33 kV towerline roadcrossing design modification - Final (English)

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COMISIÓN DE INTEGRACIÓN ENERGÉTICA REGIONAL

OBJECTIVES

Live Line Work is nowadays considered a valuable tool that makes possible to improve the reliability in power systems avoiding production losses associated with power interruptions, in this paper the procedure developed for the redesign of underground road-crossing between 33 kV towers in Wafra Oil Field, Kuwait, through the installation of temporary overhead by-passes working live with rubber gloves method is presented, as clear example of the Live Line Work benefits.

IMCO COMPANY PROFILE

Established in 1970, IMCO is a pioneer company in the industrial Electrical & Instrumentation fields in Kuwait. Today, it is one of the leading engineering and construction companies in the Oil & Gas, Petrochemical, Water & Electricity sectors. IMCO services cover project

management, engineering, design, construction, maintenance and project support services.

Locally some of the main clients and end users are: Kuwait Gulf Oil Company (KGOC), Kuwait National Petroleum Company (KNPC), Petroleum Industries Company (PIC), Saudi Arabian Chevron (SAC), Equate, Ministry of Electricity and Water (MEW), plus many others. Globally, it has proudly collaborated with Bechtel (USA), Technip (Italy), Foster Wheeler (UK), Black & Veatch (USA), GE (USA), Hyundai Engineering Co. (S. Korea), plus many others. IMCO has 15 sites, offices and service centers in Kuwait and branches in Qatar, UAE and Irak. At the present time it has around 3500 employees across Arabian Gulf. It was the first local company to take up Live Line Maintenance and Washing Works in Kuwait and Middle East, and it has capabilities that include:

33 kV TOWERLINE ROAD-CROSSING DESIGN MODIFICATION

Author/s: ENG. PABLO M. JURADO – ENG. JALAL MOHESEN Company: IMCO Engineering & Construction Co.

Position: Senior Live Line Engineer – Project Manager

COMPANY INFORMATION

Address: P.O. Box 9309 Ahmadi, Kuwait Zip Cod: 61004 Telephone: (965) 2398 1661 Fax: (965) 2398 4708 E-Mail: [email protected] [email protected]

KEY-WORDS: redesign - coordination – uninterrupted production – temporary overhead by-pass

COMPANY: IMCO Engineering & Construction Co. COUNTRY: Kuwait Type: Technical Paper Kuwait, April 17th of 2011.

mailto:[email protected]

mailto:[email protected]

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Barehand Method

Distance Method

Rubber Gloves Method

Washing & Cleaning

Working in Distribution and Transmission.

DEVELOPMENT

One of the main Live Line services provided by IMCO, among several others, it is the Operation, Maintenance and Construction of Overhead Lines in Joint Operations (constituted by Kuwait Gulf Oil Company and Saudi Arabian Chevron for the operation of Wafra Oil Field, located in the Partitioned Neutral Zone at the border between Kuwait and Saudi Arabia).

Within the scope of this contract, IMCO maintains 80 km of 11 and 13,8 kV networks, 400 km of 33 and 34,5 kV networks and 36 km of 115 kV transmission lines. Since Live Line Work for maintenance and construction jobs in the oil field was implemented, the level of production losses, which are reflected as differed oil, due to overhead lines failures have dramatically decreased, nevertheless the failures in underground cable terminations kept a high rate, which all the way affected the reliability of the network due to its direct link with the overhead lines because of the type of design of the 33 kV system.

There are in the oil field 8 main circuits en 33 kV, which supplies 68 MW to the oil Wells that are distributed around the field, which layout is made of a main steel tower-line with double circuit, from where the branch lines supported on wooden poles are connected. These branches are the ones that reach to the oil wells to give them supply.

At every intersection between these main tower-lines and the roads used for rig transportation called “rig-roads”, the overhead line is discontinued and there is an underground road-crossing in place, which is made of 3 triple core cables of 240 mm² Cu that were rigidly connected to a busbar at the tower at each side of the road and from these busbar the jumpers to the overhead line were connected.

South Umm Gudair

Wafra

Humma

South Fuwaris

Mina Saud

(SAT Camp)

0 25 50 KM.

ADMINISTRATIVE

DIVISION LINE

S A U D I

A R A B I A

I R A N

I R A Q

S A U D I

A R A B I A

I R A N

I R A Q

S A U D I

A R A B I A

I R A N

I R A Q

SAUDI

ARABIA

KUWAIT

Partitioned Neutral Zone (PNZ)

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This configuration presented some important difficulties like:

Due to the rigid link, a failure in the cables caused the shutdown of the whole line.

Despite there were 3 cables in each road-crossing, the power couldn’t be restored until the failed cable were disconnected from the busbar, which sometimes took several ours due to the occurrence of the failure at unpredicted time (during night time for example).

Re-connection of the cables after repairing or any other maintenance job by means of Live Line Techniques was complicated, because of space limitation and lack of versatility of the structure what hadn’t been designed considering Live Line job.

