Category: Introduction to Static Relays

Polarised Relay

Polarised Relay: This Polarised Relay is very frequently employed where operation is required in two directions. in a d.c. polarized relay contact A is closed when current in the operating winding flows in one direction contact B will be closed if the current direction reverses as shown in Fig. A.1.16(b). An exactly similar operation can […]

Time Delay Circuit

Time Delay Circuit: Time Delay Circuit – Several choices are available in the selection of suitable circuits for obtaining time delay depending on the magnitude of the time delay required. Delays of the order of microseconds can be obtained by what are known as delay lines or cables usually employed in communication systems. The delay […]

Level Detector

Level Detector: Schmitt trigger or level detector circuits are very often employed in static relay circuits as a final stage before the trip coil circuit of the circuit breaker. The name level detector is derived from the fact that the circuit operates abruptly when the input level exceeds a predetermined value. This is shown in […]

Types of Relay Elements

Types of Relay Elements: The Important Types of Relay Elements or also called Electromagnetic Types are 1.Induction Disc Relay The shaded pole type gives the most effective form of an electromagnet since it has the following: Higher torque/VA. A single coil which permits use of larger wire. Time-current characteristics which can be controlled easily by varying […]

Influence of Static Protective Relays

Influence of Static Protective Relays: Influence of Static Protective Relays on the associated equipment like current transformers, voltage transformers, etc, Current Transformers Burdens on current transformers have a great influence on their design and for a long time the problems of transient performance have given way to a progressive reduction of the relay burdens. However, […]

Transistor Switch Circuit

Transistor Switch Circuit: Transistor Switch Circuit – The characteristics of modern transistors are specially suited to the functional requirements mentioned above. These along with the other Semiconductor production of static relays. The properties particularly useful in the realization of the functional requirements are amplification, switching characteristics, sensitivity, high speeds of response, flexibility of design and […]

Characteristic Functions of Protection Relay

Characteristic Functions of Protection Relay: Characteristic Functions of Protection Relay elements using different operating principles. These principles and design criteria determine how well the basic function is performed and how in practice it deviates from the ideal. Static relays can achieve such a high performance that the departures from the ideal in practice are negligible. […]

Generator Transformer Protection

Generator Transformer Protection: Generator Transformer Protection – Protective relays, being component parts of electrical switchgear, should be closely associated with the control section of such systems, e.g. indicating and signalling systems. Thus the signalling and indicating systems must also be designed on a static basis. The plug in type modular chassis has been widely adopted already in electronic regulating and control equipment. […]

Overcurrent Relay

Overcurrent Relay: Overcurrent Relay – In a three phase system of relays, it is economical to build it on a single phase basis. Thus there will be three converter elements, one for each phase, but thereafter the rest of the circuits (e.g. measuring element, output element, etc.) will be common to all the three circuits. […]

Types of Protective Relays

Types of Protective Relays: Basically, Types of Protective Relays are analogue-binary signal converters with measuring functions. The variables such as current, voltage, phase angle or frequency and derived values obtained by differentiation, integration or other arithmetical operations, appear always as analogue signals at the input of the measuring unit. The output will always have a […]