CN115236508A

CN115236508A - AC/DC universal medium-voltage dry-type load and work switching method

Info

Publication number: CN115236508A
Application number: CN202210860280.8A
Authority: CN
Inventors: 胡聪; 孙曦东; 俞希学; 陈晓波
Original assignee: 703th Research Institute of CSIC Wuxi Branch
Current assignee: 703th Research Institute of CSIC Wuxi Branch
Priority date: 2022-07-21
Filing date: 2022-07-21
Publication date: 2022-10-25

Abstract

The invention relates to an alternating current and direct current universal medium-voltage dry load and a work switching method. The system comprises a dry type load unit group, wherein the dry type load unit group comprises a plurality of dry type load units which are connected in a three-phase star shape, and the dry type load units are configured to be in an alternating current working mode or a direct current working mode, wherein when the dry type load units are configured to be in the alternating current working mode, the load connecting ends of the dry type load units are in adaptive electric connection with three-phase alternating current buses in the alternating current working mode, so that the dry type load units are configured to be medium-voltage alternating current dry type loads; when the dry type load unit is configured to be in a direct current working mode, the load connecting end of the dry type load unit is in adaptive electrical connection with the positive bus in the direct current working mode, so that the dry type load unit is configured to be used as a medium-voltage direct current dry type load. The invention can meet the test requirements of medium-voltage direct current and medium-voltage alternating current, improves the utilization rate of the load, reduces the test cost, and is safe and reliable.

Description

AC/DC universal medium-voltage dry-type load and work switching method

Technical Field

The invention relates to a load and work switching method, in particular to an alternating current and direct current universal medium-voltage dry-type load and a work switching method.

Background

With the development of modern science and technology, direct current is widely applied to various industrial fields, and a high-power medium-voltage direct current power generation technology is rapidly developed. Therefore, it is important to detect the quality and safety of the medium-voltage dc power supply based on the high-power dc power generation technology.

The high-power direct-current power generation technology is generally based on a medium-voltage direct-current generator set, and equipment for testing the performance of the medium-voltage direct-current generator set at home and abroad is mainly a dry direct-current load, namely the medium-voltage direct-current dry load. The dry-type direct current load is widely used for performance test of the medium-voltage direct current generator set due to the outstanding characteristics of large power density, high load regulation precision and the like.

For performance testing of medium voltage ac generator sets, it is generally necessary to utilize medium voltage ac dry loads. It is well known to those skilled in the art that the medium voltage ac dry load and the medium voltage dc dry load cannot be commonly used due to the difference in load structure, voltage class and insulation requirements between the existing medium voltage ac dry load and the existing medium voltage dc dry load. The differences in load structure and insulation requirements between the medium voltage ac dry load and the medium voltage dc dry load will be specifically described below.

Difference in load structure: in order to ensure three-phase balance, a load loop is uniformly distributed between three phases, and the medium-voltage alternating-current dry load generally adopts a star-shaped or triangular connection method; and the load loop of the medium-voltage direct-current dry-type load is directly arranged between the positive bus and the negative bus.

Taking an AC 10.5kV medium-voltage alternating-current dry load as an example, the situation of the difference of the load structure is specifically explained; specifically, the method of directly applying direct-current voltage by taking two phases of three phases of the alternating-current load as the positive bus and the negative bus not only wastes resistance wires in a residual-phase load loop, but also easily causes local overheating of the load loop, and affects safe and reliable operation of the load. Meanwhile, the original voltage between two used phases is AC 10.5kV, but when the voltage is applied to DC 4kV, the voltage is reduced by over 60 percent, the resistance value of a load loop is increased by 100 percent, and the heating power of the load loop is seriously influenced; the whole load power is one ninth of the original load power.

Difference in insulation requirements: due to the difference in electrical clearance requirements of different electrical systems and voltage levels, it is difficult to ensure the rationality of the electrical clearance under different electrical systems and voltage levels. Meanwhile, the dry load loop control generally adopts a contactor as a loop breaking device, but the medium-voltage alternating current and direct current contactor cannot be directly used in common due to large differences in key technical parameters such as structure, voltage-resistant grade, arc extinguishing capability, manufacturing process, materials and the like.

In summary, under the existing conditions, the common use of the medium-voltage ac dry load and the medium-voltage dc dry load cannot be realized; the medium-voltage alternating current dry-type load and the medium-voltage direct current dry-type load are used for respectively carrying out performance tests on the medium-voltage alternating current generator set and the medium-voltage direct current generator set, so that the load utilization rate is low, the test cost is high, and the requirement of actual performance tests is difficult to meet.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide an alternating current and direct current universal medium-voltage dry type load and a work switching method, which can meet the test requirements of medium-voltage direct current and medium-voltage alternating current, improve the utilization rate of the load, reduce the test cost and are safe and reliable.

According to the technical scheme provided by the invention, the alternating current-direct current universal medium-voltage dry load comprises a dry load unit group, wherein the dry load unit group comprises a plurality of dry load units connected in a three-phase star manner, neutral points of all the dry load units are connected with each other, and the neutral points of all the dry load units are connected with each other and then used as a negative bus in a direct current working mode;

configuring a dry type load unit to be in an alternating current working mode or a direct current working mode, wherein when the dry type load unit is configured to be in the alternating current working mode, a load connecting end of the dry type load unit is in adaptive electrical connection with a three-phase alternating current bus in the alternating current working mode, so that the dry type load unit is configured to be used as a medium-voltage alternating current dry type load; when the dry type load unit is configured to be in a direct current working mode, the load connecting end of the dry type load unit is in adaptive electric connection with the positive bus in the direct current working mode, so that the dry type load unit is configured to be used as a medium-voltage direct current dry type load;

during operation, the dry load units in the dry load unit group can only be configured in the same operating mode.

