Differential protection method and system for single-core phase-shifting transformer

Abstract

The invention discloses a differential protection method and system for a single-core phase-shifting transformer, and the method comprises the steps: respectively calculating first balance coefficients of a series winding system side and a load side and a first balance coefficient of an excitation winding through employing the current of the excitation winding as a criterion and employing the current of the series winding system side and the load side; respectively calculating a second balance coefficient of the system side of the series winding and a second balance coefficient of the exciting winding by using the phase modulation gear data, the transformation ratio of the current transformer of the system side of the series winding and the transformation ratio of the current transformer of the exciting winding; correcting the series winding system side current and the excitation winding current by using the first balance coefficient and the second balance coefficient so as to calculate a magnetic balance differential current; correcting the series winding system side current, the series winding load side current and the excitation winding current by using a first balance coefficient so as to calculate an electric balance differential current; when the magnetic balance differential current and the electric balance differential current are both larger than the braking current, differential protection acts, and differential protection of the single-core phase-shifting transformer is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of relay protection of electric power systems, and in particular, relates to a differential protection method and system for a single-core phase-shifting transformer, which is applicable to a hexagonal single-core phase-shifting transformer, a triangular single-core phase-shifting transformer and a SEN-shaped single-core phase-shifting transformer. Background Art

[0002] Regional power grid interconnection can improve power supply reliability, but it also brings many problems, such as uneven power flow distribution and circulating current, which makes some lines overloaded and some lines underutilized, thus affecting the safety of the power system and the absorption of new energy. However, the investment in new transmission lines is large and the cycle is long, and they are also restricted by factors such as land resources and the environment. Power flow controller is one of the main means to solve the above problems.

[0003] In the prior art, there are two main types of power flow controllers used in practical projects, namely, electromagnetic power flow controllers represented by phase shifting transformers (PST) and power electronic power flow controllers represented by unified power flow controllers (UPFC). If the excitation unit and series unit of the PST share a core, this PST is a single-core type; if the excitation unit and series unit of the PST use independent cores, this PST is a double-core type. A PST that does not change the line voltage amplitude after phase shifting is a symmetrical type, otherwise it is an asymmetrical type; a PST that can independently adjust active and reactive power is an independent type.

[0004] In the prior art, a method for differential protection of an excitation transformer for a dual-core asymmetric phase-shifting transformer (CN114362101A) determines whether the conditions for protection action are met based on the corrected differential current after calculating the balance coefficient, but does not take into account the balance coefficient of a single-core phase-shifting transformer. Considering that the series unit and the excitation unit of a single-core phase-shifting transformer share the same iron core, the excitation differential of a single-core is more complicated than that of a dual-core. A method and system for ampere-turn balanced differential protection of a phase-shifting transformer (CN113241727B) provides differential protection for the primary and secondary sides of the series transformer and the secondary side of the excitation transformer by modeling the phase-shifting transformer. This prior art is also for dual-core phase-shifting transformers. A method for implementing differential protection of a phase-shifting transformer (CN105186452B) simply considers the calculation method of the differential current after converting the secondary side to the primary side, without considering that the phase-shifting transformer body will have a gear change when regulating the voltage. With the change of the gear, the differential current will fluctuate, resulting in malfunction of the protection. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a differential protection method and system for a single-core phase-shifting transformer, which realizes the differential protection function of the single-core phase-shifting transformer and the double-core phase-shifting transformer by configuring multiple CTs at different positions and performing specific differential current calculations.

[0006] The present invention adopts the following technical solution.

[0007] The present invention proposes a differential protection method for a single-core phase-shifting transformer, wherein the single-core phase-shifting transformer includes: a hexagonal single-core phase-shifting transformer, a triangular single-core phase-shifting transformer and a SEN-shaped single-core phase-shifting transformer; the single-core phase-shifting transformer includes a three-phase excitation winding and a three-phase series winding that share the same set of iron cores; and includes:

[0008] A set of current transformers is configured on the series winding system side, the series winding load side and the excitation winding respectively to collect the current on the series winding system side, the series winding load side current and the excitation winding current; and obtain the phase adjustment gear data;

[0009] Taking the excitation winding current as a reference, using the series winding system side current and the series winding load side current, respectively calculate the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side, and the first balance coefficient of the excitation winding; using the phase adjustment gear data, the current transformer ratio of the series winding system side, and the current transformer ratio of the excitation winding, respectively calculate the second balance coefficient of the series winding system side and the second balance coefficient of the excitation winding;

[0010] Using the first balance coefficient and the second balance coefficient of the series winding system side and the first balance coefficient and the second balance coefficient of the excitation winding, respectively correct the current of the series winding system side and the excitation winding current, and calculate the magnetic balance differential current with the corrected value of the current of the series winding system side, the excitation winding current, and the corrected value of the excitation winding current;

[0011] The first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding are used to respectively correct the series winding system side current, the series winding load side current and the excitation winding current, and the electric balance differential current is calculated using the corrected value of the series winding system side current, the corrected value of the series winding load side current and the excitation winding current;

[0012] When both the magnetic balance differential current and the electric balance differential current are greater than the braking current, the differential protection operates.

[0013] When both the magnetic balance differential current and the electric balance differential current are not greater than the braking current, the phase adjustment gear is monitored, and when the phase-shifting transformer is in the phase adjustment gear adjustment state, the differential protection is locked.

