Zero-sequence overcurrent protection checking method based on primary simulation platform of power grid

Abstract

The invention discloses a zero-sequence overcurrent protection checking method based on a power grid primary simulation platform, and the method comprises the steps: obtaining regional power grid power flow information and grid parameters through a dispatching automation system, and building the power grid primary simulation platform; s2, calculating system equivalent impedance at a bus corresponding to a fault point in a small mode through a power grid primary simulation platform; s3, according to the system equivalent impedance at the bus corresponding to the fault point and the power grid operation mode, obtaining the zero-sequence current of the related fault point; s4, calculating a zero-sequence overcurrent II section fixed value and a zero-sequence overcurrent III section fixed value according to the zero-sequence current of the related fault point; and S5, calling a zero-sequence overcurrent II section constant value and a zero-sequence overcurrent III section constant value in an actual protection device, and comparing the zero-sequence overcurrent II section constant value and the zero-sequence overcurrent III section constant value with the calculated zero-sequence overcurrent II section constant value and the zero-sequence overcurrent III section constant value to complete zero-sequence overcurrent protection checking. And the accuracy of zero-sequence over-current protection checking and the operation reliability of the relay protection device are improved.

Description

Technical Field

[0001] The present application relates to the technical field of power system simulation, and in particular to a zero-sequence overcurrent protection verification method based on a power grid primary simulation platform. Background Art

[0002] The existing zero-sequence overcurrent protection verification method uses manual calculation of system equivalent impedance to calculate the zero-sequence current of the fault point according to a specific power grid operation mode, which is labor-intensive and error-prone, and the calculation result is very limited by the operation mode of the power grid, resulting in large calculation errors. The present invention uses a dispatching automation system to establish a power grid primary simulation platform, the model data is derived from the actual power grid parameters, and the system impedance closest to the real power grid is calculated through the fluctuating bus voltage and current, thereby improving the accuracy of the zero-sequence fault current. At the same time, the expert library model is used to obtain the fixed values ​​of the zero-sequence overcurrent protection sections II and III, and the fixed values ​​are compared with the fixed values ​​in the actual protection device, thereby improving the accuracy and ensuring the safe and stable operation of the power grid. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention provides a zero-sequence overcurrent protection verification method based on a power grid primary simulation platform, which solves the problem that the traditional power grid uses a manual method to calculate the equivalent impedance, resulting in a large workload, prone to errors, and large errors in the calculation results.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a zero-sequence overcurrent protection verification method based on a power grid primary simulation platform, comprising:

[0005] S1. The dispatching automation system obtains regional power grid flow information and grid parameters, and establishes a power grid primary simulation platform;

[0006] S2. Calculate the equivalent impedance of the system at the bus corresponding to the fault point under the small mode through the primary simulation platform of the power grid;

[0007] S3. Obtain the zero-sequence current of the relevant fault point according to the system equivalent impedance at the bus corresponding to the fault point and the grid operation mode;

[0008] S4. Calculate the zero-sequence overcurrent II-stage constant and the zero-sequence overcurrent III-stage constant according to the zero-sequence current of the relevant fault point;

[0009] S5. Retrieve the zero-sequence overcurrent stage II and zero-sequence overcurrent stage III setting values ​​in the actual protection device, and compare them with the calculated zero-sequence overcurrent stage II and zero-sequence overcurrent stage III setting values ​​to complete the zero-sequence overcurrent protection verification.

[0010] Further: the regional power grid flow information and grid parameters in S1 include the regional power system generator power, load power, 500kV substation grid power, line parameters and transformer parameters.