For any dry load unit, the system comprises an alternating current medium voltage contactor and a direct current medium voltage contactor which are matched with the dry load unit, wherein,

the dry type load unit is in adaptive connection with the wire outlet end of the main contact of the alternating current medium voltage contactor through the working mode switching connection mechanism or is in adaptive connection with the wire outlet end of the main contact of the direct current medium voltage contactor, the wire inlet end of the main contact of the alternating current medium voltage contactor is in adaptive electric connection with the three-phase alternating current bus, and the wire inlet end of the main contact of the direct current medium voltage contactor is in adaptive electric connection with the positive bus;

when the dry type load unit is configured to be in an alternating current working mode, controlling a main contact of the alternating current medium voltage contactor to be closed and a main contact of the direct current medium voltage contactor to be opened, so that a load connecting end of the dry type load unit is electrically connected with the three-phase alternating current bus through the working mode switching connecting mechanism and the main contact of the alternating current medium voltage contactor in a closed state;

and when the dry type load unit is configured to be in a direct current working mode, the main contact of the alternating current medium voltage contactor is controlled to be opened and the main contact of the direct current medium voltage contactor is controlled to be closed, so that the load connection end of the dry type load unit is electrically connected with the positive bus through the working mode switching connection mechanism and the main contact of the direct current medium voltage contactor in a closed state.

The working mode switching connecting mechanism comprises a busbar side connecting unit which is in adaptive connection with a main contact of the alternating current medium voltage contactor, a resistance side connecting unit which is in adaptive connection with a load connecting end of the dry type load unit, a direct current side connecting body which is used for connecting a main contact outlet end of the direct current medium voltage contactor and a switching connecting unit which is used for switching the connecting state, wherein,

when the resistance side connecting unit is correspondingly and electrically connected with the busbar side connecting unit through the switching connecting unit, the dry type load unit can be electrically connected with the three-phase alternating current bus; when the resistance side connecting unit is correspondingly and electrically connected with the direct current side connecting body through the switching connecting unit, the dry type load unit can be electrically connected with the positive bus.

The busbar side connecting unit comprises three parallel busbar side connecting copper bars which are respectively and correspondingly electrically connected with the main contact of the alternating-current medium-voltage contactor;

the resistance side connecting unit comprises three parallel resistance side connecting copper bars, the three resistance side connecting copper bars are in one-to-one positive correspondence with the three busbar side connecting copper bars in the busbar side connecting unit, and the three resistance side connecting copper bars are correspondingly and electrically connected with the load connecting end of the dry type load unit;

the switching connection unit comprises at least three switching connection copper bars, the three switching connection copper bars are utilized to enable the resistance side connection copper bars to be correspondingly connected with the busbar side connection copper bars one by one, or the three switching connection copper bars are utilized to enable the resistance side connection copper bars to be electrically connected with the direct current side connector.

The neutral points of all dry load units in the dry load unit group are connected, and a voltage sensor for measuring the neutral point-to-ground voltage state of the dry load units is configured;

and configuring load working state monitoring based on the neutral point-to-ground voltage through the neutral point-to-ground voltage measured by the voltage sensor, wherein the configured load working state monitoring comprises abnormal switching monitoring in an alternating current working mode, load health state monitoring in the alternating current working mode and/or ground insulation state monitoring in a direct current working mode.

And when the switching abnormity is monitored in the alternating current working mode, the neutral point deviation alarm is carried out when the neutral point deviation of the medium-voltage alternating current dry load is determined according to the neutral point to ground voltage.

When monitoring a load fault in an alternating-current working mode, determining the amplitude of a neutral point-to-ground voltage and the phase of the neutral point-to-ground voltage by using a voltage sensor;

when a dry load unit is configured as a medium voltage alternating current dry load, a corresponding neutral-to-ground voltage vector difference before and after the current dry load unit is connected to an alternating current bus is determined, and the health state of the medium voltage alternating current dry load is determined according to the determined neutral-to-ground voltage vector difference.

Also comprises a contactor closing control circuit for controlling the corresponding opening and closing states of the alternating current medium voltage contactor and the direct current medium voltage contactor, wherein,

when the contactor closing control circuit is utilized to control the AC medium-voltage contactor to be in a closed state, the DC medium-voltage contactor is locked to be in an open state, or when the contactor closing control circuit is utilized to control the DC medium-voltage contactor to be in a closed state, the AC medium-voltage contactor is locked to be in an open state.

The system is characterized by further comprising a quick fuse group for fusing protection, wherein the quick fuse group comprises a plurality of quick fuses of required current levels, and the quick fuses in the quick fuse group are used for fusing protection of dry-type load units configured in an alternating current working mode or a direct current working mode.

A method for switching operation of a DC/AC universal medium voltage dry load comprises a dry load unit group for forming the DC/AC universal medium voltage dry load and an operation switching controller for controlling the operation switching,

and configuring the alternating current and direct current universal dry type load to be in the state by using a working switching controller so as to switch and control the working state of the alternating current and direct current universal medium-voltage dry type load.

The invention has the advantages that: the dry type load unit group comprises a plurality of dry type load units connected in a three-phase star type, wherein neutral points of all the dry type load units are connected with each other, and the neutral points of all the dry type load units are connected with each other and then used as a negative pole bus in a direct current working mode;

the dry-type load units in the dry-type load unit group can work in an alternating current working mode and a direct current working mode, the load power in the direct current working mode can reach two thirds of that in the alternating current working mode, and the utilization rate of the dry-type load unit group can be improved. On withstand voltage and insulating problem, each return circuit maximum voltage does not all exceed insulating material's tolerance ability under the direct current mode, possesses fine security performance to can satisfy the test demand of middling pressure direct current, can satisfy the test demand of middling pressure alternating current again, improve the utilization ratio of load, reduce test cost, safe and reliable.

Drawings

Fig. 1 is a schematic diagram of an embodiment of the ac/dc universal dry medium voltage load according to the present invention.

Fig. 2 is a schematic diagram of the secondary side of the closing control circuit of the contactor according to the present invention.

Fig. 3 is a schematic diagram of the secondary side self-locking protection of the closing control circuit of the contactor of the invention.

Fig. 4 is a schematic view of an embodiment of the operation mode switching connection mechanism of the present invention.

