Line surge arresters (NGLA/EGLA)
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Line surge arresters (NGLA/EGLA)
The use of surge arresters on hazardous stretches of a power line helps improve network protection and increases the reliability of the entire transmission system. Offering a highly efficient combination of low weight, outstanding strength, and safety features, Siemens 3EL surge arresters are ideally suited for this purpose.
Siemens provides two solutions for line surge arresters:
Non-gapped line arresters (NGLA):
NGLA line surge arresters can either be installed directly on the insulators or on the tower, depending on the tower design and the arrangement of insulators and lines. Siemens 3EL surge arresters are available as NGLA types
Externally gapped line arresters (EGLA):
EGLA line surge arresters have an external spark gap placed in series that galvanically isolates the active part of the line surge arrester from the line voltage under normal conditions. The series varistor units (SVU) of the EGLA 3EV product lines are based on the respective 3EL product lines.
Non-gapped line arresters (NGLA)
Non-gapped line surge arresters (NGLA) offer a high degree of mounting flexibility and operational reliability. Depending on the tower design and the arrangement of insulators and lines, these arresters can either be installed directly on the insulators or on the tower.
Thanks to their high energy absorption capacity, non-gapped line arresters offer a very high level of protection against overvoltages caused by lightning and network-generated switching impulse current overvoltages.
To galvanically isolate the line surge arrester from the line voltage in the unlikely event of a fault or thermal overload, a disconnector is installed in series. It automatically and immediately disconnects the line surge arrester from the line voltage. This allows the affected overhead line to continue to be used until replacement can be scheduled.
In addition to the line surge arresters, the new ACM advanced monitoring system can be installed to provide arrester condition monitoring. This system monitors wirelessly and provides detailed information about leakage currents and converted energy.
|Highest system voltage kV||||||145||362||550||800|
|Maximum rated voltage kV||||||144||288||468||588|
|Nominal discharge current kA||Thermal energy rating kJ/kVr||Charge transfer rating C|||||||||
|Rated short-circuit current kA||||||20||65||65||65|
|High current impulse kA||||||100||100||100||100|
|Specified short-term load SSL kNm||||||0.5||1.2||4.0||10.0|
Externally gapped line arresters (EGLA)
EGLA line surge arresters have an external spark gap placed in series that galvanically isolates the active part of the arrester from the line voltage in normal conditions. In case of lightning, the spark gap is ignited and the overvoltage is safely discharged to the ground.
EGLA line surge arresters prevent all insulator flashovers caused by lightning strikes. Hence EGLA increases network stability as well as the availability of the overhead line.
An additional benefit of EGLA line surge arresters is that there is no leakage current, because the series gap disconnects the MOV blocks in the active part of the EGLA,from the system voltage in normal operating conditions.
The compact design of the EGLA allows installation and lightning protection even on existing towers with very small clearances.
Siemens EGLA line surge arresters are available for system voltages of up to 550 kV.
All Siemens EGLAs are designed and tested to comply with the latest IEC 60099-8 standard, which became effective in January 2011.
Line condition studies:
Siemens optionally offers software analysis (simulation) based on Cigré studies to examine and conduct preliminary tests of customer-specific applications as a way of determining the optimal, cost-effective solution. With this approach, the customer only needs to equip particular phases or individual line segments with line surge arresters, and can still ensure sufficient lightning protection of the overhead line and reduce network failures.
In the first phase of an analysis, all important parameters of the transmission line under study are entered into the simulation software, and the installations to be examined are selected. This approach takes the following factors into consideration:
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