[0011] Further: S2 includes:

[0012] S201, the dispatching automation system obtains the output power of each generator and the load power of each node corresponding to the annual minimum load of the power grid;

[0013] S202, according to the output power of each generator and the load power of each node corresponding to the annual minimum load of the power grid, obtain the normal distribution samples of each generator and the normal distribution samples of the load power of each node when the annual minimum load of the power grid is obtained;

[0014] S203, substituting the normal distribution samples of each generator and the normal distribution samples of each node load power at the annual minimum load of the power grid into the primary simulation platform of the power grid;

[0015] S204, using a Monte Carlo probability power flow calculation method through a power grid primary simulation platform to obtain a bus voltage sample set and a load current sample set corresponding to the fault point under normal distribution;

[0016] S205. Calculate the equivalent impedance of the system at the bus corresponding to the fault point in a small mode according to the bus voltage sample set and the load current sample set corresponding to the fault point under normal distribution.

[0017] Further: S3 includes:

[0018] S301, generating a short-circuit current calculation sequence network diagram according to the system equivalent impedance at the bus corresponding to the fault point and the grid operation mode;

[0019] S302, calculating the zero-sequence current value when single-phase grounding occurs according to the short-circuit current calculation sequence network diagram and the characteristics of the single-phase grounding fault network at the end of the line;

[0020] S303, calculating the zero-sequence current value when two phases are grounded at the end of the line according to the short-circuit current calculation sequence network diagram and the fault network characteristics when two phases are grounded at the end of the line;

[0021] S304. Take the smaller one of the zero-sequence current value when a single phase is grounded and the zero-sequence current value when two phases are grounded at the end of the line as the zero-sequence current of the fault point.

[0022] Further: In S4, the method for calculating the zero-sequence overcurrent II stage constant includes three methods:

[0023] Method 1: Calculate the zero-sequence overcurrent II stage constant based on the zero-sequence current at the relevant fault point and on the premise of ensuring sufficient sensitivity when the fault occurs at the end of the line;

[0024] Method 2: Calculate the zero-sequence overcurrent II section constant according to the coordination relationship between the zero-sequence overcurrent II section of the current line and the adjacent line;

[0025] Method 3: Calculate the zero-sequence overcurrent II constant based on the 220kV transformer on the opposite side of the line.

[0026] Further: in S4, the zero-sequence overcurrent II stage setting also includes a zero-sequence overcurrent II stage time setting, and the zero-sequence overcurrent II stage time setting is used to coordinate with the zero-sequence overcurrent II stage setting of the adjacent line.

[0027] Further: In S4, the method for calculating the zero-sequence overcurrent III stage constant includes:

[0028] S411. Calculate the zero-sequence III current according to the zero-sequence current of the relevant fault point and on the premise of ensuring sufficient sensitivity when the end of the line is faulty;

[0029] S412, according to the constraint of zero-sequence III-stage current and the zero-sequence current flowing through the ground fault on the 220 kV side of the transformer, calculate the zero-sequence overcurrent III-stage constant;

[0030] S413, converting the zero-sequence III segment current and the zero-sequence overcurrent III segment current into nominal values, and dividing them by the zero-sequence current transformer ratio at the same time, to obtain the zero-sequence overcurrent III segment constant.

[0031] Further: in S4, the zero-sequence overcurrent stage III setting also includes a zero-sequence overcurrent stage III time setting, and the zero-sequence overcurrent stage III time setting is used to ensure the selectivity of the zero-sequence overcurrent protection during a fault.

[0032] The beneficial effects of the present invention are:

[0033] A dispatching automation system is used to establish a primary simulation platform for the power grid. The model data is derived from the actual power grid parameters, and the system impedance closest to the real power grid is calculated through the fluctuating bus voltage and current, which improves the accuracy of the zero-sequence fault current. At the same time, the expert library model is used to obtain the set values ​​of the zero-sequence overcurrent protection stages II and III, which are compared with the set values ​​in the actual protection device, thereby improving the accuracy and ensuring the safe and stable operation of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of the zero-sequence overcurrent protection verification method based on the primary power grid simulation platform. DETAILED DESCRIPTION

