CN107132463B - Short circuit preventing device for secondary winding of voltage transformer - Google Patents
Short circuit preventing device for secondary winding of voltage transformer Download PDFInfo
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- CN107132463B CN107132463B CN201710432223.9A CN201710432223A CN107132463B CN 107132463 B CN107132463 B CN 107132463B CN 201710432223 A CN201710432223 A CN 201710432223A CN 107132463 B CN107132463 B CN 107132463B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/36—Overload-protection arrangements or circuits for electric measuring instruments
Abstract
The invention provides a voltage transformer secondary winding short-circuit prevention device which is arranged between a voltage transformer secondary winding and a voltage transformer sampling unit measuring loop and comprises an air switch, a wiring terminal and a protection circuit board, wherein the protection circuit board comprises a main loop resistor, a protection resistor, a light-emitting diode and a fuse; the wire inlet end of the air switch is connected with the live wire and the zero wire of the secondary winding of the voltage transformer, the wire outlet end of the air switch is connected with one end of the main loop resistor, the other end of the main loop resistor is connected with one end of the fuse, the other end of the fuse is connected with one end of the protection resistor or the positive electrode of the light emitting diode while being connected with the wire inlet end of the connecting terminal, the other end of the protection resistor or the negative electrode of the light emitting diode is connected with the wire inlet end of the connecting terminal, and the wire outlet end of the connecting terminal is connected with the live wire and the zero wire of the voltage transformer sampling unit measuring loop. The invention can eliminate the potential safety hazard of the short circuit of the secondary winding of the voltage transformer caused by the short circuit of the test loop.
Description
Technical Field
The invention belongs to the technical field of electrical engineering, and particularly relates to a secondary winding short-circuit prevention device of a voltage transformer.
Background
The capacitive equipment insulation on-line monitoring system mainly measures tg delta and Cx (pF) of the capacitive equipment such as 220kV main transformer bushings, current transformers, coupling capacitors and the like, and resistive current and full current of a zinc oxide arrester, and comprehensively judges the insulation condition of the capacitive equipment by comparing and analyzing the data.
The capacitive equipment insulation on-line monitoring system mainly measures bus voltage vectors and leakage current vectors flowing through a tested object through a voltage transformer sampling unit and a tested equipment sampling unit, and then inputs all test signals into a host through a cable channel for data processing and analysis and calculation. However, when the secondary voltage of the voltage transformer is measured through the voltage transformer sampling unit, the secondary winding of the voltage transformer is frequently caused to have short-circuit faults due to the fact that a signal channel is damaged by external force, man-made misoperation, faults of a testing instrument and the like, and once the short-circuit faults occur, the secondary winding can generate large short-circuit current to burn the voltage transformer, so that the stability and the safety of a system are seriously affected.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the utility model provides a voltage transformer secondary winding prevents short circuit device to solve the problem that leads to burning loss voltage transformer because of voltage transformer secondary winding short circuit.
The invention provides a voltage transformer secondary winding short-circuit prevention device which is arranged between a voltage transformer secondary winding and a voltage transformer sampling unit measuring loop and comprises an air switch, a wiring terminal and a protection circuit board, wherein the protection circuit board comprises a main loop resistor, a protection resistor, a light-emitting diode and a fuse; the wire inlet end of the air switch is connected with the live wire and the zero wire of the secondary winding of the voltage transformer, the wire outlet end of the air switch is connected with one end of the main loop resistor, the other end of the main loop resistor is connected with one end of the fuse, the other end of the fuse is connected with one end of the protection resistor or the positive electrode of the light emitting diode while being connected with the wire inlet end of the wiring terminal, the other end of the protection resistor or the negative electrode of the light emitting diode is connected with the wire inlet end of the wiring terminal, and the wire outlet end of the wiring terminal is connected with the live wire and the zero wire of the voltage transformer sampling unit measuring loop;