Description of reference numerals: 1-busbar side connection first copper bar, 2-busbar side connection second copper bar, 3-busbar side connection third copper bar, 4-resistance side connection first copper bar, 5-resistance side connection second copper bar, 6-resistance side connection third copper bar, 7-direct current side connection copper bar, 8-switching connection first copper bar, 9-switching connection second copper bar and 10-switching connection third copper bar.

Detailed Description

The invention is further illustrated by the following specific figures and examples.

In order to meet the test requirements of medium-voltage direct current and medium-voltage alternating current, improve the utilization rate of a load and reduce the test cost, the alternating-current and direct-current universal medium-voltage dry load provided by the invention comprises the following components in percentage by weight: the system comprises a dry-type load unit group, wherein the dry-type load unit group comprises a plurality of dry-type load units which are connected in a three-phase star shape, neutral points of all the dry-type load units are connected with one another, and the neutral points of all the dry-type load units are connected with one another and then used as negative buses in a direct-current working mode;

Specifically, the dry load unit group includes a plurality of dry load units, and the number of the dry load units may be selected according to actual application requirements, so as to meet actual test requirements. For adapting to the AC medium voltage test, a dry type load unit comprises three-phase subunits, when the dry type load unit adopts three-phase star connection, one ends of the three-phase subunits are mutually connected to form a neutral point of the dry type load unit, the other ends of the three-phase subunits are mutually independent to form a load connecting end, namely, the load connecting end is provided with three connecting ends, and the three-phase AC bus or the anode bus can be adaptively and electrically connected through the load connecting end.

In specific implementation, when all the dry-type load units are connected in a three-phase star-shaped manner, the neutral points of all the dry-type load units are connected with each other, and the neutral points of all the dry-type load units are connected with each other and then used as a negative bus in a direct-current working mode.

The dry type load unit is universal under three-phase alternating voltage or direct current voltage, and when the dry type load unit works specifically and needs to be configured in an alternating current working mode when a medium-voltage alternating current test is needed; when a medium-voltage direct-current test is required, the dry-type load unit needs to be configured in a direct-current working mode. The dry load units in the dry load unit group are generally connected to a test by one or more dry load units during the test to provide the load power required by the test. The dry-type load units are uniformly configured in an alternating current working mode or a direct current working mode, specifically, when the dry-type load units are connected to a medium-voltage alternating current test or a medium-voltage direct current test, the dry-type load units which do not utilize the connection test are not configured in the alternating current working mode or the direct current working mode, and at the moment, the load connecting ends of the dry-type load single power supplies which do not utilize the connection are in a disconnection state and are not connected with a three-phase alternating current bus or a positive bus.

In order to ensure the reliability of the test, the dry load units in the dry load unit group can only be configured in the same working mode, that is, the dry load units configured in the dry load unit group are in the same working mode, that is, the same working mode is an alternating current working mode or a direct current working mode, so that the dry load units configured in the alternating current working mode and the dry load units configured in the direct current working mode are prevented from being present during the test.

When the dry load unit is configured in an alternating current working mode, the load connecting end of the dry load unit is in adaptive electrical connection with the three-phase alternating current bus to serve as a medium-voltage alternating current dry load. When the dry load unit is configured in a direct current working mode, the load connecting end of the dry load unit is electrically connected with the positive bus in a matching mode to serve as a medium-voltage direct current dry load. In specific implementation, the dry-type load unit is configured to be in an alternating current working mode or a direct current working mode, and is particularly related according to a scene and requirements of an actual test so as to meet actual test requirements.

Fig. 1 shows a specific implementation of the dry load unit group, in fig. 1, R1 to R8 are dry load units, that is, the dry load unit group in fig. 1 includes eight dry load units, and the dry load units R1 to R8 are all connected in a three-phase star-like manner. In the dry load units R1 to R8, each phase subunit includes two resistors connected in series, and in the specific implementation, the resistors in the same dry load unit have the same resistance, while the resistors in different dry load units may have different resistances, which may be specifically selected according to the requirement, so as to meet the requirement of the medium voltage ac test or the medium voltage dc test. Therefore, in fig. 1, the six resistors included in the dry load unit R1 have the same resistance value, but may be different from the six resistors included in the dry load unit R8.

In the embodiment of the invention, the dry-type load units in the dry-type load unit group can work in an alternating current working mode and a direct current working mode, the load power in the direct current working mode can reach two thirds in the alternating current working mode, and the utilization rate of the dry-type load unit group can be improved. On withstand voltage and insulating problem, each return circuit maximum voltage does not all exceed insulating material's tolerance ability under the direct current mode, possesses fine security performance to can satisfy the test demand of middling pressure direct current, can satisfy the test demand of middling pressure alternating current again, improve the utilization ratio of load, reduce test cost, safe and reliable.

Further, for any dry load unit, comprising an ac medium voltage contactor and a dc medium voltage contactor adapted to the dry load unit, wherein,

In specific implementation, in order to configure a dry load unit to enter an AC working mode or a DC working mode, each dry load unit includes an AC medium voltage contactor and a DC medium voltage contactor, where the specific types of the AC medium voltage contactor and the DC medium voltage contactor are based on the requirement of meeting the actual withstand voltage test, and if the medium voltage AC is AC 10.5kV and the medium voltage DC is DC 4kV, the dry load unit and the AC medium voltage contactor and the DC medium voltage contactor are set to meet the corresponding voltage classes, which are specifically consistent with the existing ones, and are not described herein again.

In order to enable the dry type load unit to be adaptively and electrically connected with the ac medium voltage contactor or the dc medium voltage contactor, in the embodiment of the present invention, the dry type load unit can be adaptively connected with the ac medium voltage contactor or the dc medium voltage contactor through the operation mode switching connection mechanism, which is not shown in fig. 1, but a specific implementation of the operation mode switching connection mechanism is shown in fig. 4.