[0035] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0036] like Figure 1 As shown, in one embodiment of the present invention, a zero-sequence overcurrent protection verification method based on a power grid primary simulation platform is provided, comprising:

[0037] S1. The dispatching automation system obtains regional power grid flow information and grid parameters, and establishes a power grid primary simulation platform;

[0038] S2. Calculate the equivalent impedance of the system at the bus corresponding to the fault point under the small mode through the primary simulation platform of the power grid;

[0039] S3. Obtain the zero-sequence current of the relevant fault point according to the system equivalent impedance at the bus corresponding to the fault point and the grid operation mode;

[0040] S4. Calculate the zero-sequence overcurrent II-stage constant and the zero-sequence overcurrent III-stage constant according to the zero-sequence current of the relevant fault point;

[0041] S5. Retrieve the zero-sequence overcurrent stage II and zero-sequence overcurrent stage III setting values ​​in the actual protection device, and compare them with the calculated zero-sequence overcurrent stage II and zero-sequence overcurrent stage III setting values ​​to complete the zero-sequence overcurrent protection verification.

[0042] Specifically, the regional power grid flow information and grid parameters in S1 include the regional power system generator power, load power, 500kV substation off-grid power, line parameters and transformer parameters.

[0043] S1 includes:

[0044] S11. Obtain the power flow information of a certain regional power grid through the power system unified dispatching automation system, and obtain the generator power, load power and 500kV substation power of the regional power system;

[0045] S12, obtaining the grid parameters of a regional power grid through the power system unified dispatching automation system, and obtaining all generator impedances, line impedance parameters and transformer short-circuit impedance parameters of the regional power system;

[0046] S13. Establish a primary power grid simulation platform based on the regional power system generator power, load power, 500kV substation grid power and all generator impedances, line impedance parameters and transformer short-circuit impedance parameters of the regional power system.

[0047] Specifically, S2 includes:

[0048] S201, the dispatching automation system obtains the output power of each generator and the load power of each node corresponding to the annual minimum load of the power grid;

[0049] S202, according to the output power of each generator and the load power of each node corresponding to the annual minimum load of the power grid, obtain the normal distribution sample P of each generator at the annual minimum load of the power grid G (P i ) and the normal distribution sample L(d i );

[0050] S203, substituting the normal distribution samples of each generator and the normal distribution samples of each node load power at the annual minimum load of the power grid into the primary simulation platform of the power grid;

[0051] S204, using a Monte Carlo probability power flow calculation method through a power grid primary simulation platform to obtain a bus voltage sample set U and a load current sample set I corresponding to the fault point under normal distribution;

[0052] S205. Calculate the equivalent impedance Z of the system at the bus corresponding to the fault point under the small mode according to the bus voltage sample set and load current sample set corresponding to the fault point under the normal distribution. S-ym , whose expression is:

[0053]

[0054] Among them, E is the system voltage at the fault point, I is the load current of the 220kV fault point during normal operation, U is the bus voltage at the fault point, and Z S-ym is the equivalent impedance of the system at the busbar corresponding to the fault point under the small mode;

[0055] Optionally, after S205, Z S-ym Convert from a nominal value to a per-unit value.

[0056] Specifically, S3 includes:

[0057] S301, generating a short-circuit current calculation sequence network diagram according to the system equivalent impedance at the bus corresponding to the fault point and the grid operation mode;

[0058] Among them, the short-circuit current calculation sequence network diagram includes positive sequence network, negative sequence network and zero sequence network;

[0059] The positive sequence network includes the system equivalent impedance, transformer and line positive sequence impedance, and the positive sequence comprehensive impedance X 1∑ =X S-by +X T1 +X L1 ; The negative sequence network includes the negative sequence impedance of the transformer and the line, and its negative sequence comprehensive impedance X 2∑ =X S-by +X T2 +X L2 ; The zero-sequence network includes the zero-sequence impedance of the transformer and the line, and its zero-sequence comprehensive impedance X 0∑ =XT0 +X L0 ;

