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Introduction

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ivCopyright © 2010 IEEE. All rights reserved.

This is an unapproved IEEE Standards Draft, subject to change.

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Interpretations

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Patents

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vCopyright © 2010 IEEE. All rights reserved.


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Participants

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viCopyright © 2010 IEEE. All rights reserved.


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Contents

<After draft body is complete, select this text and click Insert Special->Add (Table of) Contents>

viiCopyright © 2010 IEEE. All rights reserved.


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IEEE P<designation>/D<draft_number>, <draft_month> <draft_year>

DrafttxtTrialUsetxtGorRPorSTD for varTitlePAR

IMPORTANT NOTICE: This standard is not intended to ensure safety, security, health, or environmental protection. Implementers of the standard are responsible for determining appropriate safety, security, environmental, and health practices or regulatory requirements.

This IEEE document is made available for use subject to important notices and legal disclaimers. These notices and disclaimers appear in all publications containing this document and may be found under the heading “Important Notice” or “Important Notices and Disclaimers Concerning IEEE Documents.” They can also be obtained on request from IEEE or viewed at http://standards.ieee.org/IPR/disclaimers.html.

1. Overview

1.1 Scope

1.2 Purpose

2. Normative references

The following referenced documents are indispensable for the application of this document (i.e., they must be understood and used, so each referenced document is cited in text and its relationship to this document is explained). For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrigenda) applies.

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3. Definitions

As of June 2009, please use the following introductory paragraph and there is no requirement to number definitions. Please refer to the 2009 Style Manual for updates (http://standards.ieee.org/guides/style/2009_Style_Manual.pdf). To format terms and definitions in the IEEE-SA word template, you may NOW simply bold the "term:" and use regular body text (IEEEStds Paragraph style) for the definitions. DO NOT USE the IEEEStds Definitions or IEEEStds DefTerms+Numbers style. However, if the definitions have already been numbered with the template tool, STAFF will remove the numbering during the publication process. (NOTE: There are instances when a draft will need to number terms - please consult with an IEEE-SA editor). A new version of the template is being designed and tested to deal with the new definitions options. (2.2010).

For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary: Glossary of Terms & Definitions should be consulted for terms not defined in this clause.1

1 The IEEE Standards Dictionary: Glossary of Terms & Definitions is available at http://shop.ieee.org/.

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Annex A

(informative)

Impulse Generators

A.1 Introduction

This Annex covers:

Types of impulse generator

Impulse generator parameters

Impulse generators typically used for surge protector testing

Impulse generator circuits

Combination-wave generators

Expanding single output generators to multiple output

Generator variations

A.2 Types of impulse generator

Impulse generators can be classified into three types:

1. Generators with a defined voltage waveform typically used for high-voltage insulation testing

2. Generators with a defined current waveform typically used for high-current component and device testing

3. Generators with defined voltage and current waveforms. These generators can be subdivided into:

3.1. Circuit defined generators

3.2. Waveform defined generators

A.3 Impulse generator parameters

A.3.1 Glossary of Annex terms

The following terms are used in this Annex to describe the impulse and generator parameters.

virtual front time:

a) the front time T1 of a voltage impulse is 1/0.6 times the interval T between the instants when the impulse is 30 % and 90 % of the peak value

b) the front time T1 of a surge current impulse is 1.25 times the interval T between the instants when the impulse is 10 % and 90 % of the peak value

NOTE—Some standards use the 10 % and 90 % front time measurement for the voltage impulse.

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virtual origin; O1:

a) for the impulse voltage waveform, it is the instant at which a straight line drawn through the 30 % and 90 % amplitude values crosses the time axis.

b) for the impulse current waveform, it is the instant at which a straight line drawn through the 10 % and 90 % amplitude values crosses the time axis

virtual time to half-value; T2: interval of time between the instant of virtual origin O1 and the instant when the voltage or current has decreased to half the peak value

designation of an impulse shape: combination of two numbers, the first representing the virtual front time (T1) and the second the virtual time to half-value on the tail (T2)

NOTE 1—It is written as T1/T2, both in microseconds, the sign "/ " having no mathematical meaning.

