Assessment of the Electric and Magnetic Fieldsowikosovo.com/wp-content/uploads/2019/10/Bajgora...transmission line (OHL). Also the assessment will include checks of clearance distances

Assessment of the Electric and Magnetic

Field

110kV Overhead Transmission line Between SS Selac to SS

Vushtri

March / 2019

Tirana, Albania

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REPORT SUMMARY

PROJECT TITLE Social Impact Assessment

DOCUMENT TITLE Assessment of the Electric and Magnetic Field

REV. PURPOSE OF ISSUE REMARK/ DESCRIPTION ORIGINATOR DATE

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2

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FINAL PURPOSE OF ISSUE

CONSULTANT CONTRACTOR

Originator: Checker: Approver: Checked: Approved:

Name/ Last

Name

Ing.

Rejnald Zyfi

Klodian

Cipo

Signature

Date

Document

Status

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Table of Contents

1. Introduction ........................................................................................................................................... 7

1.1. What are the dangers and/or effects that a transmission line may represent? ................................... 7

1.2. Scope of work ........................................................................................................................................ 7

2. Limited norms of EMF in Kosovo and EU .............................................................................................. 9

2.1. Standards or allowed level of EMF in EU............................................................................................... 9

2.2. Standards or allowed level of EMF in Kosovo ....................................................................................... 9

3. Method Statement .............................................................................................................................. 10

4. Electromagnetic Field Check ............................................................................................................... 12

4.1. Electric field check (Plotting of the electric field check) ..................................................................... 12

4.2. Magnetic field check ............................................................................................................................ 13

4.3. Resulting Limit Values ......................................................................................................................... 13

5. Evaluation of overhead line route and the intersections with the proximity objects ........................ 15

5.1. Evaluation of the overhead line and inspections ................................................................................ 15

5.1.1. Distance of the conductor from the existing buildings ........................................................... 15

5.1.2. Check of the overhead line intersections ................................................................................ 15

5.1.3. Check of the line route with the radio transmitting or receiving stations .............................. 15

5.1.4. Horizontal line distances for existing building according to the most unfavorable climatic

conditions 15

5.1.5. Detailed check of the line longitudinal section, for major possible impact to the environment

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5.1.5.1. The span between tower no.77 progressive point of the longitudinal section +17,200m

related to the existing building ................................................................................................................... 17

5.1.5.2. The conductor swing into tower no.50 in the progressive point of the longitudinal section

+11,340m related to the existing building .................................................................................................. 19

5.1.5.3. The span between towers no.32-33 in the progressive point of the longitudinal section

+7,365m related to the existing building .................................................................................................... 19

5.1.5.4. The span between towers no.9-10 in the progressive point of the longitudinal section

+2,274m related to the existing building .................................................................................................... 21

5.1.5.5. The span between towers no.1-2 in the progressive point of the longitudinal section +100m

related to the existing building ................................................................................................................... 21

5.2. Conclusion ........................................................................................................................................... 23

6. General Conclusions & Recommendations ......................................................................................... 24

6.1. Clearances from buildings and other structures of concern ............................................................... 24

6.2. Grounding of the towers no. 9, 10, 11, 12, 32, 33, 76, 77, 78, 79, 80 ................................................. 25

6.3. INSTALLATION OF ANTI CLIMBING DEVICES ........................................................................................ 25

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Figures

Figure 1 Overhead Lines: maximum electric fields ....................................................................................... 9

Figure 2 Power line - profile view mode ..................................................................................................... 11

Figure 3 Electrical parameters ..................................................................................................................... 12

Figure 4 Electric Field VS Offset at Station 14.222m ................................................................................... 13

Figure 5 Magnetic Field plot in the location of the highest calculated magnetic field ............................... 14

Figure 6 Illustration drawing of electrical clearances for 110kV OHL ......................................................... 18

Figure 7 Safety clearance distance - building to tower no.77 ..................................................................... 19

Figure 8 Safety clearance distance - building to tower no.50 ..................................................................... 20

Figure 9 Safety clearance distance – building to tower no.32-33 ............................................................... 21

Figure 11 Safety clearance distance - building to tower no.9-10 ................................................................ 22

Figure 12 Safety clearance distance - building to tower no.1-2 .................................................................. 23

Figure 13 Sampling of tower earthing ......................................................................................................... 26

