Utilizing microwave continuous-wave Doppler radars to wirelessly detect mechanical vibrations have been attracting more and more interests in recent years. In this paper, aiming to solve the null point and nonlinear issues in small-angle approximation-based Doppler radar sensors and eliminate the codomain restriction in the arctangent demodulation approach, we propose and investigate an extended differentiate and cross-multiply (DACM) algorithm. With an additional accumulator, the noise performance of the original DACM algorithm is improved. Moreover, the amplitude information of the vibration can be directly retrieved from accumulation without involving any distance-dependent issue. Experimental validations show that the proposed algorithm can fully recover the vibration patterns with the measured noncalibrated amplitude agreeing well with the known precalibrated data. Application examples of mechanical fault detection and human vital sign detection are demonstrated, showing a wide range of potential applications of this algorithm.

Noncontact Distance and Amplitude-Independent Vibration Measurement Based on an Extended DACM Algorithm

The deployment of Artificial Neural Networks (ANNs) in safety-critical applications poses a number of new verification and certification challenges. In particular, for ANN-enabled self-driving vehicles it is important to establish properties about the resilience of ANNs to noisy or even maliciously manipulated sensory input. We are addressing these challenges by defining resilience properties of ANN-based classifiers as the maximum amount of input or sensor perturbation which is still tolerated. This problem of computing maximum perturbation bounds for ANNs is then reduced to solving mixed integer optimization problems (MIP). A number of MIP encoding heuristics are developed for drastically reducing MIP-solver runtimes, and using parallelization of MIP-solvers results in an almost linear speed-up in the number (up to a certain limit) of computing cores in our experiments. We demonstrate the effectiveness and scalability of our approach by means of computing maximum resilience bounds for a number of ANN benchmark sets ranging from typical image recognition scenarios to the autonomous maneuvering of robots.

Maximum Resilience of Artificial Neural Networks

A device for attaching to an electric power line conductor includes an electrically conductive housing with an opening for accepting the power line conductor and configured to be grounded to the power line conductor. At least one magnetic core is configured to surround the power line conductor and power a power supply electronics module. An ambient temperature measuring assembly is mounted inside and near the bottom of the electrically conductive housing. The ambient temperature measuring assembly is thermally insulated from the housing for thermally separating the ambient temperature measuring assembly from the housing.

Portable self powered line mountable device for measuring and transmitting ambient temperature

With the high penetration of distributed generations (DGs), the conventional radial distribution network is becoming an active distribution network (ADN). It has the characteristics of multisource, multibranch, bidirectional power and fault current flow, as well as weak infeed. To provide effective protection for such a network, a novel current differential protection scheme, together with new implementation technology, is proposed in this paper. In this scheme, instead of using phase currents, a positive-sequence fault component (PSFC) is introduced into the differential protection. By building the PSFC equivalent circuit of the ADN, the distribution characteristic of PSFC within the ADN is theoretically analyzed in detail, especially for the case when the ADN contains inverter interfaced DGs. The PSFC-based differential protection criteria for different types of feeder are then established and simulated. To put the scheme into practice, data self-synchronization and peer-to-peer communication techniques are established. Based on this principle and using an advanced hardware platform, a protection prototype is successfully developed and tested. The test results verify the feasibility of the proposed protection scheme.

Principle and Implementation of Current Differential Protection in Distribution Networks With High Penetration of DGs

Ease of integration of the variable speed diesel generators resulting in substantial reduction of the fuel consumption is the key motivation for the development of the dc shipboard power system (SPS). One of the impediments to the widespread adoption of the dc SPS, however, has been the lack of comprehensive fault management strategies during the short-circuit faults. Such strategies comprise of fault detection, fault isolation, and reconfiguration of dc SPS. In the existing literature, all these aspects of fault management are dealt independently and mostly assuming ideal conditions. All the strategies are of utmost importance and it is needed to study them under a common framework which is the aim of this paper. This paper starts with a brief discussion on the characteristics of dc SPS along with recent modeling techniques. Subsequently, this paper describes the short-circuit fault studies, fault characteristics, and protection requirements. Finally, this paper outlines the working principle, advantages, and limitations of the fault detection, isolation, and reconfiguration strategies developed for the dc power system and analyzes their suitability to the dc SPS. This paper is concluded by identifying the future research trends needed for the development of the short-circuit fault management strategies of dc SPS for critical marine missions.

