IEC 60243-3 pdf download

IEC 60243-3 pdf download Electrical strength of insulating materials — Test methods — Part 3: Additional requirements for 1,2/50 ? ?s impulse tests
Scope
This part of IEC 60243 gives requirements additional to those in lEC 60243-1 for thedetermination of the electric strength of solid insulating materials under 1,2/50 us impulsevoltage stress.
2 Normative references
The following normative documents contain provisions which,through reference in this text,constitute provisions of this part of lEC 60243.For dated references,subsequent amendmentsto,or revisions of，any of these publications do not apply. However parties to agreementsbased on this part of lEC 60243 are encouraged to investigate the possibility of applying themost recent editions of the normative documents indicated below.For undated references, thelatest edition of the normative document referred to applies. Members of the lEC and the lSomaintain registers of currently valid lnternational Standards.
IEC 60243-1:1998,Electrical strength of insulating materials – Test methods – Part 1:Tests atpower frequencies
3Definitions
For the purpose of this part of lEC 60243, the following definitions, together with those given inclause 2 of IEC 60243-1, apply.
3.1
full impulse-voltage wave (and see figure 1)
aperiodic transient voltage that rises rapidly to a maximum value, then falls less rapidly to zero
3.2
peak value (of an impulse-voltage wave), upmaximum value of voltage
3.3
virtual peak value (of an impulse-voltage wave),u.
value derived from a recording of an impulse-voltage wave on which high-frequencyoscillations, or overshoot of a limited magnitude, may be present
3.4
virtual origin (of an impulse-voltage wave)o1
point of intersection O with the line of zero voltage of a line drawn through the points of 0,3and 0,9 times the virtual peak value on the front of an impulse-voltage wave (see figure 1)
3.5
virtual front time (of an impulse-voltage wave) t
equal to 1,67 times the interval t between the instants when the voltage is 0,3 and 0,9 timesthe peak value (t, figure 1).
3.6
virtual time to half-value t2
time interval t, between the virtual origin Oand the instant on the tail when the voltage hasdecreased to half the peak value
4Significance of the test
ln addition to the information of clause 3 of lEC 60243-1, the following points are of importancein connection with impulse-voltage tests:
4.1High-voltage equipment may be subjected to transient voltage stresses resulting fromsuch causes as nearby lightning strokes. This is particularly true of apparatus such astransformers and switchgears used in electrical power transmission and distribution systems.The ability of insulating materials to withstand these transient voltages is important inestablishing the reliability of apparatus insulated with these materials.
4.2Transient voltages caused by lightning may be of either positive or negative polarity. In asymmetrical field between identical electrodes,the polarity has no effect on the electricstrength.However, with dissimilar electrodes, there may be a pronounced polarity effect. Whenassymetrical electrodes are used for testing materials with which the tester has no previousexperience or knowledge，it is recommended that comparative tests be made with bothdirections of polarity.