電纜的額定電壓應(yīng)適合于電纜系統(tǒng)的運(yùn)行狀況，用U0/U
（Um）kV 表示。
U0—電纜設(shè)計(jì)用的導(dǎo)體對(duì)地或金屬屏蔽之間的額定工頻電
壓；
U—電纜設(shè)計(jì)用的導(dǎo)體間的額定工頻電壓；電機(jī)引接線，交聯(lián)電纜
Um—設(shè)備可承受的“zui高系統(tǒng)電壓”的zui大值。
The rated voltage of the cable for a given application shall be suitable for
the operating conditions in the system in which the cable is used,and is
expressed in the form of U0/U（Um）kV. Where:
U0—The rated power-frequency voltage between conductor and earth
or metallic screen,for which the cable designed；
U—The rated power-frequency voltage between conductors,for which
the cable disigned；
Um—The maximum value of the “highest system voltage”for which
the equipment may be used.
U
kV
Um
kV
U0*kV
A 和B 類系統(tǒng)
Syetem categories A and B
C 類系統(tǒng)
Syetem categories C
6 7.2 3.6 6
10 12 6 8.7
15 17.5 8.7 12
20 24 12 18
30 36 18 -
35 40.5 21 26A 類系統(tǒng)—該類系統(tǒng)任何一相導(dǎo)體與地或接地導(dǎo)體接觸時(shí)，能
在1min 內(nèi)與系統(tǒng)分離；
B 類系統(tǒng)—該類系統(tǒng)僅包括單相接地故障短路時(shí)運(yùn)行的條件，
接地故障時(shí)間應(yīng)不超過1h，但在任何情況下，zui長(zhǎng)不超過8h，
每年接地故障總持續(xù)時(shí)間不超過125h；
C 類系統(tǒng)—不屬于A 類、B 類的系統(tǒng)。
System category A—This category comprises those systems in which any phase
conductor that comes in contact with earth or an earth conductor,is disconnected
from the system
with in 1 min.
System category B—This category comprises those system which,under fault
conditions,are operated for a short time with one phase earthed.This period should
not exceed 1 h.For a longer period,not exceeding 8 h on any occasion,can be
tolerated.The total duration of earth faults in any year should not exceed 125 h.
System category C—This category comprises all syatems which do not fall into
categories A and B.
電纜額定電壓的選擇Voltage designation
三相系統(tǒng)用電纜的U0 值推薦如下表：The values of U0 recommened for cables to be used in three-phase systems are listed below.
電纜的額定電壓應(yīng)適合于電纜系統(tǒng)的運(yùn)行狀況，用U0/U
（Um）kV 表示。
U0—電纜設(shè)計(jì)用的導(dǎo)體對(duì)地或金屬屏蔽之間的額定工頻電
壓；
U—電纜設(shè)計(jì)用的導(dǎo)體間的額定工頻電壓；
Um—設(shè)備可承受的“zui高系統(tǒng)電壓”的zui大值。
The rated voltage of the cable for a given application shall be suitable for
the operating conditions in the system in which the cable is used,and is
expressed in the form of U0/U（Um）kV. Where:
U0—The rated power-frequency voltage between conductor and earth
or metallic screen,for which the cable designed；
U—The rated power-frequency voltage between conductors,for which
the cable disigned；
Um—The maximum value of the “highest system voltage”for which
the equipment may be used.
U
kV
Um
kV
U0*kV
A 和B 類系統(tǒng)
Syetem categories A and B
C 類系統(tǒng)
Syetem categories C
6 7.2 3.6 6
10 12 6 8.7
15 17.5 8.7 12
20 24 12 18
30 36 18 -
35 40.5 21