JPH081859B2 - Tap switching device under load - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a load tap switching device, and particularly detects an insulating oil temperature in a switching switch chamber, and thereby calculates a temperature and a temperature rising rate. Monitor for any abnormalities,
Further, the present invention relates to a load tap switching device for predicting a situation where an abnormality has spread.

(Prior Art) A load tap switching device provided in a transformer of a power transmission and distribution system is provided in the transformer when the load of the power transmission and distribution system fluctuates and the voltage change due to this fluctuation exceeds a certain limit. The voltage of the power transmission and distribution system is kept constant by switching the taps that are open. Further, the load tap switching device provided in the industrial transformer switches the taps of the transformer according to the electric power required by the industrial equipment to supply the required electric power.

This load tap changer comprises a switch signal generator, a load tap changer and an electric operating mechanism. The load tap changer further comprises a changeover switch and a tap selector.

The outline of the switching operation in the device having this structure is as follows. That is, when the voltage change exceeds a certain limit, first, a signal is generated by the switching signal generating section, and thereby the electric operating mechanism is started to drive the load tap changer. As a result, the drive shaft of the tap changer under load rotates, and due to this driving force, the movable contact of the tap changer moves away from one fixed contact, and when it is turned on to another fixed contact, the corresponding action is taken. The switching switch performs the switching operation from one tap to the other tap. By the way, for example, especially in the power transmission and distribution system which is the main trunk line, if this load tap switching device fails, there is a possibility of widespread power failure.When this device fails, it is detected and recognized as soon as possible. Then you need to deal with this.

Conventionally, as the failure detection means of the tap changer during load,
When the insulating arc is decomposed by an abnormal arc generated inside the tap changer during load and a large amount of gas is generated, the oil flow and gas pressure are detected, and the magnitude of the current flowing through the tap changer during load is changed. There is a device that measures short circuit between taps by measuring with a measuring instrument.

(Problems to be Solved by the Invention) However, the conventional load tap changer as described above has the following drawbacks.

The switching switch of the tap changer under load is installed in an independent oil tank isolated from the transformer, and opens and closes the current in this oil tank. The contact group that opens and closes the current sometimes bridges the taps during operation, and a current limiting resistor is provided to reduce the current due to the bridge. The temperature of the current limiting resistor rises due to energization, but the switching switch is operated at high speed to suppress this temperature rise. Therefore, the higher the switching frequency, the higher the probability of mechanical damage due to high-speed switching.

For example, if some kind of damage causes the switching operation to stop halfway, by continuing to energize the current limiting resistor, the oil temperature in the oil tank rises, causing thermal damage to the switching switch and oil tank, and significantly It may lead to a major accident such as a transformer fire.

Further, even if the current limiting resistor itself is blown out due to an increase in temperature, an abnormal arc may be generated in the blowout portion to raise the oil temperature in the oil tank, resulting in the same accident as above.

The above example is an example where there is mechanical damage, but as another example, if the tap changer under load continues to be abnormally and continuously switched, the oil temperature in the switching switch will continue to rise and eventually the resistance will increase. It is conceivable that the result will be the same as the accident described above due to the meltdown.

In the conventional technology, such an accident occurs only when the oil flow velocity in the oil pipe of the tap changer under load, which is generated by the pressure of the gas generated when the insulating oil is decomposed by an abnormal arc or heating, reaches a certain speed. Had been detected. Therefore, since a secondary phenomenon that follows the accident phenomenon is captured, even if an accident is detected, the damage may have already spread and the tap changer and transformer under load may not be protected. Furthermore, it is not possible to judge with the conventional device whether the accident that occurred is kept in a small accident situation or the accident continues to expand.

Therefore, in order to protect the accident in the above example, the temperature condition inside the switching switch is directly detected and monitored, and the abnormality is detected in a short time. Become.

The present invention has been made in order to solve the problems of the prior art as described above, and its purpose is to detect the oil temperature in the switching switch oil tank of the tap changer during load, and also to detect the elapsed time and the detected temperature. Provides a tap switching device at load that can calculate the temperature rise rate and detect whether there is an abnormality in the switching switch, and can predict a serious accident when there is an abnormality. To do.

[Structure of Invention]

(Means for Solving Problems) In order to achieve the above object, the present invention installs a temperature detecting unit inside the switching switch oil tank of the tap switch during load, and externally connects the tap switch transformer during load. Is characterized in that an abnormality determination unit capable of determining an abnormality based on the dangerous temperature and the dangerous temperature increase rate is provided.

(Operation) With such a configuration, the abnormality of the switching switch can be detected in a short time from the oil temperature change inside the switching switch oil tank in the abnormality determination unit, and it takes time before the abnormality spreads and a serious accident occurs. By extrapolating the time in advance, a serious accident can be predicted.

(Embodiment) An embodiment of the tap switching device during load according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the embodiment. Reference numeral 1 is a load tap changer, which is composed of a changeover switch 2 and a tap selector 3. The switching switch 2 is composed of an oil tank 4 which is isolated from the transformer 20, a shutoff unit 5 which opens and closes the current stored in the oil tank 4, a current limiting resistor 6 which limits the shutoff current, and insulating oil 7. ing.