furthermore, preferably, the voltage transformer comprises a first secondary winding, a second secondary winding and a third secondary winding, wherein the first secondary winding comprises a live wire A and a zero line N, the second secondary winding comprises a live wire B and a zero line N, and the third secondary winding comprises a live wire C and a zero line N; the voltage transformer sampling unit measuring loop comprises a first measuring loop, a second measuring loop and a third measuring loop, wherein the first measuring loop comprises a live wire a and a zero line n, the second measuring loop comprises a live wire b and a zero line n, and the third measuring loop comprises a live wire c and a zero line n; the air switch comprises a first path, a second path, a third path and a fourth path; the wiring terminal comprises a first hole, a second hole, a third hole and a fourth hole; the main loop resistor comprises a first main loop resistor, a second main loop resistor and a third main loop resistor; the protection resistor comprises a first protection resistor, a second protection resistor, a third protection resistor and a fourth protection resistor; the fuse comprises a first fuse, a second fuse and a third fuse; the light emitting diodes comprise a first light emitting diode, a second light emitting diode and a third light emitting diode; the wire inlet of the first path is connected with the live wire of the first secondary winding, the wire outlet of the first path is connected with one end of a first main loop resistor, the other end of the first main loop resistor is connected with one end of a first fuse, the other end of the first fuse is connected with the wire inlet end of a first hole and one end of a first protection resistor, the other end of the first protection resistor is connected with the positive electrode of a first light emitting diode, the negative electrode of the first light emitting diode is connected with one end of a fourth protection resistor, the other end of the fourth protection resistor is connected with the wire inlet end of a fourth hole, the wire outlet end of the fourth hole is connected with a zero wire of a first measurement loop, and the live wire of the first measurement loop is connected with the wire outlet end of the first hole; the wire inlet end of the second path is connected with the fire wire of the second secondary winding, the wire outlet end of the second path is connected with one end of a second main loop resistor, the other end of the second main loop resistor is connected with one end of a second fuse, the other end of the second fuse is connected with the wire inlet end of a second hole and one end of a second protection resistor, the other end of the second protection resistor is connected with the positive electrode of a second light emitting diode, the negative electrode of the second light emitting diode is connected with one end of a fourth protection resistor, the other end of the fourth protection resistor is connected with the wire inlet end of a fourth hole, the wire outlet end of the fourth hole is connected with a zero wire of a second measurement loop, and the fire wire of the second measurement loop is connected with the wire outlet end of the second hole; the wire inlet of the third path is connected with the fire wire of the third secondary winding, the wire outlet of the third path is connected with one end of a third main loop resistor, the other end of the third main loop resistor is connected with one end of a third fuse, the other end of the third fuse is connected with the wire inlet of a third hole and one end of a third protection resistor, the other end of the third protection resistor is connected with the positive electrode of a third light emitting diode, the negative electrode of the third light emitting diode is connected with one end of a fourth protection resistor, the other end of the fourth protection resistor is connected with the wire inlet of a fourth hole, the wire outlet of the fourth hole is connected with a zero wire of a third measurement loop, and the wire outlet of the third measurement loop is connected with the wire outlet of the third hole; the wire inlet end of the fourth path is respectively connected with zero wires of the first secondary winding, the second secondary winding and the third secondary winding, and the wire outlet end of the fourth path is connected with the wire inlet end of the fourth hole through a wire.
In addition, the rated currents of the first fuse, the second fuse and the third fuse are all 0.5A; the resistance values of the first main loop resistor, the second main loop resistor and the third main loop resistor are all 20Ω; the resistance values of the first protection resistor, the second protection resistor and the third protection resistor are 2400 omega, and the resistance value of the fourth protection resistor is 120 omega; the working current of the first light emitting diode, the second light emitting diode and the third light emitting diode is 20mA.
Furthermore, the short-circuit prevention device for the secondary winding of the voltage transformer also comprises an epoxy resin plate arranged in a terminal box of the voltage transformer, and the air switch, the wiring terminal and the protection circuit board are respectively fixed on the epoxy resin plate.
Through the design scheme, the invention has the following beneficial effects:
1. the potential safety hazard of the short circuit of the secondary winding of the voltage transformer caused by the short circuit of the sampling unit of the voltage transformer is eliminated, so that the safety of the system operation is improved.
2. The current of the measuring loop of the quick-break voltage transformer sampling unit of the fuse is effectively limited, so that insulation of the secondary winding of the voltage transformer is prevented from being reduced and service life is shortened due to overlarge current.
