CN104183379A - Connecting device for maintenance of secondary side of electric power current transformer - Google Patents

Abstract

The invention discloses a connection device for maintenance of the secondary side of a power current transformer, which comprises a first group of three-phase terminal ABCN, a second group of three-phase terminal A1B1C1N1 and three AC ammeters; the beneficial effect is that the current The connection device for secondary side maintenance of the transformer bypasses and detects the secondary side current of the current transformer, which simplifies the process of closing the CT; it can shorten the fault handling time, eliminate the potential safety hazard of closing the CT when the secondary circuit is live Personal and equipment injuries caused by accidentally touching live terminals or working without knowing whether the CT terminals are sealed; the device is low in cost, easy to use, and suitable for popularization and application.

Description

Connection device for maintenance of secondary side of power current transformer

technical field

The invention relates to the professional technical field of relay protection in electric power industry systems; in particular, it relates to a connection device for secondary side maintenance of power current transformers.

Background technique

The function of the current transformer (CT for short) used in the power industry system is to convert the primary current with a large value into a secondary current with a small value through a certain transformation ratio for protection, measurement and maintenance. and other purposes. For example, a current transformer with a transformation ratio of 400/5 can convert the actual 400A current into a 5A current. the

In the transmission lines of power generation, power transformation, power transmission, power distribution and power consumption, the size of the current varies greatly, ranging from a few amperes to tens of thousands of amperes. For the convenience of measurement, protection and control, it needs to be converted into a relatively uniform current. In addition, the voltage on the line is generally relatively high, and it is very dangerous to measure it directly. The current transformer plays the role of current conversion and electrical isolation.

For pointer ammeters, most of the secondary currents of current transformers are ampere-level, such as 5A, 10A, 20A, etc. For digital instruments, the sampled signal is generally milliamp level (0-5V, 4-20mA, etc.). The secondary current of the miniature current transformer is milliamp level, which mainly acts as a bridge between the large transformer and the sampling.

Similar to the transformer, the current transformer also works according to the principle of electromagnetic induction. The transformer transforms the voltage while the current transformer transforms the current. The winding of the current transformer connected to the measured current (the number of turns is N1) is called the primary winding (or primary winding, primary winding); the winding connected to the measuring instrument (the number of turns is N2) is called the secondary winding (or secondary winding) winding, secondary winding).

The current ratio of the current transformer primary winding current I1 to the secondary winding I2 is called the actual current ratio K. The current ratio of the current transformer when it works at the rated current is called the rated current ratio of the current transformer, expressed in Kn.

Kn=I1n/I2n

Current transformers (CT) are widely used in primary measurement and voltage protectors in power systems

control. During normal operation, the secondary side of the current transformer is in an approximate short-circuit state, and the output voltage is very low. During operation, if the secondary winding is open, or the primary winding flows through an abnormal current (such as lightning current, resonant overcurrent, capacitor charging current, inductive starting current, etc.), thousands of volts or even tens of thousands of volts will be generated on the secondary side. Overvoltage. This will not only cause damage to the insulation of the secondary system, but also cause the transformer to be overexcited and burn out, and even endanger the safety of the staff. Using the current transformer overvoltage protector can effectively prevent accidents caused by the secondary open circuit of the current transformer.

At present, with the improvement of the reliability of power supply, some relay protection work is required to be carried out under the condition that the secondary AC circuit is not powered off. Especially when dealing with urgent defects but the external power cannot be cut off, we need to carry out live work. First close the lower terminal of the current transformer secondary side protection terminal panel, and then perform the work of the secondary AC circuit on the terminal panel. Using the existing method, there are hidden dangers such as CT open circuit and accidental touching of live terminals in the process of sealing CT, which may easily lead to equipment damage and personal casualties.

Contents of the invention

The technical problem to be solved by the present invention is to provide a connection device for maintenance of the secondary side of a power current transformer.

The technical solution adopted in the present invention is a connection device for maintenance of the secondary side of a power current transformer, including the first group of three-phase binding posts ABCN, the second group of three-phase binding posts A1B1C1N1 and three AC ammeters; The first group of three-phase electricity phase A terminal is electrically connected to the input terminal of the first AC ammeter, and the second group of three-phase electricity A1 phase terminal is electrically connected to the output terminal of the first AC ammeter; the second group The three-phase electricity A2 phase terminal is electrically connected to the input terminal of the second AC ammeter, and the second group of three-phase electricity A2 phase terminal is electrically connected to the output end of the second AC ammeter; the third group of three-phase electricity A3 The phase terminal is electrically connected to the input terminal of the third AC ammeter, and the third group of three-phase electricity A3 phase terminal is electrically connected to the output terminal of the third AC ammeter; the first group of three-phase electricity N-phase terminal is electrically connected to the The second group of three-phase electricity N1 phase terminals are electrically connected.

