live rehabilitation of 400kv ohl mintia-sibiu - icolim 2014icolim2014.org/2014/ppt/159.pdf · 3...

Live Rehabilitation of 400kV OHL

Mintia-Sibiu

Eng. Marius Nicolae Oltean- Smart SA- RomaniaEng. Ioan Sevastre- Smart SA- RomaniaEng. Dorin Lucian Brabete- Smart SA- RomaniaEng. Ioan Rodean- Transelectrica- Romania

1

2Live Rehabilitation of 400kV OHL Mintia-Sibiu

1. INTRODUCTION

Connected to Mintia power plant and to 400/220/110/20kV Sibiu Sudsubstation (which is the center of gravity of Romanian Transmission Grid)Mintia – Sibiu 400kV OHL is one of the most important transmission line in Romania.

After the repairing works, the main advantages will be :

- reducing the number of occurring incidents;

- preventing the destruction of the OHL components, which would

have real serious consequences on the functioning of the energetic system;

- preventing/reducing the economic and social costs implied by the

interruption of the electric energy;

- reducing maintanance works and costs;

- increasing the operation safety of the Transmission Power Grid.


Mintia- Sibiu 400 kV OHL:

-Operating since 1972(operating voltage 220kV-in 1987 operating voltage becomes 400kV)

-rated voltage: 400 kV;

- OHL type: simple

circuit;

- length: 127,749 km;

2. THE PROJECT STARTING POINT


Main technical data


Towers


- conductors- phase conductors: 1 circuit x 3 phases/circuit x 2 conductors/phase x 450/75 mm2 ACSS, lay length: 400mm.- ACSS 160/95 mm2 ground wire and one OPGW 95 or 70 mm2.- vibration dampers:

- AVb 1 and Avb 3 - for the classical ground wire;- SAPREM Stockbridge Damper –for OPGW;- AVb5- for the ACSS 450/75 phase conductor.

- Insulation- insulator strings consisting of cap and pin elements made of chilled glass

- CTS 120-1 or CTS 160-1, PS11 or PS16B for the level I and II pollution area;- CTS 120-2p for the level III and IV pollution area;;


- Clamps for active conductors:- SOL 450 pivot suspension clamps with no releasing of the conductor- STIL 450 limited tension suspension clamps;- CSA-4 suspension clamps ;- TP pressure traction strain clamps;- TPDf 450/75 pressure traction with front derivation plate strain clamps;

- Clamps for ACSS ground wires:- SOL 70 and SOL 240 suspension clamps;- TPT 70 and TP1 strain clamps;

- Clamps for OPGW:- AGS Clamp n70 and 95 suspension clamps ;- Dead-End CFO-70 and CFO-95 tension clamps


Grounding electrodes

- artificial earthings, made of flat-bar zincates steel (OlZn 40x4 mm) mounted 0,40 - 0,90 m deep in the ground, and, in some cases, of vertical electrodes made of zincates steel pipe.

Tower foundations

- prefabricated foundations for the stayed support suspension towers, and guss concrete foundations for the tension towers.

Anticorrosion protection

- painting, for the metallic poles;

- hot zinc coating, for the steel cores of the ACSS conductors, for the clamps and fittings of the insulator strings and ground wire;

- zinc coating for the electrodes and flat-bars of the grounding electrodes

- electrolytic zinc coating for the assembly components of the insulator strings (screws, splints)


Location of the OHL


3. CHOOSING LW TECHNOLOGIES FOR THE PROJECT

Being difficult to deenergize the line Live Working technologies are mandatory for project completition.

In the feasibility study a comparison between working live and working with the line deenergized was done.


Advantages of LW

From technological point of view LW has certain advantages:

-the works can be done as they were planned;

-due to increasing of the maneuvers , the incident risk is diminished;

-the procedures for organizing and performing work are more simple;

- there is no undelivered energy and there are no congestions;

- the stability of the grid is increased;

- the safety at work is increasing.


4. Work description

The main works done on the line in LW technology:

-mounting or replacement of aerial numbering plates,

- replacement of vibration dampers on the active conductors and on the groundwire,

- mounting or replacement of suspension clamps, with or without armour rod,

- replacement of broken pin-cap insulators,

- replacement of PS 11 insulator chains with composite insulators,

- replacement of arching devices,

- replacement of insulator string straps on the crossarm,

- replacement of dampers.


Some other works were done with the energized line, but not in LW technology:

- Works on the tower foundation;

- Works on the maintenance transmission line corridor,

- Works on groundings,

- Works on metal structure of the towers,

- Installation of new numbering plates,

- Installation of warning plates,

- Installation of ladder devices on Y towers;

- Lining of suspension PAS towers.


Some works where performed with the line deenergized:

- Replacement of anchor system;

- Painting of the towers;

- Replacement of existing TP and TPD clamps with new TPDFc

clamps.


5. Live technologies applied on the line

General Circumstances

The methods applied are:

-“close to the energized parts”

-“barehand”


3.2. Distances

The distance D is the sum between the voltage distance (dt) and the protection distance (dp).

Rated voltageUn (kV)

Voltage distance dt (m)

Protection distance dp

(m)

Minimum distance phase/operator D

(m)

400 2 0,50 2,50


Wheather Conditions

The LW foreman has to analyze the weather conditions.

It is forbidden to start the work in the following weather conditions:

- Showers (rain, snow, drizzle, hail,) or relative humidity higher

than 80%,

- Thick fog,

- Strong wind (over 9.5 m/s),

- Lightning (storm) in the working area..


