FKN12-12 · FKRN12-12

Indoor air-blast (puffer) load break switch

Indoor 12 kV load break switch with compressed-air (puffer) arc quenching, switching load, closed-loop, transformer magnetising and charging currents. FKRN12-12 is a switch-fuse combination capable of interrupting any current up to the short-circuit current.

Key parameters

Rated voltage: 12 kV
Rated current: 630 A (FKN12-12); 100 A (FKRN12-12)
Rated short-time withstand current: 20 kA (4 s)
Rated short-circuit breaking current (FKRN12-12): 31.5 kA

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General information

The FKN12-12 is an indoor high-voltage puffer-type (compressed-air arc-quenching) load break switch: a three-phase switching device rated for 12 kV and 50 Hz. It is intended for making and breaking load currents, closed-loop currents, magnetising currents of unloaded transformers and charging currents, as well as for making onto a short-circuit current. The load break switch, fitted with an earthing switch, withstands short-circuit current.

The FKRN12-12 is an indoor load break switch–fuse combination that combines the FKN12-12 load break switch with SKLAJ-12 (XRNTC1-10) current-limiting high-voltage fuses. It reliably breaks any current up to the short-circuit current: the load break switch breaks operating currents, the fuse breaks the short-circuit current, and any current between the operating current and the full short-circuit current is broken jointly — the fuse, via its striker, trips the load break switch.

Type designation

FKN12-12D/T630-20

F	Load break switch
K	Arc-quenching medium — air
N	Indoor
12	Design serial number
12	Rated voltage, kV
D	With earthing switch
T	Spring operating mechanism
630	Rated current, A
20	Rated short-time withstand current, kA

FKRN12-12D/T125-31.5

F	Load break switch
K	Arc-quenching medium — air
R	With fuse protection
N	Indoor
12	Design serial number
12	Rated voltage, kV
D	With earthing switch
T	Spring operating mechanism
125	Rated current, A
31.5	Rated short-time withstand current, kA

Note: the spring operating mechanism is available in two versions — manually operated and electrically (motor) operated.

Service conditions

Air temperature: −25 °C … +40 °C.
Altitude: not more than 1000 m.
Relative humidity: daily average ≤ 95 %, monthly average ≤ 90 %.
Seismic intensity: not more than 8 degrees.
Installation site: free from fire and explosion hazards, chemical corrosion and severe vibration.
Pollution level: II.

Main technical parameters

Parameter	Unit	FKN12-12	FKRN12-12
Rated voltage	kV	12
Rated frequency	Hz	50
Rated current	A	630	100
Lightning impulse withstand voltage	kV	to earth and phase-to-phase — 75; across the isolating distance — 85
Power-frequency withstand voltage (1 min)	kV	to earth and phase-to-phase — 42; across the isolating distance — 48
Rated short-time withstand current	kA	20 (4 s)
Rated peak withstand current	kA	50
Rated making current (peak)	kA	50	50
Rated short-circuit breaking current (prospective)	kA		31.5
Maximum Joule integral I²t when breaking the critical current	A²·s	according to fuse characteristic
Minimum breaking current	kA	according to fuse characteristic
Rated transfer current	kA		1.5
Maximum breaking current (reference value)	kA	1.8
Breaking capacity for unloaded transformer	kVA	1250
Rated cable-charging breaking current	A	10
Number of breaks at rated active load current	times	> 100
Time from striker operation to load break switch opening	s		> 0.06
Earthing switch short-time withstand current	kA	20 (2 s)
Earthing switch short-time withstand current (peak)	kA	50
Motor operating mechanism supply voltage	V	AC/DC 110, 220

Overall and mounting dimensions (mm)

Note: dimension L or L1 in the drawing may be specified by the customer; standard L = 174 mm.

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