JPH0440260Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a tap shift detection device for a transformer with an on-load tap changer that operates in parallel in plural units at the same time.

Generally, when a plurality of transformers with on-load tap changers are operated in parallel, it is necessary to simultaneously change the taps of each transformer in response to load fluctuations. When tap misalignment occurs, circulating current flows in the circuit between the transformers, resulting in large losses as reactive current.

As a conventional tap misalignment detection device, for example, a dial switch type device shown in FIG. 1 is often used. Dial switches 1A, 1B, and 1C are connected in parallel to a storage battery 2, which are connected to an electric operating mechanism of a switching device (not shown) attached to each transformer. Dial switch 1A is linked to the No. 1 transformer side, dial switch 1B is linked to the No. 2 transformer side, and dial switch 1C is linked to the No. 3 transformer side. The switching contacts of each dial switch 1A, 1B, 1C are wired so as to form a closed circuit with the storage battery 2 when the taps are at the same position. A relay 3 for detecting tap deviation of the first and second transformers is connected in series to the circuit passing through the storage battery 2 and the dial switches 1A and 1B.
A relay 4 for detecting tap deviation of transformers No. 1 and No. 3 is connected in series to the circuit passing through A and 1C.

In this detection device, each dial switch 1A,
When the tap instruction positions of 1B and 1C are the same, a closed circuit is formed and the tap deviation detection relay 3,
4 is in an energized state. When a tap misalignment occurs and the changeover contacts of the dial switches 1A and 1B shift, the circuit becomes open and power to the tap misalignment detection relay 3 is cut off, and the contact closes and an alarm is issued. The switching control circuit is locked.

However, with the above control device, when adding a new transformer, it is necessary to connect auxiliary relays as many as the number of tap points of the transformer to the dial switch used for other purposes, and to amplify the contacts, and the wiring circuit There was a problem that made things more complicated.

In addition, in the case of a transformer that is not equipped with a tap shift detection device, the electric operating mechanism of the switch is equipped with a circuit that detects the presence or absence of tap switching operation and issues an alarm if there is a discrepancy with the tap switching control signal. It is being

However, in the above device, if the control signal is issued and the tap switching operation is not performed,
Although it is possible to detect tap deviations for each transformer, it is possible to detect tap deviations for each transformer, but if a switching operation is performed with the taps of each transformer misaligned, or if some switchers are switched to a tap other than the one specified. In such a case, the tap misalignment could not be detected and the reliability was low.

The purpose of the present invention is to provide a tap shift detection device for a transformer with an on-load tap changer that eliminates the above drawbacks, simplifies the circuit, makes it easy to add more transformers, and has excellent reliability. That is.

An embodiment of the present invention will be described in detail below with reference to FIGS. 2 and 3.

Between the power source 5 and the load 6, three transformers 7A, 7B, and 7C with on-load tap changers are installed.
The units are connected in parallel. Each transformer 7A, 7B,
Current transformers 8A, 8B, and 8C are attached to the secondary side of 7C, respectively.

The secondary sides of the adjacent current transformers 8A and 8B are combined as a pair and cross-connected so that the direction of the induced current is opposite to form a closed circuit. In between, the tap shift detection relays 3 of the first and second transformers 7A and 7B are connected in parallel. Similarly, the secondary sides of current transformers 8B and 8C are combined as a pair and cross-connected so that the direction of the induced current is opposite to form a closed circuit, and both secondary side coils are In between, the tap shift detection relays 4 of the second and third transformers 7B and 7C are connected in parallel. Furthermore, the contacts 3a and 4a of both tap misalignment detection relays 3 and 4 are as follows:
It is connected in parallel or series to a lock circuit (not shown), and when a tap shift is detected, its contact 3
a, 4a are closed.

Next, the operation of the next detection circuit will be explained.

