阅读说明：本技术 一种基于自适应的选择性定子接地保护方法 (Selective stator grounding protection method based on self-adaption ) 是由 邓丛林 于 2019-11-19 设计创作，主要内容包括：本发明涉及继电保护领域,其公开了一种基于自适应的选择性定子接地保护方法,解决现有技术中的定子接地保护方案存在选择性受局限,灵敏度低,可靠性低的问题。该方法包括：根据采集到的零序电压值大小判断是否出现接地故障；当出现接地故障时,定子接地保护根据方向判据决策动作与否：通过采集机端零序电压和零序电流,求出两个向量间的角度γ,当角度γ在动作区内时,保护动作跳闸；当在动作区之外时,保护不动作；所述方向判据中的动作灵敏角Φ的确定方式为：通过采集发电机出口断路器位置,通过位置判断主接线运行方式,进而把方向判据的动作灵敏度角Φ自动切换到与该主接线匹配的预设定值上。(The invention relates to the field of relay protection, discloses a self-adaptive selective stator grounding protection method, and solves the problems of limited selectivity, low sensitivity and low reliability of a stator grounding protection scheme in the prior art. The method comprises the following steps: judging whether a ground fault occurs according to the magnitude of the acquired zero sequence voltage value; when the grounding fault occurs, the stator grounding protection decides whether to act according to the direction criterion: calculating an angle gamma between two vectors by acquiring a zero sequence voltage and a zero sequence current at a machine end, and protecting the action trip when the angle gamma is in an action area; when outside the action zone, the protection does not act; the motion sensitivity angle phi in the direction criterion is determined in the following manner: the position of the breaker at the outlet of the generator is collected, and the operation mode of the main wiring is judged through the position, so that the action sensitivity angle phi of the direction criterion is automatically switched to a preset value matched with the main wiring.)

1. An adaptive-based selective stator ground protection method, comprising:

judging whether a ground fault occurs according to the magnitude of the acquired zero sequence voltage value;

when the grounding fault occurs, the stator grounding protection decides whether to act according to the direction criterion:

calculating an angle gamma between two vectors by acquiring a zero sequence voltage and a zero sequence current at a machine end, and protecting the action trip when the angle gamma is in an action area; when outside the action zone, the protection does not act;

the motion sensitivity angle phi in the direction criterion is determined in the following manner:

the position of the breaker at the outlet of the generator is collected, and the operation mode of the main wiring is judged through the position, so that the action sensitivity angle phi of the direction criterion is automatically switched to a preset value matched with the main wiring.

2. The adaptive-based selective stator ground protection method of claim 1,

the determination method of the motion sensitivity angle Φ in the direction criterion specifically includes:

the stator grounding protection of each unit acquires GCB position signals of all unit outlets, and the inside of the stator grounding protection of each unit is completely set and corresponds to the action sensitivity angle phi under n different operation modes_1～nWhen the stator grounding protection of a certain unit judges that the main wiring operates in the mth operation mode according to the collected GCB position signal, the fixed value of the action sensitivity angle of the protection is automatically switched to the corresponding phi_m。

Technical Field

The invention relates to the field of relay protection, in particular to a selective stator grounding protection method based on self-adaptation.

Background

When a generator is connected with a main transformer to operate, a stator winding or an outgoing line of the generator is lowered in insulation performance due to too long operation time, and a single-phase ground fault may occur, namely, a certain phase of a fixed armature winding inside the generator is connected with the ground. A stator ground protection reflecting this type of fault is then required to remove the faulty equipment. Fig. 1 illustrates the case of a phase C ground fault, where G represents an alternator, T represents a transformer, GCB represents a generator outlet breaker, and A, B, C represents an electrical three-phase loop.

At present, the stator grounding protection can be divided into two types in principle: fundamental zero-sequence voltage principle and injection principle. When single-phase grounding of the stator occurs, zero sequence voltage of a terminal fundamental wave can be increased, and the grounding resistance value can be obviously reduced relative to the ground resistance value. The zero sequence voltage value of the fundamental wave at the generator end is protected and collected, and the alarm is given to stop the generator by judging the rise of the zero sequence voltage of the fundamental wave at the generator end; the injection protection measures the insulation resistance value of the stator loop relative to the ground, and alarms and stops the machine by judging the reduction of the insulation resistance value of the stator loop relative to the ground.

