JPS6295923A - Protective relay of transformer - 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 ratio differential type protective relay device for a transformer.

[Conventional technology]

FIG. 2 is a circuit diagram showing a conventional transformer protective relay device of this type, and is shown in a single-phase representation. Same figure.

, AC is an alternating current power supply, 1 is the transformer to be protected,
2a is an instrument current transformer that detects the transformer input current (high voltage side) Tin, 2b is an instrument current transformer that detects the transformer output current (low voltage side) To, and 3a is a transformer input side breaker ,3
b is the transformer output side breaker, 4 is the OF cable within the protection zone (between the circuit breakers 3a and 3b), and 5 is the ground capacitance of the OF cable 4.

Reference numeral 6 denotes a protective relay device, which includes a suppressing force deriving circuit 6a, a differential force deriving circuit 6b, a ratio differential force determining circuit 6C1, an inrush current waveform determining circuit 6d, and an inhibit circuit 6e.

The suppressing force deriving circuit 6a receives the detected currents output from the instrument current transformers 2a and 2b, compares the magnitude thereof, and calculates a current proportional to the maximum value (absolute value of iinmax or absolute value of iomax) of the large detected current. Generates output (inhibitory force) IR.

The differential power deriving circuit 6b performs vector calculation of the detected currents output by the instrument current transformers 2a and 2b, and generates a current differential output (differential power) proportional to the difference 10 (=!in-'r
absolute value of o). The ratio differential power determination circuit 6C takes in the current proportional output IR and the differential power ID, and calculates 10/I.
The ratio of R is compared with a predetermined value of 1, and if the cough ratio is equal to the predetermined value of 1 or greater than the predetermined value of 1, an internal failure determination signal is generated. The inrush current waveform determination circuit 6d is the differential power derivation circuit 6.
This is to judge the degree of the second harmonic component 2 in the output 10 of b, and it enters when the ratio with the fundamental wave component 2/fl is equal to a predetermined value of 2 or greater than a predetermined value of 2. Generates a current judgment signal. The outputs of the ratio differential power determination circuit 6C and the inrush current waveform determination circuit 6d are guided to the inhibit circuit 6e.
When the former is at H level and the latter is at L level, a protective operation request signal (breaker trip signal) is generated.

Next, the operation of this device will be explained. For convenience of explanation, it is assumed that there is no charging current Ic due to the ground capacitance 5, and the magnitude of the current tin and the current 10 during normal operation of the transformer 1 is Assume they are the same. When an internal failure occurs in the transformer 1, a large fault current flows from the power supply AC side toward the transformer 1, so a differential output ID is generated from the differential power deriving circuit 6b, and 1 is established on (ID/IR). Therefore, the ratio differential power determination circuit 6C generates a failure determination signal. However, in this case, since the inrush current waveform determination circuit 6d does not output an inrush current determination signal,
A protection operation request signal is sent from the inhibit circuit 6e.

Next, when the circuit breaker 3a is closed, the excitation inrush current flows into the transformer 1, so the ratio differential power determination circuit 6C outputs an output, but in this case, the inrush current waveform determination circuit 6d outputs Therefore, the inhibit circuit 6e does not send out a protection operation request signal.

FIG. 3 shows the protective operation characteristics of the above-mentioned protective relay device, in which the magnitude of the current when the transformer 1 is operated at its rated capacity is expressed as 100%. The shaded area A in the figure is the internal failure detection operating range.

The range from IR=O to 100% is the load current region of the transformer, and usually a margin KO is provided for the current differential error caused by the transformer's tap changer, instrument current transformer, etc., and l0= Ko
% (Ko is generally about 30%) or more, and when IR-≧-100%, in order to avoid penetration error in the event of an external failure, (ID /IR) > K (K is 0
．． 3 to 0.5). In the figure, B is the differential error area at load current, and C is the differential error area at the time of external failure.