[0060] Among them, X S-by Z S-ym The corresponding system impedance, X T1 is the transformer positive sequence impedance, X L1 is the positive sequence impedance from the fault point to the busbar; X T2 is the transformer negative sequence impedance, X L2 is the negative sequence impedance from the fault point to the bus; X T0 is the transformer zero-sequence impedance, X L0 is the zero-sequence impedance from the fault point to the busbar;

[0061] S302, calculate the zero-sequence current value 3I when single-phase grounding occurs according to the short-circuit current calculation sequence network diagram and the characteristics of the single-phase grounding fault network at the end of the line (i.e., the positive sequence, negative sequence and zero sequence networks are connected in series). 0 , whose expression is:

[0062]

[0063] S303, according to the short-circuit current calculation sequence network diagram and the fault network characteristics when two phases are grounded at the end of the line (that is, the negative sequence and zero sequence networks are connected in parallel and then connected to the positive sequence network), calculate the zero sequence current value 3I when two phases are grounded at the end of the line 0 ′, its expression is:

[0064]

[0065] S304, take the smaller one of the zero-sequence current value when a single phase is grounded and the zero-sequence current value when two phases are grounded at the end of the line. 0min =min(3I 0 ,3I 0 ′), as the zero-sequence current of the fault point.

[0066] Specifically, according to the setting calculation principle, in S4, the method for calculating the zero-sequence overcurrent II stage setting value includes three methods:

[0067] Method 1: Calculate the zero-sequence overcurrent II stage constant based on the zero-sequence current at the relevant fault point and on the premise of ensuring sufficient sensitivity when the fault occurs at the end of the line;

[0068] Its expression is:

[0069] I ∏ =3I 0min / K sen

[0070] Among them, I 0min is the zero-sequence current value of the line end fault under the small mode, through Ksen is the sensitivity when the fault occurs at the end of this line;

[0071] In order to improve the sensitivity of zero-sequence overcurrent protection, it is necessary to find a minimum fault zero-sequence current. At the same time, the fault type and operation mode will cause the magnitude of the zero-sequence current to change, so it is necessary to obtain the minimum zero-sequence current I 0min .

[0072] Method 2: According to the coordination relationship between the zero-sequence overcurrent section II of this line and the adjacent line, the zero-sequence overcurrent section II constant is calculated, and its expression is:

[0073] I Π =K k K F I′ DZ ∏

[0074] Among them, K k is the reliability coefficient, K F is the maximum branching coefficient, I′ DZ∏ Set the value for the zero-sequence II section of the adjacent line;

[0075] Method 3: If there is a 220kV transformer on the opposite side of the line, the zero-sequence current I can flow through the line through the ground fault on the 220kV side of the transformer. 0T Calculate the zero-sequence II current, the expression is:

[0076] I ∏ =K k ′·I 0T

[0077] Among them, K k ′ is the reliability coefficient, I 0T It is the zero sequence current flowing through the line due to the ground fault on the 220kV side of the transformer;

[0078] Optionally, the calculated zero-sequence overcurrent II stage constant is converted into a nominal value and divided by the zero-sequence CT ratio to obtain the zero-sequence overcurrent II stage reference constant I DZII , including:

[0079] S4001. Convert the calculated zero-sequence overcurrent II segment constant value into a nominal value, and obtain the zero-sequence II segment current nominal value I II ;

[0080] in, V B is the reference voltage of the corresponding level, S B is the base capacity;

[0081] S4002, the nominal value of the zero-sequence II current divided by the zero-sequence current transformer ratio n CT , and obtain the zero-sequence overcurrent II section reference value IDZII .

[0082] In particular, in S4, the zero-sequence overcurrent II stage setting also includes the zero-sequence overcurrent II stage time setting, which is used to coordinate with the zero-sequence overcurrent II stage setting of the adjacent line, and its expression is:

[0083] t ∏ =t lin∏ +Δt

[0084] Among them, t ∏ is the zero sequence overcurrent II period, t lin∏ is the constant value of the zero-sequence overcurrent II section of the adjacent line, and Δt is the time interval.