If a tap shift occurs in transformers 7A, 7B, 7C during parallel operation, transformers 7A, 7B, 7C
Circulating currents ` <sub>`1'</sub> ', `` <sub>2''</sub> , and `` ₃ '' flow between them due to the induced voltage difference between the transformers 7A, 7B, and 7C.As shown in Figure 3, the vector of this current is approximately The current is delayed by 90 degrees, and a current flowing in a transformer with a low induced voltage is 180 degrees different from that in a transformer with a high induced voltage. Therefore, by detecting this circulating current, it is possible to detect a tap shift.

Note that the vectors when the No. 1 transformer 7A causes a tap shift with respect to the No. 2 and No. 3 transformers 7B and 7C are as shown in FIG.

The symbols in the figure are as follows. _L : Current value supplied by each transformer to the load (assuming the load power factor is 1) ₁ , ₂ , ₃ : Secondary current of each transformer ₁ : Current value of the No. 1 transformer at tap shift Circulating current `` <sub>2</sub> ,'' <sub>3</sub> : Circulating current of the No. 2 and No. 3 transformers at the time of tap deviation θ <sub>1</sub> : Secondary current value of the No. 1 transformer at the time of tap deviation θ <sub>2</sub> , θ <sub>3</sub> : Tap deviation Phase angle of the secondary current of the No. 2 and No. 3 transformers at the time ′ <sub>1</sub> : Secondary current value of the current transformer on the No. 1 side ′ <sub>2</sub> ,′ <sub>3</sub> : Current transformation on the No. 2 and No. 3 sides Secondary current value of the transformer ′ <sub>1</sub> −′ <sub>2</sub> : Current supplied to the relay for detecting tap deviation Therefore, No. 1 transformer 7A and No. 2 transformer 7B
When a tap deviation occurs, circulating currents `` _1' ' and `` _2'' flow in the direction of the arrows as shown in Fig. 2, and the combined current of this and the load current _L causes the current transformers 8A, 8A,
Currents (secondary currents) ' ₁ and ' ₂ are induced on the secondary side of 8B, and when this current difference ' ₁ -' ₂ is detected by the tap deviation detection relay 3, its contact 3a closes and the lock is activated. The circuit is activated and the switching control circuit is locked.

Although the above example shows the case where three transformers are operated in parallel, the same applies to the case of four or more transformers, and even when adding a transformer, the current transformer of the adjacent transformer and All you need to do is add a relay to detect tap misalignment between the two.

In addition, the method of connecting the secondary side of the AC transformer one pair at a time to the tap shift detection relay is not limited to the case where the secondary sides of the AC transformer are adjacent to each other. Any combination structure may be used, such as a combination with a transformer. Further, the current transformer may be of a configuration in which an auxiliary current transformer for the configuration of the present invention is inserted into a current transformer circuit already provided for measurement, and an electric device for detecting tap deviation is added to the secondary side of the auxiliary current transformer.

As explained above, according to the present invention, by detecting the circulating current caused by tap misalignment during parallel operation, tap misalignment can be detected with a simple circuit configuration, and it is also easy to add a transformer. Therefore, it is possible to obtain a tap shift detection device for a transformer with an on-load tap changer, which is also highly reliable.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional dial switch type tap deviation detection device, Fig. 2 is a circuit diagram of a tap deviation detection device according to an embodiment of the present invention, and Fig. 3 is a circuit diagram of a tap deviation detection device according to an embodiment of the present invention.
The figure is a current vector diagram when three units are operated in parallel. 1A, 1B, 1C...Dial switch, 2...
...Storage battery, 3, 4...Tap displacement detection relay,
5...Power supply, 6...Load, 7A, 7B, 7C...
Transformer, 8A, 8B, 8C...Current transformer.

Claims (1)

[Scope of utility model registration request] A current transformer is installed on the secondary side of multiple transformers with on-load tap changers connected in parallel between the power source and the load, and the secondary sides of these current transformers are connected as a pair. A relay for detecting tap deviation is connected in parallel between both secondary coils to form a closed circuit, and a circulating current induced by the deviation of the taps of each transformer is transferred to the relay for detecting tap deviation. 1. A tap shift detection device for a transformer with an on-load tap changer, characterized in that the tap shift detection device detects the tap shift in a transformer with an on-load tap changer.