JPH0548052B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an operation monitoring device for a transformer load tap changer (hereinafter referred to as a tap changer), and particularly to a device for constantly monitoring the bridging current during tap change. In particular, the present invention relates to a device for early detection of abnormality in a touch engineer.

[Conventional technology]

When a transformer's tap engineer changes the voltage ratio while power is being applied, it temporarily shorts the taps in the transformer's tap windings to be changed through a resistor or reactor. If it does not work or if the resistor or reactor is damaged, an excessive short circuit current will occur between the taps of the tap winding, leading to a major accident.

In order to prevent this accident and operate the transformer normally, we have traditionally monitored the number of operations of the touch engine and replaced parts when the number of operations reached the specified number, as well as preparing switching operations when the touch engine is operating. Although time monitoring including time is performed, bridging current is not monitored, so it is difficult to grasp precursory phenomena of abnormalities, and it cannot be said to be sufficient as a method for predicting abnormalities.

On the other hand, during patrol inspections conducted by humans, abnormalities may be discovered based on the difference between the tap changeover sound and the normal sound, but this audible abnormality detection requires the patrolman to approach the transformer, and the This is limited to cases where various conditions are met, such as the switching operation being performed and the patrolman being able to determine whether the target touch engineer is normal or abnormal based on the switching sound. This method required a high level of skill on the part of the patrol personnel, and it was not sufficient as an abnormality detection method, such as the inability to perform constant monitoring.

[Summary of the invention]

The present invention eliminates the drawbacks of the conventional touch engine monitoring method described above, performs constant monitoring, directly detects the bridging current, and processes it for judgment, thereby automatically detecting abnormalities in the touch engine at an early stage. The purpose is to provide a device for discovery.

To achieve this object, the present invention provides an operation monitoring device for a load-time tap switching device for a transformer of a switching type in which a current limiting means short-circuits the tap winding when the tap is switched. a first current detecting means for detecting a superimposed current in which a bridging current and a load current flowing to the current limiting means connected to the first tap are superimposed when the tap is switched; a second current detection means for detecting the load current flowing through the current limiting means when the switch is switched to the second tap, and a load current detected by the superimposed current and the second current detection means; A transformer characterized by comprising: determining means for determining a bridging current and comparing the bridging current with a reference bridging current during normal operation to determine whether or not there is an abnormality in the load tap switching device of the transformer. There is an operation monitoring device for the tap switching device under load.

[Embodiments of the invention]

FIG. 1 is a block diagram of a monitoring device showing an embodiment of the present invention, in which 1 is a tap winding of a transformer, 2 is a tap engine body connected to tap leads 3A to 3C from tap winding 1. Tap selector fixed contacts 4A to 4C, tap selector movable contacts 5A and 5B, current limiting resistors (or reactors, etc.) 6A to suppress short-circuit current when switching taps
6D, fixed arc contacts 7A to 7F, and movable arc contacts 8A to 8F which are connected to and released from the fixed arc contacts 7A to 7F from the switching drive mechanism 10 via the insulated drive shaft 9 are built in. 1
1A and 11B are current sensors that detect the current flowing through the current limiting resistors 6A to 6D, 12 is an operation monitoring device, and 13 and 13B are current sensors 11A and 1.
A signal conversion circuit that converts a 1B signal into a predetermined electrical signal according to the magnitude of current, 14A and 14B are sample and hold circuits, 15 is a multiplexer, 1
6 is an analog-digital conversion circuit (hereinafter referred to as A/
17 indicates a control/arithmetic processing section. In addition, in the figure, the solid arrow line shows the transmission path of the signal, the broken line of the arrow shows the transmission path of the control signal from the control/arithmetic processing unit 17, and the arrow i _l flows to the current limiting resistors 6A to 6D. current, and i _L indicates the load current.

