Analysis on correction of intermittent operation impulse discharge voltage during high altitude live working

作者： GOZ Electric 时间：2024-10-17 09:46:46 阅读：17

In the new era, during the operation and maintenance of transmission lines, live work is a relatively common method. It can not only effectively reduce the frequency of power outages, but also effectively improve the reliability and stability of power supply. Judging from the situation in low-altitude areas, live work on transmission lines is already relatively common. In recent years, the construction level of my country's power transmission and transformation work has gradually improved, and the construction area has become wider and wider. Many transmission lines under construction have to pass through high-altitude areas. Affected by factors such as climate and environment, as the altitude increases, the corresponding air density will gradually decrease. This is why people are prone to hypoxia at high altitudes. At the same distance, the air gap discharge voltage is significantly lower than that in low-altitude areas, which imposes higher requirements on work safety and the safe distance for live work will increase. Therefore, in order to improve the stability and safety of the operation, it is necessary to study the appropriate discharge voltage correction method and determine the shortest safety distance. This paper takes a 750kV double-circuit linear tower on the same tower as an example, conducts tests in areas with altitudes of 2000m, 3000m, and 4300m, proposes a discharge voltage altitude correction method based on improved m parameters, and determines the minimum safety distance reference value for live work.

Keywords: high altitude areas; live work; voltage correction; impulse discharge

Judging from the current research status of domestic live work, relevant research institutions have carried out many experiments to study the discharge characteristics of typical air gaps such as rod-plate and rod-rod in high-altitude areas and the air gaps of AC and DC transmission lines. Altitude correction of discharge voltage provides rich reference data [1]. From a comprehensive perspective, common discharge voltage altitude correction methods include the g parameter method recommended in IEC60060-1-2010 and GB/T16927.1-2011, the meteorological condition correction method recommended in DL/T620-1997, and IEC60071-2- The m-parameter method recommended in 1996 and GB311.1-2012. Among them, the g-parameter method and the method in DL/T620 both use relative air density, absolute humidity and other atmospheric parameters in actual operations, so they are not very convenient to operate. The M parameter rule only requires the altitude and m value to be substituted, making the test simple and convenient.

1. Experimental analysis of discharge characteristics

(1) At different altitudes

Through this test, the results of the discharge characteristics of the live working gap were obtained. The results showed that as the altitude increases, the discharge voltage of the corresponding live working gap decreases to varying degrees when the workers are in different positions. At the same time, with the help of the slopes of different gap discharge characteristic curves, the discharge voltage gradient at different altitudes can be further analyzed.

As shown in Figure 1, workers obtained discharge voltage gradients at different altitudes and gaps under different working conditions. At an altitude of 23m, the minimum discharge voltage of the live working gap is 188.00kV/m.

The maximum value is 239.64kV/m; at an altitude of 2000m, the minimum value of the discharge voltage is 185.85kV/m, and the maximum value is 230.82kV/m; at an altitude of 3000m, the minimum value of the discharge voltage is 168.11kV/m, and the maximum value It is 225.29kV/m; at an altitude of 4300m, the minimum value of the discharge voltage is 165.36kV/m and the maximum value is 223.56kV/m. Taken together

See, the discharge voltage gradient of the split conductor-ground potential person is the highest, while the discharge voltage gradient of the equipotential person-upper cross arm gap is the lowest. When the altitude continues to rise, the corresponding discharge voltage gradients of different gaps will decrease.

Figure 1

(2) Operators in different postures

During the operation, due to the different postures of the operators, the discharge characteristics of different gaps are also different, which will be affected to a certain extent. The reason is that the discharge characteristics of different gaps will change regularly at different altitudes. In the following discussion, in order to avoid repetition, taking 4300m as an example, we learned that at the same altitude, the gap (gap 4) formed between the split wire and the ground potential personnel has the highest discharge voltage, while the equipotential personnel and their heads have the highest discharge voltage. The discharge voltage in the upper cross arm gap (Gap 2) is the lowest. Comparing gaps 1, 2, and 3, the ground electrode structures are all the same. The main reason for the difference in discharge voltage is the different positions of the workers. In gap 2, the operator stands on the split wire, forming an obvious rod-cross-arm structure. The result is that the discharge voltage has the lowest value. In gaps 1 and 3, the curvature radius of the operator's back is larger, and the discharge sites occur on the back and feet of the human body respectively. The electric field distribution is more uniform on the back than on the feet, so the final discharge voltage is higher than on the feet.