GCB Incomplete Phase Detection Method Based on Zero-Sequence Voltage Proportional Differential

Abstract

The GCB non-full-phase detection method based on zero-sequence voltage proportional differential includes: Step 1: Acquiring the zero-sequence voltages of the voltage transformers on both sides of the generator outlet circuit breaker GCB. The zero-sequence voltage on the generator side is [value], and the zero-sequence voltage on the transformer side is [value]. Step 2: Calculating the amplitude ratio of the two zero-sequence voltages acquired in Step 1. When the ratio is greater than or equal to the set parameter K... set Step 3: Calculate the phase angle difference between the two zero-sequence voltages acquired in Step 1. When the difference meets the set parameter range; Step 4: When both the amplitude criterion and the phase angle criterion are met simultaneously and exceed the set time value t. set In such cases, the circuit breaker will trip or alarm. This method is based on a clear principle, is easy to calculate, and is readily applicable in practical relay protection engineering, showing promising practical value.

Description

Technical Field

[0001] This invention relates to the field of GCB non-full-phase fault detection technology, specifically to a GCB non-full-phase detection method based on zero-sequence voltage proportional differential. Background Technology

[0002] GCB, also known as generator output circuit breaker, generally adopts a three-phase linkage mechanism and is configured between the generator and the step-up transformer. It is used for grid connection, disconnection, or interruption of short-term fault current. For units such as hydro-generators and pumped storage units, which undertake more peak-shaving tasks, the frequent start-up and shutdown and the large number of GCB opening and closing operations greatly increase the probability of GCB non-full-phase faults.

[0003] Traditional GCB (Generator Circuit Breaker) non-full-phase protection determines the non-full-phase operation state of the circuit breaker by detecting the position of the three-phase inconsistent contacts, the magnitude of the negative-sequence current, and the zero-sequence current. However, for three-phase interlocked circuit breakers, since they cannot provide three-phase inconsistent contacts, and the negative-sequence and zero-sequence currents are relatively small at the initial stage of grid connection or at the moment of disconnection, faults cannot be accurately detected. This results in the unit being subjected to negative-sequence current for a long time, posing a threat to the safe operation of the unit.

[0004] Several patents have addressed this issue. A Chinese patent proposes a "GCB Incomplete Phase Detection Method Based on Injection Principle" (application number: 20211135709.2), which overcomes the aforementioned problems. However, due to the need to inject low-frequency signals into the high-voltage system, signal injection and extraction are difficult. Another Chinese patent, "An Implementation Method for Incomplete Phase Protection Logic of a Three-Phase Interlocking Circuit Breaker" (application number: 20211096463.8), proposes a multi-mode, multi-criteria incomplete phase protection logic for a three-phase interlocking circuit breaker; however, this logic involves multiple state transition judgments, making it complex and difficult to apply in the field. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for detecting GCB non-complete phase based on zero-sequence voltage proportional differential. This method can accurately determine whether GCB is in a non-complete phase state simply by comparing the amplitude and phase of the zero-sequence voltages on both sides of the GCB. The method has a clear principle and good performance.

[0006] The technical solution adopted in this invention is as follows:

[0007] The GCB non-full-phase detection method based on zero-sequence voltage proportional differential includes the following steps:

[0008] Step 1: Collect the zero-sequence voltage of the voltage transformers on both sides of the generator output circuit breaker GCB. The zero-sequence voltage on the side closer to the generator is... The zero-sequence voltage on the side closest to the transformer is

[0009] Step 2: Calculate the amplitude ratio of the two zero-sequence voltages acquired in Step 1. When the ratio is greater than or equal to the set parameter K... set At that time, the amplitude criterion is satisfied:

[0010]

[0011] Step 3: Calculate the phase angle difference between the two zero-sequence voltages acquired in Step 1. When the difference meets the set parameter range, the phase angle criterion is satisfied:

[0012]

[0013] Step 4: When both the amplitude criterion and the phase criterion are satisfied simultaneously and the set time value t is exceeded. set When the fault is detected, the GCB circuit breaker will trip or alarm if a non-full-phase fault occurs.

[0014] In step one, the zero-sequence voltage can be directly acquired from the open delta winding of the voltage transformer, or calculated using the three-phase voltage.

[0015] In step three, the difference must satisfy the set parameter range: sensitivity angle θ set Expand on both sides The angle allows the phase angle criterion to be more adaptable.

[0016] This method includes the amplitude scaling parameter K. set With the sensitivity angle parameter θ set The setting method is described in this step, which outlines the setting methods for the set values ​​in steps two and three:

[0017]

[0018]

[0019] In the formula: This refers to the total capacitive reactance of the three phases to ground on one side of the transformer.

[0020] ω=2πf=2π×50=100π is the rated electrical angular frequency of the terminal voltage.