Tables

Table 1 Exposure to time-varying electric and magnetic fields .................................................................. 15

Table 2 Table of 110kV overhead lines - Del=1.0m ..................................................................................... 17

Photos

Photo 1 Layout of the conductor crossing the animal shed ........................................................................ 19

Photo 2 Layout of the terrain - building to tower no.32-33 ........................................................................ 21

Photo 3 Layout of the conductors .............................................................................................................. 23

Photo 4 Example of wire mesh and steel spins anti climbing device .......................................................... 27

Photo 5 Example of wire mesh and steel spins anti climbing device .......................................................... 27

ABBREVIATIONS

µT Microtesla

A Ampere

ACSR Aluminum Conductor Steel-Reinforced Cable

Amps Ampere

B Magnetic Flux Density

C Coulomb

E Electric Field Strength

EMF Electric And Magnetic Fields

EN European Standards

EU European Union

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GHz Gigahertz

H Henry

H Magnetic Field Strength

Hz Hertz

IEC International Electro-technical Commission

INCRP International Commission On Non‐Ionizing Radiation Protection

J Joule

kg Kilogram

kHz Kilohertz

ATDC Albanian Technical Design Conditions

KV Kilovolt

kV/m Kilovolt per Meter

m Meter

MHz Megahertz

N Newton

N/A Not Available

Nm/A Newton-Meters per Ampere

OHL Overhead Line

OHTL Overhead Transmission Line

PLS-CADD Power Line Systems Transmission Line Design Software

REV Revision

s second

SAR Specific Absorption Rate

Seq Plane-Wave Equivalent

T Tesla (Newton-Meters per Ampere)

TOW Tower

V Volt

V/m Volt per Meter

W/m2 Watt per Square Meter

Wb Weber

Ω Ohm

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1. Introduction

The assessment will be carried out to identify any potential impacts on the health of the residents from the electric and magnetic fields (EMF). Based on recent studies, guidelines and similar cases, the consultant will evaluate the possible health effects from exposure to the electric and magnetic field from the overhead transmission line (OHL).

Also the assessment will include checks of clearance distances from civil buildings, road intersections and all the safety distances on the 110kV Overhead Transmission Line (OHL) must ensure in the nearby area.

The scope of the assessment is also to verify that all the electrical and safety measures have been considered in the power line design, in order for the Overhead Transmission Line to be safe and pose no health risks to local residents during operation.

During the compiled assessment the following items on the transmission line design supplied from the investor have been evaluated:

• Transmission Line route;

• Transmission Line longitudinal Profile;

• Transmission Line tower layouts;

• Conductor Parameters and stringing tables;

• Fittings clamps;

• Earthing of transmission line towers.

1.1. What are the dangers and/or effects that a transmission line may

represent?

The dangers and/or effects that a transmission line may represent are as follows:

• A transmission line under operation generates Electric and Magnetic Fields (these parameters should be kept within the allowed limits, in order not to present any danger to the general public through exposure);

• Transmission lines may present electric shock risks (for this reason conductors and all elements under live-line are kept within the allowed parameters);

• Additional protection measures in different areas of the line;

• Electrical shock hazards must be kept within tolerable limits of allowed step and touch voltage.

1.2. Scope of work

This consultant’s study will be based on the classification of potential electro-magnetic-field exposure from the designed OHL, which is subject of construction based on the power line voltage, current transmitting capability, power frequency, towers topology and their distance to nearby residences or inhabited areas).

Having these parameters defined, the consultant is able to predict the EMF exposure levels and determine any area of concern where the urban settlements lie within the potential human impact zone.

Given the characteristics of the transmission line (110kV OHTL) for the connection of Substation WF Selac to the Substation Vushtri, and based on the literature and recent studies of similar cases (as presented in the chart given below1) the area of influence is determined to be up to 25m from the current transmission line.

1http://www.emfs.info/sources/overhead/summaries/

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Figure 1 Overhead Lines: maximum electric fields

A walk through survey was carried out to identify on site the presence and characterization of the receptors (settlements, schools or other education facilities, hospitals, telecommunication antennas, transmitters or receivers, roads, other transmission lines, etc., located within or close to the OHL corridor).

The Consultant will compare the calculated parameters in line with the EU Directives, if there are specification of the potential human impact zone relative to EMF for 110KV transmission lines and all standards and recommended exposure limits are taken in consideration.

