THE OVERVOLTAGES PROTECTIONS SYSTEMS

IN MAIN VOLTAGE SUPPLY OF LARGE INDUSTRIAL HALLS

K.Wincencik A. W. Sowa chris@ceti.com.pl a.sowa@interia.pl

DEHN POLSKA DEHN POLSKA

Poland Poland

Abstract: The overvoltages protection of electronic

and electric devises or systems required the correct

cooperation between the Surge Protective Devices

(SPDs) subjected to different classes in multistage

protective systems. This is especially important in

main voltage supply of large industrial buildings dur-

ing direct lightning strokes to the lightning protection

systems or steel constructions.

Keywords: surge protective devices, lightning protection

systems, large industrial constructions,

1. INTRODUCTION

According to a Lightning Protection Zone concept, the

overvoltage protection of electronic and electric devises,

required the correct cooperation of SPDs in multistage

protective system. This cooperation was investigated by

computer simulation of surge protected low voltage sys-

tems in large industrial halls during direct lightning

stroke to the LPS or to the steel construction of these

buildings.

The aim of the study was the evaluation of:

¶ surge current distribution in the wires of low voltage

power systems,

¶ the influence of these distributions on the overvolt-

age systems in low-voltage supply nets,

¶ the overvoltages which appeared on different SPDs.

As a results of calculation it is possible to find the energy

coordination between the surge protective devices inside

the building and voltages on the output of protective

systems.

2. MULTISTAGE SYSTEMS OF SPDs

Creation of lightning and overvoltages protection systems

in low voltage power nets requires to comply the follow-

ing requirements which concern the SPDs:

1. Number of surge protective devices and the manner

of their montage should be adopted to the low volt-

age system (TN-, TT- and IT systems are taken into

account).

2. SPDs should be places in such manner, that their

limited overvoltages to the levels which are required

in select impulse withstand voltages.

3. Short-current resistance of SPDs should be adopted

to the values of short currents which can appeared in

the places of their montage.

4. The distance between:

- the surge protective devices subjected to differ-

ent classes,

- SPDs and protected devices,

- SPDs of class I and the other electric devices in

the places of their montages

should be define taking into account the producer’s

recommendation.

Calculation of surge protection systems in the case of

the direct lightning stroke to the building are pre-

sented.

3. COMPUTER SIMULATION OF

MULTISTAGE PROTECTION SYSTEMS

The possibility of cooperation between surge protective

devices subjected to different classes can be estimated

on the ground of laboratory investigation or theoretical

calculations.

Realization of laboratory investigation require the spe-

cialistic measurement equipment, and received results

are difficult generalize to other arrangements of protec-

tion systems. These facts caused the increase of interest

with the theoretical simulations.

Below the results of theoretical investigation are pre-

sented. We analysed two- and three-stages systems of

voltage-switching and voltage-limiting SPDs using pro-

gramme Pspice v.7.1.

3.1. Voltage-switching SPDs

Voltage-switching SPDs, tested to class I, are generally

recommended for localization at points of high expo-

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sure for lightning currents and lightning and switching

overvoltages. In theoretical considerations the model of

SDP class I were realized on the base of switch

Sw_tClose from programme Pspice library. The fol-

lowing parameters of switch is taken into account:

- tClose – time of close, defined from voltage-time

characteristics of SPD class I,

- ttrans – time of switching duration – 0,01 ms or

0,1ms,

- Rclosed – resistance when the switch is closed –

0,0015 W or 0,002W,

- Ropen – resistance when the switch is open equal

100 MW

Fig.1 present the answer of SDP class I calculated with

these parameters.

Fig. 1.The overvoltage on the SPD class I

3.2. Voltage-limiting SPDs

Voltage-limiting SPDs, tested to class II and III, most

often are metal oxide varistors.

In calculation we take the model of varistor which is

proposed by Manfred Holzer and Willie Zapsky [7 ]. The

equivalent circuit diagram of varistor is presented in

fig.2.

R_series

L_series

R_par

C_par

Fig.2. Equivalent circuit diagram of varistor.

Symbols in presented model of varistors are following:

- R_series – resistance require from mathematical

reason (constant value R_series = 100nW),

- L_series – inductance of wires which connect varis-

tor in power system (approximately – 1nH/mm) and

internal inductance of varistor,

- C_par – capacity of varistor,

- R_var – descried the non-linear current-voltage

characteristic of varistor.

Resistance R-var is realized using the voltage source

which is control by current and is described by following

function:

log(u) = P1 + P2 + P3 + P4

where: P1 = b1

P2 = b2 · log(i)

P3 = b3 · exp(-log(i))

P4 = b4 · exp(log(i))

Parameters b1, b2, b3, b4 are define for each type of varistor.

3.3. Models of the surge protection systems

The theoretical analyses were done for low voltage power

systems in large industrial halls in following arrange-

ments:

- two-stage protection systems - the arrangements with

SPDs class I and II,

- thee-stage protection systems – the arrangements with

istances between transformer and the first step of pro-

m to

50m.

m 10m to 50m between SPDs class I and II,

¶ which simulated the equipment

with the following parameters:

350 with the

lue 200 kA,

0).

m

for om transformer about 150m. In

SDPs class I, II and III,

The transformer is located outside and inside the hall.