[0021] C t This is the single-phase-to-ground capacitance value on the low-voltage side of the transformer, which includes the low-voltage side capacitance of the transformer and the transformer-side GCB-to-ground capacitance. The total capacitive reactance to ground on one side of the generator;

[0022] C g This is the single-phase ground capacitance value on the generator side, which includes the generator-to-ground capacitance, the generator-side GCB-to-ground capacitance, and the enclosed busbar-to-ground capacitance.

[0023] Z n =R n +jX n =|Z n |∠α, is the equivalent impedance of the generator neutral-point grounded transformer, where: R n X is the equivalent resistance; n Equivalent reactance; α is the impedance angle;

[0024] K rel The reliability coefficient is an adjustable value, which can generally be set to 0.8 to 0.9, or it can be adjusted on-site through actual measurement.

[0025] The GCB non-full-phase detection method based on zero-sequence voltage proportional differential assumes that the three-phase capacitances to ground at the generator terminal are equal, and the capacitance value of each phase is C. g ;

[0026] The three-phase-to-ground capacitances on the low-voltage side of the main transformer are equal, with each phase capacitance value being C. t ;

[0027] The equivalent ground resistance of the generator neutral point grounding transformer is R. n The equivalent ground reactance of the neutral point grounding transformer is X. n ;

[0028] When there is a non-full-phase condition: either a single-phase disconnection or a two-phase disconnection.

[0029]

[0030] in,

[0031] This invention discloses a non-full-phase detection method for GCB based on zero-sequence voltage proportional differential, with the following technical advantages:

[0032] 1) Step 2 of this invention provides a zero-sequence voltage amplitude comparison criterion in the GCB non-complete phase detection method; Step 3 of this invention provides a zero-sequence voltage phase angle comparison criterion in the GCB non-complete phase detection method; Step 4 of this invention combines Step 2 and Step 3 to provide a GCB non-complete phase detection method. This method has a clear principle, is simple to implement, and has strong field feasibility.

[0033] 2) Amplitude scaling parameter K of the present invention set With the sensitivity angle parameter θ set The tuning method is given, and the threshold calculation method for the amplitude comparison criterion and phase angle comparison criterion in steps two and three is given. Attached Figure Description

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0035] Figure 1This is a schematic diagram showing the acquisition of zero-sequence voltage on the transformer side and zero-sequence voltage on the generator side.

[0036] Figure 2 This is a logic diagram of the GCB non-full-phase detection method based on zero-sequence voltage proportional differential.

[0037] Figure 3 This is the equivalent circuit diagram for GCB non-full-phase operation. Detailed Implementation

[0038] Working principle:

[0039] like Figure 3 As shown, assuming the three-phase capacitance to ground at the generator terminal is equal, the capacitance value of each phase is C. g The three-phase-to-ground capacitances on the low-voltage side of the main transformer are equal, with each phase having a capacitance value of C. t The equivalent ground resistance of the generator neutral point grounding transformer is R. n The equivalent ground reactance of the neutral point grounding transformer is X. n The three-phase voltages at the generator terminals are respectively The three-phase voltages on the low-voltage side of the main transformer are respectively When the generator terminal is connected to the low-voltage side of the main transformer, according to Kirchhoff's current law, we have:

[0040]

[0041] Considering:

[0042]

[0043]

[0044] have:

[0045]

[0046] or:

[0047]

[0048] in, Z n =R n +jX n =|Z n |∠α;

[0049] When all three phases are fully connected, the three-phase voltage at the generator terminals is exactly equal to the three-phase voltage on the low-voltage side of the main transformer. At this time, we have:

[0050]

[0051] When all three phases are completely disconnected, the three-phase voltage at the generator terminal and the three-phase voltage on the low-voltage side of the main transformer are two independent systems. and They are not equal, and the difference in their phase angles cycles between 0 and 2π.

[0052] When there is a non-full-phase condition: either a single-phase disconnection or a two-phase disconnection, we have:

[0053]

[0054] in,

[0055] A method for detecting incomplete phase GCB based on zero-sequence voltage proportional differential is proposed. This method compares the amplitude difference or phase angle difference of the zero-sequence voltages on both sides of the GCB to achieve detection, alarm, and tripping of the incomplete phase GCB. The method includes the following steps:

[0056] Step 1: As Figure 1 As shown, the device collects the zero-sequence voltage of the voltage transformers on both sides of the generator outlet circuit breaker GCB. The zero-sequence voltage on the side closer to the generator is... The zero-sequence voltage on the side closest to the transformer is

[0057] Wherein: the zero-sequence voltage can be directly acquired from the open delta secondary winding of the voltage transformer, or it can be obtained using the three-phase voltage according to the following formula:

[0058]

[0059]

[0060] Step 2: Calculate the amplitude ratio of the two zero-sequence voltages acquired in Step 1. When the ratio is greater than or equal to the set parameter K... set At that time, the amplitude criterion is satisfied:

[0061]

[0062] Step 3: Calculate the phase angle difference between the two zero-sequence voltages acquired in Step 1. When the difference meets the set parameter range, the phase angle criterion is satisfied:

[0063]

[0064] Wherein: the set parameter range is: sensitivity angle θ set Expand on both sides angle.

