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UL 2556中對絕緣耐壓測試有三種方式., Z3 `) f1 A2 Z
6.2 Dielectric voltage-withstand2 E5 K* j# C1 E3 ]
6.2.1 Scope( z' |, }5 z6 [* q
This test establishes the methods for determining the dielectric voltage-withstand of a wire or cable.! K3 t6 }! z& q9 j6 X# e
6.2.2 Apparatus. R6 D: I( X3 k1 E- T1 t
The apparatus shall consist of
4 q9 g- P: O: }; J0 Na) an isolation transformer capable of supplying a test potential of 48 to 62 Hz, whose output
) L* W: D' h$ J" a, ]! v) ~potential is continuously variable from near zero to at least the specified rms test potential;
- Q2 W* ~" t3 Z& H& J. {4 X4 I, vb) a voltmeter having an accuracy of ±5%, on the high voltage side of the transformer. If
# T9 U- \) U/ v' m& N7 _, R& G9 {analog, it shall have a response time that does not introduce a lagging error greater than 1% of
6 I8 \' k- Z( x# |! {) {full scale at the specified rate of increase in voltage;3 |( F7 s3 M B" s& v% F
c) a fault current indicator;
- K7 ?) o3 F/ L2 T0 ?& c2 R. W, _d) a forced-air oven as described in Clause 4.2.3 Item (i), having insulated bushings for
9 ^* v q7 F [2 `connection of the test voltage while the oven is closed;
* ~$ _* J( X9 A* D7 Re) a temperature-measuring device with an accuracy of ±1 °C;$ B7 P* H. O, U
f) a tank filled with tap water; and8 H( \% c* }7 v& \( A P
g) a means of grounding, maximum impedance of 15W.
4 j4 l) R' w2 q; ] D4 |6.2.3 Preparation of specimens- j" x# V; q8 h0 C4 T( Y$ `
6.2.3.1 Method 1 (in water)7 @$ R" J% e9 B& f/ Y8 j! w- U; a
Both ends of the individual conductors shall be made bare.
+ U2 ~ \6 h/ s$ GIn preparing the wire for test, each end of the specimen shall be brought out well above the water level
3 k8 `7 x: o/ uin the tank, where applicable, and the covering removed from the surface of the insulation for a short2 ]$ G* d' s$ N w9 i+ a
distance if necessary to prevent surface leakage. The temperature of the water in which the specimen is
' B h' i# Y" e+ limmersed need not be controlled unless specified in the product standard.$ [5 b v* c4 g( |
Unless specifically required by the product standard, a shielded or metal-covered single-conductor
& W) \* [1 K: }2 J* j2 g- ?specimen need not be immersed in water, the test voltage being applied between the conductor and the
3 r( f( Q' g- V$ s' qshield or metal covering.+ {- f) y! A3 k' ^# i5 W9 V
Unless specifically required by the product standard, a multiconductor cable need not be immersed in
6 Z4 W5 z! \2 S) V! l$ ]water, the test voltage being applied between each conductor and the electrode, consisting of all other
9 V! R: e' Z/ k! Gconductors connected together and to all shields and metal coverings, as applicable.+ q, T1 m0 l0 ^1 C
In all cases, the ends of the conductor of the specimen shall be spaced from the grounded electrode a
+ C: K7 ?8 x5 B+ j" v2 W9 l' Esufficient distance to prevent corona or flashover at the ends during application of the test voltage.- c( P' U, q; g* ~. Q: s
6.2.3.2 Method 2 (in air)2 m4 z9 v0 n5 q M# x; P
Both ends of the individual conductors shall be made bare.; h- X& w; |& \0 t/ w9 h
For a single-conductor cable, a grounding electrode, when not present as a component, shall be applied.
; r: m$ M/ c' h! DA snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable.
" B! v; y5 g+ p E" m! ]6.2.3.3 Method 3 (in air at elevated temperature)5 T8 B/ W& d3 Y' x
Both ends of the individual conductors shall be made bare.* ?! F; k# q) z9 H9 \& n7 ^$ }" z
For a single-conductor cable, a grounding electrode, when not present as a component shall be applied.! ^! K( B8 Q l, ~8 W' _3 @
A snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable. |
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