JPS6152430B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for testing a temperature rise in a transformer. There are three types of transformer temperature testing methods: (a) actual load method, (b) equivalent load method, and (c) return load method, but (a) actual load method cannot generally be performed in a factory. Therefore, (b)
The equivalent load method of (c) and the return load method of (c) have been implemented. The equivalent load method is mainly used to test oil-immersed transformers, and the returned load method is mainly used to test dry type transformers, but the test method is complicated. Also,
When conducting the above temperature test, the supplied current is limited by the standards to be 90% or more of the rated current.
For example, in the oil-immersed type, the supply loss is over 80% and the current is 90%.
% or more, and in a dry method, if the current is 90% or more, it is possible to convert the temperature to 100% loss and 100% current. Each of the above test methods can be applied to general transformers, but for example, primary to secondary or primary to secondary to tertiary transformers.
In the case of special transformers that have a secondary winding and the winding capacity differs greatly, the test method has the disadvantage of being complicated. A particularly special type of transformer is an oil-immersed transformer that has secondary and tertiary windings with a delta (Δ) connection on the primary side and a star (Y) connection on the secondary side, as shown in Figure 1. The temperature test is usually performed three times using the equivalent load method. However, in recent years, special transformers such as those described above have come to be manufactured as dry type transformers in order to make the location where the transformer is installed incombustible. In the case of dry type transformers, temperature tests are conducted using the above-mentioned return load method, so testing cannot be easily performed. For this reason, we would like to perform a test using the equivalent load method, but this becomes impossible if the capacity ratio between the primary and secondary sides of the transformer becomes large. For example, if the transformer shown in Figure 1 has the ratings shown in the table below, this transformer can be calculated using the equivalent load method.

[Table] To perform a temperature test, all terminals on the secondary side are short-circuited and 100% current is supplied to the primary side. The secondary current (I) flowing to the secondary side is I = 2230/3150 x 100. %=70.8%. Since this value is less than the above-mentioned 90% or more, the primary side overcurrent % required to flow 90% to the secondary side is I ₁ = 90 ÷ 70.8 = 127.1%, which can be tolerated by a normal transformer. It turns out that the overcurrent exceeds the limit. Therefore, as a condition for implementing this method, it is necessary to make the primary winding size excessively large so as to withstand overcurrent, and it is not possible to provide an economical product. This invention was made in view of the above circumstances, and aims to provide a temperature rise test method for transformers that can reliably and easily test the temperature of transformers with special wiring connections using the equivalent load method. . An embodiment of the present invention will be described below with reference to FIG. In FIG. 2, the primary winding 1 on the primary side remains connected in delta, and the secondary winding 2 and tertiary winding 3 on the secondary side are connected as follows. While the secondary winding 2 remains star-connected, the x, y, and z phase windings 3a to 3c of the tertiary winding 3 are separated, and one end of each winding is connected to the u, v, Connect to w phase. The secondary side capacitance when the secondary side is connected in this way is calculated as follows. Secondary voltage = 682 (V) × √3 × √3 = 2046V Also, secondary capacity = √3 × 2046 (V) × 770 (A) =
It will be 2729KVA. As shown above, if you connect the wires in Figure 1 as shown in Figure 2, the capacity of the secondary winding will be
It can be reduced from 3150KVA to 2729KVA. Next, in order to short-circuit the open other ends of the windings 3a, 3b, and 3c of the tertiary winding 3 and perform a temperature test using the equivalent load method, when 100% current is supplied to the primary side, the secondary current I
becomes as follows. I = 2230/2729 x 100% = 81.7% This value is less than 90%, but if the primary side supply current is 110%, the secondary current I will be I = 81.7% x 1.1 = 90%, equivalent Temperature testing of dry type transformers can be reliably performed using the load method. In addition, if there are two transformers with the same rating, the return load method is also possible. In addition, in FIG. 2, u, v,
The w phase may be separated and connected to the tertiary winding 3. The above is a test method for dry type transformers.
If an oil-immersed transformer is connected in the same manner as described above and the equivalent load method is tested, the temperature rise test can be performed in one test, making the test easier than the conventional method. As described above, the present invention has the advantage that even dry type transformers with special wiring connections can be reliably tested for temperature rise using the specified equivalent load method, and the testing method can be extremely simple. In particular, since there is a tendency for the number of transformers with special wiring to increase, the merits of the method of the present invention are extremely large.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram showing a transformer with special wiring, Figure 2
The figure is a wiring diagram of an embodiment according to the present invention. 1... Primary winding, 2... Secondary winding, 3... Tertiary winding, 3a to 3c... Each phase winding of tertiary winding.

Claims (1)

[Claims] 1 It has a primary winding connected in delta on the primary side,
A dry type transformer that has star-connected secondary and tertiary windings on the secondary side, and the secondary winding capacity is larger than the primary winding capacity, is tested using the equivalent load method. In this case, after separating the star connection of one of the windings on the secondary side, the windings are arranged in a staggered connection, and one end of each of the separated windings is connected to the winding of the other star connection. A temperature rise test method for a transformer in which each phase is connected and the other ends of the separated windings are connected together to short-circuit the secondary side and supply a predetermined current to the primary side.