Short-Circuit Fault Management in DC Electric Ship Propulsion System: Protection Requirements, Review of Existing Technologies and Future Research Trends

Overcurrent relays are widely used for power systems protection. Transmission side uses more directional type relays, while distribution systems, e.g., radial and ring-main subtransmission systems use nondirectional types. The fault direction may be forward (between relay and grid), or reverse (between relay and source), the normal power flow being from source to the grid. Traditional directional overcurrent relays utilize the reference voltage phasor for estimating the direction of the fault. This requires measurement of both current and voltage using respective sensors. This makes the directional overcurrent relays more costly than the nondirectional type. In this paper, a novel current-only directional detection possibility is highlighted along with theoretical, test signal analysis, challenges and associated solutions. Possible utilizations of the current-only directional relay in the distribution side protection are described, which is a key focus area for enabling the smart grid.

Current-Only Directional Overcurrent Protection for Distribution Automation: Challenges and Solutions

Overcurrent relays are widely used for protection of power systems, directional ones for transmission side, and nondirectional ones for distribution side. The fault direction may be forward (between relay and grid), or reverse (between relay and source), the normal power flow being from source to the grid. Known directional overcurrent relays rely on a reference voltage phasor for estimating the direction of the fault, requiring both current and voltage sensors. This increases the cost of the relays, prohibiting the utilization of such relays in the distribution side protection and automation, which is going to be a key part in the smart grid initiative. In this paper, a novel current-only directional detection possibility is highlighted.

Current-Only Directional Overcurrent Relay

Inverse tangent or arctangent function has many applications, for example, in estimating the phase angle of complex number utilized in electrical ac circuit analysis, power systems analysis, etc. Therefore, fast and accurate computation of the arctangent function is of great importance. Implementation of the arctan or atan2 using series expansions is accurate when computational cost is not an issue. However, for embedded applications such implementations cannot be used. As alternative, different approximations are proposed. In this paper, we present an efficient implementation using look-up table with 101-points. The accuracy is then increased by linear interpolation. The arctangent computation is extended to four quadrant operation using particular properties of arctan. The proposed scheme is implemented in a 60MHz microcontroller platform, typical for embedded applications. Comparative evaluations show that the accuracy of the proposed method is better than the reported approximation techniques. The time consumption of the proposed method is significantly less than that of the library function of the same microcontroller platform.

Fast computation of arctangent functions for embedded applications: A comparative analysis

Overcurrent relays are widely used for power systems protection. Transmission side uses more directional type relays, while distribution systems, e.g., radial and ring-main subtransmission systems use non-directional types. The fault direction may be forward (between relay and grid), or reverse (between relay and source), the normal power flow being from source to the grid. Traditional directional overcurrent relays utilize the reference voltage phasor for estimating the direction of the fault. This requires measurement of both current and voltage using respective sensors. This makes the directional overcurrent relays more costly than the non-directional type. In this paper, a novel current-only directional detection possibility is highlighted along with theoretical and test signal analysis. Possible utilization of the current-only directional relay for intelligent directional protection in the distribution systems are described. Directional protection for distribution systems is a key focus area for enabling the smart grid.

Smart distribution protection using current-only directional overcurrent relay

A method of determining a fault direction parameter of a fault on an AC transmission line of a power distribution system relative to a measurement location of the transmission line. The method includes measuring a time-dependent AC current of the transmission line at the measurement location to obtain time-domain current data indicative of the measured current, obtaining a time of the fault on the transmission line, identifying first and second times by identifying a periodically re-occurring feature of the current data, such that the fault time is between the first and second times, extracting, from the current data, an offset indicative parameter indicative of a time offset of the current at the fault time and between the first and second times, calculating an offset direction parameter by comparing the offset indicative parameter to a non-offset indicative parameter, and establishing the fault direction parameter based on the offset direction parameter.

Vishal H. Shah

Papers

Current-Only Directional Overcurrent Protection for Distribution Automation: Challenges and Solutions

Current-Only Directional Overcurrent Relay

Fast computation of arctangent functions for embedded applications: A comparative analysis

Smart distribution protection using current-only directional overcurrent relay

Fault direction parameter indicator device and related methods