CN113078622A - Resistance type direct current magnetic biasing suppression system - Google Patents

Resistance type direct current magnetic biasing suppression system Download PDF

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Publication number
CN113078622A
CN113078622A CN202110451901.2A CN202110451901A CN113078622A CN 113078622 A CN113078622 A CN 113078622A CN 202110451901 A CN202110451901 A CN 202110451901A CN 113078622 A CN113078622 A CN 113078622A
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CN
China
Prior art keywords
current
transformer
thyristor
direct current
current transformer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202110451901.2A
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Chinese (zh)
Inventor
张丽娜
杨运国
王鹏
侯健生
陈梓翰
蔡建军
王千
邱璐
黄俊威
叶泓炜
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Jinhua Electric Power Design Institute Co ltd
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Jinhua Electric Power Design Institute Co ltd
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Publication date
Application filed by Jinhua Electric Power Design Institute Co ltd filed Critical Jinhua Electric Power Design Institute Co ltd
Priority to CN202110451901.2A priority Critical patent/CN113078622A/en
Publication of CN113078622A publication Critical patent/CN113078622A/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/005—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection avoiding undesired transient conditions
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
    • H02H7/042—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers for current transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
    • H02H9/044—Physical layout, materials not provided for elsewhere
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
    • H02H9/045—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage adapted to a particular application and not provided for elsewhere

Abstract

The invention discloses a resistance type direct current magnetic bias suppression system which comprises an adjustable resistor, a quick action switch, a bridge rectifier, a transient voltage trigger unit, a current transformer unit, a thyristor and an adjustable resistor control unit. The bridge rectifier and the thyristor are connected in series and then are connected with the adjustable resistor and the fast acting switch in parallel, one end of the bridge rectifier and the thyristor is connected with a neutral point of the transformer, and the other end of the bridge rectifier and the thyristor are directly grounded. The overvoltage trigger unit is used for triggering the conduction of the thyristor and the closing of the quick action switch. The current transformer unit comprises a Hall current transformer and a Rogowski coil current transformer, wherein the Rogowski coil current transformer is used for detecting neutral point alternating current and transient current and is used as a control signal for switching off the quick action switch; the Hall current transformer is used for detecting the direct current of a neutral point, the direct current is transmitted to the adjustable resistance control unit, and the adjustable resistance control unit adjusts the resistance value of the adjustable resistance to enable the direct current to be smaller than 10A. The device can automatically change the grounding mode of the transformer according to the field requirement.

