3.2　Technical Requirements on the Connection of Power Plant to the Power System

3.2.1　The connection of fossil fired power plants to the power system shall be designed based on the planning capacity,single unit capacity,power transmission direction,power transmission distance and their roles in the system,as well as under the principles that the grid structure and the single line diagram of power plants can be simplified,the voltage level,number of circuits of outgoing lines and network loss can be reduced,and the dispatching,and troubleshooting can be facilitated.

3.2.2　The voltage level at which the power plant is connected to the system shall meet the following requirements:

1　The power plant should not be connected to the system at more than two voltage levels.

2　The power plants of different construction scales shall be connected to the power grids at corresponding voltage levels according to their respective role and function in the system；the power plants built to serve local loads and those with a single-unit capacity of 600MW and below should be connected to 330kV and below power grids.

3　The main power plant having a large capacity built in the receiving-end system should be directly connected to the power grid with a one-level higher voltage.

4　For power plants supplying electricity outside the region,the units having a single-unit capacity of 600MW and above should be directly connected to the power grid with a one-level higher voltage.

3.2.3　The electrical equipment of power plants shall comply with the following requirements:

1　The breaking capacity of circuit breakers shall meet the technical requirements on the prospective short-circuit breaking current at the installation point.

2　In the case of a large-scale power plant located at a load center with a dense grid structure and connected to the grid at two voltage levels,the plant should not be installed with tie-transformers that may constitute an electromagnetic loop network.

3　The single line diagram of fossil fired power plants shall satisfy the operation requirements for open loop and disconnection from power grid.

4　The generator transformer shall comply with the following requirements:

1）The step-up transformers of power plants should be of off-circuit-tap-changing type.

2）If it is demonstrated that voltage regulation is necessary for the tie-transformers,on-load-tapchanging transformers may be used.

3）The rated tap and sub-taps of the main transformer shall be selected based on the long-term development of power flow in the system.

4）If more than one step-up transformers rated 220kV and below are installed in a power plant,one or two of them shall have the neutral points grounded.

5）At least one of the voltage transformers which are connected to each 110kV busbar shall have the neutral points grounded.

5　The necessity for installing high voltage shunt reactors in a power plant depends upon the requirements of limiting the power frequency overvoltage and secondary arc current,and preventing selfexcitation；as well as the requirements of system synchronization and reactive compensation.

6　For the units that transmit electric power over long distance and necessitate leading power factor operation,the voltage regulation mode of the HV auxiliary transformers connected to the generator end shall meet the relevant requirements.

7　For power plants nearby the DC converter station and the ones transmit electric power through series-compensated lines,it shall be necessary to study the sub-synchronous oscillation and resonance problems and take appropriate measures for suppressing them according to the study results.