Voltage and Current Measuring Technologies for High Voltage Direct Current Supergrids: A Technology Review Identifying the Options for Protection, Fault Location and Automation Applications

Abstract

After the occurrence of a DC-side feeder faults on HVDC transmission systems, protection and fault detection systems are anticipated to minimize their onerous effects, by initiating fault-clearing actions such as selective tripping of circuit breakers. Following the successful fault clearance, a subsequent action of significant importance, is the meticulous estimation of its location as a means to accelerate the line restoration, reduce down-time, limit recovery and repair costs, and hence elevate the overall availability and reliability of the transmission system. In order to capture DC-side fault transients for protection and fault location applications, measuring equipment is required to be placed on HVDC installations. This paper focuses primarily on reviewing the available technologies from the perspective of enabling protection, fault location and automation applications in HVDC systems. The review constitutes a mapping of protection and fault location functions, against the available voltage and current measuring technologies, ultimately unlocking insights for selecting measuring equipment based on the desirable characteristics of protection and fault location systems. The review also revealed that the frequency characteristics of each sensing scheme, primarily refers to the bandwidth of the primary sensor, whereas the overall bandwidth of the complete measuring scheme may be further restricted by the secondary converter and corresponding data acquisition system and signal processing electronics. It was also identified that the use of RC voltage dividers has prevailed for voltage measurements for HVDC applications, due to their superior advantages. The choice of a suitable device for current measurement, depends mainly on the fault detection method used and the frequency range it operates. In particular, the review revealed that fault detection and protection methods are mainly concentrated in a frequency spectrum ranging from a few kHz to 100 kHz, while fault location methods require measurements with a frequency range from 100 kHz up to 2 MHz.

Multi‐vendor interoperability in HVDC grid protection: State‐of‐the‐art and challenges ahead

“…Compensated resistivecapacitive (RC) dividers are the main technology used for HVDC voltage measurements [58]. NCITs used for HVDC applications can provide a bandwidth up to a few MHz, which is considered sufficient for HVDC grid protection [58,59].…”

“…Zero‐flux sensors, hybrid electro‐optical combined with shunt and Rogowski coil, and fibre optical sensors are the technologies primarily used for HVDC current measurements. Compensated resistive‐capacitive (RC) dividers are the main technology used for HVDC voltage measurements [58]. NCITs used for HVDC applications can provide a bandwidth up to a few MHz, which is considered sufficient for HVDC grid protection [58, 59].…”

Technical feasibility of Power Flow Controllers for HVDC grids

“…Hence, they provide inherent insulation which is important for high voltage applications. They commonly rely on the Faraday effect and several manufacturers, such as ABB or GE, provide this kind of technology [28]. These sensors can be installed in the PFC platform and they can send the optic signals using the fiber optics to the controller station at ground potential.…”

“…Regarding the HVDC pole-to-ground voltage measurement, if it is needed, the state of the art is based on RC dividers [28]. In case of requiring the measurement of the PFC capacitors (some kV at high potential), a similar approach to the one applied to the capacitors of the MMC submodules can be considered (also some kV at high potential), where their voltage is measured and sent to the controller at ground level via fiber optics [18].…”

Buck Converter Current Measurement Using Differential Amplifier

“…The acquisition and accuracy of input current signals which are given to the compensation system is a basic and mandatory parameter in order to deliver the better control as per system requirements. There are different types of technologies are available to measure the current [3,4] and a suitable technology can be selected based on the isolation, power dissipation, measurement current level, system size, component count and costing requirements. Along with those requirements and considerations the system accuracy will be final product of any measurement techniques and extreme efforts are made to reach the maximum accuracy and minimum error.…”