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A solid state relay (SSR) is an electronic switching device that switches on or off when an external voltage (AC or DC) is applied across its control terminals. They serve the same function as an electromechanical relay , but solid-state electronics contain no moving parts and have a longer operational lifetime.
Digital/numerical relays provide a front panel display, or display on a terminal through a communication interface. This is used to display relay settings and real-time current/voltage values, etc. More complex digital relays will have metering and communication protocol ports, allowing the relay to become an element in a SCADA system.
The schematic diagrams for relay logic circuits are often called line diagrams, because the inputs and outputs are essentially drawn in a series of lines. A relay logic circuit is an electrical network consisting of lines, or rungs, in which each line or rung must have continuity to enable the output device. A typical circuit consists of a ...
COMTRADE files are typically generated by Intelligent Electronic Devices , such as an electronic protective relay, in electrical substations during power systems disturbances. These IEDs monitor the electrical characteristics of the power system by digitally sampling measurements of the current , voltage , power , frequency , etc. at a high speed.
Modern microprocessor-based timing relays provide precision timing over a great range. Some relays are constructed with a kind of "shock absorber" mechanism attached to the armature, which prevents immediate, full motion when the coil is either energized or de-energized. This addition gives the relay the property of time-delay actuation.
A 'data link module' (DLM) is the interface between the data link and the TFMs. A DLM has a blue label. For transmission over longer distances, fibre-optic cable and pulse-code modulation may be used. Another type of module, the 'long distance terminal' (LDT) is available for this purpose. An LDT has a gold coloured label.
A rare gold coin was donated to a Salvation Army Red Kettle in Washington, Pennsylvania, by an anonymous good Samaritan due to holiday foot traffic. Coin expert weighs in.
Current and voltage transformers to step down the high voltages and currents of the electrical power system to convenient levels for the relays to deal with; Protective relays to sense the fault and initiate a trip, or disconnection, order; Circuit breakers or RCDs to open/close the system based on relay and autorecloser commands