JPH0465613B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a protective relay device for a ratio differential type transformer.

[Conventional technology]

FIG. 2 is a block diagram showing a conventional protective relay device for a transformer, and is shown in a single-phase representation.

In Figure 2, 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) Iin, and 2b is the transformer output current (low voltage side). ) Io is detected by the instrument AC, 3a is the transformer input side shield breaker, 3b is the transformer output side shield breaker, 4 is the protection zone (the shield breaker 3a,
3b), and 5 is the ground capacitance of the OF cable 4. 6 indicates a protective relay device,
Suppression force derivation circuit 6a, differential force derivation circuit 6b, ratio differential force determination circuit 6c, rush current waveform determination circuit 6
d, an inbit circuit 6e, and the suppressing force derivation 6a compares the magnitude of the detection currents output by the instrument current transformers 2a and 2b, and determines the maximum value of the large detection current (the absolute value of i _ionax or the absolute value of i _pnax) . Generates a current proportional output (repression force) IR proportional to the current value). 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) ID (=absolute value of i _io - i _p ) proportional to the difference. occurs.

The ratio differential power determination circuit 6c takes in the current proportional output IR and the differential power ID, and sets the ratio of ID/IR to a predetermined value K1.
and whether this ratio is equal to the predetermined value K1 or the predetermined value
If it is larger than K1, an internal failure determination signal is generated.

The inrush current waveform determination circuit 6d is the differential power derivation circuit 6.
This is to determine the degree of the second harmonic component f2 in the current differential output ID of b, and the ratio of the fundamental wave component (f2/f1)
is equal to or larger than the predetermined value K2, an inrush current determination signal is generated.

The inhibit circuit 6e is a ratio differential power determination circuit 6.
c and the output of the inrush current waveform determination circuit 6d, and when the former is at H level and the latter is at L level, a protective operation request signal (shrink 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 magnitudes of the current i _io and the current i _p when the transformer 1 is operating normally. Assume that the values are the same.

If an internal failure occurs in transformer 1, the AC power supply
Since a large fault current flows from the AC side toward the transformer 1, a current differential output ID is generated from the differential power deriving circuit 6b, and (ID/IR)≧K1 is established, so the ratio differential power A 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 out from the inhibit circuit 6e.

Next, when the shield breaker 3a is turned on, the excitation inrush current flows into the transformer 1, so the ratio differential power determination circuit 6c outputs an output, but the inrush current waveform determination circuit 6d also outputs an output. , inhibit circuit 6
e does not send a protection operation request signal.

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

The range of IR = 0 to 100% is the load current range of the transformer 1, and normally there is a tolerance Ko for current differential errors caused by the tap changer of the transformer 1, the instrument current transformer, etc.
In order to set the characteristic of operating above ID=Ko% (Ko is generally about 30%), and to avoid the penetration error in the event of an external failure when IR≧100%, (ID/IR)>
It has a characteristic of operating at K (K is about 0.3 to 0.5).

Note that B is the differential error range at load current, and C is the differential error range at the time of external failure.

FIG. 3b is a simplified diagram showing the protective relay device of FIG. 2.

[Problem that the invention seeks to solve]

Since the conventional protective relay device for a transformer is configured as described above, there is a charging current Ic due to its ground capacitance 5, and a charging current Ic added to the current _iio is on the output side of the instrument current transformer 2a. Since the current i _c flows, the differential output ID=|i _io +i _c −i _p |, which becomes a new differential error. This charging current I _c is 10-15% of the rating
Therefore, in order to avoid malfunctions due to differential errors, the value of tolerance Ko should be increased from 30% to 50%.
% to lower the internal failure determination sensitivity, and the problem that high-sensitivity failure determination could no longer be performed has disappeared.

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

[Means for solving problems]

A protective relay device for a transformer according to the present invention is provided with a differential error value output circuit that generates a differential error (charging current error) that is known in advance, and a circuit breaker provided at both ends of the transformer. The configuration is such that the current differential output output from the differential power deriving circuit is corrected by the output of the differential error value output circuit only when either one of the differential power deriving circuits is turned on.