[0014] Collect the series winding system side current, series winding load side current, excitation winding current and phase adjustment gear data, including:

[0015] The collected current on the series winding system side includes the primary rated current, secondary rated current, primary actual current and secondary actual current on the series winding system side;

[0016] The collected current on the load side of the series winding includes the primary rated current, the secondary rated current, the primary actual current and the secondary actual current on the load side of the series winding;

[0017] The collected excitation winding current includes: the excitation winding current before the phase modulation gear is adjusted and the excitation winding current after the phase modulation gear is adjusted; wherein the excitation winding current includes the primary rated current, secondary rated current, primary actual current and secondary actual current of the excitation winding.

[0018] Taking the excitation winding current as a reference, using the series winding system side current and the series winding load side current, respectively calculating the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding, including:

[0019] Taking the secondary rated current of the excitation winding as the reference, using the secondary rated current of the series winding system side and the secondary rated current of the series winding load side, the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding are calculated respectively, and the following relationships are satisfied respectively:

[0020]

[0021] In the formula, K ph.M is the first balance coefficient of the series winding system side, K ph.L is the first balance coefficient of the series winding load side, K ph.H is the first balance coefficient of the excitation winding, I 2e.H is the secondary rated current of the excitation winding, I 2e.M is the secondary rated current on the series winding system side, I 2e.L is the secondary rated current on the load side of the series winding.

[0022] The phase modulation gear data includes: the turns ratio of the phase modulation middle gear, the turns percentage of each phase modulation gear, the current phase modulation gear and the phase modulation middle gear;

[0023] The second balance coefficient of the series winding system side and the second balance coefficient of the excitation winding are calculated by using the phase modulation gear data, the current transformer ratio of the series winding system side, and the current transformer ratio of the excitation winding, respectively, and the following relationships are satisfied:

[0024]

[0025] In the formula, is the second balance coefficient on the series winding system side, is the second balance coefficient of the excitation winding, P n is the turns ratio of the intermediate gear of phase modulation, R n is the percentage of turns per gear in phase modulation, D n is the current phase adjustment position, O n For the middle gear of phase modulation, K M , K H They are the current transformer ratio on the series winding system side and the current transformer ratio of the excitation winding respectively.

[0026] The first balance coefficient and the second balance coefficient of the series winding system side and the first balance coefficient and the second balance coefficient of the excitation winding are used to correct the current of the series winding system side and the excitation winding current respectively, and the magnetic balance differential current is calculated by the corrected value of the current of the series winding system side and the corrected value of the excitation winding current, including:

[0027] The first balance coefficient and the second balance coefficient of the series winding system are used to correct the primary actual current of the series winding system to satisfy the following relationship:

[0028]

[0029] In the formula, is the actual primary current on the series winding system side, is a first correction value of an actual primary current on the series winding system side based on a first balance coefficient and a second balance coefficient on the series winding system side;

[0030] The actual primary current of the excitation winding is corrected by using the first balance coefficient and the second balance coefficient of the excitation winding to satisfy the following relationship:

[0031]

[0032] In the formula, is the actual primary current of the excitation winding, is a first correction value of the primary actual current of the excitation winding based on the first balance coefficient and the second balance coefficient of the excitation winding;

[0033] The magnetic balance differential current is calculated using the first correction value of the series winding system side current, the excitation winding current, and the first correction value of the excitation winding current, satisfying the following relationship:

[0034]

[0035] In the formula, I dzA_M ,I dzB_M ,IdzC_M is the magnetic balance differential current.

[0036] The first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding are used to respectively correct the series winding system side current, the series winding load side current and the excitation winding current, and the electric balance differential current is calculated using the corrected value of the series winding system side current, the corrected value of the series winding load side current and the corrected value of the excitation winding current, including:

[0037] The first balance coefficient of the series winding system is used to correct the primary actual current of the series winding system to satisfy the following relationship:

[0038]

[0039] In the formula, is the actual primary current on the series winding system side, A second correction value of the primary actual current on the series winding system side based on the first balance coefficient on the series winding system side;

[0040] The first balance coefficient on the load side of the series winding is used to correct the primary actual current on the load side of the series winding to satisfy the following relationship:

[0041]

[0042] In the formula, is the actual primary current on the load side of the series winding, is a correction value of the primary actual current on the load side of the series winding based on the first balance coefficient on the load side of the series winding;

[0043] The first balance coefficient of the excitation winding is used to correct the actual primary current of the excitation winding to satisfy the following relationship:

[0044]

[0045] In the formula, is the actual primary current of the excitation winding, A second correction value of the primary actual current of the excitation winding based on the first balance coefficient of the excitation winding;

[0046] The electric balance differential current is calculated using the second correction value of the current on the system side of the series winding, the correction value of the primary actual current on the load side of the series winding, the excitation winding current, and the second correction value of the excitation winding current, satisfying the following relationship:

[0047]

[0048] In the formula, I dzA_E,I dzB_M ,I dzC_M is the electrically balanced differential current.

[0049] The first balance coefficient and / or the second balance coefficient of the excitation winding is used to correct the actual primary current of the excitation winding after the phase adjustment gear is adjusted.

[0050] The braking current satisfies the following relationship:

[0051]

[0052] In the formula, I zd is the braking current; It is the phase current with the largest amplitude on the system side of the series winding, the load side of the series winding, and the field winding; For the exception In addition, it is the sum of the currents in the series winding system side, the series winding load side and the excitation winding.