[Problem that the invention seeks to solve]

By the way, there is an OF cable 4 within the above protection zone of the transformer 1.
is used, there is a charging current 1c due to its ground capacitance 5, and a charging current ic flows in addition to the current iin on the output side of the instrument current transformer 2a, so a differential output 10=1itn+'tc-iol,
This becomes a new differential error. This charging current Ic can reach 10 to 15% of the rating, so in order to avoid malfunctions due to differential errors, the above KoO value should be set to 30%.
It is necessary to increase the internal failure determination sensitivity from 1 to 50% to lower the internal failure determination sensitivity, which poses a problem in that highly sensitive failure determination cannot be performed.

This invention was made in order to solve the above-mentioned problems, and is a protective relay for transformers that can detect internal failures with high sensitivity without reducing the failure judgment sensitivity even when the differential error is large. The purpose is to obtain equipment.

[Means to solve the problem]

In order to achieve the above object, the present invention adds a differential error correction circuit that generates a differential error that is known in advance, and uses the output of the differential error correction circuit to generate a differential output. The configuration is such that the dynamic output is corrected.

[Effect]

In this invention, since the differential error that is known in advance and cannot be ignored is canceled from the differential output of the circuit that calculates the differential component of the transformer input/output current, the determination sensitivity of the ratio differential power generation circuit is is prevented from being influenced by the differential error.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention, which has a differential output correction circuit 6f and an adder circuit 6g, and the output of the adder circuit 6g is supplied to a ratio differential power determining circuit 6C. This is different from the conventional case shown in FIG. The other configurations are the same as those in FIG. 2, and are designated by the same reference numerals.

Next, the operation of this device will be explained.

The differential correction circuit 6f corrects the differential error that is known in advance,
In this embodiment, the differential error Δ+D corresponding to the charging current 1c of the ground capacitance 5 of the OF cable 4 is set, and the cough differential error ΔID=ic is determined by the addition circuit 6g and the differential output I
It is added to D in the direction of (ID-ΔID). Since the differential output i[1=iin+1c-4o, the adder circuit 6
Since the output of g is a Jansell'ed value, the determination sensitivity of the ratio differential power determination circuit 6C is prevented from decreasing due to the charging current portion 1c. Other operations are the same as in the conventional case.

In addition, in the above embodiment, the case where the differential error caused by the ground capacitance within the protection zone is corrected is explained.
The differential error to be corrected is not limited to this,
By correcting the non-negligible differential error with respect to the current differential output, the determination sensitivity of the ratio differential power determination circuit can be increased.

Furthermore, although the above-mentioned embodiment deals with a protective relay device for a transformer, the present invention can be practiced and similar effects can be obtained with any differential type protective relay device.

〔Effect of the invention〕

As explained above, this invention corrects the differential output using a differential error correction circuit that generates a differential error that is known in advance, so even if there is a differential error factor that cannot be ignored, this will improve the judgment sensitivity. Since the influence on the transformer can be eliminated, internal faults in the transformer can be detected without reducing the determination sensitivity, and reliability can be improved.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing a conventional transformer protection relay device, and Fig. 3 is a general protective operation characteristic diagram of a transformer protection relay device. be. In the figure, 1 - transformer, 2a, 2b - instrument current transformer, 6a - restraining force deriving circuit, 6b - differential power deriving circuit, 60
-Ratio differential power determination circuit, 6d--inrush current waveform determination circuit, 6e--inhibit circuit, 6f-differential error correction circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A circuit that takes the input and output current of a transformer through a current transformer and generates a current proportional output proportional to the current value on the larger side, takes the input and output current of the transformer through the current transformer, and calculates the difference between the two currents. a circuit that generates a differential output proportional to the dynamic component, a ratio differential determination circuit from which the current proportional output and the differential output are derived, an inrush current waveform determination circuit from which the differential output is derived; In a ratio differential type protection relay device for a transformer, the output of the determination circuit becomes a transformer protection request signal under the condition that there is no output from the inrush current waveform determination circuit. A protective relay device for a transformer, characterized in that a dynamic error correction circuit is added, and the differential output is corrected by the output of the differential error correction circuit.