dynamic cable rating systems are able to provide information on

admissible loads, thus allowing maximization of transmission capabilities

including overloads. A first approach of this issue has been published in TB 247

“Optimization of power transmission capability of underground cable sys-

tems using thermal monitoring”. Further work in this field will be considered

by WG B1.35 which will explore the rating calculations involved in the

dynamic rating.

The challenge with diagnostics of life cable systems is the acquisition of

accurate data and their subsequent interpretation with regard to practical

conclusions. Whereas small samples of materials (oil, mass) for diagnostic

purposes can be extracted without impact to the system from fluid filled paper

insulated cables or accessories, sampling is not possible for dry extruded

cables.

A report Diagnostic methods for HV paper cables and accessories was

published in ELECTRA 176. For extruded cables, diagnostic procedures

must be absolutely non destructive. One option could be Partial Discharge

(PD) testing on site, which was addressed in TB 182 “PD detection in

installed HV extruded cable systems”. Further work is carried out by WG

B1.28 “On site partial Discharges Detection” with first conclusions expected

in 2011.

Further investigations on water-tree detection in XLPE insulation of

installed cables has been carried out in cooperation with SC D1 “Materials and

new Technologies”. JWG D1/B1.20 will soon publish a report regarding the

applicable methods.

Remaining Life Estimation of existing HV AC Underground Lines is an

important topic, which is of high concern for utilities. It is clear that it won’t be

possible to exactly say how long a cable system has still to live, but to convert

the growing risk of failure or excessive cost of maintenance (repairs) into

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SC B1



an estimation of the remaining useful life will be an important step ahead.WG

B1.09 has produced guidelines for a practical strategy for remaining life esti-

mation.

HV and EHV underground and submarine cable systems are reliable and

well established components of electric power transmission networks. The goal

of SC B1 is to prepare in its field of activity the Network of the Future:

�� The first Technical Direction of SC B1 is to make the best use of this exist-

ing equipment and system by producing guidelines for operation,mainte-

nance and diagnostics, as well as statistics.

�� The second Technical Direction is to ease the development of new tech-

niques bymaking recommendations and guidelines for design, testing and

installation.

�� The third Technical Direction is tomake sure that the Environment is pre-

served.

�� The fourth Technical Direction is to develop Technical Information through

Technical Brochures and Tutorials.

Further work is also submitted by our Target Groups.

At present almost 200 cable experts are participating to this task. Many

high technical value publications (around 170 ) are available. Tutorials sessions

have been organised to disseminate this information in several countries. Any

further information is currently available on SC B1’s website www.cigre-

b1.org. �

S

SC ANNUALREPORT

2010

SC B1


REPORT SC B1 Insulated Cables 2010b1.cigre.org/content/download/61382/2778548/version/1/...Transmission.Itisfocused mainly on HV and EHV applications but MV cable applicationsare also

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