Document: NRC Regulatory Guide
Document ID: 1731a882-b0c5-418d-b65e-55646c26be5c
Document Type: regulatory_guide
Title: 03/2007
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0703/ML070380553.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.9
CFR Part: 
CFR Title: 

Content:
one large connected load.) Frequency should be restored to within 2 percent of nominal in less than 60 percent of each load-sequence interval for a stepload increase, and less than 80 percent of each load-sequence interval for disconnection of the single largest load. Voltage should be restored to within 10 percent of nominal within 60 percent of each load-sequence interval. The acceptance value of the frequency and voltage should be based on plant-specific analysis (where conservative values of voltage and frequency are measured) to prevent load interruption. (A greater percentage of the load-sequence interval may be used if it can be justified by analysis. However, the load-sequence interval should include sufficient margin for the accuracy and repeatability of the load-sequence timer.) During recovery from transients caused by disconnection of the largest single load, the speed of the diesel generator should not exceed the nominal speed plus 75 percent of the difference between nominal speed and the overspeed trip set point, or 115 percent of nominal (whichever is lower). Furthermore, the transient following a complete loss of load should not cause the diesel generator speed to reach the overspeed trip set point. Rev. 4 of RG 1.9, Page 6 1.5 Emergency diesel generators should be designed so that they can be tested as described in Regulatory Position 2. The design should allow testing of the diesel generators to simulate the parameters of operation (e.g., manual start, automatic start, load sequencing, load shedding, operation time), normal standby conditions, and environments (e.g., temperature, humidity) that would be expected if actual demand were placed on the system. If prelubrication systems or prewarming systems designed to maintain lube oil and jacket water cooling at certain temperatures (or both) are normally in operation, this would constitute normal standby conditions for the given plant. 1.6 Design provisions should include the capability to test