JP3058977B2 - Partial discharge detection method for electrical equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting partial discharge of electric equipment such as a transformer.

[0002]

2. Description of the Related Art For example, in a gas-insulated transformer in which SF ₆ gas as an inert gas is sealed, a partial discharge may occur in an internal winding. If the partial discharge occurs beyond a certain limit, the winding must be repaired or replaced. For this reason, in gas-insulated transformers, the occurrence of partial discharge is always or periodically detected and monitored.

One of the methods for detecting the occurrence of partial discharge is a method for detecting a decomposition gas. That is, SF ₆ gas is originally a stable inert gas, but it is known that the following chemical reaction is caused by generation of partial discharge and contact with moisture. SF ₆ → SF ₄ + F _{2 SF 4} + H ₂ O → SOF ₂ + 2FH SOF ₂ + H ₂ O → SO ₂ + 2HF

[0004] Since the several hundred ppm of water is present in the tank of the transformer is usual, when partial discharge occurs, stable SF6 gas is decomposed to active degradation gases such as SOF ₂ Change. Therefore, attempts have been made to detect the occurrence of partial discharge by detecting the decomposed gas with a decomposed gas sensor.

[0005]

However, gas-insulated transformers generally contain an adsorbent for adsorbing the decomposed gas in order to prevent the decomposed gas from affecting the transformer body. Even if a partial discharge occurs and a decomposition gas is generated, there is a possibility that the gas is adsorbed by the adsorbent and cannot be detected. Therefore, the timing of detection is important for detecting the decomposed gas, and there is a problem that the detection cannot be performed properly unless the decomposed gas sensor operates immediately after the partial discharge.

In this case, if the operation interval of the decomposed gas sensor is shortened, for example, to one minute, there is a possibility that the decomposed gas can be detected luckily. However, in order to operate the decomposition gas sensor, it is necessary to sample the gas manually or automatically from the gas insulated transformer, and in this case, mechanical parts having movable parts such as solenoid valves are absolutely necessary. There is a disadvantage that the life of the apparatus is determined by the existence of the movable part, and the decomposition gas sensor cannot be operated many times.

When a partial discharge occurs, an abnormal phenomenon such as an electromagnetic wave, light, sound wave, or pulse current occurs in addition to the generation of the special decomposition gas as described above. This makes it possible to detect the occurrence of partial discharge. However, it is difficult to distinguish electromagnetic waves generated during partial discharge from other broadcast waves or external noise. The same applies to the case of detecting other light, sound waves, pulse currents, and the like. It is also considered to provide a plurality of these detecting means. However, since the individual means cannot accurately detect the partial discharge, accuracy cannot be expected very much.

The present invention has been made in consideration of the above problems, and has been made in consideration of the above-described problems, and is intended to accurately detect the occurrence of partial discharge without shortening the life of the apparatus, and to improve the sensitivity of a decomposition gas sensor. An object of the present invention is to provide a discharge detection method.

[0009]

According to the present invention, there is provided a method for detecting a partial discharge of an electric device, comprising: a partial discharge sensor for detecting a partial discharge generated in the electric device; And a method for detecting the partial discharge of an electric device in which the decomposition gas sensor is operated by the detection signal of the partial discharge sensor, wherein the decomposition gas sensor is periodically operated independently of the operation based on the detection signal of the partial discharge sensor. The feature is to review the threshold. In this case, the threshold value can be reviewed by periodically measuring the dark noise of the decomposition gas sensor.

[0010]

