When using transformers, electrical coils, and other devices operated with oil (e.g., for insulation), for a volume of 1 m3 or more of water-polluting liquids, the energy supplier must comply with special requirements for operating such systems.
To prevent water-polluting liquids escaping from the overall system in the event of any incidents, all oil-filled devices must be set up on liquid-tight surfaces. These surfaces must be designed either as a catch basin or a drainage surface to an external collecting chamber or large-scale separator.
The Arbeitsgemeinschaft Industriebau (AGI), a German trade organization of industrial construction companies, has authored a technical standard that describes various structural options for designing transformer catch basins so as to comply with the German Ordinance on Installations for Handling Substances Hazardous to Water (VAwS). The technical standard also notes that the precipitation water can be pumped out of the basin or the collection chamber after a visual inspection. This is important because in the event of a catastrophic failure all of the oil from the transformer can be collected and does not pollute the environment.
Phoenix Contact offers a new system for continuous level monitoring, alarm generation, and pumping precipitation water for transformer catch basins. The water level measured by an ultrasonic sensor is continuously compared to two different limit values.
A FO cable is used for communication from the control cabinet to the higher-level station control engineering using IEC 61850 so as to eliminate EMI influences in the transformer station. Thanks to this information, appropriate action can then be taken from the network control center.
During the subsequent inspection tour of the station by the maintenance personnel, the pumping process is started after a visual inspection of the precipitation water for oil contamination. The pumping process then proceeds automatically. During this process, the water level is still continuously measured and lowered to an adjustable minimum volume. An additional rod probe ensures that the pumping process is stopped immediately if any oil contamination is detected. The key components of the system are certified and have received official technical approval.
Functions of the monitoring system
The solution covers the following functions:
Configuration and diagnostics via web page
The monitoring unit is parameterized via the web server that is integrated in the small-scale controllers. A web interface is available for conveniently configuring the solution as well as displaying the diagnostic information. All that is needed to visualize the interface is a standard web browser (such as Microsoft Internet Explorer or similar) and JAVA Virtual Machine.
IEC 61850 – data modeling
The data model that is already integrated allows the monitoring system to be started up quickly using the control engineering by simply importing the .scd file into the control engineering. According to IEC 61850, the controller represents an Intelligent Electronic Device (IED). The IED contains an access point with a Logical Device (LD). Two standardized Logical Nodes (LNs) and three generic nodes (GGIOs) are defined in the LD.
There is no GOOSE (Generic Object Oriented Substation Events) communication in the monitoring system data model. Individual modification or extension of the data model can therefore be carried out easily. The time is synchronized via an SNTP server in the network. The corresponding address can be entered via the web interface.