In order to improve the stability and reliability of the test, the load connection end corresponding to the dry-type load unit is in adaptive connection with the outlet end of the main contact of the alternating current medium voltage contactor through the working mode switching connection mechanism or is in adaptive connection with the outlet end of the main contact of the direct current medium voltage contactor, so that the dry-type load unit cannot be configured under normal conditions, namely, the dry-type load unit cannot be accessed and configured to enter an alternating current working mode or a direct current working mode, namely, only when a dry-type load unit needs to be accessed according to the test requirement, the main contact of the alternating current medium voltage contactor or the main contact of the direct current medium voltage contactor can be selectively controlled to be closed.

When the method is implemented specifically, the wire inlet end of the main contact of the alternating-current medium-voltage contactor is in adaptive electric connection with the three-phase alternating-current bus, and the wire inlet end of the main contact of the direct-current medium-voltage contactor is in adaptive electric connection with the positive bus; and the outlet end of the main contact of the alternating-current medium-voltage contactor and the outlet end of the main contact of the direct-current medium-voltage contactor are correspondingly connected with the working mode switching connecting mechanism.

When a dry type load unit is matched with a corresponding alternating current medium voltage contactor and a corresponding direct current medium voltage contactor through a working mode switching connection mechanism, the main contact of the alternating current medium voltage contactor is controlled to be closed and the main contact of the direct current medium voltage contactor is controlled to be opened so as to configure that the dry type load unit is in an alternating current working mode, and at the moment, the load connection end of the dry type load unit is electrically connected with a three-phase alternating current bus through the working mode switching connection mechanism and the main contact of the alternating current medium voltage contactor in a closed state. When the main contact of the ac medium voltage contactor is controlled to be opened and the main contact of the dc medium voltage contactor is controlled to be closed, and the dry type load unit is configured to be in the dc operation mode, the load connection end of the dry type load unit is electrically connected to the positive electrode bus through the operation mode changeover connection mechanism and the main contact of the dc medium voltage contactor in the closed state.

Therefore, as can be seen from the above description, in a dry load unit, since the main contacts of the ac medium voltage contactor and the dc medium voltage contactor adapted to the dry load unit are not in the closed state at the same time, the reliability of the dry load unit during operation can be ensured.

In fig. 1, the contactors KJ1 to KJ8 are medium voltage ac contactors, and the contactors KZ1 to KZ8 are medium voltage dc contactors, wherein the medium voltage ac contactor KJ1 and the medium voltage dc contactor KZ1 correspond to the dry load unit R1, the medium voltage ac contactor KJ2 and the medium voltage dc contactor KZ1 correspond to the dry load unit R2, and the rest of the conditions are analogized in sequence, which can refer to the diagram of fig. 1, and the description is not repeated one by one.

In fig. 1, when the main contact of the medium-voltage ac contactor KJ1 is closed and the main contact of the medium-voltage dc contactor KZ1 is opened, the load connection terminal of the dry load unit R1 is electrically connectable to the three-phase ac bus, and at this time, the dry load unit R1 is placed in the ac operation mode. When the main contact of the medium-voltage ac contactor KJ1 is opened and the main contact of the medium-voltage dc contactor KZ1 is closed, the load connection end of the dry load unit R1 is electrically connected to the positive bus, and at this time, the dry load unit R1 is configured in the dc operation mode. The details of the other dry load units can be described with reference to the dry load unit R1, and will not be described in detail here.

Furthermore, the work mode switching connection mechanism comprises a busbar side connection unit which is in adaptive connection with a main contact outlet end of the alternating current medium voltage contactor, a resistance side connection unit which is in adaptive connection with a load connection end of the dry type load unit, a direct current side connection body which is used for connecting the main contact outlet end of the direct current medium voltage contactor, and a switching connection unit which is used for switching the connection state, wherein,

In order to realize the switching connection, in the embodiment of the invention, the working mode switching connection mechanism comprises a busbar side connection unit, a resistance side connection unit, a direct current side connection body and a switching connection unit for switching the connection state, the busbar side connection unit is in adaptive connection with the outlet end of the main contact of the alternating current medium voltage contactor, the resistance side connection unit is in adaptive connection with the load connection end of the dry type load unit, and the direct current side connection body is in adaptive connection with the outlet end of the main contact of the direct current medium voltage contactor.

Specifically, when the resistance side connection unit is correspondingly electrically connected with the busbar side connection unit through the switching connection unit, the dry type load unit can be electrically connected with the three-phase alternating current bus, that is, the dry type load unit is configured to enter an alternating current working mode. When the resistance side connecting unit is correspondingly and electrically connected with the direct current side connecting body through the switching connecting unit, the dry type load unit can be electrically connected with the positive bus, and the dry type load unit is configured to enter a direct current working mode.

Furthermore, the busbar side connecting unit comprises three parallel busbar side connecting copper bars which are respectively and correspondingly electrically connected with the main contact of the alternating-current medium-voltage contactor;

Fig. 4 shows a specific implementation of the operation mode switching connection mechanism, and when three busbar-side connection copper bars are adopted as the busbar-side connection units, the busbar-side connection units can improve the busbar capacity. The busbar side connecting copper bars are connected with three busbar sides in the busbar side connecting unit, the busbar side connecting first copper bars 1, the busbar side connecting second copper bars 2 and the busbar side connecting third copper bars 3 in the graph 4 are respectively arranged, the busbar side connecting first copper bars 1, the busbar side connecting second copper bars 2 and the busbar side connecting third copper bars 3 are distributed in parallel, the busbar side connecting first copper bars 1, the busbar side connecting second copper bars 2 and the busbar side connecting third copper bars 3 can adopt the same form, and the busbar side connecting third copper bars can be selected as required.

The busbar side is connected with the first copper bar 1, the busbar side is connected with the second copper bar 2, the busbar side is connected with the third copper bar 3 and is parallel to each other, the first end of the busbar side is connected with the first copper bar 1, the first end of the busbar side is connected with the second copper bar 2, and the first end of the busbar side is connected with the third copper bar 3 is correspondingly connected with a main contact of the alternating-current medium-voltage contactor, specifically, the first end is correspondingly connected with a leading-out end of the main contact of the alternating-current medium-voltage contactor.

