CN110768210A - Transformer protection current abrupt change starting method and transformer protection device - Google Patents

Abstract

The invention relates to a current sudden change starting method for transformer protection and a transformer protection device. The method includes: when a current sensor on a certain side of the transformer has a disconnection fault, the current sudden change of the transformer, the zero sequence voltage and the negative sequence voltage on the corresponding side of the transformer are analyzed. , the zero-sequence voltage mutation and the negative-sequence voltage mutation; when the current mutation of a phase on the high-voltage side or medium-voltage side of the transformer is greater than the current mutation threshold, the zero-sequence voltage, negative-sequence voltage, and zero-sequence voltage of the corresponding side of the transformer When the mutation amount or negative sequence voltage mutation amount is greater than the voltage threshold value, the control starting element starts; when the current mutation amount of a phase on the low voltage side of the transformer is greater than the current mutation amount threshold value, the negative sequence voltage or negative sequence voltage mutation amount on the corresponding side of the transformer is greater than the voltage When the threshold value is reached, the control activation element is activated. The invention realizes that even when the current sensor on one side of the transformer is disconnected, the current sudden change starting element can still be started reliably.

Description

Transformer protection current sudden change start method and transformer protection device

technical field

The invention belongs to the technical field of power system relay protection, and particularly relates to a current sudden change starting method for transformer protection and a transformer protection device.

Background technique

In the prior art, the current sudden change starting element detects the change of the current of each phase in real time through an effective current sensor to determine whether the protected equipment is faulty. The main start-up element of the protection. However, the above-mentioned method of detecting the current changes of each phase in real time is suitable for the situation that the current sensor on either side of the transformer does not have a disconnection fault. When the current sensor on one side of the transformer has a disconnection fault, the above-mentioned current sudden change amount starts to determine the failure. , the reliability of the judgment cannot be guaranteed.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a current sudden change starting method and transformer protection device for transformer protection, which are used to solve the problem that when there is a disconnection fault of a current sensor on one side of the transformer, the above current sudden change starting judgment fails, and the judgment cannot be guaranteed. reliability issues.

Based on the above purpose, the technical solution of a current sudden change starting method for transformer protection is as follows:

When the current sensor on one side of the transformer has a disconnection fault, the current sudden change of any phase on either side of the transformer is judged, and the zero sequence voltage, negative sequence voltage, zero sequence voltage sudden change and negative sequence on the corresponding side of the transformer are judged. Judging by the voltage mutation;

When there is a current mutation of a certain phase on the high-voltage side or medium-voltage side of the transformer that is greater than the set current mutation threshold, and when the zero-sequence voltage, negative-sequence voltage, zero-sequence voltage mutation or negative-sequence voltage mutation of the corresponding side of the transformer When the voltage is greater than the set voltage threshold, the current sudden change start element of the control transformer protection is activated;

When there is a current mutation of a certain phase on the low-voltage side of the transformer that is greater than the set current mutation threshold, and when the negative sequence voltage or negative sequence voltage mutation of the corresponding side of the transformer is greater than the set voltage threshold, control the protection of the transformer. The current jump start element is activated.

Based on the above purpose, the technical solution of the transformer protection device is as follows:

A processor is included for executing the instructions to implement the above-mentioned method for starting the current sudden change of the transformer protection.

The beneficial effects of the above two technical solutions are:

The current sudden change starting method and component of the present invention can judge the current sudden change of any phase on either side of the transformer when the current sensor on one side of the transformer has a disconnection fault, and combine the zero sequence voltage and zero sequence voltage sudden change It can be judged by any of the conditions of the voltage, the negative sequence voltage and the negative sequence voltage sudden change, so that even when the current sensor on one side of the transformer is disconnected, the current sudden change starting element can still start reliably.

The system on the low-voltage side of the transformer is usually a low-current grounding system. When the low-voltage side of the transformer is single-phase grounded, the system has zero-sequence voltage, but the transformer can continue to operate for a period of time. Therefore, the zero-sequence voltage and zero-sequence voltage mutation cannot be used on the low-voltage side of the transformer. The criterion can only be judged by the negative sequence voltage and the negative sequence voltage abrupt change; and when the high-voltage side or the medium-voltage side of the transformer is a high-current grounding system, the system does not continue to operate when there is a single-phase grounding fault, so zero can be used. Sequence voltage, zero-sequence voltage abrupt change, negative sequence voltage and negative sequence voltage abrupt change are judged. According to the actual operating conditions of the transformer, combined with the zero-sequence voltage of the corresponding side of the transformer, the zero-sequence voltage mutation, the negative sequence voltage and the negative sequence voltage mutation are comprehensively judged to prevent the current mutation starting element from starting incorrectly.

