JPS605731A - Internal shortcircuit protecting device of transformer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection device in the event of an internal short circuit in a tap-changeable transformer.

The internal short-circuit protection device of the transformer is provided on the primary side of the tap-changeable transformer 5 connected between the power supply line 1 and the load line 2 via a circuit breaker 3.4, as shown in FIG. and a current transformer 6.7 connected to the secondary side and the current transformer 6.
．． 7 is input, and when the inside of the transformer 5 is short-circuited, the current flowing through the primary and secondary sides causes the circuit breaker 3 to
A ratio differential relay 8 that opens the transformer 5 to prevent burnout of the transformer 5.
Generally, it consists of:

However, when the voltage tap of the transformer 5 is switched, the operating point of the ratio differential relay 8 changes in the above configuration, so in order to prevent this, the ratio differential relay 8 must be equipped with a current tap switching mechanism, or Current transformer 6 (if the voltage tap is on the primary side) or 7 (if the voltage tap is on the secondary side) had to be replaced depending on the voltage tap change.

The present invention has been made in view of the above points, and the currents flowing through the primary and secondary sides of a tap-switchable transformer are respectively input to a ratio differential relay via a current transformer. In the internal short-circuit protection device for a transformer, which cuts off power supply to the transformer by operating a ratio differential relay due to an internal short-circuit in the transformer, the current transformer is disposed on the tap switching side of the transformer. By providing a current transformation ratio switching means, it is possible to eliminate the need for a ratio differential relay with a special configuration.
Furthermore, it is an object of the present invention to provide an internal short-circuit protection device for a transformer that eliminates the above-mentioned disadvantages without having to take the trouble to replace the current transformer.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3 while referring to FIG. F.

A, B, and C are voltage taps formed by extending Hiji wires from multiple locations in the middle of the primary winding 11 for one phase of the transformer 5;
12 is a selection switch for selecting voltage taps A to C of the transformer 5; 13 is a secondary winding of the current transformer 6; 142 to 14C are multiple points in the middle of the secondary winding 13, that is, the selection switch of the transformer 5; Current taps A', B', and C are formed by extending the Hiji wires from the same number of points as the number of taps, and A', B', and C are voltage taps A, B, and C of the transformer 5.
, are limit switches that are closed in conjunction with selection by the selection switch 12, and A' corresponds to voltage tap A, B' corresponds to voltage tap B, and C' corresponds to voltage tap C, respectively.

Note that the current taps 14a to 14C and limit switches A', B', and C' link the current transformation ratio of the current transformer 6 disposed on the voltage tap switching side of the transformer 5 to the voltage tap switching of the transformer 5. It functions as a current conversion ratio switching means.

Next, the effect will be explained.

When voltage taps A, B, and C provided on the primary side of the transformer 5 are switched appropriately, for example, when voltage tap A is selected, limit switch A' is closed in conjunction with this switching operation, and the current transformer 6 is switched. The secondary side is switched to the current tap 14c. Therefore,
By switching to the primary side voltage tab A of the transformer 5, even if the turns ratio of the transformer 5 changes and the currents on the primary and secondary sides of the transformer 5 change, the voltage of the transformer disposed on the negative side changes. Since the current tap position on the secondary side of the current transformer 6 is set so that the selected current transformation ratio of the current transformer 6 is approximately the reciprocal of the turned ratio, the ratio of the ratio differential relay 8 is set. The operating point can be made almost the same as before the voltage tap switching. As a result, even if the primary side voltage tab of the transformer 5 is switched to any position,
If there is a short circuit inside the transformer 5, the circuit breaker 3 can be reliably opened by the ratio differential relay 8 without replacing the current transformer or using a special ratio differential relay equipped with a current tap switching mechanism as in the past. Therefore, burnout accidents of the transformer 5 can be prevented.

In the above embodiment, the current transformation ratio of the current transformer 6 is automatically switched in conjunction with the switching of the voltage tap of the transformer 5 using the limit switches A', to C'. Alternatively, it may be configured to switch manually.

As explained above, according to the present invention, the currents flowing through the primary and secondary sides of a tap-switchable transformer are respectively input to a ratio differential relay via a current transformer, In the transformer internal short circuit protection device, the power supply to the transformer is cut off by the operation of the ratio differential relay due to an internal short circuit of the transformer, the current transformer disposed on the tap switching side of the transformer, Since the current transformation ratio switching means is provided, the operating point of the ratio differential relay can be kept substantially constant regardless of voltage tap switching of the transformer. Therefore, even if the current tap of the transformer is changed, if a short circuit occurs inside the transformer, it can be reliably fixed without replacing the current transformer or using a special ratio differential relay equipped with a current tap switching mechanism as in the past. The power supply to the transformer can be cut off immediately, preventing transformer burnout accidents.

[Brief explanation of drawings]

Figure 1 is a schematic overall diagram of the internal short-circuit protection device of a transformer, Figure 2
The figure is a diagram of the primary winding configuration of the transformer, and FIG. 3 is a diagram of the secondary winding configuration of a current transformer according to an embodiment of the present invention. 3.4... Breaker 5... Transformer 6,7... Ratio differential relay ]1... Primary winding of transformer 12.
... Selection switch 13 ... Secondary winding of current transformer 14
a, 14 b, 14 c - current tap A,
B, C... Voltage taps A', B', C'... Limit switch agent Masuo Oone (and 2 others)

Claims (2)

[Claims] (1) The currents flowing through the primary and secondary sides of a transformer capable of switching the taps are respectively input to a ratio differential relay via a current transformer, and the ratio differential relay is activated by an internal short circuit in the transformer. In the internal short-circuit protection device for a transformer, which cuts off the power supply to the transformer by the operation of An internal short-circuit protection device for a transformer, characterized by: (2) The internal short-circuit protection device for a transformer according to claim 1, wherein the current transformation ratio switching means is switched in conjunction with the tap switching of the transformer.