A system and method for realizing dead-zone-free configuration of differential protection of pumped storage power station

Abstract

The present invention discloses a system and method for implementing a zero-dead-zone configuration of differential protection for a pumped-storage power station. The system includes a unit differential protection circuit and a main transformer differential protection circuit. The generator motor is equipped with the unit differential protection circuit, and the main transformer differential protection circuit is equipped with the main transformer differential protection circuit. The main transformer differential protection circuit includes a commutation switch and a generator output circuit breaker (GCB). The method and system for implementing a zero-dead-zone configuration of differential protection for a pumped-storage power station proposed in the present invention utilizes an operating condition identification mechanism to automatically adjust the composition of the operating current and braking current under pumping direction startup conditions without locking the main transformer differential protection. This ensures that the generator motor and main transformer of the pumped-storage power station can be equipped with a set of differential protection that can be put into operation under various operating conditions.

Description

Technical Field

[0001] The present invention relates to a system and method for realizing dead-zone-free configuration of differential protection of a pumped storage power station, belonging to the technical field of power system relay protection. Background Art

[0002] Currently, differential protection for pumped-storage power station units and main transformers is generally configured as follows: unit differential protection and small differential protection, and main transformer differential protection and small differential protection, based on their actual protection ranges. The generator motor and main transformer are each equipped with two sets of differential protection. The protection ranges of both the unit differential protection and the main transformer differential protection include the generator output circuit breaker (GCB), achieving cross-configuration. However, during unit startup conditions in the pumping direction, when both the commutation switch and the output circuit breaker are actually open, the GCB receives a low-frequency current on the unit side, which cannot form a differential circuit with the main transformer high-voltage branch current, the auxiliary power branch current, and the SFC branch current. This can directly lead to false activation of the main transformer differential protection. To eliminate the impact of the unit startup branch current circuit, this solution blocks the unit differential protection and the main transformer differential protection, retaining only the unit differential protection and the main transformer differential protection, which are unaffected by the unit's operating conditions. The disadvantage of this solution is that when the unit is started in the pumping direction, since the two sets of large differentials are locked, only two sets of small differentials are retained. As a result, if a fault occurs in the area from the phase change switch to the GCB, no differential protection can be activated, and there is a protection dead zone. At this time, the protection device can only rely on the backup protection to coordinate the action, sacrificing the sensitivity and speed of the protection, which is not good for the protected equipment. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the problem that the conventional configuration of differential protection in pumped storage power stations has a protection dead zone due to the exit of large differential protection under the pumping direction starting condition. A system and method for realizing the dead zone-free configuration of differential protection is proposed, which ensures that the generator motor and main transformer of the pumped storage power station can be equipped with a set of differential protection that can be put into operation under various operating conditions.

[0004] To solve the above technical problems, the present invention provides a system for implementing dead-zone-free configuration of differential protection for a pumped-storage power station, which is characterized by comprising: a small differential protection circuit for a unit and a large differential protection circuit for a main transformer; the generator motor is equipped with the small differential protection circuit for the unit, and the main transformer is equipped with the large differential protection circuit for the main transformer; the main transformer large differential protection circuit includes a commutation switch and a generator outlet circuit breaker (GCB), and the main transformer is connected to the generator motor via the commutation switch and the generator outlet circuit breaker (GCB) in sequence.

[0005] As a preferred embodiment, the unit small differential protection circuit is put into operation under all working conditions; the main transformer large differential protection circuit is put into operation under the working conditions of distinguishing whether it is a pumping direction or not.

[0006] As a preferred embodiment, in the non-pumping direction starting condition, the operating current I d and braking current I q The structure is shown in the following formula (1):

[0007]

[0008] in, is the branch current on the high voltage side of the main transformer, is the branch current of the plant transformer, It is the branch current of the static variable frequency starting device SFC. is the GCB unit side current.

[0009] As a preferred embodiment, under the pumping direction starting condition, the operating current I d and braking current I q The structure is shown in the following formula (2):

[0010]

[0011] in, is the branch current on the high voltage side of the main transformer, is the branch current of the plant transformer, It is the branch current of the static frequency conversion starting device SFC.

[0012] The present invention also proposes a method for realizing the dead zone-free configuration of differential protection of a pumped storage power station, comprising: configuring a small differential protection circuit for the generator motor and configuring a large differential protection circuit for the main transformer; respectively collecting the branch current on the high voltage side of the main transformer; Auxiliary transformer branch current Static frequency conversion starting device SFC branch current GCB unit side current Differentiate the working conditions and calculate the operating current I of the main transformer large differential protection circuit d and braking current I q .

[0013] As a preferred embodiment, the unit small differential protection circuit is put into operation under all working conditions; the main transformer large differential protection circuit is put into operation under the working conditions of distinguishing whether it is a pumping direction or not.

[0014] As a preferred embodiment, in the non-pumping direction starting condition, the operating current I d and braking current I q The structure is shown in the following formula (3):

[0015]

[0016] in, is the branch current on the high voltage side of the main transformer, is the branch current of the plant transformer, It is the branch current of the static variable frequency starting device SFC. is the GCB unit side current.

[0017] As a preferred embodiment, under the pumping direction starting condition, the operating current I d and braking current I q The structure is shown in the following formula (4):

[0018]

[0019] in, is the branch current on the high voltage side of the main transformer, is the branch current of the plant transformer, It is the branch current of the static frequency conversion starting device SFC.

