This paper presents a method for rapid detection of faults on voltage source converter multiterminal HVdc transmission networks using multipoint optical current sensing. The proposed method uses differential protection as a guiding principle, and is implemented using current measurements obtained from the optical current sensors distributed along the transmission line. Performance is assessed through detailed transient simulation using MATLAB/Simulink models, integrating inductive dc-line terminations, detailed dc circuit-breaker models, and a network of fiber-optic current sensors. Moreover, the feasibility and required performance of optical-based measurements is validated through laboratory testing. Simulation results demonstrate that the proposed protection algorithm can effectively, and within very short period of time, discriminate between faults on the protected line (internal faults), and those occurring on adjacent lines or busbars (external faults). Hardware tests prove that the scheme can be achieved with the existing, available sensing technology.

In this paper, a sensor that is capable of measuring both ac current and temperature using a single fiber Bragg grating (FBG) is described. The device consists of a magnetically biased magnetostrictive alloy bonded to an FBG. The magnetic field generated by the current in a specially designed coil produces internal strains in the magnetostrictive alloy which can be detected by the FBG. The temperature at the sensing point is determined through averaging of the sensor output signal. The measurement range of the sensor can be varied by altering the design of the sensor coil. A prototype sensor that is capable of measuring ac currents up to 1 A has been constructed while simultaneously measuring temperatures of up to 100 degC

This paper is aimed at analysing the levelised cost of energy (LCOE) of onshore wind turbine generators (WTGs) that are in operation beyond their design lifetime. In order to do so, the LCOE approach is introduced and input parameters are discussed for a UK deployment. In addition, a methodology is presented to support economic lifetime extension and investment decision making at the end of an asset's design lifetime. As part of a case study, a wind farm consisting of six 900 kW WTGs is subjected to different combinations of i) lifetime extension (5- 15 years), ii) input assumptions (pessimistic, central, optimistic), and iii) re-investment types (retrofits). Results indicate that in the central lifetime extension scenario, LCOE estimates of 22.40 £/MWh are achievable

This paper presents a new method for locating faults in multi-terminal direct current (MTDC) networks incorporating hybrid transmission media (HTMs), including segments of underground cables (UGCs) and overhead lines (OHLs). The proposed travelling wave (TW) type method uses continuous wavelet transform (CWT) applied to a series of line current measurements obtained from a network of distributed optical sensors. The technical feasibility of optically-based DC current measurement is evaluated through laboratory experiments using Fiber-Bragg Grating (FBG) sensors and other commercially available equipment. Simulation-based analysis has been used to assess the proposed technique under a variety of fault types and locations within an MTDC network. The proposed fault location scheme has been found to successfully identify the faulted segment of the transmission media as well as accurately estimating the fault position within the faulted segment. Systematic evaluation of the method is presented considering a wide range of fault resistances, mother wavelets, scaling factors and noisy inputs. Additionally, the principle of the proposed fault location scheme has been practically validated by applying a series of laboratory test sets.

In this paper, we analyze the performance of the fiber Bragg grating (FBG) interrogation system based on an arrayed waveguide grating (AWG) device. The spectrum of light reflected from the FBG sensor is analyzed using an AWG, which acts as a coarse spectrometer. Using measurement points from the AWG channels, the original spectrum of the sensing element is reconstructed by means of curve fitting. The measurement system is modeled in the LabView environment, which allows the modification of the FBG and AWG parameters and simulating the measurement process. This, in turn, allows the quantification of the measurement errors resulting from the nonlinearity of the particular FBG/AWG configuration, and allows the optimization of the system design for the particular measurement errors permitted. In addition to the simulations of the proposed measurement system, we provide details of the laboratory evaluation.