The decomposed gas sensor only needs to be operated when it is assumed that partial discharge has occurred, and it is not necessary to simply operate it periodically, for example, at one-minute intervals. Therefore, if the decomposition gas sensor is operated based on the detection signal of the partial discharge sensor, the number of operations can be reduced, and the detection operation of the decomposition gas can be performed with good timing immediately after the occurrence of the partial discharge. Can accurately detect the decomposition gas. Further, the sensitivity of the cracked gas sensor is improved by periodically operating the cracked gas sensor and reviewing the threshold value of the cracked gas sensor.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings, taking a gas-insulated transformer as an example. In FIG. 1, a transformer 11 including an iron core 12 and a winding 13 wound around the iron core 12 is housed in a tank 11, and SF ₆ which is an inert gas is contained in the tank 11. (Sulfur hexaboride) gas is sealed. A sensor storage chamber 15 is provided on a side surface of the tank 11 through a glass window or the like so as to face the inside, and a corona sensor 16 as a partial discharge sensor is provided therein. Corona sensor 1
Reference numeral 6 denotes a ferrite antenna having substantially the same configuration as that of the ferrite antenna, which is formed by winding a winding 16 around a ferrite core 16a for several turns. A radiator 14 is provided on a side surface of the tank 11, and a decomposition gas sensor 18 communicating with a valve 17 is provided. The decomposition gas sensor 18 has a metal oxide semiconductor gas sensor such as SnO ₂ . This semiconductor gas sensor uses a platinum wire coil as S
It is constructed by burying it in an nO ₂ sintered body. By energizing and heating the coil, oxygen is adsorbed and electrons are enriched to increase the element resistance, where an active gas such as SO ₂ is added. When the element approaches, a phenomenon occurs in which electrons are released (stolen) and electrons are released to lower the resistance, so that this resistance change is read.

The operation of the decomposition gas sensor 18 is performed as follows. The sample gas is conveyed from the tank 11 to the decomposition gas sensor 18 via the filter 19 and the valves 17 and 20 including an electromagnetic valve by utilizing the pressure difference. The decomposition gas sensor 18 includes a container 21 that is filled with air before the sample gas is blown, and a semiconductor gas sensor 22 disposed in the container 21. The compressor 23 has a function of compressing air and enclosing it in the container 21. Oxygen may be used instead of air. The air or oxygen is necessary for keeping the SnO ₂ semiconductor gas sensor 22 in an electron-rich state and maintaining a high element resistance as described above. The sample gas after the measurement passes through the valve 24 and the lime water 25 through the pipe 26
Transported to the outside via

A sequence controller 27 is provided to control the plurality of valves 17, 20, and 24. This sequence controller 27 is a corona sensor 1
6 operates as a trigger.

That is, in the corona sensor 16, the sipling interval is set to, for example, about 30 minutes, and
While the operation of monitoring the occurrence of partial discharge is performed every 0 minutes, the operation of the decomposition gas sensor 18 is normally stopped.

When a partial discharge occurs in or near the winding 13 in the tank 11, an electromagnetic wave is generated at that time, and the corona sensor 16 is activated. 29. Even without the occurrence of partial discharge, the corona sensor 16 may receive an external broadcast wave or electromagnetic wave noise, which may be transmitted to the signal processor 29 via the amplifier 28.
The signal processing device 29 is provided with a circuit for holding the signal for 32 minutes. If the corona sensor 16 receives an electromagnetic wave during one sampling, the signal is held and the trigger is generated. Then, an operation command is transmitted to the sequence controller 27 of the decomposition gas sensor 18.

In this case, the output signal of the corona sensor 16 can be set as follows. For example, the output signal is DC 4-20 mA or DC 0-1 in the signal processing device 29.
It is converted to a form such as 0 mV and output. DC4-20
In mA, for example, 12 mA is responsible for the discharge charge amount of 1000 pc, and when this level (threshold) is exceeded, a TTL level pulse signal is applied to the sequence controller 27 as a trigger signal.

In response to this, the sequence controller 27
Energizes the semiconductor gas sensor 22 and the compressor 2
3 is started, valves 17 and 20 are opened, and container 2 is opened.
Gas is sampled from the inside of the tank 11 into 1 and the decomposition gas sensor 18 is set to an operating state. The time required for the decomposition gas sensor 18 to be in the operating state and for actual measurement is 10 to 20.
Need for minutes. This is the time required to warm up the sensor and to measure if decomposed gas is generated, should it occur. And the decomposition gas sensor 18
If there is no change in the resistance of the semiconductor gas sensor 22 due to contact with the sampled gas, no detection signal is output. On the other hand, if a partial discharge occurs in the winding 13 and SnO ₂ gas is generated, A change occurs in the resistance of the semiconductor gas sensor 22 to output a detection signal. This output signal is transmitted to the signal processing device 29 via the amplifier 30.
Since the output signal of the corona sensor 16 is held, if the active gas is detected by the decomposition gas sensor 18 as described above, it can be confirmed that partial discharge has occurred by the sum of both signals. The signal processing device 29 has a function of transmitting a signal to the display device 31 even if it slightly exceeds a preset threshold value (alarm level) for each signal to generate an alarm.

