CN104134976A - Method for recognizing fault in power transmission line distance protection - Google Patents

Abstract

The invention provides a method for recognizing a fault in a power transmission line distance protection. The method comprises the following steps that the three-phase voltage and the three-phase current at the position where the protection is installed; a positive sequence voltage, a positive sequence current, a negative sequence current and a zero sequence current with the phi phase as the reference are determined; the current asymmetry degree at the position where the protection is installed is determined; the included angle between the positive sequence voltage and the positive sequence current is determined; fault recognition is carried out according to a current asymmetry degree plane. According to method for recognizing the fault in the power transmission line distance protection, fault recognition in the distance protection is achieved through comprehensive use of the current asymmetry degree and the U1cos phi1 characteristic, and action performance of an existing power transmission line distance protection is improved when a fault happens during oscillation and overload happens.

Description

Fault recognition method in a kind of transmission line distance protecting

Technical field

The present invention relates to the method in a kind of distance protection field, specifically relate to fault recognition method in a kind of transmission line distance protecting.

Background technology

Distance protection is divided into three sections; its middle distance I, II section; after fault opening 150ms; enter out-of-step blocking; at idle interval; need to carry out fault open again; affect distance protection responsiveness, for distance protection III section, when the increase of transmission line transmission capacity and the transfer of line fault afterload can cause circuit overload; load impedance enters distance protection active region; can cause distance protection misoperation, and then cause load further to shift, cause cascading failure; cause accident expanded range, when serious, can cause large-area power-cuts.

In prior art, take out-of-step blocking fault again open condition be to utilize separately m (open unbalanced fault) and Ucos φ (opening symmetric fault), for unbalanced fault, when single phase ground fault transition resistance is larger, can not open, for symmetric fault, open hour are longer, problem for distance protection possibility misoperation under overload, the measure of taking is at present mainly that the load limit line of adjusting on impedance plane escapes load, and this method can be sacrificed the sensitivity of distance protection, along with load constantly increases, the active region of distance protection can significantly reduce, for single phase ground fault, because transition resistance excursion is larger, when transition resistance is larger, impact due to load limit line, distance protection tripping is done, the tolerance transition resistance ability of distance protection is significantly weakened.

Therefore, need to provide a kind of and can open fast fault recognition method in distance protection transmission line distance protecting, improve the resistance to transition resistance ability of distance protection, overcome the deficiency that conventional method is only utilized single features.

Summary of the invention

For overcoming above-mentioned the deficiencies in the prior art, the invention provides fault recognition method in a kind of transmission line distance protecting, the method utilization is at current asymmetry degree m-positive sequence voltage cosine component in plane, utilize simultaneously m and two kinds of feature identification circuit faults, can open distance protection while there is line fault during out-of-step blocking fast, have improved open sensitivity and the open rapidity of symmetric fault of unbalanced fault.

Realizing the solution that above-mentioned purpose adopts is:

A fault recognition method in transmission line distance protecting, its improvements are: said method comprising the steps of:

I, obtain protection installation place three-phase voltage and three-phase current;

II, determine that take φ is positive sequence voltage, forward-order current, negative-sequence current and the zero-sequence current of benchmark mutually;

III, determine the current asymmetry degree of described protection installation place;

IV, determine the angle between described positive sequence voltage and described forward-order current;

V, according to current asymmetry degree plane, carry out Fault Identification.

Further, in described Step II, according to described three-phase voltage and three-phase current, by following formula, determine that respectively take φ is the forward-order current of benchmark mutually negative-sequence current zero-sequence current and positive sequence voltage

${\stackrel{.}{I}}_{\mathrm{\φ}0}=\frac{1}{3}({\stackrel{.}{I}}_{\mathrm{\φ}}+{\stackrel{.}{I}}_B+{\stackrel{.}{I}}_C)$

In formula, for φ phase current; be respectively the electric current of other two-phase; for φ phase voltage; B is the hysteresis phase of φ phase mutually, and C is the leading phase of φ phase mutually, for the hysteresis phase voltage of φ phase, leading phase voltage for φ phase.

Further, in described Step II I, by following formula, determine described current asymmetry degree m:

$m=\frac{\left|{\stackrel{.}{I}}_{\mathrm{\φ}2}\right|+\left|{\stackrel{.}{I}}_{\mathrm{\φ}0}\right|}{\left|{\stackrel{.}{I}}_{\mathrm{\φ}1}\right|}$

In formula, be respectively that to take φ be forward-order current, negative-sequence current, the zero-sequence current of benchmark mutually.

