When working in high-current AC voltage circuits, it becomes necessary to use compact devices with which you can use the non-contact method to control the necessary parameters. For these purposes, a current transformer is widely used, which, in addition to measuring, performs an additional number of useful functions. Such devices are manufactured on an industrial scale and have a wide variety of designs. Distinctive properties of these devices are the measuring range, the degree of protection of the device itself and its design features.
A 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, accordingly, the greater the current flows in the conductor. It remains only to recalculate the gain of the device and give the selected signal to the control, control or protection circuit.
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 the plot of the graph, which determine 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 galvanic separation of power and control circuits. This is important for security reasons. 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 supplied in a protection or control circuit based on modern electronic devices. Using them is easy.
make an emergency shutdown of the power lines and view the pre-emergency history. Such devices monitor the state of the network and calculate all the necessary parameters:
active / reactive power, current, power consumption, etc.
In the design process, the task arises: to select devices for monitoring and measurement. The selection of current transformers is based on the average design parameters of the operating network and the design features of the measuring device itself. Usually 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 lives. Sensitive devices protect expensive equipment and are responsible for human safety. They work perfectly in electrical circuits, providing control over the measured parameters.