## Permissable touch voltage - derivaton of curves in EN 50522

## Permissable touch voltage - derivaton of curves in EN 50522

(OP)

Hi

Referring to thread238-305712: Calculation of Touch and Step Voltage Limits using EN50522.

Im trying to derive the permissable touch voltage curves in standard EN50522 without any success.

Can someone please share how to derive these curves? An ExCeL worksheet will be appreciated:)

Many Thanks

Referring to thread238-305712: Calculation of Touch and Step Voltage Limits using EN50522.

Im trying to derive the permissable touch voltage curves in standard EN50522 without any success.

Can someone please share how to derive these curves? An ExCeL worksheet will be appreciated:)

Many Thanks

## RE: Permissable touch voltage - derivaton of curves in EN 50522

Using the list in Table B.3 where some points appear, you can find the other points by interpolation. More precisely, you can copy the curve and measure the paper in mm and calculate proportionally.

## RE: Permissable touch voltage - derivaton of curves in EN 50522

How is for example 716 V been calculated? Can you show this?

## RE: Permissable touch voltage - derivaton of curves in EN 50522

For additional details, see the enclosed excerpt and the references.

## RE: Permissable touch voltage - derivaton of curves in EN 50522

## RE: Permissable touch voltage - derivaton of curves in EN 50522

## RE: Permissable touch voltage - derivaton of curves in EN 50522

However the standard gives some hint on how to derive the curves given the formula in Annex A and values for body impedance and body current given in annex B.

The curve in figure 4 in the standard are based on weighed averages for permissable touch voltages as discussed in thread238-305712: Calculation of Touch and Step Voltage Limits using EN50522.

User Radug came Close to calculate the values, so his input will be valuable.

## RE: Permissable touch voltage - derivaton of curves in EN 50522

for each possible circuits as the Standard shows, with different corrections factors HF and BF, and

calculate a weigthed average.

I have a program to do this job, without additional resistance and with the values of additional

resistance from Standard.

The program generates a lot of values, for you request of t=0.05 s, the Table B.3 has the value 716 V,

the program calculates 712.84 V.

TABLE C.3 AND FIGURE 9.1

TIME OF FAULT : 0.05

HF : 1.

BF : 0.75

WEIGTH : 1.

TOTAL ADDITIONAL RESISTANCE : 0.

BODY RESISTANCE : 820.939836 at 554.13439 V

CORRECTED BODY RESISTANCE : 615.704877

TOTAL TOUCH RESISTANCE : 615.704877

PERMISIBLE BODY CURRENT : 900.

PERMISIBLE TOUCH CURRENT : 900.

BODY VOLTAGE : 554.13439

PROSPECTIVE TOUCH VOLTAGE : 554.13439

TIME OF FAULT : 0.05

HF : 0.8

BF : 0.75

WEIGTH : 1.

TOTAL ADDITIONAL RESISTANCE : 0.

BODY RESISTANCE : 780.306292 at 658.383434 V

CORRECTED BODY RESISTANCE : 585.229719

TOTAL TOUCH RESISTANCE : 585.229719

PERMISIBLE BODY CURRENT : 900.

PERMISIBLE TOUCH CURRENT : 1125.

BODY VOLTAGE : 658.383434

PROSPECTIVE TOUCH VOLTAGE : 658.383434

TIME OF FAULT : 0.05

HF : 1.

BF : 0.5

WEIGTH : 1.

TOTAL ADDITIONAL RESISTANCE : 0.

BODY RESISTANCE : 929.401269 at 418.230571 V

CORRECTED BODY RESISTANCE : 464.700634

TOTAL TOUCH RESISTANCE : 464.700634

PERMISIBLE BODY CURRENT : 900.

PERMISIBLE TOUCH CURRENT : 900.

BODY VOLTAGE : 418.230571

PROSPECTIVE TOUCH VOLTAGE : 418.230571

TIME OF FAULT : 0.05

HF : 0.4

BF : 1.

WEIGTH : 0.7

TOTAL ADDITIONAL RESISTANCE : 0.

BODY RESISTANCE : 775. at 1743.75 V

CORRECTED BODY RESISTANCE : 775.

TOTAL TOUCH RESISTANCE : 775.

PERMISIBLE BODY CURRENT : 900.

PERMISIBLE TOUCH CURRENT : 2250.

BODY VOLTAGE : 1743.75

PROSPECTIVE TOUCH VOLTAGE : 1743.75

TIME OF FAULT : 0.05

HF : 0.04

BF : 1.

WEIGTH : 0.

TOTAL ADDITIONAL RESISTANCE : 0.

BODY RESISTANCE : 775. at 17437.5 V

CORRECTED BODY RESISTANCE : 775.

TOTAL TOUCH RESISTANCE : 775.

PERMISIBLE BODY CURRENT : 900.

PERMISIBLE TOUCH CURRENT : 22500.