NOTE 2—Combination wave generators have both voltage and current impulse designations given separated by a hyphen e.g. 1.2/50-8/20

NOTE 3—Waveshapes defined as maximum front time and minimum time to half value are expressed as <T1/>T2

undershoot: The peak value of an impulse voltage or current that passes through zero in the opposite polarity of the initial peak. [B1]

charge (impulse): time integral of the impulse current

I2t (impulse): time integral of the square of the impulse current

a) I2t is called the action integral for atmospheric lightning, joule integral for fuses and specific energy (W/R) for AC surge protectors.

b) The units for I2t are A2s, but assuming the current flows in a virtual 1 resistor may be expressed in energy units J (fuses) or W/ (AC surge protectors)

combination wave generator: generator with 1,2/50 µs or 10/700 µs open-circuit voltage waveform and respectively 8/20 µs or 5/320 µs short-circuit current waveform [B10]

fictive impedance (impulse generator): quotient of the generator open-circuit peak voltage value and the generator short-circuit peak current value

A.3.2 Virtual parameters

This clause covers the virtual (calculated) waveform parameters and their applicability. Figure A.1 shows an impulse designation based on the extrapolation of the 10 % to 90 % front-time levels. All current lightning surge impulses in this document use the 10 % to 90 % front-time designation. The <10/>250 and <10/>1000 [B9] impulse generators uniquely use the 10 % to 90 % front-time designation for the voltage impulse. All other impulse generators use a 30 % to 90 % front-time designation for the voltage impulse. The 8/20 current waveform is not necessarily unidirectional and has a maximum undershoot value specified.

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Figure A.2 shows a voltage impulse designation based on the extrapolation of the 30 % to 90 % front-time. All 30 % to 90 % front-time designated voltage impulses use nominal time values.

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A.4 Impulse generators typically used for surge protector testing

This clause lists commonly used or referenced impulse generators. The three tables cover generator types with voltage, current and voltage & current defined waveforms. A bibliographic reference is given for each designation of generator. Where there are duplicate designations, the most commonly used one is indicated. Clause A.8 gives further details on the duplicate designation generators.

A.4.1 Impulse generators with a defined voltage waveform

These generators are used for high-voltage insulation/dielectric testing. Capacitive loads will slow down the voltage front time. To compensate for capacitive loads above 5 nF, some generators have a selectable output resistance value. The generator design objective is to produce a precision voltage impulse. The generator design must be robust enough to survive the discharge current caused by any insulation breakdown. Generator #1 is the most commonly used variant of generators #1 and #2.

Table A.1—Voltage Impulse GeneratorsNumber Designation Condition Edge Time and

ToleranceAmplitude

1 1.2/50[B1][B2](IEC/IEEE)

Open-CircuitVoltage

Front 1.2 µs ±30 % ±3 %Decay 50 µs ±20 %

Short-CircuitCurrent

See NOTE

2 1.2/50[B4][B3](ITU-T/IEC)

Open-CircuitVoltage

Generator circuit defined –0% to +5%


See NOTE

NOTE—Current waveshape not defined.

A.4.2 Impulse generators with a defined current waveform

These generators are used for high-current component and device testing.

The 8/20 waveform is typically produced by an LCR series circuit that has a damping factor of less than one (circuit Q > 0.5). Such a design requires that the load voltage is kept to be much smaller than the charging voltage, e.g. a 1:10 voltage ratio. These generators produce a current through the load with an 8/20 waveshape, unlike the 1.2/50-8/20 generator which has its current waveform measured into a short-circuit.

The amount of energy developed in an MOV or fuse is governed by the applied waveform. The possible range in developed energy is reduced by tighter waveform tolerances. Generator #3 is the preferred and most commonly used one because it has a ±10 % waveform tolerance compared the ±20 % of generator #4.

Generator #5 has its current waveform expressed as charge and I2t values which can be simulated by a 10/350 waveform.

