OVERVOLTAGE PROTECTION · 2020. 6. 13. · Overvoltage protection Electronic components are...

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Overvoltage protection

Electronic components are increasinglyreplacing electrical components in pro-duction installations. PLC controls and PCapplications are replacing relay technology.Interferences from overvoltage or switchingactions are causing failures or damage tothe installation components. Appropriateovervoltage or surge protection can largelyeliminate this damage.

Components for overvoltage protectionWeidmüller uses various components toprovide a versatile range of overvoltageprotection units:• Gas discharge tubes• Metal-oxide varistors• Suppression diodesThese components have specific charac-teristics, so that careful coordination isrequired to provide effective overvoltageprotection.

• Gas Discharge TubesThe so-called Gas Discharge Tube con-sists of two electrodes spaced a definenddistance apart enclosed in a small glass orceramic tube. The electrical properties areessentially determined by the type of gas,gas pressure and the electrode spacing. Inthe event of a voltage surge, an arc is pro-duced between the electrodes. The ioni-zed gas discharge path changes from highresistance to low resistance. This dischar-ge process prevents a further surge rise,where the arcing voltage drops from about10 – 30 V. The low resistance offered bythe device is capable of allowing a highsurge current to flow, i. e. since extinctionof the surge current does not necessarilyoccur, it may be necessary to fit a fuse inthe circuit for protection. Precise extinction conditions prevail at:– Operating voltages less than the arcing

voltage (typical 10 – 30 V)– Operating voltages less than 100 V and

short-circuit current less than 0.1 A.

DC sparkover voltageThis value indicates the firing voltage forDC voltage or a slow rate of rise (du/dtabout 100 V/s).

Impulse sparkover voltageThis value describes the dynamic beha-viour of the gas discharge tube in basedon a rate of voltage rise of du/dt = 1 kV/µs(VDE 0845).

Leakage currentTwo procedures are used here, namelyDIN VDE 0432 Part 2, IEC 68 and CCITT.nCCITT: 10 loads (8/20 µs) at intervals of3 min, or acc. VDE; 5 loads (8/20 µs) atintervals of 30 sec. Typical values are 2.5, 5, 10, 20 kA. DIN IEC 68 lists the mechanical / climaticconditions. Here vibration, shock andothers are tested as are, e.g. in Part 2.3the effect of humid elevated temperaturefor 21 days, 40 °C, 93% relative humidity.Operating temperature range:–40 °C...+90 °C. The capacitance of the earth is typicallyseveral pF.

• VaristorsMetal oxide varistors are used. They areapproved for a maximum sinusoidal ACoperating unit. Any voltage higher thanthat stated is reliably arrested.Varistors can be used for medium to highpowers.

These voltage dependent resistors consistof zinc oxide. The varistor is available invarious designs. Disc varistors are prima-rily used. If the varistor is at max. permit-ted voltage limit a false current of a few µAflows through it.Varistors are tested by the manufacturer toDIN IEC 68 and to CECC 42000(DIN 45923).

DIN IEC 68 lists the mechanical / climaticconditions. Here vibration, shock andothers are tested as are, e.g. in Part 2.3the effect of humid elevated temperaturefor 56 days, 40 °C, 93% relative humidity.Operating temperature range:–40 °C...+85 °C. Storage temperature up to +125 °C.

CECC 42000 lists, e.g. the voltage limit(>2.5 kV), impulse current derating(8/20µs), insulation resistance > 1 GOhmand the typical response time of < 25 ns.

Varistors used at standard mains impe-dances should be of the type S14 andS20. S14 can be fused with max. 10A,S20 with max. 16A.

Energy uptake (2 ms) of the varistor isbetween 0.3 J to 200 J, depending ondesign.

The capacitance of the varistor is design-dependent and is between 0.1 and 37 nFat 1kHz.

Varistor Approvals– Underwriters Laboratories, Inc. (UL)

– UL 1414 Across-the-line components: File E77005 (N) Types S05 /S07 /S10/S14/S20, at voltage levels K130to K 300

– UL 1449 Transient voltage suppressors:File E77005 (M): All disc types which arebuilt primarily into DKU, EGU, LPU,RSU.

– Canadian Standards Association (CSA)

– Class 2221 01 Accessories and Partsfor Electronic Products

All disc types with a voltage of > 115 V;for use as across-the-line transient protectors: File LR 63185

– Schweizerischer ElektrotechnischerVerein SEV

Protection Class I, IP00, Test conditionsCECC 42200; Test report 90.102484.01 of 17.7.91 forS05/S07/S10/S14/S20.