In this way, since the decomposition gas sensor 18 is operated when the corona sensor 16 performs the detection operation, the number of times the decomposition gas sensor 18 is operated can be extremely reduced. Therefore, the valve 1 composed of a solenoid valve
7, 20, 24, and the life of movable parts such as motors in the compressor 14 and parts that are easily consumed can be extended.
As a result, the life of the device can be extended.

The decomposition gas sensor 18 is operated by using an output signal of the corona sensor 16 as a trigger, and the timing is determined immediately after the partial discharge occurs and before the active gas is adsorbed by the adsorbent. Since the detection is performed, the active gas can be reliably detected. Therefore, when partial discharge has actually occurred in the tank 11, the partial discharge can be accurately detected. In addition, for an electromagnetic wave such as a broadcast wave, the decomposition gas sensor 18 does not detect the partial discharge. It can be reliably distinguished from the occurrence of discharge.

By operating the decomposed gas sensor based on the detection signal of the corona sensor as described above, it is possible to distinguish external electromagnetic waves such as broadcast waves from partial discharges. Due to the influence of the sensitivity characteristics of the above, it is expected that the partial discharge is not identified as occurrence of partial discharge. That is, in the SnO ₂ semiconductor gas sensor, the output signal includes dark noise irrespective of the generation of the decomposition gas generated by the partial discharge, and the noise increases in accordance with the operation time due to temporal deterioration during operation. It is conceivable that the sensitivity characteristic of the cracked gas sensor will be reduced.

Therefore, in this embodiment, for example, the background noise of the decomposition gas sensor is automatically measured by periodically measuring the background noise and automatically revising the threshold value of the decomposition gas sensor accompanying the background noise in a sequence. The maximum detection sensitivity of the SnO ₂ semiconductor gas sensor is used to detect a discharge such as a minute corona as much as possible.

The details of the operating state of the partial discharge detection method according to the present embodiment will be described with reference to the timing charts and flowcharts of FIGS. It should be noted that the sequence controller 27 has an internal clock (not shown) built-in, so that the decomposition gas sensor can be operated, for example, on a daily basis.

In FIG. 2, a trigger pulse is generated by an internal clock and used as a start signal. Start signal is usually once / week to 1 for regular check of dark noise
Repeat every 10 days. Until the start signal arrives, all except the sequence controller 27 are at rest. The sequence controller 27 gives a warm-up operation instruction to the decomposition gas sensor 18 that has been turned off by the start signal. Subsequently, calibration using a reference gas such as dry air that does not include SOF ₂ gas is also performed to check each part of the sensor. Subsequently, the sample gas is extracted from the transformer tank 11, and the presence or absence of the SOF ₂ gas and the actual measurement of the level are performed. Decomposition gas sensor 1
8 is the same as the output of the corona sensor 16, for example, DC
The signal is converted into a form such as 4 to 20 mA and
Is entered into (A) in FIG. 2 is a period during which the value that has reached the peak value during the change in the measured value is held. (B) is a period in which the peak value during the measurement is held after the measurement is completed. In FIG. 2, the current output value x from the decomposition gas sensor 18 indicates the background noise in which the SOF ₂ gas is not detected in this case. This current output value x is 4 mA if there is no SOF ₂ gas and there is no background noise.

FIG. 2 also shows the output value z of the corona sensor 16. When the corona sensor 16 receives nothing including external noise, the output value z is 4 mA. As shown in FIG. 2, the corona sensor output value z changes under the influence of external noise. FIG. 2 also shows the value of the threshold value y. The threshold value y is set to about y = x + 1 with a margin of, for example, +1 mA with respect to the current output value x of the decomposition gas sensor 18.

The method of setting the threshold value y will be described in more detail with reference to the flowchart of FIG. In the signal processing device 29, first, a threshold value ymA for determining whether or not SOF ₂ gas is generated is temporarily set in a range of 5 to 20 mA. The threshold value y can be set by the signal processing device 29 in which a microcomputer and a keyboard are installed. The provisional threshold value y can be set freely by operating the keyboard.