Further, in described step IV, by following formula, determine the angle between described positive sequence voltage and described forward-order current:

In formula, for take φ, be the zero-sequence current of benchmark mutually, for take φ, be the forward-order current of benchmark mutually; for positive sequence voltage and forward-order current between angle, for take φ, be the positive sequence voltage of benchmark mutually, for take φ, be the forward-order current of benchmark mutually, the value of φ is A, B, C three-phase, for perunit value, benchmark is protection installation place φ phase voltage.

Further, in described step V, according to the current asymmetry degree of described protection installation place and current asymmetry degree plane, carry out Fault Identification.

Further, described step V comprises the following steps:

S501, judgement whether set up, set up and be judged as unbalanced fault, open distance protection, otherwise enter step S502;

S502, judgement whether set up, set up the electric current unsymmetrical plan of writing afterwards last cycle otherwise, locking distance protection;

S503, compare the electric current unsymmetrical plan of described last cycle and 0.3pu, if be judged as symmetric fault, open distance protection;

If time delay open distance protection I, II section, open distance protection III section.

Compared with prior art, the present invention has following beneficial effect:

1, the inventive method comprehensive utilization current asymmetry degree and U1cos φ feature, improve existing transmission line distance protecting performance when fault and overload in vibration;

2, the inventive method can accurately be identified unbalanced fault and symmetric fault, improves the resistance to transition resistance ability of ground distance protection simultaneously;

3, in method of the present invention without manually adjusting, avoided tuning error;

4, method of the present invention has very important meaning to the safe and stable operation of electrical network and restriction accident expanded range;

5, provided by the invention a kind of based on two dimensional surface, comprehensive utilization current asymmetry degree and U ₁cos φ ₁two kinds of features are identified symmetric fault and unbalanced fault, the method of fast open distance protection, overcome conventional method and only utilized the deficiency of single features, improve the resistance to transition resistance ability of distance protection simultaneously, for safe and stable operation and the restriction accident expanded range of electrical network, there is very important meaning;

6, the present invention is directed to transmission line distance protecting fault during out-of-step blocking and open again and design, utilize plane characterizes line fault, compares traditional open condition, for unbalanced fault, utilize m with combine and can improve through compared with great transition grounding through resistance fault, utilize variable quantity can improve the breakaway speed of symmetric fault.

Accompanying drawing explanation

Fig. 1 is method flow diagram of the present invention;

Fig. 2 be in the present invention current asymmetry degree m with graph of a relation.

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.

As shown in Figure 1, Fig. 1 is method flow diagram of the present invention, and in a kind of transmission line distance protecting provided by the invention, fault recognition method comprises the following steps:

Step 1, obtain protection installation place three-phase voltage and three-phase current;

Step 2, determine that take φ is positive sequence voltage, forward-order current, negative-sequence current and the zero-sequence current of benchmark mutually;

Step 3, determine the current asymmetry degree of described protection installation place;

Step 4, determine the angle between described positive sequence voltage and described forward-order current

Step 5, according to current asymmetry degree plane, carry out Fault Identification.

In step 1, use voltage sensor and current sensor to obtain respectively three-phase voltage and the three-phase current of protection installation place.

In step 2, according to described three-phase voltage and three-phase current, by following formula, determine that respectively take φ is the forward-order current of benchmark mutually negative-sequence current zero-sequence current and positive sequence voltage

Take A mutually as forward-order current, negative-sequence current, zero-sequence current and the positive sequence voltage of benchmark respectively as shown in the formula:

${\stackrel{.}{I}}_{A0}=\frac{1}{3}({\stackrel{.}{I}}_A+{\stackrel{.}{I}}_B+{\stackrel{.}{I}}_C)$

Take B mutually as forward-order current, negative-sequence current, zero-sequence current and the positive sequence voltage of benchmark respectively as shown in the formula:

${\stackrel{.}{I}}_{B0}=\frac{1}{3}({\stackrel{.}{I}}_A+{\stackrel{.}{I}}_B+{\stackrel{.}{I}}_C)$

Take C mutually as forward-order current, negative-sequence current, zero-sequence current and the positive sequence voltage of benchmark respectively as shown in the formula:

${\stackrel{.}{I}}_{C0}=\frac{1}{3}({\stackrel{.}{I}}_A+{\stackrel{.}{I}}_B+{\stackrel{.}{I}}_C)$

In step 3, by following formula, determine described current asymmetry degree:

$m=\frac{\left|{\stackrel{.}{I}}_{\mathrm{\φ}2}\right|+\left|{\stackrel{.}{I}}_{\mathrm{\φ}0}\right|}{\left|{\stackrel{.}{I}}_{\mathrm{\φ}1}\right|}$

In formula, be respectively that to take arbitrary be forward-order current, negative-sequence current, the zero-sequence current of benchmark mutually.

