Cost-efficient and easy to use

Following the TR250 temperature relay—which has protected transformers worldwide from destruction due to overheating for decades—ZIEHL’s UR series is now being deployed in its first substations. In this instance, the UR840IP serves as an example of the versatility of this new product series. The UR840IP from Ziehl Industrie-elektronik is a modern, web-enabled universal relay featuring an Ethernet interface, making it ideally suited for implementing a comprehensive condition monitoring system within utility-operated transformer substations. This application example demonstrates how the system extends far beyond traditional temperature monitoring to become the digital heart of a future-proof transformer infrastructure.

System Architecture and Sensor Integration

The UR840IP features 8 analog measurement inputs and 4 digital inputs, making it an extremely versatile monitoring solution. In a modern transformer substation operated by an energy provider, for example, the system is deployed with the following sensor configuration:

The thermal status of the transformer is monitored by several Pt100 sensors: one sensor for winding temperature (hotspot), one sensor for oil temperature at the top of the transformer, and an additional sensor for core temperature monitoring. Furthermore, an ambient temperature sensor is installed outside the substation to document local operating conditions. In parallel, a humidity and pressure sensor is installed, as moisture ingress is one of the primary causes of premature insulation degradation and transformer failure. The 0–10 V or 4–20 mA inputs enable the integration of transducers for cooling system parameters—such as fan and pump performance—as well as the monitoring of pressure and flow rates in liquid-cooled systems. The four digital inputs are configured to monitor critical operating conditions: door contacts to detect unauthorized access, contacts indicating the status of the cooling system and fans, and signals from low-voltage switches. This creates a system that captures the entire transformer status in real time—not merely temperature values.