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UL 2556中對絕緣耐壓測試有三種方式.! |* r2 ?! A! w+ }! O
6.2 Dielectric voltage-withstand
) |- N/ h7 R3 l6.2.1 Scope5 ~6 R1 d4 s* L5 Y4 L7 x
This test establishes the methods for determining the dielectric voltage-withstand of a wire or cable.! z# M* t8 r/ @+ j6 D- F# H
6.2.2 Apparatus
" f1 U3 G) k8 Z( E2 S/ kThe apparatus shall consist of9 [1 W' Y( r; x5 e: G4 S( o8 ?
a) an isolation transformer capable of supplying a test potential of 48 to 62 Hz, whose output, I0 h6 _4 l4 B
potential is continuously variable from near zero to at least the specified rms test potential;
! J L1 N+ n( c, ab) a voltmeter having an accuracy of ±5%, on the high voltage side of the transformer. If
R* m! O( V5 w( b' \+ ?" tanalog, it shall have a response time that does not introduce a lagging error greater than 1% of
! m& F1 q5 v4 Yfull scale at the specified rate of increase in voltage; ~7 w3 z8 a9 |
c) a fault current indicator;
8 i! Z, C2 R- p% L6 |1 \" Xd) a forced-air oven as described in Clause 4.2.3 Item (i), having insulated bushings for
! \& g- Z8 i4 i9 V1 e' mconnection of the test voltage while the oven is closed;9 g. ?6 A/ g b( b8 l0 J) S
e) a temperature-measuring device with an accuracy of ±1 °C;3 X& P% m" V0 e: G3 r9 l
f) a tank filled with tap water; and; J- X1 y- x( X
g) a means of grounding, maximum impedance of 15W.
- `) q8 r! |% i9 P7 Z Y1 q1 g1 I! E6.2.3 Preparation of specimens' s: |' ?1 |; ]$ v- [
6.2.3.1 Method 1 (in water)1 s! k/ r6 F7 b' |" z
Both ends of the individual conductors shall be made bare.
: [+ L7 x. ^6 b9 {3 L4 T( P: eIn preparing the wire for test, each end of the specimen shall be brought out well above the water level9 @) W* Y( q V6 [
in the tank, where applicable, and the covering removed from the surface of the insulation for a short
! p+ r8 T: o; pdistance if necessary to prevent surface leakage. The temperature of the water in which the specimen is
: b2 Y# ?# M: J. Ximmersed need not be controlled unless specified in the product standard.
& Q i, b" R) UUnless specifically required by the product standard, a shielded or metal-covered single-conductor
! `4 Z$ _$ f+ n' u& B0 }specimen need not be immersed in water, the test voltage being applied between the conductor and the1 ^, A7 ^4 @: e0 j$ m( p
shield or metal covering., _6 |/ w% I& ]0 }) s
Unless specifically required by the product standard, a multiconductor cable need not be immersed in
$ c6 ]; I- p0 z6 n0 Q& Zwater, the test voltage being applied between each conductor and the electrode, consisting of all other& u3 R" W: F+ Y0 k, ?2 j
conductors connected together and to all shields and metal coverings, as applicable.! [$ h+ f3 ?8 o. t6 [
In all cases, the ends of the conductor of the specimen shall be spaced from the grounded electrode a) V9 g/ f. W4 h" v
sufficient distance to prevent corona or flashover at the ends during application of the test voltage.
R, ^: T- |1 K9 [( s9 p6.2.3.2 Method 2 (in air)
3 k, T6 l9 G4 H' I: `" _9 r0 PBoth ends of the individual conductors shall be made bare.! [6 T2 Y2 B% e3 {1 N" F
For a single-conductor cable, a grounding electrode, when not present as a component, shall be applied.
- m5 S1 |' Z+ W6 A. o5 |" OA snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable.( Q2 E6 a4 K7 Q$ D2 x
6.2.3.3 Method 3 (in air at elevated temperature)* Z/ z( V+ ~; c8 Y% d( V5 J: n
Both ends of the individual conductors shall be made bare.7 r1 ^. @6 q- |/ O4 m ^- Q
For a single-conductor cable, a grounding electrode, when not present as a component shall be applied.
' ?" O/ |1 ?- h* z2 g3 S. g6 N8 e2 SA snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable. |
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