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Table A.2—Current Impulse GeneratorsNumber Designation Condition Edge Time and

ToleranceAmplitude

3 8/20[B1][B5][B6](IEEE/IEC)

Open-CircuitVoltage

See NOTE


Front 8 µs ±10 % ±10 %0 to -20 % undershoot

Decay 20 µs ±10 %

4 8/20[B5](IEC)

Open-CircuitVoltage

See NOTE


Front 8 µs ±20 % ±10 %0 to -30 % undershoot

Decay 20 µs ±20 %

5 10/350[B6](IEC)

Open-CircuitVoltage

See NOTE

Short-CircuitCurrent, Iimp

Waveform charge0.5*Iimp C –10 % to +20 %

±10 %

Waveform I2t0.25*(Iimp)2 A2s –10 % to +45 %.

NOTE—Voltage waveshape not defined. Usually the peak charging voltage for the specified

8/20 current value is given

A.4.3 Generators with defined voltage and current waveforms

The 1.2/50-8/20 generator #7 is commercially available and established in test laboratories. Although generator #8 might be referenced most people would use generator #7 for testing.

A similar situation exists for the 10/1000 impulse generators #11 and #12. Generator #11 is commercially available and established in test laboratories. Although generator #12 might be referenced most people would use generator #11 for testing.

For the 10/700 generators, #9 and #10, the choice is application dependent. For telecommunications applications the ITU-T generator #9 [B7] is the automatic choice and most commonly available both commercially and in test laboratories. General EMC work will often reference the IEC generator #10 [B10]. The IEC generator #10 is available commercially, but is possible to use the ITU-T generator with extra series resistors, see A.8.3.

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Table A.3—Voltage and Current Impulse GeneratorsNumber Designation Condition Edge Time and

ToleranceAmplitude

6 1.2/50-8/20(1.2/50-7.3/22)[B8] (IEEE)See NOTE 1

Open-CircuitVoltage

Front 1.2 µs ±30 % µs ±10 %Decay 50 µs ±20 %


Front 8 µs -31 % to +13 % ±10 % Decay 20 µs -20 % to +40 %

7 1.2/50-8/20[B9][B10](IEC/Telcordia)See NOTE 2

Open-CircuitVoltage

Front 1.2 µs ±30 % ±10 %Decay 50 µs ±20 %


Front 8 µs ±20 % ±10 % 0 to -30 % undershoot

Decay 20 µs ±20 %

8 <10/>250[B9](Telcordia)

Open-CircuitVoltage

Front 10 µs -60 % to 0 0% to +16%Decay 250 µs 0 to +60 %


Front 10 µs -30 % to 0 0% to +16%Decay 250 µs 0 to +20 %

9 10/700[B10](IEC)See NOTE 3

Open-CircuitVoltage

Front 10 µs ±30 % 0% to +15%Decay 700 µs ±20 %


Front 5 µs ±20 % 0% to +15%Decay 320µs ±20 %

10 10/700[B7][B3](ITU-T/IEC)See NOTE 4

Open-CircuitVoltage

Front 10 µs ±30 % ±10 %Decay 700 µs ±20 %


Front 5 µs ±20 % ±10 %Decay 320µs ±20 %

11 <10/>1000[B9](Telcordia)

Open-CircuitVoltage

Front 10 µs -40 % to 0 0 to +15 %Decay 1000 µs 0 to +50 %


Front 10 µs -40 % to 0 0 to +15 %Decay 1000 µs 0 to +50 %

12 10/1000[B8](IEEE)

Open-CircuitVoltage

Front 10 µs -50 % to 0 ±10 %Decay 1000 µs 0 to +100 %


Front 10 µs -50 % to 0 ±10 %Decay 1000 µs ±20 %

a) The #6 1.2/50-8/20 generator fictive impedance is 2 ±12.5 % [B8].

b) The #7 1.2/50-8/20 generator fictive impedance is 2 ±10 % [B10].

c) The #9 10/700 generator [B10] short-circuit current waveshape is 5/320 for single output and 5/320 for dual output. The dual output current tolerance is 5 µs ±20 % front, 320 µs ±20 % duration and

±10 % amplitude.

d) The #10 10/700 generator [B7] short-circuit current waveshape is 5/320 for single output and 4/250 for dual output. The dual output current tolerance is 4 µs ±20 % front, 250 µs ±20 % duration and±10 % amplitude.

