Mukhtar Ahmad

Power system frequency deviation measurement using an electronic bridge

A very simple frequency-deviation measuring instrument that works on the principle of a two-arm bridge is described. The circuit was fabricated and tested in the laboratory. The results indicate good linearity between frequency deviation and voltage or pulse count over the normal range of power system frequencies. The same instrument along with a variable frequency supply can also be used to measure a capacitance or a resistance. >

A digital tachometer for measurement of very low speeds

An induction-type digital tachometer in which the number of pulses is proportional to the speed is described. Even for very low speeds the number of pulses is high, making it very suitable for extremely low speed measurement.

Electrochemical study of natural gas fueled electrodes for low temperature solid oxide fuel cell

Fuel cell is undoubtedly widespread energy conversion technology, which can convert fuel (biogas) energy into electricity. Solid oxide fuel cell (SOFC) is one of the best choices among the fuel cell’s family due to high efficiency and fuel flexibility. In this study, zinc-based nanostructured Mn0.20FexZn0.80−xOδ electrode materials were successfully developed by solid state reaction. The proposed materials have been characterized by XRD and SEM. The electrical conductivities have been examined by four-probe DC method in the temperature range of 300–600∘C, the maximum values were recorded and found to be 12.019 and 5.106 S/cm at natural gas and air atmosphere, respectively. The electrochemical performance has been measured employing NK-SDC electrolyte material and their current density versus voltage and current density versus power density (I-V and I-P characteristics) have been drawn. The maximum power density was found to be 170 mW/cm2 using natural gas as a bio-fuel over a temperature of 600∘C.

A simple scheme for loss angle measurement of a capacitor

This paper presents a very simple electronic circuit for direct measurement of loss angle of a leaky capacitor. The circuit used can directly provide loss angle or tan /spl delta/ in terms of a pulse count. The circuit uses very few components, requires no special supply, and is suitable for a large range of capacitor values.

A Potentiometric Transducer for the Measurement of Very Low Speeds

A simple circuit for the measurement of very low angular speeds is described. It uses a potentiometric transducer along with a modified astable multivibrator. Using an up-down counter the speed measured can also be displayed.

A Digital Frequency Relay For Over/under Frequency Detection

Under frequency relays are used to shed automatically certain portion of load whenever the system frequently falls to such a low level as to threaten the stability of the power system. In this paper a very simple digital frequency relay is proposed for this purpose. The main component of this relay is a simple digital frequency measurement circuit which gives better accuracy than present day available frequency delays. This relay can also be used for over frequency detection.

Measurement of Power System Frequency Deviation using a microprocessor

The measurement of power system frequency deviation is useful for the design of power system stabilizers, automatic load shedding systems and the monitoring of power station frequency. Here, a simple scheme using a 90° phase shifter is suggested. The scheme is suitable for implementation using a microprocessor.

A digital tachometer for fast detection of speed variation in kiln drives

Kiln drives in cement industries are required to run at very low speeds of 1/3 to 1.8 r.p.m.. To design a suitable control scheme for speed regulation of such motors, fast detection of speed variation is essential. An induction-type tachometer with digital output that can be used for this purpose is described.

Application of Doubly Fed Induction Motor in Power System State Measurements

In a large interconnected power system, any strategy for the control of transient modes after a major disturbance requires a fast and reasonably accurate measurement of power angle and speed or frequency deviations. These data are given to the controlling device for performing the corrective actions.

Improvement of transient stability by sequentially switched autoreclosing circuit breaker

Abstract Autoreclosing circuit breakers are frequently used to improve the transient stability limit of a power system. But the system may fail to maintain stability even after a successful reclosure for high values of prefault power transfer. A sequential switching scheme employing three fast-acting isolators in addition to the autoreclosing circuit breaker is suggested. It improves the transient stability limit of the transmission system considerably. A simple mathematical analysis reveals the extent of stability improvement. Complete constraint clauses have been formulated for the switching scheme and a block diagram of the logic circuit is presented. The proposed scheme finds its immediate application in a single circuit tie-line between two systems.