Water no matter what the weather

The ground waterworks Haseldorfer Marsch in Wedel near Hamburg began operating in 1960 and extracts its raw water from three horizontal filter wells, two flat and eight deep wells, which are located at depths between 17 and 107 meters. Two thirds of the ground water obtained is treated in a flocculation system and the rest in a spray tower. Following subsequent filtration drinking water is delivered via four pure water pumps that guarantee a continual daily supply of 15 000 m³. Ensuring that this process runs smoothly requires reliable protection and monitoring measures.

Completely new safety aspects 

"Our plant was originally built without any form of lightning or surge protection", reports Hauke Beier a member of the waterworks maintenance team. "However, we discovered that uncontrolled incidents occurred repeatedly when thunderstorms arose; incidents such as invalid error messages, electronics failing or electrical equipment being destroyed. For that reason we decided to install surge protection in all of our electrical lines."

Due to the extensive surface areas of large processing plants they are easily susceptible to lightning strikes, which, for example, can then lead to the coupling of overvoltages. As a result the operators required a seamless lightning and surge protection concept that offers protection against both possible scenarios – direct and indirect lightning strikes. "In the past protection meant mostly external lightning protection; and if internal lightning protection was taken into consideration then simply in the form of power protection" explains Ralf Güthoff, product manager at the Electronics business unit at Weidmüller. "However, since 2006 a new supportive application standard has come into force that specifies guidelines for both selecting the right lightning protection zone concept as well as the risk analysis." As the waterworks is a public plant charged with guaranteeing a continual supply of water to countless numbers of people it is required in accordance with IEC 62305-1 – 4 that an external lightning protection must be integrated and, in addition, all ingoing and outgoing cables must be fitted with an internal lightning protection. In addition, the product standard IEC 61643-21 defines protection for measurement and control signals since 2009. That means that today a completely new safety aspect must be taken into consideration.

Overvoltage protection and remote signalling

"When building our new well system we wished to integrate significantly more monitoring functions, because the system is located several kilometres from the control room", relates Hauke Beier. "It was important for us that the central control room is kept up to date with regard to the status of the system." As an electromagnetic interference coupling is highly probable due to the long distance involved it was considered necessary to safeguard the connection to the control room with a reliable surge protection.

A spur line runs from the pump house of the new well system to the well shaft. The controls that regulate the valves, carry out water level measurements and are responsible for technically protecting the plant against outside hazards are located in this shaft. A Weidmüller primary, single-phase switch-mode power supply unit of the type ConnectPower provides power to the controls as well as to the other electrical equipment in the well shaft.

To ensure it is possible to continuously monitor the processes in the well shaft in all weather conditions it was decided to install surge protection including remote signalling functionality in all installed power and signal lines. To protect their power lines the Haseldorfer Marsch waterworks utilises lightning and surge protection components of the types PU I – III that offer compelling product characteristics such as high discharge currents and a compact design. With regard to signal protection Weidmüller’s new product series VARITECTOR SPC (VSPC) offers optimum attributes.

Permanent monitoring and simple testing

The pluggable surge protection module for measurement and control signals provides the defined protection classes D1, C2 and C1 as specified in IEC 61643-22 and contains an internal monitoring function that regulates error detection and error message processes. If a short-circuit occurs on the signal line or a connection is wired incorrectly the arrester enters an overload failure mode as required in the latest version of IEC 61643-21. At the same time a message is transmitted automatically via the VSPC Control Unit to the control room, whereupon a red LED lights up on the device and on the defective VSPC Control Unit instead of a green LED. That ensures that not only is the operator kept up to date through permanent monitoring of the status of his protection concept, but that the on-site technician is also informed by means of error indication. As a result the defective module can be very quickly found and replaced.

The test unit V-TEST Basic makes it possible to adhere to maintenance intervals as specified in accordance with IEC 62305-3. Bearing in mind that no adapter is required, the arresters are simply plugged into the compact and portable test unit. All that is required to analyse the status of the arrester is a couple of simple actions to ensure early prevention of failure caused by the effects of lightning and surge events.

Safety concept for power, signals and data

Suitable lightning and surge protection arresters need to be selected to prevent faults and damage occurring from lightning strikes. Weidmüller’s PU series for power and the new BSPC series for signals guarantee protection as specified in the relevant standards. Industrial Ethernet is utilised to visualise all processes in the waterworks. AdvancedLine unmanaged switches from Weidmüller act as the central network components to prevent data collisions, enable fast packet switching and increase data throughput. With these solutions the Haseldorfer Marsch waterworks has received a safety concept that offers a high-level of supply security for the transmission of power, signals and data.