Drawings
The invention is further described with reference to the drawings and detailed description which follow:
FIG. 1 is a schematic circuit diagram of a secondary winding short circuit prevention device of a voltage transformer;
fig. 2 is an equivalent circuit diagram of the secondary winding short-circuit prevention device for the voltage transformer in the invention when A, B phases are short-circuited;
FIG. 3 is an equivalent circuit diagram of the secondary winding anti-short circuit device of the voltage transformer when A phase is short-circuited;
fig. 4 is a circuit diagram of a light emitting diode circuit in the secondary winding short circuit prevention device of the voltage transformer.
In the figure: QF-air switch, J-binding post, R1-first main loop resistance, R2-second main loop resistance, R3-third main loop resistance, R1-first protection resistance, R2-second protection resistance, R3-third protection resistance, R4-fourth protection resistance, F1-first fuse, F2-second fuse, F3-third fuse, L1-first LED, L2-second LED, L3-third LED.
Detailed Description
The voltage transformer secondary winding short-circuit prevention device is arranged between the voltage transformer secondary winding and the voltage transformer sampling unit measurement loop, and is used for cutting off a circuit between the voltage transformer sampling unit measurement loop and the voltage transformer secondary winding when the voltage transformer sampling unit measurement loop is short-circuited, so that the voltage transformer secondary winding is prevented from being burnt due to excessive current.
Epoxy resin board installed in terminal box of voltage transformer, air switch, wiring terminal and protection circuit board are respectively fixed on the epoxy resin board
The voltage transformer secondary winding short-circuit prevention device comprises an epoxy resin plate, an air switch, a wiring terminal and a protection circuit board, wherein the air switch, the wiring terminal and the protection circuit board are all fixed on the epoxy resin plate, and the epoxy resin plate is arranged in a voltage transformer terminal box.
The protection circuit board is connected between the air switch and the wiring terminal and specifically comprises a main loop resistor, a protection resistor, a light emitting diode and a fuse; the wire inlet end of the air switch is connected with the live wire and the zero wire of the secondary winding of the voltage transformer, the wire outlet end of the air switch is connected with one end of the main loop resistor, the other end of the main loop resistor is connected with one end of the fuse, the other end of the fuse is connected with one end of the protection resistor or the positive electrode of the light emitting diode while being connected with the wire inlet end of the connecting terminal, the other end of the protection resistor or the negative electrode of the light emitting diode is connected with the wire inlet end of the connecting terminal, and the wire outlet end of the connecting terminal is connected with the live wire and the zero wire of the voltage transformer sampling unit measuring loop.
The fuse is used for cutting off a line between the secondary winding of the voltage transformer and the measuring loop of the sampling unit of the voltage transformer when the flowing current exceeds the rated current of the fuse.
The air switch is used to ensure that the line is voltage-free when the fuse is replaced or the like.
The light-emitting diode is used for displaying the working state of the fuse, and when the fuse is not fused, the light-emitting diode lights to indicate that the measuring loop of the voltage transformer sampling unit is not short-circuited; when the fuse is fused, the LED is turned off to indicate that the measuring loop of the voltage transformer sampling unit is short-circuited.
The main loop resistance is used to ensure that the fuse can quickly blow.
The wiring terminal is used for protecting a circuit, and original wiring of a sampling unit measuring loop of the sampling voltage transformer is not changed.
The voltage transformer comprises at most three secondary windings, each secondary winding corresponds to one measuring loop, and the number of the measuring loops of the voltage transformer sampling unit is determined by the number of the secondary windings of the voltage transformer. The secondary winding and the measuring loop respectively comprise a live wire and a zero wire, and the voltage transformer comprises three secondary windings as an example.
Fig. 1 shows a circuit structure of a secondary winding short-circuit prevention device of a voltage transformer.