In fig. 4, three parallel resistor-side connecting copper bars in the resistor-side connecting unit are respectively: the resistance side is connected first copper bar 4, the resistance side is connected second copper bar 5 and the resistance side is connected third copper bar 6, and the resistance side is connected first copper bar 4, the resistance side is connected second copper bar 5 and the resistance side is connected third copper bar 6 and is distributed side by side, and can adopt identical form, specifically can select as required.

The three resistance side connecting copper bars are in one-to-one positive correspondence with the three busbar side connecting copper bars in the busbar side connecting unit, specifically, a resistance side connecting first copper bar 4 is in positive correspondence with a busbar side connecting first copper bar 1, a resistance side connecting second copper bar 5 is in positive correspondence with a busbar side connecting second copper bar 2, and a busbar side connecting third copper bar 3 is in positive correspondence with a resistance side connecting third copper bar 6; the positive correspondence is coaxial distribution. After the dry-type load unit is just corresponding, the first copper bar 4 is connected to the resistance side, the second copper bar 5 is connected to the resistance side, and the corresponding first end of the third copper bar 6 is connected to the resistance side, and the first copper bar 1 is connected to the adjacent mother board side, the second copper bar 2 is connected to the mother board side, the corresponding second end of the third copper bar 3 is connected to the mother board side, the first copper bar 4 is connected to the resistance side, the second copper bar 5 is connected to the resistance side, and the corresponding second end of the third copper bar 6 is connected to the resistance side, and the corresponding connection is the end connection of the corresponding subunit in the dry-type load unit.

In fig. 4, the dc side connecting body is the dc side connecting copper bar 7, the dc side connecting copper bar 7 is connected with the resistor side connecting first copper bar 4, the resistor side connecting second copper bar 5 and the resistor side connecting third copper bar 6 in parallel, and may adopt the same form. Specifically, the first end of the direct current side connection copper bar 7 is aligned with the first end corresponding to the resistance side connection first copper bar 4, the resistance side connection second copper bar 5 and the resistance side connection third copper bar 6, and the second end of the direct current side connection copper bar 7 is connected with the wire outlet end of the main contact of a corresponding medium-voltage direct current contactor.

In fig. 4, three switching connection copper bars in the switching connection unit are respectively: the first copper bar 8, the second copper bar 9 and the third copper bar 10 are connected in a switching way; when female row side linkage unit, resistance side linkage unit and direct current side connector adopt above-mentioned implementation form, usable switching connection first copper bar 8 realizes female row side connection first copper bar 1 and resistance side connection first copper bar 4 conductive connection, utilize switching connection second copper bar 9 to realize female row side connection second copper bar 2 and resistance side connection second copper bar 5 conductive connection, utilize switching connection third copper bar 10 to realize female row side connection third copper bar 3 and resistance side connection third copper bar 6 conductive connection, at this moment, realize promptly entering into the alternating current mode with the configuration of dry-type load unit.

When the direct current working mode needs to be configured, the two ends of the switching connection first copper bar 8 are respectively and electrically connected with the first ends corresponding to the resistance side connection first copper bar 4 and the resistance side connection second copper bar 5, and the two ends of the switching connection second copper bar 9 are respectively and electrically connected with the first ends corresponding to the resistance side connection second copper bar 5 and the resistance side connection third copper bar 6; the two ends of the switching connection third copper bar 10 are respectively connected with the first ends corresponding to the resistance side connection third copper bar 6 and the direct current side connection copper bar 7.

Therefore, the corresponding connection states required for the configuration to enter the alternating current working mode and the direct current working mode can be met by switching the connection of the first copper bar 8, the second copper bar 9 and the third copper bar 10. Because when entering alternating current mode and direct current mode, the mode that the switching linkage unit is connected is different, during specific implementation, can manually adjust the required connection state of switching connection first copper bar 8, switching connection second copper bar 9 and switching connection third copper bar 10, perhaps adopts the required connection state of automatic adjustment, specifically with can satisfy the configuration and get into required mode as the standard, no longer gives details here. Of course, in specific implementation, the operation mode switching connection mechanism may also adopt other required implementation forms, and specifically may be subject to the requirement of meeting the actual configuration operation mode according to the requirement.

Furthermore, the neutral points of all the dry-type load units in the dry-type load unit group are connected, and a voltage sensor for measuring the neutral point-to-ground voltage state of the dry-type load units is configured;

In the embodiment of the present invention, the neutral points of all dry load units are connected, and after being grounded through the voltage sensor, the voltage sensor is used to measure the voltage state of the dry load neutral point to the ground, and in fig. 1, PT12 is the configured voltage sensor. During specific implementation, after the neutral-to-ground voltage is measured by using a voltage sensor, load working state monitoring based on the neutral-to-ground voltage can be implemented, and configured load working state monitoring comprises abnormal switching monitoring in an alternating current working mode, load health state monitoring in the alternating current working mode and/or ground insulation state monitoring in a direct current working mode.

The following describes the specific details of the load operation state monitoring.

And monitoring switching abnormity in an alternating current working mode, and alarming neutral point deviation when neutral point deviation of the medium-voltage alternating current dry load is determined according to the neutral point-to-ground voltage.

Specifically, in an alternating-current working mode, a first copper bar 1 is connected to the busbar side, a second copper bar 2 is connected to the busbar side, and a third copper bar 3 is connected to the busbar side and distributed in parallel at intervals, and respectively corresponds to a first copper bar 4 connected to the resistor side, a second copper bar 5 connected to the resistor side, and a third copper bar 6 connected to the resistor side; the lengths of the first copper bar 8, the second copper bar 9 and the third copper bar 10 are designed according to the interval length.

When a dry-type load unit is switched from a direct-current working mode to an alternating-current working mode, if one of the first copper bar 8, the second copper bar 9 and the third copper bar 10 is not dismounted or switched as required, the neutral point of the dry-type load unit can shift, the neutral point-to-ground voltage which can be quickly detected by a voltage sensor at the neutral point is abnormal, and the neutral point of the medium-voltage alternating-current dry-type load can be determined to be cheap, and at the moment, an alarm is sent out in time.