Description

Resistance type direct current magnetic biasing suppression system
Technical Field
The invention relates to a resistance type direct current magnetic bias suppression system, in particular to a resistance type direct current magnetic bias suppression system capable of automatically changing a grounding mode of a transformer.
Background
The direct current magnetic biasing means that a direct current component appears in the exciting current of the transformer, so that the half-cycle magnetic saturation of the iron core of the transformer is caused, and a series of electromagnetic effects are generated. When direct current enters the transformer, the half-cycle magnetic saturation of the transformer core is caused, the magnetic leakage is increased, and the metal structural part and the oil tank are overheated; the direct current magnetic biasing can also cause the magnetostriction of the iron core to be more serious, so that the vibration of the transformer is aggravated and the noise is increased; meanwhile, due to harmonic distortion, the loss of the transformer is increased, and the efficiency is reduced; when the direct current magnetic bias is serious, the transformer is damaged and the power supply is tripped. Therefore, the direct current magnetic biasing has great potential safety hazard on the safe operation of the power system.
The reason for generating the direct current magnetic bias is mainly unipolar operation or asymmetric operation of a direct current transmission line and solar magnetic storm, and the former is the main reason for generating the direct current magnetic bias in China.
Normally operating a transformer of 110kV or more generally adopts a direct neutral grounding mode, but if the transformer in the region has a larger direct current magnetic bias risk, a capacitive or resistive direct current magnetic bias suppression device is additionally arranged at the neutral point of the transformer.
Because the capacitor has the function of isolating direct current and direct current, the neutral point of the transformer cannot pass through direct current after being connected into the capacitor. The blocking effect of capacitive devices is therefore not affected by the magnitude of the dc current, relative to resistive devices. However, the dc blocking device completely blocks current, and the dc current in the ground will enter the transformer of the adjacent substation, resulting in the dc magnetic bias problem at the new substation.
The resistance type device increases the resistance of a neutral point direct current loop of the transformer, has certain current circulation capacity and can inhibit direct current magnetic bias current of a neutral point, so that the resistance device is more effective in treatment of the direct current magnetic bias of a regional power grid under the condition that the direct current magnetic bias current is not large (not more than 50A). At present, the direct current magnetic biasing problem of a regional power grid is usually treated in a mode of combining capacitance and resistance in engineering.
The resistance current limiting device increases the direct current impedance of a power grid system by connecting a high-power resistor in series at the neutral point of the transformer, thereby inhibiting the direct current magnetic bias current entering the transformer. The current accessed resistance device is generally a pure resistance of 3-5 ohms, and the structure of the device is simpler. However, the zero sequence impedance of the power grid is increased to a great extent by the access of the resistance device, and under the working conditions of short circuit grounding and overvoltage of the system, the accuracy of the relay protection and fault location system can be influenced, and even the protection misoperation can be caused.
Disclosure of Invention
The invention aims to provide a resistance type direct current magnetic bias suppression system aiming at the defects of the prior art, wherein an overvoltage rapid bypass protection loop is arranged outside an original resistor, when the voltage is detected to exceed a set threshold value, the protection loop is rapidly conducted, the direct grounding of a transformer is realized, the circuit topology is restored to the state without a neutral point resistor, and the correct protection action is ensured. Meanwhile, a current transformer is adopted to detect neutral point alternating current and transient current and is used for controlling the disconnection of the quick switch and the mode that the transformer is recovered to be grounded through a resistor, and direct current magnetic bias in a system loop is inhibited, so that the grounding mode of the transformer is automatically changed.
The technical scheme adopted by the invention is as follows:
a resistance type direct current magnetic bias suppression system is characterized in that a direct current magnetic bias suppression device consists of an adjustable resistor, a fast acting switch, a rectification module, a transient voltage trigger unit, a current transformer unit, a thyristor and an adjustable resistor control unit; after the rectifier module and the thyristor are connected in series, the rectifier module and the thyristor are connected in parallel with the adjustable resistor and the quick action switch, one end of the rectifier module is connected with a neutral point of the transformer, and the other end of the rectifier module is directly grounded;
the high-voltage end of the overvoltage trigger unit is connected with the upper end of the thyristor and is used for triggering the thyristor to be conducted;
the current transformer unit comprises a Hall current transformer and a Rogowski coil current transformer, wherein the Rogowski coil current transformer is used for detecting neutral point alternating current and transient current, and the Hall current transformer is used for detecting neutral point direct current;
the Hall current transformer is in communication connection with the adjustable resistor control unit, and the adjustable resistor control unit adjusts the resistance value of the adjustable resistor according to the neutral point direct current detected by the Hall current transformer, so that the direct current is smaller than 10A;
the quick action switch acts according to the detection results of the overvoltage trigger unit and the Rogowski coil current transformer: when the overvoltage signal detected by the overvoltage trigger unit exceeds a voltage threshold value, the fast-acting switch is closed, and when the alternating current and transient current signals detected by the Rogowski coil current transformer are lower than a current threshold value, the fast-acting switch is opened.
