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UL 2556中對絕緣耐壓測試有三種方式.
8 c6 h- o- Q/ C& a6.2 Dielectric voltage-withstand. e& Q& O# o1 S& t
6.2.1 Scope0 a; j4 O$ V& Q7 U, N% L! k
This test establishes the methods for determining the dielectric voltage-withstand of a wire or cable.+ F( C( n- C# V% Q4 B9 Z
6.2.2 Apparatus m) u2 G* I4 x! M
The apparatus shall consist of
6 T8 O* a0 y+ @+ p; da) an isolation transformer capable of supplying a test potential of 48 to 62 Hz, whose output8 f+ @; S8 i( _/ J* }) f6 u- ^; I
potential is continuously variable from near zero to at least the specified rms test potential;) n; }6 Z$ c3 L3 h; E& U% ^9 C0 b
b) a voltmeter having an accuracy of ±5%, on the high voltage side of the transformer. If
, ^1 j1 p" \9 M, L, panalog, it shall have a response time that does not introduce a lagging error greater than 1% of2 m. h# T6 l G+ e( p
full scale at the specified rate of increase in voltage;' }' I7 f" W) Y$ m2 @9 f; `
c) a fault current indicator;
# a4 B/ E- v- Md) a forced-air oven as described in Clause 4.2.3 Item (i), having insulated bushings for
6 E- b6 h) P3 S, x+ I! d/ C! uconnection of the test voltage while the oven is closed;
+ f4 v, i. }& L X2 ce) a temperature-measuring device with an accuracy of ±1 °C;; M" D) c' C4 X/ g, v0 t
f) a tank filled with tap water; and
" }& o/ i( v5 K3 B) i |g) a means of grounding, maximum impedance of 15W.
* q$ {) v0 O1 l9 S, _5 E6.2.3 Preparation of specimens
6 n' \5 z5 `% n" ~6.2.3.1 Method 1 (in water)1 J! h t* Q* {
Both ends of the individual conductors shall be made bare.% S0 ^) N6 X3 X& q$ t+ _: S
In preparing the wire for test, each end of the specimen shall be brought out well above the water level
. W4 r8 E6 j' Din the tank, where applicable, and the covering removed from the surface of the insulation for a short( J* _+ {: p$ Q2 V# ^
distance if necessary to prevent surface leakage. The temperature of the water in which the specimen is( Q( {3 M. Y/ M6 I3 s" I3 J! x t
immersed need not be controlled unless specified in the product standard.
, w) H0 h* f6 ZUnless specifically required by the product standard, a shielded or metal-covered single-conductor
o: v! B' L9 gspecimen need not be immersed in water, the test voltage being applied between the conductor and the+ f( r' g W* z- O. g- d! l
shield or metal covering.
$ m- \& Y' _9 V; y. F8 q. iUnless specifically required by the product standard, a multiconductor cable need not be immersed in
0 Z# ?: D& n+ o5 z6 Rwater, the test voltage being applied between each conductor and the electrode, consisting of all other
: w ?" ?( | F. K y. \9 M0 n/ aconductors connected together and to all shields and metal coverings, as applicable.. W5 C: d% Y0 \7 e$ B$ z
In all cases, the ends of the conductor of the specimen shall be spaced from the grounded electrode a+ b1 c3 Y0 ~ l* S/ V7 v! b+ Q
sufficient distance to prevent corona or flashover at the ends during application of the test voltage.7 D1 r2 d9 ~9 W$ e* O7 ]
6.2.3.2 Method 2 (in air)% D% y5 K( C/ @! D( ]- n
Both ends of the individual conductors shall be made bare.5 P" h c) Q9 L
For a single-conductor cable, a grounding electrode, when not present as a component, shall be applied.- x4 e9 {4 g0 n; r; S
A snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable.8 W, M9 f# E3 m$ E" l( O9 I0 T
6.2.3.3 Method 3 (in air at elevated temperature)
d6 l6 L$ Q9 CBoth ends of the individual conductors shall be made bare.7 c4 ~ h: y& I( u- X; @9 e& y% k
For a single-conductor cable, a grounding electrode, when not present as a component shall be applied.2 ~5 g" v1 |! `$ `+ j1 Q, }. d8 S
A snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable. |
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