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IEEE Std C62.72a-2020 pdf free download
IEEE Std C62.72a-2020 pdf free download.IEEE Guide for the Application of Surge-Protective Devices for Use on the Load Side of Service Equipment in Low-Voltage (1000 V or Less, 50 Hz or 60 Hz) AC Power Circuits Amendment 1: SPD Disconnector Application Considerations and Coordination.
Circuit breakers arc available with different sense circuits that offer a variety of time current characteristics.
Different circuit breaker types include those used for branch locations and those for usc in a specific point of use application. Circuit breakers that are used in branch locations are evaluated according to national codes and standards. For example, within the US, they arc tested in accordance with UL 489 [B 10]. Circuit breakers evaluated to UL 489 are intended for use anywhere in the electrical distribution system where they are applied within their specified ratings. Circuit breakers evaluated to UL 489 are capable of interrupting numerous overload conditions without degradation (see UL 489 for details) depending on the characteristics of the overload condition and that of the circuit breaker. Refer to IEEE Std 1458 for factors on detecting the end of life of the MCCB.
Circuit breakers that are intended for specific loads are evaluated to UL 1077 [131 IJ. Circuit breakers evaluated to UL 1077 are intended to be used for specific loads, not for branch locations, and arc generally installed as convenience circuit breakers within control cabinets or industrial machines. Circuit breakers evaluated to UL 1077 are capable of intemipting short-circuit currents only one time without creating a defined safety hazard.
Low-voltage circuit breakers can also be identified by the type of sensing mechanism. Common types of’ circuit breaker sense mechanisms arc thermal, magnetic, thermal-magnetic. hydraulic-magnetic, and electronic trip.
Circuit breakers that use a thermal sense mechanism detect overload currents by use of’ a bi-metallic strip. As current increases through the bi-metallic strip, the temperature increases. The bi-metallic strip is connected to the trip mechanism of the circuit breaker to ensure that all phases connected are opened once an overload has existed for a predetermined period of time, which is determined by the components used by the circuit breaker manufacturer. Thermal type circuit breakers have better response to overload currents than short-circuit currents. Thermal circuit breakers have limited use in applications where high ambient temperatures exist. One type of thermal element may be external to the device that it is protecting. If the thermal device is not located in the same location as the device that it is protecting, it must be compensated.
Magnetic circuit breakers use a form of an electromagnet as the sensing mechanism to determine the overload or short-circuit currents that are present. As the current through the electromagnet increases, the force increases. When the overload or short-circuit current has existed for a predetermined period of time, the trip mechanism of the circuit breaker activates opening all connected poles or phases. Magnetic-type circuit breakers have a better response to short-circuit currents than overload currents.IEEE Std C62.72a-2020 pdf free download.
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