IEEE C57.131-2012 pdf download IEEE Standard Requirements for Tap Changers
main switching contacts: For resistance-type load tap changers (LTCs), a set of contacts that has no transitionimpedance between the transformer winding and the contacts and makes and breaks current.
maximum rated step voltage: The highest value of rated step voltage for which the load tap changer is designed
maximum rated through current: The highest rated through current for which beth-the tap changer is designedemperature rise ef the eontaets and which forms the basis for all current-related tests the serviee duty test apply.
motor-drive mechanism: A driving mechanism which incorporates an electric motor and a control circuit.
number of inherent tap positions: The highest number of tap positions for half a cycle of operation for which anLTC is designed.
number of service tap positions: The number of tap positions for half a cycle of operation for which an load tapchanger (LTC) is used in a transformer.
NOTE–The above two terms,3-19 and 3-20, are generally given as the values of the relevant numbers, e.g, t l6positions.
They are, in principle, valid also for the motor-drive mechanism. When the term number of tap positions is used inconnection with a transformer, this always refers to the number of service tap positions of the LTC.
off-circuit tap changer: See: de-energized tap changer (DETC). on-load tap changer (OLTC): See L.oad tapchanger (LTC).
olus/minus operation: A winding arrangement in which one or the other end of the tapped winding is connectedby a reversing change-over selector to the main winding, and allows use of the taps in a buck or boost mode whentraveling through the tapping range
preventive autotransformer: An autotransformer (or center-tapped reactor) used in load tap changing andregulating transformers, or step-voltage regulators to limit the circulating current when operating on a position inwhich two adjacent taps are bridged, or during the change of taps between adjacent positions.
rated frequency: The frequency of the alternating current for which the load tap changer (LTC) isdesigned.
rated step voltage of a load tap changer: For each value of rated through current, the highest permissiblevoltage between tap changer terminal, that are intended to be connected to successive taps pesiiens. of thetransformer winding
NOTE–The rated step voltage refers to the voltage applied across the contacts during the service duty and breaking capacitytests. It therefore relates to the switching ability of the tap changer under load. The term rated step voltage does not applyto deenergized tap changers.
IEEE C57.131-2012 pdf download
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