IEEE 741-2017 pdf free.IEEE Standard for Criteria for the Protection of Class 1 E Power Systems and Equipment in Nuclear Power Generating Stations.
For the purposes of this document, the following terms and definitions apply. The IEEE Standards Diciionarv Online and IEEE C37. IQOTM (B9j 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 satty limit is not exceeded.
anticipated overloads: Those values of motor current in excess of motor nameplate rating that arc 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 transtr to an alternate source (US. NRC Branch Technical Position, PSB-l [B 161). These protective relays monitor the Class I E safety bus voltages and automatically initiate the disconnection 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 successive stroking of the valve.
duty cycle time of a valve actuator: The time required tbr a valve to complete one stroke multiplied by the duty cycle.
DVR dropout setting: The voltage selpoint 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 1 E 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) undcrvoltagc protection scheme provided to detect loss of otisite power at the Class I E buses.
LVR dropout setting: The voltage setpoint of the loss of voltage relay (LVR) that causes the relay to actuate and automatically disconnect otisite power after the LVR voltage limit and LVR time delay limit is reached. Also, minimum voltage at which all Class 1 E loads are capable of running fhr a defined period of time.
nilnimuni required grid voltage: The minimum switchyard voltage required to maintain an operable preferred otYsite power supply such that the supply can perform its intended safety function per GIX’- 17. This requires the otIsite supply to have sufficient capacity and capability to perform its intended function, including 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 thereby causing separation from the otIsite power supply. valve actuator motor nominal current: The current that the motor is rated to carry for the duration of its rated
duty, commonly known as the motor nameplate current.
valve actuator motor nominal torque: The torque that corresponds to the valve actuator nominal current.
salve stroke: Complete travel distance of a valve from either fully open to fully closed position, or vice-versa.IEEE 741 pdf download.