Description
Main technical data for 10kA ZnO varistor inner core
|
Figure No. |
ZnO varistor inner core |
Rated Voltage |
MCOV(kV) |
Impulse current residual voltage |
2ms Rectangular current impulse withstand |
4/10us High current impulse withstand |
||
|
1/4us Lightning impulse current（kV） |
8/20 us Lightning impulse current（kV） |
30/60us Lightning impulse current（kV） |
||||||
|
1 |
Φ44x90 |
3 |
2.55 |
11.3 |
9 |
8.9 |
250 |
100 |
|
2 |
Φ44x120 |
6 |
5.1 |
22.6 |
18 |
16.8 |
250 |
100 |
|
3 |
Φ44x120 |
9 |
7.65 |
33.7 |
27 |
23.8 |
250 |
100 |
|
5 |
Φ44x150 |
10 |
8.4 |
36 |
30 |
23 |
250 |
100 |
|
6 |
Φ44x150 |
11 |
9.4 |
40 |
33 |
27 |
250 |
100 |
|
7 |
Φ44x150 |
12 |
10.2 |
42.2 |
36 |
30 |
250 |
100 |
|
8 |
Φ44x180 |
15 |
12.7 |
51 |
45 |
38.5 |
250 |
100 |
|
9 |
Φ44x210 |
18 |
15.3 |
61.5 |
54 |
46.2 |
250 |
100 |
|
10 |
Φ44x240 |
21 |
17 |
71.8 |
63 |
54.2 |
250 |
100 |
|
11 |
Φ44x270 |
24 |
19.5 |
82 |
72 |
62 |
250 |
100 |
|
12 |
Φ44x300 |
27 |
22 |
92 |
81 |
69.8 |
250 |
100 |
|
13 |
Φ44x330 |
30 |
24.4 |
102 |
90 |
79 |
250 |
100 |
|
14 |
Φ44x330 |
33 |
27.5 |
112 |
99 |
86.7 |
250 |
100 |
|
15 |
Φ44x360 |
36 |
29 |
123 |
108 |
92.4 |
250 |
100 |
Note: We can design and make products according to customer's specific requirements.
Over voltages in power system may occur due to lightning or switching operation. These overvoltages could reach dangerous amplitudes for power system apparatus. To protect the system electrical equipment and to guarantee an economic and reliable operation, surge arresters are applied in almost all types of electrical power network. Gapless zinc oxide (ZnO) surge arresters are widely used. The surge arresters are usually connected between the phase and ground terminals. They limit the voltage level in equipments such as transformers below the withstand voltage level.
The time axis is divided into the range of lightning overvoltage in microsecond, switching overvoltage in millisecond and temporary overvoltage in second. In the lightning overvoltage and switching overvoltage range, the magnitude of overvoltage can reach several per unit if the system is without arrester protection. Arrester could limit overvoltage below withstand voltage of equipment. This phenomenon clearly shows the importance of arresters for lightning overvoltage protection.
Construction of Zinc Oxide Surge / Lightening Arrester:
The construction of ZnO Lightening Arresters is very simple. They consist of an insulating housing which is made of porcelain and the inner column is made of the ZnO blocks as shown in Figure below.
ZnO block provide the Voltage- Current non-linear characteristics which serves the main purpose for the protection from overvoltage. Thus we can say that ZnO block has non-liner resistivity.
Voltage Current Characteristics of Zno Block:
Figure below shows the V-I characteristics of ZnO element which are divided into three regions, being low current region (A), operating region (B) and high current region (C).
