阅读说明：本技术 一种用于抑制空载长线路过电压的负荷量计算方法 (Load calculation method for suppressing no-load long line overvoltage ) 是由 刘志坚 王雁红 余进 徐慧 晏永飞 周于尧 王一妃 余莎 李鹏程 赵浩益 于 2019-09-19 设计创作，主要内容包括：本发明公开了一种用于抑制空载长线路过电压的负荷量计算方法,属于高电压电网技术领域。本发明首先搭建仿真模型,进行高压输电线路空充实验；根据输电线路电容效应导致的末端电压升高值获得所需求解的有功负荷、无功负荷。本发明能够使调度人员根据想要的输电线路工频过电压来计算出负荷量,而线路末端带适量负荷合闸可使得操作过电压、工频过电压幅值在合理范围内,波动小,且有利于消减毛刺现象,对骨干网架黑启动方案的制定、校验、电压波形的识别及黑启动过程中的过电压的预测具有较高参考价值。(The invention discloses a load quantity calculation method for restraining overvoltage of a no-load long line, and belongs to the technical field of high-voltage power grids. Firstly, building a simulation model, and carrying out a high-voltage transmission line empty charge experiment; and obtaining the active load and the reactive load to be solved according to the terminal voltage increase value caused by the capacitance effect of the power transmission line. The invention can enable a dispatcher to calculate the load according to the desired power frequency overvoltage of the power transmission line, and the tail end of the line is provided with a proper amount of load for switching on, so that the amplitude of the operation overvoltage and the power frequency overvoltage are in a reasonable range, the fluctuation is small, the burr phenomenon is reduced, and the invention has higher reference value for formulation and verification of a backbone network frame black start scheme, identification of voltage waveform and prediction of overvoltage in the black start process.)

1. A load calculation method for suppressing an over-voltage of a no-load long line is characterized in that: the method comprises the following steps:

s1, building a simulation model, and performing a high-voltage transmission line empty charge experiment; the model comprises the following main modules: the device comprises a three-phase constant voltage source, a three-phase transformer, a three-phase distribution parameter circuit, a three-phase voltage and current measuring module, a three-phase circuit breaker and an oscilloscope;

s2, calculating delta U of the air charging line:

ΔU＝(P′₂R+Q′₂X)/U₁

in the formula: delta U is a terminal voltage increase value caused by the capacitance effect of the power transmission line; p'₂＝0.5×G×U₂ ²，Q′₂＝-0.5×B×U₂ ²，U₁For line head end voltage, U₂The voltage at the tail end of the line, G is the conductance of the line, B is the susceptance of the line, R is the resistance of the line, and X is the reactance of the line;

step3, calculate P_L、Q_L：

In the formula: u shape_xFor a predetermined line end voltage, P_LFor active load to be solved, Q_LFor reactive loads to be solved, P_L＝aQ_LAnd a is a coefficient.

2. The load amount calculation method for suppressing an unloaded long line overvoltage according to claim 1, characterized in that: the high voltage refers to 220kV and 110kV voltage levels.

3. The load amount calculation method for suppressing an unloaded long line overvoltage according to claim 1, characterized in that: r ═ R₁l、X＝x₁l、G＝g₁l、B＝b₁l; wherein r is₁Resistance per unit length of line, x₁Reactance per unit length of line, g₁Conductance per unit length of line, b₁Is the susceptance per unit length of the line.

Technical Field

The invention relates to a load quantity calculation method for restraining overvoltage of a no-load long line, and belongs to the technical field of high-voltage power grids.

Background

When a large-area power failure occurs in an electric power system, not only can great economic loss be brought to a power failure area, but also more importantly, the life order of people cannot be guaranteed after the accident. According to the national power system safety and stability control technical guide rules, each power company combines a self actual system to make a proper recovery scheme (including a black start scheme), so that an effective guide criterion is provided for a large area after a power failure accident, the loss of the area is reduced, and power is supplied to an important load in time. The system constructed in the initial stage of black start is a weak power grid structure, and if any out-of-limit fluctuation occurs, the whole black start can be unsuccessful, and larger loss is caused. Careful verification procedures are important for a safe, efficient black start scheme. At the tail end of the power transmission line, if the voltage amplitude is too large, equipment can be broken down to cause misoperation, so that the recovery of the black start of the system is unsuccessful, and great economic loss is caused. Therefore, the black start path recovery must pay attention to the verification of the operation overvoltage at the tail end of the line and the power frequency overvoltage. In order to limit the power frequency overvoltage of a long line, a shunt reactor is generally adopted to compensate the capacitance current of the line in an ultra-high voltage system and an extra-high voltage system at present, so that the capacitance effect of the line is weakened. Meanwhile, various methods in the current stage are not suitable for energy supply systems mainly comprising small-capacity hydropower stations, and the overvoltage phenomenon can be effectively inhibited only by considering the load.

Disclosure of Invention

The invention provides a load quantity calculation method for suppressing overvoltage of a no-load long line, which is used for obtaining the load quantity and effectively suppressing the overvoltage of the no-load long line.

The technical scheme of the invention is as follows: a load calculation method for suppressing no-load long line overvoltage comprises the following steps:

s1, building a simulation model, and performing a high-voltage transmission line empty charge experiment; the model comprises the following main modules: the device comprises a three-phase constant voltage source, a three-phase transformer, a three-phase distribution parameter circuit, a three-phase voltage and current measuring module, a three-phase circuit breaker and an oscilloscope;

s2, calculating delta U of the air charging line:

ΔU＝(P₂′R+Q₂′X)/U₁

in the formula: delta U is a terminal voltage increase value caused by the capacitance effect of the power transmission line; p₂′＝0.5×G×U₂ ²，Q₂′＝-0.5×B×U₂ ²，U₁For line head end voltage, U₂The voltage at the tail end of the line, G is the conductance of the line, B is the susceptance of the line, R is the resistance of the line, and X is the reactance of the line;

step3, calculate P_L、Q_L：

In the formula: u shape_xFor a predetermined line end voltage, P_LFor active load to be solved, Q_LFor reactive loads to be solved, P_L＝aQ_LAnd a is a coefficient.

The high voltage refers to 220kV and 110kV voltage levels.

R ═ R₁l、X＝x₁l、G＝g₁l、B＝b₁l; wherein r is₁Resistance per unit length of line, x₁Reactance per unit length of line, g₁Conductance per unit length of line, b₁Is the susceptance per unit length of the line.

The invention has the beneficial effects that: the invention can enable a dispatcher to calculate the load according to the desired power frequency overvoltage of the power transmission line, and the tail end of the line is provided with a proper amount of load for switching on, so that the amplitude of the operation overvoltage and the power frequency overvoltage are in a reasonable range, the fluctuation is small, the burr phenomenon is reduced, and the invention has higher reference value for formulation and verification of a backbone network frame black start scheme, identification of voltage waveform and prediction of overvoltage in the black start process.

Drawings

FIG. 1 is a simulation diagram of the transmission line terminal voltage under no load condition;

FIG. 2 is a simulation diagram of line terminal voltage after switching on with load;

FIG. 3 is the effect of an on-load on the over-voltage after closing;

FIG. 4 is a comparison of 110kV operating overvoltage;

FIG. 5 is a comparison of 110kV power frequency overvoltage;

FIG. 6 is a comparison of 220kV operating overvoltage;

FIG. 7 is a comparison of 220kV power frequency overvoltage;

FIG. 8 is a flow chart of the present invention.

Detailed Description