A.5 Impulse generator circuits

A.5.1 RC half-value time waveshaping

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A.5.2 LRC half-value time waveshaping

A.6 Combination wave generators

Combination wave generators have significantly different open-circuit voltage and short-circuit current impulse waveshapes. Impulse generators with the same nominal open-circuit voltage and short-circuit current waveshapes have different voltage and current waveshape tolerances to compensate for the inherent change in waveshape in going from open- to short-circuit. If a combination wave generator isn’t given a waveshape designation it is assumed to be a 1.2/50-8/20 combination wave generator.

A.6.1 1.2/50-8/20 combination wave generator

In 1966, a group of engineers set out to characterize the surge environment of low voltage AC power circuits. The outcome in 1980 was the IEEE 587 standard. It was this standard that created the 1.2/50-8/20 combination wave generator. Combination means that the generator was formulated by combining the existing 1.2/50 voltage waveform, used for insulation testing, and the existing 8/20 current waveform, used for component testing. The research results set the generator to produce a 6 kV maximum (nominal) open-circuit 1.2/50 voltage and 3 kA short-circuit 8/20 current [B11].

The fictive impedance (peak open-circuit voltage divided by peak short-circuit current) of the 1.2/50-8/20 Combination wave generator is 2 . The 1.2/50-8/20 Combination wave generator is often used with external resistors to reduce the prospective current or share currents to multiple outputs. The prospective short circuit current is the defined by the voltage setting, the 2 fictive impedance and the external series resistance(s).

When connected to a resistive load, the actual load waveshape will depend on the value of resistance. A low value of resistance will result in an 8/20 waveshape and a high value of resistance will result in a 1.2/50 waveshape. Figure A.3 shows how the front time and half-value time typically varies with load resistance values in the 0 to 20 range.

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Figure A.3—1.2/50-8/20 Combination wave generator output waveshape variation with external resistance

Standard configurations [B10] use external current limiting resistor values of 10 and 40 . Into a short-circuit these resistive feeds will give waveshapes of 2.2/37 (10 ) and 1.3/51 (40 ). Table A.4 lists the Figure A.3 plot values together with peak current and I2t values.

If it was required to test with a voltage of 6 kV and a prospective current of 500 A, the external series resistor value would be 6000/500 – 2 (fictive) = 12 – 2 = 10 . From the 10 table row, the current waveshape would be 2.2/37 and the waveshape I2t would be 18.38*(6000/10000)2 = 6.6 A2s.

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Table A.4—1.2/50-8/20 generator output variation with external resistance RR

Front Time

s

Time tohalf-value

s

Normalized 10 kV voltage settingIPEAK I2t IPEAK

AI2t A2s

0 8.00 20 1 1.000 5000 305.001 6.21 22 0.6667 0.507 3333 154.542 5.08 24.2 0.5 0.325 2500 98.983 4.31 26.2 0.4 0.232 2000 70.914 3.75 28.1 0.3333 0.179 1667 54.555 3.33 29.8 0.2857 0.144 1429 43.856 3.01 31.4 0.25 0.116 1250 35.377 2.75 32.9 0.2222 0.096 1111 29.298 2.54 34.3 0.2 0.081 1000 24.739 2.37 35.5 0.1818 0.069 909 21.1510 2.23 36.7 0.1667 0.060 833 18.3812 2.01 38.8 0.1429 0.047 714 14.2714 1.86 40.6 0.125 0.037 625 11.4316 1.74 42.2 0.1111 0.031 556 9.3918 1.66 43.5 0.1 0.026 500 7.8420 1.59 44.6 0.0909 0.022 455 6.64

A.6.2 10/700-5/320 combination wave generator

Explain background and waveform variation

A.7 Expanding single output generators to multiple output

A.7.1 Current waveform generators

As these generators have defined a current waveform, the multiple output design will use the added series resistors to provide current sharing between the outputs. The operation of current source generators requires that the load voltage is relatively small compared with the generator charging voltage. The multiple output design must make the combined voltage of the surge protector in conduction and the current sharing resistor voltage drop much smaller than the generator charging voltage.

A.7.1.1 8/20 current generator

A.7.1.1.1 Resistor values

A.7.1.1.2 Surge Protector asynchronous operation

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A.7.2 Voltage and current waveform generators

As these generators have defined voltage and current waveforms, the multiple output design will use the added series resistors to both limit the peak current and provide current sharing between the outputs.

