CN103779835A - Transformer winding turn-to-turn short circuit relay protection method based on iron loss reactive power characteristic - Google Patents

Abstract

The invention discloses a transformer winding turn-to-turn short circuit relay protection method based on the iron loss reactive power characteristic. Firstly, the three-phase voltage and the three-phase current of all sampling time on the high-voltage side of a transformer are measured, the positive sequence voltage and the positive sequence current of all the t sampling time on the d coordinate axis and the q coordinate axis of the high-voltage side of the transformer are calculated and the iron loss reactive power of the transformer is calculated. Afterwards, the obtained iron loss reactive power of the transformer and the setting reactive power form relay protection criteria. According to the transformer winding turn-to-turn short circuit relay protection method, the characteristic that energy consumed by an iron core of the transformer when the transformer winding turn-to-turn short circuit fault occurs is mainly the active power and energy consumed by the iron core of the transformer is mainly the reactive power when magnetizing rush currents are generated by no-load closing of the transformer is used for detecting a transformer winding turn-to-turn short circuit fault, and the acting performance is prevented from being affected by exciting currents, transition resistance and load currents and is accurate and reliable. The malfunction transformer can be effectively prevented from operating all the time so as to prevent a transformer winding from deforming. Safety of the transformer equipment is ensured.

Description

Based on iron loss reactive power characteristic Transformer Winding turn-to-turn short circuit relay protecting method

Technical field

The present invention relates to Relay Protection Technology in Power System field, specifically relate to a kind of based on iron loss reactive power characteristic Transformer Winding turn-to-turn short circuit relay protecting method.

Background technology

The 220kV transformer of electric power system extensive use adopts three-phase three-winding transformer conventionally.In order to guarantee that phase electromotive force is close to sine wave, for triple-frequency harmonics provides path, three-phase three-winding transformer must have one group of winding to adopt delta connection, and therefore its mode of connection is △/Y/Y wiring.

Current differential protection is the main protection of transformer, and difference between current momentum is zero when making normally to move, two groups of Y side electric currents of transformer need be converted to △ side or △ side electric current is converted to two groups of Y sides, to eliminate unsymmetrical current.In order to eliminate unsymmetrical current; mainly adopt at present the current compensation mode that two groups of Y side electric currents is converted to the current compensation mode of △ side and △ side electric current is converted to two groups of Y sides; but the difference between current momentum after this two kinds of mapping modes conversion all can not correct response transformer magnetizing current impact; cause as the current differential protection Reliability of Microprocessor of transformer main protection influencedly, also make to utilize second harmonic to differentiate the method reliability of magnetizing inrush current and short trouble on the low side.

When transformer generation winding interturn short-circuit fault; fault current is little; fault signature is not obvious; differential current is usually less than stalling current; current differential protection criterion cannot meet, and protection cannot the each side circuit breaker of correct operation tripping transformer, causes failure transformer to move always; easily cause deformation of transformer winding, serious threat power equipment safety.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, provide that a kind of performance is not subject to that exciting current, transition resistance and load current affect based on iron loss reactive power characteristic Transformer Winding turn-to-turn short circuit relay protecting method.

Technical scheme of the present invention is as follows:

A kind of based on iron loss reactive power characteristic Transformer Winding turn-to-turn short circuit relay protecting method, step is as follows:

1) the three-phase voltage u of the each t sampling instant of protector measuring high voltage side of transformer _a(t), u _b(t), u _cand three-phase current i (t) _a(t), i _b(t), i _c(t);

2) protective device calculating transformer high-pressure side each t sampling instant positive sequence voltage u in dq reference axis _d(t), u _q(t):

$u_d\left(t\right)=\sqrt{\frac{2}{3}}(u_a\left(t\right)\cos \left(\mathrm{\ωt}\right)+u_b\left(t\right)\cos (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+u_c\left(t\right)\cos (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π}))$

$u_q\left(t\right)=-\sqrt{\frac{2}{3}}(u_a\left(t\right)\sin \left(\mathrm{\ωt}\right)+u_b\left(t\right)\sin (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+u_c\left(t\right)\sin (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})),$

Wherein, ω is electric power system angular frequency; T is the sampling time;

3) protective device calculating transformer high-pressure side each t sampling instant forward-order current i in dq reference axis _d(t), i _q(t):

$i_d\left(t\right)=\sqrt{\frac{2}{3}}(i_a\left(t\right)\cos \left(\mathrm{\ωt}\right)+i_b\left(t\right)\cos (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+i_c\left(t\right)\cos (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π}))$

$i_q\left(t\right)=-\sqrt{\frac{2}{3}}(i_a\left(t\right)\sin \left(\mathrm{\ωt}\right)+i_b\left(t\right)\sin (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+i_c\left(t\right)\sin (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})),$

Wherein, ω is electric power system angular frequency; T is the sampling time;

4) protective device calculating transformer iron loss reactive power

5) protective device judges whether transformer iron loss reactive power Q is less than

if be less than, protective device judges transformer generation winding interturn short-circuit fault, sends action trip signal, the each side circuit breaker of tripping transformer; Wherein, k is tuning coefficient, value in (1.53) scope.

Beneficial effect of the present invention is as follows:

The inventive method is three-phase voltage and the three-phase current of the each sampling instant in measuring transformer high-pressure side first; positive sequence voltage and the forward-order current of the each t sampling instant in dq reference axis of calculating transformer high-pressure side; calculating transformer iron loss reactive power, then utilizes the transformer iron loss reactive power calculating and the reactive power of adjusting to form relaying protection criterion.When the inventive method is utilized Transformer Winding shorted-turn fault, transformer core consumed energy is mainly active power; transformer during no-load closing produces when magnetizing inrush current transformer core consumed energy and is mainly this characteristic of reactive power and carries out the detection of Transformer Winding shorted-turn fault; Perfomance of protective relaying is not subject to the impact of exciting current, transition resistance and load current; performance is correctly reliable; can effectively prevent that failure transformer from moving always causes deformation of transformer winding, guarantees transformer equipment safety.

