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UL 2556中對絕緣耐壓測試有三種方式.* G$ l J9 m0 b
6.2 Dielectric voltage-withstand
9 Y4 Y: Q2 y# H5 F6.2.1 Scope
5 d# Y/ q# l3 Z4 RThis test establishes the methods for determining the dielectric voltage-withstand of a wire or cable.- P: ?( o/ o1 [
6.2.2 Apparatus. Y3 D- u& O& W5 }
The apparatus shall consist of
9 a2 F# I5 w/ }6 G# A# U1 Ca) an isolation transformer capable of supplying a test potential of 48 to 62 Hz, whose output
5 m6 `, W9 C( S+ ~ l$ `5 Ipotential is continuously variable from near zero to at least the specified rms test potential;
' a) o& ^( j. G( Ab) a voltmeter having an accuracy of ±5%, on the high voltage side of the transformer. If7 A0 E" W; ?5 d# u. y
analog, it shall have a response time that does not introduce a lagging error greater than 1% of
* R' S r* S9 o& A/ d0 o+ S5 Nfull scale at the specified rate of increase in voltage;6 }4 s' C7 i5 b
c) a fault current indicator;
8 z# k! ]: t% S3 s( Dd) a forced-air oven as described in Clause 4.2.3 Item (i), having insulated bushings for
9 X+ n) J1 _- l7 C2 Iconnection of the test voltage while the oven is closed;# h; K5 N. m) ~; N2 W& R6 B
e) a temperature-measuring device with an accuracy of ±1 °C;
* e% v& V/ S6 w7 x1 P0 f1 E0 bf) a tank filled with tap water; and
5 o" G0 y) u0 g+ i+ qg) a means of grounding, maximum impedance of 15W." J( o) p# X f# n7 f. |
6.2.3 Preparation of specimens9 h% j: C* @" b9 [/ ~6 N
6.2.3.1 Method 1 (in water) U; D5 N' w1 K+ o' X+ p
Both ends of the individual conductors shall be made bare.
. [( G/ x8 ^) C s& J* I, L* HIn preparing the wire for test, each end of the specimen shall be brought out well above the water level
8 ?& I. d4 ]2 E. e3 M; Vin the tank, where applicable, and the covering removed from the surface of the insulation for a short
) x, {0 }, G: P& l2 w1 P- bdistance if necessary to prevent surface leakage. The temperature of the water in which the specimen is7 I" V: a4 k% \1 C$ X! J! |/ x6 J
immersed need not be controlled unless specified in the product standard., c! W5 Q& m3 M. v
Unless specifically required by the product standard, a shielded or metal-covered single-conductor
8 @, W' ?* P/ x: b0 Xspecimen need not be immersed in water, the test voltage being applied between the conductor and the
9 [/ b5 v: [2 @. q: c: rshield or metal covering.( w. E2 C$ b; i( F8 F+ d
Unless specifically required by the product standard, a multiconductor cable need not be immersed in# c6 z% m) y) M. L# `5 k( `6 {3 F
water, the test voltage being applied between each conductor and the electrode, consisting of all other
; e3 p* j8 V, y9 S0 Gconductors connected together and to all shields and metal coverings, as applicable.
# `' d2 z1 o2 i0 _9 }3 HIn all cases, the ends of the conductor of the specimen shall be spaced from the grounded electrode a; L k7 m- |6 e4 v+ e; w- Q
sufficient distance to prevent corona or flashover at the ends during application of the test voltage./ ~" i! l5 }5 {7 n
6.2.3.2 Method 2 (in air): F" q+ h& Q3 p6 D
Both ends of the individual conductors shall be made bare.
- Q/ r- J1 |( H* u' j0 tFor a single-conductor cable, a grounding electrode, when not present as a component, shall be applied.
7 B7 U0 g4 K' U; X5 {8 ^& }! xA snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable.
, C* N4 A6 I- k6 ^% m0 j5 N; J6.2.3.3 Method 3 (in air at elevated temperature)
7 g+ W! z; p2 z0 M7 f( F8 N4 sBoth ends of the individual conductors shall be made bare.
# p' X( p( a+ K. ]# i' K' T. cFor a single-conductor cable, a grounding electrode, when not present as a component shall be applied.1 ?, Z! D4 |% T2 N4 W4 ]7 D
A snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable. |
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