A.7.2.1 1.2/50-8/20 generator



A.7.2.2 <10/>250 generator

The most common requirement for this generator is a dual output variant. This design example is based on the coordination test clause 4.6.2.1.2.7 of [B9] which requires a minimum of 2x500 A into a protector-equipment combination developing a maximum voltage of 1000 V. The impulse generator voltage is stepped up until a current level of 500 A, or a voltage level of 1000 V or both is obtained.


The <10/>250 impulse generator has a peak open circuit voltage of 4000 V and a peak short-circuit current of 2000 A. The generator fictive resistance is 4000/2000 = 2 . The current drawn from the generator is 2x500 = 1000 A making the total circuit resistance (4000-1000)/1000 = 3 . Each series current sharing resistor will be 2x(3-2) = 2 . The operational aspects of the arrangement now need to be evaluated.

Figure A.4 shows the generator conditions for the design value dual 1000 V, 2x500 A (2x2 ) load and dual short-circuit load. With a dual short-circuit load the total current is 4/(2+2/2) = 1333 A = 2x667 A. The external 2 splitter resistors used should be capable of withstanding peak current levels of about 700 A.

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10/250 coordination generator at 4 kV with dual 1 kV load

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10/250 coordination generator at 4 kV with dual short-circuit output

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Figure A.4—<10/>250 generator coordination currents – figure needs work!


A surge protector that has independent switching operation of its overvoltage protection elements may result in one conductor being shorted before the other. The design should cause both overvoltage protection elements to operate, by generating sufficient voltage to operate the non-conducting overvoltage protection element. Figure A.5 shows this situation for 1000 V GDT overvoltage protection elements.

250 A

2

1 kV

10/250 coordination generator with asynchronous 1 kV GDT protectors

first protector just operated

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2 500 V

500 A

2

2 kV

10/250 coordination generator with asynchronous 1 kV GDT protectorssecond protector just about to operate

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2 1 kV

Figure A.5— Asynchronous primary protector operation – figure needs work!When the generator voltage is set to VL (1 kV), one GDT operates first. In operation the GDT conducts a current of 250 A and reduces the voltage of the other GDT to 500 V. Stepping up the generator voltage to 2 kV gives an un-operated GDT voltage of 1 kV with a current of 500 A in the operated GDT. The next small step increase in generator voltage will operate both GDTs.

Had a 3-electrode common-chamber GDT, been used rather than two 2-electrode GDTs, then operation of one side would have automatically caused operation of the other side, reducing the EUT metallic (transverse) stress level.

A.8 Generator variations

Anomalies occur due to the way in which different standards organizations define a certain waveshape generator. The two differences that can occur are due to tolerance values and current sharing resistances.

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Users need to be aware of which generator variant they have and if its performance will have an adverse effect on the testing.

A.8.1 8/20 current generator

There is a tolerance difference between a generator intended for arrestor testing and a more general purpose version.

A.8.2 10/1000 generator

In 1955, Bell Telephone Laboratories standardized on a 10/600 waveshape for protection testing [B12]. The recommendations of a 1961 Bell Laboratories field study report resulted in the adoption of a 10/1000 waveshape [B13] The chosen front time of 10 µs was less than 99.5 % of the recorded values and the chosen half-value time of 1000 µs was greater than 95 % of the recorded values.

The study covered five voice-grade trunk routes with a mixture of aerial and underground cabling. Measurements made on modern, short distance DSL-capable lines show front times in the microsecond region.

A Canadian Bell-Northern Research 1968-1969 field study [B14] studied three types of facility. The report suggested the following waveforms, 1000 V, 10/1000 to cover 99.8 % of all paired and coaxial cable lightning surges and 2000 V, 4/200 to cover 99.8 % of all open wire circuit lightning surges. The report showed an inverse correlation existed between the surge voltage and decay for higher level surges.

As a result of these recommendations the 1000 V, 100 A, <10/>1000 impulse was standardized on by Telecordia for many of its NEBS (Network Equipment - Building System) documents [B9]. This is the <10/>1000 generator #11 in Table A.3.