[0085] Specifically, according to the setting calculation principle, in S4, the method for calculating the zero-sequence overcurrent III stage setting value includes:

[0086] S411. Based on the zero-sequence current of the relevant fault point and under the premise of ensuring sufficient sensitivity when the end of the line is faulty, calculate the zero-sequence III current standard value I III , whose expression is:

[0087] I III =3I 0min / K s ' en

[0088] S412, according to the constraint of zero-sequence III-stage current and the zero-sequence current flowing through the ground fault on the 220 kV side of the transformer, calculate the zero-sequence overcurrent III-stage constant;

[0089] In this embodiment, the constraint of the zero-sequence III current is that the primary value of the zero-sequence current does not exceed 300A;

[0090] S413, converting the zero-sequence III segment current and the zero-sequence overcurrent III segment current into nominal values, and dividing them by the zero-sequence current transformer ratio at the same time to obtain the zero-sequence overcurrent III segment constant value;

[0091] Specifically, S413 includes:

[0092] S4131. Multiply the zero-sequence III current per unit value by the current reference value of the corresponding voltage level to obtain the zero-sequence III current nominal value, which is expressed as:

[0093] I III =I III-by I B

[0094] Among them, I III-by is the zero-sequence III current per unit value, I III It is the nominal value of zero-sequence III current;

[0095] S4132, divide the nominal value of the zero-sequence III current by the zero-sequence current transformer ratio n CT , and obtain the zero-sequence overcurrent III constant I DZIII .

[0096] In particular, in S4, the zero-sequence overcurrent III stage setting also includes the zero-sequence overcurrent III stage time setting, which is used to ensure the selectivity of the zero-sequence overcurrent protection during a fault, specifically including:

[0097] In order to prevent the fault from leapfrogging to the main transformer protection, the zero-sequence overcurrent III time setting value t III Should be less than 2.2 seconds;

[0098] In order to ensure selectivity during faults, the zero-sequence overcurrent III time setting value t III =t linII +Δt;

[0099] Among them, t linII It is the time constant of zero-sequence overcurrent II stage of adjacent lines.

[0100] In S5, dedicated software is used to retrieve the zero-sequence overcurrent II and zero-sequence overcurrent III constants in the actual protection device, and compare them with the constants in steps 4 and 5. If the constants obtained in steps 4 and 5 are within the upper and lower preset ranges, the system considers that the zero-sequence overcurrent II and III constants are correct; otherwise, they are judged to be incorrect and require manual confirmation.

[0101] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A zero-sequence overcurrent protection verification method based on a power grid primary simulation platform is characterized in that: include: S1. The dispatching automation system obtains regional power grid flow information and grid parameters, and establishes a power grid primary simulation platform; S2. Calculate the equivalent impedance of the system at the bus corresponding to the fault point under the small mode through the primary simulation platform of the power grid; S3. Obtain the zero-sequence current of the relevant fault point according to the system equivalent impedance at the bus corresponding to the fault point and the grid operation mode; S4. Calculate the zero-sequence overcurrent II-stage constant and the zero-sequence overcurrent III-stage constant according to the zero-sequence current of the relevant fault point; S5. Retrieve the zero-sequence overcurrent stage II and zero-sequence overcurrent stage III setting values ​​in the actual protection device, and compare them with the calculated zero-sequence overcurrent stage II and zero-sequence overcurrent stage III setting values ​​to complete the zero-sequence overcurrent protection verification.

2. The zero-sequence overcurrent protection verification method based on the power grid primary simulation platform according to claim 1 is characterized in that: The regional power grid flow information and grid parameters in S1 include the regional power system generator power, load power, 500kV substation grid power, line parameters and transformer parameters.