Further, a plurality of thyristors are connected in parallel.
Further, the rated current of the thyristor is not lower than 5000A, and the surge current is not lower than 70kA/20 ms.
Furthermore, the resistance range of the adjustable resistor is 1-6 ohms, and the minimum adjusting gear is 0.5 ohms.
Further, the current threshold is 100A.
The invention provides a resistance type direct current magnetic bias suppression system, wherein an overvoltage rapid bypass protection loop is arranged outside an original resistor, when the voltage is detected to exceed a set threshold value, the protection loop is rapidly conducted, the direct grounding of a transformer is realized, the circuit topology is restored to the state without a neutral point resistor, and the correct protection action is ensured. Meanwhile, a current transformer is adopted to detect neutral point alternating current and transient current and is used for controlling the disconnection of the quick switch, and the transformer is restored to be in a resistance grounding mode, so that direct current magnetic bias in a system loop is inhibited. The resistance type direct current magnetic bias suppression system can automatically change the grounding mode of the transformer according to the field requirement.
In addition, the resistance type direct current magnetic bias suppression system adopts the thyristor as a switching element, so that the response time can reach us level, and the response time is greatly faster than the action time of a conventional gap or a switch.
Drawings
The invention is further explained below with reference to the figures and examples;
FIG. 1 is a schematic circuit diagram of a resistive DC bias suppression system according to the present invention;
FIG. 2 is a flow chart of the resistive DC bias suppression system of the present invention;
in the figure, N is a neutral point of the transformer; r1 is an adjustable resistor; k1 is a quick action switch; BR is a bridge rectifier; t1 is a transient voltage trigger unit; th is a thyristor; CT is a current sensor unit; KT is an adjustable resistance control unit.
Detailed Description
The invention provides a resistance type direct current magnetic bias suppression system, which is composed of an adjustable resistor R1, a quick action switch K1, a bridge rectifier BR, a transient voltage trigger unit T1, a current transformer unit CT, a thyristor Th and an adjustable resistor control unit KT as shown in figures 1-2. Wherein:
the head end of the adjustable resistor R1 is connected with the neutral point of the transformer, and the tail end is directly grounded.
The fast acting switch K1 is connected in parallel with an adjustable resistor R1. When the quick bypass switch is closed, the neutral point of the transformer is directly grounded; and conversely, the transformer is grounded through the resistor.
The bridge rectifier BR and the thyristor Th are connected in series and then are connected with the adjustable resistor R1 and the fast-acting switch K1 in parallel to be grounded. The bridge rectifier BR can ensure that the voltage applied to the overvoltage trigger unit and the thyristor is forward voltage; and the high-voltage end of the overvoltage trigger unit T1 is connected with the upper end of the thyristor Th and is used for triggering the conduction of the thyristor Th and the closing of the quick-action switch K1. When a system short-circuit fault, a lightning invasion wave and an operation overvoltage occur, the voltage at two ends of the adjustable resistor R1 is increased sharply, when the voltage is higher than a voltage threshold U0 (set to be 10kV) on the transient voltage trigger unit T1, the transient voltage trigger unit T1 is conducted, meanwhile, the conduction of the thyristor Th and the closing of the fast action switch K1 are triggered, and as the response time of the thyristor Th is us grade, a neutral point is directly grounded through the thyristor Th firstly at us grade time. Since the overvoltage trigger unit T1 triggers the thyristor Th and the fast-acting switch K1 at the same time, K1 is switched on fast while the thyristor Th is turned on, and the action time is less than 20 ms. By means of parallel connection of the thyristor Th and the quick action switch K1, the neutral point of the transformer can be quickly grounded, and the influence of the resistance of the device on relay protection is eliminated.
The protective thyristor Th adopts a high-capacity high-voltage thyristor, the rated current is generally not lower than 5000A, the surge current is not lower than 70kA/20ms, and the time matching of quick switching is met. If necessary, the safety margin can be improved in a mode of connecting a plurality of high-voltage thyristors in series and in parallel.
The current transformer unit CT comprises a rogowski coil current transformer, wherein the rogowski coil current transformer is used for detecting neutral point alternating current and transient current, and a current signal is used for controlling the disconnection of the fast-acting switch K1 through the signal loop 2.
The fast-acting switch K1 in the invention is controlled by the detection results of the transient voltage trigger unit T1 and the current transformer unit CT at the same time, as shown in fig. 2, when the voltage of the transient voltage trigger unit T1 is higher than the threshold, the control K1 is closed, and the adjustable resistor R1 is bypassed; when the overvoltage of the system disappears, the transient current of the neutral point disappears, and the alternating current of the neutral point returns to the normal level, so that the current of the signal loop 2 is set to be less than the current threshold I0(100A) and K1 is turned off, and the neutral point of the transformer returns to the resistance-grounded state, thereby suppressing dc magnetic bias in the system circuit. Therefore, the grounding mode of the transformer can be automatically changed according to the field requirement through the matching of the signal control loops 2 and 3.
In addition, current transformer unit CT still includes a hall current transformer, hall current transformer is used for detecting neutral point direct current, and the electric current gets into adjustable resistance control unit KT through signal circuit 1, and adjustable resistance control unit KT is used for adjusting adjustable resistance R1's gear until direct current is less than 10A, makes the transformer not fragile.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should all embodiments be exhaustive. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.