Further, the discriminant equation for judging the zero-sequence voltage on the corresponding side of the transformer is:

3U ₀ (t)>3U _0.SET

In the above formula, 3U ₀ (t) is the zero-sequence voltage amplitude of the corresponding side of the transformer at time t, and 3U _0.SET is the zero-sequence voltage value in the set voltage threshold. Specifically, the value range of the 3U _0.SET is _0.06UN to _0.15UN , where _UN is the rated voltage value of the transformer.

Further, the discriminant equation for judging the negative sequence voltage on the corresponding side of the transformer is:

U ₂ (t)>U _2.SET

In the above formula, U ₂ (t) is the negative-sequence voltage amplitude of the corresponding side of the transformer at time t, and U _2.SET is the negative-sequence voltage constant value in the set voltage threshold value. Specifically, the value range of U _2.SET is 0.06U _N to 0.10U _N , where U _N is the rated voltage value of the transformer.

Further, the discriminant equation for judging the zero-sequence voltage mutation on the corresponding side of the transformer is:

|3U ₀ (t)-3U ₀ (t-2T)|>Δ3U _0.SET

In the above formula, 3U ₀ (t) is the zero-sequence voltage amplitude of the corresponding side of the transformer at time t, 3U ₀ (t-2T) is the zero-sequence voltage amplitude of the corresponding side of the transformer at time t two cycles before 2T, Δ3U _{0. SET} is a fixed value of the zero-sequence voltage abrupt change in the set voltage threshold value. Specifically, the value range of the _{Δ3U 0.SET} is _0.015UN to _0.04UN , where UN is the rated voltage value of the transformer.

Further, the discriminant equation for judging the negative sequence voltage mutation on the corresponding side of the transformer is:

|U ₂ (t)-U ₂ (t-2T)|>ΔU _2.SET

In the above formula, U ₂ (t) is the negative sequence voltage amplitude of the corresponding side of the transformer at time t, U ₂ (t-2T) is the negative sequence voltage amplitude of the corresponding side of the transformer at time t two cycles before 2T, ΔU _{2. SET} is the negative sequence voltage abrupt change value in the set voltage threshold value. Specifically, the value range of the _{ΔU 2.SET} is 0.01 UN to 0.03 _UN , where _UN is the rated voltage value of the transformer.

Description of drawings

Fig. 1 is a schematic diagram of the main wiring mode of a 220kV transformer in the prior art;

2 is a schematic diagram of the startup logic of the current sudden change startup method in Embodiment 1 of the method of the present invention;

FIG. 3 is a schematic diagram of startup logic of the current sudden change startup method in Embodiment 2 of the method of the present invention.

Detailed ways

The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

Method Embodiment 1:

The method for starting the current sudden change of transformer protection of the present invention is mainly applied to the localized transformer protection device of the smart grid. Sequence voltage, zero-sequence voltage abrupt change or negative-sequence voltage sudden change is judged, and compared with the set voltage threshold to decide whether to control the current sudden change of the transformer protection to start the component to prevent the current sensor on one side of the transformer. When a disconnection fault occurs, the current sudden change will cause the starting element to refuse to move, so as to improve the reliability of the transformer protection device. The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

In the main wiring mode of the 220kV transformer shown in Figure 1, the transformer protection device collects the high-voltage side current TA1 and voltage TV1, medium-voltage side current TA2 and voltage TV2, and low-voltage side current TA3 and voltage TV3 of the transformer. Establish the starting criteria for the current sudden change of the high-voltage side, the medium-voltage side and the low-voltage side of the transformer. Among them, the transformer high-voltage side, medium-voltage side and low-voltage side current mutation startup criteria are respectively used as independent functional modules, which are placed in the transformer protection device, and each functional module is always used to realize the current mutation startup method of transformer protection. , its startup logic is shown in Figure 2, and the specific steps are as follows:

Determine whether the current sudden change of any phase on either side of the transformer is greater than the set current sudden change threshold; judge whether the phase current on the corresponding side of the transformer is greater than the set current threshold.