Then, the following flow is executed. The output value z of the corona sensor 16 is input to the signal processing device 29, and it is checked whether or not the output value z is 4 mA, that is, whether or not a signal including a corona is received at all. If the corona sensor output value z exceeds 4 mA,
Since there is a possibility that external noise has been received, the data is not used in that case. Conversely, the corona sensor output value z is 4
In the case of mA, the output value x of the semiconductor gas sensor 22 holding the above peak value is compared with the output value x in the signal processing device 29 by a threshold value y = x + α.
(Α: about 1 mA). The threshold value y is α = 1m
If A is set, it will be set in the range of 5 mA to 20 mA. The threshold value y can also be manually set by a human based on the above-described flowchart. However, the threshold value y needs to be reviewed every time a start signal is issued as shown in FIG. 2, so that it is generally preferable to form a sequence using a microcomputer and its software. In short, assuming that the corona sensor output value z is 4 mA at each timing, the threshold value y
And a flow of setting a new threshold value y = x + α may be repeatedly executed. The microcomputer and the software can be built in the signal processing device 29. An example in which the external noise is received by the corona sensor 16 and misdiagnosed as a corona is as follows.
According to the field test conducted at the actual substation conducted by the inventor for about one year and one month, the result is about once / 30 days, and the number of times the corona sensor output value z cannot be used due to practical misdiagnosis is not so large. However, if the corona sensor 16 generates any output including external electromagnetic wave noise, partial discharge may have occurred as described above, and at the same time, the output value x of the decomposition gas sensor 18 includes corona generation information. The data at that time will not be adopted because it may have been used.

As described above, the background noise caused by the degradation of the decomposition gas sensor 18 is periodically measured, and the threshold value of the decomposition gas sensor 18 is automatically reviewed based on the result. By utilizing the performance of the gas sensor 18 to the utmost, it is possible to detect a partial discharge as low as possible. In particular, the SnO ₂ semiconductor type gas sensor 22 used for the decomposition gas sensor 18 has a darkness due to the influence of an electric field which is constantly applied during operation, the influence of heat due to the ambient temperature, and the decomposition of SF ₆ gas and the presence of generated gas accompanying it. In equipment such as transformers, where noise tends to increase and maintenance-free is required, it is virtually impossible for customers to replace the slightly degraded SnO ₂ semiconductor gas sensor at the customer's site. It is. Therefore, the partial discharge detection method in which the sensitivity characteristic of the decomposition gas sensor is periodically reviewed as in the present embodiment is not limited to the detection of the partial discharge,
It is also extremely effective from a maintenance-free point of view.

In the above embodiment, the corona sensor 1
6 has been described as a system that captures the generation of electromagnetic waves, for example, an AE sensor that captures ultrasonic waves, an optical sensor that captures light,
Other types of partial discharge sensors, such as using a pulse current method signal that captures a pulse as a current as a trigger, can also be employed.

[0029]

According to the present invention, the occurrence of partial discharge can be accurately detected by operating the decomposition gas sensor with the output signal of the partial discharge sensor as a trigger, and the number of operations of the decomposition gas sensor is reduced, so that the life is sufficient. The sensitivity of the cracked gas sensor can be maximized by periodically measuring, for example, the background noise of the cracked gas sensor and reviewing the threshold value of the cracked gas sensor based on it. There is an effect that can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an apparatus to which a method for detecting partial discharge of electric equipment according to the present invention is applied.

FIG. 2 is a diagram showing a timing chart of a method for detecting partial discharge of an electric device according to the present invention.

FIG. 3 is a flowchart showing a partial discharge detection method for electric equipment according to the present invention.

[Explanation of symbols]

11 is a tank, 12 is an iron core, 13 is a winding, 16 is a corona sensor (partial discharge sensor), 18 is a decomposition gas sensor, 2
2 denotes a semiconductor gas sensor, 27 denotes a sequence controller, and 29 denotes a signal processing device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01R 31/12 G01N 27 / 00,27 / 12,27 / 20 H02B 13/00-13/06 H01H 33 / 00 H01F 27/00

Claims (2)

(57) [Claims] A partial discharge sensor for detecting a partial discharge generated inside an electric device and a decomposition gas sensor for detecting a decomposition gas generated by the generation of the partial discharge are provided, and the decomposition gas sensor is detected by a detection signal of the partial discharge sensor. In the method for detecting the partial discharge of the electrical device to be operated, the threshold value of the decomposition gas sensor is reviewed by periodically operating the decomposition gas sensor independently of the operation based on the detection signal of the partial discharge sensor. Partial discharge detection method for electrical equipment. 2. The method according to claim 1, wherein the threshold value of the decomposition gas sensor is reviewed by periodically measuring the dark noise of the decomposition gas sensor.