• Suppression diodesSuppression diodes work on a similar prin-ciple to conventional zener diodes. If theindicated breakdown voltage is exceeded,the diode conducts. Compared to zenerdiodes, suppression diodes have a highercurrent carrying capacity and faster res-ponse times typically within the ps range.

Suppression diodes are only suitable forrelatively small impulse peaks (up to maxi-mum 1.5 kW/ms).

The capacitance of the diodes is typicallybetween 9500...360 pF at 1 MHz. The supressor diodes can convert max.1500 W for 1 ms to heat, depending ontype.

When the diode is overloaded the P-Ninterface short-circuits. If energy continuesto be fed the P-N interface is destroyed.

These diodes can be used to protect coils,or can also be used in combination withgas arrestors or varistors.

Supressor diodes are available as unidirec-tional and bidirectional diodes. Weidmüller24 VDC overvoltage protection modulesfrequently contain unidirectional diodes.

Here the voltage in barrier direction istypically 29V and in transmission direction0.7 V.

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kV

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kV

0,5

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tInput impulse Output impulse

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U


U

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Overvoltage protection applicationsCombination unit

Overvoltage surges on measurement andcontrol signals, data or power supply linescan cause considerable operational dis-ruption.Failure of electronic circuits or completesystems can cause serious damage toproperty and even personal injury.Overvoltages are caused, among otherthings, by atmospheric discharges andswitching operations and are relevant inthe following areas:

• Telemetry Control systems• Signal systems• Data Processing equipment• Process Control terminals• Instrumentation and Control technology• Meteorological stations

These systems must be protected againstovervoltages.

The necessity of providing overvoltageprotection is illustrated in the followingexamples:

• In measuring and control stations, allsensor and actuator cables from thefield and the sensors themselves mustbe protected against overvoltage.

• Power stations, water tapping systemsor sewage treatment plants must beprotected not only against direct light-ning strikes, but also against the effectsof remote strikes. The sheer size ofthese plants and the extensive electro-nic systems they incorporate makeovervoltage protection a necessity.

• In traffic control systems, such as lockand signal systems overvoltage protec-tion units are essential for safety.

• Frequency converter controlled machi-nes modulate system voltage with high-frequency interference and also affectother electronic units.

• Power supply and data lines of compu-ters and their peripheral equipmentmust be protected to ensure safeoperation.

These examples clearly define the areas ofapplication of overvoltage protection.

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20 40 60

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Voltage waveshape at overvoltage protection unit EGU 2

By employing a combination of theaforementioned components, close over-voltage protection can be provided tomeet individual requirements. When a vol-tage surge appears at the input to thisunit, the gas discharge tube fires anddiverts the high current. The residualimpulse is dampened by the inductors,varistor and suppression diode. If the gas discharge tube does not fire (i. e. for less steep rise time surges), theimpulse will be dampened only by thevaristor and the suppression diode. This type of component configuration pro-vides increased sensitivity to a high surgevoltage as it travels from stage to stagetowards the output. An impulse voltagewith the standard rise time of 1 kV/µs anda peak value of 10 kV at the input will belimited to approximately 600 – 700 V bythe gas discharge tube.

The second stage of the varistor, which isinductively coupled to the first, limits thisvalue to about 90 V and the suppressiondiode further limits the impulse to about35 V at the output.This shows how the successive stagesprotect the subsequent electronics limitingthe output to about 1.5 x VB.

Overvoltage protection

Installation of cables

Signal cables should berouted by the shortest pathto the close overvoltageprotection units and furtherto the electronics. Parallelrouting of cables and rou-

ting of protected and unprotected cablestogether should be avoided. (Particularreference is made to cable routes andcable ducts!). If parallel routing cannot beavoided, a spacing of minimum 0.5 metresshould be maintained.

Module marking

The overvoltage protectionunits are marked either byan arrow or the word “IN”.The arrow points to the pro-tected side of the unit, i. e.overvoltage is suppressed in

the arrowed direction (see combinationunit).

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2

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4IN OUT

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Technical rules for flammable liquidsTRbFExtract from TRbF 100

Requirements:1. Buildings containing above-ground

installations (subject to special permis-sion) for the storage, filling or trans-portation of flammable liquids, as wellas outdoor tanks above and belowground which are not enclosed on allsides by soil, brickwork or concrete orseveral of these materials, must beprotected by the provision of suitablearrangements against ignition hazardsand lightning (e.g. complying with therequirements of DIN VDE 0185 Parts 1 and 2).