The range of the three AC ammeters is 20A.

The beneficial effect of the present invention is that the current transformer secondary side maintenance connection device is used to bypass and detect the current transformer secondary side current, which simplifies the closed CT process; the fault processing time can be shortened, and the live operation of the secondary circuit is eliminated The potential safety hazard of closing the CT at the time avoids personal and equipment injuries caused by accidentally touching the live terminal or working without knowing whether the CT terminal is sealed; the device is low in cost, easy to use, and suitable for popularization and application.

Description of drawings

Fig. 1 is a schematic diagram of the composition and structure of the connection device for secondary side maintenance of the current transformer of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

As shown in Fig. 1, the connection device for maintenance of the secondary side of the power current transformer of the present invention includes a first group of three-phase binding posts ABCN, a second group of three-phase binding posts A1B1C1N1 and three AC ammeters;

The first group of three-phase electricity phase A terminal is electrically connected to the input terminal of the first AC ammeter, and the second group of three-phase electricity A1 phase terminal is electrically connected to the output terminal of the first AC ammeter;

The second group of three-phase electricity A2-phase terminal is electrically connected to the input terminal of the second AC ammeter, and the second group of three-phase electricity A2-phase terminal is electrically connected to the output terminal of the second AC ammeter;

The third group of three-phase electricity A3-phase terminal is electrically connected to the input terminal of the third AC ammeter, and the third group of three-phase electricity A3-phase terminal is electrically connected to the output terminal of the third AC ammeter;

The first group of three-phase power N-phase terminal is electrically connected to the second group of three-phase power N1-phase terminal.

The range of the three AC ammeters is 20A.

The CT connecting device of the present invention is composed of multi-strand test lines, connecting terminals and a small box of an ammeter. In order to connect with terminal blocks on the secondary side of different types of current transformers, the connecting plug of the device can be freely replaced with matching connecting terminals. There is an AC ammeter connected in series in the middle of the box, which can visually monitor whether the secondary side of the current transformer and the terminal block are electrically connected reliably through the meter information. For troubleshooting the fault of the secondary device, for example, the LCD screen cannot be displayed, the protection device The role of faults such as damage to the AC sampling board is particularly evident. When the four CT connecting wires A, B, C, and N are inserted into the terminals on the secondary side of the current transformer and pass through the ammeter, the ammeter will have a current indication. At this time, if the ammeter has no indication, it indicates that the CT is connected. The line and the terminal block under the panel of the protection device are not connected properly, and the connection wires of the terminal block under the panel need to be carefully checked for faults. Do not disconnect the CT connecting piece at this time, otherwise it will cause the terminal block of the CT to open circuit, and in serious cases, it will cause the protection device to malfunction.

The present invention adopts the connection device for secondary side maintenance of the current transformer to bypass and detect the current of the secondary side of the current transformer. Two groups of ABCN three-phase terminal posts are installed on both sides of the device, and are respectively connected through the connecting wires for testing. The secondary side of the current transformer is connected separately according to the corresponding phases, and the secondary side of the current transformer is maintained. Simplifies the closed CT process; can shorten the fault handling time, eliminates the potential safety hazard of closed CT during live operation of the secondary circuit, and avoids personal injury and equipment caused by accidentally touching the live terminal or working without knowing whether the CT terminal is sealed damage; the device is low in cost, easy to use, and suitable for popularization and application.

It is worth pointing out that the scope of protection of the present invention is not limited to the above-mentioned specific examples. According to the basic technical concept of the present invention, basically the same structure can also be used to achieve the purpose of the present invention, as long as those of ordinary skill in the art do not need to be creative Labor, that is, the conceivable implementation modes, all belong to the protection scope of the present invention.

Claims (2)

1. A connection device for secondary side maintenance of a power current transformer, characterized in that, comprising, the first group of three-phase binding posts ABCN, the second group of three-phase binding posts A1B1C1N1 and three AC ammeters; The first group of three-phase electricity phase A terminal is electrically connected to the input terminal of the first AC ammeter, and the second group of three-phase electricity A1 phase terminal is electrically connected to the output terminal of the first AC ammeter; The second group of three-phase electricity A2-phase terminal is electrically connected to the input terminal of the second AC ammeter, and the second group of three-phase electricity A2-phase terminal is electrically connected to the output terminal of the second AC ammeter; The third group of three-phase electricity A3-phase terminal is electrically connected to the input terminal of the third AC ammeter, and the third group of three-phase electricity A3-phase terminal is electrically connected to the output terminal of the third AC ammeter; The first group of three-phase power N-phase binding posts is electrically connected to the second group of three-phase power N1-phase binding posts. 2. The connection device for maintenance of the secondary side of a power current transformer according to claim 1, wherein the measuring range of the three AC ammeters is 20A.