icolim conductive clothingmsz en 1585:2012 operation of electrical installation based on en...

Revision of the way of classification of conductive clothing

Budapest University of Technology and EconomicsHigh Voltage Laboratory

Dr. Gábor Göcsei, Dr. Bálint Németh

Department of Electric Power EngineeringGroup of High Voltage Technology and [email protected]@vet.bme.hu+36 1 463 3236

Conductive clothing

• Conductive clothing

• Faraday-cage

• „Faraday-holes”

• HV LLM

• Electric field

• Magnetic field

• Face mesh

BUTE High Voltage Laboratory5/11/2017 2

Limits for electric field strength

• Measuring and simulating the electric field between the face screen and the face of the mannequin• According to ICNIRP the maximum allowed electric field

near an occupational person is 10 kV/m


Electic field

strength, until2010 [kV/m]

Electric fieldstrength,

since 2010[kV/m]

Magnetic field

strength, until 2010 [µT]

Magneticfield

strength, since 2010

[µT]

Public 5 5 100 200

Occupational(8 hours/day)

10 10 500 1000

Electric field distribution

• Calculations

• Modeling

• CAD (3D)

• Simulations

• Finite element method (FEM)

• Face mesh model

• Laboratory measurements

• Checking the results


Face mesh opening vs. electric field strength

5/11/2017 BUTE High Voltage Laboratory 5

• Limit: 10 kV/m• Face mesh

• Shielding of electric fields

• Ergonomicalaspects

• Local peaks of E-field• Eliminated by the

current way of measurement

• „Faraday-holes” decrease efficiencysignifficanty

• Safety of theworker can be guaranteed onlyby theapplication of face protection

Critical value:

1.75 cm

Note: 1.75 cm ~ 0,7”

Summary of simulations and measurements

• Electric field may be higher than the limit of

10 kV/m without any face mesh

• Electric field can be radically reduced with a

proper face mesh

• The maximum allowable radius of mesh

opening is about 1.75 cm (~0,7”)

• By IEC 60895, the face screen is currently

only required over 800 kV (Class 2)


Summary of the results

BUTE High Voltage Laboratory

• Results: face screen decreases the level of electric field inside the conductive clothing significantly as a „shield” in front of the face

• At common European voltage levels (even at 120 kV) without face protection there are specific parts on the worker’s head where the electric field is higher than the current limits defined by ICNIRP

5/11/2017 7

Summary of the results


• Face protection decreases electric fieldstrength below the limit

• Face protection is essential during live line maintenance to protect the worker from high electric fields

• Different types of conductive head covers, scarves and helmets• Scarf, helmet: shielding efficiency is weak

5/11/2017 8

Measuring the screening efficiency

• Regulation of the IEC 60895• Two currents are to be measured

• I1 flowing between the live electrode and theconductive clothing connected to the mannequin

• I2 flowing between the live electrode and themannequin


Measuring method

• Acceptance criteria


Measurement according to IEC

• Another, but equivalent

arrangement

• Mannequin suspended by a solid

insulator

• Measuring voltage: 111.5 kV

• Distance (determined by the

voltage level): 1.12 m


Results

• Screening efficiency with face mesh

• Screening efficiency without face mesh

• There is not any notable difference

• The clothing without face mesh passed the test


I1 [uA] I2 [uA] V [%]

1412 13 99.08

I1 [uA] I2 [uA] V [%]

1445 14 99.04

Problems

• The environment of the measurement is not defined at all

High influence on the electric field distributionduring the measurement!


Simulation and results


• No grounded parts near the mannequin• Conductor shields the electric field

• Electric field is low in front of the face



Figure 1 Figure 2

Figure 1: there are not any grounded parts near the mannequinFigure 2: there are grounded parts, but further than distance „D”

Conclusion of the simulations

• The electric field strength is much higher and

the distribution is completely different in the

two cases

• The measurement can not beenrepeatable, because the environment has a high infuence on the electric field distribution!


Suggestions

• The electrode arrangement shall be clearly determined

• The micro ammeters are energized, it is not easy and safe to read the values

Suggestion for a new arrangement(currently under CDV version by IEC,

just started the IEEE 1067 revision)


New measurement arrangement

• The mannequin is grounded

• The energized conductor shall be placed at the minimal arcing distance from the mannequin (determined by the current relatedstandards)

• The conductor shall be placed at the head’s height

• Leakage current shall be measured by two micro ammeters


New measurement arrangement

• Acceptance criteria

The screening efficiency (V) shall be higher than 99%

Where:��


Measuring in the new arrangement


Measuring in the new arrangement

• Screening efficiency without face mesh

• Screening efficiency with face mesh


I body [uA] I clothing [uA] V [%]

6,6 350 98,12

I body [uA] I clothing [uA] V [%]

0,5 360 99,86

Simulations in the new arrangement• Electric field with (left) and without (right) grounded

parts nearby


Conclusion

• The environment does not affect the

suggested measurement’s results signifficantly

• The measurement will be repeatable

• The differences are much more clear between

the different types of clothing

• The micro ammeters can be read easily in a

safe way (as they are grounded)


Further studies…


Accident – High voltageFlashover during LLM – 500 kV AC

• Canada

• 27th October 1997. – autumn11:26 – 0,5 °C-1,3 °C

• Hot stick method

• Insulator changing

• 5,6 kA peak current

• ~ 50 ms arcing time

26

Photos: W. McDermid, J. Bromley, D. Dodds, D. Swatek és M. Hydro,

„Investigation of the Flashover of a FRP Hot Stich While in Use for Live Line

Work at 500 kV,” in IEEE, 1999.


Regulations for arc protection and IEC standard about conductive clothingMSZ EN 1585:2012 Operation of electrical installation

Based on

EN 50110-1:2004 Operation of electrical installation

with additional national regulations

• Less deatiled specifications and requirements compared to anothernational requirements (such as NFPA 70E in the USA)

• There are no guidlines about risk assessment or incident energy

IEC 60895:2002 Live working. Conductive clothing for use at nominal voltage up to 800 kV a.c. and ±600 kV d.c.

27BUTE High Voltage Laboratory

28

Case I. – 750 kV grid - arrangementFlashover on the surface of the additional insulator rod between the two insulator strings


• Arc rated conductive clothing needed

• ATPV level - 8.77 cal/cm2

29

Case I. – 750 kV gridFlashover on the surface of the additional insulator rod between the two insulator strings

2.524 cal/cm2

Case II.Installation of a PPAG to 400 kV transmission line

Incident energy can exceeds 2 cal/cm2

BUTE High Voltage Laboratory 29


BUTE-HVLHungary, Budapest1111, Egry József u. 18.Phone: +36 1 463 3236Fax: +36 1 463 3231E-mail: [email protected]

Thank youfor your attention!

icolim conductive clothingmsz en 1585:2012 operation of electrical installation based on en...

Documents