D

tection – SPDs class I – were changed from 20

1

The calculation were made for the variable:

¶ distances

- fro

- from 5m to 50m between SPDs class II and III.

resistances of loads

connected to the low voltage power system – from

10W to 1kW,

¶ sparkover voltages of the SPDs class I (for 1500V,

2500V and 4000V).

The lightning current is simulated by the ideal current

sources

- the first lightning strokes- current 10/

peak va

- the subsequent strokes- current - 50kA (0,25/10

4. EXAMPLES OF MATHEMATICAL

RESULTS

So e examples of computer simulation will be presented

building far-away fr

low voltage power nets will be the two- and three-stage

protection systems. The arrangements which is simulated

was presented in fig.3.

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otection

system

Transformer Earthing

system

Lightning

arr nters

Overvoltage

arresters PAS

Lightni

ren

l2

ircuit diagram for two stage protection system shows

e fig.4. The surge currents distributions in SPDs class I,

arthing systems of building and in transformer for the

rst and subsequent lightning currents are presented in

g.5 and 6.

he results were obtained for the parameters of power

ets, transformer and earthing systems which are pre-

nted in Table 1.

ome examples of overvoltage at the SPD class II and

urrent which is flowing in it for:

- the surge current 10

- sparkover voltages of the SPDs class I – 1500V.

C

th

e

fi

fi

T

n

se

S

c

/350,

are presented in fig.7.

ng

t

e

s

t

Lightning pr

l1 l3

cur

Lt1

Lt2

Lt3

Rlt

Rt2

Rt3

Rn

L11

L12

L13

L14

L21

L22

L23

L24

Ro1 Ro2 Ro3 Ro4

Ret

Let

Et

VV2

V3

Les

Re

Surge

current

R11

R12

R13

R14

R21

R22

R23

R24

L1

L2

L3

N

PE

SG1 SG2 SG3

L25 R25

W1,W2,

W3,W4

Rw1

Rw2

Rw3

Rw4

1

Fig.3. Low voltage power net with thee-stage protection systems

Fig.4. Circuits diagram of simulated wo stage protection system

Fig.5. Distribution of lightning current 10/350.

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Fig.6. Distribution of lightning current 0,25/100

Table 1. Parameters of elements for example in fig.3 [2,3]

Element Values

Mutual inductance LS1, LS2,

LS3, L24

10µH -

20 µH

Resistance of power supply cable R11, R12, 1mW/m; (between transformer and SPDs) R13, R14 l =150m

Inductance of power le

PDs)

L11, L12,

supply cab

(between transformer and S L13, L14

1µH/m;

l =150m

RES 10W

Inductance of building’s earthing system LES 5µH

Resistance of earthing system - trans- R

former Et 1W

Inductance of earthing system - trans- L

former Et 5µH

Resistance and inductance of the trans-

former secondary wires

Rt1, 2 t3

Lt1, 2 t3 50µH

Rt , R

Lt , L5mW

Capasitance of transformer – secon- Ct1, Ct2, Ct3 2nF

dary wires

Resistan

former

V1=22 V, 5 z j=0¯2=220V 0Hz

j

Phase voltag

3=2 0Hz

Resistance of building’s earthing system

ce of neutral line of the trans- Rt4 2mW

0 0H

V , 5

=120¯ es of the transformer

V 20V, 5

j=240¯

Fig.7. Overvoltage and current in SPD class II in protec-

tion system from fig. 4.

dditionally on fig.8. the spectral analyses of these

PDs.

Fig. 8. Spectral analysis of the curves from fig 7.

5. CONCLUSIONS

sys-

ms can be effectively realized by computer simulation.

In calculation th tning strokes to

uildings, was analysed. From the simulation’s results, it

only for the simple model of the

S

dif

f Buildings;

Protection handicap Safety; Protection Against Over-

voltages; Prote tages of Atmos-

pheric Origin or Due this {then} Switching.

3. I ices.

-

5. A ge

-

92;

7. M ice:

A

curves are presented. Similar consideration were made

for thee stage system of S

The complex coordination of SPDs in low voltage

te

e worst case, direct ligh

b

is possible to estimate:

- energy exposures for SPDs different classes in multi-

stage overvoltage protection systems,

- protection levels for different arrangements of SPDs.

This analysis was made

PDs class I. Nowadays we try to find the solution for

ferent models of spark gaps in SPDs.

6. REFERENCES

1. IEC 364-4-443 Electrical Installation o

ction Against Overvol

2. IEC 61312-3 Draft of and Technical Report Type 2

prepared TC 81 ACCORDING TO 3 PG 3( January

1998) Requirements of Surge Protective Devices.

EC SC 37A Low voltage surge protective dev

4. IEC SC 37B Specific components handicap low volt

age surge protection devices.

ltmeier, Pelz, Scheibe: Computer simulation of sur

voltage protection in low-voltage systems; 21. Of in

ternal medicines. Conf. He Lightning protection,(

Reef. Number 7. 08); Berlin 19

6. SIOV Metal Oxide Varistors Databook, Siemens Mat-

sushita; repr1995.

. Holzer, Zapsky In.: Modeling varistors with Psp

Simulation beats trial and error;