Application of Off-line diagnostic techniques to determine the healthiness of the underground cables was also complicated.

In the presence of this situation it was decided to implement a redesign and modification of the underground road-crossing that allows:

To avoid the complete shutdown whenever a cable failure happened.

To reduce the downtimes by doing possible the disconnection of the cables through the installation of switches.

To reduce the rate of underground cable failures by allowing performing off-line cable testing to evaluate the condition of the insulation.

To ease the Live Maintenance on the installations.

Droppers

UGC

Rigid link

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New design drawings

Implementation of the project using the Live Line approach

The redesign should be implemented in 9 road-crossings of the 4 main tower-lines, and the challenge was to develop a procedure that allows the modification of the system without power interruption.

The installation of a double overhead by-pass between the towers at each side of the road-crossings that allowed the disconnection of the existing cables, the construction of the structures

of the new design and latter the connection of them to the towers, was planned.

This type of by-pass was done as a regular procedure every time that a hot spot in the connection point of an underground road-crossing should be fixed, but in much lower pole lines with road-crossings shorter than those in the tower-lines. Previously only in one occasion it had been performed in a tower-line, and that experience was used as background to develop the procedure.

Temporary by-pass between poles

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Some important tips to be considered were:

Temporary road interruption and by-pass installed indication. While working on the installation of the temporary span, a diversion for the transit that were properly indicated has to be provided, since these road-crossings were located on heavy traffic main roads of the oil field. In addition, once the by-pass was installed, safe height indicators before and after the road-crossing had to remain installed, as a clear indication that the maximum height for the vehicles in that road had been limited.

Working height, since the upper face in these towers is located to 21,6 m from ground, it was necessary to use 24 m insulated lifts.

Task coordination, as it was decided to employ two Live Line crews each one working in a tower at each side of the road-crossing, under the coordination of one engineer who communicated with the crew supervisors in each tower. Then the supervisors communicated with the linemen that worked at heights by means of walkie-talkies.

Once addressed these issues and defined the Live Line procedure to be used, a general procedure for the execution of the Works in every road-crossing was established, which included the following main stages:

ACTIVITY IN CHARGE OF DURATION

[Days]

Safe Height Indicators installation

IMCO Construction

1

Temporary overhead by-pass installation and removal of droppers

IMCO Live Line 4

Gantries construction according to new design

IMCO Construction

18

Re-installation of droppers and temporary by-pass removal

IMCO Live Line 4

Safe Height Indicators removal

IMCO Construction

1

28

That meant that the maximum height for circulating vehicles was going to be limited during 28 days approximately in each road-crossing, so in order to not affect the rig movements, the main plan for the whole project execution was coordinate with Production Division.

Construction of New Road Crossings in Tower Lines

Execution Schedule

Road Crossing Road 24

/01

/20

10

31

/01

/20

10

07

/02

/20

10

14

/02

/20

10

21

/02

/20

10

28

/02

/20

10

07

/03

/20

10

14

/03

/20

10

21

/03

/20

10

28

/03

/20

10

04

/04

/20

10

11

/04

/20

10

18

/04

/20

10

25

/04

/20

10

02

/05

/20

10

09

/05

/20

10

16

/05

/20

10

23

/05

/20

10

30

/05

/20

10

06

/06

/20

10

13

/06

/20

10

20

/06

/20

10

27

/06

/20

10

04

/07

/20

10

11

/07

/20

10

18

/07

/20

10

25

/07

/20

10

01

/08

/20

10

08

/08

/20

10

15

/08

/20

10

L3A&B/9 & 10 SAC Road 7

L2A&B/8 & 9 L2A&B/8 & 9

L5A&B/9 & 10 SAC Road 7

L1A&B/4 & 5 Road 4

L2A&B/4 & 5 Road 4

L5A&B/22 & 23 SC 13 Road

L5A&B/37 & 38 South Fawares Road 9

L5A&B/59 & 60 SC 14 Road

L2A&B/23 & 24 SC 3 Road

We consider that LL Crews will start installing the following temporary by-pass one week before Construction Crews finish their current job.

Live Line Work

Cold Construction Work

June 10 July 10 August 10Jan 10 February 10 March 10 April 10 May-10

Live Line Procedure for the Installation and Removal of Temporary Overhead By-Pass

Once the Safe Height Indicators are installed, the road transit is interrupted and the circulation is diverted to the previously established alternative way.

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An insulated lift is positioned in each tower at both sides of the underground road-crossing and the necessary hardware and insulators for hanging the conductors of the temporary span are installed.

Starting from the upper phase the conductor for the temporary span is strung, and this operation is repeated in the middle and lower phases.

Then this procedure is repeated for the remaining circuit.

One of the crews installs an insulated jumper between the permanent line conductor and the temporary by-pass conductor and the other crew checks the phase concordance before closing the circuit by installing another insulating jumper. After that, this last crew checks the circulation of current by means of an amp-meter.