In step 4, by following formula, determine the angle between described positive sequence voltage and described forward-order current:

In formula, for take φ, be the zero-sequence current of benchmark mutually, for take φ, be the forward-order current of benchmark mutually; for positive sequence voltage and forward-order current between angle, for take φ, be the positive sequence voltage of benchmark mutually, for take φ, be the forward-order current of benchmark mutually, the value of φ is A, B, C three-phase, for perunit value, benchmark is protection installation place φ phase voltage.

In step 5, according to the current asymmetry degree of described protection installation place and current asymmetry degree plane, carry out Fault Identification.Specifically comprise the following steps:

S501, judgement whether set up, set up and be judged as unbalanced fault, open distance protection, otherwise enter step S502;

S502, judgement whether set up, set up the electric current unsymmetrical plan of writing afterwards last cycle otherwise, locking distance protection;

S503, compare the electric current unsymmetrical plan of described last cycle and 0.3pu, if be judged as symmetric fault, open distance protection;

If time delay open distance protection I, II section, directly open distance protection III section.

As shown in Figure 2, Fig. 2 be in the present invention current asymmetry degree m with graph of a relation; Transverse axis is current asymmetry degree m, and the longitudinal axis is positive sequence voltage cosine component wherein current asymmetry degree m characterizes unbalanced fault, characterize symmetric fault, utilize simultaneously m and can characterize through high resistance earthing fault the mathematic(al) representation of its mean camber line curve right side is characterize unbalanced fault occurs, left side characterizes symmetric case (normally operation or symmetric fault).

Finally should be noted that: above embodiment is only for illustrating the application's technical scheme but not restriction to its protection range; although the application is had been described in detail with reference to above-described embodiment; those of ordinary skill in the field are to be understood that: those skilled in the art still can carry out all replacements that becomes more, revises or be equal to the embodiment of application after reading the application; but these change, revise or be equal to replacement, within the claim protection range all awaiting the reply in application.

Claims (6)

1. a fault recognition method in transmission line distance protecting, is characterized in that: said method comprising the steps of:

I, obtain protection installation place three-phase voltage and three-phase current;

II, determine that take φ is positive sequence voltage, forward-order current, negative-sequence current and the zero-sequence current of benchmark mutually;

III, determine the current asymmetry degree of described protection installation place;

IV, determine the angle between described positive sequence voltage and described forward-order current;

V, according to current asymmetry degree plane, carry out Fault Identification.

2. the method for claim 1, is characterized in that: in described Step II, according to described three-phase voltage and three-phase current, by following formula, determine that respectively take φ is the forward-order current of benchmark mutually negative-sequence current zero-sequence current and positive sequence voltage

${\stackrel{.}{I}}_{\mathrm{\φ}0}=\frac{1}{3}({\stackrel{.}{I}}_{\mathrm{\φ}}+{\stackrel{.}{I}}_B+{\stackrel{.}{I}}_C)$

In formula, for φ phase current; be respectively the electric current of other two-phase; for φ phase voltage; for the hysteresis phase voltage of φ phase, leading phase voltage for φ phase.

3. the method for claim 1, is characterized in that: in described Step II I, by following formula, determine described current asymmetry degree m:

$m=\frac{\left|{\stackrel{.}{I}}_{\mathrm{\φ}2}\right|+\left|{\stackrel{.}{I}}_{\mathrm{\φ}0}\right|}{\left|{\stackrel{.}{I}}_{\mathrm{\φ}1}\right|}$

In formula, be respectively that to take φ be forward-order current, negative-sequence current, the zero-sequence current of benchmark mutually.

4. the method for claim 1, is characterized in that: in described step IV, by following formula, determine the angle between described positive sequence voltage and described forward-order current:

In formula, for take φ, be the zero-sequence current of benchmark mutually, for take φ, be the forward-order current of benchmark mutually; for positive sequence voltage and forward-order current between angle, for take φ, be the positive sequence voltage of benchmark mutually, for take φ, be the forward-order current of benchmark mutually, the value of φ is A, B, C three-phase, for perunit value, benchmark is protection installation place φ phase voltage.

5. the method for claim 1, is characterized in that: in described step V, according to the current asymmetry degree of described protection installation place and current asymmetry degree plane, carry out Fault Identification.

6. method as claimed in claim 5, is characterized in that: described step V comprises the following steps:

S501, judgement whether set up, set up and be judged as unbalanced fault, open distance protection, otherwise enter step S502;

S502, judgement whether set up, set up the electric current unsymmetrical plan of writing afterwards last cycle otherwise, locking distance protection;

S503, compare the electric current unsymmetrical plan of described last cycle and 0.3pu, if be judged as symmetric fault, open distance protection;

If time delay open distance protection I, II section, open distance protection III section.