2. Section 1 also applies to outdoor tanksabove ground which are used for thestorage of flammable liquids of thedanger classes A I, A II or B in onetank.

3. For intrinsically safe circuits which areused, e.g. for instrumentation and con-trol purposes, whose cables are routedin the tank, applicable are independentof Sections 1 and 2 and over andabove.

– outdoor tanks below ground*),

– tanks in buildings susceptible to light-ning strikes due to the cable routing(also remote lightning strikes*).

Resulting requirements:1. Prior to cables into tanks, the overvol-

tage protection in a metal housing (e.g.terminal box, housing for integratedmeasuring transducer or similar) mustbe provided. The metal housing withovervoltage protection must beconnected to the tank wall or scree-ning electrically conductive, so thatreliable equipotential bonding isensured.

2. For the supply cable from the instru-ment board to the metal housing withovervoltage protection, a suitablecable/conductor **) must be used.From the overvoltage protection to thestorage tank, a cable/conductor withmetal sheath, screening or a suitablecable/conductor in a protective metaltube must be used. The metal sheath,screening or protective tube must beconnected to the equipotential bonding(earth). For the cable/conductor over-voltage protection to the storage tank,the r.m.s. test voltage (Ueff) betweenthe conductors and the metal sheath,screening or protective tube must beminimum 1500 V.

3. The cable/conductor between themetal housing with overvoltage protec-tion and entry into the tank must berouted in such a way that a lightningstrike in this cable/conductor is impro-bable.

*) These requirements apply, for example, to level meters orsimilar measuring devices which are installed in outdoor tanksbelow ground and from which a cable is routed below groundinto a building (e.g. petrol station buildings).

**) In accordance with harmonization documents 21 and 22CENELEC

Overvoltage protection for intrinsically safe circuits

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Weidmüller offers a complete solution for this application!• Metal enclosure with BASEEFA approval EEx e II T6

• Overvoltage protection with PTB approval EEx ia IIB/IIC T4/T6

• Metal enclosure complete with glands and overvoltage protectionto meet individual requirements.

Actuator

Overvoltage protection 1

Tank filled with flammable liquid

Overvoltage protection 2

Sensor

Metal housing with integrated over-voltage protection

Screened cable

The point Overvoltage protection 1is permanently earthed!

The overvoltage protection units LPU 800843 24 VAC/DC 1.5 A or LPU 800844 48 VAC/DC 1.5 A are used for this purpose.

This is a plug-in protection unit for use inthe SEG-U housing. It can also be fitted inthe terminal design:DKU 801580DKU 801581 24 VDC 0.1 or DKU 801928DKU 801929 48 VAC/DC 0.1 A

The point Overvoltage protection 2is earthed floating via a gas dischargetube!

Earthing takes place via a gas dischargetube with 470 V from cable to earth (Type DK4U 940044 and DK4U 940045).

Overvoltage protection can be providedbetween the cables, for example:LPU 822524 24 VDC 0.1 ALPU 822525 48 VDC 0.1 A or overvoltage protection in the terminaldesign:DK4U 940040 DK4U 940050.

According to TRbF, overvoltage protection2 must be arranged in a metal housingprior to routing the cable into the tank.The housings STB 1 and NEXT 26/26/16are used for this purpose.

These housings are approved for hazar-dous areas use by the BASEEFA EEx e IIT6. The housings must be conductivelyconnected to the tank.


152


Overvoltage protection 2in 12 mm wide terminal design with individual components

Schematic circuit diagram

Overvoltage protection 1in 6 mm wide terminal design


Technical data

Rated voltage U1.2

Max. permissible voltage U1.2

Through resistance1.3

Inductance of four-pole network LI ≤Capacitance of four-pole network CI ≤Source impedance frequency response

at 50 Ω/-3 db at Ri = … ΩMax. rated current per path

∆Tü at 0.1 A and

60°C ambient temperature

Gas arrester type

Varistor type

Suppression diode type

Inductor

Rated AC discharge current

Terminal material

Sparkover voltage of surge arrestor

at 1000 V/µs at input

Interference voltage at rated voltage


Interference voltage at rated voltage

at 8/20 µs and 5 kA at input

Max. leakage current at rated voltage Un

and max. temperature Tu from terminal 1 to 2 (PA)

