1. The IT system reduces the contact voltage and grid earth leakage current (effectively controls the direct leakage current to the heart), so the risk of personal electric shock is minimized;

As we all know, when the direct leakage of electric equipment to human heart is more than 10uA, it will cause micro electric shock injury to patients. However, RCD, ELCB and other earth leakage protection switches used in general buildings have mA grade action response value (such as 30 MA), which is far from meeting the needs of medical field.

Therefore, internationally, the operation room, ICU, CCU and other important places in the medical field are usually powered by local "neutral ungrounded power supply system" (i.e. "IT system" or "isolated power supply system"). By using single-phase 3kva-10kva medical isolated power supply to supply power for these places, firstly, the leakage current in other power supply circuits can be prevented from channeling into the medical electrical equipment of operating room, ICU and CCU through the grounding wire, which poses a threat to the safety of patients; In addition, once the load connected to the isolated power supply (such as various medical electrical equipment) has an earth leakage fault, it can only produce a small capacitive leakage current because it cannot form a circuit to the ground, which greatly protects patients from the damage of leakage current.

2. When the first insulation fault occurs at the load end of the power grid, it will not cause the power air switch action (trip), The continuity of power supply is ensured;

In medical field, some places require high continuity of power supply, so it is designed to automatically switch two (or even three) power supplies (grounding power supply system) to ensure the continuity of power supply in these special places. However, if there is a relative insulation fault at the load end, the fault current may form a loop to the ground through the neutral point of the power supply, so as to form a larger fault current, which can make the upper air switch or fuse action, and eventually lead to the interruption of power supply. If the IT distribution system is used in these special places, because the neutral point of the power supply is not grounded, when the first point of the load side insulation fault occurs, it can only produce a small capacitive leakage current because it cannot form a circuit to the ground, which may not harm human body, and not lead to the air switch action, so as to ensure the power supply connectivity of the operating room.

3. The leakage current to the ground is reduced, so the fire safety is improved.

How to design and select IT system for new (reconstructed) hospitals:

1. In medical field, there are three applications of all equipment (including its wires) that are in direct contact with patients for the purpose of examination or treatment

• Application group 0: there is no medical electrical equipment using power grid in the medical area.

For example: outpatient room, waiting room, massage room, etc.

• Application group 1: there is medical electrical equipment using power grid in the medical place, and none of these equipment parts are inserted into the patient's body.

For example: inpatient ward, delivery room, X-ray room, etc.

• Application group 2: all medical electrical equipment powered by power grid in the medical field, is used for heart or internal human surgery, real-time monitoring of patients or life support of patients, etc.

For example: anesthesia room, operation room, operation preparation room, operation plaster room, operation recovery room, cardiac catheter insertion room, intensive care unit, cardiac care unit, angiography examination room, premature infant care unit, etc.

Isolated power supply system (IT system) with insulation resistance monitoring must be used in medical places of application group 2. The ground system, i.e., TN-S system, with leakage current protection can be used in medical places of application group 0 and 1.

2. The electrical equipment suggested connecting to IT grid:

a) Ventilator   b) Constant temperature incubator
c) Dialysis equipment   d) Anesthesia equipment
e) Patient monitoring equipment   f) High frequency surgical equipment
g) Infusion pump   h) Syringe pump
i) Cardiopulmonary machine   j) Cardiac force recorder
k) Pulse compression machine   l) Cardiac rhythm electronic pulse regulator, etc.

3. Basic configuration of IT power supply system in operating room / ICU ward / CCU Ward:

1. Medical isolation power supply
2. Insulation monitor
3. Transformer load and temperature monitoring equipment
4. External alarm display device