As shown in fig. 1, the secondary windings of the voltage transformer are a first secondary winding, a second secondary winding and a third secondary winding respectively, the live wire of the first secondary winding is called an a phase, the live wire of the second secondary winding is called a B phase, the live wire of the third secondary winding is called a C phase, and the zero wires of the first secondary winding, the second secondary winding and the third secondary winding are all called N phases; the voltage transformer sampling unit measuring loop is respectively a first measuring loop, a second measuring loop and a third measuring loop, the live wire of the first measuring loop is called a phase, the live wire of the second measuring loop is called b phase, the live wire of the third measuring loop is called c phase, and the zero wires of the first measuring loop, the second measuring loop and the third measuring loop are all called n phases; the air switch is a four-way air switch, which is respectively a first way, a second way, a third way and a fourth way, the zero line N phases of the first secondary winding, the second secondary winding and the third secondary winding are twisted into a strand to be connected into the fourth way, and the live wire A phase of the first secondary winding, the live wire B phase of the second secondary winding and the live wire C phase of the third secondary winding are respectively connected into the first way, the second way and the third way; the wiring terminal is a four-hole wiring terminal, and is respectively a first hole, a second hole, a third hole and a fourth hole, the zero line n phases of the first measuring loop, the second measuring loop and the third measuring loop are twisted into one strand to be connected into the fourth hole, and the live wire a phase of the first measuring loop, the live wire b phase of the second measuring loop and the live wire c phase of the third measuring loop are respectively connected into the first hole, the second hole and the third hole.
The main loop resistance includes a first main loop resistance R1, a second main loop resistance R2, and a third main loop resistance R3.
The protection resistors include a first protection resistor r1, a second protection resistor r2, a third protection resistor r3, and a fourth protection resistor r4.
The fuses include a first fuse F1, a second fuse F2, and a third fuse F3; the light emitting diodes include a first light emitting diode L1, a second light emitting diode L2, and a third light emitting diode L3.
The inlet wire of first way inserts the live wire A phase of first secondary winding, the outlet wire of first way inserts the one end of first main loop resistance R1, the other end of first main loop resistance R1 is connected with the one end of first fuse F1, the other end of first fuse F1 inserts the inlet wire end of first hole and is connected with the one end of first protection resistance R1, the other end of first protection resistance R1 is connected with the positive pole of first emitting diode L1, the negative pole of first emitting diode L1 is connected with the one end of fourth protection resistance R4, the other end of fourth protection resistance R4 is connected with the inlet wire end of fourth hole, the outlet wire of fourth hole inserts zero line n of first measurement circuit, the outlet wire a of first measurement circuit inserts the outlet wire end of first hole.
The wire inlet end of the second path is connected to the live wire B of the second secondary winding, the wire outlet end of the second path is connected to one end of a second main loop resistor R2, the other end of the second main loop resistor R2 is connected with one end of a second fuse F2, the other end of the second fuse F2 is connected to the wire inlet end of a second hole and one end of a second protection resistor R2, the other end of the second protection resistor R2 is connected with the positive electrode of a second light emitting diode L2, the negative electrode of the second light emitting diode L2 is connected with one end of a fourth protection resistor R4, the other end of the fourth protection resistor R4 is connected with the wire inlet end of a fourth hole, the wire outlet end of the fourth hole is connected to a zero line n of a second measurement loop, and the live wire B of the second measurement loop is connected to the wire outlet end of the second hole.
The wire inlet of the third path is connected to the live wire c of the third secondary winding, the wire outlet of the third path is connected to one end of a third main loop resistor R3, the other end of the third main loop resistor R3 is connected with one end of a third fuse F3, the other end of the third fuse F3 is connected to the wire inlet end of a third hole and one end of a third protection resistor R3, the other end of the third protection resistor R3 is connected with the positive electrode of a third light emitting diode L3, the negative electrode of the third light emitting diode L3 is connected with one end of a fourth protection resistor R4, the other end of the fourth protection resistor R4 is connected with the wire inlet end of a fourth hole, the wire outlet end of the fourth hole is connected to a zero wire n of a third measurement loop, and the wire outlet end of the third measurement loop is connected to the wire outlet end of the third hole.
The wire inlet end of the fourth path is respectively connected with the zero wires n of the first secondary winding, the second secondary winding and the third secondary winding, and the wire outlet end of the fourth path is connected with the wire inlet end of the fourth hole through a wire.
The current of the measuring loop of the voltage transformer sampling unit is not more than 1mA and even lower when the measuring loop works normally, and is similar to an open circuit state, and once the measuring loop is in interphase short circuit or single-phase grounding fault, the current is increased sharply. In order to meet the requirement of minimum volume, the first fuse F1, the second fuse F2 and the third fuse F3 in the invention select 5 x 20mm fuse tubes with minimum specification in the market, namely the fuse with rated current of 0.5A.
