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UL 2556中對絕緣耐壓測試有三種方式.8 l& f+ S. o" U: v
6.2 Dielectric voltage-withstand
6 l4 Z' m7 t8 ^1 {9 _- _( B6.2.1 Scope
! _" I! T7 |6 I& pThis test establishes the methods for determining the dielectric voltage-withstand of a wire or cable.
, I* J8 P8 r F* J6 K6.2.2 Apparatus
' d6 w# n/ D. g* j: F, fThe apparatus shall consist of
- s# ^" j, H, Oa) an isolation transformer capable of supplying a test potential of 48 to 62 Hz, whose output( f8 \% ?: I# P/ e+ Y
potential is continuously variable from near zero to at least the specified rms test potential;0 D4 k5 k c; D8 i) j+ f' B
b) a voltmeter having an accuracy of ±5%, on the high voltage side of the transformer. If- X5 F8 _$ k5 p6 b `' u
analog, it shall have a response time that does not introduce a lagging error greater than 1% of
( d* s; J6 U* Q6 ufull scale at the specified rate of increase in voltage;
, e7 f. n( Q+ S& mc) a fault current indicator;
. t8 Q; h7 V' ^/ d+ X* C3 A/ Id) a forced-air oven as described in Clause 4.2.3 Item (i), having insulated bushings for
# k0 w5 l, _8 v4 A! L. v7 Fconnection of the test voltage while the oven is closed;
2 [5 T" E+ k" j" G" De) a temperature-measuring device with an accuracy of ±1 °C;% o# k5 w: F! u$ g; }
f) a tank filled with tap water; and: ~# C3 h. ?+ d* e9 [! I4 T' j
g) a means of grounding, maximum impedance of 15W." _) y9 Y' ?4 [1 E
6.2.3 Preparation of specimens
/ B! P7 m2 j& R2 T7 H6.2.3.1 Method 1 (in water)2 O: L' I; @' t$ a% Z
Both ends of the individual conductors shall be made bare.
) {$ @( |- k) _- Z' V }In preparing the wire for test, each end of the specimen shall be brought out well above the water level
" S7 m( |5 p# f% E( ~in the tank, where applicable, and the covering removed from the surface of the insulation for a short' G" E! Y4 O. ]# t9 d/ q$ {4 r
distance if necessary to prevent surface leakage. The temperature of the water in which the specimen is
5 _, x6 s) H v( O+ M( P3 v1 @- Fimmersed need not be controlled unless specified in the product standard.$ g* q% s- c) Y0 k
Unless specifically required by the product standard, a shielded or metal-covered single-conductor/ q; i' k7 U( P1 j, [" ^7 {
specimen need not be immersed in water, the test voltage being applied between the conductor and the
" O& q, h; {" f/ T( {( O+ y( mshield or metal covering.' H& m8 g/ ], N" p5 n" m/ x8 S
Unless specifically required by the product standard, a multiconductor cable need not be immersed in
2 H4 b6 @" X' nwater, the test voltage being applied between each conductor and the electrode, consisting of all other
: Z2 i; \3 I s2 M' P( Zconductors connected together and to all shields and metal coverings, as applicable.6 T, _4 [8 q! X2 |9 q1 P
In all cases, the ends of the conductor of the specimen shall be spaced from the grounded electrode a0 d5 m m7 _. M$ l0 ^9 {- v) E; `* u6 n
sufficient distance to prevent corona or flashover at the ends during application of the test voltage.
9 m( C2 \( v0 i r6.2.3.2 Method 2 (in air)
$ N, J0 p/ e, `$ XBoth ends of the individual conductors shall be made bare.: Z0 {2 v6 {( S5 a. _
For a single-conductor cable, a grounding electrode, when not present as a component, shall be applied.
: N- ]" _- [4 f' H( q, JA snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable.
/ w4 K2 P, ~1 O% \: s6 V! q. A4 s6.2.3.3 Method 3 (in air at elevated temperature)
, q9 P( d2 B k! K+ M3 [4 J/ t* L- _Both ends of the individual conductors shall be made bare.
8 D# E9 a l" \ g+ [% Z! NFor a single-conductor cable, a grounding electrode, when not present as a component shall be applied.
1 j0 S: V7 o4 u4 E: b' P! C, m8 O: jA snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable. |
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