Special exploitation regime (SER):

- the autoreclosing should be cancelled at both sides of the line,

- radio or telephone links have to be established between the working area and operative dispatch centre,

- the reclosing of the OHL should be done manually, only when the LW foreman agrees.


Work Preparation

The foreman identifies the OHL and the tower and the access conditions to the area. He checks weather conditions. He ensures that every crew member is well instructed and understood these instructions.The foreman verifies that the work preparation is appropriate. He also verifies that the situation of the action place as he expected and there are no new elements that may affect the working progress.The foreman verifies the working zone, especially:

- Vegetation; - The distances to the closest buildings, - Presence of other elements that may come into contact with the OHL;- The state of the insulating chains

The crew members that will work on the tower are supposed to wear the electro conductive suits, anti-UV glasses, electro conductive boots, protective helmet, climbing system, the little roll and insulating rope.


Risk Analysis and Prevention Measures

The foreman has all the needed documents for the access in the working zone, on the OHL.The foreman owns the Live Working technical Instruction and the Specific Safety Instructions for the Work. The foreman defines the Live Working Zone to prohibit unauthorized access.The foreman shall ensure that there are access conditions to the Live Working area, which are adapted to the devices that he intends to use on the ground.All along the working period, the foreman has to supervise the working team and the working area.


Access on the Potential

Depending on the work conditions different tools and devices where used to reach the potential:

- Aerial insulated platform;

- Insulated ladder (from the tower structure);

- Insulated ergonomic chair (from the tower structure);

- Aluminum ladder (from the ground);

- Ropes and booms (from the ground).


Aerial Insulated Platform

The insulated aerial platform is an articulating aerial device having an insulating lower arm, insulating upper boom and an ISO-Grip system. -Lower Boom is made of reinforced steel with a rectangular filament wound fiberglass insulator (762 mm). -Upper Boom is a rectangular filament wound fiberglass, providing a minimum of 4.6 m of isolation. The inner surface of the fiberglass insulator of the booms has acrylic polyurethane The outer surface has a smooth gel coat finish.


Compensating upper boom allows the upper boom to maintain the same relative angle with the ground as the lower boom is being raised or lowered.

The mechanism for leveling the platform includes two single acting cylinders incorporating counterbalance load holding valves to lock the platform in the event of hydraulic line failure. Hydraulic flow for the cylinders is controlled by a pendulum type control valve that maintains a level platform throughout the full range of boom articulation.

The aerial device is designed and manufactured in a facility that is certified to meet ISO 9001 requirements.


Replacement of suspension clamps and installation of vibration dampers on suspension towers

For the 400 kV suspension towers with crossed anchors the execution of the works in the middle phase will be done after measuring distances.

The minimum number of staff required for this work is:

-one LW foreman (team leader), authorized I 3T,

-one LW operator, authorized I 1T, on the tower,

-two (2) LW operators, authorized I 1T, on the conductor.

-five (5) LW operators, authorized I 1T or without LW authorization.


Replacement of the vibration dampers on the ground wire

The minimum number of staff required for this work:


-two (2) LW operators, authorized I 1T, on the tower.

- two (2) LW operators, authorized

I 1T or without LW authorization.

- It is not necessary to put the line

into a Special exploitation regime

(SER).


Replacement of the aerial numbering plates

The method applied is “close to the energized parts” (the operator finds himself at pole’s potential, at a proper distance from the energised parts).

The minimum number of staff required for this work:


-one LW operators, authorized I 1T, on the tower.

-one LW operators, authorized I 1T or without LW authorization.

It is not necessary to put the line into a Special

exploitation regime (RSE).


Economical considerations about LW technologies applied in the project

The advantages of the Live technologies where underlined:- Possibility of performing the works as they where planned;- Decreasing of maneuvers number, involving in consequence the decreasing the number of outages;- Simplified procedures concerning organization, preparation and execution of works;- Limitation of environmental impact;- Increasing the continuity of supply;- Increasing of work safety.


After every Live Working project, Transelectrica is analyzing the efficiency of working Live. Some criteria are considered. Basically the losses (technological consumption) and congestion costs are easy to calculate.

For Mintia-Sibiu Sud refurbishment project, considering losses and congestions, the economy done by applying Live Working technology was about 50.000 EUR for the first area.

The final economy will be calculated at the end of the project. The expected economy using LW technologies is about 200.000 EUR for the whole project.


There are other criteria which are more difficult to quantify, such as:

- The time of line unavailability;

- The unload of adjacent networks, which are supplementary loaded, due to the line deenergizing;

- The maneuver costs;

where not quantified as savings, but where shown as benefits of the project.

Anyway the main benefit is the stability of power grid.


Working live on the overhead lines is a need in the actual state of the Romanian Power Grid.

When the LW technologies are applied the project should be studied and the best approach should be used.

Depending on natural conditions the acces methods can be combined. In this particular project different acces methods were used (aerial insulated platform, insulated ladder, aluminum ladder, ergonomic chair).

The combination between live maintenance technologies and the usual technologies, with the line deenergized, is sometimes, the best way to optimize the costs and efficiency of projects.

CONCLUSIONS

THANK YOU FOR YOUR ATTENTION !

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live rehabilitation of 400kv ohl mintia-sibiu - icolim 2014icolim2014.org/2014/ppt/159.pdf · 3...

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