FZN21-40.5 Indoor Load Break Switch 40.5kV 20kA | High-Voltage Switchgear | IEC Certified

Product Overview

The FZN21-40.5 indoor high-voltage AC vacuum load break switch and the FZRN21-40.5D switch-fuse combination unit are built for 35 kV box-type substations in networks of 40.5 kV at 50 Hz, and either unit can also be used as a standalone switching unit. The load break switch makes and breaks load and overload current at 1250 A and needs no maintenance between services; in the combination unit the series striker-type fuse clears short-circuit current at 20 kA. The vacuum chamber carries current only at the instant of closing and opening, which is what allows the switch to be offered as a maintenance-free unit with a mechanical life of 10000 operations.

Product Display

FZN21-40.5 Indoor High-Voltage Vacuum Load Break Switch - display

FZN21-40.5 Indoor High-Voltage Vacuum Load Break Switch - poster_display

Model Designation

FZN21-40.5 Indoor High-Voltage Vacuum Load Break Switch - model

Model format: FZRN21-40.5D/50-20 (combination unit) and FZN21-40.5 (load break switch, 1250 A)

F: load break switch; Z: vacuum; R: with fuse; N: indoor
21: design sequence number
40.5: rated voltage, kV
D: with earthing switch
50: rated current of the combination unit and of its fuse, A
20: rated short-circuit breaking current, kA
Without the R, FZN21-40.5 describes the load break switch on its own, rated 1250 A

Service Conditions

Ambient temperature: +40 °C upper, -25 °C lower
Altitude: not more than 1000 m
Relative humidity: daily average not more than 95%, monthly average not more than 90%
Seismic intensity: not more than 8 degrees
Site condition: no fire, explosion hazard, chemical corrosion or violent vibration
Pollution level: II

Construction

The three poles stand on a common steel frame: the spring operating mechanism drives the disconnect blade and the earthing blade through the insulating pull rod, the vacuum arc extinction chamber interrupts the circuit, and the operating panel at the front shows the position of each. The disconnect blade gives a visible isolation gap and the earthing blade bonds the de-energised side before maintenance.

The vacuum chamber carries current only at the instant of closing and opening, which is what allows the switch to be offered as a maintenance-free unit with a mechanical life of 10000 operations. The striker of the series fuse acts on the release device, so a blown fuse is reported at the switch instead of being left to protection alone, and the fuse compartment is reached only after the circuit is isolated and earthed.

Technical Data

No.	Item	Unit	Combined unit FZRN21-40.5D	Load break switch FZN21-40.5
1	Rated voltage	kV	40.5	40.5
2	Rated frequency	Hz	50	50
3	Rated short-time withstand current (4 s)	kA	16	16
4	Rated current	A	50	1250
5	Rated breaking current of active load	A	/	1250
6	Rated closed-loop breaking current	A	/	1250
7	Rated peak withstand current	kA	/	40
8	Rated short-circuit breaking current	kA	20	/
9	Rated cable charging current	A	/	21
10	1 min power-frequency withstand voltage (vacuum gap, phase-to-phase and phase-to-earth / across the isolation gap)	kV	95/110	95/110
11	Lightning impulse withstand voltage (same arrangement)	kV	185/215	185/215
12	1 min power-frequency withstand voltage of control and auxiliary circuits	kV	2	2
13	Mechanical life	operations	10000	10000
14	Permissible wear of the vacuum chamber contacts	mm	3	3
15	Manual operating torque	N·m	Not more than 250	Not more than 250
16	Contact gap	mm	17±1	17±1
17	Contact over-travel	mm	5±1	5±1
18	Average closing speed	m/s	0.6±0.2	0.6±0.2
19	Average opening speed	m/s	1.5±0.2	1.5±0.2
20	Opening and closing inconsistency of the three poles	ms	≤2	≤2
21	Closing bounce time of the contacts	ms	≤3	≤3
22	Clearance between live parts and to earth	mm	≥300	≥300
23	Main circuit resistance (excluding the fuse)	μΩ	Not more than 150	Not more than 150

Selection note: 40.5 kV is the rated voltage of the switchgear, and the unit is offered for the 35 kV side of box-type substations. The 16 kA figure is the 4 s short-time withstand current common to both units, while 20 kA is the rated short-circuit breaking current of the combination unit and 40 kA the rated peak withstand current of the load break switch. Non-standard current or fuse combinations are subject to agreement between manufacturer and purchaser. Final parameters are subject to nameplate data and approved specifications.

