Overcurrent Protection Relay in Power System: The technique of Overcurrent Protection Relay in Power System is still widely used as a means of detecting faults on distribution system and on transmission lines fed from one…
Basic Elements of Static Relay: The basic elements of a static relay are namely, Input Element: Mixing circuits are needed to sum the input signals in a convenient form. Semiconductor circuits are suited to the…
Coincidence Type Phase Comparator: The basic concept of phase comparison is simpler in that it is possible to deal with signals of equal strength whose coincidence (or noncoinecidence) is readily measurable. Considering two sinusoidal signals…
Phase Comparator Circuit: Phase Comparator Circuit technique is the most widely used for all practical directional, distance, differential and carrier relays. If the two input signals are S1 and S2 the output occurs when the…
Static Amplitude Comparator: If the two input signals are S1 and S2 the amplitude comparator gives positive (yes) output only if S2/S1 ≤ K (Fig. (11.1)), S1 is the operating quantity and S2 is the restraining…
Zero Crossing Detector Circuit: Zero Crossing Detector Circuit basically involves the sine to square wave conversion by a level detector circuit followed by a pulse circuit, which consists of one shot monostable circuit or a…
Sampling Circuits: Sampling Circuits is one which allows a comparison of instantaneous values derived at different instants of time, thereby dispensing with the need to phase shift and mix signals derived from the primary line…
Summation Device: Summation transformers and sequence networks as already discussed can combine a number of electrical quantities into a single quantity. The operational amplifier is commonly used as a mixer or summer and the Summation…
Square Wave Generators: Diode clippers can be used to remove the curved portion of the sinusoidal wave to give square waves. The operational amplifier together with an integrator, can be used to generate a square…
Smoothing Circuits: The rectified a.c. consists of a series of undirectional half waves of current or voltage. It is generally desirable to smooth this output. The various filters used for Smoothing Circuits are the conventional…
