CN105186452A - Implementation method for phase-shifting transformer differential protection - Google Patents

Abstract

The invention discloses an implementation method for phase-shifting transformer differential protection. The implementation method is characterized by comprising the following steps specifically: step SS1, collecting winding current of each side of a transformer in real time; step SS2, converting each winding current in the low voltage side into the high voltage side, and shifting to a step SS3; step SS3, calculating differential current according to the converted current; and step SS4, judging whether the differential current is higher than an action threshold or not, if so, cutting off the transformer by the differential protection action. The implementation method for the phase-shifting transformer differential protection is suitable for common electric transformers as well as phase-shifting transformers with multiple windings, random connection groups and random phase differences; and the implementation method has extremely high universality, and solves the problem that the existing phase-shifting transformers (including rectifier transformers) cannot realize the differential protection caused by difficulty in calculating the differential current.

Description

A kind of phase shifting transformer differential protection implementation method

Technical field

The present invention relates to a kind of implementation method of phase shifting transformer differential protection, belong to electrical engineering technical field of relay protection.

Background technology

At industrial circles such as aluminium electroloysis, alkali electrolysis, salt electrolysis, chemical industry, use rectification phase shifting transformer in a large number.Phase shifting transformer has following three functions: 1. realize the phase deviation of first and second side line voltage with harmonic carcellation; 2. conversion obtains the secondary side voltage of needs; 3. the electrical isolation between rectifier and electrical network is realized.

The special function of phase shifting transformer determines its special electrical structure, and different from common transformer, phase shifting transformer secondary winding has many groups usually.According to the difference of Phase shift winding, phase shifting transformer can be divided into high-pressure side phase shift and low-pressure side phase shift.When for high-pressure side phase shift, high pressure winding adopts the extension triangle mode of connection or the figure of eight mode of connection usually, as shown in Figure 1.When for low-pressure side phase shift, low pressure winding adopts the extension triangle mode of connection usually, as shown in Figure 2.

Phase shifting transformer is multi winding transformer, and the phase difference between winding is different, and such as 36 pulse wave rectifier phase shift low pressure side phase shift phase places are respectively-20 ,-10,0,10,20,30.Transformer differential protection needs the phase place each side joint being entered to electric current to compensate, indifference stream during to guarantee that transformer normally runs, and has difference stream during internal fault.Conventional power transformer is generally the whole hour number mode of connection, and as Y0, △-11 wiring, Y, △-1 wiring, only needs Y-△ phase transition, i.e. IA '=IA-IB during differential current computing, or IA '=IA-IC, B, C phase by that analogy.And phase difference is not whole hour number (30 °) between each winding of phase shifting transformer, thus cannot realize current phase by simple addition and subtraction and compensate, differential current computing more complicated, must redesign differential current computing method.

At present, consider for aspects such as construction condition, cost of investment and technical difficulty, phase shifting transformer generally only configures quick-break overcurrent and protection, does not install differential protection.Because phase shifting transformer low-pressure side winding is many, inner no-load voltage ratio is changeable, and cause its impedance not easily to calculate, therefore set-point is adjusted and made troubles.In addition, quick-break overcurrent can not reflect the fault such as high resistance ground in inside transformer turn-to-turn short circuit, district, and the sensitivity therefore protected is lower.

Summary of the invention

The object of the invention is the defect overcoming prior art existence, improve sensitivity and the reliability of phase shifting transformer protection, the present invention proposes a kind of phase shifting transformer differential protection implementation method, goes for the transformer of any wiring group, random phase difference.

The present invention adopts following technical scheme: a kind of phase shifting transformer differential protection implementation method, is characterized in that, specifically comprise the steps:

Step SS1 Real-time Collection transformer each side winding current;

Each for low-pressure side winding current is converted high-pressure side by step SS2, proceeds to step SS3;

Step SS3 is according to the Current calculation difference stream after conversion;

Step SS4 differentiates whether differential current is greater than action threshold, if differential current is greater than threshold, and differential protection action excision transformer.

Preferably, each side winding current described in described step SS1 comprises high pressure winding current i _ha, i _hb, i _hc, low pressure 1 ~ n winding current i _lja, i _ljb, i _ljc, wherein j=1,2 Λ n.

Preferably, described step SS2 specifically comprises the steps: to set high-pressure side winding rated voltage as U _hN, high-pressure side winding CT no-load voltage ratio is CT _h, it is U that low-pressure side volume winding determines voltage _lN, low-pressure side winding CT no-load voltage ratio is CT _l, low-pressure side winding and high-pressure side winding phases difference are according to the fundamental characteristics of transformer, have

Wherein $\mathrm{\ϵ}=\frac{U_{lN}*{\mathrm{CT}}_l}{U_{hN}*{\mathrm{CT}}_h};$

Can by two orthogonal phasor representations based on any one phasor, if:

${\stackrel{\·}{I}}_{hA}=\stackrel{\·}{k_1{I}_{lA}}+\stackrel{\·}{k_2{I}_{lB}}---\left(2\right)$

In formula for high-pressure side winding A phase current phasor, for low-pressure side winding A, B phase current phasor; Because three-phase current is symmetrical, therefore have:

