GB/T 40596-2021 in English

GB/T40596-2021 specifies the technical measures for automatic low-frequency load reduction in the power system when there is an active power shortage, including device configuration principles, setting calculation methods and frequency dynamic process control requirements. The standard applies to the entire life cycle of system planning and design, production operation, and scientific research and manufacturing.

The standard recommends using the single machine with concentrated load model to calculate the frequency dynamic process (see Appendix B for details). Attention should be paid to the selection of key parameters:

• The system inertia constant only takes into account the generator set
• The load frequency adjustment coefficient is 1-3 (actual measurement is recommended)
• The spinning standby capacity is considered according to the most unfavorable situation

Power shortage calculation formula:
K=(P_L-P_R)/P_R
Where P_L is the load power and P_R is the remaining power generation power.

The standard clearly requires:

1. The basic round is set to 3-8 rounds + a special long delay round
2. The first round starting frequency ≤49.25Hz (large power grid)
3. Prioritize the removal of load branches that do not contain distributed power sources
4. The tripping setting of the pumped storage unit is higher than that of the first round

Typical round parameter configuration example:

According to the management process in Appendix A of the standard, it is recommended that:

• A three-level coordination mechanism should be established (regional-provincial-municipal)
• Frequency stability verification should be carried out regularly
• Important substations should be equipped with dual de-energizing devices
• The system for event retrospective analysis should be improved

Special reminder: For systems containing special power sources such as nuclear power and DC transmission, the low-frequency protection coordination must be separately verified according to Article 5.1(b) of the standard.