1、What’s the IT

IT is Non-ground neutral power distribution system, IT undertake the first subsystem of stable power, and is different from the traditional TT, TN power supply and distribution system. Traditional power grid based on the reference potential, the phase line current can pass and not insulated channels, a circuit to the earth, this is the essence of electric shock. And IT the power supply after isolation transformer isolation, original power grids of the earth is no longer a reference potential, no one output line IT can be with the earth constitute a loop, this ensures the safety of power supply. Specific 2 places to go to the hospital, patient and a variety of medical electrical equipment connected, traditional TN -s leakage flows through the ground wire in the power supply system into the operating room, ICU, CCU medical electrical equipment, make patient to electrocution; And IT the power of the earth is no longer a reference potential, up to the patient leakage to the earth structure of circuit, so will not result in electric shock accidents.

 2、How do IT solve leakage

Power supply principle of IT is use isolation transformer turn TN the power supply to the ground of IT. IT systems of the power end not grounding or via high impedance, the exposed conductive part of electrical devices, being alone or centrally by protecting line (PE) even to the earth. In practice, IT systems are and TN or TT system through the isolation transformer isolation. Under normal circumstances, the system exists only in tiny leakage current to ground capacitance. Shown in figure 1 for the first time the IT system earth-fault diagram, when the system is first single-phase earth fault, fault current for the two non fault relatively capacitive current phasor and Id, due to the current value is very small, not cause personal electric shock or other accident, also won't cut off the power supply, ensure the continuity of the system power supply. But if not timely troubleshooting, when another phase ground fault occurs, the second is equivalent to form the interphase short circuit, over current protection device, caused by power supply interruption, for the main power supply room is not allowed.