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CORONA RESISTANT PTFE INSULATED
MINIATURE HIGH VOLTAGE 
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  WIRES PER U.S.A. MIL-W-16878
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PERFORMANCE & QUALITY ASSURANCE

The curves of performance in Figure below show accumulated experience of 30 years.  At about 5 KV AC working, the Break Down Voltage (BDV) is 30 KV AC, and 80 KV AC at 20 KV AC working.  The Progressive Stress Test (PST, described here) simulates more closely the influence of corona on cable life.  It is a type of accelerated life-test under corona attack.  The observed co-relation between life of a cable under long-time tests at actual working voltages and under PST provides safe, repeatable prediction of cable life based on PST data.

Progressive Stress Test Graph

HVCR cables generally have problems with `Strip-Force' (adhesion of conductor to insulation) especially for higher insulation thickness; either the conductor is free-moving inside the insulation, or the it is difficult to remove from the conductor.  Our R&D has solved this important technical problem.  Now smaller conductor size with larger X CR rating is available with good adhesion of conductor and good strip force.

The test procedure and specs for HVCR cables are briefly described here.  There are no generally accepted specifications for HVCR wires & cables.  The test methods described here are based on long experience and specifications are proprietary.

On 100% length, 15 minute water soak, and water tank tests:

(a) Dielectric Test at Working Voltage (WV) + 10% + 1 KV; duration 5 minutes (e.g. for WV 10 KV AC/22.5 KV DC, test will be at 12 KV AC).

(b) Spark Test at AC using the value of KV DC rating for One Second, (e.g., for above type, 22.5 KV AC for one second).

(c) Conductor dia and Resistance, and visual/OD check of finished cable.

On samplesProgressive Stress Test (PST) on 0.6 metre samples from both ends of each piece (and identified):
(d) On these samples, AC voltage is applied in water tank test, starting at 1 KV and step-increasing by 2 KV at the end of each minute until break-down.  Time and voltage are noted, and the range/spread recorded.  BD Time should be above the minimum specified in the Figure for each piece.  Average of all values should be well above the minimum specified.

(e) For internal information and control, BDV on samples on AC is obtained and recorded.

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