It can be seen from the above description that both the fundamental zero-sequence voltage protection and the injection protection have a common disadvantage, i.e. they have no selectivity, and when they are used for expanding the unit wiring, when a single-phase earth fault occurs in the internal winding and outgoing line of a certain generator, the earth protection of the stator of the other non-fault generators will trip, thus expanding the accident range. Fig. 2 illustrates a multi-unit parallel system, in case of a single-phase ground fault inside a G1 unit, since the terminals of the three units are connected to each other, the PT (voltage transformer) at the terminal of each unit measures the same zero sequence voltage value, which causes the G2 and G3 units to trip, and the accident scope is expanded.

In order to improve the selectivity of stator grounding protection action, action delay coordination among different units is generally adopted at present to reduce the probability of non-fault tripping; for example, the stator ground protection of the unit No. 1 is delayed for 0.3s trip, the stator ground protection of the unit No. 2 is delayed for 0.6s trip, when the stator ground protection fault occurs to the unit No. 1, the stator ground protection of the unit No. 1 trips to remove the fault first, and the generator No. 2 cannot trip due to long delay, so that the unit continues to operate without being influenced.

However, this method has the disadvantage that the selectivity of the stator ground protection can only be improved by 50%, and only the selectivity of the protection can be ensured when the unit internal fault is configured with the short-delay protection, and the non-fault tripping condition can also occur when the unit internal fault is configured with the long-delay protection. That is, if the stator ground fault occurs in the generator No. 2, the generator No. 1 stator ground protection will also trip first.

In order to further improve the selectivity of the stator ground protection action when the generator has a stator ground fault, some manufacturers also adopt fundamental wave zero sequence voltage protection with a zero sequence direction, the protection judges whether the generator internal ground fault or external ground fault is the generator internal ground fault or the generator external ground fault according to an angle gamma between zero sequence voltage and zero sequence current at a generator end, fig. 3 is a schematic diagram of the principle, fig. 4 is a schematic diagram of the action range, a shadow area in the diagram is an action area, an opposite direction is an inaction area, the whole partition is determined by an action sensitivity angle phi, when the gamma value is in the shadow area, the protection action trips, and when the gamma value is in the opposite direction inaction area, the protection does not act.

Based on the principle, when the fault is judged to occur in the generator winding, the generator is tripped firstly, and when the fault is judged to occur in other generators, the generator is tripped in a delayed mode. The method ensures that the protection can be selectively tripped when any ground fault occurs, and the accident range cannot be enlarged. However, the protection of the principle needs to set the action sensitive angle phi, the fixed value is comprehensively determined by the ground capacitance and the impedance of the equipment connected with the generator winding, the bus and other main wirings in parallel, and is influenced by the number of the generators connected in parallel, the current solution is to take the arithmetic and the average value of the measured sensitive angles under different unit operation numbers as a fixed setting value, and the mode can greatly reduce the sensitivity of the direction criterion, has insufficient reliability, and can cause misoperation or refusal in serious cases.

In conclusion, the stator grounding protection scheme in the prior art has the problems of limited selectivity, low sensitivity and low reliability.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: a self-adaptive selective stator grounding protection method is provided, and the problems of limited selectivity, low sensitivity and low reliability of a stator grounding protection scheme in the prior art are solved.

The technical scheme adopted by the invention for solving the technical problems is as follows:

an adaptive-based selective stator ground protection method, comprising:

judging whether a ground fault occurs according to the magnitude of the acquired zero sequence voltage value;

when the grounding fault occurs, the stator grounding protection decides whether to act according to the direction criterion:

calculating an angle gamma between two vectors by acquiring a zero sequence voltage and a zero sequence current at a machine end, and protecting the action trip when the angle gamma is in an action area; when outside the action zone, the protection does not act;

the motion sensitivity angle phi in the direction criterion is determined in the following manner:

the position of the breaker at the outlet of the generator is collected, and the operation mode of the main wiring is judged through the position, so that the action sensitivity angle phi of the direction criterion is automatically switched to a preset value matched with the main wiring.

