The new large-scale power transformers in the power system adopt on-load voltage regulators and have a well-defined low-voltage power distribution network structure and sufficient reactive power compensation capacity to ensure safe operation of the power grid and meet the requirements of users for power quality. The main transformers in 110kV substations in some places and counties have used non-excitation surge transformers for historical reasons.
This method has several drawbacks; first, it requires a certain amount of power outage time to make adjustments, interferes with normal production, and provides less power; second, the number of adjustments is limited, and only periodic or seasonal adjustments can be made and cannot be performed frequently. The voltage fluctuation caused by the change of the daily peak-valley voltage is in a helpless state. Thirdly, the non-excited tap-changer is frequently operated, and the seal is easily damaged to cause oil leakage. The fourth is the fact that the agricultural distribution transformer tap-changer is self-adjusting. Frequently, it is easy to cause an event that the voltage of the low voltage user is too high or the electrical equipment is damaged after the main transformer changes the tap position. The only way is to transform the transformer to achieve on-load voltage regulation.
(1) Wearing boots reform method
The so-called wear boots is to open the neutral point of the high-voltage three-phase coil of the main transformer, and separately connect the compensator (namely, the SZZ7 type neutral load voltage regulating transformer) to the voltage regulator coil, and the low voltage side of the main transformer and the excitation of the compensation transformer. The coils are connected in parallel to achieve on-load voltage regulation. The voltage regulation is based on the voltage superposition principle. The voltage regulator compensates the voltage of the main transformer high-voltage side coil within the rated voltage range by means of the on-load voltage regulator switch.
In this voltage regulation mode, the compensator only withstands the voltage of the neutral point or N-level voltage regulation ΣΔU1 during operation, and the insulation level requirement is low. When the transformer neutral point is operated in the high-current grounding mode, the insulation level is only It is enough for 35kV (we design and manufacture according to 40kV), can also design higher insulating level according to the operating mode. In this method, as long as a neutral point voltage regulating transformer is separately manufactured, the cost of reconstruction is low, and the on-site reconstruction of the main transformer neutral point can be completed within one working day. If the main transformer overhaul is performed at the same time, the overhaul period is basically not increased. .
The boots mode is suitable for a range where the voltage fluctuation range has exceeded the non-excitation voltage regulation range, that is, the non-excitation voltage regulator switch position cannot reach the voltage qualified requirement even in the highest gear or the lowest gear. The neutral point on-load tap-changer used by us can realize wide-range voltage regulation of ±12% U1N. If it is matched with the main transformer without excitation switch, it can more easily move the pressure-adjusting range up and down (excitation-free voltage regulation range). In order to meet the actual pressure regulation needs, and increase the output of the main transformer.
At the same time, according to the actual situation to determine the voltage adjustment range to configure the neutral point load transformer, the capacity configuration shown in Table 1, the various voltage transformers are suitable for transformation. We completed the transformation of the four main transformers. The items listed in Table 1 have been transformed. However, this method needs to increase the floor area of ​​a transformer, and the wiring is a bit more complicated. However, from the perspective of the entire reconstruction period and saving investment, it is a relatively economic and reasonable reconstruction program.
(2) Knapsack reform method
The so-called backpack is a more economical and applicable method of transformation under the condition that the transformer non-excitation voltage regulation range can meet the needs of the supply voltage fluctuation in the region. That is, the tap-off lead on the original off-circuit tap-changer is removed, the switch is removed, a jumper-type or linear on-load tap-changer is added, and the original tap lead is led to the on-load tap-changer. The modification method of load regulation and pressure also requires only one overhaul cycle, and the main body modification (lifting cover or hanging core) takes only one day. Simultaneously with the core inspection, the bell jar (tank case) or fuel tank is also transformed. The key to its transformation is to ensure that the core body is not subjected to tides to complete the renovation work within one day, otherwise it will extend the power outage time and increase the cost of renovation. At the same time, since the original transformer cannot leave the lead channel during the transformation, corresponding measures must be taken to ensure that the insulation distances of all types of transformers are in line with the requirements, and that it is convenient for future maintenance work (ie, the hanging hood and the core are not change). In this regard, we have done a lot of work, equipped with appropriate equipment, conducted research on each link of the transformation, and worked out a set of feasible construction plans. Using this method, we have transformed five times and have achieved the intended purpose. It is indeed an economical and simple transformation method.