[0065] Step Four: As Figure 2 As shown, when both the amplitude criterion and the phase criterion are satisfied simultaneously and the set time value t is exceeded... setWhen a non-full-phase fault is detected in the GCB circuit breaker, automated measures are taken to trip the GCB switch or issue an alarm signal to eliminate the non-full-phase fault.

[0066] The above amplitude ratio parameter K set With the sensitivity angle parameter θ set The tuning method is as follows:

[0067]

[0068]

[0069] In the formula, C is the total capacitive reactance of the three phases to ground on one side of the transformer; t This refers to the single-phase-to-ground capacitance value on the low-voltage side of the transformer, which includes the low-voltage side capacitance of the transformer and the transformer-side GCB-to-ground capacitance, etc.

[0070] C is the total capacitive reactance of the three-phase ground on one side of the generator; g The single-phase ground capacitance value on the generator side includes the generator-to-ground capacitance, the generator-side GCB-to-ground capacitance, and the enclosed busbar-to-ground capacitance.

[0071] Z n =R n +jX n =|Z n |∠α, where R is the equivalent impedance of the generator neutral point grounding transformer. n X is the equivalent resistance. n For equivalent reactance, It is the impedance angle.

[0072] K rel The reliability coefficient is an adjustable value, which can generally be set to 0.8 to 0.9, or it can be adjusted on-site through actual measurement.

[0073] This invention discloses a method for detecting incomplete phases of a GCB (Gate Block Controller) based on zero-sequence voltage proportional differential. It achieves detection, alarm, and tripping of the incomplete phase of the GCB by comparing the amplitude difference or phase angle difference of the zero-sequence voltages on both sides of the GCB. The method has a clear principle, is simple to calculate, and is easy to promote and apply in practical relay protection engineering, showing promising practical value.

Claims

1. A non-full-phase detection method for GCB based on zero-sequence voltage proportional differential, characterized in that... Includes the following steps: Step 1: Collect the zero-sequence voltage of the voltage transformers on both sides of the generator output circuit breaker GCB. The zero-sequence voltage on the side closer to the generator is... The zero-sequence voltage on the side closest to the transformer is ; Step 2: Calculate the amplitude ratio of the two zero-sequence voltages acquired in Step 1. When the ratio is greater than or equal to the set parameter... At that time, the amplitude criterion is satisfied: ； Step 3: Calculate the phase angle difference between the two zero-sequence voltages acquired in Step 1. When the difference meets the set parameter range, the phase angle criterion is satisfied: ； Step 4: When both the amplitude criterion and the phase criterion are satisfied simultaneously and the set time limit is exceeded. When it is determined that the GCB circuit breaker has a non-full-phase fault, the output circuit breaker will trip or alarm. The method also includes an amplitude scaling parameter. With sensitivity angle parameters The adjustment; ； ； In the formula: This is the total capacitive reactance of the three-phase to ground on one side of the transformer; The rated electrical angular frequency of the terminal voltage; This is the single-phase-to-ground capacitance value on the low-voltage side of the transformer, which includes the low-voltage side capacitance of the transformer and the transformer-side GCB-to-ground capacitance. This is the total capacitive reactance of the three-phase to ground on one side of the generator; This is the single-phase ground capacitance value on the generator side, which includes the generator-to-ground capacitance, the generator-side GCB-to-ground capacitance, and the enclosed busbar-to-ground capacitance. , where is the equivalent impedance of the generator neutral point grounding transformer, where: Equivalent resistance; Equivalent reactance; , It is the impedance angle; It is an adjustable reliability coefficient.

2. The GCB non-full-phase detection method based on zero-sequence voltage proportional differential as described in claim 1, characterized in that: In step one, the zero-sequence voltage is directly acquired by the open delta winding of the voltage transformer, or calculated using the three-phase voltage.

3. The GCB non-full-phase detection method based on zero-sequence voltage proportional differential as described in claim 1, characterized in that: In step three, the difference must satisfy the set parameter range: sensitivity angle Expand on both sides angle.

4. The GCB non-full-phase detection method based on zero-sequence voltage proportional differential as described in claim 1, characterized in that: Assume that the three-phase capacitance to ground at the generator terminals are equal, and the capacitance value of each phase is [value missing]. ; The three-phase-to-ground capacitances on the low-voltage side of the main transformer are equal, and the capacitance value of each phase is [value missing]. ; The equivalent ground resistance of the generator neutral point grounding transformer is The equivalent ground reactance of the neutral point grounding transformer is ; When there is a non-full-phase condition: either a single-phase disconnection or a two-phase disconnection. ； in, ; .

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