When the current passing through the fuse is smaller than the rated current, the fuse cannot be fused, and only when the rated current is exceeded and the fused current is reached, the fuse can be heated and fused. The greater the current through the fuse, the faster the fuse blows. Generally, when the current flowing through the fuse is 2 times the rated current, the fuse should be fused within 30 seconds; when the rated current is 5 times of the rated current, the electric motor should be instantaneously fused. In order to ensure that the fuse is instantaneously and reliably fused when an interphase or single-phase grounding fault occurs and avoid misoperation caused by starting an inductive load, the invention selects the rated current which is 2.5A current and is 5 times of the rated current.
When the measuring circuit has interphase short circuit fault (such as A, B interphase short circuit), the equivalent circuit diagram is shown in fig. 2:
uab=100v, i=2.5a, finding r1=r2=0.5×uab/i=20Ω,
wherein: uab is the effective value of the line voltage of the secondary winding of the voltage transformer; i is the set fuse current value.
When a single-phase earth fault occurs in the measurement loop (such as phase a is grounded), the equivalent circuit diagram is shown in fig. 3:
knowing ua=58v, i=2.5a, finding r1=ua/i=23.2Ω,
wherein: ua is the effective value of the phase voltage of the secondary winding of the voltage transformer; i is the set fuse current value.
By combining the two fault modes, a 20Ω resistor (formed by connecting two 10Ω resistors in series) is selected as a main loop resistor, namely, the resistance values of the first main loop resistor R1, the second main loop resistor R2 and the third main loop resistor R3 are 20Ω.
In order to meet the requirement that the working current of the light-emitting diode is 20mA, the protection resistors r1, r2, r3 and r4 are selected as shown in fig. 4:
i1=i2=i3=20ma, ean=58v, r1=r2=r3,
the following equation can be used: uan =i1×r1+3×i1×r4,
according to the specifications and equation constraint conditions of the existing resistors in the market, 2400 omega resistors are selected as r1, r2 and r3, and 120 omega resistors are selected as r4.
Claims (3)
1. A short-circuit prevention device for a secondary winding of a voltage transformer is arranged between the secondary winding of the voltage transformer and a measuring loop of a sampling unit of the voltage transformer, and is characterized in that: the air switch comprises an air switch (QF), a wiring terminal (J) and a protection circuit board, wherein the protection circuit board comprises a main loop resistor, a protection resistor, a light emitting diode and a fuse; the wire inlet end of the air switch (QF) is connected with the live wire and the zero wire of the secondary winding of the voltage transformer, the wire outlet end of the air switch (QF) is connected with one end of the main loop resistor, the other end of the main loop resistor is connected with one end of the fuse, the other end of the fuse is connected with one end of the protection resistor or the positive electrode of the light emitting diode while being connected with the wire inlet end of the wiring terminal (J), the other end of the protection resistor or the negative electrode of the light emitting diode is connected with the wire inlet end of the wiring terminal (J), and the wire outlet end of the wiring terminal (J) is connected with the live wire and the zero wire of the voltage transformer sampling unit measuring loop;
the voltage transformer comprises a first secondary winding, a second secondary winding and a third secondary winding, wherein the first secondary winding comprises a live wire (A) and a zero wire (N), the second secondary winding comprises a live wire (B) and a zero wire (N), and the third secondary winding comprises a live wire (C) and a zero wire (N);
the voltage transformer sampling unit measuring circuit comprises a first measuring circuit, a second measuring circuit and a third measuring circuit, wherein the first measuring circuit comprises a live wire (a) and a zero wire (n), the second measuring circuit comprises a live wire (b) and a zero wire (n), and the third measuring circuit comprises a live wire (c) and a zero wire (n);
the air switch (QF) comprises a first path, a second path, a third path and a fourth path;
the wiring terminal (J) comprises a first hole, a second hole, a third hole and a fourth hole;
the main loop resistances include a first main loop resistance (R1), a second main loop resistance (R2), and a third main loop resistance (R3);
the protection resistor comprises a first protection resistor (r 1), a second protection resistor (r 2), a third protection resistor (r 3) and a fourth protection resistor (r 4);
the fuse includes a first fuse (F1), a second fuse (F2), and a third fuse (F3);
the light emitting diodes include a first light emitting diode (L1), a second light emitting diode (L2), and a third light emitting diode (L3);