IP protection

Storage temperature

Operating temperature

Clamping point

solid

flexible

Approvals

Ordering data

24 Vdc

28 Vdc

3,5 Ω170 µH

2,5 nF

(… at Ri = 240 Ω)

500 kHz

0,1 A

18 K

90 V 2,5 kA

S07 K30

ZP 1033 A 0,6 kW

2 x 70 µH 0,1 A

–

PA 66

typ. 700 V

typ. 33 V

max. 38 V

10 µA

Safe from finger-touch

to DIN VDE 0106 Part 100

- 25 … + 85 °C

- 25 … + 60 °C

Self-locking screw

0,5 … 4 mm2

0,5 … 4 mm2

Ex ia IIC/IIB T6/T4 PTB Nr.

Ex-93.Y.4601 X

Type Cat. No.

DKU 24 Vdc 8015800000

0,1 A TS 32

DKU 24 Vdc 8015810000

0,1 A TS 35

48 Vac/dc

75 Vdc/54 Vac

3,5 Ω170 µH

1,0 nF

(… at Ri = 480 Ω)

1000 kH

0,1 A

11 K

230 V 2,5 kA

S07 K60

P 6 KE 82 CP 0,6 kW

2 x 70 µH 0,1 A

–

PA 66

typ. 700 V

typ. 82 V

max. 100 V

10 µA


DIN VDE 0106 Part 100

- 25 … + 85 °C

- 25 … + 50 °C

Self-locking screw

0,5 … 4 mm2

0,5 … 4 mm2


Ex-93.Y.4601 X

Type Cat. No.

DKU 48 Vac/dc 8019280000

0,1 A TS 32

DKU 48 Vac/dc 8019290000

0,1 A TS 35

56 Vdc/40 Vac

≤ 0,1 Ω0 mH

0 µF

10 A

typ. 15 K

90 V 20 kA

25 A

PA 66

typ. 650 V

0 µA



- 25 … + 85 °C

- 25 … + 60 °C

Self-locking screw

0,5 … 4 mm2

0,5 … 4 mm2


Ex-93.Y.4601 X

Type Cat. No.

DK4U 48 Vdc 9400400000*

TS 32

DK4U 48 Vdc 9400500000*

TS 35

± 283 Vdc/200 Vac

≤ 0,1 Ω0 mH

0 µF

10 A

typ. 15 K

470 V 20 kA

25 A

PA 66

typ. 1100 V

0 µA



- 25 … + 85 °C

- 25 … + 60 °C

Self-locking screw

0,5 … 4 mm2

0,5 … 4 mm2


Ex-93.Y.4601 X

Typ Cat. No.

DK4U 110 Vdc 9400440000*

TS 32

DK4U 110 Vdc 9400540000*

TS 35

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Schematic circuit diagram

Overvoltage protection 1for 20 mm wide SEG/U housing

Overvoltage protection 2for 20 mm wide SEG/U housing

Overvoltage protectionfor intrinsically safe circuit


Technical data

Rated voltage U1.3

Rated voltage U1.2 and U2.3

Max. permissible voltage U1.3

Max. permissible voltage U1.2 and U2.3

Trough resistance 1, 4 and 2, 6

Inductance of four-pole network LI ≤Capacitance of four-pole network CI ≤Source impedance frequency response

at 50 Ω/-3 db at Ri = … ΩMax. rated current per path

∆Tü at 1.5 Aeff and



Gas arrestor type

Varistor type

Suppression diode type

Inductor

Location cover material

Sparkover voltage of surge arrester


Interference voltage at rated voltage 4.6


Interference voltage at rated voltage 4.6

at 8/20 µs and 5 kA at input

Max. leakage current at rated voltage Un

and max. temperature Tu from terminal 1 to 2 (PA)

…from terminal 1 to 3

IP protection

Storage temperature

Operating temperature

Clamping point

solid

flexible

Approvals

Ordering data

24 Vac/dc

24 Vac/dc

34 Vdc/27 Vac

31 Vdc/25 Vac

0,15 Ω75 µH

7,5 nF

(… at Ri = 16 Ω)

150 kHz

1,5 A

32 K

2 x 90 V 5 kA

2 x S10 K25

CP 2039 A 1,5 kW

4 x 15 µH 1,5 A

PA 66

typ. 700 V

typ. 39 V

max. 65 V

10 µA



- 25 … + 85 °C

- 25 … + 50 °C

Self-locking screw

0,5 … 4 mm2

0,5 … 4 mm2


Ex-93.Y.4601 X

Type Cat. No.