Association type (1) ~ (3), can solve:

Formula (2) gives the equivalent relation of high-pressure side winding and low-pressure side winding current, that is to say the computational methods of low-pressure side winding current being converted to high-pressure side winding current, that is:

${{\stackrel{\·}{I}}^{\′}}_{lA}=\stackrel{\·}{k_1{I}_{lA}}+\stackrel{\·}{k_2{I}_{lB}}---\left(5\right)$

i′ _lja＝k _j1i _lja+k _j2i _ljb

i′ _ljb＝k _j1i _ljb+k _j2i _ljc

i′ _ljc＝k _j1i _ljc+k _j2i _lja(6)

Wherein, formula (6) is high-pressure side winding current and low-pressure side winding current relational expression.

Preferably, described step SS3 specifically comprises the steps: that formula (6) is equally applicable to the conversion of sampled value, and after conversion, both phase places unanimously, and then directly carry out differential current computing, that is:

i _da＝i _ha+i′ _la

i _db＝i _hb+i′ _lc(7)

i _dc＝i _hc+i′ _la

Formula (7) is phase shift angle the differential current computing formula of two winding transformer, being generalized to low-pressure side has n winding, and the arbitrary phase shifting transformer of each winding phase shift angle, then differential current computing formula is:

$i_{da}=i_{ha}+\underset{j=1}{\overset{n}{\Σ}}{i}_{lja}^{\′}$

$i_{db}=i_{hb}+\underset{j=1}{\overset{n}{\Σ}}{i}_{ljb}^{\′}---\left(8\right)$

$i_{dc}=i_{hc}+\underset{j=1}{\overset{n}{\Σ}}{i}_{ljc}^{\′}$

Wherein, i _ha, i _hb, i _hcfor high pressure winding current, i _lja, i _ljb, i _ljcfor low pressure 1 ~ n winding

Electric current, j=1,2 Λ n.

The beneficial effect that the present invention reaches: the present invention is not only applicable to conventional power transformer; and be applicable to the phase shifting transformer of Multiple coil, arbitrarily wiring group, random phase difference; there is extremely strong versatility, solve current phase shifting transformer (comprising rectifier transformer) cannot realize differential protection present situation because difference stream is difficult to calculate.

Accompanying drawing explanation

When Fig. 1 is high-pressure side phase shift, high pressure winding adopts the schematic diagram of the extension triangle mode of connection or the figure of eight mode of connection.

When Fig. 2 is low-pressure side phase shift, low pressure winding adopts the extension triangle mode of connection usually.

Fig. 3 is the flow chart of the implementation method of a kind of phase shifting transformer differential protection of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.Following examples only for technical scheme of the present invention is clearly described, and can not limit the scope of the invention with this.

Fig. 3 is the flow chart of the implementation method of a kind of phase shifting transformer differential protection of the present invention, and the present invention adopts following technical scheme: a kind of phase shifting transformer differential protection implementation method, is characterized in that, specifically comprise the steps:

Step SS1 Real-time Collection transformer each side winding current; Each side winding current described in described step SS1 comprises high pressure winding current i _ha, i _hb, i _hc, low pressure 1 ~ n winding current i _lja, i _ljb, i _ljc, wherein j=1,2 Λ n;

Each for low-pressure side winding current is converted high-pressure side by step SS2, proceeds to step SS3; Described step SS2 specifically comprises the steps: to set high-pressure side winding rated voltage as U _hN, high-pressure side winding CT no-load voltage ratio is CT _h, it is U that low-pressure side volume winding determines voltage _lN, low-pressure side winding CT no-load voltage ratio is CT _l, low-pressure side winding and high-pressure side winding phases difference are according to the fundamental characteristics of transformer, have

Wherein $\mathrm{\ϵ}=\frac{U_{lN}*{\mathrm{CT}}_l}{U_{hN}*{\mathrm{CT}}_h};$

Can by two orthogonal phasor representations based on any one phasor, if:

${\stackrel{\·}{I}}_{hA}=\stackrel{\·}{k_1{I}_{lA}}+\stackrel{\·}{k_2{I}_{lB}}---\left(2\right)$

In formula for high-pressure side winding A phase current phasor, for low-pressure side winding A, B phase current phasor; Because three-phase current is symmetrical, therefore have:

Association type (1) ~ (3), can solve:

Formula (2) gives the equivalent relation of high-pressure side winding and low-pressure side winding current, that is to say the computational methods of low-pressure side winding current being converted to high-pressure side winding current, that is:

${{\stackrel{\·}{I}}^{\′}}_{lA}=\stackrel{\·}{k_1{I}_{lA}}+\stackrel{\·}{k_2{I}_{lB}}---\left(5\right)$

i′ _lja＝k _j1i _lja+k _j2i _ljb

i′ _ljb＝k _j1i _ljb+k _j2i _ljc

i′ _ljc＝k _j1i _ljc+k _j2i _lja(6)

Wherein, formula (6) is high-pressure side winding current and low-pressure side winding current relational expression.