the wire inlet end of the first path is connected to the live wire (A) of the first secondary winding, the wire outlet end of the first path is connected to one end of the first main loop resistor (R1), the other end of the first main loop resistor (R1) is connected with one end of the first fuse (F1), the other end of the first fuse (F1) is connected to the wire inlet end of the first hole and one end of the first protection resistor (R1), the other end of the first protection resistor (R1) is connected with the positive electrode of the first light emitting diode (L1), the negative electrode of the first light emitting diode (L1) is connected with one end of the fourth protection resistor (R4), the other end of the fourth protection resistor (R4) is connected with the wire inlet end of the fourth hole, the wire outlet end of the fourth hole is connected to the zero wire (n) of the first measurement loop, and the wire outlet end of the first measurement loop is connected to the wire outlet end of the first hole;
the wire inlet end of the second path is connected to the live wire (B) of the second secondary winding, the wire outlet end of the second path is connected to one end of the second main loop resistor (R2), the other end of the second main loop resistor (R2) is connected with one end of the second fuse (F2), the other end of the second fuse (F2) is connected to the wire inlet end of the second hole and one end of the second protection resistor (R2), the other end of the second protection resistor (R2) is connected with the positive electrode of the second light emitting diode (L2), the negative electrode of the second light emitting diode (L2) is connected with one end of the fourth protection resistor (R4), the other end of the fourth protection resistor (R4) is connected with the wire inlet end of the fourth hole, the wire outlet end of the fourth hole is connected to the zero wire (n) of the second measurement loop, and the live wire (B) of the second measurement loop is connected to the wire outlet end of the second hole;
the wire inlet end of the third path is connected to the live wire (C) of the third secondary winding, the wire outlet end of the third path is connected to one end of the third main loop resistor (R3), the other end of the third main loop resistor (R3) is connected with one end of the third fuse (F3), the other end of the third fuse (F3) is connected to the wire inlet end of the third hole and one end of the third protection resistor (R3), the other end of the third protection resistor (R3) is connected with the positive electrode of the third light emitting diode (L3), the negative electrode of the third light emitting diode (L3) is connected with one end of the fourth protection resistor (R4), the other end of the fourth protection resistor (R4) is connected with the wire inlet end of the fourth hole, the wire outlet end of the fourth hole is connected to the zero wire (n) of the third measurement circuit, and the live wire (C) of the third measurement circuit is connected to the wire outlet end of the third hole;
the wire inlet end of the fourth path is respectively connected with the zero wires (N) of the first secondary winding, the second secondary winding and the third secondary winding, and the wire outlet end of the fourth path is connected with the wire inlet end of the fourth hole through a wire.
2. The voltage transformer secondary winding short circuit prevention device according to claim 1, wherein:
rated currents of the first fuse (F1), the second fuse (F2) and the third fuse (F3) are all 0.5A;
the resistance values of the first main loop resistor (R1), the second main loop resistor (R2) and the third main loop resistor (R3) are all 20Ω;
the resistance values of the first protection resistor (r 1), the second protection resistor (r 2) and the third protection resistor (r 3) are 2400 omega, and the resistance value of the fourth protection resistor (r 4) is 120 omega;
the working currents of the first light emitting diode (L1), the second light emitting diode (L2) and the third light emitting diode (L3) are 20mA.
3. The voltage transformer secondary winding short circuit prevention device according to claim 1, wherein: the air switch (QF), the wiring terminal (J) and the protection circuit board are respectively fixed on the epoxy resin board.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201710432223.9A CN107132463B (en) | 2017-06-09 | 2017-06-09 | Short circuit preventing device for secondary winding of voltage transformer |
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| CN201710432223.9A CN107132463B (en) | 2017-06-09 | 2017-06-09 | Short circuit preventing device for secondary winding of voltage transformer |
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| CN108107358A (en) * | 2018-01-25 | 2018-06-01 | 国网江苏省电力有限公司徐州供电分公司 | Portable voltage mutual inductor auxiliary air closing detecting apparatus and method of discrimination |
| CN108429242A (en) * | 2018-03-31 | 2018-08-21 | 苏州风中智能科技有限公司 | A kind of protector of electronic component |
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| CN203305936U (en) * | 2013-06-18 | 2013-11-27 | 苏州力特奥维斯保险丝有限公司 | Relay control unit |
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