CN102169754A - Current and voltage transformer - Google Patents

Abstract

The invention provides a current and voltage transformer, relates to the field of power grids, and is invented for solving the technical problem of monitoring power equipment of a smart grid. The current and voltage transformer includes: a first current transformer, including: a first coil wound on the iron core for passing a high-voltage transmission line, and the two ends of the first coil output current signals for measurement; The first resistor is connected to the two ends of the first coil; the voltage transformer includes: a high-voltage arm resistor, the first end of the high-voltage arm resistor is connected to the high-voltage power line; a low-voltage arm resistor, the low-voltage arm resistor The first end of the resistor is connected to the ground, the second end of the low-voltage arm resistor is connected to the second end of the high-voltage arm resistor, and the output between the first end and the second end of the low-voltage arm resistor is used for measurement. voltage signal. The invention can be used for the management of smart grid.

Description

current voltage transformer

technical field

The invention relates to the field of transformers, in particular to a current and voltage transformer.

Background technique

With the advancement of smart grid construction, how to monitor the power equipment of smart grid online has become an urgent problem to be solved. In the construction process of the smart grid, real-time monitoring of the operating parameters of the power grid is the basis, and the measurement of the current and voltage of the high-voltage line is the basis of the foundation. Only when the measurement of the voltage and current is realized can the power, harmonics and other parameter. The current measurement method mainly uses electromagnetic transformers, and its defect is that the output signal is very strong. For example, the current transformer outputs a current signal of 1 ampere or 5 amperes, and the voltage transformer outputs a 100V AC signal. These output signals cannot be directly transmitted to the back-end monitoring equipment and instruments, but need to be converted twice to reduce the signal to a voltage signal of about 5V that can be measured by electronic equipment before analog-to-digital conversion (AD conversion). In this way, due to the increase of the secondary conversion, the measurement accuracy will be reduced; it will also make the system more complicated and the failure rate will increase.

Contents of the invention

The technical problem to be solved by the present invention is to provide a current and voltage transformer, which can monitor the power equipment of the smart grid, and the output signal is relatively small, which can be directly transmitted to the subsequent monitoring equipment.

In order to solve the above technical problems, embodiments of the present invention provide technical solutions as follows:

In one aspect, a current and voltage transformer is provided, comprising:

The first current transformer includes: a first coil wound on the iron core for passing through the high-voltage transmission line, and the two ends of the first coil output current signals for measurement; a first resistor connected to the first coil two ends of a coil;

The voltage transformer includes: a high-voltage arm resistance, the first end of which is connected to the high-voltage transmission line; a low-voltage arm resistance, whose first end is connected to the ground, and the low-voltage arm The second end of the resistor is connected to the second end of the high-voltage arm resistor, and a voltage signal for measurement is output between the first end and the second end of the low-voltage arm resistor.

The first coil is made of a plurality of wires wound in parallel, a flexible cable braided by a plurality of wires, a hollow copper tube or a hollow aluminum tube.

The iron core is made of iron-based nanocrystalline ribbon material.

The resistance value of the first resistor is between 30-100 ohms.

The current and voltage transformer also includes: a second current transformer, including:

The second coil wound on the frame is used for passing through the high-voltage transmission line, and the two ends of the second coil output the second protection current signal; the second coil is arranged parallel to the first coil; the The skeleton is a non-magnetic material;

The second resistor is connected to both ends of the second coil.

The resistance values of the high voltage arm resistor and the low voltage arm resistor are between 5MΩ-100MΩ.

