PEXLINK - Line Surge Arresters

Both large and small public/private utility owners of transmission systems face a sharpened competitive situation which demands increased availability and reliability of the systems. At the same time consumers have become more demanding as their processes are dependent on constant and reliable energy supply of good quality. Hence, there is a strong demand for a reliable power grid both from the utility owners as well as the electricity consumer perspective.

Increased line availability for lightning events

By locating the PEXLINK on sections of lines with high footing impedance towers and on additional low footing-impedance towers at each end of the section, PEXLINK protects existing shielded and non-shielded lines from abnormal lightning surges (frequent or high amplitudes) and reduces the outages.
The reduced outages are beneficial also indirectly in that sensitive equipment are not damaged and the circuit breakers overhaul interval can be extended. Thus, total maintenance costs are also reduced.
This protection may be used for all system voltages where the stated abnormal conditions exist. Arresters with moderate energy capability are often enough. However, the high-current capability must be large and distribution-type arresters may not be suitable.

Increased line availability for switching events

For long EHV lines, station surge arresters are usually located at line-ends. By deploying PEXLINK at one or more points along the line e.g. at midpoint or 1/3 and 2/3 line length switching surge overvoltages and thus line insulation requirements could be limited without the use of pre-insertion resistors. The surge arresters used for this type of PEXLINK application should be designed for high energy capability. Usually an SL (PEXLIM R) or SM (PEXLIM Q) surge arrester will be enough out on the line but higher arrester classes may be necessary at the receiving end of the line

The NGLA by Hitachi Energy can be used on all voltage levels and increases the availability of electricity networks by providing efficient and reliable protection against disruptions caused by lightning strike and switching overvoltage events.

Hitachi Energy NGLA are built using well-proven and robust installation hardware, whilst keeping the installation time and effort to a minimum. The hardware is designed to allow for flexibility of installation

Hitachi Energy NGLA design offers a number of benefits:

• ·Full disconnection with integrated replacement indication – achieves full insulation withstand for the transmission line in case of a fault and provides a visual indication of the need to replace an overloaded NGLA
• Flexibility of installation – allows for installation on different tower and line configurations
• Quick and easy installation – outage time of critical transmission lines can be kept to a minimum as the installation process only requires standard tools and most of the build can be prepared in advance at ground level
• Robust installation hardware – from our experience with PEXLINK NGLA and through extensive testing far beyond the standard requirements, the longevity of the solution with minimal risk of interruption and outages is assured
• Easy asset replacement management – the universal design of the NGLA enables ease of managing spare stock and performing replacement of failed units
• Switching control – provides switching control functionality

The EGLA 765 kV increases the availability of Ultra-High Voltage (UHV) electricity networks by providing efficient and reliable protection against disruptions caused by lightning strike and switching overvoltage events.

Designed for applications at 765 kV, this line surge arrester provides efficient and reliable protection against overvoltages caused by both lightning strikes and switching overvoltages – a unique feature for an EGLA.

The EGLA for 765 kV is built on the vast experience of our PEXLINK concept using well-proven and robust installation hardware, whilst keeping the installation time and effort to a minimum.

Hitachi Energy EGLA design for 765 kV offers a number of unique benefits:

• Full disconnection with integrated replacement indication – achieves full insulation withstand for the transmission line in case of a fault and provides a visual indication of the need to replace an overloaded EGLA
• No need for specific type testing – independently use of the EGLA on various tower configurations without the need to re-perform type testing
• Short implementation time – implementation time can be minimized due to absence of specific type testing requirements
• Quick and easy installation – outage time of critical transmission lines can be kept to a minimum as the installation process only requires standard tools and most of the build can be prepared in advance at ground level
• Robust installation hardware – from our experience with PEXLINK NGLA and through extensive testing far beyond the standard requirements, the longevity of the solution with minimal risk of interruption and outages is assured
• Easy asset replacement management – the universal design of the EGLA enables ease of managing spare stock and performing replacement of failed units
• Switching control – provide switching control functionality in a similar way to NGLA, a unique feature for an EGLA

EXCOUNT-II is our remote wireless monitoring and diagnostics product with the most extensive and powerful features that enables users to keep track of overvoltages in the network as well as providing state-of-the art online condition monitoring of arresters.

The sensor enables advanced surge registration with date and time of surge events along the transmission line - enabling the user to assess the operation of the PEXLINK installation. In addition, the EXCOUNT-II can measure the essential resistive leakage current that gives a good indication of the arrester’s condition and fitness for continued service – an important feature for critical installations.

The measurements can be remotely read when convenient with the aid of a hand-held transceiver and an external antenna. Remote reading provides increased personnel safety compared with conventional counters.

The measured data can then be transferred to a computer for statistical analysis. Included with EXCOUNT-II is specially designed software which facilitates download of the measured data from the transceiver and permits quick analysis and report­ing of the collected information.

The sensor is housed in a sealed, weather-proof case, suitable for outdoor use and proven to match the short-circuit capability of the arrester to which it is connected. The sensor requires no external power supply or battery replacement.