Claims (5)

1. A resistance type direct current magnetic bias suppression system is characterized in that the direct current magnetic bias suppression device comprises an adjustable resistor, a fast acting switch, a rectification module, a transient voltage trigger unit, a current transformer unit, a thyristor, an adjustable resistor control unit and the like; after the rectifier module and the thyristor are connected in series, the rectifier module and the thyristor are connected in parallel with the adjustable resistor and the quick action switch, one end of the rectifier module is connected with a neutral point of the transformer, and the other end of the rectifier module is directly grounded;
and the high-voltage end of the overvoltage trigger unit is connected with the upper end of the thyristor and is used for triggering the thyristor to be conducted.
The current transformer unit comprises a Hall current transformer and a Rogowski coil current transformer, wherein the Rogowski coil current transformer is used for detecting neutral point alternating current and transient current, and the Hall current transformer is used for detecting neutral point direct current.
The Hall current transformer is in communication connection with the adjustable resistor control unit, and the adjustable resistor control unit adjusts the resistance value of the adjustable resistor according to the neutral point direct current detected by the Hall current transformer, so that the direct current is smaller than 10A;
the quick action switch acts according to the detection results of the overvoltage trigger unit and the Rogowski coil current transformer: when the overvoltage signal detected by the overvoltage trigger unit exceeds a voltage threshold value, the fast-acting switch is closed, and when the alternating current and transient current signals detected by the Rogowski coil current transformer are lower than a current threshold value, the fast-acting switch is opened.
2. The system of claim 1, comprising a plurality of thyristors connected in parallel.
3. A resistive dc magnetic bias suppression system according to claim 1, wherein the rated current of the thyristor is not less than 5000A and the inrush current is not less than 70kA/20 ms.
4. The system of claim 1, wherein the adjustable resistor has a resistance value ranging from 1 to 6 ohms and a minimum adjustment step of 0.5 ohms.
5. The system of claim 1, wherein the current threshold is 100A.
CN202110451901.2A 2021-04-26 2021-04-26 Resistance type direct current magnetic biasing suppression system Pending CN113078622A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110451901.2A CN113078622A (en) 2021-04-26 2021-04-26 Resistance type direct current magnetic biasing suppression system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110451901.2A CN113078622A (en) 2021-04-26 2021-04-26 Resistance type direct current magnetic biasing suppression system

Publications (1)

Publication Number Publication Date
CN113078622A true CN113078622A (en) 2021-07-06

Family

ID=76618740

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110451901.2A Pending CN113078622A (en) 2021-04-26 2021-04-26 Resistance type direct current magnetic biasing suppression system

Country Status (1)

Country Link
CN (1) CN113078622A (en)

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