With the progress and development of power technology, the application of high-voltage and ultra-high voltage power cables in power systems is becoming increasingly widespread. How to increase the current carrying capacity of cables without changing the existing engineering conditions, thereby increasing the power transmission capacity, has become an urgent problem that power engineering personnel need to solve. In recent years, online monitoring systems mainly focused on monitoring the operating temperature of high-voltage and ultra-high voltage power cables have continuously developed, and have further developed into online continuous monitoring of the remaining load capacity of power cables. This provides information on the available load capacity of cables for power system dispatchers, helps them allocate cable operating loads more reasonably, and improves the operational capacity of cable lines. Alternatively, in the event of an emergency situation in a specific part of the system, the system can be quickly reassembled based on its topology and the actual available load capacity of the cables. The remaining cables with high load capacity can be used to provide load support for the faulty line in a short period of time, so that the system can enter emergency operation as soon as possible and ensure uninterrupted power supply.
Fiber optic temperature measurement and current carrying capacity analysis system
A distributed fiber optic cable temperature monitoring and real-time current carrying capacity analysis system was installed on two 110 kV cables. The project started construction at the end of October and completed the laying of temperature measuring optical cables and the installation and commissioning of temperature measuring hosts by December. The development and commissioning of interface software with the comprehensive automation system, installation and commissioning of current carrying capacity analysis software, and experimental and verification of current carrying capacity software calculation results were also completed.
The temperature measurement host of this system adopts an external laying method for installing temperature sensing optical cables, which means laying one temperature sensing optical cable along each phase of the cable line for measuring environmental temperature. The temperature sensing optical cable is 62 5/125 μ m multimode optical fiber, the outer sheath of the optical cable is made of high-performance low smoke halogen-free flame retardant thermoplastic material. Temperature sensing optical cables have excellent thermal conductivity, mechanical properties, waterproof performance, and corrosion resistance. The temperature sensing optical cable is constructed while the cable is in operation. The optical cable inside the conduit is not tied, while the optical cable outside the conduit is fixed by tying. The binding and fixing method for temperature sensing optical cables is detachable, with a fixed spacing of 0 5 m; The temperature sensing optical cable is installed on the side of the cable to ensure close contact between the temperature sensing optical cable and the outer sheath of the cable. The temperature sensing optical cable is fixed at the middle joint of the cable using a double ring winding method to ensure close contact between the temperature sensing optical cable and the middle joint of the cable. The unfolded length of the double ring winding optical cable is 5-10 meters. Hang labels on the temperature sensing optical cables at the cable terminals and each work well, indicating the starting and ending points of the temperature sensing optical cables, the name of the substation, and the length of the temperature sensing optical cables from the starting point.
Laying temperature measuring fiber optic cables along the 110 kV cable line and building an optical fiber temperature measurement system can conduct surface temperature testing and calculation of cables at safe operating temperatures (cable conductor temperature of 90 ℃). By accumulating and analyzing recorded data, the bottleneck of cable line operation can be determined; By analyzing and calculating the conductor temperature of the cable, the real-time rated current carrying capacity of the cable under operating conditions, and the relationship between the surface temperature of the cable, the conductor temperature of the cable, and the maximum current carrying capacity of the cable through mathematical models, the allowable current carrying capacity of the cable design can be effectively utilized to achieve economic operation goals