Printed Circuit Board Rogowski Coil Research Articles

Innovative Differential Protection of Power Transformers Using Low-Energy Current Sensors

Traditional differential protection systems are applied on large power transformers using current transformers (CTs). However, because of high secondary currents (often exceeding 100 kARMS), differential protection systems for electric arc furnace transformers have not been applied in the past due to the lack of commercially available CTs. This paper will present differential protection systems that have been in use for many years using Rogowski coil current sensors. These protection systems use high-precision printed circuit board Rogowski coil current sensors. This paper reviews the characteristics, designs, and application of these Rogowski coil sensors for advanced protection, control, and metering systems with new multifunction relays. This paper compares performance characteristics of new solutions based on Rogowski coil sensors with the conventional differential protection systems based on CTs, demonstrating that the new systems do not have the limitations of conventional technology. Operating experience from several site applications is included.

Positional Error Analysis of PCB Rogowski Coil for High Accuracy Current Measurement

Geometrical, physical, and electrical parameters have influences on the precision of printed circuit board Rogowski coils (PCBRCs). This paper outlined operating principles and properties of PCBRCs. Two kinds of positional sensitivities between current conductor and PCBRC are analyzed, and mathematical models and formulas for error computing are established and derived. The roles of some critical geometrical parameters are characterized and verified by experiment. These methods can be used to define structure parameters of PCBRC for precise current measurement applications.

The printed circuit board Rogowski coils for plasma current measurements on the J-TEXT tokamak

Compared with the conventional Rogowski coils made by winding wire loops, a printed circuit board (PCB) based on Rogowski coils has some favourable advantages for current measurements, such as large effective area, good linearity, high frequency response, precise geometry and thin profile. This type of Rogowski coil has been widely applied in electrical systems as the current sensor. Nevertheless, the PCB Rogowski coils are introduced for the first time to measure the plasma current on the Joint Texas Experimental Tokamak (J-TEXT). The measurements have shown that this novel PCB Rogowski coil works perfectly and is very suitable for studies of disruption, equilibrium reconstruction, etc.

Rogowski Sensor for Plasma Current Measurement in J-TEXT

Rogowski coil is very useful in transient current measurement. Rogowski sensor consisting of Rogowski coil and integrator is one of the most important diagnostic instrumentations in Tokamak. In recent years, new structures of Rogowski coil based on printed circuit board (PCB) are developed to replace traditional handmade Rogowski coil for more excellent accuracy, better temperature stability, more accordant mutual-inductance, more symmetrical windings, and other advantages. However, the existing structures of Rogowski coil based on PCB are useless in Tokamak because the required Rogowski coil installed on the vacuum vessel should have long diameter and little space. This presentation provides a new twin-loops Rogowski coil (TRC) consisting of several PCB strips. TRC has all the advantages of existing PCB Rogowski coils and can meet the limited space requirement in Tokamak at the same time. A special experiment is carried out to prove that the mutual-inductance of TRC is immune to the variation of center position of plasma current. Moreover, a differential long-term integrator is designed to cooperate with the TRC. Two switches are used in the integrator to release the remaining electric charges on integrating capacitors once the measurement is over. Then, the error accumulation of integrator is canceled in repetitious measurements. The designed new Rogowski sensor can be used to measure long pulse current below 1 s.