BODY VOLTAGE : 17437.5

PROSPECTIVE TOUCH VOLTAGE : 17437.5

average 712.843349

==================

---------- values for different times were deleted

==================

RF = 0.0000 OHM

NR. Tf (S) UvtP I Table B.1 Table B.3

----========------------============

1 0.05 712.8433 900.0000 716.0000

2 0.10 610.6242 750.0000 654.0000

3 0.20 508.3179 600.0000 537.0000

4 0.50 219.5357 200.0000 220.0000

5 1.00 116.7734 80.0000 117.0000

6 2.00 95.6989 60.0000 96.0000

7 5.00 85.4868 51.0000 86.0000

8 10.00 84.3328 50.0000 85.0000

Sorry, my English is bad.

Regards,

OPH. 2018-04-27 05:34

## RE: Permissable touch voltage - derivaton of curves in EN 50522

How do you calculate the average of 713 V?

Im calculating as follows which may be incorrect:

554 + 658 + 418 + 1744*0,7 / (1+1+1+0,7) = 2851 / 3,7 = 770 V. What am I doing wrong here?

## RE: Permissable touch voltage - derivaton of curves in EN 50522

For instance, what does mean PERMISIBLE TOUCH CURRENT?

What formula did you use in order to calculate VTP?

It is not from Annex A Utp=Ib(tf)*ZT(Ut)*BF/HF.

For instance for left hand to feet :

Utp=0.9*615.7*0.75/1=415.6 and not 554.13

## RE: Permissable touch voltage - derivaton of curves in EN 50522

(554+658+418+1744*0.7)/4= 713

For 7anoter4:

Thank you for you post, erdep. However, there are some incomprehensible points.

For instance, what does mean PERMISIBLE TOUCH CURRENT?

What formula did you use in order to calculate VTP?

It is not from Annex A Utp=Ib(tf)*ZT(Ut)*BF/HF.

For instance for left hand to feet :

1) Utp=0.9*615.7*0.75/1=415.6 and not 554.13

The factor 0.75 is taken into account when the non-linear circuit is solved

Utp=0.9*615.7/1= 554.13

2) For instance, what does mean PERMISIBLE TOUCH CURRENT?

Permisible Touch Current is the current in the circuit with the same

effect in the heart as Hand to Hand (HF=1.0).

For example, for feet to feet circuit with HF =0.04, this circuit

allows 900/0.04 = 22500 mA, with 900 mA in the heart.

In this case, it is step voltage, we may accept it is a special case

of touch voltage.

This enormous allowed current is the reason to not calculate step

voltage/current. It is not taken into account in the average.

I have a program to verify ground grids that uses this Standard (and

IEEE 80). IEEE 80 requires step voltages calculation.

The programs are free, but I am not sure if I can add a link here.

OPH.

## RE: Permissable touch voltage - derivaton of curves in EN 50522

How did you calculate the different Z(Ut) by the way? In EN50522 only 775 V for the highest touch voltage is stated, while you have calculated different values depending on the different circuit configurations.

I think you can attach the programs to this thread.

## RE: Permissable touch voltage - derivaton of curves in EN 50522

Tha values are rounded to 25 Ohm, it make difficult to obtain more accurate result

for different voltages not in the table. I used interpolation.

By the way, it is convenient to use interpolation in log(x) and log(y) tables for all variables (R(v), I(t), etc.)

This may be not true for high values of V, but is that I have.

Such values are for very short times, habitually the protection times are bigger, say 0.5 to 2.0 s.

Table B.3 and Fig. 4 of EN50522 are for Raditional=0. Figure B.2 are for different Raditional.

The programs can be downloaded from:

https://www.dropbox.com/s/qp0fd2l6fk7n1rj/erdeeng....

Both the titles and the manual are in my English...

All was done as hobby, surely a commercial program does all better, but not as cheap.

## RE: Permissable touch voltage - derivaton of curves in EN 50522

Thanks for Your post. It clears up a lot!

Im trying to create the table below from your previous post in the program. I assume I have to change some data in the SAMPLE.dat file then run erdep 2? Correct?

1 0.05 712.8433 900.0000 716.0000

2 0.10 610.6242 750.0000 654.0000

3 0.20 508.3179 600.0000 537.0000

4 0.50 219.5357 200.0000 220.0000

5 1.00 116.7734 80.0000 117.0000

6 2.00 95.6989 60.0000 96.0000

7 5.00 85.4868 51.0000 86.0000

8 10.00 84.3328 50.0000 85.0000

## RE: Permissable touch voltage - derivaton of curves in EN 50522

To obtain any value of the table you must run the program four times, with

HF= 1.0, 0.8, 1.0, 0.4

BF= 0.75, 0.75, 0.5, 1.0

Weigth= 1.0, 1.0, 1.0, 0.7

and calculate the average.

The table shown is for Raditional=0.0

The Rad can be added in a line with $F.

This value is for Rho=0.0. The programs erdep* dislike Rho=0.0, use a small value, say 0.01.

All the cases of Fig. B2 of EN50522 (Rad= 0.0, 750.0,1750.0,2500.0 and 4000.0D0 Ohm)

are calculated by the program en505222010.exe

https://www.dropbox.com/s/b84ozc4pg3n3fj1/en505222...

For the programs erdep* you can use the values as indicated in Fig. B2.

Recall they calculate one circuit at time.