JPS63234828A - 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, CBH is the breaker on the high voltage side of this protected transformer MTR, and CTH is the high voltage side current transformer of the above protected transformer MTR, and on the secondary side of this high voltage side current transformer CTH. The high voltage side relay current IRH flows after the circuit breaker CBH is turned on. CTL is the low voltage side current transformer of the protected transformer MTR,
A low voltage side relay current RL flows through the secondary side of this low voltage side current transformer Cr t after the breaker CBH is turned on. 1 is a ratio differential element, 2 is a second harmonic detection element composed of a fundamental wave filter, a second harmonic filter, and a comparison rotation, and this second harmonic detection element 2 detects the fundamental wave component contained in the input terminal. I tz/I between Iff and the second harmonic component 1f2
An output is generated when the relationship r+<K is obtained (however, K is a set value for reliably detecting inrush current, and is usually about 0.15).

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 I□ and the low voltage side relay current TII
The differential current rd combined with L 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 l are both 10 m5, for example.

In addition, the second harmonic detection element 2 at this time is a second harmonic component 1. Since the ratio of I,2/IfI is larger than the set value, 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.

Further, when an internal fault occurs, the ratio differential element 1 operates due to the differential current Id flowing through the differential circuit due to the internal fault current. Furthermore, since the second harmonic component IfZ is almost not included in the internal fault current, the ratio of the second harmonic component If2 to the fundamental component r+ of the differential current Td is less than the set value. The second harmonic detection element 2 also operates. Therefore, the AND circuit 3 receives the outputs from the ratio differential element 1 and the second harmonic detection element 2, and outputs a trip output.

[Problem that the invention seeks to solve]

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 trip output to occur is as slow as 30 m5, 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 , a delay circuit is provided to delay the return of the output of the sudden voltage drop detection element for a certain period of time, and the logical product of the output of the ratio differential element and the output from the delay circuit is used as the trip output. It is equipped with an AND circuit.

[Function] The transformer protection differential relay device of the present invention does not operate when a breaker is closed, but operates when an internal fault occurs, and provides a trip output when a ratio differential element operates.

〔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, PT, installed on the high-voltage side of TR is the low-voltage side voltage transformer installed on the low-voltage side of the protected transformer MTR, and 4 is the secondary side of the high-voltage side voltage transformer PH1 (PT). The connected voltage sudden drop detection element operates when the change in input voltage fluctuates more than the set value. 5 is the voltage sudden drop detection element connected to the secondary side of the low voltage side voltage transformer PTL, and the input voltage The voltage sudden drop detection element 4.5 operates when the change in voltage is larger than the set value.The set value of these voltage sudden decrease detection elements 4.5 is, for example, 10% of the rated voltage, the operating time and recovery time are both about 5 mS, and 6 is the OR value. The circuit 7 is a delay circuit that delays the output from the OR circuit 6 for a certain period of time, and the delay time of the delay circuit 7 is set to, for example, 60 m5, which is longer than the trip time of the circuit breaker CB□.■ is the high voltage side voltage. This is the secondary voltage of transformer PTH.

Next, the operation will be explained.

When circuit breaker CB is closed, ratio differential element 1 operates, but
Since the voltage sudden decrease detection element 4.5 does not operate, the trip output is not outputted unnecessarily.

On the other hand, when an internal fault occurs, the ratio differential element 1 operates due to the differential current 1d due to the internal fault current. In addition, since the voltage sudden drop detection elements 4 and 5 operate immediately after the occurrence of an internal failure (approximately 5 m5 in this embodiment) (Fig. 2 (4) and (5))
), the output from the voltage sudden drop detection element 4.5 is inputted to a delay circuit 7 via an OR circuit 6, and the delay circuit 7 delays the output of the OR circuit 6 for a certain period of time. The output from the delay circuit 7 is then given to the AND circuit 3, and after waiting for the operation of the ratio differential element l (see FIG. 2 (1)), a trip output is obtained from the AND circuit 3. Therefore, the trip output from the AND circuit 3 is obtained at a high speed of, for example, 10 m5 when the ratio differential element 1 operates, that is, after the internal failure occurs (see FIG. 2).

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

Further, in the above embodiment, the voltage sudden decrease detection element 4.5 is provided on both the high voltage side and the low voltage side of the protected transformer VTR in order to have high sensitivity immediately after the occurrence of an internal failure. 4.5 may be applied only to either the high pressure side or the low pressure side.

〔Effect of the invention〕

As described above, according to the present invention, the transformer protection differential relay device replaces the conventionally used second harmonic detection element with a voltage that does not operate when voltage is applied to the protected transformer, but operates when a system failure occurs. A sudden decrease detection element is installed, and the configuration is such that the trip output is obtained by the AND of the output of the ratio differential element and the output of the voltage i, m detection element, so the trip time can be significantly shortened with an extremely simple configuration. Therefore, it is possible to minimize damage to the protected transformer and the adverse effects on the power system when the protected transformer fails.

[Brief explanation of drawings]

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, 3 is an AND circuit, 4.5 is a sudden voltage drop detection element, 6 is an OR circuit, VTR is a protected transformer, CT
, cTL is a high-voltage side current transformer, PTH is a high-voltage side voltage transformer, and PTL is a low-voltage side voltage transformer. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A ratio differential element connected to the secondary sides of the high-voltage side current transformer and the low-voltage side current transformer of the protected transformer, and a ratio differential element installed on at least one of the high-voltage side or the low-voltage side of the protected transformer. a sudden voltage drop detection element connected to the secondary side of the voltage 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 an output of the ratio differential element and an output of the delay circuit. A transformer protection differential relay device equipped with an AND circuit that obtains a trip output by the logical product of