Step SS3 is according to the Current calculation difference stream after conversion; Described step SS3 specifically comprises the steps: that formula (6) is equally applicable to the conversion of sampled value, and after conversion, both phase places unanimously, and then directly carry out differential current computing, that is:

i _da＝i _ha+i′ _la

i _db＝i _hb+i′ _lc(7)

i _dc＝i _hc+i′ _la

Formula (7) is phase shift angle the differential current computing formula of two winding transformer, being generalized to low-pressure side has n winding, and the arbitrary phase shifting transformer of each winding phase shift angle, then differential current computing formula is:

$i_{da}=i_{ha}+\underset{j=1}{\overset{n}{\Σ}}{i}_{lja}^{\′}$

$i_{db}=i_{hb}+\underset{j=1}{\overset{n}{\Σ}}{i}_{ljb}^{\′}---\left(8\right)$

$i_{dc}=i_{hc}+\underset{j=1}{\overset{n}{\Σ}}{i}_{ljc}^{\′}$

Wherein, i _ha, i _hb, i _hcfor high pressure winding current, i _lja, i _ljb, i _ljcfor low pressure 1 ~ n winding

Electric current, j=1,2 Λ n.

Step SS4 differentiates whether differential current is greater than action threshold, if differential current is greater than threshold, and differential protection action excision transformer.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the prerequisite not departing from the technology of the present invention principle; can also make some improvement and distortion, these improve and distortion also should be considered as protection scope of the present invention.

Claims (4)

1. a phase shifting transformer differential protection implementation method, is characterized in that, specifically comprises the steps:

Step SS1 Real-time Collection transformer each side winding current;

Each for low-pressure side winding current is converted high-pressure side by step SS2, proceeds to step SS3;

Step SS3 is according to the Current calculation difference stream after conversion;

Step SS4 differentiates whether differential current is greater than action threshold, if differential current is greater than threshold, and differential protection action excision transformer.

2. a kind of phase shifting transformer differential protection implementation method according to claim 1, is characterized in that, each side winding current described in described step SS1 comprises high pressure winding current i _ha, i _hb, i _hc, low pressure 1 ~ n winding current i _lja, i _ljb, i _ljc, wherein j=1,2 Λ n.

3. a kind of phase shifting transformer differential protection implementation method according to claim 2, is characterized in that, described step SS2 specifically comprises the steps: to set high-pressure side winding rated voltage as U _hN, high-pressure side winding CT no-load voltage ratio is CT _h, it is U that low-pressure side volume winding determines voltage _lN, low-pressure side winding CT no-load voltage ratio is CT _l, low-pressure side winding and high-pressure side winding phases difference are according to the fundamental characteristics of transformer, have

Wherein $\mathrm{\ϵ}=\frac{U_{lN}*{\mathrm{CT}}_l}{U_{hN}*{\mathrm{CT}}_h};$

Can by two orthogonal phasor representations based on any one phasor, if:

${\stackrel{\·}{I}}_{hA}=\stackrel{\·}{k_1{I}_{lA}}+\stackrel{\·}{k_2{I}_{lB}}---\left(2\right)$

In formula for high-pressure side winding A phase current phasor, for low-pressure side winding A, B phase current phasor; Because three-phase current is symmetrical, therefore have:

Association type (1) ~ (3), can solve:

Formula (2) gives the equivalent relation of high-pressure side winding and low-pressure side winding current, that is to say the computational methods of low-pressure side winding current being converted to high-pressure side winding current, that is:

${{\stackrel{\·}{I}}^{\′}}_{lA}=\stackrel{\·}{k_1{I}_{lA}}+\stackrel{\·}{k_2{I}_{lB}}---\left(5\right)$

i′ _lja＝k _j1i _lja+k _j2i _ljb

i′ _ljb＝k _j1i _ljb+k _j2i _ljc

i′ _ljc＝k _j1i _ljc+k _j2i _lja(6)

Wherein, formula (6) is high-pressure side winding current and low-pressure side winding current relational expression.

4. a kind of phase shifting transformer differential protection implementation method according to claim 3; it is characterized in that, described step SS3 specifically comprises the steps: that formula (6) is equally applicable to the conversion of sampled value, and after conversion, both phase places are consistent; and then directly carry out differential current computing, that is:

i _da＝i _ha+i′ _la

i _db＝i _hb+i′ _lc(7)

i _dc＝i _hc+i′ _la

Formula (7) is phase shift angle the differential current computing formula of two winding transformer, being generalized to low-pressure side has n winding, and the arbitrary phase shifting transformer of each winding phase shift angle, then differential current computing formula is:

$i_{da}=i_{ha}+\underset{j=1}{\overset{n}{\Σ}}{i}_{lja}^{\′}$

$i_{db}=i_{hb}+\underset{j=1}{\overset{n}{\Σ}}{i}_{ljb}^{\′}---\left(8\right)$

$i_{dc}=i_{hc}+\underset{j=1}{\overset{n}{\Σ}}{i}_{ljc}^{\′}$

Wherein, i _ha, i _hb, i _hcfor high pressure winding current, i _lja, i _ljb, i _ljcfor low pressure 1 ~ n winding current, j=1,2 Λ n.