IEEE Std 741-2017 pdf free download – IEEE Standard Criteria for the Protection of Class 1E Power Systems and Equipment in Nuclear Power Generating Stations.
4. General Design Criteria
4.1 As used in this document, protection refers to the sense, command, and execute features with their associated interconnections (IEEE Std 603- 1980 [ 181 7, provided to minimize equipment dam- age and any interruption of electrical service resulting from mechanical or electrical failures or other unacceptable conditions.
It includes equip- ment required to support the Class 1E power sys- tem in the performance of its safety function, and components whose function is to increase the availability and reliability of the safety-related equipment. The protection shall
4.1.1 Be capable of preventing failures in safety systems and equipment from disabling safety functions to below an acceptable level. Protection in one load group shall not respond to distur- bances in a redundant load group.
4.1.2 Be capable of operating the required devices upon detection of unacceptable condi- tions to reduce the severity and extent of electri- cal system disturbances, equipment damage, and potential personnel and property hazards.
4.1.3 Be capable of monitoring the connected power supply and, where an alternate supply is provided by the design, of automatically initiating a transfer or alerting the operator to manually transfer to the alternate power supply.
4.1.4 Be capable of providing indication and identification of the protective operations.
4.1.5 Be capable of being periodically tested to verlfy logic schemes and protective functions.
4.1.6 Be designed such that the availability of protection control power is monitored.
4.1.7 Be capable of being periodically tested to verify setpoints. This requirement is not applica- ble to fuses.
4.2 Those parts of the protection that have a safety function shall meet the requirements of IEEE Std 603-1980 [18] and IEEE Std 308-1980 [7]. Those parts of the protection whose function is nonsafety related shall be designed such that their failure does not degrade the Class 1E power system below an acceptable level.
4.3 Unless specifically identified in Section 5 of this document, redundant or coincident logic protection schemes within a division of the Class 1E power system are not required.
5. Principal Design Criteria and Requirements
5.1 AC Power Distribution Systems 5.1.1 Switchgear and Bus Protection
5.1.1.1 Refer to IEEE Std 141-1986 [4] and IEEE Std 242-1986 [6] for recommended prac- tices in application of overcurrent relays, direc- tional relays, differential relays for bus protection, and ground fault relaying. The protection systems for the ac distribution system should be coordi- nated in accordance with IEEE Std 242-1986 [6]. Refer to IEEE Std 142-1982 [5] for supplemen- tary information on ground protection practices.
5.1.1.2 If the power distribution system design cannot accommodate paralleling of bus supplies, or if paralleling can be allowed only under certain conditions, interlocks or procedu- ral restrictions shall be provided to restrict such paralleling. Consideration shall be given to the higher fault current that may exist during parallel operation when selecting protective devices.
5.1.2 Bus Voltage Monitoring Schemes. Bus voltage monitoring schemes that are used for disconnecting the preferred power source, load shedding, and starting the standby power sources are part of the protection and shall meet the cri- teria outlined below. Voltage monitoring schemes that are used only for alarms do not have to meet these criteria.
5.1.2.1 Bus voltage shall be detected directly from the Class 1E bus to which the standby power source is connected. Class 1E bus voltage moni- toring shall not be derived from a non-Class 1E bus.IEEE Std 741 pdf download.