In practical implementation, normally, since the load cannot be strictly three-phase symmetric, the neutral-point ground voltage will be a small value, such as 10V, but in the above-mentioned case of not being removed or switched as required, the amplitude of the neutral-point ground voltage will become large to the amplitude of the phase voltage of a certain phase, such as 6300V, and the neutral-point voltage offset can be identified by the difference in this order of magnitude. Meanwhile, in the alternating current working mode, due to the fact that the dry type load unit is in a state that one phase is disconnected and two phases work (the short-circuit phase resistor and the disconnected phase resistor are still connected in parallel), except for load power abnormity, other dangers cannot be caused (under the condition that three phases are not recovered to be connected with copper bars according to the alternating current mode, the dry type load unit is in a complete disconnection state, the dry type load unit is in a failure state but cannot cause dangers, and the failure state cannot be used as an effective load).

In the direct current working mode, if there is a copper bar still in the alternating current mode connection mode (the copper bar is in the alternating current mode connection, specifically, there is a conductive connection between one of the busbar side connection copper bars and the corresponding one of the resistor side connection copper bars), the resistance value of the dry type load unit becomes large, and the upper computer detects that the sent loading amplitude is different from the actual loading amplitude, and immediately sends out an alarm. Under the condition, the working state of the dry type load unit which is connected correctly is consistent with the normal working condition, and no fault occurs. The incorrectly connected dry load unit can also keep the contact points from being broken down because the contact points of the voltage alternating current contactor are higher in withstand voltage than the direct current voltage value. Therefore, in the dc mode, the dry load unit can also ensure the load electrical safety under the condition that the dry load unit is connected in error/wrong.

In practice, since the resistance of each load circuit is fixed, the rated current of the load circuit should be fixed. If for a certain load power supply that former rated power is 800KW under the mode of alternating current operation, after present dry-type load drops into, discover the power that increases when for example only 400KW, can think that abnormal conditions has appeared, 800KW is the loading amplitude of sending out promptly, and 400KW is actual loading amplitude. In the above process, under the condition of constant voltage, the determination is mainly obtained by detecting the change condition of the load current.

Further, when monitoring a load fault in an alternating current working mode, determining the amplitude of the neutral-to-ground voltage and the phase of the neutral-to-ground voltage by using a voltage sensor;

Specifically, in the alternating current operating mode, the neutral points of the dry-type load units are connected through the copper bar, and the voltage sensor simultaneously monitors the phase of the ground voltage except for measuring the amplitude of the ground voltage of the neutral points. The neutral point-to-ground voltage of the dry type load unit can be monitored through the measured neutral point-to-ground voltage, the working condition of the three-phase dry type load unit can be reflected, whether any dry type load unit is balanced or not is monitored, and when the dry type load unit is unbalanced, after the dry type load unit is configured to enter an alternating current working mode, the phase and amplitude of the neutral point-to-ground voltage can be changed simultaneously compared with the phase and amplitude before the dry type load unit is configured to enter the alternating current working mode.

In particular, the voltage sensor may give a complete waveform of neutral to ground voltage. For example, before a dry load unit is connected, the neutral-to-ground voltage has an amplitude of 5V and an initial phase angle of the current voltage waveform is 0 degrees. After the current dry-type load unit is connected, the amplitude of the current neutral-point-to-ground voltage and the variation of the phase angle before the current neutral-point-to-ground voltage and the phase angle before the current neutral-point-to-ground voltage are obtained by detecting the waveform of the connected neutral-point-to-ground voltage. For example, if the amplitude and phase of the neutral-point-to-ground voltage before connection are 5V (0 °), and the amplitude and phase of the current neutral-point-to-ground voltage are 4V (30 °), the variation of the neutral-point voltage due to the imbalance of the current dry load unit is the vector difference between the two, that is: 5V (0 °) -4V (30 °) =3 (-60 °), and the approximate values of the load phase and the resistance value that become large in the dry load unit can be known from the vector difference.

Specifically, taking the dry load unit R1 and the dry load unit R2 as an example, specifically, the dry load unit R1 is in a good state, and after the dry load unit R1 is configured into an ac operating mode, three phases of the dry load unit R1 are completely symmetrical, and at this time, a phase and an amplitude of a neutral point of the dry load unit R1 to a ground voltage are both 0. The resistance value of the phase A is increased due to the fact that the resistance wire is blown out, and after the dry load unit R2 is configured to enter an alternating current working mode, the voltage of the phase A in the dry load unit R2 is higher than the voltage of the phase B and the phase C. The neutral point of the dry load unit R2 is shifted toward phase a. At this time, the voltage sensor detects that both the magnitude and the phase of the neutral-to-ground voltage change. According to the change situation, the neutral point deviation situation can be obtained, and therefore the situation that the three-phase load resistance value in the current dry-type load unit R2 is unbalanced is calculated. For any dry-type load unit, the balance means that the three-phase sub-units of the dry-type load unit have the same resistance value, and the resistance values of any Xiang Zi unit are different, i.e. are unbalanced.

According to the change conditions of the phase and amplitude of the neutral point-to-ground voltage before and after the dry type load unit is configured to enter the alternating current working mode, the vector difference of the neutral point-to-ground voltage before and after the dry type load unit enters the alternating current working mode is calculated, the phase of the resistance wire with the fault can be accurately positioned, the fault condition of the resistance wire is known, and a basis is provided for evaluating the health condition of the resistance wire.

When the dry-type load unit is in specific implementation, the resistance wire in the dry-type load unit is formed by connecting dozens or hundreds of resistance wires with fixed resistance values in series and in parallel, and the resistance wires working at the positions with higher temperature are easy to burn off because the local temperature in the load is higher than that in other places when the load works, so that the overall resistance value of a certain phase of the resistance unit is increased, and the dry-type load unit has a three-phase unbalanced condition.