Accompanying drawing explanation

Fig. 1 is △/Y/Y wiring transformer schematic diagram of implementing the inventive method.

Embodiment

Below in conjunction with drawings and Examples, the present invention is described in further detail.

△/Y/Y wiring transformer schematic diagram of enforcement the inventive method as shown in Figure 1.In the present embodiment, the three-phase voltage u of the each t sampling instant of protector measuring high voltage side of transformer _a(t), u _b(t), u _cand three-phase current i (t) _a(t), i _b(t), i _c(t).

Protective device calculating transformer high-pressure side is each t sampling instant positive sequence voltage u in dq reference axis _d(t), u _q(t):

$u_d\left(t\right)=\sqrt{\frac{2}{3}}(u_a\left(t\right)\cos \left(\mathrm{\ωt}\right)+u_b\left(t\right)\cos (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+u_c\left(t\right)\cos (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π}))$

$u_q\left(t\right)=-\sqrt{\frac{2}{3}}(u_a\left(t\right)\sin \left(\mathrm{\ωt}\right)+u_b\left(t\right)\sin (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+u_c\left(t\right)\sin (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})),$

Wherein, ω is electric power system angular frequency; T is the sampling time;

3) protective device calculating transformer high-pressure side each t sampling instant forward-order current i in dq reference axis _d(t), i _q(t):

$i_d\left(t\right)=\sqrt{\frac{2}{3}}(i_a\left(t\right)\cos \left(\mathrm{\ωt}\right)+i_b\left(t\right)\cos (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+i_c\left(t\right)\cos (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π}))$

$i_q\left(t\right)=-\sqrt{\frac{2}{3}}(i_a\left(t\right)\sin \left(\mathrm{\ωt}\right)+i_b\left(t\right)\sin (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+i_c\left(t\right)\sin (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})),$

Wherein, ω is electric power system angular frequency; T is the sampling time;

4) protective device calculating transformer iron loss reactive power Q=-u _d(t) i _q(t)+u _q(t) i _d(t);

5) protective device judges whether transformer iron loss reactive power Q is less than

if be less than, protective device judges transformer generation winding interturn short-circuit fault, sends action trip signal, the each side circuit breaker of tripping transformer; Wherein, k is tuning coefficient, value in (1.53) scope.

The inventive method is three-phase voltage and the three-phase current of the each sampling instant in measuring transformer high-pressure side first; positive sequence voltage and the forward-order current of the each t sampling instant in dq reference axis of calculating transformer high-pressure side; calculating transformer iron loss reactive power, then utilizes the transformer iron loss reactive power calculating and the reactive power of adjusting to form relaying protection criterion.

When the inventive method is utilized Transformer Winding shorted-turn fault, transformer core consumed energy is mainly active power; transformer during no-load closing produces when magnetizing inrush current transformer core consumed energy and is mainly this characteristic of reactive power and carries out the detection of Transformer Winding shorted-turn fault; Perfomance of protective relaying is not subject to the impact of exciting current, transition resistance and load current; performance is correctly reliable; can effectively prevent that failure transformer from moving always causes deformation of transformer winding, guarantees transformer equipment safety.

Above-described embodiment is only for the present invention is described, and not as limitation of the invention.As long as according to technical spirit of the present invention, to above-described embodiment change, modification etc. all will drop in the scope of claim of the present invention.

Claims (1)

1. based on an iron loss reactive power characteristic Transformer Winding turn-to-turn short circuit relay protecting method, it is characterized in that, step is as follows:

1) the three-phase voltage u of the each t sampling instant of protector measuring high voltage side of transformer _a(t), u _b(t), u _cand three-phase current i (t) _a(t), i _b(t), i _c(t);

2) protective device calculating transformer high-pressure side each t sampling instant positive sequence voltage u in dq reference axis _d(t), u _q(t):

$u_d\left(t\right)=\sqrt{\frac{2}{3}}(u_a\left(t\right)\cos \left(\mathrm{\ωt}\right)+u_b\left(t\right)\cos (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+u_c\left(t\right)\cos (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π}))$

$u_q\left(t\right)=-\sqrt{\frac{2}{3}}(u_a\left(t\right)\sin \left(\mathrm{\ωt}\right)+u_b\left(t\right)\sin (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+u_c\left(t\right)\sin (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})),$

Wherein, ω is electric power system angular frequency; T is the sampling time;

3) protective device calculating transformer high-pressure side each t sampling instant forward-order current id (t), iq (t) in dq reference axis:

$i_d\left(t\right)=\sqrt{\frac{2}{3}}(i_a\left(t\right)\cos \left(\mathrm{\ωt}\right)+i_b\left(t\right)\cos (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+i_c\left(t\right)\cos (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π}))$

$i_q\left(t\right)=-\sqrt{\frac{2}{3}}(i_a\left(t\right)\sin \left(\mathrm{\ωt}\right)+i_b\left(t\right)\sin (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})+i_c\left(t\right)\sin (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})),$

Wherein, ω is electric power system angular frequency; T is the sampling time;

4) protective device calculating transformer iron loss reactive power Q=-u _d(t) i _q(t)+u _q(t) i _d(t);

5) protective device judges whether transformer iron loss reactive power Q is less than

if be less than, protective device judges transformer generation winding interturn short-circuit fault, sends action trip signal, the each side circuit breaker of tripping transformer; Wherein, k is tuning coefficient, value in (1.53) scope.