JPS63234830A - Transformer protecting differential relay - 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 [Field of Industrial Application] The present invention relates to a transformer protection differential relay device for protecting a power transformer.

[Conventional technology]

FIG. 3 is a configuration diagram showing an example of a conventional transformer protection differential relay device.
R is the protected transformer, CB H is this protected transformer MTR
High voltage side breaker, CT.

is the high voltage side current transformer of the protected transformer MTR, and the high voltage side relay current IRM flows through the secondary side of this high voltage side current transformer CT after the breaker CB is turned on. CTL is a low voltage side current transformer of the protected transformer MTR, and a low voltage side relay current IRL flows through the secondary side of this low voltage side current transformer CTL after the breaker CBH is turned on. 1 is a ratio differential element, 2 is a fundamental wave filter,
A second harmonic filter consisting of a second harmonic filter and a comparison rotation
This second harmonic detection element 2 is a harmonic detection element, and this second harmonic detection element 2 is a fundamental wave component 1fl and a second harmonic component If2 included in the input current.
An output is generated when the relationship ■f2/■f1<K is obtained between ing). 3 is an AND circuit, and F is an internal failure point.

Next, the operation will be explained.

When the breaker CB is turned on and the protected transformer MTR is energized, the excitation inrush current (inrush current) Ie at that time
Therefore, the high voltage side relay current IN+ (and the low voltage side relay current
The differential current 1d resulting from the combination with 1 is the inrush current Ie
For example, a time T of 0.1 to several seconds corresponding to the duration of
eContinue. This differential current 1d also causes the ratio differential element 1 to open for the time Te. In this case, the operating time and return time of the ratio differential element 1 are both 10 m5, for example.

In addition, at this time, the second harmonic detection element 2 has a ratio of the second harmonic component 1fZ to the fundamental wave component Ifl of the differential current Id for inrush current, that is, ■, 2/It+ is larger than the set value. Therefore, no output is generated (see Figure 4). Therefore, since the output of the ratio differential element 1 is given as an input to the AND circuit 3, no trip signal is output.

Furthermore, when an internal fault occurs, the ratio differential element 1 operates due to the differential current 1d flowing through the differential circuit due to the internal fault current. In addition, since the second harmonic component Irz is hardly included in the internal fault current, the ratio of the second harmonic component lff0 to the fundamental wave component 1fl of the differential current rd is less than the set value, so the second harmonic component Irz is less than the set value. The harmonic detection element 2 also operates. Therefore, the outputs from the ratio differential element 1 and the second harmonic detection element 2 are input to the AND circuit 3, and a trip output is output.

[Problems to be Solved by the Invention] Since the conventional transformer protective relay device is configured as described above, when an internal failure occurs, the operating time of the ratio differential element 1 (
In the above example, the second harmonic detection element 2 provided as a countermeasure against inrush current takes a determination time of 30 m5 due to the response delay of the filter circuit of its component circuit, even though the speed is sufficiently high for 10 m5). Therefore, the time required for the trip output to occur is as slow as 30 IllS, which poses a problem in that damage to the protected transformer and adverse effects on the power system cannot be minimized in the event of a failure.

This invention was made to solve the above-mentioned problems, and provides a transformer that can greatly speed up the trip time, thereby minimizing damage to the protected transformer and the negative impact on the power system in the event of a failure. The purpose of this invention is to obtain a differential relay device that protects the device.

[Means for solving problems]

The transformer protection differential relay device according to the present invention connects ratio differential elements to the secondary sides of the high voltage side current transformer and the low voltage side current transformer of the protected transformer, and A sudden voltage drop detection element is connected to , and a delay circuit is provided to delay the return of the output of this sudden voltage drop detection element for a certain period of time, and the output of the ratio differential element is connected to the output of the high voltage side current transformer and the low voltage side current transformer. It is equipped with a logic circuit that obtains the logical product of the output of the second harmonic detection element connected to the secondary side or the logical product of the output of the ratio differential element and the output of the delay circuit as a trip output. be.