Specifically, the judgment process includes two criteria:

(1) The starting criterion of phase current sudden change (referred to as criterion 1), in this criterion, the discriminant equation satisfied by the current sudden change of any phase on the high voltage side, medium voltage side or low voltage side of the transformer (ie, the current sudden change judgment condition) for:

|I _Φ1 (t)-I _Φ1 (tT)|>1.25|I _Φ1 (tT)-I _Φ1 (t-2T)|+ΔI _SET

In the above formula, I _Φ1 (t) is the current amplitude of a certain phase on the high-voltage side, medium-voltage side or low-voltage side of the transformer at time t, and I _Φ1 (tT) is the phase current amplitude of the corresponding phase of the transformer at time t and one period before T. value, 1.25|I _Φ1 (tT)-I _Φ1 (t-2T)|+ΔI _SET is the threshold value of the set current sudden change, where I _Φ1 (t-2T) is the corresponding phase of the transformer before two cycles 2T at time t ΔI _SET is the constant value of the starting current of the sudden change, ΔI _SET takes max{0.2I _e , 0.1I _N }, where I _e is the secondary rated load current of the corresponding side of the transformer, and I _N is the corresponding side of the transformer The secondary rating of the current sensor.

(2) Phase current start-up criterion (referred to as criterion 2), in this criterion, the discriminant equation satisfied by the start-up of phase current on the corresponding side of the transformer is:

In the above formula, I _Φ1.MAX (t) is the maximum phase current amplitude in the three-phase current on the corresponding side of the transformer, and I _Φ1.SET is the fixed value of the phase current, taking 1.2I _e .

When the current mutation of a certain phase on one side of the transformer is greater than the set current mutation threshold, and when the phase current of the corresponding side of the transformer is greater than the corresponding current threshold, the current mutation starting element of the control transformer protection is activated, Send a current sudden change start message to the transformer protection device, and open the start power of the relevant outlet relay.

In order to prevent the failure of the above-mentioned judgment of the phase current when the CT (current sensor) of the transformer is disconnected, when the CT is disconnected, the starting criterion of the phase current is blocked (that is, the judgment of the phase current is blocked), and the zero-sequence voltage and negative voltage of the corresponding side of the transformer are automatically turned on. Sequence voltage, zero-sequence voltage mutation and negative-sequence voltage mutation (referred to as Criterion 3), in this criterion, the zero-sequence voltage, negative-sequence voltage, zero-sequence voltage mutation or negative-sequence voltage on the corresponding side of the transformer The discriminant equation for judging the mutation amount is:

The above formulas correspond to the zero-sequence voltage discrimination condition, the negative-sequence voltage discrimination condition, the _zero -sequence voltage abrupt change condition, and the negative-sequence voltage abrupt change condition. sequence voltage amplitude, U ₂ (t) is the negative-sequence voltage amplitude of the corresponding side of the transformer at time t, 3U ₀ (t-2T) is the zero-sequence voltage amplitude of the corresponding side of the transformer at time t two cycles before 2T, U ₂ (t-2T) is the negative sequence voltage amplitude of the corresponding side of the transformer at time t two cycles before 2T.

The set voltage thresholds include 3U _0.SET , U _2.SET , Δ3U _0.SET , ΔU _2.SET , of which 3U _0.SET is a zero-sequence voltage setting, and the value range of 3U _0.SET is 0.06U _N ~ _0.15UN , where _{UN is the rated voltage value of the transformer, preferably 0.1UN; U 2.SET is the} negative sequence voltage fixed value, and the value range of U _2.SET is 0.06 _UN ~ 0.10 _UN , It is preferable to take 0.08U _N ; Δ3U _0.SET is the zero-sequence voltage abrupt change value, and the value range of Δ3U _0.SET is 0.015U _N to 0.04U _N , preferably 0.02U _N ; ΔU _2.SET is the negative sequence voltage The mutation value is determined, and the value range of ΔU _2.SET is 0.01U _N to 0.03U _N , preferably 0.02U _N .

It should be noted that, when setting the voltage threshold value, since the negative-sequence voltage mutation is generally smaller than the zero-sequence voltage mutation, the negative-sequence voltage setting is smaller than the zero-sequence voltage setting; and in order to improve the protection The reliability of the above-mentioned zero-sequence voltage mutation and the negative-sequence voltage mutation are preferably set to be relatively small.

Based on the above voltage threshold settings, when there is a current mutation of a certain phase on the high-voltage side or medium-voltage side of the transformer that is greater than the corresponding current mutation threshold, and when the zero-sequence voltage, negative-sequence voltage, and zero-sequence voltage of the corresponding side of the transformer When the sudden change or the negative sequence voltage sudden change is greater than the corresponding voltage threshold, the current sudden change start element of the control transformer protection is activated.