In another aspect, a current and voltage transformer is provided, comprising:

The first current transformer includes: a first coil wound on the iron core for passing through the high-voltage transmission line, and the two ends of the first coil output current signals for measurement; a first resistor connected to the first coil two ends of a coil;

The voltage transformer includes: a high-voltage arm resistance, the first end of which is connected to the high-voltage transmission line; a low-voltage arm resistance, whose first end is connected to the ground, and the low-voltage arm The second end of the resistor is connected to the second end of the high-voltage arm resistor, and a voltage signal for measurement is output between the first end and the second end of the low-voltage arm resistor;

Two hollow cylinders; the first hollow cylinder is arranged on the second hollow cylinder, the axis of the first hollow cylinder is parallel to the ground; the axis of the second hollow cylinder is perpendicular to the ground;

The first coil is arranged in the cavity of the first hollow cylinder, and the first coil is parallel to the bottom surface of the first hollow cylinder, so that the high-voltage transmission line passes through the first hollow the cavity of the cylinder and said first coil;

The first resistor, the high voltage arm resistor and the low voltage arm resistor are arranged in the cavity of the second hollow cylinder;

The two hollow cylinders consist of insulating material.

The current and voltage transformer also includes: a second current transformer, including: a second coil wound on the skeleton for passing through the high-voltage transmission line, and the two ends of the second coil output the second protection current signal; the second coil is arranged parallel to the first coil; the skeleton is a non-magnetic material;

a second resistor connected to both ends of the second coil;

The second coil is arranged in the cavity of the first hollow cylinder; the second resistor is arranged in the cavity of the second hollow cylinder.

Embodiments of the present invention have the following beneficial effects:

In the above solution, a current and voltage transformer is provided, which can output current signals and voltage signals respectively, and can monitor the power equipment of the smart grid online. Compared with the method of using electromagnetic transformers in the prior art, the output signal It is relatively small and can be directly transmitted to subsequent monitoring equipment.

Description of drawings

Fig. 1 is the schematic diagram of the circuit principle of the current voltage transformer described in the present invention;

Fig. 2 is the front view of the current and voltage transformer described in the present invention;

Fig. 3 is a side view of the current and voltage transformer of the present invention;

Fig. 4 is a top view of the current and voltage transformer of the present invention;

5 is a perspective view of the current and voltage transformer of the present invention;

Fig. 6 is an application scenario of the current and voltage transformer described in the present invention.

Detailed ways

In order to make the technical problems, technical solutions and advantages to be solved by the embodiments of the present invention clearer, the following will describe in detail with reference to the drawings and specific embodiments.

As shown in Figure 1, it is a schematic diagram of a circuit principle of a current and voltage transformer according to the present invention, including:

The first current transformer includes: a first coil 4 wound on the iron core for passing through the high-voltage transmission line 1, and the two ends of the first coil 4 output current signals for measurement; the first resistor 5 is connected to at both ends of the first coil 4;

A voltage transformer, comprising: a high-voltage arm resistor 10, the first end of which is connected to the high-voltage transmission line 1; a low-voltage arm resistor 8, whose first end is connected to the ground , the second end of the low-voltage arm resistor 8 is connected to the second end of the high-voltage arm resistor 10, and a voltage signal for measurement is output between the first end and the second end of the low-voltage arm resistor 8.

The first coil 7 is made of a plurality of wires wound in parallel, a flexible cable braided by a plurality of wires, a hollow copper tube or a hollow aluminum tube.

The iron core is made of iron-based nanocrystalline ribbon material.

The resistance value of the first resistor 8 is between 30-100 ohms.

The current and voltage transformer also includes: a second current transformer, including:

The second coil 2 wound on the frame is used for the high-voltage transmission line 1 to pass through, and the two ends of the second coil 2 output the second protection current signal; the second coil 2 is parallel to the first coil 4 settings; the skeleton is a non-magnetic material;

The second resistor 7 is connected to both ends of the second coil.

The resistance values of the high voltage arm resistor 10 and the low voltage arm resistor 8 are between 5MΩ-100MΩ.

Fig. 1 shows two sets of first current transformers and two sets of voltage transformers.