[0053] The present invention also proposes a differential protection system for a single-core phase-shifting transformer, comprising:

[0054] Acquisition module, balance coefficient calculation module, magnetic balance differential current calculation module, electric balance differential current calculation module, differential action locking module;

[0055] The acquisition module is used to configure a set of current transformers on the series winding system side, the series winding load side and the excitation winding, respectively, to collect the series winding system side current, the series winding load side current and the excitation winding current; and to obtain the phase modulation gear data;

[0056] The balance coefficient calculation module is used to calculate the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side, and the first balance coefficient of the excitation winding respectively by using the current of the series winding system side and the current of the series winding load side based on the excitation winding current; and calculate the second balance coefficient of the series winding system side and the second balance coefficient of the excitation winding respectively by using the phase adjustment gear data, the current transformer ratio of the series winding system side, and the current transformer ratio of the excitation winding;

[0057] A magnetic balance differential current calculation module is used to use the first balance coefficient and the second balance coefficient of the series winding system side and the first balance coefficient and the second balance coefficient of the excitation winding to respectively correct the current on the series winding system side and the excitation winding current, and calculate the magnetic balance differential current with the corrected value of the current on the series winding system side, the excitation winding current, and the corrected value of the excitation winding current;

[0058] An electric balanced differential current calculation module, used to respectively correct the series winding system side current, the series winding load side current and the excitation winding current using the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding, and calculate the electric balanced differential current using the corrected value of the series winding system side current, the corrected value of the series winding load side current and the excitation winding current;

[0059] The differential action locking module is used to activate the differential protection when both the magnetic balance differential current and the electric balance differential current are greater than the braking current; when both the magnetic balance differential current and the electric balance differential current are not greater than the braking current, the phase adjustment gear is monitored, and when the phase-shifting transformer is in the phase adjustment gear adjustment state, the differential protection is locked.

[0060] The beneficial effects of the present invention are that, compared with the prior art, at least the differential protection method for a single-core phase-shifting transformer proposed in the present invention realizes the differential protection function of a hexagonal single-core phase-shifting transformer, a triangular single-core phase-shifting transformer and a SEN-shaped single-core phase-shifting transformer, and adopts the method of the excitation side as the reference side, thereby solving the problem of malfunction of protection caused by unbalanced differential current when the magnetic balance differential is in the middle gear when the phase adjustment gear is in the middle gear; dynamically monitors the "gear adjustment state" of the main body, and automatically adjusts the magnetic balance differential characteristics during the "gear adjustment" period, thereby avoiding the influence of the main body on the magnetic balance differential due to the lag in sending the gear information during the gear adjustment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 1 is a primary structure and CT configuration diagram of a hexagonal single-core phase-shifting transformer in an embodiment of the present invention;

[0062] Figure 2 It is a primary structure and CT configuration diagram of a triangular structure single-core phase-shifting transformer in an embodiment of the present invention;

[0063] Figure 3 1 is a primary structure and CT configuration diagram of a single-core phase-shifting transformer of a SEN-shaped structure in an embodiment of the present invention;

[0064] Figure 4 It is a flow chart of a differential protection configuration scheme of a phase-shifting protection device proposed by the present invention. DETAILED DESCRIPTION

[0065] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0066] The primary structure of the hexagonal single-core phase-shifting transformer is as follows: Figure 1 As shown, the three-phase excitation winding A E , B E , C E And three-phase series winding A S , B S , C S It forms a hexagonal structure, and the excitation winding and the series winding share the same set of iron cores, so it is called a single-core structure.

[0067] Figure 1 In the figure, the first current transformer CT1 includes: three-phase current transformers CT1a, CT1b, and CT1c on the series winding system side; the second current transformer CT2 includes: three-phase current transformers CT2a, CT2b, and CT2c on the series winding load side; the third current transformer CT3 includes: three-phase current transformers CT3a, CT3b, and CT3c of the excitation winding; Ula, Ulb, and Ulc respectively represent the three-phase voltages on the series winding load side; Usa, Usb, and Usc respectively represent the three-phase voltages on the series winding system side; PT1 and PT2 respectively represent the voltage transformers on the series winding system side and the load side.

[0068] The primary structure of a triangular structure single-core phase-shifting transformer is as follows: Figure 2 As shown, the three-phase excitation windings a3, b3, and c3 form a triangle structure, the three-phase series windings a1+a2, b1+b2, and c1+c2 form a triangle structure, and the excitation winding and the series winding share the same set of iron cores, so it is called a single-core structure.

[0069] Figure 2 In the figure, the first current transformer CT1 includes: three-phase current transformers CT1a, CT1b, and CT1c on the series winding system side; the second current transformer CT2 includes: three-phase current transformers CT2a, CT2b, and CT2c on the series winding load side; the third current transformer CT3 includes: three-phase current transformers CT3a, CT3b, and CT3c of the excitation winding; Ula, Ulb, and Ulc respectively represent the three-phase voltages on the series winding load side; Usa, Usb, and Usc respectively represent the three-phase voltages on the series winding system side; PT1 and PT2 respectively represent the voltage transformers on the series winding system side and the load side.

[0070] The primary structure of the SEN-shaped single-core phase-shifting transformer is as follows: Figure 3As shown, the three-phase excitation windings A, B, and C form a Y-shaped structure connected to the series winding system side, and the three-phase series windings a1+b3+c2, a2+b1+c3, and a3+b2+c1 form a Y-shaped structure. The series windings of each phase are connected in series between the system side and the load side; and the excitation winding and the series winding share the same set of iron cores, so it is called a single-core structure.

