Leutron protects the Alzwerke’s new telecontrol system against lightning and overvoltage
The Alzwerke, energy supplier to Wacker Chemie since 1922, reorganized the lightning protection of their telecontrol system in autumn 2005: Instead of the conventional lightning protection zone concept, the central entry point principle is used. It was realized with protective devices from Leutron GmbH.
The Alzwerke Burghausen are located in the southeast of Bavaria, right on the border with Austria. The hydropower plant, a wholly owned subsidiary of Wacker Chemie AG, has been supplying the adjacent production facilities of the plant with energy since 1922 and today covers 25-30% of the annual requirement. At the beginning of the 1970s, those responsible decided to install a telecontrol system for better monitoring and control of the power supply, with the help of which the Alz Canal and weir system could be monitored more easily and, above all, permanently. Since then, groundwater levels, water levels and temperatures have been continuously and automatically recorded and transmitted to the control room at the Burghausen plant and the weir center.
However, the technicians in the plant soon discovered that a location in the middle of three watercourses, namely between Salzach, Alz and Inn, is quite risky: Again and again, damage caused by overvoltage or even direct impact knocked out the valuable measuring and transmission devices. Helmut Zitzmann, communications engineer and sales engineer at the lightning protection specialist Leutron GmbH, explains the problem: “The measuring devices of the telecontrol system are close to, mostly in the water, and are therefore at great risk because they have a direct connection to earth. Protection is just as intensive here as, for example, a weather station on a summit. To make matters worse, barrages and weirs are metal structures that are particularly at risk of lightning. ”
At night and on weekends: personnel moved out during thunderstorms
Not only did the measuring devices fail frequently, but also the substations of the telecontrol system. These line the 16-kilometer Alz Canal at intervals of 1,000 meters and are responsible for forwarding information from the measuring devices to the headquarters. Even without visible physical damage to sensors or transmission technology, the engineer on duty could never rely 100 percent on the data arriving during a thunderstorm, because there was always the possibility that it was distorted by overvoltages. “Before the first lightning protection system was installed, the devices often broke in the lightning season,” reports Hans Wagner, operations engineer at Alzwerke GmbH. He was not yet there at the time, but he remembers the stories of his predecessor well. “The problem was not the failure of the assemblies,” he says, “but that the staff had to move out at weekends or at night to replace components and repair the system.” In the early 1980s, the telecontrol system was finally equipped with lightning and surge protection elements upgraded.
New telecontrol system, new lightning protection concept
A quarter of a century later, however, the monitoring equipment, which had been so modern in the past, had finally become obsolete, Ethernet and radar technology replaced the original relay technology, and lightning and surge protection were also to be replaced. However, the Alzwerke did not want to use the conventional lightning protection zone concept. Instead, they had measuring devices and substations secured according to the Central Entry Point Principle (ZEP). “With the ZEP principle, measuring devices and evaluation stations can be protected more precisely than with the traditional lightning protection zone concept”, Hans Wagner explains the decision. “Because of this and because Leutron’s coarse, medium and fine protection can be combined in a single device to make it very compact, we can manage with fewer protective devices. In contrast to the past, the new lightning protection system is much easier to install and clearer. ”
There is a simple idea behind the ZEP principle: a central point is defined for each control cabinet, at which all network and data lines are inserted and exported. The surge protection is also located here: The PowerPro BCD developed by Leutron is used for the power cables. It combines lightning current and surge arresters of the types T1-T3 in one device. The data lines are protected by special combination arresters.
Operations engineer Hans Wagner cannot estimate the expected payback time, because: “We don’t know beforehand how many thunderstorms there will be.” However, he also makes it clear: “Terms such as return on investment and payback depict economic considerations. We are concerned with security, however, and it cannot be calculated. ”