This procedure is repeated in both remaining phases, after that the temporary overhead by-pass remains closed and the droppers of the road-crossing can be disconnected.

Insulated jumpers installed to energize the temporary by-pass

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Then the existing jumpers between the main conductor and the droppers are disconnected one by one starting from the lower phase and continuing towards the upper one, in order to allow the removal of the droppers.

Once the underground road-crossing is dead, the droppers are removed.

This operations are repeated in the opposite circuit, after that the overhead by-pass remains carrying out the total current of the lines and the Live Line crews leave the site to the construction team, which is in charge of performing the modification Works according to the new design.

Remodeling Works in charge of construction team

Dropper disconnection

Dropper removal

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Remodeling Works in charge of construction team

Once the remodeling job is concluded, the Live Line crews come back to the site to proceed with the connection of the new installations and removal of temporary by-pass.

With one crew at each side of the tower, the droppers from the tower to the new gantries are installed.

The droppers are connected to the gantries busbar, having previously controlled that all switches are open, and then the droppers are connected to the main line.

Later one of the switches at one side of the road-crossing is closed, and the phase concordance is checked before closing the corresponding switch on the other side. Then the remaining two cables are energized in the same way.

The circulation of current through the main circuit is checked, then the two crews working in coordinated way in each tower, remove the insulated jumpers to each side of the temporary by-pass.

These steps are repeated in the remaining circuit.

Now the conductors of the temporary by-pass can be removed.

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Additional precautions must be taken for the removal of the temporary span because of the existence of the new gantry structures already energized at the bottom of each tower. A rope guided through pulleys is used for this operation and the groundmen work using insulating gloves to minimize the risks of any accidental contact, when lowering the conductors of the temporary span, with the energized equipment.

The conductors of the temporary road-crossing are removed starting from the lower phase and continuing towards the upper one.

Once the task is completed, the Safe Height Indicators are removed and the road is open to the transit again.

Especial Cases

The before described procedure was used in most of the cases, although as previously mentioned, the whole Project included the

remodeling of 9 road-crossings, executed along 9 months time during which different difficulties had to be sorted by adapting the procedure to each especial situation.

Such was the case of the road-crossings of Lines 1 and 2 between towers 4 and 5 (L1/T4&5 – L2/T4&5), where an 11 kV line supported on 10 m poles run parallel to the road over which the temporary span should be strung.

In this case a third insulated lift that was positioned besides the 11 kV line to be crossed was used. This lift was used as additional support to avoid that the conductors of the temporary overhead by-pass being installed would touch the 11 kV line during the stringing.

At the same time, an insulated rope was installed to be used as a messenger for the stringing of the bare conductors of the temporary by-pass to avoid that they fall over the 11 kV line.

Identical procedure was followed for the removal of the temporary by-pass once the construction job was finalized.

Another especial case was found at the road-crossing in Line 2 between towers 4 and 5 (L2/T4&5) where one of the towers of the road-crossing, the number 5, was situated at 90˚ of the road-crossing direction, which prevented to install the temporary by-pass for each circuit parallel to the other as it had been done in the general cases.

Job completed

Job completed

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Then the idea arose of using the conductors of the temporary by-pass installed before for the road-crossing of Line 1 between towers 4 and 5, which run along in parallel way at 10 m distance of Line 2 according to the following drawing:

That is mean in this case, once the job in the adjacent road-crossing was finished, the conductors of the temporary span remained installed and three short conductors were strung between both towers 4 of Lines 1 and 2, and both towers 5 of Lines 1 and 2 to build the by-pass.

RESULTS

The Project was executed during 9 months without any safety incidents, with a efficiency standard and in which some troubles had to be sorted like delays in the execution plan produced by environmental factors, as for instance windy

days or sand storms, which are frequent in the area in the period between April and July during which the Works has to be stopped following the safety recommendations, or like some changes in the rig movement plan that required to expedite the removal of the temporary by-pass.

Once the Project was concluded and the new installations were on service, the reliability of distribution system was substantially increased due to:

A failure in a cable terminal that before caused a shutdown of the whole line, with the new system working, it only affected to the failed cable itself, keeping the two remaining cables the power supply to the main line (L3/T10 cable 3 case).

In another occasion although the short-circuit level produced the complete shutdown of the line, the restoration time was only 45 minutes while before it took an average of 6 hours (L1B/T4 cable 1 case).

A plan for condition monitoring of underground cables by measuring Partial Discharges and doing VLF (Very Low Frequency) tests Off-Line could be implemented.

The application of Live Line Work approach for the execution of this Project, provided the uninterrupted production of 300,000 BOPD, which represented approximately u$s 24 million in losses for the client if they had to shut down the lines for the execution of the Works.

CONCLUSIONS

This technical paper shows a clear sample of how Live Line Work can contribute to avoid important economical losses, keeping at the same time a high safety grade and motivating to the people to work as a team for the development of new procedures.

33 kV towerline roadcrossing design modification - Final (English)

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