| (19) |
 |
|
(11) |
EP 0 508 647 A3 |
| (12) |
EUROPEAN PATENT APPLICATION |
| (88) |
Date of publication A3: |
|
03.03.1993 Bulletin 1993/09 |
| (43) |
Date of publication A2: |
|
14.10.1992 Bulletin 1992/42 |
| (22) |
Date of filing: 25.03.1992 |
|
|
| (84) |
Designated Contracting States: |
|
FR GB |
| (30) |
Priority: |
25.03.1991 JP 60498/91
|
| (71) |
Applicant: NGK INSULATORS, LTD. |
|
Nagoya-shi,
Aichi-ken 467 (JP) |
|
| (72) |
Inventor: |
|
- Nakayama, Tetsuya
Fuso-cho,
Niwa-gun,
Aichi-ken 480-01 (JP)
|
| (74) |
Representative: Stoner, Gerard Patrick et al |
|
MEWBURN ELLIS
York House
23 Kingsway
London WC2B 6HP
London WC2B 6HP (GB) |
|
| |
|
(57) An arrestor unit is disclosed for protecting a power transmission line against lightening
surges. The arrestor unit includes a discharge electrode that is electrically separated
from the power transmission line by a series air gap. A plurality of non-linear resistors
are provided between the discharge electrode and an electrical ground. A container
is provided to house the non-linear resistors. The container is arranged to discharge
residual electric charges that accumulate in the non-linear resistors. The discharge
constant of the container and non-linear resistors is set to a value less than the
time interval between voltage surges of a normal multiple surge lightning current.