Fumio Kawano

An Optically-Interrogated Rogowski Coil for Passive, Multiplexable Current Measurement

We report on the design and implementation of a novel hybrid electro-optical sensor for the measurement of electric current. A fibre Bragg grating is utilized to passively interrogate an air-cored coil via a low-voltage piezoelectric multilayer stack. Peak Bragg reflections are strain-tuned by the Rogowski coil/piezoelectric transducer combination, allowing primary current reconstruction to be performed remotely and without active electronics at the sensor. The preliminary embodiment demonstrates long-distance, passive measurement of current for metering and protection relaying applications, and retains the fiber transducers capability for serial multiplexing.

Distributed optical distance protection using FBG-based voltage and current transducers

We describe a novel approach to distance protection using optical fiber sensors. An optical protection system utilizing two pairs of hybrid fiber-optic voltage and current sensors is presented, allowing for distributed, multiplexed measurement of voltage and current, and hence impedance, at multiple points on a transmission network. Three separate phase-to-earth fault scenarios are tested in order to demonstrate the schemes successful operation in laboratory conditions. The deployment of the proposed scheme in electrical power transmission and distribution systems may allow for novel and flexible protection architectures while reducing the complexity of installation and isolation requirements in the high-voltage environment as well as the elimination of the requirement for a dedicated communication media to implement multi-ended schemes. The possibility of hybrid optical/conventional techniques also exists.

Distributed photonic instrumentation for power system protection and control

We report on recent developments in hybrid optical protection schemes that make use of passive fiber Bragg grating-based transducers for the distributed measurement of voltage and current. In addition to the details of the hybrid optical sensor technology, and its full integration with a commercial busbar protection relay, we report on the first-time laboratory demonstration of a centralized three-ended unit protection scheme featuring hybrid optical sensors capable of passive and wide-area coverage. Furthermore, we discuss the impact of this technology on present and future protection applications that may be improved or enabled by the proposed scheme.

Development of prototype wide-area monitoring, protection and control (WAMPAC) systems based upon international standards

Recently, the significance of Wide-Area Monitoring, Protection and Control (WAMPAC) has increased as it promises to provide a countermeasure to possible power system instability phenomena. The standardization of communication interfaces, that are able to open up the possibility of integrating a wide variety of sub systems, is becoming increasingly important in enabling the build of a standard WAMPAC system. In Japan, WAMPAC systems have been used for power system stabilization for many years and significant experience has been gained in the application of this technology. We have recently conducted a review of our in-service experience of WAMPAC systems and we have also examined current and draft international standards in order to identify the key standards pertinent to WAMPAC systems. In this paper, the authors introduce a proposal detailing a system configuration for a WAMPAC system based upon the international standards identified. The paper also discusses the prototype systems that were developed along with some sample demonstration scenarios.

Improved fault location through analysis of system parameters during auto-reclose operations on transmission lines

This paper describes a novel single-ended impedance-based fault-location method for transmission lines, which is based upon the analysis of voltage and current during discrete system states that arise during the operation of single- and three-phase autoreclose schemes. A fault-location estimation algorithm, using the data measured during various system states and is capable of locating the fault types involving one fault resistance (i.e., single-line-to-ground fault or line-to-line fault), is developed and presented. The proposed fault-location technique is shown to have high accuracy; results are presented and compared with the well-established Takagi method and the performance of the algorithm is analyzed and discussed. The proposed technique can reduce or negate limitations associated with conventional single-ended methods and can also estimate other factors associated with the fault (e.g., fault resistance and remote source impedance). In addition, it is a potentially economic solution, since it is relatively straightforward to implement on a standard protection relay hardware platform. The proposed method is demonstrated using Electromagnetic Transients Program/Alternate Transients Program simulation models for a variety of different cases. This paper concludes with an overview of ongoing and future work that has the intention of moving the work forward toward implementation within commercially available relay hardware.

Distributed photonic instrumentation for smart grids

Photonic sensor networks possess the unique potential to provide the instrumentation infrastructure required in future smart grids by simultaneously addressing the issues of metrology and communications. In contrast to established optical CT/VT technology, recent developments at the University of Strathclyde in distributed point sensors for electrical and mechanical parameters demonstrate an enormous potential for realizing novel and effective monitoring and protection strategies for intelligent electrical networks and systems. In this paper, we review this technology and its capabilities, and describe recent work in power system monitoring and protection using hybrid electro-optical sensors. We show that wide-area visibility of multiple electrical and mechanical parameters from a single central location may be achieved using this technology, and discuss the implications for smart grid instrumentation.

Faulted phase selection function based upon impedance comparison in a distance protection relay

The distance protection relay is widely used around the world for the protection of transmission and distribution networks and it is especially essential in its application within bulk power systems. The faulted phase and the fault point on the power line must be determined by the relay with great certainty. In this paper, we propose a unique method to enhance the faulted phase selection function that uses impedance. In this method, an impedance comparison technique, the faulted phase is determined by identifying the minimum of the phase-to-phase impedances based upon the rule that a phase-to-phase fault impedance becomes a minimum for two-phase faults. In order to demonstrate the validity of the new technique, both the conventional method (voltage comparison method) and the proposed method are evaluated in detail for various test cases utilizing Toshiba distance protection relays, GRZ100 and a Real Time Digital Simulator (RTDS). These test cases include evolving faults to other phases and cross-country faults involving parallel double circuit transmission lines. The results show that the conventional method does not always have sufficient capability to discriminate the faulted phase correctly for the cross-country fault cases which have no healthy phases, on the other hand, the impedance comparison method demonstrates superior performance for all of the test cases. The proposed impedance comparison method is shown to be a promising method to enhance the faulted phase selection function for the distance protection relay and has been put to practical use successfully.