Siemens SGIM-3258C

49
Type 3EF Surge Limiters
The type 3EF Surge Limiter is used with vacuum circuit breakers
and contactors to prevent the development of excessive over-
voltages due to multiple reignitions or virtual current chopping.
This is primarily of concern during the starting of motors and the
switching of reactive loads. Surge limiters are recommended in
the applications shown in Table 7. If surge limiters are provided,
and an overvoltage does occur, the magnitude of the voltages will
be limited to the values indicated in Table 8. Recommended
service voltages for each limiter are also shown in this table.
Surge limiters are intended to be used in cable network systems
to protect motors, transformers, and reactors from the effects
of voltage surges associated with vacuum breaker operations.
If lightning or switching surges may be present, the equip-
ment must be properly protected by means of surge arrestors.
The surge limiters must be disconnected from the equipment
before any high potential testing is performed. The one-minute
test period for the application of these test voltages to
switchgear may damage the surge limiters.
Table 7. Type 3EF Surge Limiter Application Recommendations
1
Surge limiter not necessary if surge capacitors or surge
arrestors are located at transformer terminals.
2
Surge limiter not necessary if surge capacitors or surge
arrestors are located at machine terminals.
Table 8. Type 3EF Surge Limiter Data
Rated Voltage kV 3.6 6 7.5 11 15
MCOV of ZnO element kV 2.6 3.9 5.2 9.1 10.4
Series Gap kV 8 10 15 25 31
Sparkover Voltage
1.2 x 50 wave
0.5kA Switching Surge kV 8 10 15 25 31
Discharge Voltage
8 x 20 wave
1.5kA Switching Surge kV 8.3 12.4 16.5 28.9 33.0
Discharge Voltage
8 x 20 wave
Grounded Wye kV 2.4 6.9 8.32 12.0 —
System Applications 4.16 7.2 12.47
13.2
13.8
Delta System kV 2.4 4.16 4.8 6.9 12.0
Applications 4.8 6.9 7.2 12.47
8.3 13.2
13.8
High Resistance kV 2.4 4.16 6.9 6.9 12.0
Grounded Wye System 7.2 12.47
Applications 8.32 13.2
13.8
Protected (Load) Equipment Surge Limiter Recommended
Liquid transformers No
Dry type transformers, Standard BIL Yes
1
Dry type transformers No
5kV with 60kV BIL
Dry type transformers
7kV or 15kV with 95kV BIL No
Motors Locked Rotor Current < 600A Yes
2
Motors Locked Rotor Current > 600A No
Reactors Yes
Capacitors No
Accessories
Courtesy of NationalSwitchgear.com