How many open current transformers should be installed in the distribution box, do you know?
How many open current transformers should be installed in the distribution box, do you know?
The role of current transformers:
The current transformer is widely used in the power system. Its function is to induce a small current from the high-current cable according to a certain proportion, and then use it for instrument measurement and relay protection.
When we open the power distribution cabinet, we can see that there are many current transformers in it. Some power distribution cabinets have only one, and some even have five or six. In fact, they all induce current signals from the bus, but the measured currents have different effects. So what role do they all play in the power distribution cabinet?
A current transformer:
If there is only one current transformer, then this situation is generally used to take the current signal from a single line. For example, it is used to expand the range of single-phase electric meters, measure single-phase line current, measure three-phase balanced line current, and sample reactive power controller current.
Expanding the range of a single-phase meter mainly refers to the wiring of a current transformer and a single-phase transformer;
Measuring single-phase line current means using a current transformer to connect with an ammeter, and then measuring single-phase line current.
Measuring the current of a three-phase balanced line is the same as measuring the current of a single-phase line, because the currents of each phase of the three-phase balanced line are almost equal.
The purpose of connecting the reactive power controller and the current transformer is to obtain the current magnitude and phase signal from the bus through the current transformer.
Two current transformers:
If two current transformers are worn on the same phase bus, you can refer to the function of connecting one current transformer. If two current transformers are respectively worn on the two-phase bus, then its purpose is mainly to measure the three-phase current in the three-phase balanced line or the three-phase unbalanced line.
When the three phases are unbalanced, the three-phase current vector sum is zero. When we know the current of two phases, we can calculate the current of the other phase.
Three current transformers:
If three current transformers are used, they are generally mainly used to measure three-phase balanced and unbalanced currents; they can also be used to connect with three-phase inductance meters to measure how much electricity is used; they can also be connected to thermal relays to expand Range of thermal relays.
