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UL 2556中對絕緣耐壓測試有三種方式.
3 Z, p+ I6 K$ V8 z4 k& y7 w6.2 Dielectric voltage-withstand
& Z& u6 s, p+ e8 B; m# p6.2.1 Scope9 I' v( @- v* F- C
This test establishes the methods for determining the dielectric voltage-withstand of a wire or cable.* Z# P2 j# S/ Z% h% P
6.2.2 Apparatus
4 V9 J( b7 o$ l" ]& K, aThe apparatus shall consist of
2 @4 }7 y6 L8 X+ e; B6 M. W2 z$ Ha) an isolation transformer capable of supplying a test potential of 48 to 62 Hz, whose output7 \$ O( u. ?$ ?8 y7 h
potential is continuously variable from near zero to at least the specified rms test potential;2 M; h7 p, C, B+ p8 B/ B
b) a voltmeter having an accuracy of ±5%, on the high voltage side of the transformer. If
0 ^2 `( b x# {analog, it shall have a response time that does not introduce a lagging error greater than 1% of. Q* W! v2 i! t, L5 j6 J! Q \5 p
full scale at the specified rate of increase in voltage;' {5 ~9 M8 ]3 W2 c" D
c) a fault current indicator;5 c& y& b0 a" j) g
d) a forced-air oven as described in Clause 4.2.3 Item (i), having insulated bushings for( ^+ q* n: k5 b! O
connection of the test voltage while the oven is closed;
" u3 D8 C% c. ~4 Ae) a temperature-measuring device with an accuracy of ±1 °C;+ y& W d" G7 [' d3 D$ G
f) a tank filled with tap water; and! w5 ^+ L. `3 u: b9 E4 r
g) a means of grounding, maximum impedance of 15W.
* f3 I+ U! w7 P0 V; v0 ^6.2.3 Preparation of specimens
- p8 U5 t4 ^, m* _! n' l4 E! F6.2.3.1 Method 1 (in water)
1 h; j5 t H. @( N' G) N3 xBoth ends of the individual conductors shall be made bare.
6 c( i7 L" Q! ]5 c8 {7 s+ @In preparing the wire for test, each end of the specimen shall be brought out well above the water level
& }- R# R: Q+ r8 [5 oin the tank, where applicable, and the covering removed from the surface of the insulation for a short/ I3 T n: q! R" v. d0 \* R
distance if necessary to prevent surface leakage. The temperature of the water in which the specimen is
$ T/ x4 J- b J( F4 m, P. L, Iimmersed need not be controlled unless specified in the product standard.7 l* `' ^6 r. ~3 C5 ?& y8 m
Unless specifically required by the product standard, a shielded or metal-covered single-conductor
. F- n) F0 K: E7 a) d& a$ T& Lspecimen need not be immersed in water, the test voltage being applied between the conductor and the) P% U8 s5 ], ` u/ ~+ U" q. _
shield or metal covering./ ?! N: P7 ]0 z8 d* h: }/ |
Unless specifically required by the product standard, a multiconductor cable need not be immersed in
2 F C0 l" c$ D K) C: S! F& hwater, the test voltage being applied between each conductor and the electrode, consisting of all other! B+ L( ~+ L3 }$ q4 C( M
conductors connected together and to all shields and metal coverings, as applicable.
0 f+ n3 w+ W o4 N+ G9 e: J+ ~In all cases, the ends of the conductor of the specimen shall be spaced from the grounded electrode a
2 C" z! X0 u \& ysufficient distance to prevent corona or flashover at the ends during application of the test voltage.2 x1 p) K) ^9 z. m, q
6.2.3.2 Method 2 (in air)
% l6 D$ H7 [. RBoth ends of the individual conductors shall be made bare.
0 k% a( z. w! @2 Q6 PFor a single-conductor cable, a grounding electrode, when not present as a component, shall be applied.
* D! L6 U6 n3 SA snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable.( C, u* e6 |# y# {7 w# M3 g
6.2.3.3 Method 3 (in air at elevated temperature)
, P3 {+ l- F5 rBoth ends of the individual conductors shall be made bare.
5 T1 q+ }2 f" r1 A7 WFor a single-conductor cable, a grounding electrode, when not present as a component shall be applied.
4 h) r, g l' \+ Z! E2 x) T! A B* dA snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable. |
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