In a direct current working mode, the neutral point-to-ground voltage measured by the voltage sensor is the negative bus voltage-to-ground voltage. When the dry load unit is lowered in insulation to ground, in the case that the neutral point of the test equipment (such as a direct current generator) is grounded, the neutral-to-ground voltage is deviated from zero to the polarity with high insulation to ground, and the larger the deviation of the positive and negative insulation to ground, the more obvious the deviation is. Therefore, by monitoring the degree of deviation of the negative bus-to-ground voltage (-DC 2000V), the dry load cell insulation to ground can be evaluated. The position and polarity of the specific occurrence of the insulation drop of the dry load cell pair can be monitored in conjunction with the conditions before and after the dry load cell configuration enters the dc operating mode.

Specifically, in the positive and negative ground insulation, the positive electrode refers to a positive bus to a direct current contactor bus side, and the negative ground insulation refers to a dry load unit and a negative bus from a direct current medium voltage contactor load side. When the insulation of the positive and negative electrodes to the ground is good, the voltage of the positive electrode to the ground should be 2000V, and the voltage of the negative electrode to the ground should be-2000V. The voltage to ground measured by the voltage sensor should be-2000V. If the neutral-to-ground voltage measured by the voltage sensor is-1900V, it is proved that the positive-electrode-to-ground voltage rises to 2100V at this time, and the voltage neutral point shifts to the negative electrode by 100V, that is, the negative electrode insulation falls (i.e., the position and polarity of the fall) compared with the positive electrode insulation at this time, otherwise, the same process is not repeated here.

Furthermore, the device also comprises a contactor closing control circuit used for controlling the corresponding opening and closing states of the alternating current medium voltage contactor and the direct current medium voltage contactor, wherein,

when the contactor closing control circuit is used for controlling the alternating current medium voltage contactor to be in a closed state, the direct current medium voltage contactor is locked to be in an open state, or when the contactor closing control circuit is used for controlling the direct current medium voltage contactor to be in a closed state, the alternating current medium voltage contactor is locked to be in an open state.

Since any dry-type load unit is correspondingly and adaptively connected with an ac medium-voltage contactor and a dc medium-voltage contactor, it is necessary to control the switching of the ac medium-voltage contactor and the dc medium-voltage contactor by using a contactor switching control circuit. In the embodiment of the invention, the alternating current medium voltage contactor and the direct current medium voltage contactor are controlled by a set of contactor closing control circuit.

Specifically, when the contactor closing control circuit is used for controlling the alternating current medium voltage contactor to be in a closed state, the direct current medium voltage contactor is locked to be in an open state, or when the contactor closing control circuit is used for controlling the direct current medium voltage contactor to be in a closed state, the alternating current medium voltage contactor is locked to be in an open state. The interlocking of the alternating-current medium-voltage contactor and the direct-current medium-voltage contactor during working can be realized, the condition that the alternating-current medium-voltage contactor and the direct-current medium-voltage contactor are closed simultaneously is avoided for the same dry-type load unit, and the stability and the reliability of the dry-type load unit during working are ensured.

Fig. 2 and 3 show a specific implementation of the closing control circuit of the contactor, where KZ1 to KZ8 in fig. 2 are coils corresponding to the medium-voltage dc contactors KZ1 to KZ8, KJ1 to KZ8 are coils corresponding to the medium-voltage ac contactors KJ1 to KJ8, KMZ1 to KMZ8 are normally open contacts corresponding to the intermediate contactors KMZ1 to KMZ8, and KMJ1 to KMJ8 are normally open contacts corresponding to the intermediate contactors KMJ1 to KMJ 8. QK4 and QK8 are power switches, and DC 110V is a converter for converting an external 220V power supply into DC 110V.

In fig. 3, QK2 and QK6 are power switches, and DC 24V is a converter for converting an external 220 power supply into a direct current 24V, wherein a portion including coils of intermediate contactors KMZ1 to KMKZ8 is a control portion of a direct current medium voltage contactor, specifically, 1JZ1, 1JZ3, 1JZ5, 1JZ7, 1JZ9, 1JZ11, 1JZ13, and 1JZ15 are closing buttons corresponding to the direct current medium voltage contactor, 1JZ2, 1JZ4, 1JZ6, 1JZ8, 1JZ10, 1JZ12, 1JZ14, and 1JZ16 are opening buttons corresponding to the direct current medium voltage contactor, and z1 is a coil and a normally open contact of the intermediate contactor, respectively.

Taking the dry load unit R1 corresponding to the medium-voltage direct-current contactor KZ1 as an example, 1JZ1 is a closing button of the dry load unit R1, 1JZ2 is an opening button of the dry load unit R1, KMJ1 is a normally closed contact of the intermediate contactor KMJ1, and the normally open contact of the intermediate contactor KMZ1 is connected in parallel with the closing button 1JZ 1. Under normal work, closing button 1JJZ is closed, and at this moment, the normally closed of separating brake button 1JZ2 and KMJ1 all is the closure attitude, and is closed with the normally open contact KMZ1 parallelly connected at button 1JZ1 to form the auto-lock, simultaneously, because the normally open contact of middle contactor KMZ1 is closed, make the coil of medium voltage direct current contactor KZ1 get electric actuation, medium voltage direct current contactor KZ1 normally closes the floodgate.

If the medium-voltage ac contactor KJ1 is initially closed (the normally closed point of the intermediate contactor KMJ1 is opened), at this time, since the KMJ1 is opened, the coil of the intermediate contactor KMZ1 cannot be electrically closed, and the medium-voltage dc contactor KZ1 cannot be closed. Meanwhile, when the medium-voltage direct-current contactor KZ1 is switched on, when a switching-on button of the medium-voltage alternating-current contactor KJ1 is pressed by mistake, the medium-voltage direct-current contactor KZ1 is also disconnected due to the fact that the normally closed contact of the intermediate contactor KMJ1 is disconnected, and the interlocking function can be achieved.

For other specific cases of the medium voltage dc contactors KZ2 to KZ8, reference may be made to the description of the dc medium voltage contactor KZ1, which is not illustrated here.

