Taichung City, West coast of Taiwan, is the centre of activities for one of Taiwan’s three main science parks: the Central Taiwan Science Park. This area has already attracted approximately 92 foreign and local manufacturers pledging a total of 51 billion USD in investment.
This science park has played a key role in leading the development and advancement of high-tech industries of central Taiwan with the objectives of pushing high-tech industries to new heights and constructing sustainable operations by creating efficient and intuitive systems for operations in order to increase the stability of the supply of electricity.
The brand-new substation built in HouLi by the national utility, Taiwan Power Company (TPC) is a perfect example. With the objective of meeting the rising demand for energy as well as the requirements for smart grid, Mr. Lai-Jinn Chen (Deputy Director of Taichung Power Supply Branch at TPC) and his team needed a complete underground transmission power cable system (cable and accessories) that could be entirely monitored in real time.
Brugg Cables, one of the leading companies in the cable and accessories manufacturing business, equipped the new HouLi substation with their 345kV underground cable system. Brugg Cables also included LIOS EN.SURE Distributed Temperature Sensing (DTS) monitoring system with an integrated Real Time Thermal Rating (RTTR) solution.
Installation by Brugg Cables
The figure below provides a good overview of the laying conditions of the underground transmission line at the jobsite. Brugg Cables technicians installed the complete cable system i.e. the outdoor, the GIS and transformer terminations as well as the XLPE insulated power cable. As you can see in the figure below, the XLPE cable system connects the outdoor terminations to the GIS terminations; and from the GIS to the transformer terminations.
How to obtain the conductor temperature in different environments (tunnels, GIS, basements and outdoor areas)?
The conductor temperature forecasts are very difficult and imprecise due to permanent changes in the surrounding area and variations of load of the extra-high voltage (EHV) underground cable.
LIOS Technology´s DTS system with an integrated RTTR solution to measure the temperature along the entire cable length using optical fibres.
The distributed temperature profile (temperature at the fibre optic cable location) is used to determine the real time conductor temperature by the mean of complex extrapolation using several standards such as IEC, IEEE for the design of insulated underground cable systems. In addition to the temperature in the fibre optic cable, other parameters such as load in the EHV cable and thermal resistivity of the soil/environment are also considered during the process. Mathematical models are specifically prepared for each project to meet the Utility requirements.
Hot Spots Sensitivity
The OFDR principle ensures high temperature and spatial resolution measurements over long distances in order to meet the requirements of the electrical assets operator.With this very high resolution, LIOS DTS system is able to detect hot spots i.e. high temperature points at: the cable joints and terminations, proximities with other cable systems, steam lines and others.
The OFDR technology is different from the Optical Time Domain Reflectometry using a laser pulse principle (similar to radars) sensitive to dispersion effects and affected by a broadened spatial resolution at long measurement distances. In that case, the hotspot sensitivity measurements degrade with a function of distance.
Real Time Thermal Rating
Because the fibre optic cable is attached to the jacket of the EHV cable at the HouLi substation, the temperature is measured at the fibre optic cable location i.e. the jacket and not at the conductor. However, the DTS system along with the RTTR calculation engine, has the capably to calculate the conductor temperature in real time. Another plus with RTTR is “Emergency Operations” calculation. You can determine transients like current, time (duration) and temperature.
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