CN204679581U - A kind of portable type current transformer polarity test device - Google Patents

Abstract

The utility model relates to a portable current transformer polarity testing device, and its technical scheme is: a switch is arranged outside the casing, a CT winding is arranged inside the casing, a power supply is connected to the CT winding through a switch, and a CT winding is arranged outside the casing. Primary side test terminal L1, L2 and secondary side test terminal K1, K2, primary side test terminal L1, L2 and secondary side test terminal K1, K2 are respectively connected to CT windings, secondary side test terminal K1, K2 is provided with a secondary side circuit, and the secondary side circuit formed on the secondary side test terminals K1 and K2 is connected in reverse parallel with the first light-emitting diode and the second light-emitting diode; the beneficial effect of the utility model is: in ensuring CT On the basis of the accuracy of the polarity test, it not only improves the integration of the test circuit, highlights its portability, but also optimizes the way of polarity discrimination.

Description

A portable current transformer polarity testing device

technical field

The utility model relates to a current transformer polarity testing device, in particular to a portable current transformer polarity testing device.

Background technique

The current transformer (hereinafter referred to as CT, Current Transformer) is one of the most important power components in the power system. It can convert the large current on the primary side of the power system into a secondary current for protection, measurement, and metering through alternating magnetic flux. , recording and broadcasting and other secondary circuits. Once the polarity of the CT secondary side circuit is reversed, it is very likely that some protection devices (functions) with direction discrimination conditions will refuse to operate or malfunction, thus causing harm to the safe and stable operation of the power grid. Therefore, before the newly installed CT is put into operation or after the secondary cable of the CT is replaced, timely testing the polarity of the above-mentioned CT is an indispensable part of the work of the relay protection staff.

At present, the CT winding polarity testing methods commonly used by relay protection workers in the power sector mainly include the DC method and the instrument method (that is, using a complete set of transformer calibrator to test the CT winding polarity). Among them, the DC method is more respected by on-site staff because of its relatively cheap components (Class A battery, single or multi-strand soft copper wire, DC mA meter) and intuitive and easy-to-understand principles. However, limited by the natural properties of the above-mentioned components and the design principle of the test circuit, it inevitably has the following defects: 1) Type A batteries and DC mA meters are bulky and difficult to carry, and the integration of the test circuit is poor; 2) due to It is necessary to observe the positive and negative bias of the DC mA meter in real time. The operation process requires the cooperation of multiple staff, which is time-consuming and laborious and inefficient; 3) Due to the fixed range of the DC mA meter, it is difficult to guarantee the test sensitivity.

Contents of the invention

The purpose of this utility model is to provide a portable current transformer polarity testing device for the above-mentioned defects in the prior art.

Its technical solution is: including shell, switch, power supply, CT winding, the outside of the shell is equipped with a switch, the inside of the shell is equipped with CT winding, the power supply is connected to the CT winding through the switch, and the outside of the shell is equipped with a primary side test wiring Columns L1, L2 and secondary side test terminal K1, K2, primary side test terminal L1, L2 and secondary side test terminal K1, K2 are respectively connected to CT windings, secondary side test terminal K1, K2 are equipped with The secondary side circuit, the first light emitting diode and the second light emitting diode are connected in antiparallel to the secondary side circuit formed by the secondary side test terminals K1 and K2.

The above-mentioned second light-emitting diode is provided with a current-limiting resistor.

The beneficial effects of the utility model are: on the basis of ensuring the accuracy of the CT polarity test, it not only improves the integration of the test circuit, highlights its portability, but also optimizes the way of polarity discrimination, making it more intuitive and easy to detect. affected by human factors. It ensures the safe and stable operation of power grid equipment, especially relay protection devices, and improves the overall reliability of power supply.

Description of drawings

Accompanying drawing 1 is the structural representation of the utility model;

Accompanying drawing 2 is the circuit structure diagram of the utility model.