When the current mutation of a certain phase on the low-voltage side of the transformer is greater than the corresponding current mutation threshold, and when the negative sequence voltage or negative sequence voltage mutation of the corresponding side of the transformer is greater than the corresponding voltage threshold, the current mutation of the transformer protection is controlled. The quantity start element starts.

After the transformer current sudden change starting element is started, it will return with a fixed delay, and the return time of the whole group is 7s.

The current sudden change starting method and component of the present invention can judge the current sudden change of any phase on either side of the transformer when the current sensor on one side of the transformer has a disconnection fault, and combine the zero sequence voltage and zero sequence voltage sudden change It can be judged by any of the conditions of the voltage, the negative sequence voltage and the negative sequence voltage sudden change, so that even when the current sensor on one side of the transformer is disconnected, it can still ensure the reliable start of the current sudden change starting element.

In this embodiment, the above-mentioned criterion 1 and criterion 2 can be judged at the same time, and the criterion 1 and criterion 3 can be judged at the same time when the CT of the transformer is disconnected. The result of 1 determines whether to carry out the judgment of criterion 2 or 3. When the discriminant equation of criterion 1 is not satisfied, it is directly judged that the current mutation start-up element does not start, and the judgment of criterion 2 and criterion 3 is no longer performed. In order to save the amount of calculation and improve the calculation efficiency.

Method embodiment two:

In order to determine whether the current sudden change starting element is started, the current sudden change starting method of this embodiment is the same as the method embodiment 1, in that it includes three criteria, namely, criterion one, criterion two and criterion three. The logic is shown in Figure 3, in which the first and third criteria are the same as those in the method embodiment 1. The difference is that the zero-sequence current and negative-sequence current start-up criteria are added to the second criterion. Therefore, the transformer corresponds to The discriminant equation satisfied by side-phase current or zero-sequence current or negative-sequence current startup is:

The above formulas correspond to the phase current judgment condition, the zero sequence current judgment condition and the negative sequence current judgment condition in turn. In the above formula, I _Φ1.MAX (t) is the maximum phase current amplitude in the three-phase current on the corresponding side of the transformer, 3I ₀ (t) is the zero-sequence current amplitude of the corresponding side of the transformer, I ₂ (t) is the negative-sequence current amplitude of the corresponding side of the transformer, and the set current thresholds include I _Φ1.SET , 3I _0.SET , I _{2 .SET , where I Φ1.SET is} the fixed value of phase current, take 1.2I _e ; 3I _0.SET is the fixed value of zero sequence current, take 0.1I _N ; I _2.SET is the fixed value of negative sequence current, take 0.2I _N .

When the current mutation of a phase on one side of the transformer is greater than the set current mutation threshold, and when the phase current or zero-sequence current or negative-sequence current of the corresponding side of the transformer is greater than the corresponding current threshold, control the transformer protection The current sudden change starting element starts, and the current sudden change starting message is sent to the transformer protection device, and the starting power of the relevant outlet relay is opened.

In order to prevent the above-mentioned judgments of phase current, zero sequence current and negative sequence current from being invalid when the CT (current sensor) of the transformer is disconnected, the starting criteria for blocking phase current, zero sequence current and negative sequence current when CT is disconnected (that is, blocking phase current and negative sequence current) current, zero-sequence current and negative-sequence current), and automatically input the zero-sequence voltage, negative-sequence voltage, zero-sequence voltage abrupt change and negative-sequence voltage abrupt change criterion (referred to as criterion three) on the corresponding side of the transformer (referred to as criterion three). The third criterion in the example is the same as the third criterion recorded in the method embodiment 1, and is not repeated in this embodiment.

Examples of transformer protection devices:

This embodiment provides a transformer protection device, including a processor for executing instructions to implement the following steps:

When the current sensor on one side of the transformer has a disconnection fault, the current sudden change of any phase on either side of the transformer is judged, and the zero sequence voltage, negative sequence voltage, zero sequence voltage sudden change and negative sequence on the corresponding side of the transformer are judged. The voltage mutation amount is judged.

When there is a current mutation of a certain phase on the high-voltage side or medium-voltage side of the transformer that is greater than the set current mutation threshold, and when the zero-sequence voltage, negative-sequence voltage, zero-sequence voltage mutation or negative-sequence voltage mutation of the corresponding side of the transformer When the amount is greater than the set voltage threshold, the current sudden change start element of the control transformer protection is activated.