[0071] Figure 3 In the figure, the first current transformer CT1 includes: three-phase current transformers CT1a, CT1b, and CT1c on the series winding system side; the second current transformer CT2 includes: three-phase current transformers CT2a, CT2b, and CT2c on the series winding load side; the third current transformer CT3 includes: three-phase current transformers CT3a, CT3b, and CT3c of the excitation winding; Ula, Ulb, and Ulc respectively represent the three-phase voltages on the series winding load side; Usa, Usb, and Usc respectively represent the three-phase voltages on the series winding system side; PT1 and PT2 respectively represent the voltage transformers on the series winding system side and the load side.

[0072] The present invention proposes a differential protection method for a single-core phase-shifting transformer. The single-core phase-shifting transformer includes a series winding and an excitation winding. The method flow is as follows: Figure 4 As shown, including:

[0073] Step 1: configure a set of current transformers on the series winding system side, the series winding load side and the excitation winding respectively, collect the series winding system side current, the series winding load side current and the excitation winding current, and obtain the phase modulation gear data at the same time.

[0074] Specifically, in a single-core phase-shifting transformer, a group of current transformers are configured on the series winding system side, the series winding load side and the excitation winding, respectively collecting the series winding system side current, the series winding load side current and the excitation winding current, wherein the excitation winding current includes: the excitation winding current before the phase modulation gear is adjusted and the excitation winding current after the phase modulation gear is adjusted.

[0075] According to the law of magnetic induction, when current flows through the excitation winding, current will be induced on the series winding through the shared iron core. This current cannot be ignored when calculating the magnetic balance differential current. Therefore, when configuring CT, a set of CTs is configured on the series winding system side, the series winding load side, and the excitation winding. The CT ratio can be set according to the on-site usage.

[0076] Specifically, the collected current on the series winding system side includes but is not limited to: the primary rated current, secondary rated current, primary actual current and secondary actual current on the series winding system side; the collected current on the series winding load side includes but is not limited to: the primary rated current, secondary rated current, primary actual current and secondary actual current on the series winding load side; the collected excitation winding current includes but is not limited to: the primary rated current, secondary rated current, primary actual current and secondary actual current of the excitation winding.

[0077] Step 2, taking the excitation winding current as a reference, using the series winding system side current and the series winding load side current, respectively calculate the first balance coefficient of the series winding system side and the first balance coefficient of the series winding load side; using the phase modulation gear data, the current transformer ratio of the series winding system side, the current transformer ratio of the series winding load side and the current transformer ratio of the excitation winding, respectively calculate the second balance coefficient of the series winding system side and the second balance coefficient of the series winding load side.

[0078] There is a tap in the structure of the series winding to adjust the percentage of the series winding connected to the system. At the same time, this tap also has the function of connecting the series winding in the forward and reverse directions, which can realize the lead-lag adjustment of the voltage angle. Therefore, the balance coefficient on the system side of the series winding and the balance coefficient on the load side of the series winding are not only related to the CT ratio configuration, but also to the phase adjustment gear. Therefore, it is necessary to obtain a balance coefficient that can integrate the above two influencing factors for the subsequent magnetic balance differential current calculation.

[0079] Specifically, step 2 includes:

[0080] Step 2.1, taking the secondary rated current of the excitation winding as a reference, using the secondary rated current of the series winding system side and the secondary rated current of the series winding load side, respectively calculate the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding;

[0081] In a non-limiting preferred embodiment, the collected secondary rated current of the excitation winding, the secondary rated current of the series winding system side, and the secondary rated current of the series winding load side are used to calculate the balance coefficient of the series winding system side and the balance coefficient of the series winding load side respectively; those skilled in the art can choose to calculate the balance coefficient by presenting currents with different balance coefficients due to different CT ratio settings according to various requirements such as actual engineering conditions and current measurement accuracy.

[0082] Among them, the rated current of the excitation winding includes: the primary rated current I of the excitation winding 1e.H and the secondary rated current I of the field winding 2e.H; The rated current of the series winding includes: the primary rated current I on the system side of the series winding 1e.M and the secondary rated current I on the series winding system side 2e.M , the primary rated current I of the series winding load side 1e.L and the secondary rated current I of the load side of the series winding 2e.L .

[0083] The first balance coefficient K of the series winding system is calculated using the following relationship: ph.M , the first balance coefficient K on the load side of the series winding ph.L , the first balance coefficient K of the excitation winding ph.H :

[0084]

[0085] Step 2.2, using the phase modulation gear data, the current transformer ratio of the series winding system side, and the current transformer ratio of the excitation winding, respectively calculate the second balance coefficient of the series winding system side and the second balance coefficient of the excitation winding;

[0086] In a non-limiting preferred embodiment, the phase modulation gear data includes but is not limited to: the turns ratio of the phase modulation intermediate gear, the turns percentage of each phase modulation gear, the current phase modulation gear and the phase modulation intermediate gear.

[0087] The second balance coefficient of the series winding system is calculated using the following relationship: Second balance factor of the series winding load side Second balance factor of the field winding

[0088]

[0089] In the formula,

[0090] is the second balance coefficient on the series winding system side;

[0091] is the second balance coefficient on the load side of the series winding;

[0092] is the second balance coefficient of the field winding;

[0093] P n is the turns ratio of the intermediate gear of phase modulation;

[0094] R n is the percentage of turns in each gear of phase modulation;

[0095] D n is the current phase adjustment gear;

[0096] On It is the middle gear of phase modulation;

[0097] K M , K L , K H They are the current transformer ratio on the series winding system side, the current transformer ratio on the series winding load side, and the current transformer ratio of the excitation winding.