The real object of the current and voltage transformer according to the present invention will be described below with reference to FIG. 2 to FIG. 5 . Fig. 2 is the front view of current voltage transformer according to the present invention; Fig. 3 is the side view of current voltage transformer according to the present invention; Fig. 4 is the top view of current voltage transformer according to the present invention; Fig. 5 is The perspective view of the current and voltage transformer of the present invention; the current and voltage transformer includes:

Two hollow cylinders; the first hollow cylinder 20 is arranged on the second hollow cylinder 30, the axis of the first hollow cylinder 20 is parallel to the ground; the axis of the second hollow cylinder 30 is perpendicular to the ground;

The first coil 4 is arranged in the cavity of the first hollow cylinder 20, and the first coil 4 is parallel to the bottom surface of the first hollow cylinder 20, so that the high-voltage transmission line 1 passes through The cavity of the first hollow cylinder 20 and the first coil 4;

The first resistor 5, the high voltage arm resistor 10 and the low voltage arm resistor 8 are arranged in the cavity of the second hollow cylinder 30;

The two hollow cylinders 30, 20 consist of insulating material.

The second coil 2 is arranged in the cavity of the first hollow cylinder 20 ; the second resistor 7 is arranged in the cavity of the second hollow cylinder 30 .

The voltage transformer also includes: a shielding electrode (not shown in the figure), which is arranged outside the high voltage arm resistor 10 .

The voltage transformer also includes: an overvoltage protection device (not shown in the figure), the first end of the overvoltage protection device is connected to the second end of the low-voltage arm resistor 8, and the overvoltage protection device The second end is connected to the first end of the low-voltage arm resistor 8 . The overvoltage protection device is disposed in the cavity of the second hollow cylinder 30 .

The invention provides an integrated electronic current and voltage transformer specially used for overhead power distribution lines. It has built-in 3 sets of coils and 2 sets of voltage dividers, which have the following beneficial effects:

(1) It can directly replace the post insulator on the utility pole

(2), Built-in current transformer, the output is an electronic signal (4V, no power)

(3) The current transformer part can output two sets of current signals for measurement (0~500A, 0.2%), and one set of current signals for protection (0~20kA, 3%)

(4), built-in voltage transformer, the output is an electronic signal (2V, no power)

(5) The voltage transformer part can output two sets of voltage signals for measurement (0~45kV, 0.2%)

(6) It can be made into an open type, which is easy to install.

The principle of the electronic current transformer is described below.

In the present invention, the electronic current transformer adopts the principle of Rogowski coil and light load coil (LPCT). The Rogowski coil is used to measure large current signals for relay protection, and the linear range of the measurable current can reach up to 20kA. Using LPCT to measure the working current for metering and measurement, the linear range is 0~630A.

Because the Rogowski coil adopts a non-magnetic skeleton, there is no magnetic saturation phenomenon. When the primary current passes through the Rogowski coil, the coil generates a secondary voltage E proportional to the time differential of the primary current I1. By time-integrating the secondary voltage E, a voltage signal U proportional to the primary current can be obtained. The signal U is converted and processed by the microprocessor, and the primary current information can be converted into analog and digital output.

The light-duty coil consists of a primary winding, a small iron core and a secondary winding to minimize losses. The secondary winding is connected with the sampling resistor R, and the voltage drop U2 of the secondary current I2 at both ends of the sampling electric group R is proportional to the primary current I1. The LPCT core is made of microcrystalline amorphous alloy, which has the characteristics of high magnetic permeability, high sensitivity and no hysteresis.

The principle of the electronic voltage transformer is described below.

Electronic voltage transformers work in the way of resistive voltage division. EVT (voltage transformer) is composed of high-voltage arm resistance, low-voltage arm resistance, shielding electrode, and overvoltage protection device. The primary voltage is converted into a small voltage signal proportional to the primary voltage and phase through a voltage divider. Shielding electrodes are used to improve the electric field distribution and the influence of stray capacitance. A highly sensitive overvoltage protection device is connected in parallel at the secondary output terminal to prevent the secondary side voltage from increasing when the secondary output terminal is open.