If EMF levels are confirmed or expected to be above the recommended exposure limits, the application of engineering techniques should be considered to reduce the EMF produced by the designed power line.

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2. Limited norms of EMF in Kosovo and EU

2.1. Standards or allowed level of EMF in EU

The electric and Magnetic field allowed levels in the EU have been considered related to studies on both direct and indirect effects of EMF to the human body.

These studies have been performed by the "International Commission on Non‐Ionizing Radiation Protection" ('INCRP'), and based on the performed studies have been published the “ICNIRP Guidelines For Limiting Exposure To Time-Varying Electric, Magnetic and Electromagnetic Fields (up to 300GHZ)”.2

The above guideline has defined the "Reference levels for general public exposure to time-varying electric and magnetic fields".

The above reference levels for general public exposure have been defined based on the SAR (Specific energy absorption rate W x Kg ¹־. The rate at which energy is absorbed in body tissues, is in watt per kilogram.

2.2. Standards or allowed level of EMF in Kosovo

No parameters of EMF limits have been found in the legislation of Kosovo for this study, so the same reference levels as in the EU will be applied.

2 https://www.icnirp.org/cms/upload/publications/ICNIRPemfgdl.pdf

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3. Method Statement

The applied Method Statement to check the electric and magnetic fields caused by the operation of the designed 110kV overhead transmission line, is performed by importing the OHL as designed in PLS-CADD software3, taking in consideration the actual terrain and by placing the towers according to the longitudinal profile. Also the conductor sagging in the prepared model has been installed according to the design sagging tables for each span in order to achieve the most realistic transmission line model according to the final as-build situation.

At the end in the conductor section module has been selected the "EMF Calculator Function" considering that the electrical field is proportional to the Voltage level for the simulation and has been selected the highest voltage level of 123kV for the allowed working voltage of the equipment according to IEC 60070-1 standard.

The maximal allowed current level for the ACSR 240/40 Conductor is 645 Amperes according to the guaranteed characteristics of the EN 50-182 standard for a maximal operation temperature of 60°C.

In order to make a more conservative calculation the consultant has considered a maximal full load current of 717Amps (according to the datasheet from the conductor manufacturer (even though it is too high for the power capability of the wind farm).

Considering the highest temperature values, it is expected that during operation, the conductor will never reach or be allowed to reach this temperature.

INPUT PARAMETERS:

✓ U=123 kV

✓ I = 717 Amps

Figure 2 Power line - profile view mode

The designed power line (figure 2) is modelled in PLS Cadd software in the profile view mode. It shows

the longitudinal profile line which is checked for the electric and magnetic field values. This control is

obtained by entirely digitalizing the line route according to the original design.

3 http://www.powline.com/products/pls_cadd.html

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Figure 3 Electrical parameters

The electrical parameters used for the calculations in the magnetic and electric field are:

✓ Voltage level of 123kV; and

✓ Load current of 717Amperes.

In the above figure is shown the data input used in the performed electric and magnetic field calculation.

Also the limit values are inserted in the “field limits” boxes for which the software will perform the

calculations.

Note:

• Maximal Current of 717A taken from page no.50 of main design No ES06-01/2019 (conductor

data from manufacturer);

• Maximal operating voltage 123kV according to standard insulation levels from IEC 60071-1.

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4. Electromagnetic Field Check

The electromagnetic field check is performed in specified points of the transmission line and it varies according to the conductor height and distances for the surveyed point.

Observing the longitudinal profile of the OHL, the clearance distance of the conductor from the ground is near its critical point of 6m. In these points we expect to have the higher values of electric and magnetic fields from ground. Several calculations have been performed in the spans with critical lowest points of the conductor from the ground level.

Each span has been checked on the electric and magnetic field and the locations with the highest electric and magnetic fields according to the sectional view of the longitudinal profile have been determined.

4.1. Electric field check (Plotting of the electric field check)

As seen from the plotted graph (figure 4), the electric field is higher on the side where the two cross arms of the transmission line are located. With the green color are shown the positions of the conductors in normal conditions (no wind effect).

Figure 4 Electric Field VS Offset at Station 14.222m

✓ Maximum Calculated value of electric field: E = 1.471kV/m; ✓ Maximum allowed value of electric field for public exposure: E = 5.0kV/m.