[0098] The first balance coefficient proposed in the present invention characterizes the configuration characteristics of the current transformer ratio, and is used to calculate the electrically balanced differential current in real time; the second balance coefficient proposed in the present invention characterizes the primary structural characteristics of the single-core phase-shifting transformer. In the subsequent magnetically balanced differential current calculation, the magnetically balanced differential current can follow the changes in the phase adjustment gear in real time based on the second balance coefficient.

[0099] Step 3, using the first balance coefficient and the second balance coefficient of the series winding system side and the first balance coefficient and the second balance coefficient of the excitation winding, respectively correct the current on the series winding system side and the excitation winding current, and calculate the magnetic balance differential current with the corrected value of the current on the series winding system side, the excitation winding current, and the corrected value of the excitation winding current.

[0100] Specifically, step 3 includes:

[0101] Step 3.1, using the first balance coefficient and the second balance coefficient of the series winding system side, correct the primary actual current on the series winding system side to satisfy the following relationship:

[0102]

[0103] In the formula, is the actual primary current on the series winding system side, It is a first correction value of the primary actual current on the series winding system side based on the first balance coefficient and the second balance coefficient on the series winding system side.

[0104] Step 3.2, using the first balance coefficient and the second balance coefficient of the excitation winding, correct the actual primary current of the excitation winding to satisfy the following relationship:

[0105]

[0106] In the formula, is the actual primary current of the excitation winding, It is a first correction value of the primary actual current of the excitation winding based on the first balance coefficient and the second balance coefficient of the excitation winding.

[0107] In a non-limiting preferred embodiment, the actual primary current of the excitation winding after the phase adjustment is corrected by using the first balance coefficient and the second balance coefficient of the excitation winding.

[0108] Step 3.3, calculating the magnetic balance differential current with the first correction value of the series winding system side current, the excitation winding current and the first correction value of the excitation winding current, satisfying the following relationship:

[0109]

[0110] In the formula, I dzA_M ,I dzB_M ,I dzC_M is the magnetic balance differential current.

[0111] Among them, the corrected value of the current on the series winding system side and the excitation winding current are taken as the forward current, and the corrected value of the excitation winding current is taken as the reverse current. The calculated magnetic balance differential current can follow the change of the phase modulation gear, thereby taking into account the influence of the primary structure of the single-core phase-shifting transformer on the magnetic balance.

[0112] In the embodiment, Figure 1 As shown, the first current transformer CT1 configured on the series winding system side and the third current transformer CT3 configured on the excitation winding constitute a magnetic balance differential. Taking phase A as an example, the A-phase CT3a of the third current transformer is used to collect the A-phase current of the excitation winding, the C-phase reverse current of the excitation winding after the phase adjustment gear is collected by the C-phase CT3c of the third current transformer, and the A-phase current on the series winding system side is collected by the A-phase CT1a of the first current transformer and corrected by the balance coefficient. In the calculation method of the magnetic balance differential current applicable to the single-core phase-shifting transformer proposed in the present invention, by first converting the current on the series winding system side by the balance coefficient, the calculation result of the magnetic balance differential current can follow the phase adjustment gear change in real time, which is helpful for engineering application. When the phase adjustment gear is in the middle gear of the magnetic balance differential, the excitation winding current is always 0. By using the secondary rated current of the excitation winding as the reference, the problem of protection malfunction caused by unbalanced differential current when the phase adjustment gear is in the middle gear of the magnetic balance differential is solved.

[0113] Step 4, use the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding to respectively correct the series winding system side current, the series winding load side current and the excitation winding current, and calculate the electrically balanced differential current with the corrected value of the series winding system side current, the corrected value of the series winding load side current and the corrected value of the excitation winding current.

[0114] Specifically, step 4 includes:

[0115] Step 4.1, using the first balance coefficient of the series winding system side, correct the primary actual current on the series winding system side to satisfy the following relationship:

[0116]

[0117] In the formula, is the actual primary current on the series winding system side, It is a second correction value of the primary actual current on the series winding system side based on the first balance coefficient on the series winding system side.

[0118] Step 4.2, using the first balance coefficient on the load side of the series winding, correct the actual primary current on the load side of the series winding to satisfy the following relationship:

[0119]

[0120] In the formula, is the actual primary current on the load side of the series winding, is a correction value of the primary actual current on the load side of the series winding based on the first balance coefficient on the load side of the series winding;

[0121] Step 4.3, using the first balance coefficient of the excitation winding, correct the actual primary current of the excitation winding to satisfy the following relationship:

[0122]

[0123] In the formula, is the actual primary current of the excitation winding, It is a second correction value of the primary actual current of the excitation winding based on the first balance coefficient of the excitation winding.

[0124] In a non-limiting preferred embodiment, the first balance coefficient of the excitation winding is used to correct the actual primary current of the excitation winding after the phase adjustment gear is adjusted.

[0125] Step 4.4, calculate the electric balance differential current using the second correction value of the current on the system side of the series winding, the correction value of the primary actual current on the load side of the series winding, the excitation winding current, and the second correction value of the excitation winding current, to satisfy the following relationship:

[0126]

[0127] In the formula, I dzA_E ,I dzB_M ,I dzC_M is the electrically balanced differential current.