Detailed ways

In conjunction with accompanying drawings 1-2, the utility model is further described:

The utility model includes a housing 1, a switch S, a power supply E, and a CT winding. The outside of the housing is provided with a switch S, and the inside of the housing is provided with a CT winding. The power supply E is connected to the CT winding through the switch S. The outside of the housing is provided with Primary side test terminal L1, L2 and secondary side test terminal K1, K2, primary side test terminal L1, L2 and secondary side test terminal K1, K2 are respectively connected to CT winding, secondary side test terminal K1, K2 is provided with a secondary side circuit, and the secondary side circuit formed by the secondary side test terminals K1 and K2 is connected in reverse parallel with the first light emitting diode LED1 and the second light emitting diode LED2.

Wherein, a current limiting resistor R is provided on the second light emitting diode LED2.

The usage method of the portable current transformer polarity testing device mentioned in the utility model comprises the following steps:

A) In the test device circuit, L1 and K1 are the polarity ends of the primary side circuit and the secondary side circuit of the CT winding respectively. When the current in the primary side circuit flows from L1 to L2, the current in the secondary side circuit flows from K2 to K1. If the polarity is reduced, the green light of the first light-emitting diode LED1 is on, indicating that the polarity connection is correct; otherwise, the polarity is added, and the red light of the second light-emitting diode LED2 is on, indicating that the polarity is reversed;

B) The first light-emitting diode LED1 and the second light-emitting diode LED2 connected in antiparallel in the secondary side circuit of the CT winding can emit red light and green light respectively when they are turned on, which are used to indicate the polarity addition and depolarization of the CT winding . There is also a multi-level adjustable current-limiting resistor connected in series with the second light-emitting diode LED2 of the CT winding, which is used to prevent the light-emitting diode from being damaged by excessive induced current or high reverse voltage in the loop when the transformation ratio of the CT winding changes;

C) According to the typical working voltage of the light-emitting diode is 0.7V, the light-emitting diode cannot indicate normally when it is lower than 0.4V, and it is easy to be broken down when it is higher than 1.4V. According to the formula:

The resistance value R of the current-limiting resistor that needs to be connected in series in the secondary circuit of the CT winding can be calculated. Among them, V ₂ is the working voltage required by the anti-parallel light-emitting diodes; I ₂ is the secondary side current of the CT winding; V ₁ is the primary side voltage of the CT winding; R ₁ is the typical value of the primary side impedance of the CT winding provided by the CT manufacturer ; It is the transformation ratio coefficient of CT, and it is enough to ensure that the voltage applied to both ends of the light-emitting diode can always fall within its normal working voltage range through the current-limiting resistor R;

D) Use small and easy-to-integrate batteries to replace Type A batteries in series into the primary side circuit of the CT winding. The primary side test terminal L1, L2 and the secondary side test terminal K1, K2, a total of 4 terminals, are painted with different colors. Distinguish, used to connect the polarity terminal and non-polarity terminal of CT primary side and secondary side respectively, a test start-stop switch, used to control the start-stop of the device, two light-emitting diodes that can emit green light and red light respectively It must also protrude out of the shell to facilitate observation and judgment of CT polarity.

Claims (2)

1. a portable type current transformer polarity test device, it is characterized in that: comprise housing (1), switch S, power supply E, CT winding, the outside of housing is provided with switch S, the inside of housing (1) is provided with CT winding, power supply E connects CT winding by switch S, the outside of housing (1) is provided with primary side calibrating terminal L1, L2 and secondary side calibrating terminal K1, K2, primary side calibrating terminal L1, L2 and secondary side calibrating terminal K1, K2 connects CT winding respectively, secondary side calibrating terminal K1, K2 is provided with secondary side circuit, secondary side calibrating terminal K1, reverse parallel connection first LED 1 and the second LED 2 on the secondary side circuit of the upper composition of K2.

2. a kind of portable type current transformer polarity test device according to claim 1, is characterized in that: the second described LED 2 is provided with current-limiting resistance R.