Conclusion: Calculated value of electric field is within the allowed limits.

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4.2. Magnetic field check

As expected in the plotted graph a higher electric field is visible near the lowest conductor point in the side were two conductors are located.

Figure 5 Magnetic Field plot in the location of the highest calculated magnetic field

✓ Maximum Calculated value of magnetic field: B = 11.26(µT);

✓ Maximum allowed value of magnetic field for public exposure4: B = 200.0(µT).

Conclusion: Calculated value of magnetic field is within the allowed limits.

4.3. Resulting Limit Values

The reference levels for general public exposure to time-varying electric and magnetic fields (unperturbed rms values) are shown in the table below. The maximal allowed values for:

✓ Maximum Allowed electric field strength E= 250/f (kHz) = 250/0.05 = 5000 V/m

✓ Maximum Allowed magnetic field strength B= 5/f (kHz) = 5/0.05 = 200 µT

4 ICNIRP GUIDELINES: Table 7. Reference levels for general public exposure to time-varying electric and magnetic fields (unperturbed rms values)

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Table 1 Exposure to time-varying electric and magnetic fields

Frequency

range

E-field strength

(V/m)

H-field strength

(A/m) B-field (µT)

Equivalent plane wave power

density

Seq (W/m2)

0-1 Hz - 3.2 x 104 4 x 104 N/A

1-8 Hz 10,000 3.2 x 104/f2 4 x 104/f2 N/A -

8-25 Hz 10,000 4,000/f 5,000/f N/A -

0.025-

0.8KHz 250/f 4/f 5/f N/A -

0.8-3kHz 250/f 5 6.25 N/A -

3-150kHz 87 5 6.25 N/A -

0.15-1MHz 87 0.73/f 0.92/f N/A -

1-10MHz 87/f/1/2 0.73/f 0.92/f N/A -

10-

400MHz 28 0.073 0.092 2

400-

2000MHz 1.375 f1/2 0.0037f1/2 0.0046f1/2 f/200

2-500GHz 61 0.20 0.20 10

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5. Evaluation of overhead line route and the intersections

with the proximity objects

5.1. Evaluation of the overhead line and inspections

For the evaluation of the overhead line route and the intersections with the proximity objects the following verification will be made:

• Distance of the conductor from the existing buildings;

• Check of the overhead line intersections;

• Check of the line route with the radio transmitting or receiving stations;

• Horizontal line distances for existing building according to the most unfavorable climatic

conditions; and

• Detailed check of the line longitudinal section, for major possible impact to the environment.

5.1.1. Distance of the conductor from the existing buildings

To define the distance of the conductor from the existing buildings for the maximal conductor inclination for the most unfavorable climatic condition. The Method of the line route evaluation will be applied by observing carefully segments in the line route that pass over polluted areas, by preventing to the conductor from coming near the allowable limits for the highest conductor swing in the heaviest climatic criteria.

5.1.2. Check of the overhead line intersections

During the assessment it was noticed that there are 3 towers where the tower legs are located at a close distance from the road banks. This distance is greater than the minimum allowed 2.5 m but some protection, through paint by florescent color, should be built near the tower legs, to protect them from car accidents which may result into transmission line tower destruction.

Attention should be given to towers no.77, 50, span between towers no.32-33, towers no.9-10 and span

between towers no.1-2. The check of the overhead line intersections can be completed with:

• Objects build underneath the line axis;

• Intersections with roads and conductor height from road intersection;

• Distance of tower legs from road banks;

• Vertical distances with existing overhead lines and telephone lines.

5.1.3. Check of the line route with the radio transmitting or receiving stations

For the check of the above electrical clearances will be respected the normative and criteria's According to the EN 50-341 European standard.

5.1.4. Horizontal line distances for existing building according to the most

unfavorable climatic conditions

The table below gives instructions of clearance distances for every type of terrain and situation that the overhead line crosses. Means that for 110kV OHL, the minimal allowed distance of an object at a live voltage from another object at earthed potential is 1.0m.

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Table 2 Table of 110kV overhead lines - Del=1.0m

The photo below (see also page 18), is used in addition with figure No.6, to estimate data of clearances to

crossed objects under the line route or clearance distances of objects near the line proximity.

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Figure 6 Illustration drawing of electrical clearances for 110kV OHL

Referring to the result obtained from the table no.2, the conclusion is that the horizontal electrical distances of the most external conductor for his maximal inclination angle to the building walls, should not be less than 4m.