[0128] Among them, the electric balance differential current is calculated by taking the corrected value of the current on the system side of the series winding, the corrected value of the current on the load side of the series winding, and the excitation winding current as the forward current, and taking the corrected value of the excitation winding current as the reverse current.

[0129] In the embodiment, Figure 1 As shown, the first current transformer CT1 configured on the series winding system side, the second current transformer CT2 configured on the series winding load side, and the third current transformer CT3 configured on the excitation winding constitute an electric balance differential. Taking phase A as an example, the first current transformer A phase CT1a is used to collect the A phase current on the series winding system side, the second current transformer A phase CT2a is used to collect the A phase current on the series winding load side, and the third current transformer B phase CT3b and C phase CT3c are used to collect the difference between the B phase current and the C phase current of the excitation winding. In the calculation method of the electric balance differential current applicable to the single-core phase-shifting transformer proposed in the present invention, the electric balance is not achieved by phase, but the current difference between the other two phases of the excitation winding is used as the current of the corresponding phase, which is helpful for engineering applications. The primary structure of the single-core phase-shifting transformer is complex, and a specific differential current calculation method needs to be considered according to different structures to form a magnetic balance differential and an electric balance differential that are compatible with the primary structure. In the electrically balanced differential current, there is no need to consider the influence of the balance coefficient or the following of the phase adjustment gear caused by the particularity of the primary structure of the phase-shifting transformer body.

[0130] Based on the improvement of the magnetic balance differential current calculation method and the electric balance differential current calculation method, the excitation winding side is used as the reference side. When the magnetic balance differential protection is in the middle gear, there will be no protection malfunction caused by the imbalance of the differential current when the phase adjustment gear is in the middle gear. Moreover, since the calculation result of the magnetic balance differential current can follow the change of the phase adjustment gear in real time, the magnetic balance differential current is automatically adjusted during the gear adjustment period, avoiding the error of the magnetic balance differential caused by the lag in sending the gear adjustment information, thereby improving the reliability of the differential protection action.

[0131] Step 5, when the magnetic balance differential current and the electric balance differential current are greater than the braking current, the differential protection is activated; when the magnetic balance differential current and the electric balance differential current are not greater than the braking current, the phase adjustment position is monitored, and when the phase-shifting transformer is in the phase adjustment position adjustment state, the differential protection is locked.

[0132] Specifically, the braking current satisfies the following relationship:

[0133]

[0134] In the formula,

[0135] I zd is the braking current;

[0136] It is the phase current with the largest amplitude on the system side of the series winding, the load side of the series winding, and the field winding;

[0137] For the exception In addition, it is the sum of the currents in the series winding system side, the series winding load side and the excitation winding.

[0138] For special operating conditions, consider whether to lock the differential protection. For example, when the phase-shifting transformer is running in the middle gear, it means that the phase-shifting transformer is not put into operation; during the phase-shifting gear adjustment process, there will be a lag in sending the gear information of the phase-shifting transformer to the protection device. When the protection device monitors that the phase-shifting transformer body is in the phase-shifting gear adjustment state, the differential protection is locked to avoid the phenomenon of incorrect differential current calculation caused by the lag in sending the gear information during the phase-shifting gear adjustment process, thereby ensuring that the magnetic balance differential will not malfunction.

[0139] The present invention also proposes a differential protection system for a single-core phase-shifting transformer, comprising:

[0140] Acquisition module, balance coefficient calculation module, magnetic balance differential current calculation module, electric balance differential current calculation module, differential action locking module;

[0141] The acquisition module is used to configure a set of current transformers on the series winding system side, the series winding load side and the excitation winding, respectively, to collect the series winding system side current, the series winding load side current and the excitation winding current; and to obtain the phase modulation gear data;

[0142] The balance coefficient calculation module is used to calculate the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side, and the first balance coefficient of the excitation winding respectively by using the current of the series winding system side and the current of the series winding load side based on the excitation winding current; and calculate the second balance coefficient of the series winding system side and the second balance coefficient of the excitation winding respectively by using the phase adjustment gear data, the current transformer ratio of the series winding system side, and the current transformer ratio of the excitation winding;

[0143] A magnetic balance differential current calculation module is used to use the first balance coefficient and the second balance coefficient of the series winding system side and the first balance coefficient and the second balance coefficient of the excitation winding to respectively correct the current on the series winding system side and the excitation winding current, and calculate the magnetic balance differential current with the corrected value of the current on the series winding system side, the excitation winding current, and the corrected value of the excitation winding current;

[0144] An electric balanced differential current calculation module, used to respectively correct the series winding system side current, the series winding load side current and the excitation winding current using the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding, and calculate the electric balanced differential current using the corrected value of the series winding system side current, the corrected value of the series winding load side current and the excitation winding current;

[0145] The differential action locking module is used to activate the differential protection when both the magnetic balance differential current and the electric balance differential current are greater than the braking current; when both the magnetic balance differential current and the electric balance differential current are not greater than the braking current, the phase adjustment gear is monitored, and when the phase-shifting transformer is in the phase adjustment gear adjustment state, the differential protection is locked.

[0146] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0147] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0148] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0149] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0150] Various aspects of the present disclosure are described herein with reference to the flowcharts and / or block diagrams of the methods, devices (systems) and computer program products according to the embodiments of the present disclosure. It should be understood that each box in the flowchart and / or block diagram and the combination of each box in the flowchart and / or block diagram can be implemented by computer-readable program instructions.

