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Zinc Oxide Elements manufacture at OBLUM:
 High performance ZnO Varistors the key components of Surge Arresters are manufactured in state-of-the-art manufacturing facility by taking acute care of composition, purity, particle size of input materials, and manufacturing process, broadly consisting of homogenous mixing, spray drying, powder pressing and sintering. Sintered blocks are given a glass coating and heat treated to achieve good stability.
ZnO element consists of ZnO grains separated by extremely thin inter granular & depletion layers of Metal Oxide additives resulting in higher non-linear characteristics. ZnO contributes for the dissipation of heat and other oxide additives contribute for the non-linearity.
The Zinc Oxide Discs are designed in accordance with IEC Standards and are available in 33mm dia for distribution class, 41mm dia for discharge class-1, 50mm dia for discharge class-II, 62mm dia for discharge class-III and 75mm dia of 23mm height for discharge class-IV in 3KV rating. The Zinc Oxide discs are used in Surge Arresters, Polymer Arresters, Transmission Line Arresters, Cable Termination, Motor and Generator Protection, Tertiary winding protection etc. The zinc oxide discs are known as Varistors, Surge Suppressors, Voltage Limiters, Surge Protectors, Non-linear Resistors and Voltage dependent resistors.
Automated testing of Zinc Oxide Discs consists of subjecting each and every element for high energy withstand test in auto test system for selection and rejection of the failed discs without any manual interference and thereafter followed by classification tests.
Automated classification of zinc oxide discs consists of testing for leakage current, reference voltage and residual discharge voltage and printing the characteristic data on the disc. The discs are packed and dispatched to the assemblers of Arresters or used in OBLUM Porcelain and Polymer housed Arresters.
Durability : METOVAR Metal Oxide discs consistently withstand the following minimum design tests.
Two High current 4x10 mSec. 100KA surges.
Eighteen long duration current surges as per IEC 60099-4 of 2004 for various discharge classes.
Duty cycle test consisting of 20 discharges of 10KA, by two high current impulses and two long duration current impulses followed by rated voltage for 10 sec. and continuous operating voltage for 30 min. as per IEC 60099-4 of 2004. |
| Zinc Oxide Blocks Characteristics: |
| Characteristics |
dia 37+1mm
ht.23+2mm
(Dist.Class) |
dia 44+1mm
ht.23+2mm
(Class-1) |
dia 50+2mm
ht.23+1mm
(Class-2) |
dia 62+1mm
ht.23+2mm
(Class-3) |
dia 75+2mm
ht.23+2mm
(Class-4) |
| Rated Voltage(Ur) |
3KV RMS |
3KV RMS |
3KV RMS |
3KV RMS |
3KV RMS |
| Nominal Discharge Current(In) |
5KA Peak |
10KA Peak |
10KA Peak |
10KA Peak |
10KA Peak |
| Current used for the Long
Duration Impulse Test |
75A
1000 msec. |
250A
2000 msec. |
500A
2000 msec. |
600A
2400 msec. |
1000A
2400 msec. |
| High Current Impulse(Imax) |
65KA
4/10msec. |
100KA
4/10msec. |
100KA
4/10msec. |
100KA
4/10msec. |
100KA
4/10msec. |
| Maximum Continuous
Operating Voltage (Uc) |
2.55KV RMS |
2.55KV RMS |
2.55KV RMS |
2.55KV RMS |
2.55KV RMS |
| Reference Current(Iref) |
1.0mA |
1.0mA |
2.0mA |
3.0mA |
3 to 5mA |
| Maximum Residual Voltage at Nominal Discharge Current (Ures) |
9KVP |
9KVP |
8.5KVP |
8.0KVP |
6.8KVP to 7.2KVP |
| Reference Voltage(uref) |
>3KV RMS |
>3KV RMS |
>3KV RMS |
>3KV RMS |
>3KV RMS |
| Maximum Leakage Current under maximum continuous operating voltage (IL) |
150 m Amps |
250 m Amps |
300 m Amps |
300 m Amps |
400 m Amps |
| Applicable Standard |
SC 37B |
SC 37B |
SC 37B |
SC 37B |
SC 37B |
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