Carefully observing the line layout and the longitudinal profile, sections of major concern are as follows:

• The span between towers no.77 in the progressive point of the longitudinal section +17,200m

regarding to the existing building;

• The conductor swing into tower no.50 in the progressive point of the longitudinal section

+11,340m regarding to the existing building;

• The span between towers no.32-33 in the progressive point of the longitudinal section +7,365m


• The span between towers no.9-10 in the progressive point of the longitudinal section +2,274m


• The span between towers no.1-2 in the progressive point of the longitudinal section +100m

regarding to the existing building.

The assessment will be made for the maximal sag of the conductor with the maximum wind pressure acting perpendicular to the conductor. Inclination swing of the insulators and of the conductor will be calculated using the created PLS-CADD model of the overhead line.

5.1.5. Detailed check of the line longitudinal section, for major possible impact

to the environment

5.1.5.1. The span between tower no.77 progressive point of the longitudinal

section +17,200m related to the existing building

The tower no.77 has been moved from the animals store compared to the positioning in the previous design. With this movement of the line, away from the animals’ store, there is no risk of a fallen broken conductor over animal’s store. But structure no.77 has been placed closer to the building, only 10.2m from the conductor phase.

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Photo 1 Layout of the conductor crossing the animal shed

For this reason a more detailed check was performed in the following paragraph and the result is that, there are no risks for the building from electrical hazards and does not have electric or magnetic fields over the allowed limits.

In the figure below, it is shown the control for clearance distances of the building from the conductors’ maximal inclination.

Figure 7 Safety clearance distance - building to tower no.77

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The building is not under risk even for the most severe climatic condition of the wind blowing

perpendicular to the line axis.

5.1.5.2. The conductor swing into tower no.50 in the progressive point of the

longitudinal section +11,340m related to the existing building

As seen from the figure below, the tower no.50 does not represent a risk in electrical clearances from the building, because the conductor sag is very small near the tower and the insulators do not allow a significant conductor swing.

The transmission tower and the overhead line conductor do not present a risk for the civil building adjacent to the tower. The figure 8 shows the Check of conductor safety clearance distance from nearest building in from tower no.50.

Figure 8 Safety clearance distance - building to tower no.50

5.1.5.3. The span between towers no.32-33 in the progressive point of the


As seen in the figure below the overhead line conductor is very far from the building and because there is a small span and a low sag between towers no.32 to tower no.33, the safety distance of the conductor electrical clearance distance, to the civil building are reached and the transmission line does not represent a potential risk or hazard to the civil building.

The figure 9 shows the check of conductor safety clearance distance from nearest building in span between towers no.32-33.

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Figure 9 Safety clearance distance – building to tower no.32-33

Photo 2 Layout of the terrain - building to tower no.32-33

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The figure below shows the Check of conductor safety clearance distance from nearest building in span between tower no.9-10.

Figure 10 Safety clearance distance - building to tower no.9-10

The clearance distance from the mid-span conductor sag to the highest possible conductor inclination has the necessary safety distance from the civil building. Therefore, for this span even though the distance is small and there is not a lot of spare safety distance, the building is safe against the conductor swing during the most severe wind conditions. Actually the building is not threatened from electrical hazards but the gap is near the limits, considering also that the building is a residential house.


longitudinal section +100m related to the existing building

The sectional view of the conductor swing between tower No. 1 and tower No.2 shows that for the maximal wind pressure without ice conditions, there will be conductor swinging over the building (in the layout or structure named "Llamkos Glavasteel") observed in the span layout.

In the scenario of the load combination with maximum transversal wind without ice load, the conductor will be for certain over the roof of the building. During this load case the conductor also suffers the maximal mechanical stress. This means that in case of a broken conductor for this load combination the conductor could fall over the top of the building or implant. The figure below shows the Check of conductor safety clearance distance from nearest building in span between tower no.1-2.

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Figure 11 Safety clearance distance - building to tower no.1-2

Photo 3 Layout of the conductors

This photo shows the layout of the conductors in the span between tower no.1 and tower no.2. As seen in the photo the left conductor is only 4.2 meters from the edge of the building in mid-span, where we have the point of higher sag in the span.