Specifically, a portion including the coils of the intermediate contactors KMJ1 to KMMJ8 is a control portion of the ac medium voltage contactor, specifically, 2JZ1, 2JZ3, 2JZ5, 2JZ7, 2JZ9, 2JZ11, 2JZ13, and 2JZ15 are closing buttons corresponding to the ac medium voltage contactors, 2JZ2, 2JZ4, 2JZ6, 2JZ8, 2JZ10, 2JZ12, 2JZ14, and 2JZ16 are opening buttons corresponding to the ac total voltage contactors, and KMJ1 is a coil of the intermediate contactor and a normally open contact, respectively.

For the control of the ac medium-voltage contactor, reference may be made to the switching control of the medium-voltage dc contactor KZ1 described above, and the detailed description thereof is omitted here.

And further, the system also comprises a quick fuse group for fusing protection, wherein the quick fuse group comprises a plurality of quick fuses with required current levels, so that the quick fuses in the quick fuse group are utilized to fuse and protect the dry type load unit configured in an alternating current working mode or a direct current working mode.

When the fuse protector is specifically implemented, the fuse protector is used for fusing protection, and the fusing protection of the required current level needs to be met by the fuse protector. In fig. 1, QS1 is a switch of a three-phase ac bus, and QS2 is a switch of a positive electrode bus and a negative electrode bus. The fast fuse group comprises a fuse FU 1-FU 8 and a fuse F1-FU F9, wherein the fuse FU 1-FU 8 is a fuse matched with an alternating current medium voltage contactor, the F1 can be fused and protected to neutral point ground, and the F2-F9 is a fuse matched with a direct current medium voltage contactor. Of course, in specific implementation, the fast fuse set may also adopt other forms so as to realize fast fuse protection.

In summary, a method for switching operation of a dc/ac universal medium voltage dry load, including a dry load cell group for forming the dc/ac universal medium voltage dry load and an operation switching controller for controlling the operation switching, wherein,

In specific implementation, reference may be made to the above description for a specific switching control manner and process for implementing that the dry load unit configuration in the dry load unit group enters the dc working mode or the ac working mode, and details are not described herein again.

Claims

1. An alternating current-direct current universal medium-voltage dry load is characterized in that: the system comprises a dry-type load unit group, wherein the dry-type load unit group comprises a plurality of dry-type load units which are connected in a three-phase star shape, neutral points of all the dry-type load units are connected with one another, and the neutral points of all the dry-type load units are connected with one another and then used as negative buses in a direct-current working mode;

configuring a dry-type load unit to be in an alternating current working mode or a direct current working mode, wherein when the dry-type load unit is configured to be in the alternating current working mode, a load connecting end of the dry-type load unit is in adaptive electrical connection with a three-phase alternating current bus in the alternating current working mode, so that the dry-type load unit is configured to be used as a medium-voltage alternating current dry-type load; when the dry type load unit is configured to be in a direct current working mode, the load connecting end of the dry type load unit is in adaptive electrical connection with the positive bus in the direct current working mode, so that the dry type load unit is configured to be used as a medium-voltage direct current dry type load;

during operation, the dry load units in the dry load unit group can only be configured in the same operation mode.

2. The ac-dc universal medium voltage dry load of claim 1, further comprising: for any dry load unit, the system comprises an alternating current medium voltage contactor and a direct current medium voltage contactor which are matched with the dry load unit, wherein,

3. The ac-dc universal medium voltage dry load of claim 2, further comprising: the working mode switching connecting mechanism comprises a busbar side connecting unit which is in adaptive connection with a main contact of the alternating current medium voltage contactor, a resistance side connecting unit which is in adaptive connection with a load connecting end of the dry type load unit, a direct current side connecting body which is used for connecting a main contact outlet end of the direct current medium voltage contactor and a switching connecting unit which is used for switching the connecting state, wherein,

4. The ac-dc universal medium voltage dry load according to claim 3, wherein: the busbar side connecting unit comprises three parallel busbar side connecting copper bars which are respectively and correspondingly electrically connected with the main contact of the alternating-current medium-voltage contactor;

the switching connection unit comprises at least three switching connection copper bars, the three switching connection copper bars are utilized to enable the resistance side connection copper bars to be in one-to-one corresponding connection with the busbar side connection copper bars, or the three switching connection copper bars are utilized to enable the resistance side connection copper bars to be electrically connected with the direct current side connector.

5. The AC/DC universal medium voltage dry load according to any one of claims 1 to 4, wherein: the neutral points of all dry-type load units in the dry-type load unit group are connected, and a voltage sensor for measuring the neutral point-to-ground voltage state of the dry-type load units is configured;

6. The AC/DC universal medium voltage dry load according to claim 5, wherein: and when the switching abnormity is monitored in the alternating current working mode, the neutral point deviation alarm is carried out when the neutral point deviation of the medium-voltage alternating current dry load is determined according to the neutral point to ground voltage.

7. The AC/DC universal medium voltage dry load according to claim 5, wherein: when monitoring a load fault in an alternating-current working mode, determining the amplitude of a neutral point-to-ground voltage and the phase of the neutral point-to-ground voltage by using a voltage sensor;

8. The AC/DC universal medium voltage dry load according to any one of claims 2 to 4, wherein: also comprises a contactor closing control circuit for controlling the corresponding opening and closing states of the alternating current medium voltage contactor and the direct current medium voltage contactor, wherein,

9. The AC/DC universal medium voltage dry load according to any one of claims 1 to 4, wherein: the system is characterized by further comprising a quick fuse group for fusing protection, wherein the quick fuse group comprises a plurality of quick fuses of required current levels, and the quick fuses in the quick fuse group are used for fusing protection of dry-type load units configured in an alternating current working mode or a direct current working mode.

10. A work switching method of an alternating current-direct current universal medium-voltage dry load is characterized by comprising the following steps: comprises a dry type load unit group for forming an AC/DC universal medium-voltage dry type load and a work switching controller for controlling work switching,

configuring the ac/dc common dry load in a state as claimed in any one of claims 1 to 9 using an operation switching controller to switch control over the operating state of the ac/dc common medium voltage dry load.