The temperature detection unit 8 is installed in the insulating oil 7 in the switching switch oil tank and is connected to the abnormality determination unit 9.

The abnormality judging section 9 judges whether the present temperature is above the critical temperature or not and calculates the temperature rise temperature with respect to time from the A / D conversion circuit 10 for converting an electric analog signal into a digital signal and the digital signal of the temperature. , It is judged whether this temperature rising speed is higher than the dangerous temperature rising speed, and when the current temperature is lower than the dangerous temperature and the temperature rising speed is higher than the dangerous speed, the time to reach the dangerous temperature is calculated and the current temperature is calculated. It is composed of a calculation judgment unit 11 for judging whether an abnormality immediately leads to a serious accident and an abnormality display unit 12 for displaying a judgment result of failure or accident. Furthermore, the calculation determination unit 11 is connected to the line breaker 13 that opens and closes the charging of the transformer unit 20.

The operation of the tap switching device under load configured as described above will be described with reference to FIG. 2 showing a change form of the oil temperature in the switching switch and FIG. 3 showing a determination flow chart of the calculation determination unit 11.

During normal switching, the oil temperature changes as shown by the chain double-dashed line in FIG. During abnormal times, the oil temperature will continue to rise as shown in the actual battle. _TCR is set as 100 ° C as an example of dangerous temperature. The temperature rise rate is indicated by dT / dt, which is the dangerous temperature rise rate (dT / dt) _CR . As an example (dT / dt) _CR is 3 ℃ / 1
Set as minutes.

These dangerous temperature and dangerous temperature rising speed are set by the boiling point of oil and the energizing ability of the switching device.

Next, the operation of the operation judging section 11 is as follows according to FIG.

The oil temperature T _n at the current time t _n is detected. T _n is the critical temperature TCR
If it exceeds, it is judged as a serious accident and the circuit breaker 13 is operated. Next, when T _n is below TCR, the temperature rise rate (dT / dt)
_n is calculated by the equation (1).

Here, T _n-1 and t _n-1 indicate the temperature and the detection time immediately before the current time. This is the dangerous temperature rise rate (dT / dt)
If it exceeds _CR , it is determined that the switching switch has a failure, and an alarm is generated on the abnormality display section 12. Furthermore, at this time, it is calculated and determined as follows whether the present failure immediately leads to a serious accident.

The time t _a from the current temperature T _n to the dangerous temperature T _CR device is calculated by the following equation (2).

The t _a is greater likelihood of immediate danger temperature oil temperature is shorter. If the danger prediction time t _EX is set and t _a is less than t _EX, it is determined that a serious accident is likely to occur and the line breaker is determined.
Operate 13.

According to the present embodiment, the temperature detector 8 is provided inside the oil tank of the switchgear, and the abnormality determiner 9 detects the oil temperature and the oil temperature rise, so that the determination of a serious accident or failure is short. Done in time. Furthermore, even in the case of a failure, it can be predicted before a serious accident is reached.

The present invention is not limited to the above embodiment, the distance between the temperature detection time shortened from, to increase the calculation accuracy by calculating the (dT / dt) _n and t _a by a polynomial by detection points or three points be able to.

〔The invention's effect〕

As described above, according to the present invention, the temperature of the oil in the oil tank of the switchgear can be detected and calculated to determine a serious accident or failure, and even in the case of a failure, it can be predicted before the serious accident is expanded. Therefore, it is possible to provide a load tap switching device with high operational reliability.

[Brief description of drawings]

FIG. 1 is a block diagram of a tap switching device under load according to the present invention,
FIG. 2 is an explanatory view of the oil temperature change in the oil tank of the switching switch, and FIG.
The figure is a flowchart of the abnormality determination method. 1 …… Tap switch during load, 2 …… Switching switch 3 …… Tap selector, 4 …… Oil tank 5 …… Cut off part, 6 …… Current limiting resistor 7 …… Insulating oil, 8 …… Temperature detection Part 9 ... Abnormality judgment unit, 10 ... A / D conversion circuit 11 ... Calculation judgment unit, 12 ... Abnormality display unit 13 ... Line breaker, 20 ... Transformer

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-58-154212 (JP, A) JP-A-60-180431 (JP, A) JP-A-60-178520 (JP, A) JP-A-60- 186007 (JP, A) Actual opening 55-147722 (JP, U) Actual opening 60-66016 (JP, U)

Claims (2)

[Claims] Claim: What is claimed is: 1. A temperature detecting section for detecting the temperature of insulating oil in an oil tank of a tap changer during load, and an output signal of the temperature detecting section is compared with a preset dangerous temperature of the oil temperature. A tap changeover under load, which is provided with an abnormality judging section for judging an abnormality by comparing a temperature increase rate calculated based on an output signal of the section with a preset dangerous temperature increase rate of the oil temperature. apparatus. 2. A temperature detector for detecting the temperature of insulating oil in the oil tank of the tap changer during load, and a detection temperature detected by the temperature detector exceeding a preset dangerous temperature of the oil temperature. If it is judged to be a serious accident, a cutoff command is issued. The alarm command is sent and the time until a serious accident is extrapolated and calculated.
When the time is shorter than a preset risk prediction time, an abnormality determination unit that determines that a serious accident is likely to occur and issues a cutoff command is provided.