A shift in the position of tower no.2 is proposed in order to position the conductors away from this part of

the building, so that even in the case of trasversal wind blowing at 90 degrees with the conductors, the

building should not be afected from conductor breackage at maximal wind pressure.

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5.2. Conclusion

The Transmission line does not seem to affect or exceed the minimal allowed safety distances from the civil buildings and other structures. Overall, the impacted areas have the necessary clearance distances

from buildings and are within the allowed limits and ICNIRP GUIDELINES: Table 7 of "Limiting exposure to

time‐varying electric, magnetic and electromagnetic fields”.

The position of tower no.2 is recommended to be shifted in order to position the conductors in a greater distance from the building as shown in the photo no.3.

From the assessment, it has been verified, that the conductor swing for the most extreme wind conditions will be over the highlighted area.

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6. General Conclusions & Recommendations

As reflected in the above calculations, the highest electric and magnetic fields are far from the maximal allowable limits, respectively of 5.0 kv/m for the electric field and 200.0 (µT) for the magnetic field, for the general public exposure according to the ICNIRP guidelines: "Limiting exposure to time‐varying electric, magnetic and electromagnetic fields: Up to 300 GHZ)" (Published in Health Physics 74 (4):494‐522; 1998).

Reference levels for general public exposure to time-varying electric and magnetic fields (unperturbed rms values) are as follows:

✓ Allowed electric field strength E= 250/f (kHz) = 250/0.05 = 5000 V/m

✓ Allowed magnetic field strength B= 5/f (kHz) = 5/0.05 = 200 µT

6.1. Clearances from buildings and other structures of concern

The clearances from Buildings and other structures have been kept in the allowable line clearance limits. The line with the highest electric and magnetic field recorded is the span between towers No.63-64 in the progressive point of the longitudinal section 14,222m.

Also other points where the Electric field will be in the values over 1kV/m are the spans as follows:

• between tower no.69-70 in the progressive point of the longitudinal section 15,451m;



• between tower no.89-90 in the progressive point of the longitudinal section 19,204m.

All the above spans, after the detailed check, showed that they do not represent a hazard from the electrical shock or neither have electric or magnetic fields above the allowed limits. Meanwhile for the span between towers no.1-2 has been advised the shifting, if possible, of the tower no.2.

In this part of the line route has been kept a configuration with many angle towers which have been chosen with the shortest possible configuration, resulting in a conductor height being very close to the ground.

In case it is chosen to decrease the electric and magnetic field to a minor value, it may be suggested to adapt a body extension of +1.0m of the chosen towers no.69, 70, 71, 86, 87, 89, and 90.

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6.2. Grounding of the towers no. 9, 10, 11, 12, 32, 33, 76, 77, 78, 79, 80

The earthing of towers no.9, 10, 11, 12, 32, 33, 76, 77, 78, 79, and 80 should be extended to another type of grounding with a wider configuration than type B which should include underground earthing strips or additional electrodes.

Figure 12 Sampling of tower earthing

This is required because the towers are close to inhabited areas and because the earthing conditions depend on the insulation conditions of the population being exposed to high voltages. Near the towers no. 9, 10, 11, 12, 32, 33, 76, 77, 78, 79, 80 should be considered as an area where people might gather with bare feet meaning a maximal body resistance of 1,750ohm.

This should require a specially designed earthing and calculation of this earthing for the touch and step voltages should be provided. Also, the soil resistivity in this part should be evidenced in the geological study and inserted as an input parameter in the earthing design for these towers.

6.3. INSTALLATION OF ANTI CLIMBING DEVICES

From a general observation of the main design and all the tower passports and tower drawings, it is visible that no anti climbing devices have been foreseen to be installed in any of the transmission line towers. All towers should be equipped with ant climbing devices.

The anti-climbing device prevents children, unskilled personnel or animals, from climbing on transmission line towers. The workshop drawings of the transmission line tower structures should be adapted by drilling additional holes in order to allow for the installation of anti-climbing devices.

These anti climbing devices can be composed of wire mesh or steel spins as shown in the photos as follows:

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Photo 4 Example of wire mesh and steel spins anti climbing device

Photo 5 Example of wire mesh and steel spins anti climbing device

Assessment of the Electric and Magnetic Fieldsowikosovo.com/wp-content/uploads/2019/10/Bajgora...transmission line (OHL). Also the assessment will include checks of clearance distances

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