ENERGY INDUSTRY RTTR Cable Monitoring System

Cable monitoring systems continuously monitor the temperature of power cables to ensure their operational safety and efficiency. Areas where local temperature increases occur due to poor heat dissipation are referred to as hotspots. These hotspots limit the maximum current-carrying capacity of the cable system. If these are not detected and the cable's permissible load capacity is exceeded, it can lead to accelerated aging of the cable, thermal destruction of the cable insulation, and potentially result in a short circuit and cable failure. Cable monitoring allows for precise localization and assessment of hotspots, thereby increasing the safety and reliability of the cable system.

A cable monitoring system consists of a fiber optic cable installed along the power cable, a DTS (Distributed Temperature Sensing) device for measuring the temperature data reflected back from the fiber, a control cabinet with an industrial PC and communication interfaces for network control technology, server-side (database) software, and client-side visualization software.

DTS (Distributed Temperature Sensing) is a spatially distributed (continuous) temperature measurement technology that uses the fiber optic cable, installed along the power cable, as a temperature sensor. For flat-laid cables, the fiber is embedded in a stainless-steel tube inte-grated into the cable's shield section during manufacturing. In triangular cable arrangements, the fiber can alternatively be positioned in the cable’s interstice. The DTS temperature measurement is based on the Raman scattering of laser light. Local temperature changes induce lattice vibrations in the fiber's molecular structure, which causes Raman scattered light with anti-Stokes and Stokes components. The local temperature of the fiber is determined by the intensity ratio of the anti-Stokes to Stokes light. These light scatter-ings occur almost simultaneously along the entire length of the fiber. Using a fiber-optic radar measurement technique, a temperature profile is obtained for all locations along the fiber during each measurement cycle.

DTS technology allows for distributed temperature measurement along the entire length of the cable, a unique feature for large distances. Unlike traditional methods that only provide point-specific temperature measurements, DTS captures the temperature at every location along the fiber, enabling early detection of unexpected hotspots. Since the measurement is conducted using laser light, the signals are immune to electromagnetic interference. The fiber, serving as a passive sensor, is electrically insulated and does not affect the cable's internal temperature, resulting in a higher measurement accuracy.

The specifications of a DTS system can be tailored to the application. The system range can extend up to 70 km, with a spatial resolution between 50 cm and 2 m. The temperature accuracy is typically around 1K and depends on the chosen resolution, measurement time, system calibration, and the environmental conditions surrounding the fiber.

Yes, the fiber can also detect and evaluate acoustic signals along the measurement path. Distributed Acoustic Sensing (DAS) allows for the localization of mechanical impacts on the cable (e.g., damage caused by excavation work) and electrical impacts (e.g., the location of cable faults).

Yes, the fiber can also detect and evaluate strain along the cables. Brillouin scattering enables the localization of mechanical impacts in the longitudinal direction of the cable (e.g., during cable installation in ducts).

Our measurement and communication software supports standard protocols such as Modbus, IEC60870-5-104, and IEC 61850. Data can also be transmitted and received via digital, analog, and relay interfaces. Additional communication protocols and interfaces can be implemented upon request.

RTTR (Real Time Thermal Rating) is a software modeling method for determining the real-time conductor temperature, considering the measured shield temperature (DTS) and the current of the monitored power cable. Using application-specific cable and route models, the current and maximum load capacity of the power cables can be calculated in real-time. This allows the cable system's load reserve to be optimally utilized and the cables to be safely operated up to their performance limit.

Yes, cable monitoring systems monitor the temperature in the cable's shield or interstice, with the primary purpose of locating hotspots. RTTR cable monitoring systems also locate hotspots but with the added capability of dynamically assessing the cable's load capacity in real time. The cable system's intrinsic load reserves can be efficiently utilized, enhancing operational safety. For optimal use of the RTTR system, the load reserves are calculated in real-time from the measured conductor temperatures and forecasted for the future. This provides a valuable tool for the control center to optimize their grids while ensuring maximum safety.

Yes, an existing monitoring system can be upgraded to an RTTR system without requiring modifications to the cable installation.

In addition to the DTS temperature measurement data, the primary data needed for operating the RTTR system are the load data from the power grid. Cable and route models are created using cable data sheets and installation plans for RTTR modeling.

If a hotspot (increased temperature) is localized along the power cable, the system sends a notification or alarm. Temperature thresholds can be predefined to adequately inform the control center, enabling them to take appropriate actions, such as redirecting or reducing the load.

Cable monitoring can be applied to almost all types of underground power cables, provided that fiber optic cables are either integrated into the power cable or installed parallel to it.

Once the cable monitoring system is in operation or integrated into the control center as an RTTR system, it runs fully autonomously without requiring any operational intervention. To ensure the system functions properly throughout the power cable's operational lifespan, we offer service and maintenance contracts to apply security-relevant software and firmware updates and maintain the hardware to prevent failures. Additionally, we provide standby support for emergencies and can offer ongoing advice and support for your (RTTR) cable monitoring project and its software.

The investment in RTTR cable monitoring systems is relatively low compared to the costs of the cable installation. RTTR systems significantly enhance the cost-effectiveness and opera-tional safety of the cable system, making them a crucial part of the NOVA (Netz-Optimierung vor Netz-Verstärkung vor Netz-Ausbau – Translation: Grid Optimization before Grid Reinforcement before Grid Expansion) principle.

An (RTTR) cable monitoring system can typically be delivered, installed, and be operational within a few weeks. The overall timeline depends on the project complexity and specific requirements.