A CT clamp (named Current Transformer Clamp) is a device for measuring electric current, which gives the direction of the flow. In fact, a CT clamp is a current clamp.
Clamp meters make no-contact current measurements by using wide jaws clamping around the outside of an electrical conductor. When the electric current flows in the circuit, the clamp meter converts the value to an AC reading.
The CT clamp, or Current Transducer, can either function as a feature of a multimeter or a stand-alone device connected to a transducer communication center. In view of that clamp meters have offered more measurement functions, greater accuracy, and in some cases specialized measurement features, clamp meters are preferred for measuring high levels of current. Nowadays clamp meters have most of the basic functions of a digital multimeter (DMM), such as the ability to measure voltage, continuity, and resistance.
With the application of the CT clamp meters more and more widely, CT clamps have become a popular tool primarily because of their safety and convenience. And luxpower inverter has equipped with a CT current clamp for 3 reasons.
1. Power calculation
1) In an on-grid system, a CT clamp connected with the grid, when the electric current flowed through a wire, the CT clamp sensors sense the magnetic fluctuations and transmit the AC to the luxpower monitoring system at the same time so that the Intelligent Monitoring System can calculate the load power and load electricity consumption according to the feedback data. Otherwise, when the PV panels produce excessive energy and feed into the grid, the flowing power being captured by the fluke clamp meter sensors is still calculated.
2) In the off-grid system, a CT clamp is connected with the generator, when the motor is working, the current flowing through the fluke clamp meter sensor can be monitored and calculated as well as in the on-grid system.
2. Preventing the reverse flowing
Because of the CT clamp having directionality, we define the direction of flow to the inverter to be positive for example, and the opposite direction is the negative direction. When sampled the negative signal, luxpower solar inverters take measures to prevent the current reverse flowing.
3. Self-use Mode
The priority of PV energy management is like this:
Compensate the load consumption > Charge the battery > Feed into the grid.
When we have the data of PV energy, the power of lux battery storage, and the feedback data from CT clamp, we can obtain the load consumption, to achieve self-use and spontaneity.
A CT clamp installation is simple, one to the solar inverter CT & Meter interface and another clamping to the cable. In a completed installed on-grid energy storage system, the connection diagram of the power line of the CT clamp is shown the below figure.
Notice that the system is controlled via meter or CT, the current flow from grid to load is defined as positive while current from the inverter to grid is defined as negative.
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