As a further optimization, the determination method of the motion sensitivity angle Φ in the direction criterion specifically includes:

the stator grounding protection of each unit acquires GCB position signals of all unit outlets, and the inside of the stator grounding protection of each unit is completely set and corresponds to the action sensitivity angle phi under n different operation modes_1～nWhen the stator grounding protection of a certain unit judges that the main wiring operates in the mth operation mode according to the collected GCB position signal, the fixed value of the action sensitivity angle of the protection is automatically switched to the corresponding phi_m。

The invention has the beneficial effects that:

compared with two modes of delay matching and fixed sensitivity angle fixed value direction protection between multiple sets, the method has the advantages that the main wiring operation mode is automatically identified through the GCB position, and then the sensitivity angle fixed value is automatically switched, the selectivity of protection actions is guaranteed, the reliability of the protection actions is greatly improved, the wiring is simple, and the operation is safe and reliable.

Drawings

FIG. 1 is a schematic diagram of a phase C ground fault;

FIG. 2 is a schematic diagram of a multi-unit parallel system;

FIG. 3 is a schematic diagram of directional fundamental zero sequence voltage protection;

FIG. 4 is a schematic diagram of the action range of the directional fundamental zero-sequence voltage protection;

fig. 5 is a flow chart of the adaptive-based selective stator ground protection method of the present invention.

Detailed Description

The invention aims to provide a self-adaptive selective stator grounding protection method, which solves the problems of limited selectivity, low sensitivity and low reliability of a stator grounding protection scheme in the prior art.

The core idea is as follows: when solving multimachine parallel system stator ground protection action selectivity, innovatively proposed through gathering generator export circuit breaker position, judge main wiring operation mode through the position, and then on the action sensitivity angle definite value automatic switch of direction criterion is to the definite value that matches with this main wiring, the absolute selectivity of protection has been ensured promptly, the sensitivity of protection action has been improved greatly again, prevent maloperation or refusing, whole design need not to increase equipment, only need gather each unit circuit breaker position signal, the wiring is simple, operation safe and reliable. Therefore, the scheme of the invention not only avoids the insufficient selectivity caused by the action delay coordination among different traditional machine groups, but also avoids the insufficient sensitivity caused by the fixed value of the average sensitivity angle under a plurality of operation modes depending on the direction protection, thereby greatly improving the selectivity and reliability of the stator ground protection, avoiding the non-fault tripping and reducing the unnecessary power failure loss.

In order to make the grounding protection action of the stator of the multi-machine parallel system completely selective and have good sensitivity in various operation modes, the invention adopts the following means in specific realization and the flow is shown in figure 5:

1) firstly, judging whether a ground fault occurs according to the magnitude of the acquired zero sequence voltage value;

2) in order to ensure that the stator grounding protection in a multi-machine parallel system has complete selectivity, the direction criterion of a stator grounding protection belt is determined, an angle gamma between two vectors is solved by acquiring zero-sequence voltage and zero-sequence current at the machine end, and when the angle gamma is in an action area, the action is protected from tripping; when outside the action zone, the protection does not act;

3) in order to ensure that the protection is possible in various operating modesThe reliability and the sensitivity are good, the stator grounding protection of each unit collects GCB position signals of all unit outlets, and the interior of the stator grounding protection of each unit is completely set and corresponds to the motion sensitivity angle phi under n different operation modes_1～nWhen the stator grounding protection of a certain unit judges that the main wiring operates in the mth operation mode according to the collected GCB position signal, the fixed value of the action sensitivity angle of the protection is automatically switched to the corresponding phi_m。

Taking the scheme applied to the multi-machine parallel system shown in fig. 2 as an example, the stator grounding protection of G1 respectively collects the circuit breaker position signals at the outlets of the No. 1, No. 2 and No. 3 machine sets, and when only the No. 1 machine set runs, namely only QF1 is in the closed position, the directional criterion action sensitivity angle fixed value is corresponding to phi₁(ii) a When only two units are in operation, namely any two of QF1, QF2 and QF3 are in closed position and the other is in separated position, the fixed value of the direction criterion action sensitivity angle is phi₂(ii) a When all three units are in operation, namely QF1, QF2 and QF3 are in the closed position, the action sensitivity angle fixed value of the direction criterion corresponds to phi₃。

In summary, compared with the traditional multi-unit delay matching mode or the fixed sensitivity angle mode, the method has the advantages that the position signals of the outlet circuit breakers of all the units are collected, the operation mode of the main wiring is automatically identified according to the signals, and the action sensitivity angle fixed value of the direction criterion is automatically switched, so that the fixed value can be self-adapted to the change of the main wiring, the direction criterion always has the highest sensitivity, the selectivity and the reliability of stator ground protection are greatly improved, non-fault tripping is avoided, and unnecessary power failure loss is reduced.