[Effect]

The protective relay device for a transformer according to the present invention converts the differential output of a differential power deriving circuit that calculates the difference between the input and output currents of the transformer into a differential output that generates a differential error value that is known in advance and cannot be ignored. Corrected by the output of the dynamic error value output circuit.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 1, 30a, 30b and disconnector 3
Auxiliary contacts that work with a and 3b, 6f is a differential error value output circuit that outputs a differential error value known in advance, and 6g is the operational output of auxiliary contact 30a or 30b and the differential error value output circuit 6f outputs. 6h is an adder that adds the current differential output ID output from the differential force deriving circuit 6b and the differential error value ΔID.

Since the other configurations are the same as those in FIG. 2, the same reference numerals are given and explanations are omitted.

Next, the operation will be explained.

The differential error value output circuit 6f is set with a differential error value known in advance, in this embodiment, a differential error value ΔID corresponding to the charging current Ic of the ground capacitance 5 of the OF cable 4, Only when either one of the disconnectors 3a and 3b provided at both ends of the transformer 1 is turned on, the differential error value ΔID=I _c is determined by the addition circuit 6h.
The current is added to the differential output ID in the direction of (ID - ΔID). This current differential output ID = (i _io + _ic − i _p )
Therefore, the output of the adder circuit 6h is |i _io −i _p |, which is the value in which the differential error component i _c has been corrected (cancelled), and the determination sensitivity of the ratio differential power determination circuit 6c based on the charging current component i _c is Deterioration is prevented.

When the shield breaker 3a and/or 3b is not turned on, the differential error value ΔID is added to the adder 6.
Since the protection operation request signal is not supplied to h, an erroneous protection operation request signal is no longer output.

Other operations are similar to the conventional example.

In addition, although the above-mentioned embodiment explained the case where the differential error caused by the ground capacitance 5 within the protection zone is corrected, the differential error to be corrected is not limited to this, and the current differential By correcting the differential error that cannot be ignored with respect to the output, the determination sensitivity of the ratio differential power determination circuit 6c can be increased. Furthermore, the present invention can be applied to differential type protective relay devices other than transformer protective relay devices, and similar effects can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the current differential output can be corrected using the differential error value outputted from the differential error value output circuit, which is known in advance. Since it is possible to eliminate the influence on the judgment sensitivity even if there is a problem, it is possible to detect an internal failure of the transformer without reducing the judgment sensitivity, and there is an effect that the reliability can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a protective relay device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional protective relay device, and FIG. 3a is a general protective operation of the protective relay device. The characteristic diagram, FIG. 3b, is a simplified diagram showing the protective relay device. In the figure, 1 is a transformer, 2a, 2b are instrument current transformers, 3a, 3b are breaker, 30a, 30b
is an auxiliary contact, 6 is a protective relay device, 6a is a suppression force derivation circuit, 6b is a differential power derivation circuit, 6c is a ratio differential power determination circuit, 6d is an inrush current waveform determination circuit, 6e
6f is an inhibit circuit, 6f is a differential error value output circuit, 6g is an AND circuit, and 6h is an adder. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1 A restraining force derivation circuit that takes in the input/output current of the transformer via the current transformer and generates a current proportional output proportional to the current value on the larger side of the input/output current, and a differential derivation circuit that takes in the current proportional output and generates a differential output proportional to the difference between the input and output currents, a ratio differential power determination circuit that takes in the current proportional output and the differential output, and a ratio differential power determination circuit that takes in the differential output. Equipped with an inrush current waveform determination circuit,
In a protective relay device for a transformer that uses the output of the ratio differential power determination circuit as a transformer protection request signal on the condition that there is no output of the inrush current waveform determination circuit, a differential error value known in advance is output. A differential error value output circuit is provided, and the differential output is generated by the output of the differential error value output circuit only when either one of the disconnectors or disconnectors provided at both ends of the transformer is turned on. A protective relay device for a transformer characterized by compensation.