[Effect]

In the transformer protection differential relay device according to the present invention, the voltage sudden drop detection element operates when an internal fault occurs, and a trip output is obtained by operating the ratio differential element without waiting for the second harmonic detection element to operate. This is what I did.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a configuration diagram showing one embodiment of the present invention, and the same components in FIG. 1 as in FIG. 3 are given the same reference numerals, and the explanation thereof will be omitted. In Figure 1, PT is the protected transformer M
The high-voltage side voltage transformer installed on the high-voltage side of TR, PTL is the low-voltage side voltage transformer installed on the low-voltage side of the protected transformer MTR, and 4 is connected to the secondary side of the above-mentioned high-voltage side voltage transformer PT. This is a sudden voltage drop detection element that operates when the change in input voltage fluctuates more than the set value. Reference numeral 5 denotes a sudden voltage drop detection element connected to the secondary side of the low-voltage side voltage transformer PTL, which is activated when the amount of change in the input voltage fluctuates more than a set value. The set value of these voltage sudden decrease detection elements 4 and 5 is, for example, 10% of the rated voltage, and the device operates if the amount of change is equal to or greater than this value. In addition, the operating time in this case is 5m.
It is about S. 6.7 is an OR circuit, and 8 is a delay circuit that delays the output from the OR circuit 6 for a certain period of time.The delay time of this delay circuit 8 is set to, for example, 60 m5, which is longer than the trip time of the breaker CB. (2) is the secondary voltage of the high voltage transformer PT.

Next, the operation will be explained.

When the breaker CBH is turned on, the second harmonic detection element 2 prevents unnecessary response to inrush current.

Further, when an internal failure occurs, the ratio differential element 1 and the second harmonic detection element 2 operate in the same manner as the conventional one shown in FIG.

On the other hand, the voltage sudden decrease detection element 4.5 operates immediately (approximately 5 m5 in this embodiment) after the internal failure occurs (see Fig. 2).
4) (see (5)), the OR circuit 6 is the voltage sudden decrease detection element 4.
The delay circuit 8 delays the output of the OR circuit 6 for a certain period of time. Then, the output from the delay circuit 8 is given to the input of the AND circuit 3 via the OR circuit 7, and after waiting for the operation of the ratio differential element 1 (see FIG. 2 (1)), the trip output is output from the AND circuit 3. obtain. Therefore, the trip output from the AND circuit 3 is output at a high speed of 10 m5 after the internal failure occurs, which is the operating time of the ratio differential element 1, without waiting for the operation of the second harmonic detection element 2 (see Fig. 2 (2)). (see Figure 2).

In the above embodiment, the case where the protected transformer VTR is a two-winding transformer has been described, but the invention can be similarly applied to a three-winding transformer.

Furthermore, in the above embodiment, the voltage sudden drop detection element 4.5 is provided on both the high voltage side and the low voltage side of the protected transformer MTR in order to detect internal failure with high sensitivity. good.

〔Effect of the invention〕

As described above, according to the present invention, the transformer protection differential relay device detects an internal failure with the voltage 2+ and voltage detection elements, and outputs the ratio differential element regardless of the presence or absence of the output of the second harmonic detection element. The structure is configured to trip only when the protected transformer is tripped, so it is highly sensitive and can detect minor faults, and the trip time can be significantly speeded up, thereby minimizing damage to the protected transformer and the negative impact on the power system when it fails. There is an effect that can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a transformer protection differential relay device according to an embodiment of the present invention, Fig. 2 is a time chart for explaining the operation of Fig. 1, and Fig. 3 is a block diagram of a conventional transformer protection differential relay device. A block diagram showing an example of a protective differential relay device, and FIG. 4 is a time chart for explaining the operation of FIG. 3. 1 is a ratio differential element, 2 is a harmonic detection element, 3 is an AND circuit, 4.5 is a voltage sudden decrease detection element, 6.7 is an OR circuit, 8
is a delay circuit, VTR is a protected transformer, CT is a high voltage side current transformer, CTL is a low voltage side current transformer, PT is a high voltage side voltage transformer, and PTL is a low voltage side voltage transformer. indicate the same or equivalent part. (2 others)

Claims (1)

[Claims] A ratio differential element connected to the secondary side of the high voltage side current transformer and the low voltage side current transformer of the protected transformer, and a ratio differential element connected to the secondary side of the high voltage side current transformer and the above low voltage side current transformer, respectively. a second harmonic detection element connected to the second harmonic detection element; and a sudden voltage drop detection element connected to the secondary side of a voltage transformer installed on at least one of the high voltage side and the low voltage side of the protected transformer;
A delay circuit that delays the return of the output of the sudden voltage drop detection element for a certain period of time, and the AND of the output of the ratio differential element and the output of the second harmonic detection element, or the output of the ratio differential element and the delay A transformer protection differential relay device comprising a logic circuit that obtains a trip output by ANDing with the output of the circuit.