The following describes the application of ECT (current transformer) and EVT in the power system. As shown in Figure 6, it is the application of EVT and ECT in the digital substation. In the construction of digital substation, the voltage signal measured by EVT and the current signal measured by ECT can be directly sent to the acquisition unit, and the current and voltage signals are directly converted into digital signals in the acquisition unit. Then the digital signal is sent to the combiner through the bus, and finally sent to the monitoring software of the digital substation for further metering, measurement and protection.

Electronic transformers are an important technical support for the construction of digital substations, and also have broad application prospects in the fields of power measurement and protection. Compared with traditional electromagnetic transformers, electronic current and voltage transformers have the following advantages.

(1) Wide measurement range.

The electronic transformer has a wide frequency response range, a wide measurement linear range, and good linearity. Within the effective range, the accuracy level of the current transformer can reach 0.2S/5P level, and the measurement accuracy level of the voltage transformer can reach 0.2/3p level.

(2), flexible application.

Electronic transformers output small voltage signals, generally 1.5V to 4V. This signal can be easily interfaced with digital instruments and microcomputer measurement, control and protection equipment without secondary conversion, which can reduce the complexity of system applications. The measurement error is reduced, and the stability and accuracy of the equipment are improved.

(3), safe and reliable.

Electronic transformers do not contain iron cores (or contain small iron cores), and there will be no saturation phenomenon. Even when the current transformer is opened for the second time, it will not generate high voltage, and when the voltage transformer is short-circuited for the second time, it will not generate a large current, there is no danger of over-current breakdown, and there will be no ferromagnetic resonance, thus ensuring personal safety Equipment Security.

(4) Small size and low power consumption.

The electronic transformer is small in size and light in weight, can effectively save space, consumes very little power, and has a very significant power-saving effect. It has the characteristics of an environmentally friendly product.

(5), multi-purpose.

The electronic current transformer integrates measurement and protection, and can quickly, completely and accurately transmit primary information to the computer for data processing or connect with digital instruments and other measurement and protection devices to realize metering, measurement, protection, control, status monitor. The electronic voltage transformer is also used as a live display device to realize digital on-line monitoring of primary voltage, and can also be used as a supporting insulator.

(6), long service life.

Since the electronic transformer itself has low power consumption, its own coil will not generate heat, which ensures the service life of the transformer. It is easy to install and use, requires no maintenance in operation, and has a service life of more than 30 years.

The following table compares traditional electromagnetic transformers with electronic current and voltage transformers:

The output signal of the electronic current voltage transformer of the present invention can be a 4V electronic signal, which avoids secondary conversion and can be directly transmitted to subsequent monitoring equipment. The current and voltage transformers of the present invention are combined into one, the volume and weight are greatly reduced, the manufacturing cost can be reduced, and more convenience is provided to users in actual installation and use.

In the application scenario shown in Figure 1, the output signal of the current and voltage transformer of the present invention is a multi-channel electronic analog signal, including two channels of current secondary signals for measurement, one channel of current secondary signals for protection; There are two secondary signals. All output signals are isolated independently. This output signal is suitable for measurement and fault monitoring of distribution lines. It can realize the measurement of zero-sequence current and zero-sequence voltage of overhead lines. It can be used for the monitoring of overhead line short circuit and ground fault.

In practical applications, the current secondary signal for the first measurement is used for current measurement, and the current secondary signal for the second measurement can be connected end to end, so that the zero-sequence current signal of the line is obtained, and the zero-sequence current The signal can be used to detect single-phase-to-earth faults on distribution lines. The current secondary signal for protection is used to measure the large current (up to 20,000 amperes) that passes instantaneously when a short circuit or overcurrent fault occurs in the line.

The secondary voltage signal for measuring the first channel is used to measure the voltage of the line. The secondary voltage signal for the second measurement is connected to the common end of the ground, and a resistor with a suitable resistance is connected in series, and the other end of the resistor is connected to the ground, so that the zero sequence can be measured on the small resistor connected in series. voltage signal. This method can solve the problem that the overhead distribution line cannot measure zero-sequence voltage and zero-sequence current.