(3) Concluding remarks
The above are two of the methods we have adopted for transforming the main transformer over the years. We have also carried out more than 10 transformations including aluminum-aligned copper, thin insulation insulation, and body-fitted pressure-adjusting coils, but the cost is high. The cycle is also longer. For agricultural power transformers, the above two transformation methods have their own uniqueness and are also suitable for industrial and mining enterprises.
The TPFKC-A transformer on-load tap changer tester elaborated by Yangzhou Tuopu Electric Technology Co., Ltd. is used to measure the parameters of various on-load tap-changers of transformers. The instrument is controlled by a computer and can be realized by a specially designed measuring circuit. The on-load tap-changer's transition time, transition waveform, transition resistance, three identical phases, and other parameters can be measured. The user can directly measure the tapping lead by the root requirement and on-site conditions. It can also be used by the transformer three-phase bushing and Neutral point direct wiring measurement.
The on-load tap-changer tester of TPFKC-A transformer has the functions of analyzing, storing and printing the measured data. Solved the current power transformer on-load tap changer measurement method is backward, there is no special test method, can be in the power equipment preventive testing and transformer overhaul in a timely manner to diagnose the potential failure of the on-load tap changer, to improve the power system operation Reliability is important.
Transformer On-load Tap-Changer Tester Product Features
1, strong comprehensive measurement capabilities. The measurement of various numbers of on-load tap-changers is possible in one instrument. Such as the switch selection, whether there is a break point in the whole process of switching, transition waveform, transition time, transition resistance, three identical period and so on.
2. More comprehensive analysis of measurement results. The user can analyze the resistance value of each point and each segment of the waveform and the time of each segment through the large-screen LCD display, the time of each time segment and the different phases of the three phases. Through the screen analysis, you can learn to switch During the process, each time the three-phase switch of various parameters changes, but also the waveform printing, storage and access to historical waveform analysis and comparison.
3, print output. The instrument is equipped with a panel-type front paper change printer that can be directly archived as a switch test report.
4, menu-driven, flexible operation. All operating functions, hints, and measurement results are displayed on a 240 x 128-dot large-screen LCD. As long as the user presses the function key according to the prompt, the measurement can be performed.
5, the instrument has anti-shock, overvoltage protection circuit. All external leads of the instrument are sent to the measurement circuit through the protection system, which can prevent damage to the instrument due to momentary discharge of large inductance or wiring errors.
6, has a good anti-jamming performance. All-aluminum chassis and instrument are equipped with power noise filter and anti-interference circuit, which can be used for reliable measurement at sites with poor power quality and strong electromagnetic field interference.
7, power data retention. The data and waveforms measured by the user can be stored in the instrument, and the stored contents will not be lost due to power failure. It is especially suitable for the field laboratory to return to the laboratory for analysis and archiving.
Transformer on-load tap changer tester technical parameters
1, the transition time measurement: the accuracy is 0.1ms;
2. Measurement of transition resistance: accuracy is 0.1Ω;
3, three simultaneous period: the precision is 0.1ms;
4, shows three-phase waveform: the accuracy is 0.1ms;
5, print the waveform range: 60ms / 120ms;
6, the transition resistance measurement range: ≤ 20 Ω;
7, the transition time measurement range: ≤ 400 ms;
8, the working environment temperature: -10 °C ~ 50 °C;
9, the power supply voltage: AC220V ± 10% 50Hz ± 10%;
10, external dimensions: 500 × 220 × 310mm
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Yangzhou Tuopu Electric Technology Co., Ltd. Address: No. 2, Guotai Road, Baoying County, Jiangsu Province, China Telephone Fax
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