3　Basic Requirements for Power Gird Connection

3.0.1　The design in respect of connection of shunt capacitor installations into the power grid shall be based on the principle of overall planning，reasonable layout，compensation by layers and zones and local balance in order to determine the optimal compensation capacity and distribution mode.

3.0.2　The installed capacity of capacitors in a substation shall be determined through calculations according to the reactive power planning of the local power grid and relevant regulations in the current national standards，and may be estimated based on the transformer capacity in accordance with the relevant regulations.The installed capacity of a user's shunt capacitors shall meet the requirement of local balance.

3.0.3　The capacity of sub-banks of shunt capacitors as determined shall conform to the following requirements:

1　During the switching of capacitor sub-banks，the busbar voltage fluctuation shall meet the requirements of current national standards and accommodate the adjustment and control of reactive power and voltage of the system.

2　When capacitor sub-banks are combined to provide various capacities，the capacity at which resonance would occur shall be prevented in order to avoid severe harmonic amplification and resonance.Harmonics of any orders generated as a result of the connection of capacitor branches in busbar at any side shall not exceed the limits as specified in the current national standard GB/T 14549 Quality of Electric Energy Supply-Harmonics in Public Supply Network.

3　The capacity causing resonance may be calculated from:

Where:Qcx——capacitor capacity causing a resonance at the nth harmonic（Mvar）；

Sd——busbar short-circuit capacity at the location where the shunt capacitor installation is placed（MVA）；

n——harmonic order，i.e.，the ratio of harmonic frequency to power grid fundamental frequency；

K——reactance ratio.

3.0.4　The shunt capacitor installation should be arranged at the main load side of a transformer.If conditions do not permit，it may be installed at the LV side of a three-winding transformer.

3.0.5　In cases where no HV loads are arranged in a distribution substation，the shunt capacitor installation should not be placed at the HV side.

3.0.6　The location and installed capacity of LV shunt capacitor installations shall be determined based on the principles of distributed compensation and local balance，ensuring that no reactive power would be inversely fed into the power grid.