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If the relay setting is determined to be below the apparent impedance it is determined that the fault is within the zone of protection. When the transmission line length is too short, less than 10 miles, distance protection becomes more difficult to coordinate. In these instances the best choice of protection is current differential protection.
The time interval between the instant pick-up value and the closing contacts of the relay is very low. It has low operating time and starts operating instantly when the value of current is more than the relay setting. This relay operates only when the impedance between the source and the relay is less than that provided in the section. [33]
A time–distance diagram is a chart with two axes: one for time, the other for location. The units on either axis depend on the type of project: time can be expressed in minutes (for overnight construction of railroad modification projects such as the installation of switches) or years (for large construction projects); the location can be (kilo)meters, or other distinct units (such as ...
21 - Distance Relay; 21G - Ground Distance; 21P - Phase Distance; 22 – Equalizer Circuit Breaker; 23 – Temperature control device, Heater; 24 – Volts per Hertz Relay (in some old analog applications, a 59 and an 81 device would be chained together as a 59/81 to implement the equivalent of V/Hz protection) 25 – Synchronizing or ...
The distance to the reflecting impedance can also be determined from the time that a pulse takes to return. The limitation of this method is the minimum system rise time. The total rise time consists of the combined rise time of the driving pulse and that of the oscilloscope or sampler that monitors the reflections.
In many cases, it is possible to design a relay logic diagram directly from the narrative description of a control event sequence. In general, the following suggestions apply to designing a relay logic diagram: 1. Define the process to be controlled. 2. Draw a sketch of the operation process. Make sure all the components of the system are ...
A relay allows circuits to be switched by electrical equipment: for example, a timer circuit with a relay could switch power at a preset time. For many years relays were the standard method of controlling industrial electronic systems. A number of relays could be used together to carry out complex functions (relay logic). The principle of relay ...
IEC 60255 Measuring relays and protection equipment; IEC 60258 Direct acting recording electrical measuring instruments and their accessories; IEC 60261 Sealing test for pressurized waveguide tubing and assemblies; IEC 60263 Scales and sizes for plotting frequency characteristics and polar diagrams; IEC 60264 Packaging of winding wires