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UL 2556中對絕緣耐壓測試有三種方式.* u. y I* P3 ~
6.2 Dielectric voltage-withstand/ Y( e; l. H& T" |
6.2.1 Scope6 G* M! M$ W4 f, a! x- m
This test establishes the methods for determining the dielectric voltage-withstand of a wire or cable.
, V# K1 U/ U& s5 A6.2.2 Apparatus
, H7 ]4 I, x* `- T; f6 NThe apparatus shall consist of+ ^' n. e2 f! _# X
a) an isolation transformer capable of supplying a test potential of 48 to 62 Hz, whose output5 b4 p/ u# f) ]
potential is continuously variable from near zero to at least the specified rms test potential;0 E; b# W; p5 P
b) a voltmeter having an accuracy of ±5%, on the high voltage side of the transformer. If
, O& r% F% u0 ]2 M: O% s" J7 {2 ^: O8 Q- zanalog, it shall have a response time that does not introduce a lagging error greater than 1% of
& H1 k+ F+ Z4 k# ^& [- Y! gfull scale at the specified rate of increase in voltage;3 W9 Z r7 b$ E8 f" a) B
c) a fault current indicator; m' P# l- y( X5 m* H& E
d) a forced-air oven as described in Clause 4.2.3 Item (i), having insulated bushings for
@2 O* L- S" s2 u$ [connection of the test voltage while the oven is closed;
0 [0 c2 j* T6 ^6 U4 R% w- Re) a temperature-measuring device with an accuracy of ±1 °C;3 s) E) N: D% A: _* ^/ l
f) a tank filled with tap water; and
+ Z | r, {8 yg) a means of grounding, maximum impedance of 15W.' ^' t2 L2 i" a8 |" J
6.2.3 Preparation of specimens4 k3 d4 n* \( W& E* H
6.2.3.1 Method 1 (in water)4 D( P3 {% [2 J) i
Both ends of the individual conductors shall be made bare. O9 e7 D" _4 N
In preparing the wire for test, each end of the specimen shall be brought out well above the water level9 N8 T; U9 I$ I! e
in the tank, where applicable, and the covering removed from the surface of the insulation for a short. t- A' q$ b* M1 T7 L4 J
distance if necessary to prevent surface leakage. The temperature of the water in which the specimen is
4 Y' F' T: }4 H* k* p: ~immersed need not be controlled unless specified in the product standard.
! k# l0 Q1 [' q% fUnless specifically required by the product standard, a shielded or metal-covered single-conductor
6 e2 [ y5 S0 ], a& t- {' Tspecimen need not be immersed in water, the test voltage being applied between the conductor and the
- F0 P5 t6 S$ r) c8 A$ Hshield or metal covering.9 _- K, n+ q) B% P1 T7 N7 Q8 c
Unless specifically required by the product standard, a multiconductor cable need not be immersed in7 B. t/ ^! I s7 q
water, the test voltage being applied between each conductor and the electrode, consisting of all other
- T" q4 d# L7 P$ z0 gconductors connected together and to all shields and metal coverings, as applicable.
- R4 ?) g) a. e2 K1 W3 V6 ~In all cases, the ends of the conductor of the specimen shall be spaced from the grounded electrode a8 t3 M- [' J% b2 Q- J3 F' ~3 W
sufficient distance to prevent corona or flashover at the ends during application of the test voltage.& I- P) j; L) Z9 i% x E/ l4 k3 I
6.2.3.2 Method 2 (in air)
6 }5 ~' i2 P' I3 q5 J5 G5 |Both ends of the individual conductors shall be made bare." i4 i; x* O: L. G* m3 |
For a single-conductor cable, a grounding electrode, when not present as a component, shall be applied.% X2 b, K9 u5 c) ^" R: [
A snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable./ z: J6 @$ m3 {( C
6.2.3.3 Method 3 (in air at elevated temperature)1 `# |6 k, V: J( ` s. l( W
Both ends of the individual conductors shall be made bare.8 \/ i; a, g" y& C/ t* I' j8 @
For a single-conductor cable, a grounding electrode, when not present as a component shall be applied.6 |5 L3 }) \, }! z; o
A snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable. |
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