When there is a current mutation of a certain phase on the low-voltage side of the transformer that is greater than the set current mutation threshold, and when the negative sequence voltage or negative sequence voltage mutation of the corresponding side of the transformer is greater than the set voltage threshold, control the protection of the transformer. The current jump start element is activated.

Since the description of the above-mentioned methods in Method Embodiments 1 and 2 is sufficiently clear and complete, it will not be described in detail.

Claims (10)

1. A method for starting a sudden current change for transformer protection is characterized by comprising the following steps:

when a current sensor on one side of the transformer has a line break fault, judging the current break variable of any phase on any side of the transformer, and judging the zero sequence voltage, the negative sequence voltage, the zero sequence voltage break variable and the negative sequence voltage break variable on the corresponding side of the transformer;

when the current break variable of a certain phase at the high-voltage side or the medium-voltage side of the transformer is larger than a set current break variable threshold value, and when the zero sequence voltage, the negative sequence voltage, the zero sequence voltage break variable or the negative sequence voltage break variable of the corresponding side of the transformer is larger than the set voltage threshold value, controlling a current break variable starting element protected by the transformer to start;

when the current mutation amount of a certain phase at the low-voltage side of the transformer is larger than a set current mutation amount threshold value and the negative sequence voltage or the negative sequence voltage mutation amount of the corresponding side of the transformer is larger than a set voltage threshold value, a current mutation amount starting element for protecting the transformer is controlled to start.

2. The method for starting the current mutation quantity of the transformer protection according to claim 1, wherein the discriminant equation for judging the zero sequence voltage of the corresponding side of the transformer is as follows:

3U₀(t)>3U_0.SET

3U in the above formula₀(t) is zero sequence voltage amplitude value of corresponding side of the transformer at time t, 3U_0.SETAnd determining a value for the zero sequence voltage in the set voltage threshold value.

3. The transformer protected inrush current amount starting method according to claim 2, wherein the 3U is used for starting a transformer_0.SETHas a value range of 0.06U_N～0.15U_NWherein U is_NIs the rated voltage value of the transformer.

4. The method for starting the sudden change of current for transformer protection according to claim 1, wherein the discriminant equation for determining the negative sequence voltage of the corresponding side of the transformer is as follows:

U₂(t)>U_2.SET

in the above formula U₂(t) is the negative sequence voltage amplitude at time t of the corresponding side of the transformer, U_2.SETAnd setting the negative sequence voltage in the set voltage threshold value.

5. The transformer protected current inrush current method of claim 2, wherein the U is a U_2.SETHas a value range of 0.06U_N～0.10U_NWherein U is_NIs the rated voltage value of the transformer.

6. The method for starting the current mutation quantity of the transformer protection according to claim 1, wherein the discriminant equation for judging the zero sequence voltage mutation quantity of the corresponding side of the transformer is as follows:

|3U₀(t)-3U₀(t-2T)|>Δ3U_0.SET

3U in the above formula₀(t) is zero sequence voltage amplitude value of corresponding side of the transformer at time t, 3U₀(T-2T) is zero sequence voltage amplitude of the corresponding side of the transformer before 2T in two periods at time T, delta3U_0.SETAnd determining a value for the zero sequence voltage mutation in the set voltage threshold value.

7. The transformer protected current inrush current method of claim 2, wherein the Δ 3U is a delta 3U_0.SETIs in the range of 0.015U_N～0.04U_NWherein U is_NIs the rated voltage value of the transformer.

8. The method for starting the current mutation quantity of the transformer protection according to claim 1, wherein the discriminant equation for judging the negative sequence voltage mutation quantity of the corresponding side of the transformer is as follows:

|U₂(t)-U₂(t-2T)|>ΔU_2.SET

in the above formula U₂(t) is the negative sequence voltage amplitude at time t of the corresponding side of the transformer, U₂(T-2T) is the negative sequence voltage amplitude of the corresponding side of the transformer two periods before 2T at time T, delta U_2.SETAnd determining the quantity of the negative sequence voltage mutation in the set voltage threshold value.

9. The transformer protected current inrush current method of claim 8, wherein the au is_2.SETHas a value range of 0.01U_N～0.03U_NWherein U is_NIs the rated voltage value of the transformer.

10. A transformer protection device comprising a processor for executing instructions to implement a current break variable start-up method of transformer protection according to any one of claims 1-9.

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