PRNT American-Type Fuse | Oil-immersed Compact Substation Dual-Sensitive Fuse Link 3-100A Overload Protection Accessory

1. The PRNT oil-immersed high-voltage fuse for transformer overload protection is suitable for AC 50Hz indoor power systems with a rated voltage of 15.5kV and a rated current of 140A. It must be used in series with an oil-immersed transformer short-circuit protection backup fuse to provide full-range protection for power transformers. In the full-range protection scheme, the PRNT is used only to protect against secondary side short-circuit faults and small-range fault currents of the transformer.
2. The current-limiting fuse link is a main accessory for the overcurrent protection device of oil-immersed compact substations in distribution systems. It is used to isolate fault currents to protect distribution equipment or to isolate faulty equipment to protect the power system. It can be used for single-phase transformers up to 500kVA, self-protected transformers, or other distribution equipment. It can also be used for three-phase transformers up to 1500kVA.
3. The dual-sensitive fuse link is a main accessory for overcurrent protection of oil-immersed compact substations in distribution systems. It is used in plug-in fuses and used in conjunction with backup protection fuses (i.e., ELSP) to form a "dual-fuse protection" scheme. The dual-sensitive fuse link protects against low-voltage side faults or overloads of transformers from both current and temperature aspects, preventing long-term temperature rise of the transformer due to overload or ambient temperature. The dual-sensitive fuse link is installed inside a plug-in fuse, making replacement convenient, installation simple, and operation reliable. It is therefore widely used for high-voltage side protection of American-type compact substations. As a high-quality PRNT American-type fuse, it is the ideal choice for oil-immersed transformer overload protection.

The fuse has a plug-in rod structure. It consists of a fuse link, a base, and a handle. One end of the fuse link cap is bell-shaped, and the other end is funnel-shaped. The fuse link is inserted into the screw tube inside the handle. The bell-shaped cap end makes reliable contact with the grip part of the handle through threads. The funnel-shaped cap makes good contact with the screw tube by flattening the upper end of the cap and securing it with an end bolt. The handle is inserted into the base, and the handle latch is turned to lock the fuse.

Rated Voltage (kV)	Voltage (kV)	Fuse Rated Current (A)
Fuse Link Rated Current (A): 6.3, 10, 16, 25, 40, 50, 63, 100, 140		Application Environment: In transformer oil
Rated Maximum Breaking Current (kA): 2.5

1. Open the latch on the handle and pull the handle out of the base.
2. Use a wrench to loosen the screw tube and end bolt in the handle.
3. Loosen the screw tube and end bolt.
4. Insert the fuse link into the screw tube.
5. The bell-shaped cap of the fuse link must be installed between the screw tube and the grip.
6. Use a wrench to secure the grip with a torque of approximately 5.6-7.9 N·m.
7. Flatten the funnel-shaped cap of the fuse link.
8. Use one wrench to hold the bolt at the end of the screw tube and another wrench to tighten the end bolt with a torque of approximately 5.6-7.9 N·m.
9. Insert the handle into the base and turn the handle latch to lock the fuse.

1. When inserting the handle into the base, push it firmly into place, press down and rotate the latch so that when the handle is in the locked position, the stainless steel washer is at the shoulder of the fuse tube to ensure the compact substation is fully sealed and moisture-proof.
2. When the fuse is installed in the oil tank, the oil level in the tank should be within the range shown in Figure 3.
3. After the fuse operates and needs to be replaced, open the latch on the handle, rotate the handle 90deg to break the adhesion between the sealing gasket and the outer tube, and pull out the handle.
4. After the fuse link operates, it must be replaced with a new fuse link of the same model and specifications. Do not substitute with other devices.
5. For three-phase installed fuses, unless it is certain that only one of them has carried the fault current, even if only one fuse operates, the other two should also be replaced.
6. The operation of the fuse can cause deterioration, contamination, and carbonization of the oil.

American-Type Compact Substation Capacity (kVA)	Corresponding Backup Fuse Rated Current (A)	Current-Limiting Protection Fuse (Dual-Sensitive Fuse Link) (A)	Low-Voltage Outgoing Conductor Rod (Low-Voltage Terminal) (A)
50kVA	31.5	6.3	400
80kVA	31.5	10	400
100kVA	40	10	400
160kVA	50	16	400
200kVA	63	20	400
250kVA	80	25	630
315kVA	100	25	630
400kVA	100	40	630
500kVA	125	50	800
630kVA	150	63	1000
800kVA	175	80	1600
1000kVA	200	100	1600