LPU 24 V ac/d 8008430000

1.5 A current loops

48 Vac/dc

48 Vac/dc

74 Vdc/53 Vac

81 Vdc/59 Vac

0,15 Ω75 µH

3,5 nF

(… at Ri = 32 Ω)

300 kHz

1,5 A

32 K

230 V 5 kA

2 x S10 K60

P 6 KE 82 CA 0,6 kW

4 x 15 µH 1,5 A

PA 66

typ. 700 V

typ. 82 V

max. 115 V

10 µA



- 25 … + 85 °C

- 25 … + 50 °C

Self-locking screw

0,5 … 4 mm2

0,5 … 4 mm2


Ex-93.Y.4601 X

Type Cat. No.

LPU 48 V ac/dc 8008440000

1.5 A current loops

24 Vac/dc

%

29 Vdc

200 Vac/283 Vdc

13 Ω9,5 mH

6,0 nF

(… at Ri = 240 Ω)

4,5 kHz

0,1 A

25 K

2 x 470 V 5 kA

S10 K25

ZP 1033 A 0,6 kW

4 x 2 mH 0,1 A

PA 66

typ. 800 V

typ. 33 V

max. 38 V

0 µA

15 µA



- 25 … + 85 °C

- 25 … + 60 °C

Self-locking screw

0,5 … 4 mm2

0,5 … 4 mm2


Ex-93.Y.4601 X

Type Cat. No.

LPU 24 V dc 8225240000

0.1 A unearthed

48 Vac/dc

%

74 Vdc/53 Vac

200 Vac/283 Vdc

13 Ω9,5 mH

1,8 µF

(… at Ri = 480 Ω)

9 kHz

0,1 A

25 K

2 x 470 V 5 kA

S10 K60

P 6 KE 82 CA 0,6 kW

4 x 2 mH 0,1 A

PA 66

typ. 800 V

typ. 82 V

max. 90 V

0 µA

15 µA



- 25 … + 85 °C

- 25 … + 60 °C

Self-locking screw

0,5 … 4 mm2

0,5 … 4 mm2


Ex-93.Y.4601 X

Type Cat. No.

LPU 48 V ac/dc 8225250000

0.1 A unearthed

154

SEG-U/LPUEGF

Close overvoltageprotection units

DKUEGURSU

DK 4 U

Varistor

Gas discharge tube

DKU

with combination unit50

6056,5

42

57

65

Technical data

Terminal width (+ fitting tolerance 0,2 mm)

Insulation stripping length

Screw connection, solid

Screw connection, flexible

Conductor size

Accessories

Mounting rail

End bracket

End plate

Marking material

DKU

24 V/48 V/115 V 230 V

6 mm 12 mm

Type Cat. No.

TS 32 0122800000

TS 35 x 7.5 0383400000

TS 35 x 15 0498000000

EWK 2 (TS 32) 0199360000

EWK 35 (TS 35) 0199360000

AP (for DK 4 U) 0687560000

AP (for DKU) 0687560000

dekafix 5

DK 4 U

24 V/48 V/115 V 230 V

6 mm 12 mm

0,5…4 mm2

0,5…4 mm2

AWG 20…12

Type Cat. No.

TS 32 0122800000

TS 35 x 7.5 0383400000

TS 35 x 15 0498000000

EWK 2 (TS 32) 0199360000

EWK 35 (TS 35) 0199360000

AP (for DK 4 U) 0359260000

AP (for DK 5 U) 0359260000

AP (for DK 6 U) 4042030000

dekafix 5

Technical data

Terminal width (+ fitting tolerance 0,2 mm)

Insulation stripping length

Screw connection, solid

Screw connection, flexible

Conductor size

Accessories

Mounting rail

End bracket

Marking material

DK 4 U

20 mm

7 mm

0,5…4 mm2

0,5…4 mm2

AWG 26…14

Type Cat. No.

TS 32 0122800000

TS 35 x 7.5 0383400000

TS 35 x 15 0498000000

EWK 2 (TS 32) 0199360000

EWK 35 (TS 35) 0199360000

dekafix 5


SEG-U/LPU

96,6

121

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OVERVOLTAGE PROTECTION · 2020. 6. 13. · Overvoltage protection Electronic components are...

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