IEEE 741-2017 pdf free downlaod – IEEE Standard for Criteria for the Protection of Class 1 E Power Systems and Equipment in Nuclear Power Generating Stations.
3. Definitions, abbreviations, and acronyms
3.1 Definitions
For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary Online and IEEE C37.100TM [B9] should be consulted for terms not defined in this clause.”
analytical limit: A limit of a measured or calculated variable, established by the analysis to ensure that a safety limit is not exceeded.
anticipated overloads: Those values of motor current in excess of motor nameplate rating that are expected to be realized during valve actuation due to the varying torque nature of the load.
degraded voltage relay (DVR): Undervoltage relays; part of the (second level of) undervoltage protection (with time delay) provided to protect the Class 1E equipment from damage or becoming unavailable upon transfer to an altermate source (US. NRC Branch Technical Position, PSB-1 [B16]). These protective relays monitor the Class 1E safety bus voltages and automatically initiate the disconnction of offsite power whenever the voltage setting and time delay limits have been exceeded.
duty cycle of a valve actuator: The duty cycle of a valve actuator consists of the number of valve strokes needed for its intended service. Plant operation or testing may require sucessive stroking of the valve.
duty cycle time of a valve actuator: The time required for a valve to complete one stroke multiplied by the duty cycle.
DVR dropout setting: The voltage setpoint of the degraded voltage relay (DVR) that causes the relay to actuate and automatically disconnect offsite power, after the DVR voltage limit and the DVR time delay limit is reached. Also, the minimum voltage at which all Class IE loads are capable of starting and running indefinitely.
DVR reset setting: The voltage value that causes the degraded voltage relay (DVR) to reset following relay initiation. If this voltage value is reached prior to DVR timeout, it will prevent automatic disconnection of offsite power.
loss of voltage relay (LVR): Undervoltage relays; part of the (first level of) undervoltage protection scheme provided to detect loss of offsite power at the Class IE buses.
LVR dropout setting: The voltage setpoint of the loss of voltage relay (LVR) that causes the relay to actuate and automatically disconnect fisite power after the LVR voltage limit and LVR time delay limit is reached.
Also, minimum voltage at which all Class 1E loads are capable of running for a defined period of time.
minimum required grid voltage: The minimum switchyard voltage required to maintain an operable pre ferred ffsite power supply such that the supply can perform its intended safety function per GDC-17. This requires the ofsite supply 10o have sufcient capacity and capabiliy 1o perform its intended function, inchuding
the ability to maintain voltage while accepting the accident loads It also requires the supply to safety-related loads without causing the DVR to time out and trip theeby causing sparation from the fisite power supply.
valve actuator motor nominal current: The currcnt that the motor is rated to carry for the duration ofits rated duty, commonly known as the motor nameplate current.IEEE 741 pdf download.