[0151] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, thereby producing a machine, so that when these instructions are executed by the processor of the computer or other programmable data processing device, a device that implements the functions / actions specified in one or more boxes in the flowchart and / or block diagram is generated. These computer-readable program instructions can also be stored in a computer-readable storage medium, and these instructions cause the computer, programmable data processing device, and / or other equipment to work in a specific manner, so that the computer-readable medium storing the instructions includes a manufactured product, which includes instructions for implementing various aspects of the functions / actions specified in one or more boxes in the flowchart and / or block diagram.

[0152] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device so that a series of operating steps are performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to implement the functions / actions specified in one or more boxes in the flowchart and / or block diagram.

[0153] The flow chart and block diagram in the accompanying drawings show the possible architecture, function and operation of the system, method and computer program product according to multiple embodiments disclosed in the present invention. In this regard, each square box in the flow chart or block diagram can represent a part of a module, program segment or instruction, and a part of the module, program segment or instruction includes one or more executable instructions for realizing the specified logical function. In some implementations as replacements, the functions marked in the square box can also occur in a sequence different from that marked in the accompanying drawings. For example, two continuous square boxes can actually be executed substantially in parallel, and they can sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each square box in the block diagram and / or flow chart, and the combination of the square boxes in the block diagram and / or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A differential protection method for a single-core phase-shifting transformer, the single-core phase-shifting transformer comprising: Hexagonal structure single-core phase-shifting transformer, triangle structure single-core phase-shifting transformer and SEN structure single-core phase-shifting transformer; The single-core phase-shifting transformer comprises a three-phase excitation winding and a three-phase series winding which share the same set of iron cores; and is characterized in that it comprises: A set of current transformers is configured on the series winding system side, the series winding load side and the excitation winding respectively to collect the current on the series winding system side, the series winding load side current and the excitation winding current; and obtain the phase adjustment gear data; Taking the excitation winding current as a reference, using the series winding system side current and the series winding load side current, respectively calculate the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side, and the first balance coefficient of the excitation winding; using the phase adjustment gear data, the current transformer ratio of the series winding system side, and the current transformer ratio of the excitation winding, respectively calculate the second balance coefficient of the series winding system side and the second balance coefficient of the excitation winding; Using the first balance coefficient and the second balance coefficient of the series winding system side and the first balance coefficient and the second balance coefficient of the excitation winding, respectively correct the current of the series winding system side and the excitation winding current, and calculate the magnetic balance differential current with the corrected value of the current of the series winding system side, the excitation winding current, and the corrected value of the excitation winding current; The first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding are used to respectively correct the series winding system side current, the series winding load side current and the excitation winding current, and the electric balance differential current is calculated using the corrected value of the series winding system side current, the corrected value of the series winding load side current and the excitation winding current; When both the magnetic balance differential current and the electric balance differential current are greater than the braking current, the differential protection operates.

2. The differential protection method for a single-core phase-shifting transformer according to claim 1, characterized in that: When both the magnetic balance differential current and the electric balance differential current are not greater than the braking current, the phase adjustment gear is monitored, and when the phase-shifting transformer is in the phase adjustment gear adjustment state, the differential protection is locked.

3. The differential protection method for a single-core phase-shifting transformer according to claim 1, characterized in that: Collect the series winding system side current, series winding load side current, excitation winding current and phase adjustment gear data, including: The collected current on the series winding system side includes the primary rated current, secondary rated current, primary actual current and secondary actual current on the series winding system side; The collected current on the load side of the series winding includes the primary rated current, the secondary rated current, the primary actual current and the secondary actual current on the load side of the series winding; The collected excitation winding current includes: the excitation winding current before the phase modulation gear is adjusted and the excitation winding current after the phase modulation gear is adjusted; wherein the excitation winding current includes the primary rated current, secondary rated current, primary actual current and secondary actual current of the excitation winding.

4. The differential protection method for a single-core phase-shifting transformer according to claim 3 is characterized in that: Taking the excitation winding current as a reference, using the series winding system side current and the series winding load side current, respectively calculating the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding, including: Taking the secondary rated current of the excitation winding as the reference, using the secondary rated current of the series winding system side and the secondary rated current of the series winding load side, the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding are calculated respectively, and the following relationships are satisfied respectively: In the formula, K ph.M is the first balance coefficient of the series winding system side, K ph.L is the first balance coefficient of the series winding load side, K ph.H is the first balance coefficient of the excitation winding, I 2e.H is the secondary rated current of the excitation winding, I 2e.M is the secondary rated current on the series winding system side, I 2e.L is the secondary rated current on the load side of the series winding.

5. The differential protection method for a single-core phase-shifting transformer according to claim 4, characterized in that: The phase modulation gear data includes: the turns ratio of the phase modulation middle gear, the turns percentage of each phase modulation gear, the current phase modulation gear and the phase modulation middle gear; The second balance coefficient of the series winding system side and the second balance coefficient of the excitation winding are calculated by using the phase modulation gear data, the current transformer ratio of the series winding system side, and the current transformer ratio of the excitation winding, respectively, and the following relationships are satisfied: In the formula, is the second balance coefficient on the series winding system side, is the second balance coefficient of the excitation winding, P n is the turns ratio of the intermediate gear of phase modulation, R n is the percentage of turns per gear in phase modulation, D n is the current phase adjustment position, O n For the middle gear of phase modulation, K M , K H They are the current transformer ratio on the series winding system side and the current transformer ratio of the excitation winding respectively.