The current and voltage transformer of the invention is suitable for the measurement and fault monitoring of overhead power distribution lines. It can be used in conjunction with energy metering, pole-mounted switch controllers, high-voltage reactive power compensation devices, and other equipment.

The above description is a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. a current-voltage transformer is characterized in that, comprising:

First current transformer comprises: first coil on the iron core, be used for passing for high voltage transmission line, and the two ends output of described first coil is measured and is used current signal; First resistance is connected the two ends of described first coil;

Voltage transformer comprises: high-voltage arm resistance, and first end of described high-voltage arm resistance is connected with described high voltage transmission line; Low-voltage arm resistance, first end of described low-voltage arm resistance be connected describedly, second end of described low-voltage arm resistance is connected with second end of described high-voltage arm resistance, output is measured and to be used voltage signal between first end of described low-voltage arm resistance and second end.

2. current-voltage transformer according to claim 1 is characterized in that, described first coil by and around flexible cable, hollow copper tubing or the hollow aluminum pipe of multiple conducting wires, multiple conducting wires braiding make.

3. current-voltage transformer according to claim 1 is characterized in that described iron core is made of the iron based nano crystal carrying material.

4. current-voltage transformer according to claim 1 is characterized in that the resistance of described first resistance is between 30-100 ohm.

5. current-voltage transformer according to claim 1 is characterized in that, also comprises: the one the second current transformers comprise:

Second coil on the skeleton is used for passing for high voltage transmission line, the two ends output second protection current signal of described second coil; Described second coil is parallel to the described first coil setting; Described skeleton is a nonmagnetic substance;

Second resistance is connected the two ends of described second coil.

6. current-voltage transformer according to claim 5 is characterized in that,

The resistance of described high-voltage arm resistance and described low-voltage arm resistance is between 5M Ω-100M Ω.

7. current-voltage transformer according to claim 1 is characterized in that, described voltage transformer also comprises: bucking electrode is arranged on the outside of high-voltage arm resistance.

8. according to each described current-voltage transformer of claim 1 to 7; it is characterized in that; described voltage transformer also comprises: overvoltage protection; first end of described overvoltage protection is connected with second end of described low-voltage arm resistance, and second end of described overvoltage protection is connected with first end of described low-voltage arm resistance.

9. a current-voltage transformer is characterized in that, comprising:

First current transformer comprises: first coil on the iron core, be used for passing for high voltage transmission line, and the two ends output of described first coil is measured and is used current signal; First resistance is connected the two ends of described first coil;

Voltage transformer comprises: high-voltage arm resistance, and first end of described high-voltage arm resistance is connected with described high voltage transmission line; Low-voltage arm resistance, first end of described low-voltage arm resistance be connected describedly, second end of described low-voltage arm resistance is connected with second end of described high-voltage arm resistance, output is measured and to be used voltage signal between first end of described low-voltage arm resistance and second end;

Two hollow circular cylinders; First hollow circular cylinder is arranged on second hollow circular cylinder, and the parallel axes of described first hollow circular cylinder is in ground; The axis normal of described second hollow circular cylinder is in ground;

Described first coil is arranged in the cavity of described first hollow circular cylinder, and described first coil is parallel to the bottom surface of described first hollow circular cylinder, makes described high voltage transmission line pass the cavity and described first coil of described first hollow circular cylinder;

Described first resistance, described high-voltage arm resistance and described low-voltage arm resistance are arranged in the cavity of described second hollow circular cylinder;

Described two hollow circular cylinders are made up of insulating material.

10. current-voltage transformer according to claim 9 is characterized in that, also comprises: second current transformer comprises:

Second coil on the skeleton is used for passing for high voltage transmission line, the two ends output second protection current signal of described second coil; Described second coil is parallel to the described first coil setting; Described skeleton is a nonmagnetic substance;

Second resistance is connected the two ends of described second coil;

Described second coil is arranged in the cavity of described first hollow circular cylinder; Described second resistance is arranged in the cavity of described second hollow circular cylinder.

Images