[0020] Beneficial effects achieved by the present invention: The present invention proposes a method and system for realizing a dead zone-free configuration of differential protection for a pumped storage power station, which automatically adjusts the operating current I under the pumping direction starting condition through the working condition identification mechanism. d and braking current I q The structure does not require locking the main transformer large differential protection, thereby ensuring that the pumped storage power station generator motor and main transformer can be equipped with a set of differential protection that can be put into operation under various operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is an electrical schematic diagram of the application principle of a system for implementing a dead-zone-free configuration of differential protection for a pumped storage power station.

[0022] Figure 2 The present invention is an application topology flow chart of a method for realizing a dead-zone-free configuration of differential protection of a pumped storage power station. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] like Figure 1As shown, the overall circuit of Example 1 includes: eight current transformers, namely, 1CT for measuring the current on the neutral point side of the unit, 2CT for measuring the current on the GCB unit side, 3CT for measuring the current on the GCB unit side, 4CT for measuring the current on the GCB main transformer side, 5CT for measuring the current on the main transformer side of the phase-changing switch, 6CT for measuring the branch current on the high-voltage side of the main transformer, 7CT for measuring the plant power branch current, and 8CT for measuring the SFC branch current; a phase-changing switch; a generator output circuit breaker GCB; a drag switch and a dragged switch; a plant transformer; a unit pumping direction starting circuit consisting of an SFC input transformer, an SFC, and a starting bus; a generator motor; and a main transformer.

[0025] The unit small differential protection circuit is composed of 1CT measuring the current on the neutral point side of the unit and 2CT measuring the current on the GCB unit side.

[0026] The main transformer differential protection circuit is composed of 6CTs for measuring the branch current on the high-voltage side of the main transformer, 7CTs for measuring the auxiliary power branch current, 8CTs for measuring the SFC branch current, and 3CTs for measuring the GCB unit side current.

[0027] More specifically, under the non-pumping direction starting condition, the main transformer large differential protection circuit is composed of 6CTs measuring the branch current on the high-voltage side of the main transformer, 7CTs measuring the auxiliary power branch current, 8CTs measuring the SFC branch current, and 3CTs measuring the GCB unit side current; under the non-pumping direction starting condition, the operating current I d and braking current I q The structure is shown in the following formula (5):

[0028]

[0029] in, is the branch current on the high voltage side of the main transformer, is the branch current of the plant transformer, It is the branch current of the static variable frequency starting device SFC. is the GCB unit side current.

[0030] Under the pumping direction starting condition, the main transformer large differential protection circuit is composed of 6CT measuring the branch current on the high-voltage side of the main transformer, 7CT measuring the auxiliary power branch current and 8CT measuring the SFC branch current, that is, the 3CT current on the GCB unit side is withdrawn; under the pumping direction starting condition, the operating current I d and braking current I q The structure is shown in the following formula (6):

[0031]

[0032] in, is the branch current on the high voltage side of the main transformer, is the branch current of the plant transformer, It is the branch current of the static frequency conversion starting device SFC.

[0033] like Figure 2 As shown, a method for realizing a dead zone-free configuration of differential protection of a pumped storage power station of the present invention is applied to the differential protection of the pumped storage power station. The protection software platform program of the pumped storage power station calls the differential module and first starts the working condition identification mechanism; if it is determined that the working condition is in the pumping direction starting condition, then the action current I d and braking current I q Exit the GCB unit side current during calculation; in other working conditions, the action current I d and braking current I q The current on the GCB unit side is input during the calculation; then the differential module of the pumped storage power station starts the differential logic judgment. If the action conditions are met, the protection outlet is protected, otherwise the protection returns; finally, the differential module is exited.

[0034] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A system for realizing dead-zone-free configuration of differential protection of a pumped storage power station, characterized in that: include: The generator motor is equipped with the generator small differential protection circuit, and the main transformer is equipped with the main transformer large differential protection circuit. The main transformer large differential protection circuit includes a phase-changing switch and a generator outlet circuit breaker GCB. The main transformer is connected to the generator motor in sequence through the phase-changing switch and the generator outlet circuit breaker GCB. The unit small differential protection circuit is put into operation under all working conditions; the main transformer large differential protection circuit is put into operation under the working conditions of distinguishing whether it is starting in the pumping direction or not; Under the non-pumping direction starting condition, the operating current I d and braking current I q The structure is shown in the following formula (1): in, is the branch current on the high voltage side of the main transformer, is the branch current of the plant transformer, It is the branch current of the static variable frequency starting device SFC. is the GCB unit side current; Under the pumping direction starting condition, the operating current I d and braking current I q The structure is shown in the following formula (2): in, is the branch current on the high voltage side of the main transformer, is the branch current of the plant transformer, It is the branch current of the static frequency conversion starting device SFC.

2. A method for realizing dead-zone-free configuration of differential protection of a pumped storage power station, characterized in that: Specifically include: The generator motor is equipped with a small differential protection circuit, and the main transformer is equipped with a large differential protection circuit; the branch current on the high-voltage side of the main transformer is collected separately. Auxiliary transformer branch current Static frequency conversion starting device SFC branch current GCB unit side current Differentiate the working conditions and calculate the operating current I of the main transformer large differential protection circuit d and braking current I q ; The unit small differential protection circuit is put into operation under all working conditions; the main transformer large differential protection circuit is put into operation under the working conditions of distinguishing whether it is starting in the pumping direction or not; Under the non-pumping direction starting condition, the operating current I d and braking current I q The structure is shown in the following formula (1): in, is the branch current on the high voltage side of the main transformer, is the branch current of the plant transformer, It is the branch current of the static variable frequency starting device SFC. is the GCB unit side current; Under the pumping direction starting condition, the operating current I d and braking current I q The structure is shown in the following formula (2): in, is the branch current on the high voltage side of the main transformer, is the branch current of the plant transformer, It is the branch current of the static frequency conversion starting device SFC.

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