3. The zero-sequence overcurrent protection verification method based on the power grid primary simulation platform according to claim 1 is characterized in that S2 include: S201, the dispatching automation system obtains the output power of each generator and the load power of each node corresponding to the annual minimum load of the power grid; S202, according to the output power of each generator and the load power of each node corresponding to the annual minimum load of the power grid, obtain the normal distribution samples of each generator and the normal distribution samples of the load power of each node when the annual minimum load of the power grid is obtained; S203, substituting the normal distribution samples of each generator and the normal distribution samples of each node load power at the annual minimum load of the power grid into the primary simulation platform of the power grid; S204, using a Monte Carlo probability power flow calculation method through a power grid primary simulation platform to obtain a bus voltage sample set and a load current sample set corresponding to the fault point under normal distribution; S205. Calculate the equivalent impedance of the system at the bus corresponding to the fault point in a small mode according to the bus voltage sample set and the load current sample set corresponding to the fault point under normal distribution.

4. The zero-sequence overcurrent protection verification method based on the power grid primary simulation platform according to claim 1 is characterized in that S3 include: S301, generating a short-circuit current calculation sequence network diagram according to the system equivalent impedance at the bus corresponding to the fault point and the grid operation mode; S302, calculating the zero-sequence current value when single-phase grounding occurs according to the short-circuit current calculation sequence network diagram and the characteristics of the single-phase grounding fault network at the end of the line; S303, calculating the zero-sequence current value when two phases are grounded at the end of the line according to the short-circuit current calculation sequence network diagram and the fault network characteristics when two phases are grounded at the end of the line; S304. Take the smaller one of the zero-sequence current value when a single phase is grounded and the zero-sequence current value when two phases are grounded at the end of the line as the zero-sequence current of the fault point.

5. The zero-sequence overcurrent protection verification method based on the power grid primary simulation platform according to claim 1 is characterized in that: In S4, there are three ways to calculate the zero-sequence overcurrent II setting: Method 1: Calculate the zero-sequence overcurrent II stage constant based on the zero-sequence current at the relevant fault point and on the premise of ensuring sufficient sensitivity when the fault occurs at the end of the line; Method 2: Calculate the zero-sequence overcurrent II section constant according to the coordination relationship between the zero-sequence overcurrent II section of the current line and the adjacent line; Method 3: Calculate the zero-sequence overcurrent II constant based on the 220kV transformer on the opposite side of the line.

6. The zero-sequence overcurrent protection verification method based on the power grid primary simulation platform according to claim 1 is characterized in that: In S4, the zero-sequence overcurrent II stage setting also includes the zero-sequence overcurrent II stage time setting, and the zero-sequence overcurrent II stage time setting is used to coordinate with the zero-sequence overcurrent II stage setting of the adjacent line.

7. The zero-sequence overcurrent protection verification method based on the power grid primary simulation platform according to claim 1 is characterized in that: In S4, the method for calculating the zero-sequence overcurrent stage III constant includes: S401, calculating the zero-sequence III section current according to the zero-sequence current of the relevant fault point and under the premise of ensuring sufficient sensitivity when the end of the line fails; S402, calculating the zero-sequence overcurrent segment III constant value according to the constraint of the zero-sequence segment III current and the zero-sequence current flowing through the ground fault on the 220 kV side of the transformer; S403, converting the zero-sequence III segment current and the zero-sequence overcurrent III segment current into nominal values, and dividing them by the zero-sequence current transformer ratio at the same time, to obtain the zero-sequence overcurrent III segment constant.

8. The zero-sequence overcurrent protection verification method based on the power grid primary simulation platform according to claim 1 is characterized in that: In S4, the zero-sequence overcurrent stage III setting also includes the zero-sequence overcurrent stage III time setting, and the zero-sequence overcurrent stage III time setting is used to ensure the selectivity of the zero-sequence overcurrent protection during a fault.

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