CN203135276U - Device for heating transformer oil in transformer - Google Patents

Abstract

The utility model provides a device for heating transformer oil from the inside of a transformer. By using the device, one side winding of the transformer to be heated is short-circuited, and a voltage is applied to the other side winding, and the compensation capacitor group is used to compensate the inductive reactive power required for heating the transformer. The active current provided by the power supply heats the transformer oil. The utility model heats from the inside of the transformer, has uniform heating and good heating effect, and can effectively improve the heating efficiency of the transformer under low temperature conditions.

Description

A device for heating transformer oil from inside the transformer

technical field

The utility model belongs to the technical field of transformers, in particular to a device for heating transformer oil from inside the transformer.

Background technique

With the rapid development of my country's national economy, the demand for electricity and energy is increasing. Most of the coal resources are distributed in the northwestern region of our country. It is the most economical and effective way to convert coal resources into electricity and send them to coastal economically developed areas. During the "Twelfth Five-Year Plan" period in my country, we will vigorously develop UHV power grids. We will build multiple 750-1000kV AC and ±800kV DC transmission lines, and the investment in UHV transformer equipment will also increase at an alarming rate.

Northwest my country is a severe cold zone, and the installation, handover test, grid connection and on-site maintenance of UHV electrical equipment will inevitably encounter extremely cold weather. Ultra-UHV AC/DC transformers require that the body of the UHV AC/DC transformer be heated during installation to carry out hot oil circulation of the oil filter machine, especially during the transfer partial discharge test and grid connection, the temperature of the transformer body is required to be above 10°C, which proposes to avoid Low-temperature insulation test and low-temperature grid connection of ultra-UHV transformers.

Ancient heating methods such as eddy current method, hot air method, electric heating plate method and hot oil circulation of oil filter machine. These heating methods have their common disadvantages: low thermal efficiency, long heating time, poor economy, difficult implementation, and are not suitable for ultra-high voltage transformers with high voltage levels and large capacity. In the case of very low temperature, the use of oil filter for hot oil circulation can only heat the transformer oil to a lower temperature, especially the insulation test and the static period before grid connection cannot be used; in addition, the substation cannot Provide larger power supply to heat transformer, can only provide limited power supply.

Utility model content

In order to quickly raise the transformer oil from a relatively low temperature to the temperature required by the test and grid connection in a relatively short period of time, the utility model provides a device for heating the transformer oil from the inside of the transformer.

The utility model adopts the following technical solutions: a device for heating transformer oil from the inside of the transformer, including a power supply, a voltage regulator and a compensating capacitor bank, and an excitation transformer, the voltage regulator is an inductive voltage regulator, and the The compensation capacitor bank is a container mobile capacitor bank, the output end of the power supply is connected to the inductive voltage regulator, and the excitation transformer is connected to the inductive voltage regulator. the

Short-circuit the winding on one side of the transformer, connect the winding on the other side to the power supply for pressurization, connect the capacitor bank for reactive power compensation, and connect the output end of the power supply to an induction voltage regulator. It is required to adjust the voltage regulator, the excitation transformer raises the applied voltage of the transformer to the required voltage value, and the compensation capacitor bank compensates the inductive reactive power required for heating the transformer. the

。所述的动力电源无需提供无功功率，只提供变压器所需要的有功功率。安装在高压或中压侧的分接开关调在合适分接位置,原边电流达到额定值时,电力变压器的损耗相当于额定负载时的损耗。而施加经过计算的电压值，这时输入功率基本上都消耗在变压器等值电阻上，利用变压器的部分负载损耗产生的热量来加热变压器器身等。 The basic principle of this heating method is: the winding on one side to be heated is short-circuited, and the calculated voltage is applied to the other side. The short-circuit side and the pressure side should be flexibly selected after calculation according to the transformer parameters and heating equipment parameters. At this time, viewed from the pressurized side, the transformer is equivalent to an inductance connected in parallel with a resistor, and the large-capacity inductive reactive power and small-capacity active power of the transformer are supplied by an external power supply. In addition, the inductive reactive power required by the transformer is compensated by the compensation capacitor bank. At this time, the equivalent inductance of the transformer and the compensation capacitor are close to the parallel resonance state, and the near complete compensation is realized. In a circuit in which an inductor and a capacitor are connected in parallel, when the size of the capacitor just resonates with the inductor, ωL=1/ωC (where ω is the angular velocity, L is the inductance, and C is the capacitance), that is, all the power supply power is consumed by the resistor, so When the resonant frequency f ₀ =

. The power source does not need to provide reactive power, but only provides active power required by the transformer. The tap-changer installed on the high-voltage or medium-voltage side is adjusted to the appropriate tap position. When the primary current reaches the rated value, the loss of the power transformer is equivalent to the loss at the rated load. When the calculated voltage value is applied, the input power is basically consumed on the equivalent resistance of the transformer, and the heat generated by the partial load loss of the transformer is used to heat the transformer body.

