When working in high-current AC voltage circuits, it becomes necessary to use compact devices that can be used to control the necessary parameters in a non-contact way. For these purposes, a current transformer is widely used, which, in addition to measuring, additionally performs a number of useful functions. Such devices are commercially available and have a variety of designs. Distinctive properties of these devices are the measurement range, the degree of protection of the device itself and its design features.
Modern current transformer uses in its work a simple principle known since the invention of electricity. When working under load in the conductor, it generates an electromagnetic field, which is captured by a sensitive device. The greater the intensity of the field, the correspondingly more current flows in the conductor. It remains only to recalculate the gain of the device and send the selected signal to the circuitcommand, control or protection.
Thus, the current transformer plays the role of a frame on the power cable and responds to changes in the supply network. Modern devices consist of a large number of turns and have a good transmission coefficient. When setting up such a device, the current-voltage characteristic is taken to determine the inflection point of the curve. This is necessary to find a section of the graph, which determines the range of stable operation of the device. The current transformer also has its own gain, which is specified during commissioning.
In addition to measuring functions, the device allows you to galvanically separate power and control circuits. This is important for security purposes. It is difficult to imagine a contact device that operates in electrical networks with a voltage of, say, 10,000 volts. Using modern measuring current transformers, it is possible to obtain a low power signal galvanically separated from the power circuit, which is convenient and safe to work with.
The load of such devices can be any measuring device capable of working with a measuring transformer. If the distance between them is so large that the internal resistance of the line begins to affect, then the device is calibrated. In addition, the measured signal can be fed into protection or control circuits based on modern electronic devices. With their help, it's easy
make an emergencydisconnect power lines and view the pre-accident history. Such devices monitor the state of the network and calculate all the necessary parameters: active / reactive power, current, power consumption, etc.
During the design process, a task arises: to select devices for control and measurement. The choice of current transformers is carried out on the basis of the average design parameters of the network in operation and the design features of the measuring device itself. Typically, powerful power plants come with measuring instruments, meaning: powerful power transformers, high-voltage panels, etc.
Without measuring devices, it is difficult to imagine modern production and our daily life. Sensitive devices protect expensive equipment and are responsible for human safety. They work great in electrical circuits, providing control over the measured parameters.
