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Galloping of overhead transmission lines (OHTLs) may induce conductor breakage and tower collapse, and there is no effective method for long distance distribution on-line galloping monitoring. To overcome the drawbacks of the conventional galloping monitoring systems, such as sensitivity to electromagnetic interference, the need for onsite power, and short lifetimes, a novel optical remote passive measuring system is proposed in the paper. Firstly, to solve the hysteresis and eccentric load problem in tension sensing, and to extent the dynamic response range, an ‘S’ type elastic element structure with flanges was proposed. Then, a tension experiment was carried out to demonstrate the dynamic response characteristics. Moreover, the designed tension sensor was stretched continuously for 30 min to observe its long time stability. Last but not the least, the sensor was mounted on a 70 m conductor model, and the conductor was oscillated at different frequencies to investigate the dynamic performance of the sensor. The experimental results demonstrate the sensor is suitable for the OHTL galloping detection. Compared with the conventional sensors for OHTL monitoring, the system has many advantages, such as easy installation, no flashover risk, distribution monitoring, better bandwidth, improved accuracy and higher reliability.

This paper presents a comprehensive evaluation method of cable partial discharge detection system based on fuzzy theory. First of all, evaluation index of the detection system is chose based on the system parameters and expert experience. Secondly, the weight coefficient of each evaluation index is calculated by using the method of subjective weight and objective weight combination, which not only considers the important role of expert experience in comprehensive evaluation, but also reflects the objective effect of equipment performance parameter in comprehensive evaluation. Finally, by improving the traditional ridge function, the function of the equipment performance quality grade is established, and the fuzzy characteristics between the index quality grades are accurately described. The method was used to evaluate five different PD detection system manufactured by different company, and the result indicate the proposed method can sort the PD detection system based on the evaluation result. The method quantifies the PD detection system evaluation, and it provides a comprehensive and objective evaluation opinion for the selecting of cable partial discharge detection equipment.

The partial discharge fault detection and location with the method of oscillating wave detection system has been widely applied on medium voltage cable. However, due to inaccurate data of power cable length, the propagation velocity of travelling wave along power cable just is an experience value resulting in the great error of fault location. Based on the dispersion characteristics of signal propagation in power cable, a measurement method for cable length was proposed. First, the low/high frequency velocity was determined according the physical properties of the insulation and semiconducting layer material. Then, the sine wave signal with known propagation velocity was injected into the test power cable and the propagation time was recorded by the GPS timing equipment. At last, the specific length of test power cable was determined based on the experiment results at two different frequencies. The experimental results show that length value error of power cable resulting in the system error is less than 10m.

As a traditional approach of partial discharge (PD) in power transformers, ultrasonic detection with piezoelectric transducers (PZT) has drawbacks of low sensitivity and low detection efficiency. In order to overcome these disadvantages, an ultrasonic detection system based on fiber Bragg grating (FBG) is developed for PD in power transformers. Take the advantage of good insulation ability and immunity to electromagnetic interference, the optical sensor can be put into the transformers and detect the weak PD signal directly. In this paper, ultrasonic detection theory of FBG was analyzed, and PD detection experiments in transformer oil were carried out to test the performance of this FBG ultrasonic detection system. Furthermore, in order to demonstrate the coherence and distributed measuring ability, PD detection experiments based on multi-point FBG string with different center wavelength were conducted. Study results show the performance of FBG ultrasonic detection system is better than traditional PZT sensor, and satisfactory detection coherence of FBG with different center wavelength is proved. Moreover, distributed ultrasonic measuring of PD in power transformers can be realized by multi-point FBG string with application of wavelength-division and time-division multiplexing technology.

Heavy ice coating of overhead transmission lines created the serious threat on the safe operation of power grid. The measurement of conductor icing had been an effective and reliable methods to prevent potential risks, such as conductor breakage, insulator flashover and tower collapse. Because of the advantages of immunity to electromagnetic interference and no demand for power supply in site, the optical load cell has been widely applied in monitoring the ice coating of overhead transmission lines. In this paper, we have adopted the shearing structure with additional grooves as elastic element of load cell to detect the eccentric load. Then, two welding package fiber Bragg gratings (FBGs) were mounted onto the grooves of elastic element with a direction deviation of 90° to eliminate temperature effects on strain measurement without extra FBG. After that, to avoid the occurrence of load cell breakage in heavy load measurement, the protection part has been proposed and added to the elastic element. The results of tension experiments indicate that the resolution of the load cell is 7.78 N in the conventional measuring range (0–10 kN). And in addition, the load cell proposed in this paper also has a good performance in actual experiment in which the load and temperature change simultaneously.

The online monitoring of ice load of transmission lines, which reflects the dynamic load of line, can alert the early stage ice in advance and guarantee the safety of power supply. However, the fiber sensors, which were used in ice online monitoring of overhead transmission lines, usually had low sensitivity and bad repeatability. And the capacity of sensor network was limited and it was difficult to provide hundreds of FBGs for optical sensing of overhead transmission lines in kilometers. In this paper, we proposed a novel load cell based on Fiber Bragg Grating (FBG) and presented the idea for high-capacity sensing network. Firstly, we adopted shearing structure with additional protection parts to reduce the influence of eccentric force. Then the FBG gauges were welded on the elastic element to avoid glue aging problem. After that, the FBGs were mounted at the front/rear slot with the direction deviation of 90° from the each other to eliminate the temperature effect in strain detection, and the extra FBG which usually used for temperature compensation is not necessary. The results of tension experiment indicate that the tension sensitivity and resolution of the load cell is 0.1285 pm/N and 7.78 N. Moreover, the expanded sensing network proposed can export consecutive modulating pulse as incoming signal for FBG sensors to detect the strain change result transmission line load.

Heavy ice coating of high-voltage overhead transmission lines may lead to conductor breakage and tower collapse causing the unexpected interrupt of power supply. The optical load cell applied in ice monitoring systems is immune to electromagnetic interference and has no need of a power supply on site. Therefore, it has become a hot research topic in China and other countries. In this paper, to solve the problem of eccentric load in measurement, we adopt the shearing structure with additional grooves to improve the strain distribution and acquire good repeatability. Then, the fiber Bragg grating (FBG) with a permanent weldable package are mounted onto the front/rear groove of the elastic element by spot welding, the direction deviation of FBGs is 90° from each other to achieve temperature compensation without an extra FBG. After that, protection parts are designed to guarantee high sensitivity for a light load condition and industrial safety under a heavy load up to 65 kN. The results of tension experiments indicate that the sensitivity and resolution of the load cell is 0.1285 pm/N and 7.782 N in the conventional measuring range (0-10 kN). Heavy load tension experiments prove that the protection structure works and the sensitivity and resolution are not changed after several high load (65 kN) cycles. In addition, the experiment shows that the resolution of the sensor is 87.79 N in the large load range, allowing the parameter to be used in heavy icing monitoring.