6. The differential protection method for a single-core phase-shifting transformer according to claim 5, characterized in that: The first balance coefficient and the second balance coefficient of the series winding system side and the first balance coefficient and the second balance coefficient of the excitation winding are used to correct the current of the series winding system side and the excitation winding current respectively, and the magnetic balance differential current is calculated by the corrected value of the current of the series winding system side and the corrected value of the excitation winding current, including: The first balance coefficient and the second balance coefficient of the series winding system are used to correct the primary actual current of the series winding system to satisfy the following relationship: In the formula, is the actual primary current on the series winding system side, is a first correction value of an actual primary current on the series winding system side based on a first balance coefficient and a second balance coefficient on the series winding system side; The actual primary current of the excitation winding is corrected by using the first balance coefficient and the second balance coefficient of the excitation winding to satisfy the following relationship: In the formula, is the actual primary current of the excitation winding, is a first correction value of the primary actual current of the excitation winding based on the first balance coefficient and the second balance coefficient of the excitation winding; The magnetic balance differential current is calculated using the first correction value of the series winding system side current, the excitation winding current, and the first correction value of the excitation winding current, satisfying the following relationship: In the formula, I dzA_M ,I dzB_M ,I dzC_M is the magnetic balance differential current.

7. The differential protection method for a single-core phase-shifting transformer according to claim 6, characterized in that: The first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding are used to respectively correct the series winding system side current, the series winding load side current and the excitation winding current, and the electric balance differential current is calculated using the corrected value of the series winding system side current, the corrected value of the series winding load side current and the corrected value of the excitation winding current, including: The first balance coefficient of the series winding system is used to correct the primary actual current of the series winding system to satisfy the following relationship: In the formula, is the actual primary current on the series winding system side, A second correction value of the primary actual current on the series winding system side based on the first balance coefficient on the series winding system side; The first balance coefficient on the load side of the series winding is used to correct the primary actual current on the load side of the series winding to satisfy the following relationship: In the formula, is the actual primary current on the load side of the series winding, is a correction value of the primary actual current on the load side of the series winding based on the first balance coefficient on the load side of the series winding; The first balance coefficient of the excitation winding is used to correct the actual primary current of the excitation winding to satisfy the following relationship: In the formula, is the actual primary current of the excitation winding, A second correction value of the primary actual current of the excitation winding based on the first balance coefficient of the excitation winding; The electric balance differential current is calculated using the second correction value of the current on the system side of the series winding, the correction value of the primary actual current on the load side of the series winding, the excitation winding current, and the second correction value of the excitation winding current, satisfying the following relationship: In the formula, I dzA_E ,I dzB_M ,I dzC_M is the electrically balanced differential current.

8. The differential protection method for a single-core phase-shifting transformer according to claim 7, characterized in that: The first balance coefficient and / or the second balance coefficient of the excitation winding is used to correct the actual primary current of the excitation winding after the phase adjustment gear is adjusted.

9. The differential protection method for a single-core phase-shifting transformer according to claim 1, characterized in that: The braking current satisfies the following relationship: In the formula, I zd is the braking current; It is the phase current with the largest amplitude on the system side of the series winding, the load side of the series winding, and the field winding; For the exception In addition, it is the sum of the currents in the series winding system side, the series winding load side and the excitation winding.

10. A differential protection system for a single-core phase-shifting transformer, the single-core phase-shifting transformer comprising a three-phase excitation winding and a three-phase series winding sharing the same set of iron cores; characterized in that: include: Acquisition module, balance coefficient calculation module, magnetic balance differential current calculation module, electric balance differential current calculation module, differential action locking module; The acquisition module is used to configure a set of current transformers on the series winding system side, the series winding load side and the excitation winding, respectively, to collect the series winding system side current, the series winding load side current and the excitation winding current; and to obtain the phase modulation gear data; The balance coefficient calculation module is used to calculate the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side, and the first balance coefficient of the excitation winding respectively by using the current of the series winding system side and the current of the series winding load side based on the excitation winding current; and calculate the second balance coefficient of the series winding system side and the second balance coefficient of the excitation winding respectively by using the phase adjustment gear data, the current transformer ratio of the series winding system side, and the current transformer ratio of the excitation winding; A magnetic balance differential current calculation module is used to use the first balance coefficient and the second balance coefficient of the series winding system side and the first balance coefficient and the second balance coefficient of the excitation winding to respectively correct the current on the series winding system side and the excitation winding current, and calculate the magnetic balance differential current with the corrected value of the current on the series winding system side, the excitation winding current, and the corrected value of the excitation winding current; An electric balanced differential current calculation module, used to respectively correct the series winding system side current, the series winding load side current and the excitation winding current using the first balance coefficient of the series winding system side, the first balance coefficient of the series winding load side and the first balance coefficient of the excitation winding, and calculate the electric balanced differential current using the corrected value of the series winding system side current, the corrected value of the series winding load side current and the excitation winding current; The differential action locking module is used to activate the differential protection when both the magnetic balance differential current and the electric balance differential current are greater than the braking current; when both the magnetic balance differential current and the electric balance differential current are not greater than the braking current, the phase adjustment gear is monitored, and when the phase-shifting transformer is in the phase adjustment gear adjustment state, the differential protection is locked.

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