"UL 840-2016.pdf: 最新电气设备绝缘协调标准"

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UL 840-2016.pdf is the latest complete standard for insulation coordination, including clearances and creepage distances for electrical equipment. This standard, developed and copyrighted by UL, is essential for ensuring the safety and performance of electrical equipment in various applications. The standard outlines specific requirements and guidelines for insulation coordination, which is crucial for preventing electrical breakdowns and ensuring proper functioning of electrical equipment. It includes detailed information on clearances and creepage distances, which are important factors in preventing electrical arcing and maintaining safe operation. UL 840-2016.pdf is a comprehensive document that provides valuable insights into insulation coordination and is an essential reference for manufacturers, engineers, and professionals in the electrical industry. It is a copyrighted material, and reproduction or distribution without permission from UL is not authorized. Overall, UL 840-2016.pdf is a vital standard that plays a significant role in ensuring the safety and reliability of electrical equipment. Its guidelines and requirements are fundamental in the design, testing, and certification of electrical products, ultimately contributing to the overall safety and performance of electrical systems.

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INTRODUCTION

1 Scope

1.1 These requirements cover an alternate approach to specifying through air and over surface spacings

for electrical equipment through the use of the principles of insulation coordination.

1.2 The complete principles of insulation coordination involve the consideration of the combination of

clearances, creepage distances, and the properties of solid insulation used to constitute the insulation

system. The empirical data gathered thus far has been used to develop the requirements for clearances

and creepage distances as presented in this standard. The data needed to develop the evaluation

procedure for solid insulation is still being gathered. When available, this evaluation procedure will be

added to this standard and is not expected to affect the requirements for clearances and creepage

distances.

1.3 These requirements may be used as an alternate to required spacing levels speciﬁed in end-product

standards. The end product standard spacing requirements may be based on use and systems where

overvoltages are not controlled, or if controlled, the level of control is unknown.

1.4 These alternate requirements are intended to be applied to a particular product category if the

standard covering the product category speciﬁcally references UL 840 or any of the requirements therein.

1.5 Users of these requirements may need to specify the overvoltage levels and the methods of control

which will be utilized, and establish the pollution degree to which the product insulation system will be

expected to be subjected.

1.6 It is not intended that the test values in this standard be employed for production line testing.

However, users of these requirements will need to establish a means to ensure that production controls

applied to permit the spacing reduction remain in effect during the manufacture of the product. This could

include sample testing or physical measurements or another equivalent means.

1.7 Users of these requirements will additionally need to ensure that inﬂuencing factors not addressed in

this standard, such as mechanical movement, ﬁeld placement of conductive material, and product

damage, will not affect the system for insulation coordination. Examples are the deformation of the

enclosure, movement of the ﬁttings for conduit or armored cable, or the improper installation of ﬁeld wiring.

Clearances and creepage distances at those locations must be veriﬁed for compliance by physical

measurement in accordance with Section 10, Measurement of Clearance and Creepage Distances.

JANUARY 6, 2005UL 8404

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UL COPYRIGHTED MATERIAL –

NOT AUTHORIZED FOR FURTHER REPRODUCTION OR

DISTRIBUTION WITHOUT PERMISSION FROM UL

2 Glossary

2.1 For the purpose of this standard, the following deﬁnitions apply.

2.2 CLEARANCES – Through air spacing.

2.2A COMBINATION WAVEFORM – A surge delivered by a generator which has the inherent

capability of applying a 1.2/50 µs voltage wave across an open circuit, and delivering an 8/20 µs current

wave into a short circuit. Also called a combination surge.

2.2A added May 4, 2012

2.3 CREEPAGE DISTANCES (CREEPAGES) – Over surface spacings.

2.4 FUNCTIONAL OVERVOLTAGE – Deliberately imposed transient overvoltages necessary for the

function of a device.

2.5 GENERAL ENVIRONMENT – The overall area or space in which the equipment is located.

Commonly referred to as ambient conditions.

2.6 IMPULSE WITHSTAND VOLTAGE – The highest peak value of impulse voltages, of prescribed

form and polarity, that does not cause breakdown under speciﬁed conditions of test.

2.7 INSULATION COORDINATION – The correlation of insulating characteristics of electrical

equipment:

a) With expected overvoltages and characteristics of overvoltage protective devices (a key

consideration for clearances); and

b) With the expected micro-environment and pollution protective means (key considerations for

creepage distances).

2.8 LEAKAGE CURRENT – The current that can be measured as ﬂowing between test points during a

dielectric voltage-withstand test.

2.9 LIGHTNING OVERVOLTAGE – The transient overvoltage at a given location on a system due to a

speciﬁc lightning discharge.

2.10 MICRO-ENVIRONMENT – The conditions that immediately surround the clearance or creepage

distance under consideration. The micro-environment of the creepage distance or clearance and not the

general environment of the equipment determines the effect on the insulation. The micro-environment

might be less severe or more severe than the general environment that the equipment is in. It includes

all factors inﬂuencing the insulation, such as climatic, electromagnetic, and generation of pollution.

2.10A NOMINAL DISCHARGE CURRENT (In) – Peak value of the current, selected by the

manufacturer, through the SPD having a current waveshape of 8/20 where the SPD remains functional

after 15 surges.

2.10A added May 4, 2012

2.11 OPERATING VOLTAGE – The voltage across two points occurring due to normal operation of

the product when controls are set in any position.

MAY 4, 2012 UL 840 5

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