The smart grid of the power system includes power plants, high-voltage grids, substations, distribution stations, etc., specifically including generators, transformers, power cables, switches and other power equipment. Power equipment usually operates in environments such as high voltage, strong electric fields, and heat loads, and the working environment is unmanned and unmonitored. As an engineering infrastructure, the smart grid involves the electricity needs of thousands of households, and the operating temperature of power equipment is an important factor in ensuring the safe operation of the smart grid. Whether it is transformers, power cables, or other power equipment, as important components of the power system, they may cause local overheating or arc sparks due to some circuit problems or external factors, leading to fires and causing losses to people’s production and life. Therefore, in order to avoid such a malignant event, it is urgent to conduct comprehensive temperature monitoring of power equipment. The environmental temperature and cable operation status of cable tunnels used to accommodate a large number of cables laid on cable supports in corridors or tunnel structures can only be detected when faults occur. The longer the operation time, the more prone it is to overheating and burning accidents, which may cause huge economic losses.
With the increasing deployment of power and communication in tunnels, fiber optic cables are mostly laid underground. During the long-term use of fiber optic cables, temperature monitoring is required to prevent serious safety accidents such as fires due to high temperatures. Through long-term monitoring and analysis of temperature, many information about fiber optic temperature can be obtained. Therefore, whether temperature can be monitored for a long time, continuously, and accurately largely determines the accuracy and timeliness of temperature warning and alarm.
If point temperature measurement is used, it is prone to electromagnetic interference and is not suitable for strong electromagnetic scenarios, while fiber optic temperature sensors are not affected by electromagnetic interference and are very suitable for temperature monitoring in power systems. Fiber optic temperature sensors include single point temperature sensors and quasi distributed fiber optic temperature sensors. A single point temperature sensor measures a certain point in the temperature field with high measurement accuracy and reliability, but it is difficult to measure the distribution of multiple points in the temperature field. To solve the measurement problem of multi-point distribution of temperature field, a quasi distributed fiber optic temperature sensor composed of a multiplexed fiber optic temperature sensor and an array of fiber optic temperature sensors has emerged. The quasi distributed fiber optic temperature sensor uses a single point fiber optic sensor array to form a spatial network distribution to achieve distributed fiber optic temperature measurement. The measurement accuracy and speed may be affected due to resolution, bandwidth, or spatial structure, making it difficult to accurately measure and locate temperature.
Distributed fiber optic temperature sensing for tunnel cables
The purpose and principles of designing a distributed fiber optic fire alarm system
(1) Purpose: In order to detect and report fires early, prevent and reduce fire hazards, ensure normal production and life, protect personal and property safety, important large buildings and high-rise building clusters must consider designing and installing automatic fire alarm systems.
(2) Principles: Safe and reliable, easy to use, advanced technology, and economically reasonable.
The characteristics of tunnel cables
Industrial cable tunnels are composed of a large number of cables laid together, suitable for long-distance transmission of electrical energy. Cable is an important power transmission equipment, and the production of modern industrial enterprises cannot be separated from electricity, and the transmission of electricity is completed by a large number of cables. It is a bridge to ensure the normal operation of industrial enterprises; It is the reserve force for the survival of industrial enterprises; It is an important component of the lifeline of industrial enterprises.
Prediction of tunnel cable fire faults
According to the analysis of power accidents, cable overheating faults can cause fires, leading to extensive cable burning and forced shutdown, making it impossible to resume normal production and life in a short period of time, causing significant economic losses and social impact. Through the analysis of accidents, it is found that overheating of cable joints is the direct cause of cable fires, and overheating of cable joints is caused by loose compression joints, oxidation of joints, etc., which leads to excessive contact resistance. Long term high-temperature operation causes insulation to decrease and breakdown, ultimately leading to the occurrence of cable fires. Based on the analysis of the characteristics of cable overheating faults, an effective method to prevent cable overheating and fire is to timely monitor the temperature of cable joints, analyze the aging degree of cable joints based on the trend of joint temperature changes, and issue an alarm before the actual failure of cable joints occurs.