Standards

The source page does not quote a standard number for this switch. The usual references for indoor high-voltage load break switches are IEC 62271-102 / IEC 60265-1 and GB/T 3804; confirm the applicable edition with the factory when ordering.

Technical note: final parameters are subject to nameplate data and approved specifications.

Installation & Dimensions

Installation Diagram

FZN21-40.5 Indoor High-Voltage Vacuum Load Break Switch - installation

The unit is bolted to the cubicle frame through six 17 by 22 mm slots. Before energisation, check the closed, open and earthed positions and the interlocks on all three poles, fit the specified striker-type fuse with its striker engaging the release device, and measure the main circuit resistance and the clearances.

View / dimension	Value (mm)
Front view overall width	1060 (1015 between outer frames)
Pole spacing	410 ± 2, marked twice
Front view vertical steps	99 / 285 / 400 / 450
Mounting slots	6 × 17 × 22
Side view over top	1065
Side view overall height	1610 (680 at base)
Terminals	lower 4 × 12.5 holes, upper 2 × 12.5 holes

Safety notice: installation, operation and maintenance must be performed by qualified professionals. Before maintenance, open the load break switch, close the earthing blade and verify absence of voltage. Do not use the load break switch alone to interrupt short-circuit current; that duty belongs to the fuse of the combination unit, and a blown fuse is replaced only with the same rated type.

FAQs

It is an indoor three-phase vacuum load break switch for networks of 40.5 kV at 50 Hz, built for the 35 kV side of box-type substations. It makes and breaks load and overload current, isolates the circuit through a visible gap on the disconnect blade and earths the de-energised side with the earthing blade. The FZRN21-40.5D combination unit adds a striker-type fuse so the same frame also clears short-circuit current at 20 kA.

Both are correct and describe different things. 40.5 kV is the rated voltage of the switchgear, the highest voltage the equipment is designed to carry, while 35 kV names the system it is built for, namely the 35 kV side of a box-type substation. Switchgear rated 40.5 kV is the standard selection for a 35 kV network because it leaves margin for the operating voltage of that network.

F is the load break switch, Z the vacuum medium, R indicates the fuse is combined, N that the unit is for indoor use, 21 the design sequence number, 40.5 the rated voltage in kV and D the earthing switch. The trailing numbers give 50 A as the rated current of the combination unit and of its fuse, and 20 as the rated short-circuit breaking current in kA. Without the R, FZN21-40.5 describes the switch alone at 1250 A.

Very little. The vacuum chamber carries current only at the instant of closing and opening, so the switch is offered as maintenance-free with a mechanical life of 10000 operations. What remains to be maintained is the mechanism, the interlocks and the insulation, and the chamber itself once contact wear reaches the permissible 3 mm. No oil or gas top-up is needed.

The striker of the series fuse acts on the release device, so a blown fuse is reported at the switch instead of being left to protection alone. The fuse compartment is reached only after the circuit is isolated and earthed, and the fuse is replaced one-for-one with the same rated type.

The unit is rated 95/110 kV at 1 min power frequency (vacuum gap, phase-to-phase and phase-to-earth / across the isolation gap) and 185/215 kV lightning impulse, with 2 kV across the control and auxiliary circuits and a clearance of not less than 300 mm between live parts and to earth.

FZN21-40.5 Indoor High-Voltage Vacuum Load Break Switch