In the operation monitoring device for the transformer on-load tap switching device configured as described above, when switching the tap position from the tap selector fixed contact 4B to 4C, the tap selector movable contact 5B is first connected to the tap fixed contact 4C. Ru. Next, the switching drive mechanism 10 moves the movable arc contacts 8A to 8F through the insulated drive shaft 9 from right to left toward the page, that is, movable arc contacts 8A to 8
F is combined with fixed arc contacts 7A to 7F to short-circuit or open two pairs at a time. At this time, the tap leads 3B and 3C of the tap winding 1 are bridged, for example, through the current limiting resistor 6B, contacts 7C, 8C, contacts 8D, 7D, and the current limiting resistor 6C, and the current limiting resistors 6A to 6D As shown in FIG. 2, a current i l that is a superposition of a bridge (short circuit) current i _S due to the voltage between the switching taps and _a load current i _L flows. As is clear from Fig. 2, the current limiting resistor 6A~
6D is the actual tap switching time, and at this time, an arc is generated between the fixed arc contacts 7A to 7F and the movable arc contacts 8A to 8F to open and close the short circuit current. The switching drive mechanism 10 has a built-in interlocking device using a spring or the like to shorten the arc time in order to reduce oil contamination and contact wear. 9 to the movable contacts 8A to 8F, and are switched in approximately several tens of milliseconds.

At this time, if the current limiting resistors 6A to 6D are partially damaged or partially short-circuited due to some kind of conductive foreign object, the resistance value becomes smaller than the predetermined value, so the bridging current at the time of tap switching (I _l in Figure 2
~i _L ) increases. When switching the taps of the tap engineer 2, the current limiting resistors 6A to 6A
A current sensor 11 such as an optical CT detects the current _flowing to 6D.
A and 11B detect, sensor 11A and 11B
signal converters 13A and 13B, respectively.
converts it into a predetermined electrical level signal, temporarily holds the electrical signal in sample and hold circuits 14A and 14B, switches between sample and hold circuits 14A and 14B with multiplexer 15, and converts the A/D
The conversion circuit 16 converts it into a digital signal and stores it in the control/arithmetic processing section 17.

The control/arithmetic processing unit 17 performs such data acquisition several tens to hundreds of times within the actual tap switching time of several tens of milliseconds, and after completing the data acquisition, the superimposed current i _l
Find the difference i _S = i _l − i _L between the current and load current i _L to obtain the bridging current i _S.

Furthermore, the control/arithmetic processing section compares the insulation values of these tens to hundreds of calculated bridging currents i _S to find the maximum value Is _MAX , compares it with a preset maximum bridging current value, and calculates the measured value IS _MAX . If the value is large, it is determined that there is an abnormality and an alarm is issued.

〔Effect of the invention〕

As described above, the present invention is designed to reduce bridging current, which is a pre-driving phenomenon of abnormality of a tap-engine, by using a switching type transformer load tap-changing device (tap-engineer) in which a resistor or the like is short-circuited during tap-switching. The system provides a monitoring device that detects abnormalities or signs of abnormalities in the touch engine by detecting the current flowing through the load current and the load current, and detects abnormalities automatically and with higher accuracy than conventional monitoring methods. This has the effect of allowing early detection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a graph showing the relationship between currents in various parts of the touch engineer. In the figure, 1 is a tap winding, 2 is a tap changer under load, 6A to 6D.
is a current limiting resistor, 11A, 11B are current sensors, 1
2 is an operation monitoring device, 13A and 13B are signal conversion circuits, 14A and 14B are sample and hold circuits, 1
5 is a multiplexer, 16 is an A/D conversion circuit, 1
7 is a control/arithmetic processing section. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. In an operation monitoring device for a load-time tap switching device for a transformer of a switching type in which a current limiting means short-circuits a tap winding when the tap is switched from the first tap to the second tap. , a first current detection means for detecting a superimposed current obtained by superimposing a bridge current and a load current flowing in a current limiting means connected to the first tap; and switching from the first tap to the second tap. a second current detection means for detecting a load current flowing through the current limiting means; determining a bridging current from the superimposed current and the load current detected by the second current detection means; and determining means for comparing this bridging current with a normal standard bridging current to determine whether or not there is an abnormality in the transformer on-load tap switching device. Driving monitoring device. 2. The determination means includes first and second signal conversion circuits that convert the signals of the first and second current detection means into appropriate electrical signal levels, and outputs of the first and second signal conversion circuits. first and second sample-and-hold circuits that temporarily hold signals, respectively; a multiplexer that switches between the first and second sample-and-hold circuits; an A/D conversion circuit that converts the analog signal from the multiplexer into a digital signal; The bridging current i _S = i _l −i _L is calculated from the superimposed current i _l and load current i _L corresponding to the digital value by storing the digital signal, and calculating the bridging current i _S
The invention is characterized in that it is equipped with a control/arithmetic processing unit that calculates the predetermined number of times within the actual tap switching time, determines that there is an abnormality when the maximum value exceeds the reference value, and generates an alarm signal. An operation monitoring device for a transformer on-load tap switching device according to scope 1.