In the heating process described in the utility model, the operation is carried out according to the following sequence: first, check whether the capacitance of the capacitor bank meets the requirements of the calculated value before wiring; ) short-circuit connection; again, perform wiring to complete the connection of the power supply, voltage regulator, excitation transformer and compensation capacitor bank; again, adjust the ratio of the transformer to determine whether the short-circuit loss meets the calculation requirements; Whether the actual output current of the transformer is within the range of the rated current; finally, the output voltage of the excitation transformer is increased to the design pressure value, and the heating process of the transformer oil is started.

In order to better realize the temperature increase of the transformer, thermal insulation equipment is added outside the transformer. The heat preservation equipment adopts rainproof and flame retardant heat preservation quilt.

Utilizing the utility model, the capacitive current and the inductive current provided by the compensating capacitor bank compensate each other, and the active current provided by the power supply raises the temperature of the transformer oil.

The utility model has the following effects:

1. The utility model generates heat from the inside of the transformer coil and structural parts, including coil resistance, wire eddy current and structural parts, which are collectively referred to as equivalent resistance loss heat generation. Therefore, as long as the transformer has appropriate heat preservation measures, the heating effect of this method is very good. High, and the temperature rises evenly, without local overheating;

2. The utility model adopts the structure of the container mobile compensation capacitor group, which is convenient to move, and the workload of the whole system in place and wiring is much less than that of other heating methods, which greatly reduces the workload;

3. The utility model raises the temperature in a static state, and can meet the requirements of the ultra-ultra-high voltage transformer transfer partial discharge test and the requirement that there must be enough time for static discharge before grid connection. Therefore, this method is irreplaceable by other transformer oil heating methods;

4. This method has good generality. Through calculation, all ordinary grade power transformers, ultra-high voltage and ultra-high voltage AC transformers and converter transformers can use this method to raise the temperature of transformer oil, so as to solve the problems of low-temperature installation, testing, grid connection and maintenance of ultra-high voltage transformers. It is only necessary to adjust the parameters of the relevant heating equipment according to the calculation results.

Description of drawings

Fig. 1 schematic diagram of wiring of the utility model;

Fig. 2 is a diagram of the test situation of the utility model;

In the figure: 1. Power supply, 2. Voltage regulator, 3. Excitation transformer, 4. Compensation capacitor bank, 5. Transformer, IR, active current, IL, inductive current, IC, capacitive current.

Detailed ways

For a 750kV UHV transformer with a capacity of 500MVA, its load loss is 184.6kW. The short-circuit voltage is 9.41kV, the design pressure is 7kV (after calculation, the applied voltage should not exceed 80% of the short-circuit voltage, and the heating power needs to be met at the same time), and the medium-voltage rated current is 1189A.

Get design current=1189×(7/9.41)=884A;

Transformer heating available loss=184.6×(7/9.41) ² =102kW;

Required inductive reactive power=7×884=6188kVA

In the wiring diagram of the utility model shown in Figure 1, the power supply 1 greater than 100kW is selected for heating, and the reactive power compensation capacitor bank 4 selected is a container mobile capacitor bank, which can meet the mobility requirements of the equipment; The selected power supply is the low-voltage power supply supplied by the substation; the selected voltage regulator 2 is an induction voltage regulator; the selected excitation transformer 3 is a distribution transformer. It has been verified by experiments that the reactive compensation power provided by the mobile compensation capacitor bank can meet the heating requirements of this method.

When heating, the capacitor compensation is 7900kVar, the input voltage of transformer 5 is 7.05kV, and the capacitor compensation current is 835A. The specific heating effect can be seen from Figure 2. Under the condition of outdoor temperature -20°C, within 20 hours, the temperature of the top layer oil increases from 2.5 °C has been raised to 29.1°C, meeting the handover test conditions and grid connection requirements, thus ensuring the safe operation of the transformer.

Claims (3)

1. A device for heating transformer oil from the inside of a transformer, comprising a power supply, a voltage regulator and a compensating capacitor bank, characterized in that: it also includes an excitation transformer, the voltage regulator is an inductive voltage regulator, and the compensating capacitor The group is a container mobile capacitor group, the output end of the power supply is connected to the induction voltage regulator, and the excitation transformer is connected to the induction voltage regulator. 2. The equipment for heating the transformer oil from the inside of the transformer according to claim 1, characterized in that: an insulation device is added outside the transformer. 3. The equipment for heating transformer oil from inside the transformer according to claim 2, characterized in that: the heat preservation equipment is a rainproof flame retardant heat preservation quilt.

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