Generator #11 is different to the IEEE version [B8] of a 10/1000 generator listed #12 in Table A.3. The IEEE 10/1000 generator defines a 10/1000 waveform mostly based on nominal and not limit values. The Telcordia <10/>1000 generator delivers higher stress levels than the IEEE 10/1000 generator. Mixing up these two 10/1000 generator variants is unlikely as commercially available 10/1000 generators are based on the Telcordia (#11) variant. To enable the testing of common mode (longitudinal) coordination between surge protectors and equipment a dual output generator is available with independent outputs of 2 kV, 200A, <10/>1000.

A.8.3 10/700 generator

This is filler text

The “10/700” generator is circuit defined see Figure A.6. The ITU-T “Blue Book” extraction of ITU-T K.17 (1988) Tests on power-fed repeaters using solid-state devices in order to check the arrangements for protection from external interference had two generator circuit variants; 10/700 and 100/700. The different rise times, 10 µs and 100 µs, were obtained by changing value the of rise time controlling capacitor C2 from 200 nF to 2 µF. France favored a faster rise 0.5/700 generator using a C2 value of 20 nF.

The specification of the circuit-defined 10/700 generator output waveforms came later. The specified values depend on what standards body did the determination. ANSI/TIA-968-A (Part 68) gives voltage waveshape values of 9 µs (±30%) rise time and a 720 µs (±20%) decay time. IEC 61000-4-5 gives voltage waveshape values of 10 µs ±30 % rise time and a 700 µs ±20 % decay time.

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The current waveshape values are dependent on the number of outputs used. Only one output is used for transverse or metallic testing and both outputs are used for longitudinal testing. The short circuit current waveshape of a single output is 5/320 and for two outputs shorted is 4/250.

R4 = 25

R3 = 25 Vout1R2 = 15 S1

R1 = 50 C1 = 20 µF C2 = 200 nF

Vout2

Common

Figure A.6—10/700 generator circuit

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Annex B

(informative)

Bibliography

[B1] IEEE Std 4TM-1995, IEEE Standard Techniques for High Voltage Testing

[B2] IEC 60060-1 ed3.0 (2010-09) High-voltage test techniques – Part 1: General definitions and test requirements

[B3] IEC 60950-1 ed2.0 (2005-12) Information technology equipment - Safety - Part 1: General requirements, Annex N (normative) Impulse test generators

[B4] Recommendation ITU-T K.44 (04/2008) Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents – Basic Recommendation, Figure A.3-2

[B5] IEC 62475 ed1.0 (2010-09) High-current test techniques - Definitions and requirements for test currents and measuring systems

[B6] IEC 61643-11 ed1.0 (2011-03) Low-voltage surge protective devices - Part 11: Surge protective devices connected to low-voltage power systems - Requirements and test methods

[B7] Recommendation ITU-T K.44 (04/2008) Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents – Basic Recommendation, Figure A.3-1

[B8] C62.45-2002 IEEE Recommended Practice on Surge Testing for Equipment Connected to Low-Voltage (1000 V and Less) AC Power Circuits

[B9] GR-1089-CORE, Issue 6, Electromagnetic Compatibility and Electrical Safety - Generic Criteria for Network Telecommunications Equipment

[B10] EC 61000-4-5 ed2.0 (2005-11) Electromagnetic compatibility (EMC) - Part 4-5: Testing and measurement techniques - Surge immunity test

[B11] François D. Martzloff, A Standard for the 90s: IEEE C62.41 Surges Ahead, Compliance Engineering, Fall 1991

[B12] BODLE, D.W., GHAZI, A.J., SYED, M., and WOODSIDE, R.L., Characterization of the electrical environment, University of Toronto Press, 1976

[B13] D.W. Bodle and P.A. Gresh, “Lightning Surges in Paired Telephone Cable Facilities”, The Bell System Technical Journal, March, 1961

[B14] E. Bennison, A. Ghazi, P. Ferland, Lightning Surges in Open Wire, Coaxial, and Paired Cables, IEEE Transactions on Communications, Oct 1973, Volume: 21, Issue: 10, pp 1136- 1143

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